Benthic monitoring of the Mollie Beattie Coastal Habitat community in relation to opening Packery Channel
Montagna, Paul A.
Palmer, Terence A.
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Packery Channel was a natural channel that linked Corpus Christi Bay with the Gulf of Mexico, but has been closed since 1912. Construction to reopen the channel began in October 2003 and Packery Channel was reopened on 21 July 2005 by storm surge produced by Hurricane Emily. Official construction was completed in October 2006. A before versus after, control versus impact (BACI) design was implemented to assess the effects of reopening Packery Channel on water quality and estuarine macrofauna in Mollie Beattie Coastal Habitat Community (MBCHC), Corpus Christi Bay. Two deep (approximately 1 m below mean sea level) and two shallow (approximately 0.2 m below mean sea level) stations were sampled monthly for physical and biological characteristics at both control and impact sites between November and March from 2003 through 2009. There was little initial impact on the macrofaunal community composition, abundance, biomass, or N1 diversity caused by opening Packery Channel between July and December 2005. There was more difference in community composition between deep and shallow stations than between either before and after, or control and impact sites. Salinity was reduced at MBCHC and fluctuated in a diurnal pattern after the opening of Packery Channel, which is related to increased tidal exchange with the Gulf of Mexico. Packery Channel may have affected the salinity of MBCHC by introducing a diurnal fluctuation when water levels are high and by possibly decreasing the magnitude of long-term salinity fluctuations in MBCHC. The same salinity changes were not observed at reference site. Flow decreases along a gradient moving up Packery Channel away from the Gulf of Mexico, which indicates that tidal flows spill into MBCHC. Macrofauna diversity and biomass significantly decreased in the deep MBCHC site, but not in the reference site since Packery Channel opened. Macrofauna abundance increased in the deep MBCHC relative to the reference site in the second two-year period after the channel opened. Overall, the channel opening did not coincide with any changes in macrofauna abundance or diversity of the shallow MBCHC. Biomass did decrease in the shallow MBCHC after the opening of Packery Channel, but biomass is still greater than in the shallow reference site. The small change in hydrography in MBCHC has had little initial impact on macrobenthic communities, probably because MBCHC was already functioning as marine in terms of salinity.