THE DISTRIBUTION AND RECYCLING OF CHLOROPHYLL, BACTERIOCHLOROPHYLL AND CAROTENOIDS IN THE BLACK-SEA

Chlorophyll, bacteriochlorophyll e (Bchl e), carotenoids and particulate organic carbon were measured in a suite of suspended particulate matter and sediment trap samples collected from three stations in the Black Sea. Vertical profiles of particulate chlorophyll a (Chl a) display well-developed subsurface maxima with concentrations of up to 465 ng l-1 between 30 and 40 m. Associated with these maxima are the carotenoids 19'-hexanoyloxyfucoxanthin from prymnesiophytes and fucoxanthin from diatoms. Subsurface maxima in Bchl e, characteristic of the obligate photoautotroph Clorobium phaeobacteriodes and C. phaeovibriodes, were also observed between 80 and 100 m in all samples. Vertical profiles of Bchl e display maxima at the H2S interface (chemocline) and provide the first evidence for anoxygenic photosynthesis in the Black Sea. Bacteriochlorophyll e was present at stations separated by 450 km, implying a large areal extent to the bacterial plate. Pigments are rapidly recycled with high efficiency in the euphotic zone. The distribution of pigments in our sediment trap samples is considerably different from reported distributions of pigments in sediment trap samples collected from oxic open ocean systems. High concentrations of unaltered algal pigments, originating at the base of the euphotic zone, were measured in sediment trap samples collected in and immedately below the chemocline. The carotenoid 19'-hexanoyloxyfucoxanthin, abundant in samples collected from depths < 35 m, was not detected in any of our trap samples.