Are oysters being bored to death? Influence of Cliona celata on Crassostrea virginica condition, growth and survival

Abstract

The boring sponge Cliona celata is a nuisance species that can have deleterious effects on eastern oyster Crassostrea virginica growth, condition, and survival. Surprisingly, however, these effects have not been well documented and when examined, results have been equivocal. In this study, we provide a direct comparison of growth, condition, and survival of spongecolonized and uncolonized oysters in southeast North Carolina in 2 separate experiments. In the first experiment, sponge-colonized oysters exhibited significantly slower growth rates, reduced condition, and lower survival relative to uncolonized oysters, although results may have been confounded by oyster source. In the second experiment, using smaller oysters from the same source population, growth rate was again significantly reduced in colonized oysters relative to uncolonized oysters, however neither condition nor survival differed. In field surveys of the same population, colonized individuals across a range of sizes demonstrated significantly reduced condition. Further, condition index was negatively correlated with sponge biomass, which was positively correlated with oyster size, suggesting that the impact of the sponge changes with ontogeny. By investigating clearance rates, tissue isotopic and nutrient content, as well as caloric value, this study provides further evidence that sponge presence causes the oysters to divert energy into costly shell maintenance and repair at the expense of shell and somatic growth. Thus, although variable, our results demonstrate negative impacts of sponge infestation on oyster demographics, particularly as oysters grow larger.

Reproductive and recruitment dynamics of clionaid sponges on oyster reefs in North Carolina

“…Only ~21% of oysters on local intertidal reefs are infected by boring sponge (Carroll et al. ), compared to ~100% infection in floating oyster cages (unpubl. data), and intertidal oysters in our study had fewer species of clionaids.…”

“…Prior to this study, little was known about the general species composition, reproduction, and recruitment for clionaids in this region, despite the potential detrimental impacts of boring sponges on oysters. Due to the negative impacts on both oyster reef restoration and aquaculture, there has been renewed and growing interest in examining clionaid-oyster interactions in this region (Dunn et al 2014;Carroll et al 2015).…”

“…One potential solution for oyster growers in this region is to use a rack-and-bag system of deployment, in which oysters are exposed daily during low tides. Only~21% of oysters on local intertidal reefs are infected by boring sponge (Carroll et al 2015), compared to~100% infection in floating oyster cages (unpubl. data), and intertidal oysters in our study had fewer species of clionaids.…”

“…Once inside the shell matrix, the sponge gradually takes over the oyster valves by creating a series of tunnels and chambers inside the shell material (Cobb 1975;Hoeksema 1983). This process not only weakens the shell, potentially making the oyster more vulnerable to predation, but also inhibits both shell and somatic growth as well as reproduction as the oyster expends energy trying to repair and rebuild its shell (Fromont et al 2005;Carroll et al 2015).…”

The invasive sun coral Tubastraea coccinea hosting a native Christmas tree worm at Curaçao, Dutch Caribbean

“…For example, the American slipper limpet Crepidula fornicata (Linnaeus, 1758) is an introduced host for the boring sponge Cliona celata Grant, 1826, and the digenean trematode Himasthla elongata (Mehlis, 1831) in the northeastern part of the Atlantic (Hoeksema 1983;Thieltges et al 2009), whereas both parasites also occur in their host's native range (Blakeslee et al 2011;Carroll et al 2015). Another example concerns ctenophores of the species Mnemiopsis leidyi Agassiz, 1865, which can become infested by parasitic larvae of the actiniarian genus Edwardsiella in the ctenophore's original native range along the North American east coast and also in its new, introduced range in northwestern Europe (Reitzel et al 2009;Selander et al 2010).…”