Climate Warming, Marine Protected Areas and the Ocean-Scale Integrity of Coral Reef Ecosystems

Abstract

Coral reefs have emerged as one of the ecosystems most vulnerable to climate variation and change. While the contribution of a warming climate to the loss of live coral cover has been well documented across large spatial and temporal scales, the associated effects on fish have not. Here, we respond to recent and repeated calls to assess the importance of local management in conserving coral reefs in the context of global climate change. Such information is important, as coral reef fish assemblages are the most species dense vertebrate communities on earth, contributing critical ecosystem functions and providing crucial ecosystem services to human societies in tropical countries. Our assessment of the impacts of the 1998 mass bleaching event on coral cover, reef structural complexity, and reef associated fishes spans 7 countries, 66 sites and 26 degrees of latitude in the Indian Ocean. Using Bayesian meta-analysis we show that changes in the size structure, diversity and trophic composition of the reef fish community have followed coral declines. Although the ocean scale integrity of these coral reef ecosystems has been lost, it is positive to see the effects are spatially variable at multiple scales, with impacts and vulnerability affected by geography but not management regime. Existing no-take marine protected areas still support high biomass of fish, however they had no positive affect on the ecosystem response to large-scale disturbance. This suggests a need for future conservation and management efforts to identify and protect regional refugia, which should be integrated into existing management frameworks and combined with policies to improve system-wide resilience to climate variation and change.

Trajectories and magnitude of change in coral reef fish populations in Philippine marine reserves: a meta-analysis

“…The structural complexity of coral reefs (e.g., percent live hard coral cover, slope and rugosity) is critical in the recovery of reef fish assemblages (Friedlander et al 2003;Russ et al 2005;Maliao et al 2008;Graham et al 2008). In this study, a comprehensive analysis of temporal and spatial changes in habitat structure could not be conducted because habitat data were not reported in most of the studies included in the meta-analyses.…”

“…However, Philippine reserves are usually established on reefs that were formerly fishing grounds, and many suffered from the deleterious effects of overfishing and illegal fishing (e.g., blast fishing) before their establishment as reserves (White et al 2000;Alcala and Russ 2002). The 1997/1998 El Niño Southern Oscillation (ENSO) further resulted in the massive decline of live coral cover in the Philippines (Arceo et al 2001) and subsequent decline in reef fish populations in many parts of the world (Graham et al 2008). A recent report of Marcus et al (2007) states that based on 28 coral reef fishing grounds examined in central Philippines, the magnitude of coral-reef destruction is alarming; these authors reported that only 12% of the reefs are covered with live coral and the rest is covered with abiotic structures (69%, e.g., coral rubble) and Sargassum (11%).…”

“…A recent report of Marcus et al (2007) states that based on 28 coral reef fishing grounds examined in central Philippines, the magnitude of coral-reef destruction is alarming; these authors reported that only 12% of the reefs are covered with live coral and the rest is covered with abiotic structures (69%, e.g., coral rubble) and Sargassum (11%). Although only a few fish species are heavily coral dependent, most reef fishes are reliant on the reef matrix for protection at some stage in their life cycle (Graham et al 2008). Hence, the minimal overall impact of Philippine reserves in enhancing fish density is probably linked to persistent poor habitat condition and past climatic events.…”

“…These include the population size and species composition at the onset of protection and the life history characteristics of the fish species under consideration (Hutchings 2000;Jennings 2001), reserve age, size, spacing and habitat structural complexity Hastings and Botsford 2003;Russ et al 2005;Claudet et al 2008;Graham et al 2008), and the magnitude of reduction of fishing mortality in the reserve as a function of enforcement (Russ 2006;Guidetti et al 2008). Top-trophic level species (e.g., piscivores) are preferentially fished, and thus expected to respond positively with protection because of the elimination (or reduction) of fishing mortality in the reserves (Roberts 1997;Jennings 2001;Russ 2006).…”

Transitional states in marine fisheries: adapting to predicted global change

“…Fish-community effects were apparent throughout the WIO but were patchily distributed, reflecting the dependencies of individual species on corals. In the most severely impacted locations of the northern Indian Ocean, fish diversity declined by 50 per cent, with corallivorous and planktivorous fishes dependent on corals for food and shelter declining by at least 76 and 68 per cent, where coral cover declined by more than 50 per cent (figure 3a,b; Graham et al 2008;MacNeil & Graham 2010).…”