Lake Biota Classification by trophic level Classification by zonation Factors affecting the distribution of aquatic organisms Characteristic organisms for each lake zone

Classification by Trophic Level Primary Producers Produce organic material from elemental nutrients Ex: photosynthesis where light is used as an energy source chemosynthesis where a chemical reaction is used as an energy source Add reactions?

Consumers Decomposers Feed on primary producers or other consumers Ex: zooplankton, fish, people Decomposers Convert organic material back to nutrients, e.g. mineralization Ex: bacteria, fungi

Classification by Zonation Psammolittoral zone In the beach sand Ex: specialized copepods, rotifers, nematodes Limnetic, Pelagic zone In the water Ex: phytoplankton, zooplankton, fish

Benthic zone On the bottom Epifauna – those that live and move about on the lake bottom ex: crayfish, dragonfly larvae Infauna – those that live beneath the mud surface ex: nematodes, some insect larvae

Factors Affecting the Distribution of Aquatic Organisms General principles Leibig’s “Law of the Minimum” Shelford’s “Law of Tolerance” eurothermal – withstands a large temperature range, ex: carp stenothermal- only withstands a small temperature range

Stratification Light temperature ex: refuge for daphnia chemical ex: oxygen distribution, only certain organisms can withstand anoxia Light photic zone – need light for photosynthesis photoinhibition – high levels of light, especially in the UV range, inhibits photosynthesis

Nature of the substrate interstitial space – minimum space requirements erodability ex: macrophyte rooting Water movement gas and nutrient supply/replenishment transports organisms ex: build of up of algae downwind

Availability of nutrients and/or prey ex: zooplankton migrations to graze in shallow zones ex: blue-green algae sink to deeper, nutrient-rich water at night than float to the surface during the day for light Species interactions physical avoidance of predators competition for nutrients, prey, and light

Characteristic Organisms for Each Lake Zone Limnetic zone Plankton Phytoplankton – plant plankton Major Groups: Cyanophyta – Blue-green algae Chrysophyta – Golden-yellow algae Dinophyta – Dinoflagellates Euglenophyta – Euglena Chlorophyta – Green algae Bacillariophyta – Diatoms Cryptophyta - Cryptomonads

Diatoms

zooplankton – animal plankton Major Groups: Copepoda – Copepods Diaptomus Cladocerans e.g. Bosmina, Daphnia, Rotifers

Copepods

Bosmina

Daphnia

Nekton – swimmers Vertebrates fish

Invertebrates mysis shrimp

Littoral Zone Plants Aquatic macrophytes emergent plants cattails rooted plants with floating leaves lily pads submerged vegetation Eurasian milfoil

Giant Water Lilies: Victoria amazonica

Eurasian Milfoil at Tahoe

Algae – attached and free Major groups: Bacillariophyta - diatoms Chlorophyta – green algae Filamentous green algae (pond scum) Spirogyra, which are often attached Oedogonium Cynanophyta - blue-green algae

Spirogyra, sp.

Attached Periphyton at Tahoe

Periphyton – attached algae “aufwuches” Epilithic periphyton Epipelic periphyton Epiphytic periphyton Epizoic periphyton defined by the zone where they are found

Animals Invertebrates: snails (gastropods) and mussels (Bivalve mollusks) damsel, mayfly, and dragonfly nymphs rotifers flatworms hydra midges crayfish (crustaceans) isopods copepods cladocerans

Various Macroinvertebrates

Burrowing organisms (infauna) clams annelids snails chironomids Nekton fish diving beetles (insects) Vertebrates frogs, toads salamanders turtles water snakes

Profundal zone Pleuston Bacteria and fungi are the major components Blood worms (chironomid larvae) Clams Chaoborus (phantom larvae) Pleuston moved by the wind floating on the surface

Neuston Epineuston attached to the top of the surface Hyponeuston attached to the bottom of the surface