Dolphin Health
Common bottlenose dolphins (Tursiops truncatus) can occupy habitat across a broad salinity gradient (8-35 parts-per-thousand), but are particularly susceptible to low salinity (< 10 ppt) conditions. Tropical storms and hurricanes frequently hit coastal ecosystems and increase the amount of freshwater in the ocean, decreasing the salinity of the seawater. Dolphins inhabiting areas that are impacted by these severe weather storms will develop skin disorders and experience an increase in stress hormones. A lot of research currently exists on the health and stress impacts of freshwater exposure in dolphins; however, no studies have been done that examine dolphin health under high salinity conditions (35+ ppt). TCBDP researchers are looking to fill this gap in knowledge by assessing resident dolphins that inhabit the Laguna Madre, Texas, the only naturally occurring hypersaline (or high salinity) lagoon in the USA and one of six in the world.
Photo Credits: Makayla Guinn, NMFS permit no. 21938
How do we study dolphins under high salinity conditions?
In the field, TCBDP researchers are assessing dolphin health in two ways: 1) taking photographs of dolphins during boat surveys to identify skin disorders and 2) collecting blubber tissue samples to measure hormone concentrations. Blubber is collected using a minimally invasive technique called remote biopsy sampling, in which a modified crossbow device is used to obtain a small (7-10 mm) tissue sample of free-swimming dolphins while researchers remain on the boat. Remote biopsy sampling does not involve intense animal handling and is done by trained professionals with the required federal research permits. Dolphin behavior is actively monitored before and after each biopsy attempt to ensure no adverse response to sampling.
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Back in the lab, TCBDP researchers analyze the blubber tissue using a highly sensitive instrument that is able to detect and quantify small concentrations of different compounds in the tissue. Researchers use this data to interpret the relative stress levels of the dolphins. Additionally, all photographs of dolphins are compared to a catalog of known skin disorders to evaluate dolphin health.
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Why is this important?
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Bottlenose dolphins indicate ecosystem health and are important to study in order to maintain conservation efforts and preserve local biodiversity. The effects of natural exposure to high salinity conditions in dolphins are currently unknown and remain a management priority of the National Oceanic and Atmospheric Administration. By working to fill this data gap, TCBDP researchers play an important role in helping to preserve marine life and promote environmental stewardship to benefit future generations globally.
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