Nitrogen and Phosphorus in Coastal Sediments Covered by Cyanobacteria Mats (9 pp)

The chemical behaviour of various forms of nitrogen and phosphorus in coastal sediments covered by cyanobacteria mats was studied. Sediment cores of about 10 cm length along with water samples were collected during the course of a year from two Greek coastal areas. Sediments were fractionated in three distinct layers according to their structure. A wet oxidation method for the simultaneous determination of total nitrogen and total phosphorus was applied to all sediment samples. In situ measurements of pH, temperature and salinity were also carried out. The pH of the sediment showed a gradual reduction downwards. The highest content of total organic carbon (TOC), total nitrogen and total phosphorus were detected in the surface layer of the sediment samples. The contribution of organic phosphorus to the total phosphorus ranged between 0 percent and 50 percent with an average value of 26.6 percent.