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Non-canopy (a) and canopy (b) bases positioned on the reef with sediment traps and clod cards attached. Sediment trap is indicated by white arrow in b. Clod card is indicated by yellow arrow in b
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Recent shifts in the presence and abundance of species on shallow Caribbean coral reefs have left octocorals as the dominant functional group on some reefs, creating an ‘animal forest’ with an associated canopy. This transition changes the reef profile potentially affecting flow and sedimentation. We examined the effects of an octocoral forest on t...
Citations
... As ecosystem engineers, they play a key role in the marine environment by transforming two-dimensional substrates into biologically complex three-dimensional fouling systems, providing habitat, food, and protection for many organisms (Gili and Coma 1998). Their baffle structures increase turbulence and local sediment deposition, which ultimately influences larval settlement and reef succession (Cerpovicz and Lasker 2021). Octocoral feeding also influences the benthic-pelagic coupling since pelagic food resources consumed by these suspension feeders are released as mucus and metabolic wastes (Leal et al. 2014). ...
Although octocorals are a key component of marine hard-bottom systems, their feeding performance is still poorly understood. Understanding carbon budget trends in octocorals’ feeding ecology seems essential to assess their role in benthic–pelagic coupling and to predict their responses to environmental changes. Herein, we provide a review of the feeding ecology of octocorals and an overall data reassessment of their carbon budgets through a systematic and comprehensive search of peer-reviewed literature published between 1960 and 2020, highlighting knowledge gaps. Overall, the feeding ecology of more than 95% of octocoral species remains unknown. Based on the available data, suspension feeding accounts for 162.8 ± 171.0% of the metabolic requirements in azooxanthellate octocorals and 28.7 ± 32.3% in zooxanthellate octocorals. Autotrophy is responsible for 156.7 ± 113.9% of the acquired carbon in zooxanthellate octocorals. However, this value is significantly lower in gorgonian phenotypes compared to other soft corals. We present a conceptual framework describing and exploring the most relevant hypotheses regarding putative advantages of octocorals over scleractinians against environmental changes, including their ability to decrease energy expenses to overcome stress events, their lower dependency on autotrophy, and the type of interaction (facultative and flexible) with their symbionts.
... In terrestrial communities, the sizes and shapes of plants are important predictors of the outcomes of interactions among individuals 71,72 and, more generally, the canopy created by assemblages of arborescent organisms can be considered an emergent property of dense stands of organisms (i.e., forests) 35 . The canopy modulates physical environmental features around the constituent organisms, thereby determining conditions within the understory habitat 51,62,73 , and the capacity of the forest to resist the destructive forces of the medium within which it operates (i.e., winds or the flow of water). While species identity in these systems undoubtedly mediates community properties, many of the emergent features of forest are attributable to the size and shape of the organisms alone (i.e., independent of the species of which they are composed). ...
Declines in abundance of scleractinian corals on shallow Caribbean reefs have left many reefs dominated by forests of arborescent octocorals. The ecological mechanisms favoring their persistence require exploration. We quantified octocoral communities from 2014 to 2019 at two sites in St. John, US Virgin Islands, and evaluated their dynamics to assess whether portfolio effects might contribute to their resilience. Octocorals were identified to species, or species complexes, and their abundances and heights were measured, with height ² serving as a biomass proxy. Annual variation in abundance was asynchronous among species, except when they responded in similar ways to hurricanes in September 2017. Multivariate changes in octocoral communities, viewed in 2-dimensional ordinations, were similar between sites, but analyses based on density differed from those based on the biomass proxy. On the density scale, variation in the community composed of all octocoral species was indistinguishable from that quantified with subsets of 6–10 of the octocoral species at one of the two sites, identifying structural redundancy in the response of the community. Conservation of the relative colony size-frequency structure, combined with temporal changes in the species represented by the tallest colonies, suggests that portfolio effects and functional redundancy stabilize the vertical structure and canopy in these tropical octocoral forests.
... (2021) found that octocorals were lost completely from all surveyed sites at Kiritimati atoll during the 2015/2016 El Niño heatwave. In contrast, in the Caribbean octocorals are generally more resistant to bleaching than stony corals, but responses are variable between species and extreme heat can cause octocoral bleaching and mortality (Lasker, 2003(Lasker, , 2005Drohan et al., 2005;Prada et al., 2010;Dias and Gondim, 2016;Goulet et al., 2017;Mccauley et al., 2018;Cerpovicz and Lasker, 2021). Octocorals on Puerto Rico and Brazil's reefs varied greatly in bleaching susceptibility by genus (Prada et al., 2010;Dias and Gondim, 2016). ...
... across the Caribbean (Lasker, 2003;Dias and Gondim, 2016;Goulet et al., 2017;Mccauley et al., 2018;Cerpovicz and Lasker, 2021). On the other hand, octocorals in Sesoko Island, Japan were more susceptible to bleaching than stony corals, with overall octocoral cover dropping from 34.4 to 0.2% (Loya et al., 2001). ...
... This suggests that there are differences in species' susceptibility or environmental conditions between these sites driving the range of stony and octocoral responses observed. Our study from eastern Australia, together with the majority of previous findings from Australia and the Caribbean, suggests that octocorals may be generally more resistant than stony corals to bleaching, but further research is needed over a greater area of the globe (Lasker, 2003(Lasker, , 2005Drohan et al., 2005;Goulet et al., 2008a, Goulet et al., 2008b, 2017Baker et al., 2015;Mccauley et al., 2018Mccauley et al., , 2020Ramsby and Goulet, 2019;Cerpovicz and Lasker, 2021). Though stony corals have relatively clear taxonomic and morphological patterns in bleaching susceptibility, octocoral studies provide little evidence for such patterns. ...
Coral reefs are amongst the most biodiverse ecosystems on earth, and while stony corals create the foundational complexity of these ecosystems, octocorals and anemones contribute significantly to their biodiversity and function. Like stony corals, many octocorals contain Symbiodiniaceae endosymbionts and can bleach when temperatures exceed the species’ upper thermal limit. Here, we report octocoral bleaching susceptibility and resistance within the subtropical Lord Howe Island coral reef ecosystem during and after marine heatwaves in 2019. Octocoral and anemone surveys were conducted at multiple reef locations within the Lord Howe Island lagoon during, immediately after, and 7 months after the heatwaves. One octocoral species, Cladiella sp. 1, experienced bleaching and mortality, with some bleached colonies detaching from the reef structure during the heatwave (presumed dead). Those that remained attached to the benthos survived the event and recovered endosymbionts within 7 months of bleaching. Cladiella sp. 1 Symbiodiniaceae density (in cells per µg protein), chlorophyll a and c 2 per µg protein, and photosynthetic efficiency were significantly lower in bleached colonies compared to unbleached colonies, while chlorophyll a and c 2 per symbiont were higher. Interestingly, no other symbiotic octocoral species of the Lord Howe Island lagoonal reef bleached. Unbleached Xenia cf crassa colonies had higher Symbiodiniaceae and chlorophyll densities during the marine heatwave compared to other monitoring intervals, while Cladiella sp. 2 densities did not change substantially through time. Previous work on octocoral bleaching has focused primarily on gorgonian octocorals, while this study provides insight into bleaching variability in other octocoral groups. The study also provides further evidence that octocorals may be generally more resistant to bleaching than stony corals in many, but not all, reef ecosystems. Responses to marine heating events vary and should be assessed on a species by species basis.
The degradation of shallow ecosystems has called for efforts to understand the biodiversity and functioning of Mesophotic Ecosystems. However, most empirical studies have been restricted to tropical regions and have majorly focused on taxonomic entities (i.e., species), neglecting important dimensions of biodiversity that influence community assembly and ecosystem functioning. Here, using a subtropical oceanic island in the eastern Atlantic Ocean (Lanzarote, Canary Islands), we investigated variation in (a) alpha and (b) beta functional (i.e., trait) diversity across a depth gradient (0–70 m), as a function of the presence of black coral forests (BCFs, order Antipatharian) in the mesophotic strata, a vulnerable but often overlooked ‘ecosystem engineer’ in regional biodiversity. Despite occupying a similar volume of the functional space (i.e., functional richness) than shallow (< 30 m) reefs, mesophotic fish assemblages inhabiting BCFs differed in their functional structure when accounting for species abundances, with lower evenness and divergence. Similarly, although mesophotic BCFs shared, on average, 90% of the functional entities with shallow reefs, the identity of common and dominant taxonomic and functional entities shifted. Our results suggest BCFs promoted the specialization of reef fishes, likely linked to convergence towards optimal traits to maximize the use of resources and space. Regional biodiversity planning should thus focus on developing specific management and conservation strategies for preserving the unique biodiversity and functionality of mesophotic BCFs.
