ENVIRONMENTAL CORRELATES OF SEASONAL-TO-DECADAL SHIFTS IN PLANKTONIC FORAMINIFERAL ASSEMBLAGES IN THE GULF OF MEXICO

Marine ecosystems experience fluctuations in environmental conditions (e.g., temperature, salinity, nutrients, light availability, stratification, etc.) from hourly up to millennial timescales and beyond, with magnitudes often exceeding those caused by anthropogenic forcing. There are few ecological datasets temporally resolved enough to disentangle the effects of natural environmental variability from those due to modern anthropogenic change. Here we use an exceptionally long running and resolved USGS sediment trap from the Gulf of Mexico (GoM; 27.5ºN, 90.3 ºW) to investigate whether there are emergent signals of anthropogenic change in the assemblage composition of planktic foraminifera from January 2008–January 2020. This study focuses on the GoM, a semi enclosed basin in the northwest subtropical Atlantic Ocean affected by a variety of factors including loop current dynamics, Mississippi River discharge, and the frequency and intensity of storms and tropical cyclones. The Gulf’s relatively large seasonal temperature range (~10 ºC) and dynamic setting on a continental margin makes it an ideal location to explore the interacting effects of multiple environmental factors on the planktonic foraminiferal community.

We used Bray-Curtis dissimilarity to quantify differences in community composition between months and across 12 years, exploring the dominant modes of variability using a principal component analysis. The first two principal components account for nearly 60% of the variance, with PC2 capturing seasonal variation. Using satellite sea surface salinity and sea surface temperature data at the sediment trap site, along with other environmental parameters gathered from in situ, remote sensing, and modeled data, we explore the relationship between these environmental drivers to the trends seen in foram β diversity. These data allow us to explore the effect of anthropogenic factors on planktonic foraminiferal communities at this site.