Paper No. 7
Presentation Time: 9:45 AM
IMPORTANCE OF ESTABLISHING BASELINE DATA FOR ENVIRONMENTAL INTERPRETATION: FORAMINIFERA OF THE MISSION ARANSAS NATIONAL ESTUARINE RESEARCH RESERVE, TEXAS
In 2006 the Mission Aransas National Estuarine Research Reserve (MANERR) was established along the south Texas coastline. The Mission and Aransas Rivers respectively enter Mission and Copano Bays, and the reserve encompasses other bays as well as the Aransas National Wildlife Refuge. Inflow into Texas estuaries is important in terms of quality of the environment and thus the economy, with various agencies monitoring freshwater input. Since the establishment of the MANERR, living foraminifera have been sampled in many of the secondary and tertiary bays including Copano, Mission, Mesquite, and St. Charles. Abundant and easily sampled, foraminiferal populations provide information about current biotic conditions and then their dead tests accumulate to catalog past environments. The present study focuses on Mission Bay, a small tertiary bay from which foraminifera have never been studied. Cores were taken at four stations along a north-south transect from the mouth of the Mission River to the mouth of the bay, and a total of 14 species were found. Statistical analysis shows that richness and diversity increase and species dominance decreases toward the bay mouth. These population parameters indicate a healthy ecosystem, though a couple of observations are worth noting. First, some dead tests exhibit a distinct yellow discoloration thought to be due to sulfur since yellow minerals are also seen in the sediments. Past research recorded excess barium in the bay, perhaps from barium sulfate muds associated with oil drilling in the area. Shell analysis with laser induced breakdown spectrometry suggests the presence of barium in both living and dead specimens. Second, individuals from two species have dark spots in the stained protoplasm, perhaps from bacterial decay or mineralization. As with many coastal settings, abundant pyrite occurs in sediments as well as in living and dead foraminiferal tests, so the dark spots could be pyrite minerals. This study provides baseline foraminiferal data for future monitoring in the MANERR, and underlines the utility of foraminifera for environmental interpretation in the present as well as the past.