Ruby Schwartz 

Boca Ciega Bay, Florida has been impacted by dredge and fill deposition in response to the high demand for waterfront property and infrastructure. Dredge and fill deposition  significantly modifies coastal geography and can smother benthic organisms and alter habitats. To assess the ecological signature and impact of dredge and fill deposition, 12 sediment cores were taken along transects on the east and west sides of the Tierra Verde Bridge. Three cores were also collected from Indian Key as a control site. Mollusc shells (bivalves and gastropods) were recovered from 3 sediment cores, identified to the species level, and quantified -  adding to molluscan data already documented from 6 other cores. Assemblages in dredge and fill deposition intervals are characterized by lower diversity and abundance compared to pre- and post-dredge intervals. Species in dredge and fill deposition intervals also are less commonly found in seagrass environments, whereas those in the pre- and post-dredge intervals are characteristic of seagrass environments. Samples found within the suspected dredge and fill intervals are characterized by relatively high overall abundances of bivalves and gastropods and few fragile species. The diversity was lower in dredge intervals than non-dredge intervals. In contrast, species found in pre- or post-dredge deposition intervals are characterized by a more variable overall abundances. Species primarily found in seagrasses decrease in abundance during dredge and fill deposits. Preliminary conclusions reveal that species that thrive in seagrass habitats experience a decrease in diversity and abundance more than species that thrive in rocky or sandy habitats with the introduction of dredge and fill materials. 

For more information: raschwartz@eckerd.edu

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