Virginia Institute of Marine Science
Journal of Shellfish Research
In high salinity habitats along the Middle and South Atlantic coasts of the United States the Eastern oyster, Crassostrea virginica occupies an intertidal refuge from predation, facilitated by its tolerance of aerial exposure and associated desiccation and temperature stress. Observations of the Suminoe oyster, C. ariakensis in its native environments in Asia reveal that this species is most commonly found subtidally or in the very low intertidal zone, suggesting that it may be less tolerant of aerial exposure. With serious consideration being given to introducing C. ariakensis to the mid-Atlantic region, it is important to understand the ability of this non-native species to invade and become established in the intertidal zone. We conducted experiments in an outdoor quarantined facility to compare the tolerances of C. virginica and C. ariakensis to varying levels of aerial exposure. Diploid C. virginica and C. ariakensis were set on 10 cm x 10 cm PVC tiles, held in a flow-though quarantine system exposed to ambient weather conditions, and subjected for eight weeks to four simulated tidal emersion regimes-(1) high intertidal (3.5 h emersion), (2) mid intertidal (2 h emersion), (3) low intertidal (1 h emersion), and (4) subtidal (constant immersion)-and four exposure orientations-(1,2) vertical north- and south-facing, and (3,4) horizontal up- and down-facing. Complete mortality of both species occurred in the high intertidal treatment by the end of week 1. No C. ariakensis had survived in the mid intertidal treatment by week 2 and very few remained alive in the low intertidal treatment. By the end of week 5, only 1.25% of the C. ariakensis had survived in the low intertidal treatment, whereas survival of C. ariakensis in the subtidal treatment was 36.88%. Significantly, C. virginica survival was 80.63% in the subtidal treatment and 67.50% and 28.13% on the vertically-oriented tiles (north- and south-facing treatments combined) in the low intertidal and mid intertidal treatments, respectively. Growth rates of C. virginica across tidal treatments were greatest in the subtidal treatment and C. ariakensis grew faster in the subtidal treatment than C. virginica. These results indicate that even with modest aerial exposure, under climatic conditions characteristic of summers in the mid-Atlantic region of the United States, C. ariakensis would suffer high rates of early post-settlement mortality, effectively restricting this non-native oyster species to subtidal environments if introduced to the region.
exotic species, intertidal exposure
Kingsley-Smith, P.R. and Luckenbach, M.W., Post-settlement survival and growth of the Suminoe oyster, Crassostrea ariskensis, exposed to simulated emersion regimes (2008). Journal of Shellfish Research, 27(3), 609-608.