COS 57-3 - Long-term monitoring data reveal differing species responses to habitat, interactions, and spatial structure in an estuarine metacommunity

Abstract: Estuarine systems are dynamic landscapes composed of various habitats that span several ecologically relevant environmental gradients. Because of the diversity of habitats and ecosystem functions that estuaries provide, many freshwater, marine, and euryhaline species rely on estuarine systems at some point in their life history. Four major processes can affect the composition of estuarine metacommunities over space and time: 1) species sorting among preferred habitats at local and regional scales; 2) direct and indirect interactions among species; 3) species dispersal across life stages; and 4) stochastic variability resulting in ecological drift. To date, much of the research on estuarine metacommunities has focused on a subset of these four processes Ecosystem models can integrate these processes to test hypotheses related to ecosystem structure and function, but typically rely on simulated ecosystems based on broad-stroke estimates of how each affects community assembly. Recent developments in joint species distribution modeling (JSDM) have allowed for a more empirical investigation of the relative effects of local and regional factors that influence metacommunities over space and time.

The Fisheries-Independent Monitoring program of the Florida Fish and Wildlife Conservation Commission has collected almost 30 years of continuous community data across various Florida estuaries. This dataset provides a unique opportunity to investigate the processes that structure estuarine metacommunities. Using the Hierarchical Modeling of Species Communities (HMSC; Ovaskainen et al. 2017) JSDM framework, we modeled the relative influences of habitat, species co-occurrence, spatial structure as a proxy for dispersal, and stochastic variability on sub-adult and adult fish communities across seven estuaries over a 25-year period spanning 1996-2020. Per-species model fit ranged from near 0 to 0.72. Fit was generally highest in common species and lowest in rare species. Habitat explained a diverging proportion of variation across species and was generally higher for common species. The effect of spatial structure was greater for common species than for uncommon ones. Residual species co-occurrence explained a negligible amount of variation across all species. The relatively high effect of habitat on species occurrence and abundance suggests that preservation of diverse habitats is key for maintenance of estuarine biodiversity. By identifying the relative influences of local and regional factors affecting estuarine metacommunities, we can better understand the major processes that influence the distribution and abundance of estuarine species. This can lead to better predictions of estuarine ecosystem change under various future habitat and climate scenarios.