Aims: We describe the different nutrients that phytoplankton require, their variation among phytoplankton groups and their different nutritional modes and acquisition mechanisms. We furthermore describe the consequences of nutrient scarcity and excess on competition among phytoplankton and the effects of anthropogenic nutrient enrichment on phytoplankton community composition, productivity, and ecosystem functioning. Main concepts: Nutrient requirements and stoichiometry. Nutrient acquisition mechanisms. Competition for nutrients among taxa. Role of nutrients in controlling productivity. Ecological consequences of varying nutrient availability. Main methods: Cell nutrient analysis, growth rate measurements, physiological, biochemical and molecular genetic analysis of acquisition mechanisms. Competition experiments, theoretical modeling of species interactions. Measurements of the physical structure, nutrient chemistry and composition, and abundance of biota in inland waters. Conclusions: The concentration of nutrients are low in many inland waters and therefore are a major controlling factor on phytoplankton abundance and productivity. Moreover, because phytoplankton exploit inorganic, dissolved organic and particulate nutrients to satisfy their nutrient requirements, nutrients may become limiting even in nutrient-rich systems. Differential element requirements, uptake rates and storage capacities among taxa, along with other environmental conditions, control phytoplankton community composition. Anthropogenic increases in nutrient loads to inland waters, particularly of phosphorus and nitrogen, has led to widespread eutrophication of inland waters leading to increased productivity. The changed conditions alter phytoplankton species composition, lead to the reduction or loss of freshwater plants and cause oxygen depletion, especially at depth when lakes or reservoirs are stratified. This alters the ecological distribution of species reliant on oxygen, can cause fish kills and produces a positive feedback by increasing the internal load of nutrients stored in the sediment to the overlying water. Future research should investigate the ecological significance of organic nutrients, explore the uptake characteristics of a wider range of taxa and exploit the burgeoning information available from genome sequences.
|Title of host publication||Encyclopedia of Inland Waters, Second Edition|
|Number of pages||9|
|Publication status||Published - 1 Jan 2022|