4.7 Article

Siltation negatively affects settlement and gaping behaviour in eastern oysters

Journal

MARINE ENVIRONMENTAL RESEARCH
Volume 170, Issue -, Pages -

Publisher

ELSEVIER SCI LTD
DOI: 10.1016/j.marenvres.2021.105432

Keywords

Crassostrea virginica; Larval settlement behaviour; Population recruitment; Turbidity; Shellfish aquaculture; Spat collector

Funding

  1. Fisheries and Oceans , Atlantic Science Enterprise Centre (ASEC)
  2. Mount Allison University Independent Student Research Grant (ISRG)

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The study found that sediment negatively affected oyster spat settlement on bottom shell, with spat densities being significantly lower when sediment was present, especially on the upper side of bottom shells. The behavior of wild adult oysters was also negatively affected by acute burial, leading to eventual death. The reduction in settlement in the presence of siltation is likely due to the combined effects of suspended sediment on cue detection and bedded sediment on substrate availability, which can have cascading effects on the surrounding biological community as oysters are ecosystem engineers.
While high levels of siltation are known to be deleterious to eastern oysters (Crassostrea virginica), the collective effect of suspended and bedded sediment is understudied from the perspective of oyster farming and bed restoration. In this study, we used laboratory experiments to explore spat settlement rates on a wild bed proxy substrate (i.e., empty shells on the bottom of experimental tanks) in conditions simulating a siltation event and the presence of suspended spat collectors. Using high-frequency valvometry, we also described the behavioural effects of acute sediment burial on wild adult oysters in situ. The vast majority of larvae settled on bottom substrate as opposed to suspended collectors. Sediment negatively affected overall oyster spat settlement on bottom shell, as spat densities were approximate to 3 x lower when sediment was present. This negative effect was largely attributed to severely depressed spat densities on the upper side (top) of bottom shells. Settlement on the un-derside of bottom shell was less affected. Wild adult oyster behaviour was negatively affected by acute burial, which ultimately resulted in death. We suggest that the reduction in settlement in the presence of siltation is likely due to the combined effects of suspended sediment on cue detection and bedded sediment on substrate availability. Given that oysters are ecosystem engineers, the negative effects of siltation on both larval and adult oysters can ultimately result in cascading effects to the surrounding biological community.

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