Matthew Thompson, Gallaudet University

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Abstract:

Marine snow plays an important role in the nutrient cycling and transport of particle associated bacteria to the dark deep of the ocean. Previous studies seemed to suggest that microbial abundance was lower in the bathypelagic zone compared to the epipelagic zone. However, the relationship between microbial abundance and particle sizes across the water column is unknown. Samples were obtained from the AT42-09 cruise aboard the R/V Atlantis to the East Pacific Rise in Spring 2019 then conserved in the freezer at -80°C prior to processing. These samples were prepared on black polycarbonate filter discs with DAPI stain then placed on microscope slides with a cover-slip coated in immersion oil. They were viewed under the Zeiss Axiophot Epifluorescence Microscope. Data analysis of obtained data from observations through a microscopy was carried out on Excel. The results were surprising as these data showed that the microbial abundance decreased until ~300 m where it started to increase. Other studies contrasted with a decrease in the microbial abundance across the water column (Bergauer et al. 2018). Across particle sizes, microbial abundance was expected to be at the highest on smaller particle sizes (Kostadinov et al. 2009). However, the data indicated otherwise with an inconsistency in the microbial abundance across particle sizes. To account for possible contributing factors to inconsistencies in data, negative controls were used to assess the possibility of bacteria contamination and most microbial abundance from samples had higher abundance versus the negative controls’ abundance which suggests the numbers were most likely real. These data did not arrive at a firm conclusion which may suggest some challenges from the methodology to be addressed.