Lake Communities
Authors: Kosten Sarian , Meerhoff Mariana 
Published: November 2014

Abstract

As in all other ecosystems, lake community structure is determined by processes at different spatial and temporal scales, including biogeographical, regional and local environmental conditions, speciation, and local biotic interactions such as competition and predation. Lakes are commonly classified according to: (1) productivity (e.g. oligotrophic versus eutrophic), (2) where the major carbon input comes from or (3) thermal stratification patterns and morphometry. Most lakes worldwide are shallow and small. Within lakes we distinguish three different zones or habitats: the near‐shore littoral zone, the open‐water pelagic zone and the lake bottom or benthic zone. Each of these zones has a characteristic biological community, although they interact in different ways. The relative importance of each community to the whole ecosystem functioning varies with lake morphometry and productivity. Different anthropogenic activities influence lake communities at a local or regional scale; global changes such as climate change, however, represent a new threat to lakes worldwide.

Key Concepts:

Lake communities are influenced not only by contemporary circumstances – such as nutrient loading – but by historical processes as well – example, how and when the lake was formed.

Factors that shape lake communities also act on different scales, ranging from within the lake – example, fish presence or absence – to regional patterns – example, regional species pool.

Catchment characteristics shape the abiotic scenario in which species that can potentially fulfil their requirements will interact.

Lake morphometry (e.g. shape, area, depth and shoreline development) determines patterns of light, heat and wind‐induced turbulence, and also the strength of interaction among lake habitats (pelagic, littoral and benthic).

Macrophytes play an important structural role providing refuge for small organisms against predators and substrate for attached microorganisms and macroinvertebrates. They are also strong competitors of phytoplankton for light and nutrients; and the outcome of such competition often determines the environmental state of the lake.

Fish communities strongly influence lake communities through top‐down effects on lower trophic levels, through their effects on nutrient cycling within the lake and through connecting lake habitats and local trophic webs.

Lake communities differ widely among climate regions, with typically more omnivorous fish species, richer fish assemblages and smaller body sizes of both fish and zooplankton in warmer than in cooler lakes.

Anthropogenic activities strongly influence lake communities, and lake‐specific management activities should be taken to counteract the negative impacts. Most commonly, lakes suffer from eutrophication and measures to reduce external and internal nutrient loading have to be taken to combat eutrophication and its symptoms.

Other current threats to lake communities are acidification, the arrival or introduction of exotic invasive species, and climate change. These processes may occur simultaneously and interact with one another in nonlinear ways. Their effects are therefore currently hard to predict.