[MARMAM] New publication - skin lesion and mortality rates for bottlenose dolphins following a historic flood

Christina Toms ctoms at mote.org
Fri Oct 15 08:19:53 PDT 2021

Dear Marmam Subscribers,
On behalf of myself and my coauthors, we are pleased to announce a recent
publication in PLOS ONE.

Toms, C. N., T. Stone, and T. Och.  2021. Skin lesion and mortality rate
estimates for common bottlenose dolphins (Tursiops truncatus) in the
Florida Panhandle following a historic flood. PLOS ONE 16(10): e0257526.

*Abstract*: Increasing evidence links prolonged freshwater exposure to
adverse health conditions, immune deficiencies, and mortality in
delphinids. Pensacola, Florida, experienced a record-breaking flood event
in April 2014, after which, skin lesions evident of freshwater exposure
were observed on common bottlenose dolphins (*Tursiops truncatus*). Here we
assess the potential consequences of the flood on bottlenose dolphin health
and mortality. Data from an ongoing study were used to evaluate the
relationship between skin lesions (progression, prevalence, and extent) and
the flood with respect to changing environmental conditions (salinity).
Annual stranding records (2012–2016) from Alabama to the eastern Florida
Panhandle were used as an indicator of dolphin health to test the
hypothesis that the flood event resulted in increased annual mortality
rates. Although salinities remained low for several months, results suggest
that there was not the widespread skin lesion outbreak anticipated. Of the
333 unique individuals detected only 20% were seen with skin lesions. There
was a significant increase in the proportion of dolphins seen post-flood
with lesion extent above background levels (≥ 5%; *p* = 0.001), however,
there were only 11 cases with lesion extent greater than 20%. Skin lesion
prevalence increased overall following the flood (*p* < 0.001), but
pairwise comparisons revealed a delayed response with significant increases
not detected until the following fall (*p* = 0.01), several months after
salinities returned to expected levels. Regression modeling revealed no
significant effects of year, region, or year x region on mortality rates,
except in Alabama, where increased mortality rates were likely due to
residual impacts from the Deepwater Horizon Oil Spill. This study takes
advantage of a natural experiment, highlighting how little is understood
about the conditions in which prolonged freshwater exposure leads to
negative impacts on dolphin health.

The article and supplementary materials are available as open access here:
Or you can request a copy from me at: ctoms at mote.org.

Christina Toms
PhD, Postdoctoral Scientist
Chicago Zoological Society's Sarasota Dolphin Research Program
Cell: 808-990-1931
ctoms at mote.org
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