Date of Award

Fall 8-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Rebecca J Van Beneden

Second Committee Member

Heather Hamlin

Third Committee Member

Scarlett Tudor

Abstract

Arsenic is a toxic metalloid that exceeds safe drinking water standards in groundwater in many locations worldwide. Arsenic exposure in fish has been linked to destruction of gill tissues, impairment of growth, decreased muscle mass, memory impairment, increased aggression, and avoidance behaviors. We examined the behavior of mummichogs (Fundulus heteroclitus) following arsenic exposure during development in two studies. Embryos were collected from fish from three reference sites: Scorton Creek (SC), Massachusetts, Wells Harbor (WE), Maine, and Block Island (BLOC), Rhode Island and two contaminated sites: Callahan Mine (CM), Brooksville, Maine, and New Bedford Harbor (NBH), Massachusetts. Embryos were exposed to 0, 10, 50, or 500 ppb (parts per billion) sodium arsenite. These levels represent a control, the current EPA (Environmental Protection Agency) and WHO (World Health Organization) Maximum Contaminant Level (MCL) of arsenic in drinking water, the previous regulatory standard, and the upper level of arsenic found in Maine ground water, respectively. We used five different standard tests to assess fish behavior: An Open Field Test to measure basic motor function; a Light/Dark Preference Test as a measurement of anxiety; a Novel Object Test to measure the response to a new variable in the environment; a Sociability Test to examine how an individual interacts with a group of conspecifics; and a Light/Dark Startle Response Test to look for differences in activity post exposure. We hypothesized that exposure to arsenic would alter fish behavior by decreasing activity, increasing the light preference, decreasing the time spent investigating the novel object, and decreasing the time spent socializing. Analysis of the Open Field Test showed an effect of location but not treatment. Fish from CM were less active than fish from the SC reference site. Results of the Light/Dark Preference Test showed that fish from CM exposed to arsenic spent less time in the light than fish from SC. The Novel Object Test showed no impact of treatment but a possible trend for location effect with fish from SC spending more time away from the novel object than fish from CM. The Sociability Test showed no differences in group behaviors. Finally, no differences in behavior were noted during the Light/Dark Startle Response Test. Overall, these results suggest that there are location-based differences in some of the behaviors explored here. The data also suggest that there is little impact of environmentally relevant levels of arsenic on mummichog behavior. This may be due to several reasons, including the ability of this fish to withstand low levels of arsenic exposure either by natural tolerance to environmental stressors or increased detoxification processes. Further research would be needed to distinguish which process, if any, is present in these populations to support that idea.

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