DOI: 10.25497/d7t591
title: RECOVER MAP 3.2.4.4 Oyster Reef Health in Pumpkin and Fakahatchee Estuaries: Baseline Monitoring for Ten Thousand Islands Restoration

description: Historical records indicate that oyster reefs were once significant features of the waters of the Atlantic Ocean and the Gulf of Mexico, at times presenting significant hazards to navigation (Cake 1983, Mann et al. 1996). Many Florida estuaries have previously supported a thriving oyster industry (Ingle & Whitfield 1968). Recent decades, though, have witnessed dwindling oyster populations throughout the Atlantic and Gulf coasts. For example, it has been estimated that at one time oysters could completely filter the water volume of Chesapeake Bay in only 3.3 days; current populations take more than a year to do so (Newell 1988). Similarly, records from Southwest Florida suggest that oyster growth and distribution has decreased drastically since the 1960s (Chamberlain & Doering 1998). Factors responsible for this overall decline may include overfishing and associated habitat destruction, a shortage of suitable substrate, disturbances such as dredging, reduced water and habitat quality, alteration of natural water flow and salinity patterns, natural and introduced predators, and disease (Coen et al. 1999a, Lenihan et al. 1999, Volety et al. 2000).
The protozoan parasite Perkinsus marinus has devastated oyster populations in the Atlantic (Burreson & Ragone-Calvo 1996), where it is the primary pathogen of oysters, as well as in the Gulf of Mexico (Soniat 1996). Andrews (1988) estimated that P. marinus can kill ~80% of the oysters in a bed. The distribution and prevalence of P. marinus is influenced by temperature and salinity with higher values favoring the disease organism (Burreson & Ragone-Calvo 1996, Soniat 1996, Chu & Volety 1997). Field and laboratory studies indicate that P. marinus exerts severe pressure on growth, survival, and energy reserves of oysters, thereby limiting reproduction and recruitment (Paynter & Burreson 1991, Volety & Chu 1994, Volety et al. 2000). Extensive research has been conducted on various aspects of physiology, biochemistry, reproduction, and recruitment (see Kennedy et al. 1996) in the eastern oyster (Crassostrea virginica); however, oyster growth, reproduction, recruitment, and survival depend on a multitude of complex, interacting, local factors such as substrate, estuarine circulation, food availability, temperature, salinity, and genetics (e.g., Kennedy & Boicourt 1981, Livingston et al. 2000). Few studies from Southwest Florida have examined oyster health, survival, or the prevalence of P. marinus in relation to environmental factors and water quality (Quick & Mackin 1971, Christensen et al. 1998). Our research to date on oyster reef development and oyster productivity within human-altered watersheds within the Ten Thousand Islands of Southwest Florida suggests that watershed alteration influences patterns of oyster recruitment and growth as well as of oyster-reef distribution (Savarese & Volety 2001a,b, Volety et al. 2001, Savarese et al. 2002, Savarese et al. 2004). For example, estuaries presently receiving more freshwater than the natural pre-alteration conditions allowed (e.g., Faka Union estuary downstream of South Golden Gate Estates) have fewer oyster reefs, lower living oyster densities, and greater mortality of young oysters than do relatively pristine, neighboring estuaries. Our research in the Caloosahatchee Estuary suggests that both organism abundance and density vary spatially within the estuary, with higher values occurring upstream, at lower salinities (Tolley et al. 2002a, b). Highest organism abundances occur at sites with greater densities of living oysters. In contrast, species diversity and richness are greater downstream at higher salinities.
In addition to salinity effects, oyster distribution, growth, and reproduction are affected by water flow. Oysters require swift moving currents to acquire food and for the distribution of gametes and larvae (Carriker 1951, 1986, Wood & Hargis 1971, Kennedy 1996). Reefs typically form in regions of an estuary that not only have the most desirable salinity, but also are exposed to strong tidal currents (Kennedy 1996, Shumway 1996). Anecdotal evidence suggests that oyster reef location (i.e., immediately up- or downstream from an estuarine flow-way constriction) and shape (i.e., with the long axis perpendicular to flow direction) are dictated by tidal flows (Savarese unpublished data). Unfortunately, this is one aspect of reef distribution that has not been explored in Southwest Florida. Appropriate water quality (e.g., salinity) and flow regime both must be considered when assessing estuarine health and when planning estuarine restoration projects (Volety et al. 2003). The Southwest Florida community of estuarine scientists and managers has recognized the significance of our research findings by establishing oyster health and reef productivity as measures of performance of estuarine restoration for numerous watersheds throughout the Big Cypress Basinâ s jurisdiction. The Natural Systems Group of the Southwest Florida Feasibility Study has adopted our oyster performance measures for efforts in the Ten Thousand Islands, Henderson Creek, and Estero Bay. Ten Thousand Islands restoration has begun through the authorization of the Picayune Strand Restoration Project. As presently defined in the Picayune Project Implementation Report, three estuaries will be affected by restoration. Resumption of sheet flow will increase freshwater delivery to Blackwater and Pumpkin Bay estuaries and eliminate the freshwater point-source pollution in Faka Union. A fourth estuary, Fakahatchee Bay, sits just east of the effects of South Golden Gate Estates (SGGE) water management and, consequently, has remained relatively pristine. The PIR established Fakahatchee as the control estuary, against which all performance measures should be compared. We already have baseline data on the state of oyster reefs in Blackwater and Faka Union estuaries, however, at the onset of this project, we had no information about the state of oyster health and reef productivity for Pumpkin and one year of observations for Fakahatchee. This research endeavor fills this gap in understanding of the effects on oyster health in Pumpkin and Fakahatchee Estuaries. For oyster health and reef productivity to be an effective performance measure of Picayune restoration, additional baseline data were needed for Fakahatchee to better understand the environmental state of the control and for the characterization of oyster reefs in Pumpkin. The study of the effects of watershed management upon oyster health is critical to understanding the functioning of the estuarine ecosystem of Southwest Florida and future planning from restoration projects.