Organic Carbon and Organic Matter Levels in Sediments of the Strait of Hormoz, the Persian Gulf

Total organic carbon has a major influence on both the chemical and biological processes that take place in sediments. Algal bloom is one of the organic carbon levels in aquatic ecosystems. In 2009 algal bloom occurred in the Hormozgan province and prolonged for months, which finally setteled down in 2010. In this study the variations of total organic carbon (TOC), organic matter (TOM) and total nitrogen (TN) contents, and the carbon-nitrogen ratio in superficial sediments collected from 33 stations at the Strait of Hormuz were investigated. Sampling was performed at the depths of 14 to 59 meters in spring of 2010 after sinking algal bloom in the area. The TOC content in the surface sediments revealed values in the range of 0.5 up to 3.5 % (mean 2 %, median 2.2 %, standard deviation 1.3%). The values generally highlighted a gradient increasing with distance from the Strait of Hormoz. According to the standards of Environmental Protection Agency of United State, the organic carbon concentrations in the analyzed sediments were in the range of sediments with low to medium organic carbon level. Organic matter levels were in the range of 4.4 to 10 % (mean 7.3 %). Statistical analysis demonstrated that there were no significant differences between the stations. According to Pearson correlation, total organic matter and organic carbon had significant correlation with each other (R2=0.81, P=0.01). Results showed that deeper parts had relatively higher organic carbon level (R2=0.66, P=0.05). Our investigation showed that the accumulation pattern of organic carbon depended on the grain size of the sements. The stations with higher percent of silt and clay had higher organic carbon. The results revealed that organic carbon level has increased in resent years, which can influence on the potential of methylation and accumulation of metals in sediment. In this study the TOC/TN ratio for 33 sediments were between 3 and 8, which demonstrated that the source of organic carbon could be related to the recent algal bloom.