Winter distribution of algal pigments in small- and large-size particles in the northeastern Atlantic
Mejanelle, L.; Laureillard, J.; Fillaux, J.; Saliot, A.; Lambert, C.
Deep-Sea Research Part I Oceanographic Research Papers 42(1): 117-133
ISSN/ISBN: 0967-0637 DOI: 10.1016/0967-0637(94)00036-r
Particles were collected by filtration on GF/F filters and by vertical hauls of 50 mu-m mesh-sized net throughout the water column (50-1700 m) in the northeastern Atlantic in January 1989 during the Medatlante I cruise, in the framework of the French JGOFS program. Particles were analysed for their organic carbon and algal chlorophyll and carotenoid pigments by high-performance liquid chromatography coupled with UV absorbance and fluorescence detection. Complementary analyses were performed on a surface sample for sterols and fatty acids by gas chromatography and gas chromatography/mass spectrometry. Organic carbon concentrations were 2-3 orders of magnitude higher in GF/F (10-50 mu-g l-1) than in net particles (0.01-0.06 mu-g l-1). The same ratio was encountered for pigments: 4-603 ng l-1 and 0.003-0.037 ng l-1, respectively. Among 11 GF/F samples collected between 500 and 1700 m, four samples contained pigments in detectable amounts (4-106 ng l-1). Their pigment distribution pattern was close to deep GF/F samples, but differed from the pigment pattern of deep net-collected particles, mainly composed of fecal pellets. This latter sinking material was enriched in chlorophyll degradation pigments and showed higher values of the ratio (sum of carotenoids)/(sum of chlorophylls) than those observed in small-size particles. The combined information from pigments, sterols and fatty acids shows that Prymnesiophytes in a post bloom situation contributed to a major part of the surface autotrophs. Two processes of rapid transfer of organic matter between the surface and the deep Mediterranean water are discussed: fecal pellets of herbivorous plankton and sedimentation of aggregates partly linked to the presence of Prymnesiophytes.