Thesis Defense Seminar - Lauren M. Rener

ENVIRONMENTAL SCIENCE PROGRAM
DEPARTMENT OF PHYSICAL AND ENVIRONMENTAL SCIENCES
TEXAS A&M UNIVERSITY-CORPUS CHRISTI

SUBJECT: Effect of Freshwater Inflow on Mollusk Community and Population Dynamics in Estuaries

MAJOR ADVISOR: Dr. Paul Montagna

ABSTRACT

Freshwater inflow changes can alter estuarine dynamics such as salinity, nutrients, and some biological communities. The freshwater that flows from inland sources are critical for the survival and production of estuarine organisms on the coast. Identifying the relationship among variables such as river inflow rate, estuarine salinity, various biological responses, and seasonal patterns is needed to determine requirements for developing inflow standards for estuaries. Mollusk populations respond to freshwater inflow. Inflow events cause salinity change, and abrupt salinity changes can trigger spawning and reproduction events.  In contrast, low inflow can result in unviable conditions for reproduction. Many mollusks species’ survival and growth rely on freshwater inflow for nutrients that promote primary production to feed larvae and young spat. Due to freshwater being essential for mollusk survival, they are suitable organisms for bioindicators of the effects of freshwater inflow within estuaries. The purpose of the current study is to compare mollusk population characteristics --such as the timing of reproductive events, growth rates, and population changes--over time in five estuaries along the Texas coast with different inflow rates, and responses to wet and dry periods.  Existing data from 1987 - 2019 were used. Estuaries compared include Lavaca-Colorado, Guadalupe, Mission-Aransas, Nueces, and Baffin Bay-Upper Laguna Madre.  The population characteristics were related to salinity change as an indicator for inflow change. The results were used to help evaluate freshwater inflow standards in these estuaries.