Is Food Supply Adequate for Oyster Larvae in Mississippi Sound? Evaluation of Food Quality and Quantity Through Optical, Biochemical, and Biological Observations and Modeling

Principal Investigators: Dr. Xiaodong Zhang (USM), Dr. Eric Powell (USM), Dr. Kristina Mojica (USM)

Team Members: Dr. Danielle A. Kreeger (collaborator), Dr. Lucas Barbedo (PostDoc), Dr. Yuanheng Xiong (PostDoc), Thomas Wissing (PhD student), James Klein (MS student), Emma Coltmann (MS student), Avijit Talukder (PhD student)

Award Amount: $615,000

Project Description

Goal:

Integrate optical, biochemical and biological observation with a cutting-edge oyster larval model to identify, understand, and predict the nutritional constraints on oyster larvae performance as measured by survival, growth, and success at metamorphosis in the Mississippi Sound.

Why it is Important:

Through the previous investigation, we found (i) Food source was relatively low in protein proportion, which in addition to frequent low salinity (< 10 PSU), might have contributed to a low rate of larval settlement noted in 2021 throughout the region; (ii) The few locations where some successful metamorphosis was predicted by the larval model coincided with locations where recruitment was observed; and (iii) Phytoplankton in the area are predominately macro sized (>20 µm), but during a few cases where successful larval metamorphosis was predicted and confirmed, there was always a concurrence of picoplankton (of sizes from 0.2 to 2 µm) as well as an overall increase of organic particles of sizes < 2 µm. These findings suggest that poor oyster resiliency and productivity in Mississippi Sound is in part due to unfavorable food conditions which require further investigation. We hypothesize that successful larval recruitment requires a relatively protein-rich diet that might be provided by small-sized particles, including picoplankton, bacteria, and/or viruses, the availability of which presently presents a serious constraint on oyster resiliency and productivity.

Objectives:

• To understand how food quality (Lipid/Protein/Carbohydrate) of oyster larvae is related to the type and size of plankton and particles in the Mississippi Sound

• To develop a predictive understanding of how the quality, type, and size of food sources affects larval settlement success

• To provide a tool for improved siting of revitalization and restoration efforts leading to efficient use of available funding resources

Expected Outcomes and Management Impacts:

• Measurements of environmental and optical properties will be made at seven oyster habitats in the Mississippi Sound. The environmental variables to be measured include temperature, salinity, and dissolved oxygen concentration. The optical properties are the spectral absorption coefficient and the volume scattering function.

• Particulate organic and inorganic matter and size composition of phytoplankton species will be derived from optical data. These parameters will provide a general quantification of water quality and food quality for oyster and oyster larvae.

• The abundance and size distribution of the microbes (phytoplankton, bacteria, viruses, and heterotrophic nanoflagellates) will be derived from flow cytometry analysis of water samples.

• The biochemical composition (lipid, protein, and carbohydrate) of micro- (20-200 µm), nano- (2-20 µm), pico- (0.2-2µm), and virus sized (0.02-0.2 µm) particulate organic matter will be obtained.

• The larval performance model will be expanded to include size dependency of food particle quantity and quality: this will be a unique capability.

• Predictions of larval performance will be obtained from the size-dependent food quantity and quality metrics and compared to observed recruitment performance in the field relative to observed settlement patterns, population health metrics, and substrate quality.

• Development of an empirical relationship between optically-derived water quality and food quality and an oyster larvae-specific food index will be obtained. The relationship will allow the optical data to be used directly in the oyster larval model that responds to food quantity and quality, offering potential for real-time application.

• A modeling capability predicting oyster larval performance and success at metamorphosis using an optically-derived food index in Mississippi Sound will be developed. Once proven, this will provide real-time monitoring capability for oyster larval performance, that will be critical for enhancing oyster production and reef sustainability.

OUTREACH:

• We will be involving Crystal Sea in all oyster sampling – this is a major MS oyster business.

• We will be giving talks/posters at the National Shellfisheries Annual Meeting and the American Fisheries Annual Meeting.

• We plan to present at Science on Tap, a community outreach program hosted at a local brewery intended for unformal science talks to the public (https://www.usm.edu/news/2023/release/science-on-tap.php)

• We will participate in GCRL Science Café – directed to the public and GCRL summer field program students.

• We will present at local high schools in collaboration with K-12 science teacher partners.

Project Outputs