Benthic Invertebrate Diversity in Coastal Ecosystems of the Florida Keys: A History of Anthropogenic Stressors Push Lower Diversity and Affect Ecosystem Function

Coastal ecosystems globally are facing unparalleled alterations from the growing human populations along the coasts. Coastal ecosystems in the very nearshore areas are particularly vulnerable to human-induced stressors.  In this study, the nearshore benthic communities of the Florida Keys are used as a model system to examine how chronic eutrophic conditions have altered the benthic community composition over the past two decades. Benthic sampling used the point intercept method and was conducted at thirteen study sites across the Florida Keys to describe the benthic composition. The benthic data collected were coupled with water quality data collected simultaneously. The natural community composition was described using the Coastal and Marine Ecological Classification Standard. The emergence of novel benthic communities and the occurrence of phase shifts from invertebrate- and seagrass- to algae-dominated communities were described. To further investigate the loss of invertebrates within the benthic communities and the respective role of water quality, stony corals were examined as a model system. The study sites with coral present were significantly different in the mean values for most of the water quality and nutrient parameters when compared to the study sites that were complete devoid of stony corals. These results suggested that water quality has played a role in the distribution of nearshore stony corals. Finally, a past study of two nearshore hard bottom communities in the middle Florida Keys from 1989 to 1996 was compared to repeated sampling in 2021 to understand how the long-term change of benthic invertebrate distribution has altered the structure of natural communities. The findings of this research suggested that despite years of intensive resource management in the Florida Keys, benthic diversity in being lost. A management transition from protected area-based management to ecosystem-based management to incorporate ecologically meaningful protection of nearshore water quality was suggested.