Biogeochemical Cycles in Estuaries

According to Perillo (1995, p. 4), an estuary is defined as a semi-enclosed coastal body of water that extends to the effective limit of tidal influence, within which sea water entering from one or more free connections with the open sea, or any other saline coastal body of water, is significantly diluted with fresh water derived from land drainage, and can sustain euryhaline biological species from either part or the whole of their life cycle.  

An improved classification scheme for estuaries is needed if we are to effectively contend with the growing legislative, administrative, and socioeconomic demands in coastal management which requires more unambiguous terminology than currently exists. 

Box models are commonly used biogeochemical studies that involve the interaction of biological, chemical, and geological processes that determine sources, sinks, and fluxes of elements through different reservoirs within ecosystems. 

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Mason RP, Fitzgerald WF, Hurley J, Hanson AKJr, Donaghay PL, Sieburth JM. 1993. Mercury biogeochemical cycling in a stratified estuary. Limnology and Oceanography 38 1227-1241. 

Despite the critical role dissolved gases have in many of the biogeochemical cycles of estuaries and coastal waters, only recently have there been large-scale collaborative efforts (e.g., BIOGEST) addressing the importance of coupling between estuaries and the atmosphere. 

Radionuclides have been used for studying a very broad range of biogeochemical processes in estuaries (table 7.1). In this section more details are provided on the cycling... 

Claire, T. A., J. M. Ehrman, and K. Higuchi. 1999. Changes in freshwater carbon exports from Canadian terrestrial basins to lakes and estuaries under a 2 x C02 atmospheric scenario. Global Biogeochemical Cycles 13 1091—1097. 

Wollast R. (1983) Interactions in estuaries and coastal waters. In The Major Biogeochemical Cycles and Their Interactions (eds. B. Bolin and R.E. Cook), pp. 385-410. J. Wiley and Sons, New York. 

Figure 8.4 Biogeochemical cycling of nutrients, DOM, and POM, in the estuary proper bound by coastal ocean and riverine end-member exchange. (Modified from Wakeham and Lee, 1993.)...

Figure 10.5 Major processes involved in the biogeochemical cycling of N in estuaries and the coastal ocean (1) biological N2 fixation (2) ammonia assimilation (3) nitrification (4) assimilatory NC>3 reduction (5) ammonification or N remineralization (6) ammonium oxidation (speculative at this time) (7) denitrification and dissimilatory NO3 reduction to NH4+ and (8) assimilation of dissolved organic nitrogen (DON). (Modified from Libes, 1992.)...

Chanton, J.P., and Martens, C.S. (1988) Seasonal variations in ebulhtive flux and carbon isotopic composition of methane in a tidal freshwater estuary. Global Biogeochem. Cycles 2, 289-298. 

De Angelis, M.A., and Scranton, M.D. (1993) Fate of methane in the Hudson River and estuary. Global Biogeochem. Cycles 7, 509-523. 

Sansone, F.J., Holmes, M.E., and Popp, B.N. (1999) Methane stable isotope ratios and concentrations as indicators of methane dynamics in estuaries. Global Biogeochem. Cycles 13, 463 174. 

Tovar-Sanchez, A., Sanudo-Wilhelmy, S.A., and Flegal, A.R. (2004) Temporal and spatial variations in the biogeochemical cycling of cobalt in two urban estuaries Hudson River Estuary and San Francisco Bay. Estuar. Coastal Shelf Sci. 60, 717-728. 

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