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Patchy distribution of phytoplankton pigments in South Adriatic oligotrophic environment - winter 2015

Chlorophylls and associated carotenoid pigments are being used to map the chemotaxonomic composition of phytoplankton in the oceans. Compared with larger eukaryotic cells, photosynthetic picoplankton possesses better nutrient uptake capabilities which result in its domninace and higher level of importance with increased oligotrophy. In order to determine spatial distribution of phytoplankton pigments in olygotrophic environment in winter conditions an oceanographic cruise was conducted in southern Adriatic from February 28th till March 3rd 2015. Two major transects were investigated: (i) Dubrovnik to 1000m isobath, and (ii) 1000m isobath to Lastovo island. Total of 45 CTD casts was performed in order to compare bio-optical measurements of chlorophyll fluorescence (Chl F) with pigment concentration. A total of 117 samples were collected on the basis of CTD profile and fluoresces signal and analysed by high- performance liquid chromatography (HPLC). Pigment concentration was extremely low (chlorophyll a maximum concentration was 190ngL-1) reflecting oligotrophy of the environment. Fluorescence signal was detected in depths up to 450m, which was also confirmed by HPLC pigment analyses of Chl a. Beside Chl a, most frequently detected and in highest concentrations were 19’ hexanoyloxyfucoxanthin, fucoxantin, 19’ butanoyloxyfucoxanthin, zeaxantin and one unidentified pigment. All pigments showed high patchiness in their spatial distribution. The unidentified pigment was detected at 500m depth, i.e. in the layer where Chl a was not detected any more. Its identification is the following step in the research.

phytoplankton pigments ; spatial distribution ; Adriatic Sea

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