Discipline: Ecology Environmental and Earth Sciences
Hannah Merges - Ursinus College
Blue crabs (Callinectes sapidus) comprise the largest fishery in the Maryland Coastal Bays (MCBs) region. Blue crabs and the seawater in the MCBs have been shown to contain high levels of Vibrio vulnificus, a bacterium that thrives in warmer waters with low salinity levels. V. vulnificus can pose serious health threats to humans if contaminated raw or undercooked blue crabs are consumed and/or when humans swim or wade in waters where this bacterium is prevalent. It is thus vital that we understand the factors that affect the prevalence of V. vulnificus in the blue crabs and seawater. The objective of this study was to fill in the current data gap with new information on the prevalence of V. vulnificus in blue crabs and seawater. Seawater (3 liters) and blue crabs (5-6) were collected from six sites across the MCBs in June 2018. The Most Probable Number (MPN) method and real-time polymerase chain reaction (PCR) test were used to analyze the seawater and blue crab (both the hemolymph and the crabmeat) samples for the prevalence of V. vulnificus. V. vulnificus has two types, a species-specific gene, vvhA, and a pathogenic gene, vcgC. All samples were positive for vvhA and 81% of samples were positive for vcgC. There was no statistical difference between the results from each sample type, although the trend of the results showed an increasing prevalence of V. vulnificus from seawater to hemolymph to crabmeat. The regression analysis showed that there was a significant correlation between pH, dissolved oxygen, salinity and the prevalence of V. vulnificus, but no significant correlation with temperature. Overall, results showed that these samples contain V. vulnificus, which can be a threat to human health. Future studies on additional sites both within and outside of the MCBs may help to indicate the extent of this threat and to further elucidate how the various factors, such as salinity and temperature, affect the prevalence of V. vulnificus. This may be particularly important in the face of climatic variability, which can influence salinity levels and surface water temperatures in the MCBs.
Funder Acknowledgement(s): I would like to acknowledge the NSF and the NSF CREST Project #1547821 for providing the opportunity to complete marine science research as an REU student at the University of Maryland Eastern Shore.
Faculty Advisor: Dr. Salina Parveen and Dr. Leah Joseph, email@example.com
Role: I worked alongside a graduate student and two undergraduate lab assistants and assisted with this whole process. From sample collection through statistical analysis, I researched all samples collected in June. The main focus of my research was running PCR for all of our samples as well as the analysis of the results, but I helped with the processing of samples and the MPN method too.