A high nutrient load is is not beneficial in temperate lakes

A high nutrient load is (is not) beneficial in temperate lakes. Defend both sides of the argument, giving examples and evidence to support your argument.

Solution

Temperate lakes are lakes in temperate regions (zone) on earth. It is the region between the Arctic Circle and the Tropic of Cancer (between 23.5 and 66.5°N) and between the Antarctic Circle and the Tropic of Capricorn (between 23.5 and 66.5°S) in northern and southern hemisphere. The temperatures in temperate regions are generally moderate, it is not extremely hot or cold and the changes between winter and summer are also usually moderate.

Impact of high nutrients load is not beneficial in temperate lake: Nutrients are the inorganic ions like nitrogen or phosphorus etc. These nutrients are necessary for the growth of algae and phytoplankton that are the base of the food chain and supports the entire aquatic ecosystem. More nutrients will lead to high growth of algae in the lake which are not even required to run the aquatic ecosystem of the lake. Therefore the excess of the green plants or algae will die and will increase the water turbidity and also increases the microbial growth dependent of dead and decaying materials of algae and phytoplankton etc.   These micro-organisms will consume more oxygen to carry out decay process. This will lead to the decrease in dissolved oxygen in the lake. Because of this other aquatic organisms like fishes etc. will die due to lack of oxygen. This will ultimately increase the lake turbidity and lake will lead towards eutrophication.

Impact of high nutrients load is beneficial in temperate lake: Temperate lakes are thermally stratified in summer. The upper layer is hot and temperature decreases with depth of the lake. There is no mixing of water in upper and lower layer. A little mixing in upper layer occurs only due to wind flow. In winter season also temperature of all layers of water is equally low so mixing of water also not occurs in winter. The mixing of water occurs only in autumn season, where lower layers of water have little high temperature than upper layers.

Therefore the productivity of temperate lake is very low in summer and winter as there is no mixing between the upper and lower layers. High nutrients content will be helpful for algal and green plant growth during summer, which will make enough food to run the food chain in other seasons also.