Louisiana Project: Improving region specific eastern oyster models by quantifying physiological responses regional environmental and climatic variability (using a DEB approach)

Louisiana Project

Improving region specific eastern oyster models by quantifying physiological responses regional environmental and climatic variability (using a DEB approach)

February 2014 - January 2016

Personnel

Megan La Peyre, Non-PI Collaborator

Participating Agencies

Louisiana Sea Grant

This study proposes to develop a DEB model for the eastern oyster, specifically applicable to the eastern oyster in the northern Gulf of Mexico. This project will involve several steps (1) develop a generic DEB model for the eastern oyster using available information for the eastern oyster (regardless of region or source population), (2) quantify key physiological rates (i.e., respiration, ingestion) for nGoM eastern oysters exposed to the range of temperature, salinity and food conditions reflecting conditions in the nGoM in order to provide model parameters, (3) fully parameterize the generic DEB model using our experimental data, and (4) use existing datasets (JLaPeyre & MLaPeyre, Louisiana Department of Wildlife and Fisheries) to calibrate and test the DEB model. The measurement of precise respiration and filtration rates (to derive ingestion) under a wide range of salinity, temperature and food conditions and the development of a DEB model for predicting oyster growth would ensure more accurate predictions of oyster growth, harvest, under specific environmental conditions. Furthermore, this work would enable predictions of carrying capacity for proposed regional aquaculture parks, identification of areas for restoration and protected areas, and predictions of oyster growth and production under predicted water diversion, sea level rise, and climate change scenarios. Ultimately, the generic DEB model could also be parameterized for other regions and applied widely.

Research Publications

Research Publications	Publication Date
Lavaud R., La Peyre MK, Casas S, Bacher C, La Peyre JF. 2017. Integrating the effects of salinity on the physiology of the eastern oyster, Crassostrea virginica, in the northern Gulf of Mexico through a Dynamic Energy Budget model. Ecological Modelling 363:221-233. \| Abstract	September 2017	We present a Dynamic Energy Budget (DEB) model for the eastern oyster, Crassostrea virginica, which enables the inclusion of salinity as a third environmental variable, on top of the standard food and temperature variables. Salinity changes have various effects on the physiology of oysters, potentially altering filtration and respiration rates, and ultimately impacting growth, reproduction and mortality. We tested different hypotheses as to how to include these effects in a DEB model for C. virginica. Specifically, we tested two potential mechanisms to explain changes in oyster shell growth (cm), tissue dry weight (g) and gonad dry weight (g) when salinity moves away from the ideal range: 1) a negative effect on filtration rate and 2) an additional somatic maintenance cost. Comparative simulations of shell growth, dry tissue biomass and dry gonad weight in two monitored sites in coastal Louisiana experiencing salinity from 0 to 28 were statistically analyzed to determine the best hypothesis. Model parameters were estimated through the covariation method, using literature data and a set of specifically designed ecophysiological experiments. The model was validated through independent field studies in estuaries along the northern Gulf of Mexico. Our results suggest that salinity impacts C. virginica’s energy budget predominantly through effects on filtration rate. With an overwhelming number of environmental factors impacting organisms, and increasing exposure to novel and extreme conditions, the mechanistic nature of the DEB model with its ability to incorporate more than the standard food and temperature variables provides a powerful tool to verify hypotheses and predict individual organism performance across a range of conditions.
Casas SM, Lavaud R, La Peyre MK, Comeau LA, Filgueira R, La Peyre JF. 2018. Quantifying salinity and season relationships on eastern oyster clearance and oxygen consumption rates. Marine Biology 165:90-101. \| Abstract	April 2018	Limited empirical data exist on Crassostrea virginica physiological rates across the range of salinities and temperatures that populations are regularly exposed. This lack of data reduces the accuracy of growth and production models under changing environmental conditions. The objectives of this study were to quantify the clearance and oxygen consumption rates of C. virginica from Louisiana across a range of salinities (3, 6, 9, 15 and 25) and seasonal temperatures (17 ºC in winter, 27º C in summer) typical of the region. Salinity and temperature affected C. virginica physiology differently; salinity impacted clearance rates with reduced feeding rates at low salinities, while temperature had a strong effect on respiration rates. Highest clearance rates were found at salinities ranging between 9 and 25, with reductions ranging from 50-80% and 90-95% at salinities of 6 and 3, respectively. Oxygen consumption rates in summer increased fourfold compared to winter. Oxygen consumption rates were within a narrow range and similar between salinities in winter but showed significant variation between individuals and salinities in summer that likely reflected varying stages of gonad development. Valve movements measured at the five salinities indicated oysters remained opened between 50 and 60% of the time in the 6 to 25 salinity range and about 30% at a salinity of 3. Reduced opening periods, concomitant with narrower gap amplitudes, support the finding of limited feeding at the lowest salinity (3). These data indicate the need for increased focus on experimental determination of optimal ranges and thresholds to better quantify oyster population responses to environmental changes.
Casas S. M., Filgueira R, Lavaud R., Comeau L. A., La Peyre M. K., La Peyre J. F.. 2018. COMBINED EFFECTS OF TEMPERATURE AND SALINITY ON THE PHYSIOLOGY OF TWO GEOGRAPHICALLY-DISTANT EASTERN OYSTER POPULATIONS. Journal of Experimental Biology 506:82-90. \| Abstract	June 2018	Understanding why a species occupies a certain geographic range and predicting how they will be affected by climate change require characterizing physiological traits in geographically-distant populations. The objective of this study was to perform a direct comparison of two eastern oyster (Crassostrea virginica) populations that occupy contrasting temperature and salinity habitats, New Brunswick, Canada (47 °N – Gulf of St. Lawrence) and Louisiana, USA (29 °N – Gulf of Mexico). Specifically, clearance rate, valve opening and oxygen consumption rate were measured in oysters of both populations following a full factorial design with three temperatures (10, 20, 30°C) and two salinities (15, 25). New Brunswick oysters had a greater gill area, shell gap angle, and oxygen consumption rate. Temperature was the main driver of clearance rate, valve opening duration and oxygen consumption rate. Clearance rate at 20°C and 30°C was significantly higher than at 10°C, and oysters at 20°C had their valves opened for a greater percentage of time compared to oysters at 10°C and 30°C. Oxygen consumption rate increased gradually from 10°C to 30°C and similarly for both populations, with no indications of a thermal breakpoint at 30°C. Temperature coefficients for the oxygen consumption rate (Q10) were within the normal ecological range for both populations. No physiological differences were observed between salinities in both populations. No latitudinal compensation in the physiological rates was found. Overall, results showed that C. virginica is tolerant to a broad range of temperatures and salinities. Such physiological plasticity is consistent with the species’ extended geographical range.

Theses and Dissertations

Theses and Dissertations	Publication Date
Bernasconi, S. 2016. Eastern oyster physiological responses to acute and chronic exposure to suspended sediments. MS Thesis. Louisiana State University.	January 2017

Data or Software Releases

Type	Citation	Publication Date
Data Release	Lavaud, R., La Peyre, M.K., Couvillion, B., Brown, V., Pollack, J.B., Palmer, T., and Keim, B., 2023, Eastern oyster Dynamic Energy Budget model outputs under current (2014-2020) and projected (2041-2050) temperature and salinity conditions in Texas and Louisiana estuaries and along northern Gulf of Mexico coast: U.S. Geological Survey data release, https://doi.org/10.5066/P9YS78DY.	September 2023

Cooperative Fish and Wildlife Research Units Program: Louisiana Education, Research and Technical Assistance for Managing Our Natural Resources