Student Research
Sara Smelley
The
Effects of
Longshore Drift Induced Beach and Foredune Progradation on the Ecology
of Invertebrate Burrowing and Trace-making Fauna, Packery Channel,
North Padre Island, Texas
Texas
A&M
University - Corpus Christi
Marinez
Scholar
Program
(Supervisor:
Dr. Garrison)
Infaunal
and epifaunal burrowing
organisms commonly experience environmental stress as a consequence of
rapid increases in sedimentation rate. If the increase in sedimentation
rate is gradual, organisms can respond by adjusting their burrow
geometry to accommodate the new location of the sediment-water
interface. If sedimentation rate is very rapid, environmental stress
may result in organisms experiencing major colonial disruption or even
total defaunation. In the ancient rock record, it is documented that
the burrows of infaunal crustaceans (Ophiomorpha
and Thalassinoides) are
present in both fair-weather and
storm deposits, although there is little information about the rate of
re-colonization following a major storm events or a rapid increase in
sedimentation rate, such as that produced by a wave-dominated delta
system during the rapid deposition of a stream mouth bar onto
underlying shoreface sands.
Recent nourishment and rejuvenation of a 3800 ft (1.2 km) section of
beach, facilitated by redeposition of 110,000 yd
3 (84,100 m3) of sand dredged
during re-opening of
littorally-closed Packery Channel, provides an excellent opportunity to
examine response of infaunal burrowing crustaceans to a sudden increase
in vertical sediment rate to 0.6-5.0 ft/year (0.2-1.5 meters/year)
and/or rapid beach progradation. Sand re-deposition and subsequent
storm-induced littoral drift resulted in over 330 ft (100 m) of beach
progradation between December 2003 and August 2005.
Recent
investigations of population densities of ghost shrimp Callichirus islagrande on the beach
south of Packery Channel
South Jetty provides quantitative data on the re-colonization rate of
these infaunal burrowing crustaceans. Since August 2005, Callichirus islagrande have almost
returned to normal North Padre
Island colonial densities, at an average lateral, landward
recolonization rate of 33.8 ft/month (10.3 m/month).
Publications
Garrison, James R.,
Jr. and Sara Smelley (2007)
Recovery of infaunal
crustacean colonies following a period of rapid sedimentation and
defaunation: a neoichnological examination following beach rejuvenation
on the south side of Packery Channel, North Padre Island, Texas: Gulf
Coast Association of Geological Societies Transactions, 57, 305-317.
(download pdf)