Impact of disturbances on serpulid reef and soft-sediment macrofauna in Baffin Bay, Texas

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Coastal and Marine System ScienceIn subtropical regions, low inflow estuaries are influenced by long residence times that promote hypersalinity and are intermittently affected by acute rainfall events; extreme cold temperatures, while uncommon, can also occur. Baffin Bay, TX, USA experienced a sustained period (~7 days) of freezing temperatures during “Winter Storm Uri” in February 2021, and experienced an acute freshwater flooding event three months later with a 20 unit drop in salinity. This study used benthic macrofauna from soft-sediment and serpulid reef habitats as indicators for understanding the impact of successive freeze and flood disturbances on this low inflow estuarine ecosystem. Traditional community analyses were supplemented by stable isotope analysis of basal food resources and resource use by an abundant benthic predator and economically important fisheries species, black drum (Pogonias cromis). Successive disturbances in 2021 had minimal effects on soft-sediment benthic macrofauna abundance, biomass, richness, and diversity, with values falling within historically measured ranges. Serpulid reef benthic macrofauna were lower in biomass and richness following Winter Storm Uri, and higher in abundance and richness after freshwater flooding, with values outside of historic records. Despite this fluctuation during 2021 disturbances, serpulid reef macrofauna remained higher in abundance, biomass, and richness and more stable in community composition than soft-sediment macrofauna. Greater prey availability and reliability on serpulid reefs may be important for higher-level consumers. Stable isotope results indicate reliance of black drum on benthic macrofauna prey resources in both Baffin Bay and the adjacent Upper Laguna Madre in 2021. Understanding the response of benthic macrofauna indicators to environmental disturbance from acute freeze and flood events can inform future resource management strategies, particularly in light of increasing climate variability and water resource development.Coastal and Marine System Science ProgramCollege of Scienc