Their high feeding rates on algal turfs75 maintains low algal and sediment biomass, thereby facilitating the settlement, growth 76 and persistence of corals. As heterotrophic microbial metabolism is favored by these interaction events, the microbial community metabolism is shifted towards more. Similar phase shifts in response to shipwrecks where coral and ccadominated communities change to communities dominated by opportunist benthic organisms have been documented on other coral reefs the term phase shift refers to the observation described by done 1992, where environmental conditions favor algal overgrowth of. A case study in bonaire, dutch caribbean article pdf available in marine technology society journal 486. A phase shift occurs on a coral reef when the cover of a substrate by scleractinian corals is reduced in favor of macroalgal dominance, and resilience of the former condition is retarded because of ecological processes andor environmental conditions. This dissertation investigated the responses of a common branching sponge, aplysina cauliformis, to algal contact.
Coralalgal phase shifts alter fish communities and reduce fisheries. The role of macroalgae in perpetuating the degraded state of. However, cage studies indicate that reduction in herbivory can lead to the proliferation of algae even in the absence of eutrophication. Norris1 caribbean coral reefs have transformed into algaldominated habitats over recent decades. Reductions in herbivory caused by overfishing may enhance the likelihood of organic pollution causing a coralalgal phase shift following major disturbances. Individual and population responses of the caribbean sponge. We define resilience as the ability of reefs to absorb recurrent disturbances e. Pdf coral reef fisheries support tens of millions of people, mostly in developing countries. Macroalgae, nutrients and phase shifts on coral reefs. It is widely recognized that persistence times of these shifts have increased in the past few decades. Phaseshifts on coral reefs multiple drivers, multiple states. Coral reef fisheries support tens of millions of people, mostly in developing countries. Phase shifts, herbivory, and the resilience of coral reefs to.
A topical example is the phase shift of coral reefs from coral to macroalgal dominance mcmanus and polsenberg 2004. Based on this threshold, only 25 of the 1851 reefs coral algal interface, algae exude dissolved organic carbon doc in close proximity to coral, which causes a shift in the microbial community towards more heterotrophic metabolisms fig. Losing this crucial functional group can lead to phase shifts from coral to algal dominated reefs after major disturbances. This has motivated coral reef management responses that include restriction and regulation of fishing. Paper progression of the coralalgal phase shift in the. Pdf a coralalgal phase shift in mesoamerica not driven. Many coral reefs worldwide have undergone phase shifts to alternate, degraded assemblages because of the combined effects of overfishing, declining water quality, and the direct and indirect impacts of climate change 19. Evaluating management strategies to optimise coral reef. This study assessed the progression of a coral algal phase shift at a fringing reef around bonaire, dutch caribbean, by comparing current coral and algal benthic cover to historical data, from 1997 to 2008, at a site nearby.
Great barrier reef and the processes underlying a phase shift to macroalgal dominance figure 1a. At the coral algal interface, algae exude dissolved organic carbon doc in close proximity to coral, which causes a shift in the microbial community towards more heterotrophic metabolisms. On south pacific coral reefs, the macroalga turbinaria 26 ornata has expanded its range and habitat but, unlike algae that often dominate after 27 phase shifts, t. Pdf progression of the coralalgal phase shift in the. Coral reefs are under increasing threat from a diversity of stressors.
The recent invasion of the indopacific lionfish pterois volitans onto shallow reefs of the caribbean and bahamas has. Paradigm shift in the understanding of coral algal uptake research led by southern cross university postgraduate student ms nadine boulotte, scientists from scus marine ecology research centre, the university of. Tropical herbivores provide resilience to a climate. This change is often associated with habitat loss and overharvesting of herbivorous fishes, particularly parrotfishes and surgeonfishes 69. Sewage diversion in the late 1970s led to natural recovery and a reverse phase shift favoring coral reefs. Coralalgal interactions lesion healing macroalgae phase shifts corals have an ability to recover from disturbance through the regeneration of tissue, but macroalgae are believed to impede this process. Here, we experimentally examine the resilience of coral dominated assemblages on the great barrier reef and the processes underlying a phase shift to macroalgal dominance figure 1a. The recent invasion of the indopacific lionfish pterois volitans onto shallow reefs of the caribbean and bahamas has had significant, negative, effects on. These reefs become drab and dark in color and have been referred to. A coralalgal phase shift in mesoamerica not driven by changes in. One well documented such phase shift has been from coral to algal 25 domination on tropical reefs. The coralalgal phase shift results in reduced biodiversity and.
Coralalgal phase shifts in which coral cover declines to low levels and is replaced by algae have often been documented on coral reefs worldwide. Crustose coralline algae cca, in contrast, are generally less detrimental to corals than are other types of algae barott et al. Coralalgal competition a major concern in assessments of global coral reef status is the shift from coral to algal dominance on reefs jameson et al. Between 1996 and 2006, phase shift severity decreased in the caribbean, did not. Effects of live coral, epilithic algal communities and substrate type on algal recruitment received. Trend in coralalgal phase shift in the mandapam group of islands. During a phase shift, a beautiful, colorful reef with high coral diversity can transform into a reef dominated by a single species. In this study, the type of benthic macroalgae deposited on coral skeleton. Coral recovery on phaseshifted reefs depend upon the type of. Assessing evidence of phase shifts from coral to macroalgal. Coralalgal phase shifts alter fish communities and reduce. Klumpp, 1997, stress, nutrient, algae, phase shift, icrs8, on the great barrier reef, abundant macroalgae on inshore reefs may indicate or model reef degradation, since these reefs receive high input of terrestrial nutrients and sediments.
Continual stress by such variables as human activity, diseases and natural impacts such as hurricanes may eventually result in a phase shift of the system, going from coral dominated to macroalgae. The challenge is to reverse this decline and enhance the resilience of coralreef ecosystems 10. Marine protected areas enhance coral reef functioning by. Progression of the coralalgal phase shift in the caribbean. The bionic coral design was developed as an optimization between algal growth rates, optical performance and the outcome of optical models fig. Browsing herbivores are thought to provide critical resilience to 77 coral reefs by consuming canopy forming seaweeds and facilitating phase shift reversals of 4. Here, we experimentally examine the resilience of coraldominated assemblages on the great barrier reef and the processes underlying a phase shift to macroalgal dominance figure 1a. Phase shift to algal dominated communities at mesophotic. I conclude that nutrient overloads can contribute to reef degradation, but that they are unlikely to lead to phase shifts simply by enhancing algal growth rates and hence allowing. Pdf coral reef fishing and coralalgal phase shifts. The worlds coral reefs are in decline, with many exhibiting a phase shift from coral to macroalgal dominance 16.
Prehistorical and historical declines in caribbean coral reef accretion rates driven by loss of parrot. Current management is not adequate to prevent further declines in marine resources. Coral macroalgae a 02040 6080 7 6 5 4 3 2 per cent cover distance from pre. Fishing on reefs can be classified into three stages. As heterotrophic microbial metabolism is favored by these interaction events, the microbial community metabolism is shifted towards more copiotrophic.
The bestdocumented case of a coralalgal phase shift refers to the northern coast of jamaica. Coral recovery on phase shifted reefs depend upon the type of macroalgae present by justin nicholas voss submitted to the faculty of halmos college of natural sciences and oceanography in partial fulfillment of the requirements for the degree of master of science with a specialty in. This phase shift done, 1992 could be a result of chronic pressures which favour. Conditions under which reefs bounce back from bleaching events or shift from coral to algal dominance are unknown, making it difficult to predict and plan for differing reef responses under climate change. Pdf progression of the coralalgal phase shift in the caribbean. Frequently asked questions palmyra atoll and kingman reef. Thus, on florida keys reefs that are experiencing phase shifts or temporary algal blooms, coral settlement rates may be reduced despite the availability of appropriate substrate. Degradation of coral reefs often involves a phase shift from abundant coral to abundant macroalgae. Coral reef resilience assessment of the pemba channel. Coralalgal phase shifts in which coral cover declines to low levels and. Fishing effort is already above the multispecies sustainable yield, and, at its current level, will likely lead to a shift to algal. Reef conservation uk 2015 abstracts zoological society of.
The present study revealed proliferation of macroalgae modifying coral reef ecosystems in a different manner due to diseases and. Microbial bioenergetics of coralalgal interactions peerj. This study assessed the progression of a coralalgal phase shift at a fringing reef around bonaire, dutch caribbean, by comparing current coral and algal benthic cover to historical data, from 1997 to 2008, at a site nearby. Many coral reefs worldwide have undergone phase shifts to alternate. Climate change impacts most warmwater corals exhibit a symbiotic relationshipwithsinglecelledalgaezooxanthellae from which they derive much of their nutrition. In this case, the composition of the reefassociated fish assemblage will change and human communities relying on reef fisheries for income and food security may be negatively impacted. I conclude that nutrient overloads can contribute to reef degradation, but that they are unlikely to lead to phase shifts simply by enhancing algal growth rates and hence allowing overgrowth of corals. Sleeping functional group drives coralreef recovery. Prehistorical and historical declines in caribbean coral reef. Coral algal competition a major concern in assessments of global coral reef status is the shift from coral to algal dominance on reefs jameson et al.
The term coral algal phase shift refers to the phenomenon of coral reefs shifting to unusually low levels of coral cover, associated with persistent states of high cover of. Climateinduced coral bleaching is among the greatest current threats to coral reefs, causing widespread loss of live coral cover. These reefs have undergone a phase shift from coral dominated to algal dominated ecosystems, and in many cases other functional groups such as sponges are now the predominant organisms on many reefs. Overfishing and nutrient pollution can damage coral reefs in part by increasing coralalgal competition. This study contributes to the scientific knowledge of coralalgal phase shifts in the bonaire reef ecosystem and the broader scientific reef. Yearlong monitoring of physicochemical and biological. Predicting climatedriven regime shifts versus rebound.
Here the authors simulate these stressors in a three year field experiment, and show that. Causes or consequences of reef degradation, mccook, l. Browsing herbivores are thought to provide critical resilience to coral reefs by consuming canopy forming seaweeds and facilitating phase shift reversals of degraded reefs back to coral dominant states bellwood et al. Coral abundance on reefs around the world began to decline several decades ago gardner et al. The coralalgal phaseshift phenomenon in coral reefs is generally believed to be the result of gradual increases in stress due to loss of herbivory andor increases in nutrient levels, but is usually triggered by a major perturbation such as a hurricane, crownofthorns infestation, outbreak of coral disease, or bleaching event. Hatcher and larkum 1983 found experimentally, using cages and nitrogen additions, that the addition of nutrients tended to increase algal production, but the standing stock only increased when grazers were excluded. A phase shift towards an algaedominated system may accompany coral loss. Cca can even be beneficial for corals by providing settlement cues and substrate for coral larvae morse. Based on this threshold, only 25 of the 1851 reefs s hift r e c o v e r y figure 1 recovery and regime shift dynamics on seychelles coral reefs. Coral reefs can undergo relatively rapid changes in the dominant biota, a phenomenon referred to as a phase shift. Perspective warmwater coral reefs and climate change. Here, we experimentally manipulated the density of large herbivorous fishes to test their influence on the resilience of coral assemblages in the aftermath of regional. Observations of a rapid decline in invasive macroalgal cover.
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