Trophic plasticity of mixotrophic corals under contrasting environments

Abstract

1. Mixotrophic organisms can derive nutrition from both auto-and heterotrophy, which allows them to use a variety of trophic pathways to sustain their metabolic demands under variable conditions. Therefore, when facing environmental change, these organisms are expected to demonstrate an intrinsic ability to acclimatize through trophic plasticity.2. Scleractinian corals are ecologically important mixotrophs, but understanding their trophic plasticity has been impaired by an oversimplification towards inconsistent proxies of coral diet and overlooking intraspecific variability.3. Here, we applied a Bayesian analysis of carbon and nitrogen stable isotope data to determine the trophic niches of six common species of scleractinian corals and their associated endosymbionts, and combined it with an unsupervised machine learning algorithm to identify trophic behaviours and strategies.4. We found a variable amount of nutritional plasticity identified by different trophic behaviours within and between mixotrophic corals living under the same environmental conditions. Furthermore, we observed changes in trophic plasticity across environmental conditions. Corals from variable environments had larger host and endosymbiont niches than corals from stable environments. In addition, deeper corals had niches indicating a greater degree of heterotrophy than shallow corals. Collectively, corals exhibited distinct trophic strategies by promoting trophic niche differentiation along the mixotrophic continuum and conspecific individual colonies displayed high trophic variation. 5. Our results provide a foundation to understand how mixotrophic organisms may adjust their nutrition in response to ongoing global environmental change and the consequential modification of benthic assemblages.

Influence of upwelling on coral reef benthic communities: a systematic review and meta-analysis

“…By contrast, hard coral cover was not impacted by seasonal upwelling but increased by 62% in upwelling compared with non-upwelling sites. This can likely be explained by the difference in response times of fleshy macroalgae and hard corals to increases in allochthonous energy resources, although this requires further research [ 68 ]. Future studies could focus on quantifying the responses of different benthic groups to gradients in energy availability over different time-scales, particularly organisms such as hard corals that employ a mixotrophic feeding strategy [ 18 ].…”

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“…The diet of corals, however, goes beyond a fixed trophic strategy based on the morphology of polyps and corallites [41]. There is a need to consider trophic plasticity Corals -Habitat Formers in the Anthropocene as a critical factor of resistance to environmental stress [42].…”

“…In this way, it is possible to recognize changes in trophic strategy (i.e. trophic plasticity) among different coral species living under the same environmental conditions [41]. This is particularly important in the ecological success of corals living in subtropical areas (Figure 2) [23] due to their capacity of using different nutrient sources to gain metabolic energy.…”

Coral fluorescence: a prey-lure in deep habitats

“…In contrast, MCEs are characterized by much lower light intensities, i.e., 1–10% of surface irradiance, and a narrower spectrum centered around the blue region of the spectrum 37 , resulting in a possibly impaired ability to acquire energy through photosynthesis 38 . While there is evidence of mixed nutritional sources for corals along a depth gradient 38 – 40 , some species do present a transition from photosynthesis-based nutrition (autotrophic) to predation-based nutrition (heterotrophic) in shallow versus deep corals 18 , 41 – 43 . Thus, it can be expected that corals inhabiting deeper reefs should possess prey-lure abilities and/or prey-capture mechanisms.…”