Influence of shoreline configuration on spatial variation of meroplanktonic larvae, recruitment and diversity of benthic subtidal communities

Recruitment, abundance (percentage cover, density) and diversity (H') of a benthic subtidal community were examined in relation to large scale (greater than or equal to 0.15 km) shoreline configuration in the St. Lawrence Estuary (Canada). Settlement panels were moored inside and outside bays of different sizes (0.15, 1.5, 4 and 7 km aperture) and along a portion of straight (approximate to 12 km) coast. Only the largest bay was sampled in 1993, while all bays and the straight coast were sampled in 1994. In 1993, recruitment occurred only within the bay. No recruits were observed on moored panels from zones external to the bay. Within the bay, percentage cover on panels was greater than in zones external to the bay. In 1994, percentage cover and the density of recruits were also greater within each bay than outside bays. No differences in diversity, percentage cover and density of recruits were observed among zones along the straight coast. Diversity was greater in bays than along the straight coast and was greater inside bays of 1.5 and 7 km aperture than in zones external to the bays. Overall, diversity tended to increase with increasing size of bay, the straight coast exhibiting the smallest values, in contrast, the density of recruits and percentage cover tended to decrease with increasing size of bay; smallest values were from the straight coast. Abundance of recruits was not directly related to potential larval flux; current velocity alone explained 76% of the variation in density of recruits inside and outside of bays. Our study shows a relationship between shoreline configuration, the hydrodynamics, recruitment and benthic community characteristics. The generality of this relationship can be assessed by carrying out similar large-scale studies in other systems. (C) 1999 Elsevier Science B.V. All rights reserved.