TITLE:
Unsustainable Land-Based Source Pollution in a Climate of Change: A Roadblock to the Conservation and Recovery of Elkhorn Coral Acropora palmata (Lamarck 1816)
AUTHORS:
Geraldine Díaz-Ortega, Edwin A. Hernández-Delgado
KEYWORDS:
Acropora palmata, Coral Reef Decline, Eutrophication, Land-Based Source Pollution
JOURNAL NAME:
Natural Resources,
Vol.5 No.10,
July
31,
2014
ABSTRACT: Chronic
eutrophication and turbidity are critical detrimental factors impacting coral
reef ecosystems, adversely affecting their ecological functions, services,
benefits, and resilience across multiple spatial scales and over prolonged
periods of time. Inadequate land use practices and lack of appropriate sewage
treatment can adversely contribute to increase land-based source pollution
(LBSP) impacts in coastal waters and to magnify impacts by sea surface warming
trends associated to climate change. Fringing coral reefs off Vega Baja, Puerto
Rico, support extensive remnant patches of Elkhorn coral Acropora palmata (Lamarck 1816), which was listed in 2006 as a threatened
species under the US Endangered Species Act. Chronic impacts by LBSP have
significantly affected local downstream fringing reefs. We characterized the
spatial extent of a water quality stress gradient across 12 reefs along the
Vega Baja coast through monthly measurements of multiple physico-chemical
parameters. Most parameters, particularly PO4, , chlorophyll-a, and the concentration of optical
brighteners (OABs), showed a statistically significant increase (PERMANOVA, p 4, , and chlorophyll-a, exceeded recommended concentrations
for coral reef ecosystems by factors of 7 - 50 times, 600 - 1240 times, and 17 -
83 times, respectively, depending on the source of the effluents and the
distance from sewage pollution sources. Also, water turbidity exceeded 4 - 10
times the recommended value for pristine coral reefs. Coral reefs showed
significant decline in close proximity to the polluted zone, showing a
significantly different benthic community structure (PERMANOVA, p i.e.,
macroalgae, algal turf) and bare substrate. Percent coral cover and abundance
of A. palmata, showed a significant increase
with distance. Coral species richness, species diversity index, and the
variance in taxonomic distinctness were very low on reef patches adjacent to
the polluted zone, increased at a moderate distance with increasing coral cover
and co-existence of multiple species, and declined far from the pollution
source due to dominance exerted by A.
palmata. This study suggests that chronic LBSP resulted in a major decline
of one of the largest and most dense remnant stands of A. palmata across the northeastern Caribbean and that nutrient and
chlorophyll-a concentrations were
unsustainable for coral reefs. This situation requires immediate solution to
prevent further damage to these unprecedented resources. It further suggests
that chronic LBSP may synergistically magnify sea-surface warming impacts
driving corals to an increased state of risk in face of forecasted climate change
impacts. Actions to mitigate and adapt to climate change impacts on coral reefs
must require a priori controls of
LBSP to be effective.