Integration of Physical Oceanography with Spatio-Temporal Patterns of Stranded Sea Turtles in North Carolina
Abstract
The conservation status of sea turtles warrants research on their mortality rates
(Turtle Expert Working Group 1998). Stranded carcasses document mortality but
represent an unknown fraction of total number of dead turtles at-sea (Murphy and
Hopkins-Murphy 1989, Epperly et al. 1996). In addition to water temperature, tidal
forcing, decomposition rates, scavenging rates, and the spatio-temporal distributions
of
turtles and mortality sources, wind and water current regimes probably play a major
role
in the stranding of carcasses on beaches. Fifteen years of hourly wind speed data,
recorded off the North Carolina coast, were transformed into vectors, converted into
wind
stress magnitude and direction values, and averaged by month. Near-shore surface
currents were then modeled for the South Atlantic Bight via a three-dimensional physical
oceanographic model (Werner et al. 1999). Estimated currents and particle tracks were
compared to the spatial locations of sea turtle carcasses stranded along ocean-facing
beaches of North Carolina. The seasonal development of along-shelf flow coincided
with
increased numbers of recorded strandings in late spring and early summer. The model
also predicted net offshore flow of surface waters during winter, typically the season
with
the fewest relative strandings. Modeled lagrangian drogues were retained in shallow
(< 20m) bathymetric contours, indicating that turtles killed only very close to the
shore may be most likely to strand. During seasons when net along-shelf flow was present,
turtles
were likely to have died "upstream" from the residual current. A reevaluation of oceanic
drift bottle experiments may also provide a reasonable upper bound to describe how
far
carcasses could theoretically travel and how likely those carcasses could make landfall
from points offshore. Though qualitative, this research a.) provides a starting point
for
more robust analyses and b.) demonstrates that stranding research requires an
understanding of ocean physics in addition to sources of mortality.
Type
Master's projectPermalink
https://hdl.handle.net/10161/635Citation
Mooreside, Peter Douglas (2000). Integration of Physical Oceanography with Spatio-Temporal Patterns of Stranded Sea
Turtles in North Carolina. Master's project, Duke University. Retrieved from https://hdl.handle.net/10161/635.Collections
More Info
Show full item record
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Rights for Collection: Nicholas School of the Environment
Works are deposited here by their authors, and represent their research and opinions, not that of Duke University. Some materials and descriptions may include offensive content. More info