NEARSHORE ABUNDANCE OF ZOOPLANKTON IN RELATION TO SHORELINE CONFIGURATION AND MECHANISMS INVOLVED

Zooplankton abundance was examined in relation to shoreline configurat ion. Four embayments (0.15, 1.5, 4 and 7 km opening) were each divided into three zones, corresponding to regions inside, outside and downst ream. A portion of straight coast [similar to 12 km, Sainte-Flavie (SF )I was also divided into three zones. Only the largest embayment was s ampled in 1993, but all embayments and SF were sampled in 1994. In 199 3, zooplankton abundance was significantly higher within the embayment than in external zones for six of seven dates. Zones inside the four embayments had generally higher zooplankton abundance than zones exter nal to the embayments in 1994, but the opposite was observed during th e first of two sampling dates for the largest embayments. No definite pattern was observed among zones along SF. Four hypotheses could expla in the higher abundance of zooplankton inside embayments. Three were t ested using meroplankton (M)/holoplankton (H) ratios. The MM ratios co nfirmed hypotheses of retention and local production of meroplanktonic larvae inside embayments. Zooplankton abundance was lower inside than in zones external to embayments only twice, and wind direction may ha ve been responsible for these results. No embayment size effect on zoo plankton abundance was detected. The patchy distribution of zooplankto n may increase the difficulty of observing an effect of embayment size on zooplankton abundance.