Farming behaviour of reef fishes increases the prevalence of coral disease associated microbes and black band disease

Abstract

Microbial community structure on coral reefs is strongly influenced by coral–algae interactions; however, the extent to which this influence is mediated by fishes is unknown. By excluding fleshy macroalgae, cultivating palatable filamentous algae and engaging in frequent aggression to protect resources, territorial damselfish (f. Pomacentridae), such as Stegastes , mediate macro-benthic dynamics on coral reefs and may significantly influence microbial communities. To elucidate how Stegastes apicalis and Stegastes nigricans may alter benthic microbial assemblages and coral health, we determined the benthic community composition (epilithic algal matrix and prokaryotes) and coral disease prevalence inside and outside of damselfish territories in the Great Barrier Reef, Australia. 16S rDNA sequencing revealed distinct bacterial communities associated with turf algae and a two to three times greater relative abundance of phylotypes with high sequence similarity to potential coral pathogens inside Stegastes 's territories. These potentially pathogenic phylotypes (totalling 30.04% of the community) were found to have high sequence similarity to those amplified from black band disease (BBD) and disease affected corals worldwide. Disease surveys further revealed a significantly higher occurrence of BBD inside S. nigricans 's territories. These findings demonstrate the first link between fish behaviour, reservoirs of potential coral disease pathogens and the prevalence of coral disease.

Responses of Coral-Associated Bacterial Communities to Local and Global Stressors

“…For example, within the territory of the damselfishes, Stegastes apicalis and S. nigricans, there were 2-3-fold increases in coral pathogens in the microbiome and a higher prevalence of corals with signs of black band disease. These Stegates species normally exclude macroalgae and cultivate filamentous algae, thus providing a trophic link among fish behavior, coral pathogen reservoirs and coral disease (Casey et al, 2014). Other fishes (i.e., Chaetodontidae) may also act directly as disease vectors , however, functionally diverse fish communities have been suggested to alleviate coral disease ) and five Chaetodontidae and one Labridae species actually slowed the progression of blackband disease (Cole et al, 2009).…”

Microbiome shifts and the inhibition of quorum sensing by Black Band Disease cyanobacteria

“…These observations also do not rule out a hypothesis that the spatiotemporal distribution of BBD cases on the reef correlates with water quality parameters (Page and Willis, 2006), which may serve as environmental triggers for community shifts mediated by BBD members. Alternate hypotheses, including vector-borne transmission from non-coral reservoirs or between diseased and healthy corals have also been suggested (Aeby and Santavy, 2006;Casey et al, 2014). Cyanobacteria similar to those associated with BBD, including the genera Leptolyngbya, Geitlerinema, Oscillatoria and Phormidium, were found in microbiomes associated with turf, crustose coralline and macroalgae, potentially implicating these organisms as alternate hosts or reservoirs of the pathogens (Barott et al, 2011).…”

Coral Mucus Is a Hot Spot for Viral Infections

“…The polysaccharide-protein composition of this organic matrix constitutes a nutrient-rich ecological niche harboring a great diversity of symbiotic microorganisms for corals (3,4). Mucosal bacteria, for example, provide corals a part of their nutritive needs (5,6) and also protection from the surrounding pathogens (7,8). Such a diverse and multifunctional microbiota is now regarded as a powerful arsenal allowing corals to face environmental stresses by rapid structural adjustments (9)(10)(11).…”