EXAMINING TWO METHODS OF IDENTIFYING POTENTIAL MICROPLASTIC INCLUSIONS IN AGGLUTINATED SPECIES OF FORAMINIFERA

Foraminifera are single-celled organisms found in marine environments that play a key role in the marine food web. Detrimental effects on these organisms can lead to cascading impacts on marine ecosystems. Agglutinated species of foraminifera incorporate particles from their surrounding environment into the walls of their outer shells, or tests, and studies have suggested that it is possible for microplastics to be incorporated into these structures. The aim of our study was to observe in-situ microplastic inclusions in foraminifera without compromising the structure of their tests. We explored two approaches. First, we combined scanning electron microscopy (SEM) and Raman microscopy. Using SEM we found carbon-rich areas in the matrix of the tests, which could indicate a microplastic inclusion. We then attempted to use Raman microscopy to further analyze the high-carbon areas to determine their composition and if they truly were plastic inclusions; however, the topography of the tests resulted in excessive scatter and sample burning after multiple rounds of imaging. For our second approach, we used 4-dimethylamino-40-nitrostilbene (DANS) fluorescent dye and widefield microscopy with the intent to stain and view the microplastic particles. Imaging is in the protocol development stage, and we have thus far demonstrated potential staining of PET microplastics but minimal staining of PTFE plastics. The foraminifera imaged did not show conclusive evidence of microplastic inclusions, which could be the result of several factors including lack of microplastics in the samples, the composition of potential plastic inclusions, the staining technique, and/or the sample mounting. Our next steps include continuing to optimize the staining procedure of plastic control samples. Afterwards, we will continue efforts to develop a protocol for imaging microplastics in foraminifera samples using confocal microscopy. While we did not conclusively observe microplastics in agglutinated foraminifera, we have demonstrated the potential of using SEM to identify carbon-rich areas and highlight the opportunity to refine our staining technique for future attempts.