Use of amino acid composition to investigate settling and resuspension of a spring bloom in the southern Skagerrak

Abstract

Short-term changes in amino acid composition of near-bed particulate flux were studied at an upper shelf location in the southern Skagerrak, 55 m deep. Sediment trap samples were collected with a 3-d sampling interval from late April to late June 1992. A high settling rate (85 g m-2 d-1) was intercepted in May, coinciding with high shear velocity and settling of fresh phytoplankton. During the peak in the settling rate, a decrease in the mole percentage of glycine was noticed. At the end of June, smaller peaks of high flux corresponded to periods of increased shear velocity; during this time, the amino acid composition did not change. A Q-mode factor analysis on the amino acid variation of collected particles showed a relation between certain samples consisting of fresh phytoplankton material. If organic carbon is compared to the shear velocity, the related phytoplankton samples had a positive correlation, whereas the more degraded samples had a negative correlation. The observed patterns suggest a coupling between food web dynamics and particle composition on the one hand and availability of benthic fluff at the sediment surface on the other. The length of the period affected by fresh material could be sorted out by using the amino acid composition and be made comparable to samples influenced by more degraded material.