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The role of submersed angiosperms and charophytes for aquatic fauna communities by Joakim Hansen Plants & Ecology Plant Ecology 2007/4 Department of Botany Stockholm University

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Page 1: Joakim Hansen - s u/PlantsEcology_2007_4.pdf · Joakim Hansen Plants & Ecology ... preventing erosion (reviews in Hemminga & Duarte 2000, ... Schubert & Blindow 2003,

The role of submersed angiosperms and charophytes for

aquatic fauna communities by

Joakim Hansen

Plants & Ecology Plant Ecology 2007/4 Department of Botany Stockholm University

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The role of submersed angiosperms and charophytes for aquatic fauna communities

by

Joakim Hansen

Supervisors: Lena Kautsky and Sofia Wikström

Plants & EcologyPlants & EcologyPlants & EcologyPlants & Ecology Plant Ecology 2007/42007/42007/42007/4 Department of Botany Stockholm University

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Plants & Ecology Plant Ecology Department of Botany Stockholm University S-106 91 Stockholm Sweden © Plant Ecology ISSN 1651-9248 Printed by Solna Printcenter Cover: The gastropod Bithynia tentaculata crawling on a submersed macrophyte covered by periphyton. Photo by Inge Lennmark©, published with permission.

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Summary

In order to predict how environmental changes alter ecosystems structure and function it is important

to understand interactions between units in the food web. The aim of this paper was to review the

role of submersed vegetation for aquatic fauna communities, and discuss if vegetation changes in

eutrophied shallow soft-bottom bays of the Baltic Sea have a potential to change the fauna

community. Aquatic angiosperms and charophytes affect the aquatic fauna communities in several

ways and the effect can differ between macrophyte taxa. The macrophyte structure alters food web

interactions and thereby influences the fauna communities. The plant structures also affect the

production of periphyton, which in turn influences the fauna by being an important food resource.

Live angiosperms and charophytes, as well as macrophyte detritus, are also consumed by several

fauna species. The production of allelochemicals by macrophytes can impact on the plant associated

fauna both directly and indirectly by being toxic to the animals or affecting the periphyton

composition. With eutrophication of shallow coastal bays in the Baltic Sea the aquatic fauna

community in these bays can be altered as a response to vegetation changes induced by the nutrient

enrichment.

Sammanfattning

För att förutsäga hur miljöförändringar påverkar ekosystems struktur och funktion är det viktigt att

förstå interaktioner mellan olika komponenter i födoväven. Målet med den här studien var att gå

igenom litteratur om vattenväxters roll för de vattenlevande djuren samt att diskutera om

vegetationsförändringar i övergödda grunda mjukbottenvikar i Östersjön har en potential att förändra

djursammansättningen. Vattenväxter, så som angiospermer och kransalger, påverkar akvatiska

djursamhällen på flera sätt. Denna inverkan på djursamhällena kan skilja mellan olika växtarter.

Växterna kan påverka djuren genom att deras struktur förändrar interaktioner i födoväven. Vidare

kan strukturen inverka på produktionen av påväxtorganismer, vilka i sin tur påverkar djuren genom

att de är en viktig födoresurs. Levande angiospermer och kransalger, liksom nedbrutna växtdelar,

konsumeras även av flertalet djur. Växterna producerar dessutom substanser som är giftiga för andra

organismer, vilket kan påverka djuren både direkt och indirekt genom att vara giftiga för djuren eller

genom att sammansättningen av påväxtalger förändras. Med övergödning av grunda vikar i Östersjön

kan förändringar i djursammansättningen i dessa vikar förväntas genom att växtsamhället förändras

som en respons på förhöjda närsaltshalter.

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Content

Summary......................................................................................................................................... 1

Sammanfattning............................................................................................................................. 3

Introduction .................................................................................................................................... 5

Animals associated with macrophyte vegetation........................................................................ 7

Aquatic macrophytes as a habitat for invertebrate fauna and fish........................................... 8

Function of macrophyte structure ................................................................................................ 8

Structural complexity............................................................................................................... 8

Direct function of vegetation structure.................................................................................. 10

Indirect function of vegetation structure................................................................................ 11

Macrophytes as a food resource................................................................................................. 12

Angiosperms as a food resource............................................................................................ 12

Charophytes as a food resource............................................................................................ 14

Feeding preference for certain macrophytes......................................................................... 14

Macrophyte detritus as a food resource................................................................................ 16

Macrophytes as substrate for periphyton ................................................................................... 16

Effects of allelochemicals produced by macrophytes................................................................ 18

Direct effects of allelochemicals............................................................................................ 18

Angiosperms producing allelochemicals............................................................................... 18

Charophytes producing allelochemicals................................................................................ 19

Indirect effects of allelochemicals......................................................................................... 19

Effects of macrophyte diversity and habitat size ....................................................................... 20

Effects of macrophyte diversity.............................................................................................. 20

Effects of habitat size............................................................................................................. 22

Potential effects of vegetation changes on the fauna in soft-bottom bays of the Baltic Sea.. 23

References..................................................................................................................................... 26

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Introduction

The role of submersed rooted macrophytes in aquatic systems has been documented for long. The

early literature stressed the importance of the structure the plants provide for the fauna communities

comparing vegetated and non-vegetated soft-bottom areas (e.g. Gilinsky 1984, Orth et al. 1984,

Diehl 1988, Engel 1988, Heck & Weinstein 1989). The role of rooted vascular macrophytes as a

direct food source for consumers was considered less important at first. But this view has changed,

and the direct consumption of vascular macrophytes is now considered as important as in terrestrial

ecosystems (Lodge 1991, Newman 1991, Lodge et al. 1998, Nakaoka 2005, Heck & Valentine

2006), although (non-vascular) periphytic and planktonic algae still are considered the most

important energy source for the aquatic fauna (Hoyer et al. 1998).

The vegetated soft-bottoms provide humans with a set of ecosystem goods and services. One of the

major goods from seagrass beds are fish and shellfish species (e.g. Hemminga & Duarte 2000,

Harborne et al. 2006). Furthermore, macrophytes on soft-bottoms maintain biodiversity of both

fauna and flora and keep the biological production at a high rate (reviews in Hemminga & Duarte

2000, Scheffer 2004). Aquatic macrophytes also play a significant role in global nutrient cycling

(Costanza et al. 1997). They trap nutrients and bind sediments, thereby improving water quality and

preventing erosion (reviews in Hemminga & Duarte 2000, Scheffer 2004). Additionally aquatic

macrophytes are an important carbon sink (Smith 1981).

Ecosystems housing submersed angiosperm and charophytes have, like many other ecosystems

around the globe, been subjected to major environmental changes during the last decades. One of the

most important forces for changes in the aquatic ecosystems is eutrophication (e.g. Schramm &

Nienhuis 1996, Scheffer 2004). With eutrophication there has been a general decline of slow-

growing and perennial species and an increase of fast-growing, mainly annual benthic and planktonic

algal species (but also some rooted macrophytes). The latter species have higher uptake rates of

nutrients available directly in the water and are in some cases also more tolerant to low light

conditions (e.g. Sand-Jensen & Borum 1991, Duarte 1995). In temperate regions a number of lakes

have, after dramatic increases in nutrient loading, shifted from a clear water state with abundant

macrophyte vegetation to a turbid phytoplankton state with almost no macrophyte cover (review in

Scheffer 2004). In other lakes and in the Baltic Sea charophytes have declined and been replaced by

angiosperms more tolerant to low light conditions, e.g. Ceratophyllum demersum, Myriophyllum

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spicatum and Potamogeton pectinatus (Blindow 1992, Blindow 2000, Schubert & Blindow 2003,

Munsterhjelm 2005). Marine seagrasses around the globe have declined because of a similar

eutrophication process with e.g. increased phytoplankton production, epiphytic algae load and

floating mats of fast growing algae, shading the angiosperms (reviews in Fletcher 1996, Hemminga

& Duarte 2000). Increased dredging and boat traffic are other factors negatively affecting rooted

macrophytes by mechanical impact, altered hydrological conditions and increased turbidity

(Hemminga & Duarte 2000, Eriksson et al. 2004). Another anthropogenic impact responsible for

environmental changes in both terrestrial and aquatic environments is the introduction of non-native

species. The spread of introduced aquatic macrophytes can lead to habitat changes and altering of

both ecosystem structures and functions (e.g. Lyons 1989, Cheruvelil et al. 2002, Occhipinti-

Ambrogi & Savini 2003, Schaffelke et al. 2006, Wallentinus & Nyberg 2007). However, the

extension of the introduced macrophytes in the Baltic Sea is limited and no species have been

recorded to outcompete native macrophytes. With a global warming of the planet it is likely that we

can expect further changes in the macrophyte communities on soft-bottoms, as abiotic conditions are

altered at a high rate, stressing the ecosystems.

In order to predict how these environmental changes in the aquatic vegetation can alter the

ecosystems function, and thereby the goods and services provided to humans, it is important to

understand the role of the submersed vegetation in the aquatic ecosystems. The main focus of this

review is concerned with the functions and effects of submersed angiosperm and charophyte

characteristics on the aquatic fauna communities. Furthermore, recorded and potential effects of

vegetation changes on the fauna communities due to eutrophication are discussed. Consequently, the

present paper has largely a bottom-up perspective of the ecosystem. This focus is not because the

top-down perspective is less important; however it is left outside the scope of this review. As the

paper is a literature pre-study for further research in shallow vegetated soft-bottom areas of the Baltic

Sea a special emphasis has been made to cover literature either from the brackish Baltic Sea, or

dealing with species occurring in shallow coastal bays of the Baltic Sea.

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Animals associated with macrophyte vegetation

The aquatic animals living in association with macrophytes on soft-bottoms are a diverse group of

species belonging to a variety of taxa, e.g. hydrozoans, annelids, crustaceans, insects, molluscs and

fishes. These animals have evolved many different ecological traits, something which may influence

what effect the plants have on the animals. The fauna can be divided into three broad categories

according to there occurrence in spatially separated habitats; 1) infaunal species live in the

sediments; 2) epifaunal species inhabit the stems and leafs of macrophytes, as well as the sediment

surface beneath the vegetation; 3) epibenthic species are highly motile animals which moves freely

under and over the vegetation (e.g. fishes). The two first groups are further divided according to

motility as sessile or motile species. The more motile species (e.g. fishes) are divided into groups

depending on their residence status in the vegetation; some are permanent residents, others

temporary residents, regular visitors or occasional visitors (Hemminga & Duarte 2000). The fauna

species can also be categorised into groups depending on their trophic levels (herbivores, carnivores

or detritivores) and according to feeding mode (e.g. grazing, mining, or collecting). All these

different groups may be differently affected by changes in the vegetation. For instance, specialised

grazers or leaf miners may be more affected by a shift in plant species composition than a detritus

feeding infauna species. In a similar way fish species that are permanent residents in a seagrass

meadow may be more affected by its disappearance than will an occasional resident. In this review I

will, for simplicity, present a much more generalised view of the functions and effects of aquatic

macrophytes on the fauna, without detailed separation of the effects and functions of macrophytes on

different faunal groups.

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Aquatic macrophytes as a habitat for invertebrate fauna and fish

Function of macrophyte structure

In aquatic environments comparisons between non-vegetated and vegetated bottoms, as well as

comparisons within gradients of vegetation densities have revealed the importance of habitat

structure for the inhabiting fauna communities. Generally, fauna densities and species richness are

considerably higher where plant structures are provided, and additionally increase with increasing

structure (Fig. 1; for reviews see Orth et al. 1984, Diehl & Kornijóv 1998, Hemminga & Duarte

2000). Also other biotic structures (shells, sponges, bryozoans and corals) as well as abiotic

structures (rock formations and artificial reefs) increase the fauna richness and abundance (Stoner &

Titgen 2003, Gratwicke & Speight 2005, Arias-Gonzalez et al. 2006, Wilhelmsson et al. 2006).

However, the opposite has also been found, especially when a single taxon or trophic level has been

studied, a higher trophic level has been absent, abiotic conditions altered (increased turbidity), or a

non-native species has been introduced (Brown et al. 1988, Cheruvelil et al. 2001, Snickars et al.

2004, Kornijów et al. 2005, Rennie & Jackson 2005). Furthermore, different plant species may affect

the fauna community differently because of there differences in physical structure, i.e. shoot

branching, leaf shape and size etc.

Structural complexity

To describe and compare differences in physical structures of habitats the terms habitat complexity,

spatial complexity or structural complexity is often used. However, what is meant by habitat, spatial

or structural complexity may vary from study to study and an exact definition is seldom specified.

Complexity has been measured as density or biomass of structures, or colonisable area of structures

(Boström & Bonsdorff 2000, Snickars et al. 2004, Rennie & Jackson 2005). However, according to

other studies these measures only examine the amount of available habitat, rather than complexity

per se (Attrill et al. 2000, McAbendroth et al. 2005). In landscape ecology complexity is typically

used as a measure of patch size and shape based on the ratio of patch perimeter to area (Robbins &

Bell 1994). Looking at a smaller scale, Dibble et al. (1996) defined spatial complexity of macrophyte

habitats as; Ihv = fh/lh + fv/lh. Where fh and fv are the frequencies of gaps among leaves and stems

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along a horizontal (h) and a vertical (v) axis respectively, and lh and lv are the mean length of gaps

among leafs and stems along the vertical and horizontal axes. Fractal analyses are also used to

quantify complexity (Jeffries 1993, Kostylev et al. 2005). McAbenroth et al. (2005) used the fractal

dimensions of macrophyte area and perimeter at two different scales to measure macrophyte

structural complexity. Also combinations of different measures of architectural features have been

used for calculating complexity of macrophytes, e.g. (epiphyte biomass * fractal dimension *

leaves/shoot) * shoot density (Attrill et al. 2000).

Figure 1. Documented relationships between macrophyte vegetation and associated fauna. (A) Ratio of species number and (B) ratio of individual abundance in seagrass vegetated versus non-vegetated areas (±SD). Positive values show greater abundance in vegetated areas (1=one times greater), negative values show greater abundance in non-vegetated area (-1=one times greater), 0 means no difference. Datapoints are mean values from several separate studies compiled by in Hemminga and Duarte 2000 (A: fish 15 studies, crustaceans 1 study, canopy epifauna 1 study, benthic macrofauna 5 studies.; B: fish 16 studies, crustaceans 5 studies, canopy epifauna 2 studies, benthic macrofauna 4 studies. (C) Relationship between macrophyte density and wet biomass of benthic and epiphytic macroinvertebrates in Lake Pääjärvi, Finland (95% confidence intervals). From Kornijów & Kairesalo 1994, cited in Diehl & Kornijów 1998.

The measure of structural complexity will depend on the observation scale (Wiens 1989, Robbins &

Bell 1994, Attrill et al. 2000, Dibble et al. 2006). Dibble et al. (2006) found the spatial complexity to

change differently across scales (1 - 50 cm) for different macrophyte species. In the choice of scale it

must be considered what type of species is subjected to the structure. For macrofauna species size of

the macrophyte meadow, density of shoots, leaves per shoots, leaf structure and area may be

important characteristics for complexity. For meiofauna it may instead be the microscopic surface of

the stems and leaves that are important attributes of complexity (Attrill et al. 2000, Dibble et al.

2006). However, our choice of scale is subjective and may not be accurate (Wiens 1989). With a

macroinvertebrate perspective branched algae have been suggested to be more structurally complex

than unbranched algae (Parker et al. 2001). Among rooted freshwater macrophytes highly branched

FishCrustaceans

Canopy epifaunaBenthic macrofauna

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thin-leafed species are considered more complex than sparsely branched broad-leafed species

(Humphries 1996, Warfe & Barmuta 2006, Xie et al. 2006).

The density of macroinvertebrates has been shown to increase with increasing structural complexity

(McAbendroth et al. 2005) and dissected plant species like Myriophyllum spp. to be inhabited by

high densities of fauna (Scheffer et al. 1984, Humphries 1996, McAbendroth et al. 2005, Warfe &

Barmuta 2006, Xie et al. 2006). Contrary to these results, Atrill et al. (2000) did not find the fauna

abundance and diversity in seagrass meadows to increase with increasing complexity. Instead they

suggested density and diversity of macroinvertebrates to increase with increased surface area as they

found an increase in density and number of macroinvertebrate species with increased seagrass

biomass. However, in studies of artificial structures with different complexity but similar surface

area, diversity and abundance of freshwater macroinvertebrates has been found to increase with

increasing complexity (Jeffries 1993, Taniguchi et al. 2003).

An absolute ranking of macrophyte species according to spatial complexity is difficult as different

measures of complexity may be used and different plants are compared in different studies.

Regarding soft-bottom macrophytes found in the Baltic Sea (e.g. Munsterhjelm 1997) McAbendroth

et al. (2005) found Myriophyllum alterniflorum to be the most complex macrophyte in a comparison

with Chara sp. and 14 other species. Dibble et al. (1996) though, found Myriophyllum spicatum to

have the lowest, and Potamogeton pectinatus to have the highest complexity in their study of 7

macrophyte species.

Direct function of vegetation structure

The explanation for higher production and increased number of fauna species with increasing

complexity or shoot density may be that the availability of microhabitats increase and interactions in

the food webs are altered (Scheffer 2004). The strength of e.g. a predator-prey interaction has been

suggested to decrease as structures are provided for the prey as refuge and hence a co-existence

between the predator and prey is facilitated. In several studies it has been observed that the structure

provided by macrophytes increases the survival rate of macroinvertebrates subjected to fish predators

(Diehl 1988, Mattila 1992, Diehl 1993, Isaksson et al. 1994, Diehl & Kornijóv 1998). The predation

success of planktivorous fishes like sticklebacks (Gasterosteus aculeatus) roach (Rutilus rutilus) and

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rudd (Scardinius erythrophtalmus) also decreases in dense macrophyte habitats (Winfield 1986,

Schriver et al. 1995, however see Kornijów et al. 2005). Hence, the structural refuges provided by

macrophytes also alter the zooplankton-phytoplankton interactions as the consumption rate of

phytoplankton increases with a high zooplankton survival (Schriver et al. 1995, Scheffer 2004).

However, this trophic cascade is more complex as e.g. juvenile fish also escape predation in the

vegetation and fish predation on zooplankton can be high in vegetated areas (Winfield 1986,

Schriver et al. 1995, Scheffer 2004). Furthermore, macrophytes can serve as a substrate for fish eggs

and larvae and thereby increase the reproduction success of several fish species, e.g. pike (Esox

lucius) and perch (Perca fluviatilis) (Karås 1999). Similar to the altering of interactions between

different trophic levels, complex habitats may provide conditions for modifications in resource

partitioning and niche breadth of species on the same trophic level. Different fauna species may have

certain preference for different macrophytes. For example Chick & McIvor (1997) observed three

small fish species to prefer structurally different macrophyte habitats in the presence of a predator.

Differences in fauna densities between macrophytes can also be caused by differences in the plants

life-cycles and hence differences in habitat permanence. Hargeby (1990) found the abundance of

macroinvertebrates to differ between the structurally similar Chara tomentosa (perennial) and

Nitellopsis obtusa (annual) in the field, although there was no habitat preference between the two

charophytes in a laboratory experiment. He suggested that in the seasonally changing habitat of N.

obtusa density-dependent animal interactions are of little importance for the species composition and

that species capable of fast colonisation are favoured. Hence, niche and life-cycles of both

macrophytes and fauna influence the specific patterns found in habitat preference on a species level.

Indirect function of vegetation structure

So far, I have mainly covered the direct functions of the structure provided by macrophytes on soft-

bottoms. A more large-scale, indirect function of macrophytes related to their structure is that they

can prevent eutrophied shallow lakes to shift to a turbid phytoplankton states as mentioned in the

introduction. In numerous lakes that have shifted from a clear vegetated state to a non-vegetated

turbid state the fauna diversity and whole lake bio-production have decreased (e.g. Hargeby et al.

1994, Scheffer 2004). The stabilisation of lakes in a vegetated state is conducted through a series of

feed-back mechanisms (reviews in van Donk & van de Bund 2002, Scheffer 2004). Rooted

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macrophyte vegetation stabilises sediments and reduce currents, and thereby prevents diffusion of

nutrients and organic matter to the water phase. This restricts the formation of large phytoplankton

blooms and promotes water clarity. By providing structural refuges for zooplankton from

planktivorous fish the macrophytes can further prevent phytoplankton growth as zooplankton

consumes phytoplankton. Apart from their structural function macrophytes also compete with

phytoplankton for nutrients and several macrophytes can produce chemical compounds that prevent

phytoplankton growth. Shifts between vegetated and non-vegetated states have been suggested to

occur also in eutrophied shallow bays in the Baltic Sea (Dahlgren & Kautsky 2004), and the

vegetation may play a similar role in these systems.

Macrophytes as a food resource

Angiosperms as a food resource

According to recent studies the direct grazing of vascular macrophytes (e.g. angiosperms) by

herbivores in marine and freshwaters is as extensive as that in terrestrial ecosystems (Fig. 2 A; Lodge

1991, Newman 1991, Lodge et al. 1998, Nakaoka 2005, Heck & Valentine 2006). Vascular

macrophyte biomass is to the largest extent consumed by fish, waterfowl and mammals in both

freshwater and marine ecosystems, with the addition of crayfish in freshwaters and sea urchins in

marine environments (Fig. 2 B; Lodge et al. 1998, Heck & Valentine 2006). Other invertebrates only

consume a smaller amount of vascular macrophyte biomass. However, the relative importance in

consumption rate of different faunal groups depends on the latitude as e.g. large mammal grazers,

such as dugongs (Dugong dugon) and manatees (Trichechidae), are absent at higher latitudes. In

temperate regions some fish species, like rudd and grass carp (Ctenopharyngodon idella), can graze

heavily on vascular macrophytes (Hansson et al. 1987, van Donk & Otte 1996, van Donk 1998,

Pípalová 2002, Nurminen et al. 2003). Other fish species, like roach, may occasionally graze on

macrophytes although their primary source of food is zooplankton (Körner & Dugdale 2003). Birds

can consume high quantities of submersed vascular macrophytes (Verhoeven 1980, van Donk & Otte

1996, Idestam-Almquist 1998, Mitchell & Perrow 1998, Søndergaard et al. 1998, Nacken & Reise

2000), but the negative effects on macrophytes is usually larger from plant damage rather than direct

grazing (e.g. Mitchell & Perrow 1998, Søndergaard et al. 1998). In temperate regions it is especially

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coots (Fulica atra), ducks (Anas spp./Aythya spp.), swans (Cygnus spp.) and geese (Anser

spp./Branta spp.) that are responsible for the major grazing of macrophytes (Verhoeven 1980, van

Donk & Otte 1996, Idestam-Almquist 1998, Mitchell & Perrow 1998, Søndergaard et al. 1998,

Nacken & Reise 2000, Sandsten 2002). In lakes where crayfish are abundant their grazing effects on

macrophytes can be profound (especially where non-native crayfish species are introduced: Lodge et

al. 1994, Nyström & Strand 1996). Although the reduction of vascular plant biomass by other

invertebrates is considered low in comparison to crayfish, birds and fishes, there are several

examples of substantial herbivory by invertebrates other than crayfish (review in Newman 1991,

Kornijów 1996). Vascular plants are digested directly by gastropods (Pinowska 2002), aquatic

insects (McGaha 1952, Grillas 1988, Newman 1991, Cronin et al. 1999), and crustaceans (Menéndez

& Comín 1990, Thom et al. 1995, Kotta et al. 2004, Boström & Mattila 2005). In the Baltic Sea, the

isopod Idotea baltica has been observed to graze considerably on P. pectinatus (Boström & Mattila

2005). Mining and borrowing of seagrass leaves have been reported for both marine polychaetes

(Guidetti 2000, Gambi et al. 2003) and isopods (Brearley & Walker 1995, van Tussenbroek &

Brearley 1998, Guidetti 2000). Furthermore, specialisation in seed predation has been observed

among tanaids (Zeuxo sp.) in seagrass habitats (Nakaoka 2002), and several insect species have

specialised on host plants in freshwaters (McGaha 1952, Newman 1991, Sheldon & Creed 1995,

Cronin et al. 1999).

Figure 2. (A) Mean and range of percentage reduction of standing crop of vascular and non-vascular plants (excluding phytoplankton) in terrestrial, marine and freshwater habitats. Sample numbers (numbers of separate experiments or comparisons) are in parentheses below the habitat name (vascular, non-vascular). The few negative values are not plotted but are listed here: -2, -20, -38 for terrestrial; -5, -5, -50 for marine; -24, -47 for freshwater. (B) Data points and means (horizontal bars) for the percentage reduction of standing crop of freshwater vascular and non-vascular plants (excluding phytoplankton) by different taxa of herbivores. Large dots are mean values from one study summarising several others. Small dots represent single experiments or comparisons. Modified from Lodge et al. 1998.

A B

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Charophytes as a food resource

Although vascular plants are consumed by most aquatic faunal groups, non-vascular plants are more

important as a food resource for the majority of the invertebrate herbivores (Lodge et al. 1998). Fish

also consume non-vascular plants to a high degree. The grazing of algae can be profound and impact

on the benthic plant communities (Nicotri 1977, Brawley & Fei 1987, Brawley 1992, Jernakoff &

Nielsen 1997, Malm et al. 1999, Duffy & Hay 2000). Studies on faunal grazing on charophytes are

rather few. Direct consumption of charophytes has been reported to occur among birds (Cramp &

Simmons 1977), fish (grass carp: Fowler & Robson 1978, McKnight & Hepp 1995), crayfish

(Nyström & Strand 1996, Cronin et al. 2002) and smaller crustaceans (Kotta et al. 2004). In the

Baltic Sea the isopod I. baltica and the amphipod Gammarus oceanicus have been observed to graze

directly on Chara tomentosa and Chara connivens (Kotta et al. 2004). Furthermore, some aquatic

insect species of the genera Haliplus and Liaphlus (family Haliplidae) are specialised to feed on

charophytes, and the charophyte specialist Haliplus obliquus has been found in the Baltic Sea

(Holmen 1987, Schubert & Blindow 2003).

Feeding preference for certain macrophytes

Preferences for feeding on certain vascular macrophyte species have been reported from a variety of

faunal groups. Rudd has for example been observed to avoid Myriophyllum verticillatum and

Ceratophyllum demersum, while otherwise feeding quite unselectively on macrophytes (Nurminen et

al. 2003). In tropical seagrass meadows the herbivorous fish Calotomus carolinus has been observed

to prefer short-lived r-species over long-lived K-species (Mariani & Alcoverro 1999). Snails (Galba

turricula) consumed more Elodea canadensis than C. demersum in a study by Pinowska (2002). An

aquatic Chrysomelidae insect (Galerucella nymphaeae) studied in North America was observed to

have a quite narrow diet breadth, preferring mainly two genera of aquatic macrophytes (Cronin et al.

1999). In a study of two isopod species, one in the Baltic Sea (I. baltica) and one in the Gulf of

Mexico (Erichsonella attenuata), clear feeding preferences for certain vascular plants were observed,

though the preference and investigated macrophyte species differed between the regions (Boström &

Mattila 2005). Furthermore, two crayfish species in temperate regions (Astacus astacus and

Pacifastacus leniusculus) have been observed to prefer seedlings over established Potamogeton

natans. However, the two crayfish species preferred the non-vascular charophyte Chara vulgaris

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over P. natans and two other vascular plants (Nyström & Strand 1996). Among charophytes Kotta et

al. (2004) observed a preference for C. tomentosa over C. connivens by the isopod I. baltica and the

amphipod G. oceanicus.

The selective feeding of animals has been attributed to the physical, chemical and nutritious

properties of the macrophytes (Bolser et al. 1998, Cronin et al. 2002). For example the crayfish

Procambarus clarkii was observed to prefer delicate over tough structured macrophytes (Cronin et

al. 2002). However, when the plants were offered in identical structures (alginate gel with dried and

powdered plants) the crayfish preferred macrophytes high in nitrogen and protein. Similarly the

feeding behaviour of the tropic fish Calotomus carolinus was correlated with carbon content in the

macrophytes, indicating that the fish preferred leafs low in carbon (Mariani & Alcoverro 1999). Not

only the physical structure and ratio of C:N:P in plant tissue can affect the feeding preference. Plants

may contain grazing deterrent chemicals to avoid damage from fauna (Dhillon et al. 1982, Bolser et

al. 1998, Cronin et al. 2002, Parker et al. 2006). Lodge et al. (1998) suggested a three-step

hierarchical model for the feeding preference among aquatic herbivores (Fig. 3). Plants must have a

structure that makes it feasible for herbivores to take a bite and lack chemical deterrents to be

significantly consumed. Furthermore, plants high in nutrients are preferred over species low in

nutrients. Though, other factors may also contribute to herbivores choice of food, e.g. the plant

structure as protection from predators (Duffy & Hay 1991), the herbivores previous feeding

experience (Moran & Arrontes 1994) and non-native origin of plants (Kotta et al. 2004).

Figure 3. Conceptual model of how diet composition is determined in freshwater herbivores. Modified from Lodge et al. 1998.

Not eaten

Little eaten

Eaten if nothing else is available Highly preferred

No Yes

No Yes

No Yes

Is the plant structurally suitable?

Is the plant chemically suitable?

Is the plant nutritious?

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Macrophyte detritus as a food resource

Fresh macrophyte tissue that is not grazed will eventually end up as decaying detritus on the bottoms

(or will be flushed up on shores by water movements). The role of decomposed macrophytes as a

nutrient source for animals may be considerable. Kornijóv et al. (1995) investigated the feeding on

fresh and decomposed algae (Mougeotia sp.) and a vascular macrophyte (Elodea nuttallii) by three

invertebrate species belonging to the different classes Gastropoda, Isopoda and Insecta. They found

that the digestibility of both vascular and non-vascular macrophyte increased after decomposition

and the consumption by the three invertebrates was higher on decomposed compared to fresh plants.

Accordingly, the grazing rate of I. baltica and G. oceanicus on C. tomentosa and C. connivens was

favoured by high decomposition rates in a study by Kotta et al. (2004). Furthermore, Idotea viridis,

Sphaeroma hookeri (Isopoda) and Gammarus spp. have been shown to consume substantial amounts

of decaying Ruppia cirrhosa (Verhoeven 1980, Menéndez & Comín 1990).

Macrophytes as substrate for periphyton

In aquatic environments most submersed surfaces are covered by periphyton. The periphyton

consists of macroscopic and microscopic algae and invertebrates, as well as bacteria and dead

organic matter. Periphyton is utilised as an energy source by a number of macroinvertebrates

(D'Antonio 1985, Brawley & Fei 1987, Jernakoff & Nielsen 1997, James et al. 2000, Hillebrand

2002). It is often the preferred food over vascular plants and seaweeds for small invertebrates and

some fish species (Pavia et al. 1999, Lepoint et al. 2000, Kamermans et al. 2002, Orav-Kotta &

Kotta 2004). The three main factors suggested to influence this feeding choice are (as mentioned

previously) structure, chemical deterrents and food quality (Duffy & Hay 1991, Lodge et al. 1998).

Although the nutritional value is important for the herbivores’ choice of food, there is generally little

difference in nitrogen content between periphyton and macrophytes (Lodge 1991). Instead the

increased digestibility due to a more delicate structure has been suggested as the main explanation

for the higher consumption of periphyton among macroinvertebrate herbivores. Preference by

aquatic fauna among different taxa of periphyton is likely influenced by factors such as nutrient

value and toxic deterrents (Sommer 1997).

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Variations in periphyton production may influence the distribution of fauna species. As rooted

angiosperms and charophytes provide vertical structures on otherwise structurally simple soft-

bottoms, the production of periphyton can increase in these areas. The production of aquatic

microorganisms has been shown to increase dramatically with the presence of macrophytes (Wetzel

& Søndergaard 1998, Theil-Nielsen & Søndergaard 1999). The macrophytes not only provide a

structure for the periphyton, but can function as a carbon source and a vector for trace elements

transported from the sediments to the leaf surfaces (Jackson et al. 1994, Wetzel & Søndergaard

1998). However, the production of periphyton can decrease with increased density of macrophytes as

a consequence of e.g. light and carbon competition (Jones et al. 2002). Furthermore, the abundance

of periphyton is not uniform and differs between plant parts and with depth (Baker & Orr 1986,

Liboriussen & Jeppesen 2006).

The composition and production of periphyton can also differ between different macrophyte species

(e.g. Snoeijs 1994, Jones et al. 2000, Kuczynska-Kippen et al. 2005, Messyasz & Kuczynska-Kippen

2006), and this may influence the habitat selection of macrofauna for different macrophytes as the

fauna can have preference for certain periphyton (Neckles et al. 1994, Sommer 1997). Few studies

have covered this topic and the research in this field has mainly been concentrated on periphytic

microalgae (e.g. Snoeijs 1994, Jones et al. 2000, Kuczynska-Kippen et al. 2005, Messyasz &

Kuczynska-Kippen 2006). In a comparison of the periphyton community on C. tomentosa and Typha

angustifolia, the first species had in general a higher biomass of periphyton and Chlorophyta

(Kuczynska-Kippen et al. 2005, Messyasz & Kuczynska-Kippen 2006). This difference was

probably caused by differences in the macrophytes macroscopic structure (colonisable area and

shading), the microscopic structure (attachment) and the excretion of different chemical defence

compounds. Research on differences in the bacterioperiphyton between different macrophytes is

scarcer. When Theil-Nielsen & Søndergaard (1999) compared periphytic bacteria between P.

pectinatus and C. demersum no difference was found.

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Effects of allelochemicals produced by macrophytes

Direct effects of allelochemicals

Bioactive chemicals produced by aquatic macrophytes can affect fauna species associated to the

vegetation. A biochemical interaction of any two different species is termed allelochemistry (Gross

1999). Allelochemicals are produced by species to alter interactions between them and other

organisms. In aquatic environments there are documented effects of allelochemicals produced by

macrophytes on both flora and fauna. Macrophytes producing allelochemicals can have negative

effects on macroinvertebrates (e.g. Dhillon et al. 1982, Jacobsen & Pedersen 1983, Lindén &

Lehtiniemi 2005), fish (Parker et al. 2006) and zooplankton (e.g. Cangiano et al. 2002, van Donk &

van de Bund 2002). However, the most studied biochemical interaction is that between different

autotrophic species and is termed allelopathy (Gross 1999). Allelopathic substances produced by

macrophytes have been shown to affect phytoplankton (Jasser 1995, Nakai et al. 1999, Berger &

Schagerl 2003, Mulderij et al. 2003, Mulderij et al. 2005), epiphytic algae (Erhard & Gross 2006,

Hilt 2006) and other rooted macrophytes (Agami & Waisel 1985, Elakovich 1999).

Angiosperms producing allelochemicals

Several aquatic angiosperm taxa that occur in the Baltic Sea (see e.g. Munsterhjelm 1997, Kautsky &

Foberg 2001) have been suggested to produce allelochemical substances due to direct detection of

chemicals and/or due to observation of their inhibitory effect on other organisms; e.g. Ceratophyllum

demersum (Jasser 1995, Körner & Nicklisch 2002, Gross et al. 2003), Elodea spp. (Erhard & Gross

2006, Lürling et al. 2006), Juncus spp. (Della Greca et al. 2002), Myriophyllum spicatum (Dhillon et

al. 1982, Agami & Waisel 1985, Jasser 1995, Nakai et al. 1999, Nakai et al. 2001, Körner &

Nicklisch 2002, Nakai & Hosomi 2002, Lindén & Lehtiniemi 2005), Myriophyllum verticillatum

(Hilt et al. 2006), Najas marina (Agami & Waisel 1985, Gross et al. 2003), Ruppia maritima (Della

Greca et al. 2000, Cangiano et al. 2002), Typha spp. (Aliotta et al. 1990, Della Greca 1990) and

Zostera marina (Harrison & Chan 1980, Harrison & Durance 1985). Potamogeton species, which are

common in the Baltic Sea, generally exhibit no or only very weak allelopathic activity according to

Gross (2003). When Potamogeton pectinatus was examined by Körner & Nicklisch (2002) they did

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not find any allelochemical substances produced by this plant. A similar finding was reported for

Potamogeton crispus (Nakai et al. 1999). However, allelochemical activity has been observed for

Potamogeton lucens (Jasser 1995) and Potamogeton natans (Cangiano et al. 2001, Della Greca et al.

2001, Cangiano et al. 2002).

Charophytes producing allelochemicals

Generally, production of allelochemicals is common among charophytes. In a study by Berger &

Schagerl (2004) 10 out of 13 screened charophyte species inhibited growth of cyanobacteria. Among

the charophytes occurring in the Baltic Sea (see Schubert & Blindow 2003) production of

allelochemicals and/or inhibition of organism growth have been observed for Chara aspera (Berger

& Schagerl 2003, Berger & Schagerl 2004), Chara baltica (Wium-Andersen et al. 1982), Chara

contraria (in a mix with C. globularis - Mulderij et al. 2003), Chara globularis (Jacobsen &

Pedersen 1983, Blindow & Hootsman 1991, Kleiven 1991, Jasser 1995, Mulderij et al. 2003, Berger

& Schagerl 2004), Chara hispida (Wium-Andersen et al. 1982), Chara tomentosa (Kleiven &

Szczepańska 1988, Kleiven 1991), Nitella opaca (Berger & Schagerl 2004), Nitellopsis obtusa

(Berger & Schagerl 2004) and Tolypella nidifica (Wium-Andersen et al. 1982).

Indirect effects of allelochemicals

Apart from direct effects of allelochemicals on aquatic fauna species, the biochemicals produced by

macrophytes can affect the fauna indirectly. The allelopathic activity of the macrophytes can have

different effects on different autotrophic taxa, some which may constitute an important food resource

for the fauna. For example Hilt (2006) suggested that epiphytes are less sensitive to exudates of M.

spicatum compared to phytoplankton. Furthermore, green algae have been found to be more resistant

than cyanobacteria and diatoms when grown under influence of M. spicatum (Körner & Nicklisch

2002) and M. verticillatum (Hilt et al. 2006). However, Nakai & Hosomi (2002) found diatoms to be

more resistant than green algae and cyanobacteria to allelochemicals produced by M. spicatum.

Generally, cyanobacteria seem to be especially sensitive to allelopathic substances produced by

macrophytes (Jasser 1995). Also differences within taxonomic groups have been studied. Mulderij et

al. (2003) found a difference in effect of C. globularis and C. contraria allelopathy on three

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planktonic green algae. Some microalgae have been observed to increase in abundance when

exposed to allelopathic chemicals (Blindow & Hootsman 1991, Jasser 1995, Erhard & Gross 2006,

Hilt 2006, Hilt et al. 2006). These effects on the periphyton and plankton community may influence

the habitat choice of invertebrates with feeding preferences for certain types of microalgae.

However, the results suggesting allelochemical activity of different macrophyte species is not

unambiguous, and different studies have contrasting conclusions about the allelochemical activity of

a certain species. Furthermore, the production and effects of allelochemicals can vary with time and

stress (e.g. nutrient limitation) (Reigosa et al. 1999, Gross 2003, Hilt et al. 2006). Additionally, the

evidence of allelopathy is mainly from laboratory work, while there are fewer observations of

allelopathy in situ (Gross 2003). Forsberg et al. (1990) reported for example an absence of

allelopathic effects from Chara spp. on phytoplankton in situ.

Effects of macrophyte diversity and habitat size

Until now the functional role and effects of specific species or groups of macrophytes on the aquatic

fauna communities have been considered, except for the overall function of the macrophyte

structure. In this section I will focus further on the effects of the whole macrophyte community on

the associated fauna assemblages concerning two measures; diversity of macrophytes and size of the

macrophyte habitats.

Effects of macrophyte diversity

According to general ecological literature we should expect the diversity of consumers to increase

with an increased diversity of resources (Begon et al. 2005). This means that with an increased

number of macrophyte species a heterogeneous environment should be provided for the macrophyte-

associated fauna to forage in and the diversity of the fauna should increase. Studies on the effects of

plant diversity on fauna diversity are limited in aquatic environments. In terrestrial grasslands,

arthropod species diversity has been shown to be positively correlated with plant diversity (Siemann

et al. 1998, Haddad et al. 2001). In one of these studies the abundance of arthropods was also

positively related to plant diversity (Haddad et al. 2001) whilst not in the other (Siemann et al.

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1998). Two studies in North American lakes reveal a similar pattern. Brown et al. (1988) found an

increase in diversity and abundance of macroinvertebrate epifauna with an increase in macrophyte

diversity in Lake St. Clair, Michigan (Fig. 4). Tonn and Magnusson (1982) found that fish diversity

increased with macrophyte vegetation diversity during summer in a study of 18 Wisconsin lakes.

Similarly, marine motile epifauna has been shown to increase with macrophyte diversity (Parker et

al. 2001). However, the relationship in the latter study was weak. It has been suggested that the

functional and structural properties of the habitat (surface area or complexity) is more important than

the plant species diversity per se for faunal species richness (Parker et al. 2001 and references

therein). But Symstad et al. (2000) concluded in their study of arthropods in grasslands that the

number of functional groups of plants (classified according to their effects on ecosystem processes)

was only partly relevant for consumer diversity and abundance. The consumer diversity was instead

related to number of plant taxa.

Figure 4. Average number of macroinvertebrate epifauna (phytomacrofauna) taxa per sample and the macroinvertebrate epifauna densities per m2 related to number of macrophyte taxa per sample (95% confidence intervals). Number of observations in parentheses. From Brown et al. 1988.

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Effects of habitat size

Ecological theories have for long considered the effect of habitat size on the species richness and

complexity of ecosystems. Large habitats are almost by definition more complex than smaller, and a

more complex habitat can be inhabited by a richer organism community than a small habitat

(Statzner & Moss 2004, Lomolino et al. 2006). However, when looking at recent studies of seagrass

habitats the effect of habitat size on fauna richness is often lacking (Bell et al. 2001, Barbera-Cebrian

et al. 2002, Hovel & Lipcius 2002, Nakaoka 2005, Jelbart et al. 2006). Large seagrass beds do not in

general seem to have a more species rich fauna community compared to smaller fragmented seagrass

beds. However, the pattern changes with scale. On a smaller scale (order of 101 m2 instead of >102

m2) the fauna richness increases with a larger habitat (Jelbart et al. 2006, however see Bell et al.

2006). Seagrass beds often consist of a relative low number of seagrass species (Hemminga &

Duarte 2000). This could be one explanation for the observed pattern; on a small scale the habitat

complexity increases with size, but on a larger scale this effect levels off. The diversity of some

faunal groups can even be higher in fragmented and diversified seagrass habitats compared to large

homogenous seagrass beds (e.g. mysids (Barbera-Cebrian et al. 2002)). In a study of freshwater

stream invertebrates Taniguchi et al. (2003) found an increase of taxon richness, abundance and

biomass with increased patch size of artificial macrophytes on a small scale (102-104 cm), however

the relationship was not significant for natural macrophytes. To conclude, it seems as if the

relationship between faunal community parameters and patch area in aquatic environments does not

follow a consistent pattern and needs to be further examined.

The distribution of fauna is often not homogenous in stands of macrophytes. For the fauna associated

with submersed macrophytes, being close to the edge could be advantageous for some species and

disadvantaged for others, depending on their different ecological traits. At the edge the predation

pressure may be stronger (Diehl 1988), but the abundance of food higher, compared to further inside

a habitat (Blindow 1987, Marklund et al. 2001). This trade-off between higher food availability and

higher predation risk at the edge is probably more profound for species at low trophic levels than

species at high trophic levels. It may also vary with time (Marklund et al. 2001) and with size of the

macrophyte habitat (Jelbart et al. 2006 and references therein). Because of these possible differences

in habitat preference between fauna species it is hard to make general conclusions of the total density

and species richness of fauna with distance to edge of the habitat. For example, Bell et al. (2001)

found no clear result for different fauna taxa groups in preferring edge or interior of seagrass beds.

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Marklund et al. (2001) found the densities of macroinvertebrates to be higher at the edge than in the

interior of Chara spp. vegetation, while Jelbart et al. (2006) found a lower species richness of small

fish at the edge than interior of large seagrass meadows.

Potential effects of vegetation changes on the fauna in soft-bottom bays of the Baltic Sea

From the literature summarized in this paper it is evident that aquatic angiosperms and charophytes

affect the aquatic fauna in several ways. 1) They can influence the fauna communities by their

structure altering food web interactions. 2) Their structures also affect the production of periphyton,

which in turn influence the fauna by being an important food resource. 3) Live aquatic angiosperms

and charophytes are also consumed directly by macroinvertebrates and fish. However, the

consumption rate is higher on macrophyte detritus. 4) The production of allelochemicals by

macrophytes can have an impact on the plant associated fauna both directly and indirectly by being

toxic to the animals or affecting the periphyton composition. 5) Different plants can have different

effects on the fauna due to their physical and chemical properties, life-cycle or origin. 6) The

taxonomic and/or functional diversity of macrophytes can affect the associated fauna diversity.

With these functions and effects in mind, I will here briefly discuss potential effects of vegetation

changes caused by eutrophication on the fauna community in shallow soft-bottom bays of the Baltic

Sea. The flora of the Baltic Sea is composed of both marine and freshwater species and in shallow

soft-bottom bays freshwater species dominate (e.g. Munsterhjelm 1997). The main factors inducing

changes in the benthic vegetation in the Baltic Sea are salinity, depth, light, temperature, wave action

and substrate, as well as the anthropogenic nutrient enrichment and pollution (Kautsky 1988). With

the eutrophication of coastal areas in the Baltic Sea the primary production have increased, in

particular that of filamentous and sheet-like fast-growing algae (Fletcher 1996, Schramm & Nienhuis

1996). In shallow soft-bottom bays the abundance and diversity of charophytes have decreased,

while the angiosperms Ceratophyllum demersum, Myriophyllum spicatum and Potamogeton

pectinatus have increased with the eutrophication process (Blindow 2000, Schubert & Blindow 2003,

Munsterhjelm 2005). One plausible change in the fauna community of these soft-bottom bays with

eutrophication is that the densities of aquatic fauna increase as the production of primary producers

increase, especially that of filamentous non-vascular macrophytes, which are an important food

resource. However, a substantial higher production of macrophytes may lead to anoxic conditions

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during respiration or degradation, which can cause high mortality of fauna with low mobility

(Fletcher 1996, Norkko & Bonsdorff 1996). In eutrophied enclosed shallow bays of the Baltic Sea

very low oxygen levels have been observed during early morning in very dense stands of

angiosperms (mainly M. spicatum) covered with fast growing green algae (Ulva spp. and

Cladophora spp.) (L. Kautsky pers. comm.). Furthermore, in these bays the oxygen levels may drop

to extremely low levels during winter when the plants are decomposing and an ice-cover prevents

oxygen to dissolve in the water.

As M. spicatum increase in density with eutrophication of shallow Baltic bays it may affect the fauna

community directly by its allelochemical substances. For example Lindén & Lehtiniemi (2005)

showed that dense patches of M. spicatum was lethal to mysids and at lower densities of the plant

both stickleback larvae and the mysid Neomysis integer avoided M. spicatum even in the presence of

predator signals. There may also be indirect effects on the fauna community by allelochemicals as

they can have impacts on the periphyton production, and thereby alter the food supply. Chara spp.

has been suggested to generally have low abundance of periphyton, which can be related to their

production of allelochemicals (Wium-Andersen et al. 1982, however see Blindow 1987). Hence, in

non-eutrophied Baltic bays with abundant Chara spp. vegetation the densities of periphyton may be

low. With the eutrophication process the production of periphyton may increase both as a result of

decreased Chara spp. densities and increased nutrient levels in the water.

If the diversity of macrophytes decreases with eutrophication we can expect decreased fauna

diversity in accordance with the studies of e.g. Brown et al. (1988) and Tonn & Magnusson (1982).

According to Parker et al. (2001) however, we should expect an effect on the fauna community with

changes in the functions that macrophytes provide, rather than with diversity per se. Increased

abundance of structurally complex species like Myriophyllum spp. and P. pectinatus with

eutrophication may support higher densities of macroinvertebrates compared to less complex species

like Chara spp. and low-growing angiosperms which thrive in less eutrophied waters (e.g.

Callitriche hermafroditica) (McAbendroth et al. 2005).

Dahlgren & Kautsky (2004) have suggested three alternative states for shallow soft-bottom bays in

the Baltic Sea along a eutrophication gradient; I) a vegetated clear water state under low nutrient

levels, II) a very densely vegetated state with high abundance of periphytic algae and low

chlorophyll a concentrations in the water under an intermediate nutrient load, and III) a non-

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vegetated state with high chlorophyll a concentrations in the water under hypereutrophic conditions.

As already mentioned there are several documentations of lakes where the vegetation cover has

decreased dramatically with shifts between vegetated and non-vegetated states. Non-vegetated turbid

states provide less structure for fauna species to escape predators and hence trophic interactions can

be stronger with predators decreasing prey populations. Furthermore, with the disappearance of

vertical structures on soft-bottoms the production of periphyton will decrease. Generally, there will

be less plant resources available other than phytoplankton in a turbid non-vegetated state. This will

benefit planktivores but not other herbivorous species. In temperate non-vegetated turbid lakes

planktivorous and benthivorous cyprinid fishes usually dominate together with the piscivore

pikeperch (Sander lucioperca) (Meijer et al. 1995, Scheffer 2004 and references therein). In

comparison vegetated lakes usually have a higher share of piscivores to the total fish biomass, with

perch and pike being abundant. From studies in a number of lakes it is apparent that generally the

diversity of birds, fish and invertebrates as well as the whole lake bio-production decrease with shifts

to non-vegetated turbid states (Hargeby et al. 1994, Meijer et al. 1995, Scheffer 2004).

In conclusion we can expect the fauna community of shallow soft-bottom bays in the Baltic to

change as a response to vegetation changes caused by eutrophication. The changes in fauna

community structure can be facilitated through a number of altered functions and effects of the plant

community. However, today there are few studies of such changes and our knowledge of the role of

angiosperms and charophytes for the fauna community in shallow soft-bottom bays in the Baltic is

poor. This review compiled knowledge from lakes and seagrass habitats to address the potential role

of macrophytes in shallow soft-bottom bays in the Baltic, however if the mechanisms are similar still

needs to be tested.

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References

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Aliotta, G., Della Greca, M., Monaco, P., Pinto, G., Pollio, A. & Previtera, L. (1990) Invitro algal growth-inhibition by phytotoxins of Typha latifolia L. - Journal of Chemical Ecology 16: 2637-2646.

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Serien Plants & Ecology (ISSN 1651-9248) har tidigare haft namnen "Meddelanden från Växtekologiska avdelningen, Botaniska institutionen, Stockholms Universitet" nummer 1978:1 – 1993:1 samt "Växtekologi". (ISSN 1400-9501) nummer 1994:1 – 2003:3. Följande publikationer ingår i utgivningen: 1978:1 Liljelund, Lars-Erik : Kompendium i matematik för ekologer. 1978:2 Carlsson, Lars: Vegetationen på Littejåkkadeltat vid Sitasjaure, Lule Lappmark. 1978:3 Tapper, Per-Göran: Den maritima lövskogen i Stockholms skärgård. 1978:4: Forsse, Erik: Vegetationskartans användbarhet vid detaljplanering av fritidsbebyggelse. 1978:5 Bråvander, Lars-Gunnar och Engelmark, Thorbjörn : Botaniska studier vid Porjusselets

och St. Lulevattens stränder i samband med regleringen 1974. 1979:1 Engström, Peter: Tillväxt, sulfatupptag och omsättning av cellmaterial hos pelagiska

saltvattensbakterier. 1979:2 Eriksson, Sonja: Vegetationsutvecklingen i Husby-Långhundra de senaste tvåhundra åren. 1979:3 Bråvander, Lars-Gunnar: Vegetation och flora i övre Teusadalen och vid Auta- och

Sitjasjaure; Norra Lule Lappmark. En översiktlig inventering med anledning av områdets exploatering för vattenkraftsändamål i Ritsemprojektet.

1979:4 Liljelund, Lars-Erik, Emanuelsson, Urban, Florgård, C. och Hofman-Bang, Vilhelm: Kunskapsöversikt och forskningsbehov rörande mekanisk påverkan på mark och vegetation.

1979:5 Reinhard, Ylva: Avloppsinfiltration - ett försök till konsekvensbeskrivning. 1980:1 Telenius, Anders och Torstensson, Peter: Populationsstudie på Spergularia marina och

Spergularia media. I Frödimorfism och reproduktion. 1980:2 Hilding, Tuija : Populationsstudier på Spergularia marina och Spergularia media.

II Resursallokering och mortalitet. 1980:3 Eriksson, Ove: Reproduktion och vegetativ spridning hos Potentilla anserina L. 1981:1 Eriksson, Torsten: Aspekter på färgvariation hos Dactylorhiza sambucina. 1983:1 Blom, Göran: Undersökningar av lertäkter i Färentuna, Ekerö kommun. 1984:1 Jerling, Ingemar: Kalkning som motåtgärd till försurningen och dess effekter på blåbär,

Vaccinium myrtillus. 1986:1 Svanberg, Kerstin: En studie av grusbräckans (Saxifraga tridactylites) demografi. 1986:2 Nyberg, Hans: Förändringar i träd- och buskskiktets sammansättning i ädellövskogen på

Tullgarnsnäset 1960-1983. 1987:1 Edenholm, Krister: Undersökningar av vegetationspåverkan av vildsvinsbök i

Tullgarnsområdet. 1987:2 Nilsson, Thomas: Variation i fröstorlek och tillväxthastighet inom släktet Veronica. 1988:1 Ehrlén, Johan: Fröproduktion hos vårärt (Lathyrus vernus L.). - Begränsningar och

reglering. 1988:2 Dinnétz, Patrik: Local variation in degree of gynodioecy and protogyny in Plantago

maritima. 1988:3 Blom, Göran och Wincent, Helena: Effekter of kalkning på ängsvegetation. 1989:1 Eriksson, Pia: Täthetsreglering i Littoralvegetation. 1989:2 Kalvas, Arja : Jämförande studier av Fucus-populationer från Östersjön och västkusten. 1990:1 Kiviniemi, Katariina : Groddplantsetablering och spridning hos smultron, Fragaria vesca. 1990:2 Idestam-Almquist, Jerker: Transplantationsförsök med Borstnate.

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1992:1 Malm, Torleif : Allokemisk påverkan från mucus hos åtta bruna makroalger på epifytiska alger.

1992:2 Pontis, Cristina: Om groddknoppar och tandrötter. Funderingar kring en klonal växt: Dentaria bulbifera.

1992:3 Agartz, Susanne: Optimal utkorsning hos Primula farinosa. 1992:4 Berglund, Anita: Ekologiska effekter av en parasitsvamp - Uromyces lineolatus på Glaux

maritima (Strandkrypa). 1992:5 Ehn, Maria : Distribution and tetrasporophytes in populations of Chondrus crispus

Stackhouse (Gigartinaceae, Rhodophyta) on the west coast of Sweden. 1992:6 Peterson, Torbjörn: Mollusc herbivory. 1993:1 Klásterská-Hedenberg, Martina: The influence of pH, N:P ratio and zooplankton on the

phytoplanctic composition in hypertrophic ponds in the Trebon-region, Czech Republic. 1994:1 Fröborg, Heléne: Pollination and seed set in Vaccinium and Andromeda. 1994:2 Eriksson, Åsa: Makrofossilanalys av förekomst och populationsdynamik hos Najas flexilis

i Sörmland. 1994:3 Klee, Irene: Effekter av kvävetillförsel på 6 vanliga arter i gran- och tallskog. 1995:1 Holm, Martin : Beståndshistorik - vad 492 träd på Fagerön i Uppland kan berätta. 1995:2 Löfgren, Anders: Distribution patterns and population structure of an economically

important Amazon palm, Jessenia bataua (Mart.) Burret ssp. bataua in Bolivia. 1995:3 Norberg, Ylva: Morphological variation in the reduced, free floating Fucus vesiculosus, in

the Baltic Proper. 1995:4 Hylander, Kristoffer & Hylander, Eva : Mount Zuquala - an upland forest of Ethiopia.

Floristic inventory and analysis of the state of conservation. 1996:1 Eriksson, Åsa: Plant species composition and diversity in semi-natural grasslands - with

special emphasis on effects of mycorrhiza. 1996:2 Kalvas, Arja: Morphological variation and reproduction in Fucus vesiculosus L.

populations. 1996:3 Andersson, Regina: Fågelspridda frukter kemiska och morfologiska egenskaper i relation

till fåglarnas val av frukter. 1996:4 Lindgren, Åsa: Restpopulationer, nykolonisation och diversitet hos växter i

naturbetesmarker i sörmländsk skogsbygd. 1996:5 Kiviniemi, Katariina : The ecological and evolutionary significance of the early life cycle

stages in plants, with special emphasis on seed dispersal. 1996:7 Franzén, Daniel: Fältskiktsförändringar i ädellövskog på Fagerön, Uppland, beroende på

igenväxning av gran och skogsavverkning. 1997:1 Wicksell, Maria : Flowering synchronization in the Ericaceae and the Empetraceae. 1997:2 Bolmgren, Kjell : A study of asynchrony in phenology - with a little help from Frangula

alnus. 1997:3 Kiviniemi, Katariina : A study of seed dispersal and recruitment of plants in a fragmented

habitat. 1997:4 Jakobsson, Anna: Fecundity and abundance - a comparative study of grassland species. 1997:5 Löfgren, Per: Population dynamics and the influence of disturbance in the Carline Thistle,

Carlina vulgaris. 1998:1 Mattsson, Birgitta: The stress concept, exemplified by low salinity and other stress factors

in aquatic systems.

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1998:2 Forsslund, Annika & Koffman, Anna : Species diversity of lichens on decaying wood - A comparison between old-growth and managed forest.

1998:3 Eriksson, Åsa: Recruitment processes, site history and abundance patterns of plants in semi-natural grasslands.

1998:4 Fröborg, Heléne: Biotic interactions in the recruitment phase of forest field layer plants. 1998:5 Löfgren, Anders: Spatial and temporal structure of genetic variation in plants. 1998:6 Holmén Bränn, Kristina : Limitations of recruitment in Trifolium repens. 1999:1 Mattsson, Birgitta: Salinity effects on different life cycle stages in Baltic and North Sea

Fucus vesiculosus L. 1999:2 Johannessen, Åse: Factors influencing vascular epiphyte composition in a lower montane

rain forest in Ecuador. An inventory with aspects of altitudinal distribution, moisture, dispersal and pollination.

1999:3 Fröborg, Heléne: Seedling recruitment in forest field layer plants: seed production, herbivory and local species dynamics.

1999:4 Franzén, Daniel: Processes determining plant species richness at different scales - examplified by grassland studies.

1999:5 Malm, Torleif : Factors regulating distribution patterns of fucoid seaweeds. A comparison between marine tidal and brackish atidal environments.

1999:6 Iversen, Therese: Flowering dynamics of the tropical tree Jacquinia nervosa. 1999:7 Isæus, Martin: Structuring factors for Fucus vesiculosus L. in Stockholm south archipelago

- a GIS application. 1999:8 Lannek, Joakim: Förändringar i vegetation och flora på öar i Norrtälje skärgård. 2000:1 Jakobsson, Anna: Explaining differences in geographic range size, with focus on dispersal

and speciation. 2000:2 Jakobsson, Anna: Comparative studies of colonisation ability and abundance in semi-

natural grassland and deciduous forest. 2000:3 Franzén, Daniel: Aspects of pattern, process and function of species richness in Swedish

seminatural grasslands. 2000:4 Öster, Mathias: The effects of habitat fragmentation on reproduction and population

structure in Ranunculus bulbosus. 2001:1 Lindborg, Regina: Projecting extinction risks in plants in a conservation context. 2001:2 Lindgren, Åsa: Herbivory effects at different levels of plant organisation; the individual

and the community. 2001:3 Lindborg, Regina: Forecasting the fate of plant species exposed to land use change. 2001:4 Bertilsson, Maria: Effects of habitat fragmentation on fitness components. 2001:5 Ryberg, Britta : Sustainability aspects on Oleoresin extraction from Dipterocarpus alatus. 2001:6 Dahlgren, Stefan: Undersökning av fem havsvikar i Bergkvara skärgård, östra egentliga

Östersjön. 2001:7 Moen, Jon; Angerbjörn, Anders; Dinnetz, Patrik & Er iksson Ove: Biodiversitet i fjällen

ovan trädgränsen: Bakgrund och kunskapsläge. 2001:8 Vanhoenacker, Didrik: To be short or long. Floral and inflorescence traits of Bird`s eye

primrose Primula farinose, and interactions with pollinators and a seed predator. 2001:9 Wikström, Sofia: Plant invasions: are they possible to predict? 2001:10 von Zeipel, Hugo: Metapopulations and plant fitness in a titrophic system – seed predation

and population structure in Actaea spicata L. vary with population size.

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2001:11 Forsén, Britt: Survival of Hordelymus europaéus and Bromus benekenii in a deciduous forest under influence of forest management.

2001:12 Hedin, Elisabeth: Bedömningsgrunder för restaurering av lövängsrester i Norrtälje kommun.

2002:1 Dahlgren, Stefan & Kautsky, Lena: Distribution and recent changes in benthic macrovegetation in the Baltic Sea basins. – A literature review.

2002:2 Wikström, Sofia: Invasion history of Fucus evanescens C. Ag. in the Baltic Sea region and effects on the native biota.

2002:3 Janson, Emma: The effect of fragment size and isolation on the abundance of Viola tricolor in semi-natural grasslands.

2002:4 Bertilsson, Maria: Population persistance and individual fitness in Vicia pisiformis: the effects of habitat quality, population size and isolation.

2002:5 Hedman, Irja : Hävdhistorik och artrikedom av kärlväxter i ängs- och hagmarker på Singö, Fogdö och norra Väddö.

2002:6 Karlsson, Ann: Analys av florans förändring under de senaste hundra åren, ett successionsförlopp i Norrtälje kommuns skärgård.

2002:7 Isæus, Martin: Factors affecting the large and small scale distribution of fucoids in the Baltic Sea.

2003:1 Anagrius, Malin : Plant distribution patterns in an urban environment, Södermalm, Stockholm.

2003:2 Persson, Christin: Artantal och abundans av lavar på askstammar – jämförelse mellan betade och igenvuxna lövängsrester.

2003:3 Isæus, Martin: Wave impact on macroalgal communities. 2003:4 Jansson-Ask, Kristina: Betydelsen av pollen, resurser och ljustillgång för reproduktiv

framgång hos Storrams, Polygonatum multiflorum. 2003:5 Sundblad, Göran: Using GIS to simulate and examine effects of wave exposure on

submerged macrophyte vegetation. 2004:1 Strindell, Magnus: Abundansförändringar hos kärlväxter i ädellövskog – en jämförelse av

skötselåtgärder. 2004:2 Dahlgren, Johan P: Are metapopulation dynamics important for aquatic plants? 2004:3 Wahlstrand, Anna: Predicting the occurrence of Zostera marina in bays in the Stockholm

archipelago,northern Baltic proper. 2004:4 Råberg, Sonja: Competition from filamentous algae on Fucus vesiculosus – negative

effects and the implications on biodiversity of associated flora and fauna. 2004:5 Smaaland, John: Effects of phosphorous load by water run-off on submersed plant

communities in shallow bays in the Stockholm archipelago. 2004:6 Ramula Satu: Covariation among life history traits: implications for plant population

dynamics. 2004:7 Ramula, Satu: Population viability analysis for plants: Optimizing work effort and the

precision of estimates. 2004:8 Niklasson, Camilla: Effects of nutrient content and polybrominated phenols on the

reproduction of Idotea baltica and Gammarus ssp. 2004:9 Lönnberg, Karin: Flowering phenology and distribution in fleshy fruited plants. 2004:10 Almlöf, Anette: Miljöfaktorers inverkan på bladmossor i Fagersjöskogen, Farsta,

Stockholm.

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2005:1 Hult, Anna: Factors affecting plant species composition on shores - A study made in the Stockholm archipelago, Sweden.

2005:2 Vanhoenacker, Didrik: The evolutionary pollination ecology of Primula farinosa. 2005:3 von Zeipel, Hugo: The plant-animal interactions of Actea spicata in relation to spatial

context. 2005:4 Arvanitis, Leena T.: Butterfly seed predation. 2005:5 Öster, Mathias: Landscape effects on plant species diversity – a case study of Antennaria

dioica 2005:6 Boalt, Elin: Ecosystem effects of large grazing herbivores: the role of nitrogen. 2005:7 Ohlson, Helena: The influence of landscape history, connectivity and area on species

diversity in semi-natural grasslands. 2005:8 Schmalholz, Martin: Patterns of variation in abundance and fecundity in the endangered

grassland annual Euphrasia rostkovia ssp. Fennica. 2005:9 Knutsson, Linda: Do ants select for larger seeds in Melampyrum nemorosum? 2006:1 Forslund, Helena: A comparison of resistance to herbivory between one exotic and one

native population of the brown alga Fucus evanescens. 2006:2 Nordqvist, Johanna: Effects of Ceratophyllum demersum L. on lake phytoplankton

composition. 2006:3 Lönnberg, Karin: Recruitment patterns, community assembly, and the evolution of seed

size. 2006:4 Mellbrand, Kajsa: Food webs across the waterline - Effects of marine subsidies on coastal

predators and ecosystems. 2006:5 Enskog, Maria: Effects of eutrophication and marine subsidies on terrestrial invertebrates

and plants. 2006:6 Dahlgren, Johan: Responses of forest herbs to the environment 2006:7 Aggemyr, Elsa: The influence of landscape, field size and shape on plant species diversity

in grazed former arable fields. 2006:8 Hedlund, Kristina: Flodkräftor (Astacus astacus) i Bornsjön, en omnivors påverkan på

växter och snäckor. 2007:1 Eriksson, Ove: Naturbetesmarkernas växter- ekologi, artrikedom och bevarandebiologi. 2007:2 Schmalholz, Martin: The occurrence and ecological role of refugia at different spatial

scales in a dynamic world. 2007:3 Vikström, Lina: Effects of local and regional variables on the flora in the former semi-

natural grasslands on Wäsby Golf club’s course.