The Effects of Metal Contaminants on Fish Sensory Abilities

Copper (Cu) has been used over the last 50 years for its fertilizer properties in Florida. In 2005, over 250 thousand hectares in Florida were treated with more than 500,000 kg of Cu. In 2007, Cu contamination was ranked as one of the top-heavy metals accountable for the decrease in water quality in US water bodies by the US EPA. Due to the extensive use of Cu in Florida and its inability to degrade, Cu has accumulated and remains persistent in Florida’s aquatic ecosystems. Exposure to Cu has been found to impair neurotransmitter and chemosensory functions in fish. An excellent method to study Cu sub-lethal effects is fish swimming performance. Saltwater intrusion due to global warming is also of concern in South Florida. The goal of this study was to determine the effects of Cu on [1] swimming performance in Sailfin mollies and [2] predator-prey interactions between largemouth bass and Sailfin mollies across a salinity gradient . Ucrit was measured after a 10 minute period at a water velocity of 10cm/s, followed by speed increases of 2 cm/s every 5 minutes until reaching 22 cm/s, when speed increases occurred every 15 minutes until the fish stopped swimming. The protocol was replicated to obtain Repetitive Ucrit. Swimming performance (Ucrit & Repetitive Ucrit) was measured again after a 4-week-depuration period to determine if the fish were able to recover. In a separate study, Sailfin mollies (n = 60) were also exposed to 7.20 – 8.20 ug/L Cu; at 96 h, predator-prey interactions were assessed. In Phase 1, Sailfin mollies were presented to visual, chemical, or both visual and chemical cues and tested on predator avoidance. In Phase 2, predator-prey interactions were studied by introducing a live predator to determine prey mortality rate. Our results showed that swimming performance significantly decreased after a 96-h exposure and after a 4-week-depuration period, fish were able to return to their baseline Ucrit. Cu had an effect on visual, chemical, and visual + chemical cues on prey in both Phases 1 and 2. Adverse effects of Cu on fish swimming performance and predator-prey interactions can result in a decline in population survival.