• Bet-hedging. In the face of uncertainty on adaptation rates and whether any
adaptation will be genetically or phenotypically driven, a ‘bet-hedging’ strategy
may be more appropriate based on a combination of the number of connections
prioritized in the above scenarios and the ranking of the most important
connections.
In the Bahamian example, Mumby et al. (2011) found that the bet-hedging
scenario produced a reserve design that was most similar to the ‘Adaptation
inadequate, but genetic’ scenario, where a genetic basis for adaptation is present in
existing communities. They conclude that although it was difficult to create a
compromise strategy that hedged against all scenarios, there was a subset of 15 %
of sites that were selected under all scenarios, making them ideal candidates for
early protection and inclusion in a reserve network.
12.3.2 Water Quality and Coral Bleaching
Wooldridge and Done (2009) used a Bayesian approach for modeling and data
integration to shed new light on ecological processes associated with a possible
interaction between warming ocean temperatures and water quality. The mechanistic basis for this link is that elevated dissolved inorganic nitrogen (DIN)
stimulates enlarged (suboptimal) coral symbiont populations with higher metabolic demands during periods of elevated irradiance and temperature. More energy
consumed by the symbionts themselves in turn causes reduced translocation of
energy to the host coral, dampening host productivity and CO 2 production. This in
turn causes less CO 2 to diffuse to the symbionts. A limited CO 2 substrate around
the Rubisco enzyme in the symbionts is postulated to disrupt their ‘‘dark’’ photosynthetic reactions, thereby leading to bleaching (Wooldridge 2009a). Thus, high
levels of DIN make the coral-algal symbiosis less stable so that bleaching effectively happens at lower temperatures than would be the case if DIN levels
were low.
Wooldridge and Done (2009) tested the DIN link by showing that observed
bleaching patterns on the GBR in 1998 and 2002 (Berkelmans et al. 2004) correlated better when coastal DIN and thermal history were included as additional
explanatory variables over temperature stress alone (predictive accuracy of 84 vs
73 % respectively). The onset of bleaching occurred *1–1.5 °C higher in reefs
with good water quality and lower thermal history (Fig. 12.4). The implications for
reef management are that managing nutrient runoff from rivers can have a tangible
benefit to coral reefs and improve their resilience while they cope with the impacts
of warming waters as a result of climate change (Wooldridge 2009b). These
studies also provide opportunities for further integration by including socio-economic modeling to assess and optimize the tradeoffs between the economic costs
of reducing fertilizer use and the benefits to the ecology of the reef and industries
which are dependent on a healthy reef, such as tourism (Thomas et al. 2009).
330
S. J. Weeks et al.
adaptation will be genetically or phenotypically driven, a ‘bet-hedging’ strategy
may be more appropriate based on a combination of the number of connections
prioritized in the above scenarios and the ranking of the most important
connections.
In the Bahamian example, Mumby et al. (2011) found that the bet-hedging
scenario produced a reserve design that was most similar to the ‘Adaptation
inadequate, but genetic’ scenario, where a genetic basis for adaptation is present in
existing communities. They conclude that although it was difficult to create a
compromise strategy that hedged against all scenarios, there was a subset of 15 %
of sites that were selected under all scenarios, making them ideal candidates for
early protection and inclusion in a reserve network.
12.3.2 Water Quality and Coral Bleaching
Wooldridge and Done (2009) used a Bayesian approach for modeling and data
integration to shed new light on ecological processes associated with a possible
interaction between warming ocean temperatures and water quality. The mechanistic basis for this link is that elevated dissolved inorganic nitrogen (DIN)
stimulates enlarged (suboptimal) coral symbiont populations with higher metabolic demands during periods of elevated irradiance and temperature. More energy
consumed by the symbionts themselves in turn causes reduced translocation of
energy to the host coral, dampening host productivity and CO 2 production. This in
turn causes less CO 2 to diffuse to the symbionts. A limited CO 2 substrate around
the Rubisco enzyme in the symbionts is postulated to disrupt their ‘‘dark’’ photosynthetic reactions, thereby leading to bleaching (Wooldridge 2009a). Thus, high
levels of DIN make the coral-algal symbiosis less stable so that bleaching effectively happens at lower temperatures than would be the case if DIN levels
were low.
Wooldridge and Done (2009) tested the DIN link by showing that observed
bleaching patterns on the GBR in 1998 and 2002 (Berkelmans et al. 2004) correlated better when coastal DIN and thermal history were included as additional
explanatory variables over temperature stress alone (predictive accuracy of 84 vs
73 % respectively). The onset of bleaching occurred *1–1.5 °C higher in reefs
with good water quality and lower thermal history (Fig. 12.4). The implications for
reef management are that managing nutrient runoff from rivers can have a tangible
benefit to coral reefs and improve their resilience while they cope with the impacts
of warming waters as a result of climate change (Wooldridge 2009b). These
studies also provide opportunities for further integration by including socio-economic modeling to assess and optimize the tradeoffs between the economic costs
of reducing fertilizer use and the benefits to the ecology of the reef and industries
which are dependent on a healthy reef, such as tourism (Thomas et al. 2009).
330
S. J. Weeks et al.