Lake Communities

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Lake Communities

Sarian Kosten, Radboud University Nijmegen, Nijmegen, The Netherlands
Mariana Meerhoff, Universidad de la República, Maldonado, Uruguay

Published online: November 2014

DOI: 10.1002/9780470015902.a0003177.pub2

Full Article on Wiley Online Library

Abstract
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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.

Keywords: oligotrophic; eutrophic; pelagic; littoral; benthic; fish; macrophytes; plankton; shallow; deep

	Figure 1. A conceptual model showing how ‘filters’ operating at different spatial scales determine the community structure of lakes, and how different anthropogenic activities add new or modify natural filters. Modified from Brönmark and Hansson ().
	Figure 2. Common thermal stratification patterns in lakes. Light blue indicates warm water, dark blue indicates cold water. Dimictic lakes mix twice a year (in spring and autumn) and stratify in winter when they are covered by ice and in summer when the surface waters (epilimnion) warm up. Warm monomictic lakes never freeze, and are thermally stratified throughout much of the year. Only during winter the surface waters cool to a temperature equal to the bottom waters resulting in a mixing of the different water layers (In contrast: cold monomictic lakes are covered by ice throughout much of the year and mixing only occurs during the ice‐free period). Polymictic lakes mix throughout the year and – especially in warm regions or during heat waves – stratify shortly in summer when there is little wind or in winter when ice‐covered (the latter is not shown in the figure). Drawing by S. Kosten.
	Figure 3. The different habitats of a lake, including the near‐shore littoral zone, the open‐water pelagic zone and the benthic or profundal zone where low‐light levels inhibit the growth of primary producers (aphotic zone). Representative organisms from the main communities of the ‘classical food web’ and their feeding interactions are shown. Arrows indicate the major fluxes of nutrients among lakes zones and with the surrounding terrestrial environment through the riparian zone. Subsidies from the lake to the land may be locally important. Drawing by M. Meerhoff & T. Christensen.
	Figure 4. Simplified scheme of trophic interactions among main trophic groups in temperate and warm shallow lakes with comparable phytoplankton (phyto) biomass. The densities in the subtropics are expressed relative to those in the temperate lakes (considered as the unit, for being the most known web). Shrimp relative density is dotted due to typical shrimp absence in temperate lakes. The trophic groups were classified as primary producers (periphyton and phytoplankton), intermediate herbivores (h.) such as cladocerans, and other invertebrates of littoral (Lit.) and pelagic (Pel.) zones, intermediate carnivores (c.), intermediate omnivores, and top carnivores (piscivorous fish). Except fish, the same taxa shared the same trophic classification in both climate zones. Modified with permission from Meerhoff et al. (). Copyright © 2007, John Wiley and Sons.
	Figure 5. Conceptual scheme of changes in the fish community structure (mean body size, density and biomass) along a productivity gradient (eutrophication process). Often, a decrease in oxygen concentration as a consequence of very high nutrient levels may promote sudden massive fish kills. Drawing by M. Meerhoff and T. Christensen.
	Figure 6. Some relationships now established that link climate change and an enhancement of eutrophication symptoms (Moss et al., , reproduced by permission of the Freshwater Biological Association. Drawing by A.R. Joyner).

Article Title:	Lake Communities
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