44-13 Investigating Microplastic Incorporation in Modern Agglutinated Foraminiferal Tests from Sabine Lake, Southeast Texas, USA

Abstract:

Microplastics have become ubiquitous in both terrestrial and aquatic environments. As an emerging contaminant, the effects of microplastics on aquatic ecosystems are still being investigated. Aquatic organisms may ingest microplastics starting at a low trophic level, passing particles through the food web. Some organisms, such as agglutinated forms of the single-celled foraminifera, have also been found to incorporate microplastics from their surroundings into their tests. The objective of this study is to identify potential microplastic incorporation within the test wall of agglutinated foraminifera, focusing on estuarine agglutinated foraminifera from Sabine Lake, Southeast Texas, USA. To investigate the incorporation of microplastics in agglutinated foraminifera, 10 samples were collected on a roughly north-south transect along the Texas-Louisiana border using an Eckman dredge. The transect crosses the natural salinity gradient of Sabine Lake, passing from the freshwater-influenced, low salinity waters of the northern portion of the lake into the higher salinity, marine-influenced southern waters. After collection, the samples were rinsed through a 63-micron mesh sieve to remove clays and were allowed to dry. Once dried, 300 specimens per sample were picked to assess variability in the assemblages. The southernmost samples are dominated by calcareous benthic foraminifera, whereas the middle and northernmost samples display a predominately agglutinated assemblage. The most abundant agglutinated taxa amongst the samples include species belonging to the genera Ammobaculites, Caronia, Haplophragmoides, and Miliammina. For microplastic analysis, agglutinated foraminiferal tests will soak in a mixture of Nile Red dye and acetone, which will preferentially bind to microplastics rather than mineral grains in the test wall. After drying, the samples will be observed using a stereomicroscope equipped with cyan lighting (490-515 nm wavelength) and an orange filter to fluoresce any microplastics in the test. The data collected in this study will contribute to the growing understanding of agglutinated foraminifera and their response to pervasive microplastics in the environment.

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