Biogeochemical parameters of sea water and bottom sediments near the Curieuse Island (Seychelles Islands)

Biogeochemical reef studies carried out in 1981 and 1984 found low concentration of total natural and anthropogenic hydrocarbons in inshore waters. Detection of lignin in marine and bottom sediments indicates that the land has major effect on makeup of organic matter there. Comparison of compositions of organic matter in sea water, suspended matter and bottom sediments indicated that it was altered rapidly by the reef community. Thus, in the inshore zone of the island, runoff from the land is important in supplying nutrients to the reef ecosystem alongside with transport of nutrients by deep waters. Concentrations of nutri¬ents (N, P) in the inshore zone are higher than in waters of the tropical part of the ocean. Nitrogen is the limiting element in development of phytoplankton in the inshore zone

(Table 1) Concentrations of phosphorus- and nitrogen forms in the near-bottom layer of the Baltic Sea

Nitrogen and phosphorus compounds in the near-bottom layer and interstitial waters in sediments of the Baltic Sea were studied. Statistical analysis of data revealed that variability of hydrochemical conditions in regions of fluid fluxes is higher than in regions without such fluxes. Hydrochemical conditions (concentrations of mineral phosphorus and ammonia in the near-bottom layer) in locations of fluid fluxes appeared to depend on intensity of these fluid fluxes. Influence of the fluid fluxes on formation of the hydrochemical structure and specific conditions is discussed