Cultural eutrophication activity. Polar regions have less human activity and subsequently less cultural eutrophication. One response to added amounts of nutrients in the aquatic ecosystem is the rapid growth of microscopic algae, also known as an algal bloom. In freshwater systems, the formation of floating algal blooms are commonly nitrogen-fixing cyanobacteria (blue-green algae). This outcome is favoured when nitrogen inputs are reduced and phosphorus inputs are increased. Large amounts of algae reduce the amount of dissolved oxygen available in the water for other organisms, which increases fish mortality rates. These areas affected by algal blooms are known as dead zones, and are
Plant to plant communication via mycorrhizal networks help plants in mycorrhizal networks defend themselves against attack by pathogens or herbivores, and transferred nutrients can affect growth and nutrition. Results of studies which demonstrate these modes of communication have led the authors to hypothesize mechanisms by which the transfer of these nutrients can affect the fitness of the connected plants. Plants and fungi form mutualistic symbiotic relationships called mycorrhizae, which take several forms, such as arbuscular mycorrhizae (AM) and ectomycorrhizae (ECM), and are widespread in nature. Host plants provide photosynthetically derived carbohydrates to the mycorrhizal fungi, which use them in metabolism, either for energy or to increase the