Long-Term Seagrass Decline and Spatial Reorganization of Blue Crabs in the Indian River Lagoon
Year: 2026
Type: preprint
Abstract: The Indian River Lagoon (IRL), one of North America’s most biodiverse estuarine systems, has undergone extensive ecological restructuring following widespread seagrass loss associated with nutrient enrichment, the 2011–2012 superbloom event, and recurrent harmful algal blooms. Because blue crabs ( Callinectes sapidus ) depend on structured and spatially continuous estuarine habitats during early development, we examined whether long-term habitat loss was associated with changes in the spatial organization of blue crabs across the lagoon. Using long-term fisheries-independent monitoring data from the Florida Fish and Wildlife Conservation Commission and seagrass survey data from the St. Johns River Water Management District, we quantified relationships among blue crab relative abundance, body size, habitat cover, and climatic variability. Long-term trends indicated overall declines in both summer seagrass percent cover and mean blue crab carapace width, although these changes were characterized by substantial temporal variability and marked shifts after 2011. Low bottom-vegetation cover habitats contained smaller and less abundant crabs than highly vegetated areas. Following the 2011–2012 seagrass decline, blue crab populations became increasingly spatially reorganized, with persistent low-density regions emerging in the northern region of the lagoon and areas of elevated blue crab relative abundance concentrated in the southern lagoon. Empirical orthogonal function analysis of long-term seagrass cover data showed that a single basin-wide mode explained 64.8% of habitat variability and corresponded with rainfall variability and regional climatic oscillations. Although local water-quality variables explained relatively little variation in blue crab abundance, blue crab abundance and size structure remained strongly associated with vegetated habitat availability. These findings suggest that seagrass loss and habitat restructuring were associated with large-scale spatial reorganization of blue crabs. Because movement among habitat patches was not measured directly, connectivity is interpreted here as the spatial continuity and persistence of vegetated nursery habitat rather than demographic or dispersal connectivity.
Source: Research Square
Authors: Jackson L. Evans, Hyun Jung Cho
Institution: Bethune-Cookman University
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
Award: G5693215407
OpenAlex ID: W7204835874