Lakes phytoplankton bloom

In temperate lakes phytoplanktonic blooms occur in response to the seasonal availability of nutrients, which is controlled by stratification of the water column (see Section 3.2.2b). The situation is, therefore, similar to seasonal thermocline development and decline in temperate oceans. During summer stratification nutrients in the epilimnion become depleted. During the spring and autumn overturns, nutrient-rich (and oxygen-deficient) waters of the hypolimnion mix with the epilimnion and fuel phytoplanktonic blooms, primarily in the spring. 

Some of the species involved in phytoplanktonic blooms are toxic and can pose a danger to humans. Cyanobacterial blooms (e.g. Anabaena) resulting from eutrophication in lakes and other still waters in late summer can release toxins into the water. Although cyanobacteria occur naturally in the succession of phytoplanktonic species during a typical growth season... 

Many environmental factors vary seasonally. For example, the incidence of sunlight has an important effect on photosynthesis and resultant dissolved oxygen concentrations in many aquatic areas. So, the abundant phytoplankton blooming in the spring- summer period is related to the seasonal oxygen oversaturation in the surface water of two studied lakes (Stoyneva, 1997). 

Freshwater phytoplankton blooms commonly occur in reservoirs, lakes, canals, and ponds under eutrophic and other physicochemical conditions that are favorable for bloom formation. Among the different types of phytoplankton blooms that can occur in freshwater ecosystems, cyanobacterial (blue-green algal) blooms are usually the most undesirable for the following reasons 1) certain species of cyanobacteria can produce toxins that kill aquatic and terrestrial animal life 2) some species of cyanobacteria produce off-flavor compounds that can impart an undesirable taste to cultured fish 3) cyanobacteria are a poor base for... 

Eutrophication can be defined as the addition of nitrates and phosphates to the land through the use of fertilizers and soil conditioners. Eutrophication is a very common pollutant from fertilizers in farming or from natural causes. Eutrophication can deplete oxygen in ocean and freshwater lakes causing algae and phytoplankton blooms in the water. 

In this way, the near-linear chlorophyll-phosphorus relationship in lakes depends upon the outcome of a large number of interactive processes occurring in each one of the component systems in the model. One of the most intriguing aspects of those components is that the chlorophyll models do not need to take account of the species composition of the phytoplankton in which chlorophyll is a constituent. The development of blooms of potentially toxic cyanobacteria is associated with eutrophication and phosphorus concentration, yet it is not apparent that the yield of cyanobacterial biomass requires any more mass-specific contribution from phosphorus. The explanation for this paradox is not well understood, but it is extremely important to understand that it is a matter of dynamics. The bloom-forming cyanobacteria are among the slowest-growing and most light-sensitive members of the phytoplankton. ... 

The discharge of organic pollutants into lakes or declines in the concentrations of copper, zinc, and other heavy metal toxins may promote the growth of phytoplankton (e.g. algal blooms ). Greater biological activity may then increase anoxic conditions in lake bottoms, which stimulate the reductive dissolution of (oxy)(hydr)oxides and increase the mobilization of arsenic. In particular, Martin and Pedersen (2002) concluded that reduced discharges of copper, zinc, and nickel to Balmer Lake, Ontario, Canada, increased phytoplankton production and arsenic mobility in the lake. 

Phytoplankton abundance and occurrence of blooms are the parameters for which a not necessarily taxonomic determination is required. The abundance can be measured as the total count of cells and/or colonies in a unit volume of water or recalculated further into biovolume or biomass. The WFD allows use of chlorophyll a as a surrogate for phytoplankton biomass, thus it is considered a biological parameter. In fact, chlorophyll a is the most frequently measured phytoplankton metric in lakes. Not all countries have included the bloom occurrence in routine monitoring as in some areas (e.g. countries belonging to the Alpine GIG) they occur too rarely and inegu-larly (if at all). Other non-taxonomy-based metrics, like size composition and primary productivity, are successively less considered in lake monitoring schemes. 

Van Iwaarden, A.J.W., 1979. Micro-autoradiographical Determination of the Primary Productivity of Different Phytoplankton Species During the Spring Bloom (1979) of the Lake Grevelingen. Delta Institute, Yerseke, Stud. Rep. D9-1979, 85 pp. 

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