advantage of this with increasing populations (mesotrophic). There is some sediment accumulation.
With more time, nutrients may become very concentrated and the lake eutrophic. The lake begins to
fill in and marshes encroach on the open waters and finally the lake changes to a wetland. There exist
reservoirs less than 100 years old that have converted to woodlands. In contrast many glacial lakes
have existed for thousands of years without completing this process.
1.2.9 BIOTA: MAJOR COMPONENTS IN LAKES
A rich terminology has been constructed for describing phylogenetic, spatial and functional
categories of biota in lakes. Some of the terms are arcane and seldom encountered, others are
commonly encountered and usually taken for granted by limnologists.
Lake organisms perform the same functions as organisms in any other ecosystem. Their special
adaptations enable them to inhabit the specialized environments found in many lakes. For most
purposes, they include plants, animals, and diverse microbes. Spatially, organisms inhabit the surface,
the lake bottom, and either float or swim in the lake.
Among all organisms there is one great biological distinction that makes some of the following
groups difficult to organize. All organisms are either eucaryotic (having complex cell organization) or
procaryotic (having simple cell organization). All bacteria are procaryotic. All multicellular organisms
are eucaryotic. Cyanobacteria, otherwise known as blue-green algae are procaryotic. All of the fungi
and protozoans are eucaryotic. People are eucaryotic.
Now the terms...
A. Macrophytes - large vascular plants, can be observed without microscope.
1. Endemics - native to region, Valisneria, Ceratophyllum
2. Exotics - introduced to area from other places. Hydrilla, Eurasian watermilfoil
3. Pleuston - plants which float on the surface and penetrate into the water.
B. Microscopic plants - algae, unicellular and eucaryotic
1. Phytoplankton - microscopic plants subject to water movements. Reservoirs
are dominated by green algae, diatoms, and dinoflagellates (also cyanobacteria)
2. Neuston, etc. - organisms associated with the surface film of the water.
3. Aufwuchs - attached organisms, often called periphyton.
Specialized terms according to type of surface, epiphytes on plants, epilithon on
rocks, epipsammon on muds and sediments, psammon living interstitially in the
sediments. Aufwuchs also contains animals and microbes.