EUTROPHICATION: CHANGES IN ESTUARINE PHYTOPLANKTON PRODUCTIVITY
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Date
1974
Authors
McLean, April G.
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Abstract
Estuaries are individually unique ecosystems, each with specific environmental characteristics. There are, however, some generalizations that can be made describing estuaries overall. Caspers (1967) gives four features applicable to estuaries : 1) limited to rivermouths in tidal seas; 2) saline areas present, their extent dependent on the amount of freshwater runoff; 3) the upper limit of the estuary is defined by the upper limits of tidal influence into freshwater zones; 4) characterized by changeable salinities and instability of environmental factors. Brackish systems have been put into three categories by a number of workers (cf. Emery, et.al.(1957), Pritchard (1967)) breaking them into positive, inverse and neutral groups. Positive estuaries are river dominated, freshwater runoff exceeding evaporation rate. Inverse estuaries are characterized by rapid evaporation rate, surpassing runoff and precipitation. These are hypersaline the majority of
the time. Neutral estuaries have a balance between evaporation and freshwater influx. These classifications, however, are oversimplifications. Pritchard (1967) defines an estuary as a "semi-enclosed coastal body of water which has a free connection with the open sea and within which seawater is measurably diluted with freshwater derived from land drainage." Pritchard's definition restricts the term "estuary" to signify only the so-called "positive estuary". Emery, et. al. (1957) use the term "normal estuary" to be equivalent to positive estuary.
Description
21 pages
Keywords
Eutrophication, Phytoplankton, Marine Biology