an aquatic invertebrate survey of ickworth park, suffolk

55 AN AQUATIC INVERTEBRATE SURVEY OF ICKWORTH PARK, SUFFOLK

Trans. Suffolk Nat. Soc. 40 (2004)

AN AQUATIC INVERTEBRATE SURVEY OF ICKWORTH PARK, SUFFOLK

DAVID J. LEEMING AND STUART WARRINGTON

Introduction Aquatic invertebrates are a particularly valuable suite of species for the assessment of the habitat quality of wetland sites. This is because their life cycles are relatively long, they live in intimate contact with the water and sediments, they are relatively sedentary and they exhibit a range of tolerances to pollutants and habitat change. In addition, for many aquatic taxa there is a good level of knowledge about their habitat requirements, their distribution and rarity and, importantly, there are good identification keys available.

Ickworth Park, owned by the National Trust, in west Suffolk is probably most renowned for its parkland habitat with many veteran trees, especially oaks. However, it does also have a number of wetland habitats. The main wetland feature is the River Linnet, a small river which enters the park in the south-east corner, and sweeps through a wide valley turning clockwise to exit the park to the north. The River Linnet has been dammed in two places to create the Fairy Lake and The Canal. In addition, there are numerous ponds around the estate, both in the woodland and in the grassland.

The aim of the survey was to examine a range of the wetland habitats at Ickworth for their aquatic invertebrate assemblage to help in the assessment of these habitats and to inform possible management. The species included in the survey were macroinvertebrates that complete all or part of their lifecycle underwater.

Methods The survey was carried out on 6th August 2003. At each sample site, the collection of aquatic invertebrates was by the active use of a long-handled pond-net, employing a combination of kick-sampling and net-sweep techniques, for a total duration of three minutes, supplemented by a hand search of appropriate surfaces or objects (where necessary).

All parts of a site (centre, margins and extreme edges) were sampled, except where a combination of deep water or deep silt precluded access. Care was taken to ensure collection of invertebrates from both open-water and densely vegetated areas. Attention was given to sampling amongst different vegetation types and/or detrital habitats that were present. Sweeps of the net were also used to collect surface-dwelling invertebrates on arrival at the site, prior to disturbance of the sampling area, or whenever such taxa were seen during sampling. Open water areas were sampled by broad, swift sweeps of the net. Soft silts, including muddy edge habitats, were sampled by skimming their surface with the pond net (to a depth of 2–5 cm). The extreme edges or undercut banks of particular ponds were sampled by splashing and subsequent netting of displaced macroinvertebrates. Wet areas of reed or fen litter were sampled by creating puddles through trampling, followed by sweep netting.

The sampling approach followed is capable of collecting perhaps 60–80% of the taxa actually present at the time of the sampling (Furse et al, 1981).


Suffolk Natural History, Vol. 40 56

NGR Site number and name

TL818604 1. Fairy Lake (2 samples)

TL822607 2. Sedge Pond N.E. of Fairy Lake

TL821610 3. Fontainebleau Grove Pond

TL816605 4. River Linnet outfall from Fairy Lake

TL818603 5. Sedge Pond, south of Fairy Lake

TL809612 6. Golden Pond

TL806613 7. River Linnet, Deer Park

TL810609 8. The Canal lake

TL813613 9. Parsons Pond

TL812629 10. River Linnet near Mordaboys Cottage

TL813620 11. Dairy House Pond

Samples were preserved in 70% Industrial Methylated Spirit on site, stored in buckets with airtight lids. Prior to sorting, silt was washed from samples by thoroughly rinsing with tap water through a 500 um sieve. Larger aperture sieves were also used to split the sample into size fractions to aid sorting. Material was systematically inspected to find all the invertebrates. Taxa were generally identified to species-level, however, identification to genus or Order was necessary for the poorly described larvae of particular Diptera (flies) and immature or damaged specimens. Oligochaeta (worms), Chironomidae (midge larvae) and Hydracarina (water mites) were found, but not identified.

Records obtained from the present survey have been supplemented by information from entomologists who have undertaken recording activities at Ickworth, notably David Nash, Andrew Foster and Colin Plant.

The sites sampled are listed in Table 1. Following the protracted dry hot summer of 2003 all semi-permanent or ephemeral waterbodies within the estate had dried completely by August and sampling of these areas, as and when conditions permit, would be invaluable.

The conservation importance of samples and sites was assessed using a simple scoring system following an English Nature methodology for which RDB species are allocated 100 points, Notable A species 50 pts, Notable B (or Notable) 40 pts and Local species 10 pts.

Table 1. Sampling locations at Ickworth Park

Results A total of 148 aquatic macro-invertebrate species were recorded during this one-day survey. Table 2 summarises the data for each sampling site by major groups and Table 3 provides the list of all the aquatic species recorded during this and other surveys. A further 13 species of aquatic Coleoptera, 9 species of Diptera with aquatic larvae and 2 Odonata have been recorded at Ickworth which brings the total macroinverterate taxa list to 172 species.

Insects made up the majority (83%) of the species recorded and there were 56 water beetle species (33% of total). Larvae and adults were identified for 8 of the 10 Odonata (dragonfly) species observed at Ickworth in 2003, with just Aeshna grandis (Brown hawker) and Sympetrum sanguineum (Ruddy darter) only observed as adults.



Table 2 Numbers of species of the principal Aquatic Macroinvertebrate Groups at each sample site.

Site n

um

ber:

1

2

3

4

5

6

7

8

9

10

11

all

all

Tricla

did

a (flatworm

s) 1

- 1

1

0

0

0

0

0

0

0

1

1

Gastro

poda (sn

ails & lim

pets)

6

- 1

2

3

5

4

8

7

3

5

11

11

Biv

alvia

(pea m

ussels)

4

- 2

3

0

2

2

2

0

1

2

5

5

Hiru

din

ea (leech

es) 6

- 2

3

3

2

3

5

6

3

5

9

9

Mala

costra

ca (sh

rimps, slaters)

3

- 2

2

3

2

1

2

1

2

2

4

4

Ephem

eroptera

(mayflies)

1

- 1

1

2

2

2

3

1

4

1

7

7

Odo

nata

(drag

on

flies) 9

- 1

0

5

3

2

5

1

0

4

8

10

Hem

iptera

(water b

ugs)

7

- 4

5

8

3

5

7

5

3

2

19

19

Meg

alo

ptera

(alderflies)

1

- 0

1

0

0

1

1

0

0

0

1

1

Coleo

ptera

(beetles)

15

11

4

19

12

21

17

9

6

11

2

43

56

Lep

idoptera

(moth

s) 0

- 0

0

0

0

0

1

0

0

1

2

2

Trich

optera

(caddis flies)

1

- 1

1

0

0

1

6

0

2

1

10

10

Dip

tera (tru

e flies) 21

- 8

10

7

9

8

2

4

6

2

28

37

Tota

l 75

11

27

48

43

49

46

51

31

3

5

27

148

172

Fairy Lake: all data

Sedge Pond N.E. of Fairy Lake*

Fontainebleu Wood Pond

River Linnet below Fairy Lake

Sedge Pond S of Fairy Lake

Golden Pond

River Linnet Deer Park

The Canal lake

Parsons Pond

River Linnet Mordaboys

Dairy House Pond

Ickworth Park Survey 6/8/2003

Ickworth Park: all data

* Water beetles only sampled.



Taxa Sample Locations

(River Linnet sites in Bold)

Phylum: PLATYHELMINTHES

Class: Tricladida (flatworms)

Polycelis nigra group 1, 3, 4

Phylum: MOLLUSCA (molluscs)

Class: Gastropoda (snails and limpets)

Potamopyrgus antipodarum 7, 8

Lymnaea truncatula 8, 10

Lymnaea stagnalis 6, 9

Lymnaea auricularia 11,

Lymnaea peregra 1, 4, 7, 8, 9, 10, 11

Planorbis carinatus 9, 11

Anisus vortex 7, 8, 10

Gyraulus albus 1, 4, 5, 6, 7, 8, 9, 11

Armiger crista 1, 6, 8, 9

Hippeutis complanatus 1, 4, 6, 8, 9, 11

Acroloxus lacustris 1, 3, 5, 6, 8, 9

Class: BIVALVIA (bivalve molluscs or pea mussels)

Sphaerium corneum 1, 4

Sphaerium lacustre 11

Pisidium milium 1, 3, 4, 6, 7

Pisidium nitidum 1, 8, 10, 11

Pisidium subtruncatum 1, 3, 4, 6, 7, 8

Phylum: ANNELIDA

Class: Hirudinea (leeches)

Theromyzon tessulatum 1, 8, 9, 11

Hemiclepsis marginata 9, 11

Glossiphonia complanata 1, 3, 4, 5, 7, 8, 9, 10, 11

Glossiphonia heteroclita 1, 6, 8

Helobdella stagnalis 1, 3, 4, 5, 6, 8, 9, 11

Haemopis sanguisuga 7

Erpobdella testacea 9

Erpobdella octoculata 1, 4, 5, 7, 8, 9, 10, 11

Trocheta bykowskii 1, 10

Phylum: CRUSTACEA (crustaceans)

Order: Isopoda (water slaters or hog lice)

Asellus aquaticus 1, 3, 4, 5, 10, 11

Asellus meridianus 3, 6

Table 3 A list of invertebrate taxa recorded at Ickworth Park (additional records from David Nash (DRN) in 1999, Andy Foster (APF) in 2003 or Colin Plant (CWP) in 2003)



Order: Amphipoda (shrimps)

Crangonyx pseudogracilis 1, 5, 6, 8, 9, 11

Gammarus pulex 1, 4, 5, 7, 8, 10

INSECTS

Order: Ephemeroptera (mayflies)

Baetis rhodani 10

Baetis vernus 10

Cloeon dipterum 1, 3, 4, 5, 6, 7, 8, 9, 10, 11

Centroptilum luteolum 10

Habrophlebia fusca 7

Caenis macrura 8

Caenis robusta 5, 6, 8

Order: Odonata (dragonflies and damselflies)

Calopteryx splendens (Banded demoiselle) 7

Coenagrion puella (Azure damselfly) 1, 5, 8 (APF)

Enallagma cyathigerum (Common blue damselfly) 1 (CWP), 8

Pyrrhosoma nymphula (Large red damselfly) 1, 5, 6, 8, 11

Ischnura elegans (Blue-tailed damselfly) 1, 5, 6, 7, 8, 9, 11

Aeshna cyanea (Southern hawker) 1, 3, 5, 11

Aeshna grandis (Brown hawker) 1 (CWP), 5 (APF)

Libellula depressa (Broad-bodied chaser) 1 (CWP), 6

Sympetrum striolatum (Common darter) 1 (CWP), 8 (APF), 11

Sympetrum sanguineum (Ruddy darter) 1 (CWP & APF)

Order: Hemiptera-Heteroptera (bugs)

Hydrometra stagnorum 4, 10

Velia caprai 4

Microvelia reticulata 6

Gerris lacustris 1, 3, 4, 5, 7, 8, 11

Gerris odontogaster 5

Nepa cinerea 3, 4, 5, 7, 8, 9, 10

Ilyocoris cimicoides 1, 6, 7, 8

Notonecta glauca 1, 3, 4, 5, 8, 10

Notonecta marmorea viridis 8

Plea minutissima 9

Micronecta scholtzi 8

Cymatia coleoptrata 1,

Corixa punctata 5, 6

Hesperocorixa linnaei 1

Hesperocorixa sahlbergi 1, 3, 5, 7

Sigara dorsalis 1, 9, 11

Sigara falleni 8, 9

Sigara lateralis 5, 9

Sigara nigrolineata 5, 7

Table 3 Continued



Order: Megaloptera (alderflies)

Sialis lutaria 1, 4, 7, 8

Order: Coleoptera (beetles)

Gyrinus substriatus 2, 7

Haliplus lineatocollis 7, 10

Haliplus immaculatus 1 (DRN)

Haliplus ruficollis 1, 2, 3, 5, 6, 7, 8, 9

Noterus clavicornis 1, 6, 8, 9

Hydroglyphus pusillus 7

Hygrotus inaequalis 2, 6, 9

Hyphydrus ovatus 1, 4, 5, 6 (APF)

Hydroporus angustatus 5

Hydroporus discretus 1 (DRN), 4 (DRN)

Hydroporus incognitus 2

Hydroporus memnonius 4 (DRN), 6 (APF)

Hydroporus nigrita 6

Hydroporus palustris 1, 2, 4, 5, 6 (APF), 7

Hydroporus planus 4 (DRN), 6 (APF)

Hydroporus pubescens 4 (DRN)

Hydroporus tesselatus 7

Graptodytes granularis 2, 7

Suphrodytes dorsalis 2

Nebrioporus elegans 10

Agabus bipustulatus 4 (DRN), 5, 6 (APF), 7

Agabus chalconatus 4 (DRN)

Agabus didymus 4 (DRN)

Agabus guttatus 1 (DRN), 4 (DRN)

Agabus nebulosus 6

Agabus paludosus 4 (DRN)

Agabus sturmii 4, 5, 6

Ilybius ater 2

Ilybius fuliginosus 4, 7, 11

Rhantus suturalis 1 (DRN)

Colymbetes fuscus 5, 11

Laccophilus hyalinus 1 (DRN)

Acilius sulcatus 5

Dytiscus marginalis 6

Hydraena nigrita 4

Hydraena riparia 4, 7, 10

Ochthebius minimus 2, 5, 6, 7, 10

Helophorus grandis 4 (DRN)

Helophorus minutus 7

Helophorus obscurus 6

Anacaena bipustulata 8

Anacaena globulus 1 (DRN), 4, 10

Anacaena limbata 1, 2, 3, 4, 5, 6, 7, 8

Anacaena lutescens 2

Table 3 Continued



Laccobius bipunctatus 1, 5, 6, 8, 9

Laccobius striatulus 8

Laccobius sinuatus 10

Helochares lividus 8, 9, 10

Enochrus coarctatus 6

Enochrus testaceus 1, 6, 9

Hydrobius fuscipes 3, 5, 6, 10

Elodes sp. 4, 6, 7

Elmis aenea 7, 8, 10

Oulimnius tuberculatus 1, 7, 8, 10

Dryops sp. (larvae) 1, 6, 7, 10

Heterocerus fenestratus 4 (DRN)

Order: Lepidoptera (butterflies and moths)

Nymphula nympheata 8

Parapoynx stratiotata 11

Order: Trichoptera (caddisflies)

Agraylea sp. – empty cases only 11

Hydroptila sp. – empty cases only 10

Cyrnus flavidus 1, 8

Pseudolimnophila sp. 3

Hydropsyche angustipennis 10

Phryganea grandis 8

Limnephilus lunatus 4, 7, 8

Oecetis lacustris 8

Mystacides nigra 8

Mystacides longicornis 8

Order: Diptera (true flies)

Tipula pierrei 8

Tipula montium group 7, 10

Epiphragma lineola 1

Pilaria discicollis group 1

Ormosia sp. 1, 4, 6

Peripsychoda fusca 3, 4

Pericoma pulchra 1, 4, 5, 6, 8

Pericoma trivialis group 1, 3, 4, 9, 10

Chaoborus crystallinus 5, 6

Chaoborus flavicans 1, 3, 6

Anopheles claviger 1, 3, 4, 6, 7, 11

Culiseta annulata group 4, 5

Culex sp. 7

Dixella autumnalis 5, 6

Dixella amphibia 3

Anasimyia lineata 1 (CWP)

Chrysogaster chalybeata 1 (CWP)

Table 3 Continued



Chrysogaster solstitialis 1 (CWP)

Helophilus pendulus 1 (CWP)

Lejogaster metallina 1 (CWP)

Neoascia interrupta

Neoascia tenur 1 (CWP)

Atrichopogon sp. 10

Ptychoptera albimana 4

Ptychoptera scutellaris 5

Ptychoptera minuta 1, 3, 4, 6, 9

Tabanus sp. 1, 3, 4, 5, 9

Stratiomys potamida 1, 5, 9

Oplodontha viridula 1 (CWP), 3

Oxycera morrisii 10

Vanoyia tenuicornis 6

Nemotelus pantherinus 1 (CWP)

Ephydra sp. 1

Hydrellia sp. 1, 6, 7, 10, 11

Coremacera sp. 4

Tetanocera sp. 7

Limnophora riparia (Fallen) 10

An evaluation of conservation interests Twelve species (7·0% of the total) were found which are nationally scarce and believed to occur within 31–100 hectads of the national grid (Notable b) (Table 4), seven of which were water beetles. This table does not include Helochares lividus, a water beetle recently downgraded to Local status by Foster (2000). One of the species on the list, the soldier fly Oxycera morrisii was originally listed in RDB3 (Ball, 1986) as nationally rare, although it is now understood to be more widely distributed in streams and seepages across southern England and Notable status is more warranted.

In addition, 46 ‘Local’ species were found. These species are typically rather uncommon, such as those associated with particular habitats which are limited in their geographic occurrence, or tend to have very low abundances and so are not often encountered. Generally, a concentration of Local species often accompanies a strong list of Notable species at a high quality habitat type. The distinction between Local and Common species is not statutory. For some orders the ‘Local’ designation is particularly useful in identifying species which may warrant Regionally Notable status, and it is unfortunate that this designation has only been applied to a few well-worked areas, and not on a consistent basis. Table 5 summarises the number of species found at each site that are afforded Notable or Local status and gives the total conservation score.

Clearly, the Fairy Lake and the River Linnet (combined sites) were the most important at Ickworth, both for the number of species (Table 2) and the conservation score based on the number of scarce and local species (Table 5).

Table 3 Continued



Sta

tus

Sp

ecie

s S

ite/N

GR

/Da

te/R

eco

rd

er

Nota

ble

b

Ag

ab

us

cha

lco

na

tus

A w

ate

r b

eet

le

Str

eam

to F

air

y L

ak

e T

L8

26

0 1

9/5

/99

(D

RN

)

Nota

ble

b

Rh

an

tus

sutu

rali

s

A w

ate

r b

eet

le

Fair

y L

ak

e T

L8

18

60

4 5

/5/9

9 (

DR

N)

Nota

ble

b

Hyd

rog

lyp

hu

s p

usi

llu

s

A w

ate

r b

eet

le

R.L

inn

et,

Deer

Park

TL

80

66

13 6

/8/0

3 (

DJL

)

Nota

ble

b

Gra

pto

dyte

s gra

nula

ris

R

.Lin

net

, D

eer

Park

TL

80

66

13 6

/8/0

3 (

DJL

)

A

wate

r b

eet

le

Sed

ge

Pon

d N

E o

f F

air

y L

ak

e T

L8

22

60

7 1

7/9

/03

(S

W)

Nota

ble

b

Hyd

raen

a n

igri

ta

A w

ate

r b

eet

le

R.L

inn

et,

Fair

y L

ak

e ou

tfall

TL

81

66

05

6/8

/03

(D

JL)

Nota

ble

b

An

aca

en

a b

ipu

stu

lata

A w

ate

r b

eet

le

Th

e C

an

al

TL

81

06

09

6/8

/03

(D

JL)

Nota

ble

b

La

cco

biu

s si

nu

atu

s

A w

ate

r b

eet

le

R.L

inn

et,

nr

Mord

ab

oys

Cott

age

TL

81

26

29

6/8

/03

(D

JL)

Nota

ble

b

Sym

petr

um

san

gu

ineu

m

Ru

dd

y D

art

er d

ragon

fly

Fair

y L

ak

e T

L8

18

60

4 A

ug/2

00

3 (

CW

P)

Fair

y L

ak

e T

L8

18

60

4 1

7/9

/20

03

(A

PF

)

Nota

ble

b

Str

ati

om

ys

po

tam

ida

A s

old

ierf

ly

Fair

y L

ak

e T

L8

18

60

4 6

/8/0

3 (

DJL

)

Pars

on

s P

on

d T

L8

13

61

3 6

/8/0

3 (

DJL

)

Fair

y L

ak

e T

L8

18

60

4 A

ug/2

00

3 (

CW

P)

Nota

ble

Oxyce

ra m

orr

isii

A s

old

ierf

ly

R.L

inn

et,

nr

Mord

ab

oys

Cott

age

TL

81

26

29

6/8

/03

(D

JL)

Nota

ble

Va

no

yia

ten

uic

orn

is

A s

old

ierf

ly

Go

lden

Pon

d T

L8

09

61

2 6

/8/0

3 (

DJL

)

Nota

ble

b

Neo

asc

ia i

nte

rru

pta

A h

over

fly

Fair

y L

ak

e T

L8

18

60

4 A

ug/2

00

3 (

CW

P)

Ta

ble

4 L

ist

of

Na

tion

all

y S

carc

e (N

ota

ble

) A

qu

ati

c S

pec

ies

reco

rd

ed a

t Ic

kw

ort

h P

ark

1999

–20

03

(Rec

ord

ers:

DR

N =

Dav

id N

ash,

DJL

= D

avid

Lee

min

g,

CW

P =

Coli

n P

lan

t, S

W =

Stu

art

War

rin

gto

n,

AP

F =

An

dy

Fost

er)



Table 5 The number of Aquatic Species at each site afforded Notable or Local status and the total conservation score obtained

Site number: 1 2 3 4,7,10 5 6 8 9 11 all

Local species 19 2 2 18 4 11 12 8 3 46

Notable species 4 1 0 6 1 1 1 1 0 12

Conservation score 350 60 20 420 80 150 160 120 30 940

F

air

y L

ak

e

S

edg

e P

on

d N

E o

f F

air

y L

ak

e

F

on

tain

eble

au

Wo

od

Pon

d

R

iver

Lin

net

: a

ll s

ites

S

edg

e P

on

d S

of

Fair

y L

ak

e

G

old

en P

on

d

T

he

Can

al

P

ars

on

s P

on

d

D

air

y H

ou

se P

on

d

I

ckw

ort

h P

ark

: a

ll d

ata

Site Comparisons 1. The Fairy Lake The Fairy Lake is an attractive, well-vegetated waterbody containing areas of contrasting habitats, extending to about 2 hectares overall. To the east of a small wooded island the basin is shallow and contains a large area of reedmarsh (Phragmites australis) which grades around the edges into tall rank terrestrial herbs and shrubs. To the west of the island the lake basin is more aquatic, with the surrounding edges occupied by dense emergent vegetation, comprising mostly sedges and reedmace rooting in water depths to about 40 cm. This swamp and fen zone also contains areas of meadowsweet, hemp agrimony, gypsywort and water mint, but is undoubtedly more diverse in species than this cursory list suggests. Beyond this encroaching front, the central basin is almost entirely covered by an impressive expanse of the floating leaves of the yellow water lily rooting in deep silt. Amongst the lilies, the water depth ranges from 60 cm to perhaps as much as 150 cm or more, and the water column also contains submerged vegetation including water milfoil, ivy-leaved duckweed and fine-leaved pondweeds.

Nature of fauna and key Invertebrate species: The species list contains a fairly rich assemblage of standing water species characteristic of well vegetated, eutrophic standing waters and a small element of species more typical of running-water, such as the riffle beetle Oulimnius tuberculatus, reflecting connections to the River Linnet. Scarce and local species only found here include the water beetles Rhantus suturalis and Laccophilus hyalinus, the Ruddy darter Sympetrum sanguineum and many flies such as the Notable B hoverfly Neoascia interrupta. There was also a rich community of 9 dragonfly species present.



2. Sedge Pond N.E. of Fairy Lake (in Paddock Wood) This pond is located in a peaty hollow in the woodland, with some bulrush and tussock sedge. At the time of the survey the pond had retreated to a small patch, hard to safely access and only water beetles were identified. In spring, it was apparent that a much larger area would be covered in water.

Nature of fauna and key Invertebrate species: The site was evidently of importance for supporting the Notable b water beetle Graptodytes granularis and three other beetle species Suphrodytes dorsalis, Ilybius ater and Hydroporus incognitus that were not recorded elsewhere within Ickworth Park.

3. Fontainebleau Grove Pond This woodland pond has an irregular shape and basin, with islands populated by trees and shrubs, and deep “holes” extending to 120 cm, whilst it is typically around 30 cm deep. The bed is firm clay and largely devoid of aquatic vegetation. There are a couple of significant clumps of sedge towards the centre of the pond around one of the islands, and small patches of fine-leaved submerged plants were also found. The pond contained much coarse woody debris, including the fallen limbs of trees, which can provide habitat for particular invertebrates and amphibia.

Nature of fauna and key Invertebrate species: A depauperate standing water assemblage was found at this site which produced the lowest taxon richness of all eleven samples collected. Water beetles and bugs were poorly represented here and snails absent apart from the lake limpet Acroloxus lacustris. The only noteworthy species found were the hog louse Asellus meridianus, the meniscus midge Dixella amphibia and the local soldierfly fly Oplodontha viridula.

4, 7 and 10. The River Linnet (all sites). David Nash sampled the River Linnet just upstream of Fairy Lake in 1999. This section was not visited during the present survey. In August 2003, below the Fairy Lake outfall only a small section of the stream held water ponded above a footbridge, with no perceptible flow. The stream was dry below this point as far as the Canal about 600 m distant. The stream width averaged 1·2 m (maximum 1·5 m) and water depth averaged 8 cm (maximum 10 cm), with semi-natural earth banks. The substrate was 100% silt. A variety of emergent plants including water plantain, gypsywort, water mint, unbranched burr reed, horsetail and canary grass provided useful habitat rooting in-channel, others such as bittersweet and hemp agrimony grew at the margins or rooted on the banks.

The river was next sampled approximately 1km downstream within the Deer Park in a reach of the Linnet between the outfall from the Canal and the point where a flowing tributary joins from the left bank. In Aug. 2003 this length the River Linnet was predominantly dry, with only localised areas of standing water less than a metre or so wide remaining. These pools were sampled throughout and included puddles of very shallow open water over mud at a ford, and deeper water (to about 15 cm) with grassy edges or amongst emergent plants. The emergent plants noted in this section included



water mint, unbranched burr reed, canary grass, sweet flag, fools water cress, soft, hard and spiked rushes and non-aquatic herbs. The presence of recently eroded banks (“river cliffs”) demonstrated that the section has been subjected to periodic spate flows and it is likely that perennial flows may exist here during most years.

Below the tributary stream the River Linnet held flowing water throughout the remainder of its course within the estate. This reach was sampled at a site located above the roadbridge near Mordaboys Cottage. At this point the water width averaged 1·5 m (range 1 to 2 m) and averaged about 5 cm deep (range 2 to 15 cm), with a gravel-dominated bed and mud edges largely obscured by growths of filamentous algae (approx 50% coverage). Waterlogged grassy edges and shallow water over mud provided useful invertebrate habitat, whilst the presence of slow flowing water over a gravel substrate was unique amongst the sites sampled in the estate.

Nature of fauna and key Invertebrate species: Collectively, the River Linnet sites were very important and rich aquatic invertebrate habitats. Several water beetle species obtained by David Nash from the headwaters of the River Linnet upstream of the Fairy Lake were not known elsewhere within the estate, namely Agabus guttatus, A. chalconatus and Hydroporus discretus. David Nash also recorded Agabus didymus and A. paludosus which are common species of small perennial streams. These species may be reasonably expected to occur throughout the River Linnet at Ickworth and their absence during August 2003 is likely to be a consequence of the low flows observed. The occurrence of a single larva of the demoiselle damselfly Calopteryx splendens at the Deer Park site is also noteworthy since this species is typically confined in its distribution to permanent flowing streams and a population of this insect in this drying reach is likely to be an artefact of past flow conditions. This population will be vulnerable to sustained low flows or complete channel drying.

During 2003 the Deer Park section of the Linnet contained many ditch species and a good assemblage of water beetles in particular, including species of high conservation interest such as Graptodytes granularis and Hydroglyphus pusillus. Hydroglyphus is a mobile species often associated with recently created waters, utilising habitats such as flooded grass or mud. Graptodytes typically occurs in rich fen conditions, or inundated grass. Their occurrence within this reach could reflect colonisation from local sources within the estate, including any pockets of fen or wet grassy hollows which dried completely during 2003, or they may have well established populations in this reach.

Sites on the River Linnet also produced several noteworthy stream-edge scavenger beetles not found in the standing waters, for example Hydraena riparia, Hydraena nigrita and Laccobius sinuatus. Most flow-dependent invertebrates in the River Linnet were confined in their distribution to the site near Mordaboys Cottage. Examples include the mayflies Baetis rhodani, B. vernus, and Centroptilum luteolum, the caddisfly Hydropsyche angustipennis and fish such as the stone loach. Whilst there was some evidence of a deterioration in water quality at this lower site, as shown by growths of filamentous algae, the species assemblage was still fairly rich.



5. Sedge Pond south of Fairy Lake The pond comprised a small well-defined area of open water (dimensions approx 20 m × 20 m) to the east of a larger area of shallow water densely vegetated by sedges which grades to damp ground conditions towards the western edge of the basin. Within the open water the depth averaged about 20 cm and extended to 40 cm near an overhanging tree. The bed comprised deep, soft, anaerobic black silt overlain by a layer of decomposing vegetation.

Nature of fauna and key Invertebrate species: Perhaps as a consequence of past drying-out or its’ isolated location surrounded by woodland, the pond contained a relatively limited diversity of molluscs – lacking several ubiquitous families of pond snails (eg. Lymnaeidae), and pea mussels (Sphaeriidae). Other groups were strongly represented, particular aquatic bugs (Hemiptera) and water beetles (Coleoptera), with a number of species found here that were scarce or absent from other sites in the present survey, such as Hydroporus angustatus, Acilius sulcatus and Gerris odontogaster.

6. Golden Pond Golden pond is a narrow rectangular pond (dimensions approx 70 m × 10 m), unusually situated on a steep south-facing slope and with earth banks on one side, and was perhaps created by the damming of a small spring. The land immediately surrounding the pond basin is grazed, unimproved grassland which appears botanically-rich. The open water is relatively deep (to >1 m), underlain by deep soft silts. The water column is densely-vegetated with water violet (an uncommon and noteworthy species), duckweed and ivy-leaved duckweed. The edges of the basin are undergoing encroachment by treacherous floating mats of a variety of emergent species, including fools’ water cress, marestail, marsh fleabane, unbranched bur-reed, gypsywort, hemp agrimony, water mint, creeping cinquefoil and the semi aquatic grass Glyceria declinata.

Nature of fauna and Key Invertebrate species: Well developed eutrophic pond fauna with a component of water beetle and bug species not found elsewhere in the survey. Examples include the water bug Microvelia reticulata, beetles Agabus nebulosus, Helophorus obscurus, Enochrus testaceus, Hydroporus nigrita and the Notable soldier fly Vanoyia tenuicornis. A conspicuous element of the fauna of this site were the large numbers of the water bug Ilyocoris cimicoides and the beetles Noterus clavicornis and Elodes sp (larvae) that were collected here. Overall 21 species of water beetle were found, the most for any one site.

8. The Canal The Canal is a relatively large on-line lake with dimensions of about 200 m × 50 m (about 1 hectare) created by damming of the River Linnet 600 m downstream from Fairy Lake. The lake contains a high proportion of open-water, with some extensive areas of floating-leaved yellow water lily. Sampling of the waterbody was undertaken from the south bank close to the River Linnet outfall at the western end. Throughout this part of the lake, the bed contains extensive shallow water (<40 cm) over a sand bed which extends at least 10 m from the bank. Beyond this zone lies deeper silt. Water depth



appears to reach about 120 cm towards the centre at this end of the basin. The south and west banks are managed and possess a steep, but low profile with an abrupt bank-water interface and limited coverage by emergent plants. Emergent plants noted included: unbranched burr reed, yellow flag iris, sweet flag, hairy willowherb, water mint, gypsywort, reedmace, hemp agrimony, hard rush and marestail. Well developed stands of emergent vegetation or poached margins were absent from the sampled area, although the north bank (not accessed) appears to contain a fairly continuous vegetated margin worthy of future attention.

Nature of fauna and key Invertebrate species: The fauna of the Canal contained elements associated with large well-oxygenated standing water that were not found elsewhere at Ickworth. These include the bug Micronecta scholtzi, the mayfly Caenis horaria and the caddisflies Oecetis lacustris, Mystacides longicornis, M. nigra and Phryganea grandis. The caseless caddisfly Cyrnus flavidus was also particularly abundant here, but a single specimen was also found at Fairy Lake. The common riffle beetles Oulimnius tuberculatus and Elmis aenea are occasionally found in on-line lakes and were also present in the Canal, the latter occurring in quite large numbers in the sandy areas. These are an example of the element of species shared between both on-line lakes and the River Linnet, as a consequence of their connectivity. Invertebrate groups associated with emergent vegetation and swamp-edge habitats (many water beetles and bugs for example) were probably under recorded at The Canal. Nevertheless, the single sample collected here was fairly species rich and there were many Local species. The full importance of this site may warrant further investigation.

9. Parsons Pond Parsons pond is a small circular waterbody with a diameter of about 20 m, overhung at one point by a weeping willow. The depth of the pond could not be estimated as the water column was very turbid and there was deep silt. About a third of the circumference contained a narrow (1–1·5 m wide) marginal fringe of unbranched bur-reed, with small patches of water mint and hard rush. Due to the low water level at the time of survey, much of the marginal vegetation was stranded above the waterline, and elsewhere around the pond were drawn-down edges which revealed a blackened anoxic bed with much organic debris. No submerged plants were seen apart from a small patch of the floating-leaved fringing water lily (Nymphoides peltata). This attractive native species is frequently introduced to waterbodies and is uncommon in the wild. Some fish activity was observed.

Nature of fauna and key Invertebrate species: The pond supported a moderate fauna fairly typical of a small, open, eutrophic pond. Classic small pond species such as the water bug Plea minutissima and leech Erpobdella testacea were not found elsewhere, whilst the ramshorn Planorbis carinatus and leech Hemiclepsis marginata also have a restricted distribution within Ickworth Park. The Notable soldierfly Stratiomys potamida was also found.



11. Dairy House Pond Square, formal brick-edged pond dimensions approx 30 m × 30 m. Held a shallow lens of water mostly 15–25 cm deep reflecting low water levels at time of visit. Water column densely vegetated, principally by hornwort (~80% area coverage) and water milfoil (~20% cover). These submerged plants were also overlain or smothered by blanket weeds (~ 60% area coverage) and were found to be stranded by receding water levels in some parts. Only very small patches of emergent plants were present. Considerable fish activity was witnessed with shoals of small Rudd.

Nature of fauna and key Invertebrate species: Restricted pond fauna with some elements characteristic of densely vegetated eutrophic ponds, but the overall list is limited due to shortage of edge habitats and emergent vegetation. Nevertheless, this site produced specimens of the large ear snail Lymnaea auricularia, the pyralid moth Parapoynx stratiotata, and the rather local leech Hemiclepsis marginata which are species of some interest that were either not found elsewhere or were found at only one other site in the case of Hemiclepsis.

Discussion The present and other recent survey work produced a list of 172 aquatic macro-invertebrate species for Ickworth Park of which 7·0% were nationally scarce. This figure of compares favourably with similar survey work undertaken at other sites. For example, at Richmond Park, London during August 2001, 177 taxa were recorded from 21 samples collected from a variety of ponds, lakes and a small stream, with 5·6% nationally scarce (Leeming, 2001). The ponds, lake and stream within the National Trust’s Hatfield Forest NNR produced 115 aquatic species, of which 6·1% were nationally scarce (excluding the Diptera with aquatic larvae) (Warrington et al, 2004). The numbers of species recorded during a survey of the National Trust’s Wimpole Hall estate between April and July 2000 (Kirby, 2001) were much greater than at Ickworth Park, with 310 aquatic species of which 9·6% were nationally scarce or rarer (and 652 ‘wetland’ species recorded overall). The higher total for Wimpole reflected repeat sampling of waterbodies, use of a wider variety of traps and probably the wider variety of wetland habitats present.

With regard to the ‘conservation score’ of 940 for Ickworth, using this measure the large wetland of the Inner Thames Marshes SSSI produced a score in excess of 1000 pts from a season of repeat sampling (Leeming, 1998), whilst Richmond Park generated a score of around 500 (Leeming, 2001). Scores of 150–300 are typical for important individual sample sites, which shows the high value of the Fairy Lake.

Direct comparison of the number of species found by aquatic invertebrate surveys can be potentially misleading unless sampling methodology and effort are standardised and broadly comparable. Sampling effort may vary in relation to the duration of sampling undertaken in each waterbody, the number of repeat collections made and the seasons. Repeat collections made during spring, summer and autumn provide the most comprehensive account of the species present at a site.



This survey revealed that the Ickworth Park estate supports a species-rich complement of aquatic species, including taxa characteristic of both running and standing waters. An important finding was that each water body sampled contributed to the overall biodiversity, as almost every one had species unique to that site. Further sampling and consideration of additional areas of ephemeral or transient habitat that were dry during August 2003 may be expected to increase the list of species known within the estate.

References Ball, S. G. (1986). Terrestrial and Freshwater Invertebrates with Red Data

Book, Notable or Habitat Indicator Status, Invertebrate Site Register Report No. 66, Nature Conservancy Council, Peterborough.

Foster, G. N. (2000). A review of the scarce and threatened Coleoptera of Great Britain: Part 3: Aquatic Coleoptera. Species Status, No.1, Joint Nature Conservation Committee, Peterborough.

Furse, M. T., Wright, J. F., Armitage, P. D., & Moss, D. (1981). An appraisal of pond-net samples for biological monitoring of lotic macro-invertebrates, Water Research, 15, 679–689.

Kirby, P. (2001). Wimpole Hall. Wetland invertebrate survey 2000. Unpublished Report to the National Trust.

Leeming, D. J. (1998). Aquatic macroinvertebrate survey of drainage ditches and standing waters within the Inner Thames Marshes SSSI, Essex. Unpublished Report, Environment Agency (Thames Region), Hatfield.

Leeming, D. J. (2001). Aquatic invertebrate survey of ponds within Richmond Park, London. Unpublished report for Land Use Consultants Ltd, London, on behalf of the Royal Parks.

Warrington, S., Davis, G. & Wallington, A. (2004). The aquatic invertebrate community of Hatfield Forest National Nature Reserve. Entomologist’s Monthly Magazine 140: 89–96.

Dr Stuart Warrington Regional Nature Conservation Advisor, East of England The National Trust The Dairy House Ickworth Bury St. Edmunds IP29 5QE Email: [email protected]

David Leeming 45 West End Ashwell Herts. SG7 5Q7

an aquatic invertebrate survey of ickworth park, suffolk

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