Anthropogenic eutrophication of lake ecosystems is a global problem, especially for some large shallow lakes. But scientists are not clear why shallow lakes appear prone to eutrophication.
Now researchers led by Prof. Qing Boqiang from the Nanjing Institute of Geography and Limnology at the Chinese Academy of Sciences (NIGLAS) have given clues on the issue.
Their findings are published in Water research on June 9.
The spread of the lake eutrophication varies in terms of catchment geology, climate, land uselandscape position, connectivity and morphology of the lake, each of which varies depending on the lake area or ecoregion.
In this study, researchers analyzed 1151 lakes with areas over 0.5 km2 located in Europe and the United States to identify how lake morphology and regional socio-ecological systems interact to influence the susceptibility of lakes to anthropogenic eutrophication.
They found that the depth of the lake is related to the ecoregion and the land use of the lake ecosystems. These factors largely determine the intensity of human activity and therefore the productivity of the lake.
In general, shallow lakes are located in naturally fertile plains and lowlands, where they are exposed to strong anthropogenic disturbances (eg agriculture and urban development). They are prone to ingesting large amounts of nutrients due to extensive drainage networks. In contrast, deep lakes are often concentrated in poor mountainous areas (ie mountains and highlands) with mostly natural land cover (eg forests and shrubs), low human disturbance and limited nutrient inputs.
Compared to deep lakes, shallow pools often have a small volume and low capacity to dilute imported nutrients, leading to high sensitivity of anthropogenic impact. In addition, strong water-sludge interactions are more common in shallow lakes and sediment is more susceptible to resuspension in such lakes, leading to increased internal nutrient loading and higher productivity.
In general, scientists have found that the depth of the lake is not only to predict the external load of nutrients footman; it is also associated with sensitivity to anthropogenic disturbances, with shallower lakes being more sensitive.
“Shallow lakes in agricultural or populated areas may be particularly susceptible to eutrophication, and their eutrophication may not be accidental,” said Prof. Qing.
He said shallow lakes should be given “special attention” because of the high risk of deteriorating water quality and eutrophication. He also noted that they may be more resilient to recovery than deep lakes.
By elucidating the impact on eutrophication, this study can help promote the protection and restoration of lakes worldwide.
Jian Zhou et al, Anthropogenic eutrophication of shallow lakes: Sometimes ?, Water research (2022). DOI: 10.1016 / j.watres.2022.118728
Chinese Academy of Sciences
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