Functioning of Shallow Waters in Different Climatic Regions

Most of the previously described processes hold true for shallow lakes and ponds in temperate climates, whereas information on shallow lakes and ponds in other climates is unfortunately limited. The climate regime imposes, however, important differences in the structure and functioning of these ecosystems, not least because of different patterns in the trophic interactions (Figure 7). In many (sub)tropical and warm temperate lakes, the climate is characterized by dry and wet seasons, with relatively high temperatures and long day lengths. In the wet season, nutrients enter from the catchment. Usually, the soils of warm regions have long been leached of nutrients due to their old age. By contrast, the soils in the catchments of most cold temperate lakes are

Temperate lakes

Temperate lakes

Subtropical lakes
Shallow Lakes Ecosystem

Figure 7 Role of submerged plants in the functioning of shallow lakes and ponds, showing the effects on different physical, chemical and biological processes that ultimately affect turbidity, in temperate (above) and subtropical (below) systems. Note that the benthic-pelagic coupling is included in the scheme in a partial manner and requires further consideration. The qualitative effect of each route can be determined by multiplying the signs along the way. Symbols: +positive,-negative, ? scarce data, () occasionally. Modified and updated after original model proposed for temperate lakes in Scheffer etal. (1993) TREE 8: 275-279, (Copyright Elsevier).

Figure 7 Role of submerged plants in the functioning of shallow lakes and ponds, showing the effects on different physical, chemical and biological processes that ultimately affect turbidity, in temperate (above) and subtropical (below) systems. Note that the benthic-pelagic coupling is included in the scheme in a partial manner and requires further consideration. The qualitative effect of each route can be determined by multiplying the signs along the way. Symbols: +positive,-negative, ? scarce data, () occasionally. Modified and updated after original model proposed for temperate lakes in Scheffer etal. (1993) TREE 8: 275-279, (Copyright Elsevier).

relatively young and may provide abundant nutrients. However, warm lakes tend to be more productive than similar cold lakes. For a 50-fold range of light energy available from the poles to the equator, a 1000-fold range in algal production is found. Therefore, the 'latitude effect' may thus be related to a greater rate of nutrient recycling and mineralization with the higher temperatures at decreasing latitudes. Internal nutrient cycling in warm lakes is thus relatively more important and external loading relatively less important than in cold temperate lakes. On the other hand, patterns regarding nutrient additions and the impacts of fish are more unpredictable with increasing latitude, probably due to more variable weather.

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