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In addition, nitrogen release during the decomposition process was estimated. Degradation rates were highest at the start of the experiment (0.2 d-1 at day 7) and decreased as time progressed (0.025 d-1 at day 52). Degradation rate increased with increasing temperature. After 52 days about 7% of the original dry weight remained at 25 0C, while at 5 0C about 25% of the original dry weight was still present. Differences in degadation rate between aerobic and anaerobic conditions at one temperature were not significant. This suggests that oxygen does not seem to play a major role in the decomposition process. However, nitrogen release was much higher under oxic conditions than under anoxic conditions. A decrease in inorganic nitrogen concentration was observed with increasing temperature. At the same time, the C/N ratio of the Ulva tissue decreased with time and temperature.