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Algae and Microinvertebrates Habitat & 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 Lentic Zones Lotic Environments Lotic Environments Community Descriptions • Neuston – organisms floating in surface film of water • Pleuston – organisms living at thin airwater 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 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 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 Algae • Heterocysts fix N2 from atmosphere Cyanobacteria Green 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 Algae Notes: – Cell walls of cellulose and nuclear membrane present – May possess 2 or 4 flagella Green 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 Algae • Notes: – Some are good indicators of either nutrient rich (Cladophora spp.) or poor (Desmidae) environments Spirogyra (Genus of Green Algae) Euglenoids • Phylum Euglenophyta – Habitat: freshwater – Notes: • Mostly unicellular with 1-3 flagella • Nuclear membrane but no cell walls Euglenoids Notes: • Found mostly in still water • Can be auto- or heterotrophic • Abundance of heterotrophic forms may be indicative of pollution Euglena Phylum Heterokontophyta • Algae having chlorophyll a and usually c, and flagella of unequal lengths • Classes – Xanthophyceae (yellow-green algae) – Chrysophyceae (golden algae) – Bacillariophyceae (diatoms) – Phaeophyceae (brown algae) Yellow-Green Algae • Class Xanthophyceae – Habitat: Primarily in freshwater, but some marine. – Abundance: Not abundant – Notes: Contains chlorophyll c (NO chlpyll b) Golden 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) Diatoms • – 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 Centrales • Characterized by centric and often circular form • Note also the numerous punctae (pores) Diatoms: Order Pennales • Usually elongate • Characterized by numerous striae (grooves) that may run both parallel and perpendicular to the axis of the organism Diatoms Gyrosigma obtusatum Pleurosira laevis Nitzschia levidensis Brown 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 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 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 Algae Notes: • In MI, found in bogs/attached to logs in streams—can be locally common Dinoflagellates • Phylum Pyrrhophyta “Whirling flagella” – Habitat: Mostly marine, some freshwater – Notes: • Unicellular protists • 2 dissimilar flagella • Many are photosynthetic Dinoflagellates Notes: • Heterotrophic dinoflag feed on diatoms or other protists • Marine “blooms” – Red tides Rotifers • Phylum Rotifera “Rotating wheel” – Habitat: Fresh water – Notes: • Heterotrophic • Corona of cilia provide movement and means to move food toward the mouth. Rotifers Notes: • Sessile, anchors itself with foot • May enter dormancy and form cyst when env. conditions unfavorable – Cysts last up to 50 years Bryozoa • 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 Bryozoa Cladocera • 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 Cladocera • Notes – Parthenogenetic: • most eggs are diploid females (asexual repro) • occasional diploid males fertilize haploid eggs produced by females for sexual reproduction Copepods • 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 immature copepods before reaching maturity – Characterized by conspicuous 1st pair of antennae and single anterior eye 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 End