11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 25: Predicting Reef Futures in the Context of Climate Change
25-54
Incorporating Anticipated Patterns Of Coral Bleaching Into The Design Of Marine
Protected Areas
Will WHITE* 1 , Louis BOTSFORD 1 , Philip MUNDAY 2 , Jeffrey MAYNARD 3 ,
Geoffrey JONES 2
1 Dept. of Wildlife, Fisheries, and Conservation Biology, University of California - Davis,
Davis, CA, 2 ARC Centre of Excellence for Coral Reef Studies, James Cook University,
Townsville, Australia, 3 Climate Change Response Programme, Great Barrier Reef
Marine Park Authority, Townsville, Australia
Networks of marine protected areas (MPAs) can ensure the persistence of fish and
invertebrate populations on coral reefs by providing spatial refuges from overexploitation
and habitat destruction. However, MPAs do not afford reefs any protection against coral
bleaching. Moreover, if corals inside an MPA do not recover from an intense bleaching
event, the ensuing coral mortality can drastically reduce the diversity and complexity of
habitats inside that MPA. Since many fished species rely on complex reef habitats for
shelter, especially as juveniles, bleaching can impair the ability of MPAs to safeguard the
persistence of those species. Prior theoretical work has shown that the success of MPA
networks hinges on maintaining a size and spacing among protected habitat patches that
is sufficient to sustain population connectivity. Several authors have noted the need to
set aside larger reef areas in MPAs in order to buffer against habitat losses caused by
bleaching, but none have offered quantitative guidelines for doing so. We address this
need by incorporating spatially and temporally autocorrelated patterns of coral bleaching
(inferred from recent satellite-derived estimates of sea surface temperate on the Great
Barrier Reef) into models of fish metapopulation dynamics within marine reserve
networks. By explicitly accounting for the expected spatial pattern of habitat loss, we are
able to evaluate the relative performance of MPA networks with different spatial
configurations. Our results suggest guidelines for incorporating the possibility of
bleaching into sizing and spacing guidelines for marine reserve design in order to
minimize the detrimental impact of future bleaching events.
25-55
Quantifying The Synergistic Interaction Between Thermal Stress And Water
Quality in Determining The Differential Bleaching Susceptibility Of Coral
Communities On The Gbr
Scott WOOLDRIDGE* 1 , Terry DONE 1
1 Australian Institute of Marine Science, Townsville, Australia
In this presentation, the potential for the ambient water quality regime at a particular reef
site to act as a ‘preconditioning’ determinant of coral bleaching susceptibility is
considered for the 1998 and 2002 mass bleaching events on the Great Barrier Reef,
Australia. In the first instance, a simple empirical approach is utilised to highlight the
strong spatial coherence that exists between zones of known water quality and the
differential bleaching susceptibility (per unit temperature increase) of the resident coral
communities. In particular, reef areas that are regularly exposed to terrestrial runoff
events with high inorganic nitrogen loads are shown to display enhanced susceptibility (~
factor 2) to thermal stress. To test the robustness of this relation, a mechanistic model is
developed which implicitly captures the biological attribute of bleaching ‘resistance’ to
thermal stress. Again, poor regional water quality is shown to be a strong determinant of
bleaching resistance – potentially lowering the thermal bleaching thresholds by 1 -1.5 o C
compared to reefs in highly oligotrophic waters. The implications for siting of no-take
areas and for water-quality protection initiatives are discussed
25-56
Are Refugia Based on Triage Principles the Last Hope for Reef Systems?
Donald POTTS* 1
1 Institute of Marine Sciences, University California, Santa Cruz, Santa Cruz, CA
Current human population growth and industrialization ensure that climatic, oceanographic and
other changes affecting reef systems will continue accelerating, and probably lead to major reef
degradation and species extinctions within decades. Because coral reefs exist at land-sea-air
interfaces, they are exposed simultaneously to direct and indirect impacts of many atmospheric,
oceanographic and terrigenous factors. While research tends to concentrate on primary impacts
(e.g. coral bleaching from heating; declining calcification with ocean acidification), the same
factors often have secondary effects on many other physiological and ecological processes (e.g.
larval development and survival may be particularly sensitive to pH). When multiple factors
with multiple effects act simultaneously but at different rates, on different scales, and with
variable time-lags, they are likely to generate non-linear, synergistic interactions with
cumulative impacts much greater than the sum of the individual processes, and which may
reach disaster levels much earlier than the primary effect alone.
The rapidity of projected environmental changes suggests time available for averting the worst
impacts is very limited. Nevertheless, impacts should vary in space and time, creating
opportunities to maximize chances of persistence of some reef systems by focusing resources
on the most sustainable systems. This will require three goals for research and managerial
planning.
1. Identification of refugia (geographic, ecological, or genetic) where ecosystems and individual
species are most resistant to environmental changes.
2. Development of science-based management for longterm maintenance of refugia as
geographic, ecological and genetic reservoirs to provide eventual sources for re-establishing
reef viability elsewhere.
3. Application of triage principles holistically to entire reefs and systems to determine priorities
and urgency for research and management of reefs.
This paper outlines criteria for identifying sustainable refugia, proposes some management
goals, and compares examples of marginal oceanic (Midway Atoll) and central continental
(Great Barrier Reef) sites as potential refugia.
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