A MASS-BALANCE OF CHLOROPHYLL DEGRADATION PRODUCT ACCUMULATION IN BLACK-SEA SEDIMENTS

The distribution of chlorophyll degradation products was measured in B lack Sea sediment trap and sediment samples. Chlorophyll degradation p roducts were identified as free phorbins, phorbin steryl esters, high molecular weight chlorophyll degradation products, and acid extractabl e chlorophyll degradation products. When all these sinks are considere d, an inventory of chlorophyll degradation products can be established which identifies four times more sedimentary phorbins than standard H PLC studies alone. The concentration of total chlorophyll degradation products in the sediment trap samples varies with season and, in the s ediments, increases with depth from Unit I into Unit II. In Unit III s ediments, the total phorbin concentration dramatically decreases, Thes e trends are similar to those of the total organic carbon concentratio n. Variations in the ratio of total phorbin/total organic carbon with depth in the sediments appear to be related to previously suggested ch anges of oxygen concentrations over time in the Black Sea water column . This new data was combined with data from the literature to create a mass balance of chlorophyll flux, degradation, and accumulation in th e Black Sea. It is concluded that once chlorophyll degradation product s reach the anoxic water column, they survive to be deposited in the u nderlying sediments. Although a larger percentage of total organic car bon, compared to total phorbin, passes out of the photic zone, the pho rbin macrocycle appears to be more stable under anoxic conditions than is total organic carbon.