Comparative survival of bay scallops in eelgrass and the introduced alga, Codium fragile, in a New York estuary

Abstract

Eelgrass, Zostera marina, is generally regarded as the preferred habitat of bay scallops, but in some cases scallop populations have persisted or increased in areas lacking eelgrass. This suggests that some other substrate(s) may serve important ecological functions for bay scallops. One candidate is Codium fragile, a macroalgal species with which bay scallops are known to associate and in which we commonly Wnd juvenile and adult bay scallops in eastern Long Island, New York. In this study, we examined whether survival of planted bay scallops diVered in Codium, eelgrass, and Codium + eelgrass substrates at two sites during August and October of 2 years. Survival of tethered scallops and recoveries of live free-planted individuals varied with scallop size, planting season and year, but no diVerences were observed between the three substrates for a given scallop size and planting date. Crab (particularly Dyspanopeus sayi) and whelk predation were implicated as important causes of tethered scallop mortalities while emigration and removal by predators likely contributed to scallop losses. Densities of naturally recruited 0+ years scallops recovered by visual and suction dredge sampling were similar in the eelgrass and Codium substrates. While our results suggest that Codium may oVer some degree of predation refuge for bay scallops, further work needs to weigh the potential disadvantages of this substrate (such as low DO levels, potential attachment and transport of scallops, and diVerences in current Xow, food availability and sedimentation relative to eelgrass) to determine if Codium may serve as a valuable habitat for bay scallops throughout their lifespan.

Utility of high-density plantings in bay scallop, Argopecten irradians irradians, restoration

“…Predators were those species/sizes of crabs, gastropods, or fish that had the potential to prey on the sizes of scallops that were present in the free-planted sectors (Tettelbach 1986;Carroll et al 2010).…”

Predator–prey interactions in a restored eelgrass ecosystem: strategies for maximizing success of reintroduced bay scallops (Argopecten irradians)

“…Argopecten irradians has several unique strategies throughout its life history for deterring predators. First, juveniles recruit to seagrass blades to distance themselves from benthic predators, prevent burial by sediments, and increase access to food (Ambrose & Irlandi ; Garcia‐Esquivel & Bricelj ; Bishop & Wear ; Carroll et al ). At 15–25 mm in shell height, A. irradians attain a size refuge from smaller benthic predators and move from the canopy to the sediment surface (Garcia‐Esquivel & Bricelj ).…”

The ability of macroalgae to mitigate the negative effects of ocean acidification on four species of North Atlantic bivalve

“…Despite the reported positive interactions between Ulva and the various species of bivalves in prior studies (Carroll et al, 2010;Heck et al, 2003;Sogard and Able, 1991;Wilson et al, 1990; this study), macroalgae can negatively impact bivalves and other calcifying organisms. Secondary metabolites released by Ulva can elevate mortality rates in the larval 5 stages of bivalves (Diederich, 2005;Nelson et al, 2003), barnacles (Brock et al, 2007;Magre, 1974), crabs (Johnson and Welsh, 1985), and molluscs .…”

“…This benefit was not 30 exclusive to acidified conditions, as evidenced by increased bivalve growth in the presence of Ulva within ambient CO2 treatments. While macroalgae can have adverse effects on some larval-staged bivalves, the chemical resilience provided by the macroalgae, Ulva, along with other potential ecosystem benefits such as providing nursery habitat (Wilson et al, 1990), predation refuge (Carroll et al, 2010), and inhibiting the growth of harmful microalgae (Tang and Gobler, 2011; 2015) may, in some case, outweigh the negative effects. Although seagrass meadows can also buffer carbonate chemistry to the benefit of bivalves and other calcifying organisms, their populations continue to display worldwide declines (Orth et al, 2006;Short et al, 2011).…”

“…Macroalgal beds can serve as an nursery habitat for juvenile Callinectes sapidus (Wilson et al, 1990), as well as other decapods (Heck et al, 2003;Sogard and Able, 1991). Macroalgae can also serve as a refuge from predation for some juvenile and adult bivalves (Carroll et al, 2010). An additional potential benefit provided to bivalves by Ulva and other 25 macroalgae is their ability to inhibit the growth of phytoplankton species that cause harmful algal blooms (HABs; Tang and Gobler, 2011;Tang et al, 2015) that can directly harm the bivalve species used in the present study (Gobler and Sunda, 2012;Leverone et al, 2006;Stoecker et al, 2008;Tang and Gobler, 2009).…”