Coral reef ecosystem collapse in Puerto Rico: Combined impacts of long-term local anthropogenic factors and climate change

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Date
2009-11Author
Hernández-Delgado, Edwin A.
Hernández-Pacheco, Raisa
Sabat, Alberto M.
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Show full item recordAbstract
Coral reefs are under increasing threats that have
undermined their resistance ability to disturbance,
their ecological functions and their ecosystem
resilience. A combination of long-term impacts by
natural factors (i.e., hurricanes, meso-scale gyres), a
sort of local human factors (i.e., water quality
degradation, sediment- and nutrient-loaded runoff,
overfishing), and climate-related factors (i.e., sea
surface warming, bleaching) have resulted in net
coral decline trends along the wider Caribbean
region. This study is aimed at addressing long-term
ecological change in coral reef benthic communities
across different coral reefs in Puerto Rico (PR). This
presentation is focused in Playa Carlos Rosario,
Culebra Island, with 12 years of data.
Coral species richness declined by a mean factor of
54% during the period of 1997 to 2009. Percent
living coral cover plummeted by 81%, or an annual
mean of 6.8% loss. Coral cover loss following the
2005 unprecedented sea surface warming and mass
bleaching event was 66%. Total algal cover has
increased by a factor of 91%, but macroalgal cover
has increased by 1,064%, or a mean annual
increment of 89%. This suggest unequivocal impacts
by recurrent sediment- and nutrient-loaded runoff
pulses, in combination with recurrent impacts from
meso-scale gyres that can increase background
chlorophyll a concentrations by a 5-10 fold factor.
Coral:macroalgal ratios have declined by 97%.
Mortality trends in Montastraea annularis spp.
complex has averaged 70% during the same period
and 48% since 2005. These trends are widespread
through different locations in PR, suggesting that
coral reefs are in the peril of an ecosystem collapse.
There is a need to develop mathematical models to
predict what would be the future of Caribbean-wide
coral reefs in the face of climate change impacts.