Fish diversity declines with loss of sessile benthic invertebrate density on nearshore hardbottom communities in the Florida Keys, United States

Abstract

Nearshore hardbottom communities are characterized by their invertebrate benthos, which provide food, habitat, and refuge for fish. Structural complexity supports greater species richness and abundance; thus, habitat degradation can reduce fish diversity and lead to a shift in community composition. Nearshore hardbottom communities in the Florida Keys, USA, have lost sessile benthic invertebrate diversity since the 1970s and the communities examined here have shifted from coral- and sponge-dominated to sponge- and algae-dominated. Two nearshore hardbottom communities (one oceanside site and one bayside) were surveyed from 1991 through 1996, and then were resurveyed in 2021 and 2022. Both communities experienced declines in fish richness, biodiversity, and trophic structure. Present-day fish species richness is approximately 30%–40% of what it was when surveying began in 1991. Sessile benthic invertebrate richness and density were correlated with fish richness and composition; the degradation of benthic communities appears to have negatively influenced fish assemblages. Diverse and abundant fish assemblages are key to healthy and productive coastal ecosystems; this loss of biodiversity will reduce the ecological functionality of nearshore hardbottom communities.