Effect of macroalgal competition on growth and survival of juvenile Caribbean corals

Box, Steve; Mumby, Peter J.

doi:10.3354/meps342139

Cited by 291 publications

(242 citation statements)

References 41 publications

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“…1) or L. variegata (18) that also commonly bloom following herbivore exclusion (9,33,34) had large allelopathic effects on corals and could suppress coral resilience (11,13). However, not all species in these genera are allelopathic (15), making generalizations based on relatedness or functional group alone problematic. Interestingly, other strongly allelopathic macroalgae such as C. fastigiata, G. filamentosa, Liagora sp.…”

Section: Discussionmentioning

confidence: 99%

“…However, the consequences of and mechanisms driving most algal-coral interactions remain poorly understood. Recent field studies suggest that macroalgae may damage corals by (i) shading and abrasion (15), (ii) vectoring of coral disease (16), (iii) release of water-soluble compounds that stimulate harmful, coral-associated microbes (17), or (iv) transfer of hydrophobic allelochemicals by direct contact (18). However, for most of these studies, it is unclear whether the findings are particular to the macroalgal and coral species tested or are common to algal-coral interactions in general and could thus transform the way ecologists and resource managers view processes driving phase-shifts on coral reefs.…”

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confidence: 99%

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Macroalgal terpenes function as allelopathic agents against reef corals

Rasher

Stout²,

Engel³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

207

269

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During recent decades, many tropical reefs have transitioned from coral to macroalgal dominance. These community shifts increase the frequency of algal-coral interactions and may suppress coral recovery following both anthropogenic and natural disturbance. However, the extent to which macroalgae damage corals directly, the mechanisms involved, and the species specificity of algal-coral interactions remain uncertain. Here, we conducted field experiments demonstrating that numerous macroalgae directly damage corals by transfer of hydrophobic allelochemicals present on algal surfaces. These hydrophobic compounds caused bleaching, decreased photosynthesis, and occasionally death of corals in 79% of the 24 interactions assayed (three corals and eight algae). Coral damage generally was limited to sites of algal contact, but algae were unaffected by contact with corals. Artificial mimics for shading and abrasion produced no impact on corals, and effects of hydrophobic surface extracts from macroalgae paralleled effects of whole algae; both findings suggest that local effects are generated by allelochemical rather than physical mechanisms. Rankings of macroalgae from most to least allelopathic were similar across the three coral genera tested. However, corals varied markedly in susceptibility to allelopathic algae, with globally declining corals such as Acropora more strongly affected. Bioassay-guided fractionation of extracts from two allelopathic algae led to identification of two loliolide derivatives from the red alga Galaxaura filamentosa and two acetylated diterpenes from the green alga Chlorodesmis fastigiata as potent allelochemicals. Our results highlight a newly demonstrated but potentially widespread competitive mechanism to help explain the lack of coral recovery on many present-day reefs.allelopathy | chemical ecology | competition | phase shift C orals are structurally complex foundation species that generate and maintain tropical reef biodiversity. However, the direct and interactive effects of climate-induced coral bleaching (1, 2), ocean acidification (2, 3), coral disease (4), coastal overfishing, and eutrophication (5-8) have led to coral decline over wide areas. On many reefs, dramatic declines in coral cover have co-occurred with significant increases in fleshy macroalgae (9-11). Once established, macroalgae can inhibit coral recruitment and decrease herbivore grazing, producing negative feedbacks that reinforce phase shifts and further diminish reef function (12-14). Thus, local (e.g., overfishing) and global (e.g., climate) stresses may interact in complex ways to suppress coral cover, promote algal proliferation, and compromise reef resilience; such complexities provide both challenges and opportunities for managing these dynamic ecosystems (11, 13).As corals decline and macroalgae proliferate, the frequency of algal-coral interactions will increase, potentially affecting the survivorship, growth, and reproduction of remnant adult corals and new coral recruits (12, 13). However, the consequences ...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Macroalgal terpenes function as allelopathic agents against reef corals

Rasher

Stout²,

Engel³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

207

269

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“…2) may be especially damaging to corals, although Dictyota species appear variable in their allelopathic activities (34). Fortunately, other strongly allelopathic species, like Chlorodesmis, Galaxaura and Ochtodes, rarely become abundant on reefs.…”

Section: Discussionmentioning

confidence: 99%

Chemically rich seaweeds poison corals when not controlled by herbivores

Rasher

Hay

2010

Proc. Natl. Acad. Sci. U.S.A.

296

316

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Coral reefs are in dramatic global decline, with seaweeds commonly replacing corals. It is unclear, however, whether seaweeds harm corals directly or colonize opportunistically following their decline and then suppress coral recruitment. In the Caribbean and tropical Pacific, we show that, when protected from herbivores, ∼40 to 70% of common seaweeds cause bleaching and death of coral tissue when in direct contact. For seaweeds that harmed coral tissues, their lipid-soluble extracts also produced rapid bleaching. Coral bleaching and mortality was limited to areas of direct contact with seaweeds or their extracts. These patterns suggest that allelopathic seaweed-coral interactions can be important on reefs lacking herbivore control of seaweeds, and that these interactions involve lipid-soluble metabolites transferred via direct contact. Seaweeds were rapidly consumed when placed on a Pacific reef protected from fishing but were left intact or consumed at slower rates on an adjacent fished reef, indicating that herbivory will suppress seaweeds and lower frequency of allelopathic damage to corals if reefs retain intact food webs. With continued removal of herbivores from coral reefs, seaweeds are becoming more common. This occurrence will lead to increasing frequency of seaweed-coral contacts, increasing allelopathic suppression of remaining corals, and continuing decline of reef corals.A s foundation species, corals promote marine biodiversity, support a multitude of ecosystem functions, and provide goods and services critical to human societies (1, 2). However, coral reefs are in global decline, with reefs commonly converting from species-rich and topographically complex communities dominated by corals to species-poor and topographically simplified communities dominated by seaweeds (3-7). In the Caribbean, average cover of hard corals has declined by ∼80% in the last 3 decades (5) and more than 30% of the world's coral species face elevated risk of extinction (6). Monitoring (7), field experiments (8-10), and a meta-analysis (11) all indicate that herbivory is critical in preventing seaweed replacement of corals. However, the extent to which seaweeds drive these shifts by outcompeting adult corals in the absence of herbivory, or proliferate only after coral mortality is triggered by other causes (such as disease or bleaching) is debated (12-15). To compound this uncertainty, studies addressing seaweed-coral competition have: (i) produced variable results, (ii) rarely been conducted using numerous species-pairings, (iii) varied in experimental techniques (complicating comparisons), and (iv) sometimes been conducted in laboratory settings lacking ecologically realistic conditions (e.g., flow and turbulence). Thus, the general importance of competition between established seaweeds and corals remains uncertain. An understanding of mechanisms determining the outcomes of seaweed-coral interactions, and of how herbivory mediates these interactions, is needed if reefs are to be better managed, especially with the continu...

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“…Honduras (Box and Mumby, 2007) and in Florida (Lirman, 2001). It is possible that A. palmata, consisting generally of taller colonies, is not limited by macroalgal contact or shading in the same way as A. cervicornis.…”

Section: Resultsmentioning

confidence: 99%

“…Interspecific competition (Stoll and Prati, 2001;Hartley and Shorrocks, 2002) as well as aggregation is pervasive among coral communities, and is important in maintaining their viability (Karlson, 1999;Karlson et al, 2007). Heterospecific competition of corals with algae reduces coral growth and survivorship (Lirman, 2001;Box and Mumby, 2007;Crabbe, 2008). In corals, spatial arrangement, orientation and aggregation may be a key mechanism contributing to species coexistence on coral reefs (Idjadi and Karlson, 2007).…”

Section: Introductionmentioning

confidence: 99%

Topography and spatial arrangement of reef-building corals on the fringing reefs of North Jamaica may influence their response to disturbance from bleaching

Crabbe

2010

Marine Environmental Research

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International audienceKnowledge of factors that are important in reef resilience help us understand how reefs react following major environmental disturbances such as hurricanes and bleaching. Here we test factors that might have influenced Jamaican reef resilience to, and subsequent recovery from, the 2005 bleaching event, and which might help inform management policy for reefs in the future: reef rugosity and contact of corals with macroalgae. In addition,we test in the field, on Dairy Bull reef, whether aggregated colonies exhibit enhanced growth when exposed to superior competition from , as has been found by experiment with the Indo-Pacific corals and the superior competitor (Idjadi and Karlson, 2007)

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Effect of macroalgal competition on growth and survival of juvenile Caribbean corals

Cited by 291 publications

References 41 publications

Macroalgal terpenes function as allelopathic agents against reef corals

Macroalgal terpenes function as allelopathic agents against reef corals

Chemically rich seaweeds poison corals when not controlled by herbivores

Topography and spatial arrangement of reef-building corals on the fringing reefs of North Jamaica may influence their response to disturbance from bleaching

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