Details

Autor(en) / Beteiligte

• Pomeroy, L.R.
• Sheldon, J.E.
• Sheldon, W.M.
• Blanton, J.O.
• Amft, J.
• Peters, F.

Titel

Seasonal Changes in Microbial Processes in Estuarine and Continental Shelf Waters of the South-eastern U.S.A

Ist Teil von

• Estuarine, coastal and shelf science, 2000-10, Vol.51 (4), p.415-428

Ort / Verlag

London: Elsevier Ltd

Erscheinungsjahr

2000

Link zum Volltext

Quelle

Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)

Beschreibungen/Notizen

• Respiratory rates of microbial plankton in five estuaries of Georgia, U.S.A. are similar at any given time of year, both within and among the estuaries, but change from 0·16±0·02μmh−1(mean±SE) in winter to 0·95±0·08μmh−1in summer, following the Arrhenius law. In short-term enrichment experiments, heterotrophs respond to added labile carbon, thus indicating a dual temperature-substrate limitation. The relatively much greater microbial metabolic rates in the marsh sediments than in estuarine water, the dominance of estuarine primary production in south-eastern U.S.A. by higher plants, and limited phytoplankton production in turbid water may explain the carbon limitation. Respiratory rates of south-eastern U.S.A. continental shelf microbial plankton are 1·1±0·14μmh−1near shore in winter and 0·95±0·08μmO2h−1in summer. In mid-shelf they are 0·7±0·11 in winter and 1·3±0·28 in summer, and at the edge of the Gulf Stream they are 0·3±0·1 in winter and 1·0±0·3 in summer. Thus, in contrast to the estuaries, microbial respiration in shelf waters is as high throughout the year as estuarine respiration in summer, showing no significant seasonal change, but respiration in the Gulf Stream changes seasonally. Although primary production on the south-eastern shelf is relatively high, especially near shore and in intrusions of North Atlantic Central Water, no correlation was found between respiratory rates of microbial plankton and concentrations of chlorophyll a. Concentrations of dissolved free amino acids in continental shelf waters are 39–87n m with no evident seasonal cycle. Compared to other estuarine-shelf systems, the south-eastern system is known not to be highly productive of higher trophic levels, i.e. fishes and shellfish. We postulate that this is a result of the trophic structure on the south-eastern U.S. continental shelf system which in turn is a consequence of the distribution of macronutrients, principally nitrogen. Most new nitrogen is from the North Atlantic Central Water rather than from terrestrial sources and, therefore, it is less well distributed over the central shelf.