Differences in the composition and organisation of three mutually alternative aquatic vegetation types are examined, paying particular attention to the influence exerted through the food webs in regulating the transfer of primary products to the higher trophic levels. Whereas limnoplanktonic communities of open water, whether transferring primary products directly to animals or largely through micro-organisms, are founded upon near-climactic vegetation, shallow margins supporting macrophytes provide a pioneer-stage to terrestrial ecosystems. Small or shallow lakes are entirely ‘marginal’ and are susceptible to dominance by one hydroseral stage or another but with an outcome which depends upon the operating alternative state. These factors change in time or may be altered artificially, to drive the system towards another natural or regulated alternative steady state.

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