Mary Kate Munley is a marine, estuarine and freshwater biology major who was one of the authors of a recently published study about the impact of “red tides” on Florida’s Gulf Coast on stone crabs.
This is not the first time Mary Kate’s achievements have been talked about in COLSA's Spotlights: the driven senior, who was selected to participated in the summer 2020 Fulbright-MITACS Globalink program (which was unfortunately cancelled due to the pandemic), has made it a point during her time at UNH to seize opportunities that have come her way, including working in the labs of Prof. Larry Harris and Prof. Elizabeth Fairchild. She’s also interned at the Sea Turtle Conservation and Research Program at Mote Marine Laboratory in Sarasota, Florida.
Mary Kate Munley: Almost annually Florida's Gulf coast experiences "Red Tides" which are caused by a high concentration of a phytoplankton, Karenia brevis. The toxins produced during these blooms in high concentrations can cause mass mortality events, also known as fish kills. These toxins occur in nearshore and coastal habitats where the Florida stone crab lives.
Mary Kate Munley, fifth from left, poses with research team at the Mote Research Laboratory.
In addition to the exposure to toxins, crabs in these areas are exposed to low oxygen concentrations in the water. The decaying fish from the mass mortality events further intensify the low oxygen caused by warming water temperatures. Our research determined the effect of prolonged exposure the toxins and low oxygen levels combined on stone crabs through laboratory experiments.
Mary Kate: The stone crab fishery is valued at ~$25-30 million a year in the state of Florida. The stone crab fishery is a declaw and return fishery, meaning that the claws of adult stone crabs are removed and the crab is released back into the wild to regrow its claws. This is done with the hope that the crab will regrow its claws to re-enter the fishery in future years so its claws can be harvested again. However, this method can have negative impacts such as mortality and reduced reproductive success in crabs.
Florida red tide blooms primarily occur in nearshore and coastal areas, which also are the habitats of juvenile and sublegal stone crabs, which represent the future stock of the fishery. In addition, since
2011 the southwest coast of Florida has seen approximately a 60% decrease in the region’s annual harvest. This indicates that prolonged red tide blooms may be impacting the stone crab population.
Mary Kate: Our results suggested that stone crabs in shallow nearshore environments will likely not be able to emigrate away from severe blooms or severe hypoxia (low dissolved oxygen). Crabs exhibited lethargy and immobility upon exposure to severe hypoxia. Combined exposure to severe hypoxia and Karenia brevis resulted in an 85.7% decrease in cumulative survival in comparison to the control.
This indicated that the tolerance of sublegal stone crabs to these conditions is dependent on the severity and duration. On a more positive note, there was a significant difference in mortality and stress between moderate hypoxia and severe hypoxia indicating that future mitigation efforts to reduce the severity of the blooms will benefit these populations.
Mary Kate: This research provides further insight into the detrimental effects of Karenia brevis blooms on sublegal stone crabs which is the future stock for the lucrative stone crab fishery.
Mary Kate: My research advisor was Dr. Philip Gravinese who is currently at Florida Southern College
Mary Kate’s research was supported by her research advisor, Philip Gravinese, who is currently an assistant professor of marine biology at Florida Southern College, the National Science Foundation (NSF OCE #1757419), the Steinwachs Family Foundation, which supported Gravinese's postdoctoral fellowship at Mote Marine Laboratory, and the Mote Scientific Foundation.
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