| Popis: |
Phosphate is considered as limiting nutrient for the middle Adriatic and its concentration rarely exceeds 0.1 µ ; mol dm-3 which classifies this area as an oligotrophic. Sediment phosphorus concentrations are in the range of 3-37 and 8-26 µ ; mol g-1 (d. w.) for inorganic and organic phosphorus, respectively. Concentrations depend on sediment granulometric composition, carbonate content, anthropogenic influence and water column trophic state. Considering the intensive maricultural activities during last decade in this area, we introduced monitoring program which, beside a set of parameters in water column and sediment, included sediment phosphorus speciation. Results of monitoring performed during 2001-2005 showed an enhancement of inorganic phosphorus (14-135 µ ; mol g-1) at most fish farm sites, while organic phosphorus remained in natural range (0-21 µ ; mol g-1). Consequently, occasionally increase in orthophosphate bottom water concentration (up to 3 µ ; mol dm-3) was recorded. SEDEX analysis of inorganic sediment phosphorus species: P adsorbed on / to iron oxy-hydroxides, P bounded in biogenic apatite-“ fish debris P” , authigenic apatite and detrital apatite P) showed “ fish debris” P as prevailing form at fish farms. Its portion in total phosphorus was ~34% which is twofold higher than for the natural state of the middle Adriatic area and potentially presents source of orthophosphate for water column. |
