To implement this promising idea, this project has three main phases:
We strongly believe that the Golden Triangle Community may benefit from this research idea. We intend to consider installing the weather stations in other locations in the area.
Rangia cuneata is a brackish water clam found in estuarine ecosystems and is an important part of the aquatic community. Locally, it is found in Sabine Lake and in the Neches River north of I-10. It is extremely abundant where it occurs, often accounting for 95% or more of the community biomass. In 2016, we conducted a survey of rangia beds above and below the salt water barrier to determine the effect of the barrier on historical rangia populations. The barrier cut off salt water intrusions, which flow up the river from the Sabine Lake estuary and are needed for the clam's reproductive cycle, causing rangia clam beds to go extinct upstream of the barrier. The clam beds downstream of the barrier, however, were completely dominated by rangia with clam densities up to 86 clams per square meter. Since our 2016 study, the Neches River has flooded 9 times, including the unprecedented flooding from Hurricane Harvey. Additionally, record-breaking freezing temperatures occurred in February 2021. While the effect of low flows and high salinity on rangia clams are well understood, the effect of flooding and freezing events on this important species is not well known. The goal of this project is to revisit the clam beds downstream of the salt water barrier and assess the effect of flooding and freezing on rangia.
The methods will be those used by Harrel (1993) and Christensen and Pyne (2020) to estimate density and determine clam age. Ten square meter quadrats will be randomly placed in each clam bed and all clams within the quadrats removed by hand and measured with Vernier calipers to the nearest mm. Water physicochemical parameters (DO, pH, temp, salinity) will be measured with a LabQuest 2 handheld monitor equipped with appropriate sensors (Vernier Inc.). Other conditions including substrate, turbidity, depth and barriers will be noted. We will also compare the genetic structure of Neches River clams to the clams in Sabine Lake to determine if the river clams are genetically isolated from the estuary clams. At each site a random subsample of clams will be used for genetic analyses. We will use the non-invasive sampling techniques to obtain a swab of the mantle cavity to use in DNA extraction. The DNA will be extracted using a commercially available DNA extraction kit and stored at -20 C until use in polymerase chain reaction (PCR). We will amplify a region of cytochrome oxidase I (COI) gene using the primers and the resulting fragments will be sent to MCLabs for sequencing. The DNA sequences will be edited and analyzed to examine genetic population structure of the individual site and the level of gene flow between the sites using GeneStudio, a molecular biology software package.