Abstract
Common bottlenose dolphins, Tursiops truncatus, can suffer health complications from prolonged freshwater exposure; however, little is known about how dolphins behaviorally respond to flood events. We investigated whether dolphins mitigated their freshwater exposure by moving south towards the estuary mouth and/or towards deeper areas with higher salinities in response to a record-breaking flood in Pensacola Bay, Florida. In total, 144 dolphin groups observed during 45 population dynamic surveys were analyzed across two flood-impacted sampling sessions and their respective seasonal control sessions. Kernel density estimates demonstrated southern movement towards the estuary mouth during flood-impacted sessions, but this distribution change was limited. Species distribution models showed that dolphins did not move to deeper areas after the flood and dolphin distribution was not substantially altered by flood-induced salinity changes. The estuary system exhibits strongly stratified waters with broad salinity ranges even during the flood. Dolphins may have mitigated the severity of freshwater exposure by capitalizing on these stratified areas as they continued to use habitat affected by the flood. A lack of avoidance of low salinity could result in this dolphin population being at greater risk for health problems, which should be considered in future population management and conservation.
Highlights
Common bottlenose dolphins, Tursiops truncatus, that inhabit brackish inshore estuaries have been observed in salinities ranging from 15 to
A high-precipitation event that coincided with local agricultural pesticide applications and reduced bay salinities to
Abrupt changes in water quality and salinity caused by floods were associated with the development of poxvirus-like skin lesions on Indo-Pacific bottlenose dolphins, Tursiops aduncus [9]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Poor water quality, prolonged freshwater exposure, and changes in water temperature were associated with increases in dolphin skin lesion prevalence and extent in multiple populations [1,2,4,7,8]. Complications in dolphins, there is still much to learn about how dolphins behaviorally respond to potentially harmful water quality conditions and low salinities in their habitat. Natural climatic events, such as floods, can drastically alter water quality by affecting salinity, water temperature, dissolved oxygen (hereafter abbreviated as ‘DO’), pH, turbidity, nutrient levels, organic matter loadings, and primary productivity in estuaries over a short time period [10,11,12], which can have impacts on dolphins. If dolphins avoided freshwater areas, it was expected that salinity and depth would be associated with dolphin distribution during flood conditions
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