Siltation increases the susceptibility of surface-cultured eastern oysters (Crassostrea virginica) to parasitism by the mudwormPolydora websteri

Abstract

Mudworm (Polydora websteri) parasitism is known to result in unsightly mud blisters in eastern oysters (Crassostrea virginica), resulting in reduced product quality and increased vulnerability to illness and environmental stress. While typically a concern only for bottom-grown oysters, an abnormal severe outbreak of P. websteri in surface-cultured oysters in New Brunswick, Canada, was reported in 2013, along with an anecdotally reported concurrent increase in siltation. Although heavier loads of silt are reported to increase P. websteri infestations in oysters, studies report mixed effects of siltation to this regard. Here, we report the results of a field experiment testing the effect of siltation on P. websteri recruitment in surface-grown oysters at an aquaculture site in Richibucto, New Brunswick. Live oysters of similar size were deployed at the aquaculture site and were left to collect P. websteri recruits under one of two siltation treatments (high vs. low) for 50 days. Results suggested that P. websteri recruitment correlated with metrics of oyster size (shell weight, length, width, depth and surface area). When P. websteri counts were standardized for oyster shell morphometry, P. websteri recruitment was significantly higher in oysters exposed to the high siltation treatment, accumulating approximately 1.59 as many P. websteri as oysters exposed to the low siltation treatment. Our results suggest that higher amounts of siltation on surface-cultured oysters can result in increased rates of P. websteri parasitism. Enhanced cleaning regimes may help to alleviate the impacts of P. websteri in surface-grown oysters, although other mitigation strategies exist.

Confirmation of the shell-boring oyster parasite Polydora websteri (Polychaeta: Spionidae) in Washington State, USA

“…The prevalence of Polydora websteri is sensitive to environmental change. For example, increasing siltation can increase the susceptibility of Crassostrea virginica to Polydora websteri 69 . In contrast, reducing pH actually decreases susceptibility to infestation 70 .…”

Spread of the invasive shell-boring annelid Polydora websteri (Polychaeta, Spionidae) into naturalised oyster reefs in the European Wadden Sea

“…For instance, the cultured oysters are kept on trestles about 0.35 m above the surface (Reise 1998), and it is known that tidal exposure reduces the infestation with P. websteri (Littlewood et al 1992;Handley and Bergquist 1997). Furthermore, a lower siltation, which is probably caused by the regular manual turning of the oyster mesh bags to prevent oysters from cementing together, also reduces infestation success of the polychaetes (Clements et al 2017). However, given that the polychaete is considered a serious pest in commercial marine aquaculture in other regions around the globe (Whitelegge 1890;Lunz 1941;Loosanoff and Engle 1943;Bailey-Brock and Ringwood 1982;Ogburn et al 2007), further investigations on the spread and population development of P. websteri are warranted.…”

Extreme ocean acidification reduces the susceptibility of eastern oyster shells to a polydorid parasite

“…The alternative shell features may also have been differentially affected between larger and smaller shells due to shell legacy (Waldbusser et al 2011a,b), potentially owing to the weak relationships between worm counts and shell morphometrics that are in contrast with other studies (e.g. Clements et al 2017).…”