Rebuilding A Collapsed Bivalve Population, Restoring Seagrass Meadows, and Eradicating Harmful Algal Blooms In A Temperate Lagoon Using Spawner Sanctuaries

Abstract

During the past century, bivalve populations across the globe have collapsed, resulting in negative ecosystem consequences due to their outsized impact on shallow estuaries. In response, there has been strong interest in the restoration of marine bivalve populations. Here, we present a decade-long restoration effort that sought to rebuild a collapsed (99.5% reduction in harvest) and recruitment-limited population of hard clams (Mercenaria mercenaria) in Shinnecock Bay, NY, USA, using spawner sanctuaries: no-harvest zones where adults were planted at high densities (~27 m-2). Between 2012 to 2019, more than 3.2 million clams were planted in 64 discrete sanctuary plots (~1,850 m2 each) located in zones with maximal larval retention and sediment and seawater characteristics that would maximize the conditioning and spawning of adults. Hydrodynamic models, quantification of hard clam larvae, and spatial recruitment patterns demonstrated larvae spawned within sanctuaries were transported to regions where clam densities significantly increased 18-fold over seven years (2015-2021; p<0.001) and harvests significantly increased more than 16-fold over nine years (2012-2021; p<0.0001). Increases in populations and harvests were caused by smaller clams recruited within the time frame of the creation of spawner sanctuaries. Higher clam densities caused biological filtration times of the bay to decrease from up to three months at the start of the project to as low as 10 days in 2021. Concurrently, concentrations of the harmful brown tide alga, Aureococcus anophagefferens, and chlorophyll a significantly decreased (p<0.005) while water clarity and the extent of seagrass beds significantly increased (p<0.05). Increases in clam landings and improvements in water quality were not observed in adjacent lagoonal estuaries where restoration did not occur. Given these outcomes and the global need for rebuilding marine life, the implementation of spawner sanctuaries using the criteria set forth herein may be a promising approach for restoring hard clam and other bivalve populations in estuaries elsewhere.

Warming and hypoxia reduce the performance and survival of northern bay scallops (Argopecten irradians irradians) amid a fishery collapse

“…These drivers, however, can also transform habitats and ecosystems in ways that harm fisheries, even if not as direct “stressors,” for instance via the promotion of harmful algal blooms (Díaz et al, 2019; Gobler et al, 2017; Griffith et al, 2019), the loss of seagrass habitat (Nyström et al, 2012; Strydom et al, 2020), or increased impacts of disease (Ford & Chintala, 2006; Pearce & Balcom, 2005). While climate change mitigation will require a global effort, identifying pathways toward the recovery of highly impacted hypoxic systems (Conley et al, 2009; Gobler et al, 2022; Steckbauer et al, 2011) may benefit vulnerable fisheries.…”

Oyster reefs' control of carbonate chemistry—Implications for oyster reef restoration in estuaries subject to coastal ocean acidification

“…In both Sedge and Quogue regions, a neighboring control site (50 m distance from reefs; SC and QC respectively) was also identified and monitored to provide measures of ambient seawater to be compared to reef‐modified seawater (Figure S1). Control locations were intentionally sited near to the outer edge of the reefs and were not proximate to any special features (i.e., inlets, freshwater inputs, or bathymetric features) that might create artificial biogeochemical differences unassociated with the reefs (Gobler et al, 2022; NOAA, 2020; USACE, 2004). Previous research and investigation during the reef permitting process also indicated no differences in water quality or sediment types between the reef sites and their respective control sites prior to the installation of the reefs (NYSDEC, 2017; Psuty & Silveira, 2009).…”

“…Shinnecock Bay is a 39 km 2 shallow tidal lagoon on the south shore of Long Island, NY, USA (Figure S1) that since the 1970s experienced declines in water quality, seagrass cover, and shellfisheries, coincident with intensifying eutrophication (Gobler & Sunda, 2012;NYSDEC, 1970NYSDEC, -2020NYSDEC, , 2009Weiss et al, 2007). Reef restoration is one component of a multidimensional restoration effort that began in 2012 and aims to improve water quality and reestablish bivalve shellfisheries by establishing hard clam spawner sanctuaries, planting eelgrass, harvesting aquacultured seaweeds, and constructing remotely set subtidal reefs (Gobler et al, 2022). (Callam & Supan, 2018) in multiple large 2000-L tanks filled with mesh bags (57 cm × 24 cm) of air-cured surf clam shell at the Stony Brook-Southampton Marine Lab.…”

Density‐dependent influence of ribbed mussels on salt marsh nitrogen pools and processes

“…For instance, blue mussel ( Mytilus edulis ) farming operations are considered cost‐effective measures for nutrient extraction and water clarity enhancement in the Baltic Sea (Gren et al., 2009; Kotta et al., 2020; Lindahl et al., 2005; Schröder et al., 2014). Bivalve‐mediated N regulation may be particularly important in vegetated coastal ecosystems, such as salt marshes, mangrove forests, and seagrass meadows, where synergistic interactions between bivalve populations and macrophytes may govern N sequestration pathways (Gagnon et al., 2020; Gobler et al., 2022). As applications of bivalve bioremediation grow, new calls to evaluate how bivalve densities modify N pools and processes across multiple scales have surfaced (Kellogg et al., 2014; Testa et al., 2015).…”