The Indian River Lagoon (IRL) is one of the most diverse estuaries in North America, supporting hundreds of species of wildlife, including bottlenose dolphins. In the 1970s, our scientists and colleagues began the first study of the biology of IRL dolphins. We’ve conducted photo-ID surveys of the dolphins in the lagoon via plane and boat for four decades now, documenting seasonal population changes, small scale movement, and population health. This important research focuses on predicting and preventing impacts from human disturbance, habitat loss and pollution, and climate change.

Most recently, our Research Scientist Wendy Noke Durden published abundance estimates and trends from nearly ten years of aerial surveys of IRL dolphins! The information we gather monitors the effects of ecological disturbances, unusual mortality events, and human impacts on this key species. We found that abundance estimates increased during extremely cold winter events and that the average abundance was 1,000 dolphins. As always, further investigation is needed to conserve this important dolphin population!

After significant unusual mortality events (UME) from 2011-2015, we’ve begun a full-scale investigation into what might be causing these die-offs of dolphins, seagrasses, and pelicans. All common pathological causes have been ruled out and a proposed factor – short term changes in prey availability – also unlikely based on a study first reported by postdoc Dr. Sam Rossman. In 2016, Dr. Rossman shared his findings at a meeting of marine mammal biologists and received the John R. Twiss Jr. Award for innovative research in ecosystem conservation.

Current research is employing a new laboratory technique to assess how a past legacy of pollution may be impacting the IRL and contributing to the die-offs. We’re studying rare forms of nitrogen locked away within layers of bottlenose dolphin teeth – our analysis is possible thanks to the collection of archived samples and data obtained by current and former HSWRI scientists.

One working hypothesis is that factors such as nitrogen pollution contributed by wastewater and fertilizer may have caused gradual changes in the estuarine environment that reached a tipping point in 2013. As restoration efforts (e.g., muck removal) ramp up in the IRL, studies such as ours are vitally important because they lend historical context as to how the ecosystem functioned prior to human disturbance and will provide a target to evaluate the effectiveness of current and future proposed remediation projects.

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