Recruitment pattern of benthic fauna on artificial substrates in brackish low-diversity system (the Baltic Sea)

Recruitment pattern of benthic fauna in temperate marine ecosystems is still not well recognized, particularly in inland coastal seas with distinct environmental and ecological conditions. This study investigates the effect of natural surrounding community structure, environmental variables and substrate orientation on short-term recruitment of motile and sessile epibenthos in the southern Baltic Sea. Recruitment on topsurface and undersurface of Perspex panels deployed on the seafloor in a horizontal position was monitored monthly from March 2008 to March 2010 in two coastal habitats (sandy and gravelly) in the Gulf of Gdańsk. Recruitment of epibenthic invertebrates took place primarily over a growing season (March–October) indicating that reproduction and settlement are driven by water temperature and gross primary production. Communities of recruits showed relatively homogenous spatial taxonomic composition but total epifaunal abundance varied between bottom types. Planktonic larvae supply and species-specific recruitment behaviour account primarily for settlement success, particularly on panel topsurface which hosted more diverse and more abundant recruits than panel undersurface. Relative to vertical substrates, horizontal panels had less numerous barnacle recruits probably due to inhibitory effect of sediment deposition and organic biofilm.