Size Structure of Planktonic Particles in Relation to Hydrographic Structure in the Skagerrak

Kahru, M, Leeben A.  1991.  Size Structure of Planktonic Particles in Relation to Hydrographic Structure in the Skagerrak. Marine Ecology-Progress Series. 76:159-166.

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Horizontal distributions of the particle size spectrum and chlorophyll a concentration in near-surface water in relation to hydrographic structure were studied along a transect across the Skagerrak as part of the international SKAGEX-I exercise in May-June, 1990. Results are compared with those of Kiorboe et al. (Mar. Ecol. Prog. Ser. 59: 19-32, 1990) who explained changes in the plankton size structure and the food web as resulting from differences in water column stratification. It was confirmed that the particle size fraction corresponding to diatoms was most abundant along the Skagerrak periphery where stronger vertical mixing is assumed to take place. The smallest (1 to 4-mu-m), chlorophyll-correlated particulate fraction was most abundant in the central Skagerrak with the dome-like near-surface stratification and the presumably reduced vertical mixing. However, distributions along the transect changed considerably over 1 to 3 d due to advection. In addition to the basin-wide changes, correlations of the different particle size fractions to chlorophyll concentration changed over much shorter length scales, often being in opposite phase to each other. An equivalent spherical diameter of 4-mu-m was the size at which the most significant shift in the horizontal distributions occurred.