Climate Change Leads to a Reduction in Symbiotic Derived Cnidarian Biodiversity on Coral Reefs

Abstract

Symbiotic relationships enable partners to thrive and survive in habitats where they would either not be as successful, or potentially not exist, without the symbiosis. The coral reef ecosystem, and its immense biodiversity, relies on the symbioses between cnidarians (e.g., scleractinian corals, octocorals, sea anemones, jellyfish) and multiple organisms including dinoflagellate algae (family Symbiodiniaceae), bivalves, crabs, shrimps, and fishes. In this review, we discuss the ramifications of whether coral reef cnidarian symbioses are obligatory, whereby at least one of the partners must be in the symbiosis in order to survive or are facultative. Furthermore, we cover the consequences of cnidarian symbioses exhibiting partner flexibility or fidelity. Fidelity, where a symbiotic partner can only engage in symbiosis with a subset of partners, may be absolute or context dependent. Current literature demonstrates that many cnidarian symbioses are highly obligative and appear to exhibit absolute fidelity. Consequently, for many coral reef cnidarian symbioses, surviving changing environmental conditions will depend on the robustness and potential plasticity of the existing host-symbiont(s) combination. If environmental conditions detrimentally affect even one component of this symbiotic consortium, it may lead to a cascade effect and the collapse of the entire symbiosis. Symbiosis is at the heart of the coral reef ecosystem, its existence, and its high biodiversity. Climate change may cause the demise of some of the cnidarian symbioses, leading to subsequent reduction in biodiversity on coral reefs.

Microbiome composition is shaped by geography and population structure in the parasitic wasp Asobara japonica, but not in the presence of the endosymbiont Wolbachia

“…Such disruption could have been caused potentially by a strong fluctuation in temperature, as symbionts appear to be sensitive to increases in temperature (Corbin et al, 2017;Hurst et al, 2000;Sumi et al, 2017;van Opijnen & Breeuwer, 1999) and show the general geographical pattern of lower prevalence in warmer regions (Corbin et al, 2017). Moreover, experimental heat exposure was able to eliminate Wolbachia in twospotted spider mites (van Opijnen & Breeuwer, 1999), and a green stinkbug (Kikuchi et al, 2016) and symbiont reduction in response to increasing temperatures was found in coral reefs (Goulet & Goulet, 2021). Although the underlying reasons for admixed ancestry in some Kobe samples remain speculative, our findings suggest that environmental factors and associated changes in the bacterial community composition may have played a role.…”

Comparative physiology reveals heat stress disrupts acid–base homeostasis independent of symbiotic state in the model cnidarian Exaiptasia diaphana

“…Symbiosis can facilitate physiological adaptation, as partner switching or ‘symbiont shuffling’ can provide mechanisms besides genetic evolution by which organisms can adapt to changing surroundings ( Cunning et al, 2015b ; Toby Kiers et al, 2010 ). Yet the interdependence between partners can also magnify the environmental sensitivities of mutualistic organisms, as both species must maintain function together under new conditions ( Apprill, 2020 ; Bénard et al, 2020 ; Goulet and Goulet, 2021 ). Therefore, we need to be precise in our understanding of when an abiotic stressor such as elevated temperature is affecting a host, its symbiont(s), both partners, or even modifying the dynamics of the interaction itself.…”

Anemone bleaching impacts the larval recruitment success of an anemone-associated fish

“…Across the world's coral reefs, biodiversity is supported by the mutualisms that exist between organisms such as corals or sea anemones, and their algal endosymbionts Symbiodiniaceae (Goulet and Goulet 2021). In addition to supporting diverse species assemblages through the creation of habitat and resources Chomicki et al 2019), these relationships also support secondary mutualisms, such as those between fishes and anemones (Fautin 1991).…”