Seascape genomics of eastern oyster (
            Crassostrea virginica
            ) along the Atlantic coast of Canada

A survey of 16 enzyme systems and two structural proteins, among nine eastern oyster (Crassostrea virginica) populations in and adjacent to Laguna Madre, Texas, identified two genetically differentiated groups and the transition zone between them. The discontinuity in allele frequencies occurred between a reef in Corpus Christi Bay and reefs 26 km away in upper Laguna Madre. Although no fixed allelic differences were observed between populations from either side of the transition area, substantial frequency differences were observed at six gene loci, and both groups exhibited unique alleles. Spatial heterogeneity tests also suggested sizable allele frequency differences, as 8 of 15 polymorphic loci surveyed exhibited heterogeneity. Considerable genetic subdivision was observed, as 14 of 15 polymorphic loci surveyed exhibited significant fixation indices. The mean genetic similarity was 0.898 (range 0.813–0.977). Consequently, oysters inhabiting the Laguna Madre are genetically divergent from oysters inhabiting central and eastern Texas, the north-central and eastern Gulf of Mexico, and the western Atlantic coast. Thus, these groups should be considered as discrete management units, and the patterns of genetic exchange investigated. If eastern oysters inhabiting the Laguna Madre, Texas, are unique, they warrant protection.

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Effects of resuspension of eastern oyster Crassostrea virginica biodeposits on phytoplankton community structure

Marine Ecology Progress Series ◽

10.3354/meps13277 ◽

2020 ◽

Vol 640 ◽

pp. 79-105

Author(s):

ET Porter ◽

E Robins ◽

S Davis ◽

R Lacouture ◽

JC Cornwell

Keyword(s):

Water Quality ◽

Community Structure ◽

Crassostrea Virginica ◽

Skeletonema Costatum ◽

Eastern Oyster ◽

Energy Dissipation Rate ◽

Negative Effects ◽

Cell Densities ◽

Sediment Bottom ◽

Nitrite Nitrate

Anthropogenic disturbances in the Chesapeake Bay (USA) have depleted eastern oyster Crassostrea virginica abundance and altered the estuary’s environment and water quality. Efforts to rehabilitate oyster populations are underway; however, the effect of oyster biodeposits on water quality and plankton community structure are not clear. In July 2017, we used 6 shear turbulence resuspension mesocosms (STURMs) to determine differences in plankton composition with and without the daily addition of oyster biodeposits to a muddy sediment bottom. STURM systems had a volume-weighted root mean square turbulent velocity of 1.08 cm s-1, energy dissipation rate of ~0.08 cm2 s-3, and bottom shear stress of ~0.36-0.51 Pa during mixing-on periods during 4 wk of tidal resuspension. Phytoplankton increased their chlorophyll a content in their cells in response to low light in tanks with biodeposits. The diatom Skeletonema costatum bloomed and had significantly longer chains in tanks without biodeposits. These tanks also had significantly lower concentrations of total suspended solids, zooplankton carbon, and nitrite +nitrate, and higher phytoplankton carbon concentrations. Results suggest that the absence of biodeposit resuspension initiates nitrogen uptake for diatom reproduction, increasing the cell densities of S. costatum. The low abundance of the zooplankton population in non-biodeposit tanks suggests an inability of zooplankton to graze on S. costatum and negative effects of S. costatum on zooplankton. A high abundance of the copepod Acartia tonsa in biodeposit tanks may have reduced S. costatum chain length. Oyster biodeposit addition and resuspension efficiently transferred phytoplankton carbon to zooplankton carbon, thus supporting the food web in the estuary.

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