Oysters & Shellfish



Grizzle, R.E., A. Rasmussen, A.J. Martignette, K. Ward, and L.D. Coen. 2018. Mapping seston depletion over an intertidal Eastern Oyster (Crassostrea virginica) reef: implications for restoration of multiple habitats. Estuarine, Coastal and Shelf Science 212:265–272.

Research on the effects of bivalve filtration emphasizing oysters has mainly involved extrapolations from laboratory based measurements on individual oysters to potential whole-ecosystem impacts, with only a few studies on reef-scale processes and less using direct measurements. This study characterized spatial effects of whole-reef (oysters, Crassostrea virginica, and other filter feeders on the reef) filtration in the water immediately above and adjacent to a small (300 m2) intertidal reef in Tarpon Bay, Sanibel, Florida. Changes in water column parameters were measured in 2010 (chlorophyll a only) and 2013 (chlorophyll a and turbidity) by slowly paddling a kayak back-and-forth across the reef while logging position and water data. Although oysters were the dominant filter feeder, mussels, slipper shells, sponges, and a filter-feeding crab also occurred on the reef. Ambient water flow speed and direction were concurrently determined in 2013 by an acoustic-doppler current profiler. Measurements were made on two days (1–2 June) in 2010, and two days (November 15 and December 9) in 2013. ArcGIS software was used to plot the data and construct two-dimensional maps showing changes in chlorophyll a and turbidity, which clearly indicated the spatial extent of decreases in both as water flowed across the reef. Seston decrease (interpreted as depletion) levels were spatially variable, averaging 23–25% but as high as 68% in some areas directly over the reef. The extent of detectable depletion usually extended 10–20 m beyond the edge of the reef, potentially increasing light levels and thereby providing enhanced growth conditions for adjacent seagrasses and algae, suggesting that restoration success of macrophyte habitats could be enhanced by close spatial coupling with oyster reef restoration.


Beck, M.W., R.D. Brumbaugh, L. Airoldi, A. Carranza, L.D. Coen, C. Crawford, O. Defeo, G.J. Edgar, B. Hancock., M.C. Kay, H.S. Lenihan, M.W. Luckenbach, C.L. Toropova, G. Zhang, and X. Guo. 2011. Oyster reefs at risk and recommendations for conservation, restoration and management. BioScience 61:107–116.

Native oyster reefs once dominated many estuaries, ecologically and economically. Centuries of resource extraction exacerbated by coastal degradation have pushed oyster reefs to the brink of functional extinction worldwide. We examined the condition of oyster reefs across 144 bays and 44 ecoregions; our comparisons of past with present abundances indicate that more than 90% of them have been lost in bays (70%) and ecoregions (63%). In many bays, more than 99% of oyster reefs have been lost and are functionally extinct. Overall, we estimate that 85% of oyster reefs have been lost globally. Most of the world's remaining wild capture of native oysters (> 75%) comes from just five ecoregions in North America, yet the condition of reefs in these ecoregions is poor at best, except in the Gulf of Mexico. We identify many cost-effective solutions for conservation, restoration, and the management of fisheries and nonnative species that could reverse these oyster losses and restore reef ecosystem services.


Hadley, N.H., M. Hodges, D.H. Wilber, and L.D. Coen. 2010. Evaluating intertidal oyster reef development in South Carolina using associated faunal indicators. Restoration Ecology 18(5):691–701. 

Eastern oyster (Crassostrea virginica) habitat is increasingly being restored for the ecosystem services it provides rather than solely as a fishery resource. Communitybased projects with the goal of ecological restoration have successfully constructed oyster reefs; however, the habitat benefits of these restoration efforts are usually not assessed or reported. In this study, we examined oyster habitat development at five communitybased oyster restoration sites in South Carolina using oyster population parameters, resident fauna densities, and sedimentation (percent sediment coverage) as assessment metrics. All sites included multipleaged reefs (1–3 years old) at the time of the fall 2004 sampling. Resident crabs and mussels were abundant at all five sites and crab assemblages were related to the size structure of the oyster microhabitat. Scorched mussel (Brachidontes exustus) abundances were most frequently correlated with oyster and other resident species abundances. Associations among oysters and resident crabs and mussels were not evident when analyses were conducted with higher level taxonomic groupings (e.g., total number of crabs, mussels, or oysters), indicating that specieslevel identifications improve our understanding of interactions among reef inhabitants and oyster populations. Communitybased restoration sites in South Carolina provide habitat for mussels and resident crabs, in some cases in the absence of dense populations of relatively large oysters. Monitoring programs that neglect specieslevel identifications and counts of mussels and crabs may underestimate the successful habitat provision that can arise independent of large, dense oyster assemblages.


Brumbaugh, R.D., and L.D. Coen. 2009. Contemporary approaches for small-scale oyster reef restoration to address substrate versus recruitment limitation: a review and comments relevant for the Olympia Oyster, Ostrea lurida (Carpenter, 1864). Journal of Shellfish Research 28:1–15.

Reefs and beds formed by oysters such as the Eastern oyster, Crassostrea virginica and the Olympia oyster, Ostrea lurida Carpenter 1864† were dominant features in many estuaries throughout their native ranges. Many of these estuaries no longer have healthy, productive reefs because of impacts from destructive fishing, sediment accumulation, pollution, and parasites. Once valued primarily as a fishery resource, increasing attention is being focused today on the array of other ecosystem services that oysters and the reefs they form provide in United States coastal bays and estuaries. Since the early 1990s efforts to restore subtidal and intertidal oyster reefs have increased significantly, with particular interest in small-scale community-based projects initiated most often by nongovernmental organizations (NGOs). To date, such projects have been undertaken in at least 15 US states, for both species of dominant native oysters along the United States coast. Community-based restoration practitioners have used a broad range of nonmutually exclusive approaches, including: (1) oyster gardening of hatchery-produced oysters; (2) deployment of juvenile to adult shellfish (“broodstock”) within designated areas for stock enhancement; and (3) substrate enhancement using natural or recycled man-made materials loose or in “bags” designed to enhance local settlement success. Many of these approaches are inspired by fishery-enhancement efforts of the past, though are implemented with different outcomes in mind (ecological services vs. fishery outcomes). This paper was originally presented at the first West Coast Restoration Workshop in 2006 in San Rafael, California and is intended to summarize potential approaches for small-scale restoration projects, including some emerging methods, and highlight the logistical benefits and limitations of these approaches. Because the majority of the past efforts have been with C. viriginica, we use those examples initially to highlight efforts with the intent of enlightening current west coast United States efforts with Ostrea lurida. We also discuss site-specific characteristics including “recruitment bottlenecks” and “substrate limitation” as criteria for identifying the most appropriate approaches to use for small-scale restoration projects. Many of the included “lessons-learned” from the smaller-scale restoration projects being implemented today can be used to inform not only large-scale estuary wide efforts to restore C. virginica, but also the relatively nascent efforts directed at restoring the United States west coast's native Olympia oyster, Ostrea lurida.


Grizzle, R.E., J.K. Greene, and L.D. Coen. 2008. Seston removal by natural and constructed intertidal eastern oyster (Crassostrea virginica) reefs: a comparison with previous laboratory studies, and the value of in situ methods. Estuaries and Coasts 31:1208–1220.

An important ecological role ascribed to oysters is the transfer of materials from the water column to the benthos as they feed on suspended particles (seston). This ecosystem service has been often touted as a major reason for many oyster restoration efforts, but empirical characterization and quantification of seston removal rates in the field have been lacking. Changes in chlorophyll a (chl a) concentrations in the water column were measured in May 2005 and June 2006 in South Carolina using in situ fluorometry and laboratory analysis of pumped water samples taken upstream and downstream as water flowed over natural and constructed intertidal oyster reefs. Both methods gave similar results overall, but with wide variability within individual reef datasets. In situ fluorometer data logged at 10 to 30-s intervals for up to 1.3 h over eight different reefs (three natural and five constructed) showed total removal (or uptake) expressed as % removal of chl a ranging from −9.8% to 27.9%, with a mean of 12.9%. Our data indicate that restored shellfish reefs should provide water-quality improvements soon after construction, and the overall impact is probably determined by the size and density of the resident filter feeder populations relative to water flow characteristics over the reef. The measured population-level chl a removal was converted to mean individual clearance rates to allow comparison with previous laboratory studies. Although direct comparisons could not be made due to the small size of oysters on the study reefs (mean shell height, 36.1 mm), our calculated rates (mean, 1.21 L h−1) were similar to published laboratory measured rates for oysters of this size. However, the wide variability in measured removal by the oyster reefs suggests that individual oyster feeding rates in nature may be much more variable than in the laboratory. The proliferation of ecosystem-level models that simulate the impacts of bivalves on water quality based only on laboratory-feeding measurements underscores the importance of further research aimed at determining ecologically realistic feeding rates for oysters in the field. Because in situ methods provide many replicate measurements quickly, they represent a potentially powerful tool for quantifying the effects of oyster reefs, including all suspension-feeding taxa present, on water quality.


Coen, L.D., R.D. Brumbaugh, D. Bushek, R. Grizzle, M.W. Luckenbach, M.H. Posey, S.P. Powers, and G. Tolley. 2007. AS WE SEE IT. A broader view of ecosystem services related to oyster restoration. Marine Ecology Progress Series 341:303–307.

The importance of restoring filter-feeders, such as the Eastern oyster Crassostrea virginica, to mitigate the effects of eutrophication (e.g. in Chesapeake Bay) is currently under debate. The argument that bivalve molluscs alone cannot control phytoplankton blooms and reduce hypoxia oversimplifies a more complex issue, namely that ecosystem engineering species make manifold contributions to ecosystem services. Although further discussion and research leading to a more complete understanding is required, oysters and other molluscs (e.g. mussels) in estuarine ecosystems provide services far beyond the mere top-down control of phytoplankton blooms, such as (1) seston filtration, (2) benthic–pelagic coupling, (3) creation of refugia from predation, (4) creation of feeding habitat for juveniles and adults of mobile species, and for sessile stages of species that attach to molluscan shells, and (5) provision of nesting habitat.


Books, Reports, & Symposia


Thompson, M., and R. Bartleson 2020. Second Year Monitoring Update for Constructed Oyster Reefs, Spring Creek Oyster Mitigation Plan. Submitted to Coastal Engineering Consultants Incorporated. March 2020. SCCF Marine Laboratory. Sanibel, FL.


Thompson, M.A., and R. Bartleson. 2019. First year monitoring update for the constructed oyster reefs in Estero Bay for the Spring Creek Oyster Mitigation Plan. Submitted to Coastal Engineering Consultants Incorporated by SCCF Marine Laboratory. SCCF Marine Laboratory. Sanibel, FL.


Birch, A., E.C. Milbrandt, M. Thompson, T. Reis, and K. Radabaugh. 2017. Southwest Florida Oysters. In Oyster Integrated Mapping and Monitoring Program, FWC Publication, 30 pp.


Milbrandt, E.M., R.D. Bartleson, and M.A. Thompson. 2017. Restoration of oysters and submerged aquatic vegetation in the Caloosahatchee Estuary. Final Report to Florida Dept. of Env. Protection. 121 pp. 


Thompson, M.A., E.C. Milbrandt, R. Grizzle, L. Coen, and R.D. Bartleson. 2014. Long term monitoring of a community-based oyster reef restoration project in Clam Bayou, Southwest Florida. Charlotte Harbor Watershed Summit, March 25–27, 2014, Punta Gorda, FL.

Milbrandt, E.C., and R. Grizzle. 2013. Benthic Offshore. In Integrated Conceptual Ecosystem Model Development for the Southwest Florida Shelf Coastal Marine Ecosystem. W.K. Nuttle and P.J. Fletcher (eds.). NOAA Technical Memorandum, OAR‑AOML‑102 and NOS‑NCCOS‑162. Miami, Florida. pp. 79–85.


Thompson, M.A., E. Milbrandt, R.E. Grizzle, L. Coen, R.D. Bartleson. 2013. Long Term Monitoring of a Community-Based Oyster Reef Restoration Project in a Recently Modified, Substrate-Limited Southwestern Florida Embayment. 2013 Benthic Ecology Meeting, Savannah GA.


Milbrandt, E.C., M. Thompson, L. Coen, R.E. Grizzle, K. Ward, and S. Lartz. 2012. Community-based restoration of oyster habitat: a project to evaluate its success, associated effects on water quality and seagrass health in a recently modified, substrate-limited southwestern Florida embayment. Report submitted to The Nature Conservancy and The National Oceanographic and Atmospheric Administration. SCCF Marine Laboratory, Florida Atlantic University, University of New Hampshire. 


Volety, A.K., N. Martin, A. Griffith, R. Bartleson, and R. Pierce. 2012. Bioaccumulation and persistence of brevetoxins in oysters Crassostrea virginica following a red tide outbreak in southwest Florida, United States. SETAC North America 33rd Meeting, 11/11/2012 Long Beach, CA.


Coen, L.D., B.R. Dumbauld, and M.L. Judge. 2011. Expanding shellfish aquaculture: a review of the ecological services provided by and impacts of native and cultured bivalves in shellfish-dominated ecosystems. In Shellfish Aquaculture and the Environment, S.E. Shumway, Ed., Wiley-Blackwell. 528 pp.


Bartleson, R.D., L. Coen, E. Estevez, V. Kennedy, and J. Leal. 2010. Die-off of brackish water clams in the Caloosahatchee River, summer 2009: possible contributing factors. Florida United Malacologists Meeting, Sanibel, FL January 2010.



Click here to download a full list of SCCF Publications.