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Life in Freshwater

Nutrients in Ponds and Lakes

The dissolved minerals present will depend very much on the geology of the land from which the water inflow crosses. In uplands of granite and other igneous rock this may be quite low. Calcium ions are essential for maximising population densities as it is needed for skeletal tissue, cell walls and shells in molluscs. This is the reason that chalk rivers are so diverse compared to upland ones. Nitrogen enters in the form of ammonia or nitrates. The latter may be due to run-off from agricultural land and will encourage eutrophication. This means a substantial growth of plant material. Phosphate occurs naturally in small amounts and combines with iron to form ferric phosphate, precipitating to the benthic region. However, phosphate is now a significant pollutant of water entering from farmland and will also result in eutrophication.

Organic matter is an important source of nutrients. Decomposition releases valuable nutrients and is vital for the recycling of materials within freshwater ecosystems. This is called autochthonous material - materials obtained through recycling. Within this site we will refer to ponds and lakes as natures dustbins. Leaves falling from trees in autumn may be blown significant distances but the moment they touch the surface tension they stop and eventually sink to be trapped and decomposed. Nutrients derived from matter originating outside freshwater are called allochthonous .

Abiotic factors:

 


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