Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

A detailed description of methods was written by Marshall et al. (2021). In summary, mortality of oyster spat spawned from four different broodstocks was measured when exposed to five different salinities (without acclimation) under controlled laboratory conditions. Oyster broodstocks were sourced from two populations in Louisiana (Calcasieu Lake; 29°50′58′′N, 93°17′1′′W, and Vermilion Bay; 29°34′47′′N, 92°2′4′′W) and two populations in Texas (Packery Channel; 27°37′38′′N, 97°13′59′′W, and Aransas Bay; 28°7′38′′N, 96°59′8′′W). This salinity tolerance experiment was conducted in November–December 2018 (Trial 1) and March–April 2019 (Trial 2) at Texas A&M University-Corpus Christi.

In each trial, 25 oysters from each stock were placed in labelled petri dishes within 15 38-L tanks (100 oysters per tank) with aerated artificial seawater (using Instant Ocean Reef Crystals Reef Salt, Blacksburg, Virginia) at 25 °C and salinities of 2.0, 4.0, 20.0, 38.0 and 44.0; each salinity treatment was replicated three times (5 salinity treatments × 3 replicate groups = 15 tanks). The temperature of each tank was maintained using Hydor 100W submersible glass aquarium heaters. Oxygen was supplied to each aquarium via air pump/stone, and tanks were heated to approx. 25 oC. Temperature and salinity from each tank were recorded daily. Nutrient (NO2, NO2, NH3/NH4) concentrations in each tank were measured approximately weekly. Oysters were fed daily with Shellfish Diet 1800® at approximately 3mL/100 oysters unless the water was cloudy (i.e., food from the previous day hadn’t been consumed). Trial 2 is a repeat of the same experiment conducted in Nov/Dec 2018 using the same oyster stock. The only difference is that three aquaria of salinity 20 were added with no airstone to compare oyster mortality in low and high oxygen concentrations.

Every other day, the numbers of live and dead oysters of each stock in each tank were counted over a 3-week period and the dead oysters were removed. Oysters were determined to be dead if their valves (shells) remained open despite any handling.

Water temperature was measured using an aquarium thermometer or YSI ProDSS multiprobe. Salinity was measured using a Fisher Scientific portable refractometer or YSI ProDSS multiprobe. Dissolved oxygen concentrations and saturation, and pH were measured using a YSI ProDSS multiprobe. Nutrients were measured using API test strips or API Liquid Test Kit. YSI ProDSS sensors were calibrated at least weekly.

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NSF Award Abstract:

The project focuses on understanding how oysters from different regions in the Gulf of Mexico (GOM) will be affected by ongoing changes to salinity and temperature caused by a warming climate, altered rainfall patterns, and changes in land use in this region. The oyster fishery in the GOM provides more than half of the national total, and these oyster reefs provide water filtration, shoreline stability, and critical habitat for other species. By investigating how present-day oyster populations respond to changes in temperature and salinity, this research will provide valuable information to ecologists, conservation biologists, state managers, and small-scale farmers as they plan for the effects of future changes in the environment. By identifying populations of oysters that are the most resilient to environmental changes, this research will identify potential source populations that may be used in future restoration efforts aimed at declining populations. Additionally this project will integrate research and education through a semester-long immersive research experience. Three undergraduates, two graduate students, and a postdoctoral scholar will be mentored. Public outreach will be conducted through development of middle school lesson plans, public lectures, and dissemination of results to managers.

This research will test whether eastern oysters (Crassotrea virginica) in the Gulf of Mexico are locally adapted to salinity, and whether combined changes in salinity and temperature will have synergistic effects on oyster physiology and ecology. Both temperature and salinity are expected to change rapidly in the Gulf of Mexico over the coming century, due to effects of climate change, altered rainfall patterns, and changes to coastal hydrology. Oysters are a critical habitat-forming species in this region, and while they inhabit a wide range of salinities, preliminary data indicate substantial differences in salinity tolerances among populations. This research will integrate genomic and physiological tools with controlled rearing experiments to (1) quantify genomic variation among populations of C. virginica, (2) test for local adaptation, and (3) measure physiological rates and gene expression as a function of temperature and salinity. The investigators will then use these data to build estuary-specific dynamic energy budget models, linking salinity and temperature to population growth. This project will provide critical support to ongoing restoration efforts, identifying adaptive variation among populations targeted for supportive breeding programs and informing management decisions in the face of ongoing ocean warming and changes to coastal hydrology.