Algae and MicroinvertebratesAlgae and MicroinvertebratesENV 311 / EEB 320

Winter 2007

Habitat & CommunitiesHabitat & Communities

Phytoplankton

• Phytoplankton – microscopic plants and some types of bacteria which obtain their energy via photosynthesis.

• Important to the ecosystem because – Part of the primary producing community– Assist in recycling elements such as carbon

and sulfur which are required elsewhere in the community.

Phytoplankton• Basis for aquatic food chain b/c major primary

producers• Huge impact on global primary production

– Estimated at 105 – 106 g C/year

• More abundant in well-lighted areas with higher temperatures

• Relatively unspecialized physiology, but are evolved to maintain buoyancy

• Very little competitive exclusion• May be unicellular or multicellular

Phytoplankton• Asexual reproduction keep numbers high

– Cyanobacteria can double several times/day– Diatoms are slower, but can double every 1-2

weeks

Phytoplankton

• Phylogenetically diverse

• Important groups:– cyanobacteria– dinoflagellates– euglenoids– green algae– diatoms

Cyanobacteria

Dinoflagellates

Euglena

Diatoms

Pleurosira laevis

Nitzschia levidensis

Gyrosigma obtusatum

Spirogyra(Genus of Green Algae)

Lentic Zones

Lotic Environments

Lotic Environments

Community Descriptions

• Neuston – organisms floating in surface film of water

• Pleuston – organisms living at thin air-water interface (bodies project into air)

• Periphyton – organisms living attached underwater surfaces

Periphyton

• Sessile organisms, such as algae and small crustaceans, that live attached to surfaces projecting from the bottom of a freshwater aquatic environment.

• Major groups include:– cyanobacteria– diatoms– filamentous green algae

Algae and MicroinvertsAlgae and Microinverts

• Cyanophyta• Chlorophyta• Euglenophyta• Heterokontophyta

– Xanthophyceae– Chrysophyceae– Bacillariophyceae– Phaeophyceae– Oomycetes

• Rhodophyta• Pyrrhophyta

• Rotifera • Ectoprocta/Bryozoa• Arthropoda

– Crustacea (superclass)• Cladocera (suborder)• Copepoda (order)

– Chelicerata (subphylum)• Arachnida (superclass)

– Acari (order)

Blue-Green AlgaeBlue-Green Algae• Phylum Cyanophyta

• Habitat: widespread in marine and fresh water

• Notes:– Prokaryotic; no nuclear

membrane or organelles

– Lacks cellulose cell walls and flagella

– Uses chlorophyll A, biliproteins, and carotenoids

– May be colonial, filamentous, unicellular

– Moves by extruding mucus

Blue-Green AlgaeBlue-Green Algae

• Heterocysts fix N2 from atmosphere

Green AlgaeGreen Algae

• Phylum Chlorophyta• Habitat: widespread

in marine and fresh water

• Notes:– Very diverse group,

hard to generalize about their ecology

– May be unicellular, filamentous or colonial

Green AlgaeGreen AlgaeNotes:

– Cell walls of cellulose and nuclear membrane present

– May possess 2 or 4 flagella

Green AlgaeGreen Algae

• Notes:– Utilize cholorphyll A/B

and carotenoids– Store energy as starch– Some forms are large

(e.g. Chara spp.) and at first glance resemble a higher plant

Green AlgaeGreen Algae

• Notes:– Some are good

indicators of either nutrient rich (Cladophora spp.) or poor (Desmidae) environments

EuglenoidsEuglenoids

• Phylum EuglenophytaPhylum Euglenophyta– Habitat: freshwater– Notes:

• Mostly unicellular with 1-3 flagella

• Nuclear membrane but no cell walls

EuglenoidsEuglenoids

Notes:• Found mostly in still water

• Can be auto- or heterotrophic

• Abundance of heterotrophic forms may be indicative of pollution

Phylum HeterokontophytaPhylum Heterokontophyta

• Algae having chlorophyll a and usually c, and flagella of unequal lengths

• Classes– Xanthophyceae– Chrysophyceae– Bacillariophyceae– Phaeophyceae

Yellow-Green AlgaeYellow-Green Algae

• Class Xanthophyceae– Habitat: Primarily in

freshwater, but some marine.

– Abundance: Not abundant

– Notes: Contains chlorophyll c (NO chlpyll b)

Golden AlgaeGolden Algae

• Class Chrysophyceae– Habitat: fresh water– Notes:

• With or without chloroplasts; chloroplast yellowish green or yellowish brown due to a large amount of beta carotin and xanthophyll, also contains chlorophyll a and c

• Facultative heterotrophs (in the absence of light)

DiatomsDiatoms

• – Habitat: Marine &

freshwater– Notes:

• ~20-25% of all organic carbon fixation carried out by diatoms

• Single celled• Produces a frustule

made of silica.– Bilateral symmetry

– Radial symmetry

Diatoms: Order CentralesDiatoms: Order Centrales

• Characterized by centric and often circular form

• Note also the numerous punctae (pores)

Diatoms: Order PennalesDiatoms: Order Pennales

• Usually elongate• Characterized by

numerous striae (grooves) that may run both parallel and perpendicular to the axis of the organism

Brown AlgaeBrown Algae

• Class Phaeophyceae– Habitat: mostly marine

and littoral eukaryotic algae

– Notes:• Some of the kelps can

grow to enormous sizes, forming “kelp forests,” and hosting a unique fauna

• Multicellular• Contains slimy

mucilaginous materials

Water MoldsWater Molds

• Class Oomycota “Egg fungus”

– Habitat: Freshwater– Notes:

• Does not contain chlorophyll

• Are heterotrophic• Produces gametes• Cell wall composed of a

mix of cellulosic compounds

• Nuclei are diploid (not haploid as in fungi)

End Phylum Heterokontophyta

Red AlgaeRed Algae• Phylum Rhodophyta

– Habitat: primarily marine but some fw

– Notes: • Uses Chlor A/D,

carotenoids and biliproteins

• No flagellated life stage• Able to photosynthesize

at very low light levels and wide range of the spectrum

Red AlgaeRed AlgaeNotes:

• In MI, found in bogs/attached to logs in streams—can be locally common

DinoflagellatesDinoflagellates

• Phylum Pyrrhophyta“Whirling flagella”

– Habitat: Mostly marine, some freshwater

– Notes:• Unicellular protists• 2 dissimilar flagella• Many are

photosynthetic

DinoflagellatesDinoflagellates

Notes:• Heterotrophic dinoflag

feed on diatoms or other protists

• Marine “blooms”– Red tides

RotifersRotifers• Phylum Rotifera

“Rotating wheel”

– Habitat: Fresh water– Notes:

• Heterotrophic• Corona of cilia provide

movement and means to move food toward the mouth.

RotifersRotifers

Notes:• Sessile, anchors itself

with foot• May enter dormancy and

form cyst when env. conditions unfavorable

– Cysts last up to 50 years

BryozoaBryozoa

• Phylum Ectoprocta(=Bryozoa)

• “Moss animals”– Habitat: Marine and both

lotic/lentic freshwaters– Notes:

• Sessile; can be epiphytic, epilithic or epidendric

• Colonial; a number of clones inhabit one structure

• Extend ciliated tentacles to filter food from water

• Often host a number of smaller organisms

BryozoaBryozoa

CladoceraCladocera

• Phylum Arthropoda, Superclass Crustacea, Suborder Cladocera

• Water fleas or Daphnia• Habitat: widespread; very

important in lentic habitats• Notes:

– Uses antennae to swim– Many populations react to

diurnal cycles, making vertical migrations each day

– May be predacious or herbivorous

– Head varies considerably from rounded to hooded but eye spot is always distinctive

– Body laterally compressed

CladoceraCladocera

• Notes– Parthenogenetic:

• most eggs are diploid females (asexual repro)

• occasional diploid males fertilize haploid eggs produced by females for sexual reproduction

CopepodsCopepods

• Phylum Arthropoda, Superclass Crustacea, Order Copepoda

• Habitat: widespread in marine and fw; may be benthic or pelagic

• Notes:– may be parasitic, predacious

or detrivorous– often seen carrying egg sacs

on both sides– develop through several

stages as nauplii before reaching maturity

– Characterized by conspicuous 1st pair of antennae and single anterior eye

Acari (Water Mites)Acari (Water Mites)

• Phylum Arthropoda,Subphylum Chelicerata, Superclass Arachnida, Order Acari

• Habitat: most abundant in lotic waters

• Notes:– Have 6 legs when young, 8

when mature– Many are parasitic but a

few are predaceous– Possess no antennae– Related to terrestrial

spiders

The EndThe End

Phylum Cnidaria/CoelentariaPhylum Cnidaria/Coelentaria

• Corals, hydroids, sea anemones, & jellyfish– Habitat: Marine,

freshwater (Hydra)– Notes:

• Radial symmetry• Nematocysts• Two staged life cycle

– Polyp (“juvenile”)– Medusa (“adult”)

• Symbiosis w/plants in corals.

Phylum Cnidaria/CoelentariaPhylum Cnidaria/Coelentaria

Notes:• Freshwater

ecosystems: Hydra