Definition of Shallow Lakes and Ponds and World Distribution

Shallow lakes and ponds are the most abundant lake types in the global landscape. They provide a myriad of ecosystemic and social services as well as goods and materials, while having great conservation value (for example for migratory birds). Such shallow systems usually occur in lowland areas, many in association to seasonal changes in the flood regimes of rivers. The origin of many of these systems can also be related to geological disturbances, such as glacial movements or other processes that generate depressions in the landscape. Also, many shallow lakes and ponds have been created by humans after millennia of landscape modification, such as stream and river impoundment or diversion, or when digging for metals, sand, gravel and peat (particularly common in Medieval times in Europe) or by establishing fish ponds.

The perception that despite constituting the most abundant freshwater systems, shallow lakes and ponds still do not represent a large percentage of the world's total freshwater area has been recently modified. Millions of water bodies smaller than 1 km2 occur, and small lakes and ponds (0.001-0.1 km2) represent most of the world's lacustrine area. The historical undercounting of small lakes has led to a significant underestimation of the world's lake and pond area.

Shallow lakes can be defined as more or less permanent standing water bodies that are shallow enough as to, potentially, allow light penetration to the bottom.

They can thus be colonized by higher aquatic plants over the entire basin or at least in large sections (Figure 1), although this is not necessarily the case in all lakes. Ponds are particularly small shallow lakes, typically less than 1 hectare in area. Shallow systems are also defined as polymictic, implying that the entire water column circulates continuously or for long periods and that long-lasting thermal stratification in summer is lacking. The maximum depth for these processes to occur is around 5-7 m in the temperate region, but most typically shallow lakes are <3 m deep. In contrast to deep water bodies, shallow systems are often characterized by a greater littoral zone and a closer contact with the surrounding lands, entailing a stronger aquatic-terrestrial exchange of matter and organisms. The water volume is relatively low. Together with polymixis, this results in enhanced benthic-pelagic coupling and greater impact of sediment processes in the water column. Typical shallow lakes and ponds are likely more productive than deep lakes, owing to the greater recycling of nutrients that become available for phytoplankton and the contribution to productivity by the aquatic plants and their attached epiphyte communities. This is reinforced by the fact that these systems are often distributed in the open cultivated landscape and therefore receive higher nutrient input.

Shallow lakes and ponds often show higher species richness per unit of area than large lakes owing to the strong interaction between the littoral and the pelagic habitats (Figure 1). Furthermore, lack of fish

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Shallow Lakes Ecosystem

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Figure 1 Main physico-chemical and biological variables of temperate shallow Danish lakes with different lake surface area, shown as box-plots (n = 796 lakes). Each box represents the 25% and 75% percentiles, the horizontal line the mean value, and the top and bottom of the thin line depict the 90% and 10% percentiles. Redrawn from Sondergaard etal. (2005) Archiv für Hydrobiologie 162:143-165.

sometimes occurring in small, isolated water bodies (owing to high risk of extinction and low colonization opportunities or owing to strong changes in water depth) may lead to enhanced abundance of waterfowl, amphibians, invertebrates, and plants.

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Responses

  • Brigitte
    Why shallow lakes are more productive than deep lakes?
    2 years ago
  • russom
    Why a shallow pond is more productive than deep pond?
    2 years ago
  • ensio
    What are shallow lakes and ponds?
    1 year ago
  • ZULA
    What is considered a shallow lake?
    8 months ago
  • Madihah
    Why small and shallow lakes are productive than big lakes?
    4 months ago

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