concentrations are higher than at the surface. In each estuary, these 

 three enrichment processes proceed simultaneously. 



Oceanwide, the annual contribution of nutrients by all of the rivers 

 of the world appears to provide for only a small part of the total 

 marine productivity. Data are provided showing the nutrient budget of 

 the oceans regarding nitrogen, phosphorus, and silicon, and the use of 

 these elements by phytoplankton. The oceans appear to be nearly in 

 steady state with regard to the contributions of these elements by the 

 rivers. Great as the local enrichment of estuaries by the river may 

 be, it appears that the oceanographer need not invoke this supply to 

 maintain productivity of the oceans. 



In considering pollution as an enrichment source, it was determined 

 that phosphorus can be used as an index of excess pollution in estuarine 

 waters. Three bays off Long Island, New York, were used for experimentation 

 and data gathering. It was found that the concentration of inorganic 

 phosphorus was several times greater than the usual content of sea 

 water in this area. The phytoplankton count reflected a true bloom, 

 far exceeding the populations found in normal unpolluted estuarine 

 waters. "Weed" species grow prolifically in this estuary. They are 

 not, however, good food for many of the normal populations, but their 

 growth excludes the normal estuarine phytoplankton species. While 

 fertilization may increase the production of species of value to mankind, 

 uncontrolled pollution, even though it may increase the total productivity 

 of phytoplankton, may destroy the natural resources of an estuary. 



Circulation in estuaries is frequently characterized by a two-layered 

 flow with the surface layers diluted by river water escaping seaward 

 and the salt water entering near the bottom. The estuary may be fertilized 

 by this seawater countercurrent, since, in many cases, the sea water 

 is drawn from depths below the euphotic zone in the ocean where the 

 concentration of nutrients has not been depleted by the growth of 

 phytoplankton. Organisms grown in the surface layers of the estuary 

 may sink to countercurrent depths where decomposition releases the 

 nutrients, which will then be returned again for reuse within the 

 estuary. Nutrients can thus become trapped within the estuary and 

 build up unusually high concentrations. (H.D.) 



Keywords: phytoplankton, nutrients, estuaries 



III-D-11 



Patrick, R. 1967. Diatom communities in estuaries. Pages 311-315 in^ 



G.H. Lauff, ed.. Estuaries. American Association for the Advancement of 



Science, Washington, D.C. 



This paper explores the ecological factors affecting the occurrence 

 of diatoms and the structure of diatom communities. The types of diatoms 

 that compose estuary communities are usually benthic and neritic species, 



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