Regional spatial distributions of organic carbon in coastal surface sediments of the Baltic Sea - A statistical approach and a rationale for geophysical surveying

The concentration of organic carbon in coastal sediments depends on several inter-related variables in a complex way. However, within a relatively small coastal area, several of these factors vary only little. Under these circumstances one variable, which to the largest extent determines the concentration of organic carbon is the mechanical energy of the bottom sediments. In this study we have collected sediment cores from two types of bottoms, transport (discontinuous deposition of fine particles and lower water content of sediments) and accumulation bottoms (continuous deposition of fine particles and higher water content of sediments), in a small area of the Stockholm Archipelago, in the Baltic Sea. The two bottom types are defined according to the water content of the sediment samples at the surface and distribution with depth. A statistical analysis of the organic concentration data by the means of an Analysis of variance (ANOVA) test with a 2-way layout, showed that the bottom type and not the sediment depth determines the concentration of organic carbon in these sediments. This result is believed to be universal under certain premises, and hence provides a rationale for surveying (with e g acoustic methods) the bottom dynamics whenever an estimate of the organic carbon concentration in the sediments of a given coastal area is desired. If the mean organic carbon concentration is estimated by considering these two sub-populations instead of a simple estimate, a smaller error will be obtained.