Trouble in Murky Seas for Reef Fish

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Trouble in murky seas for distributions. False orange clownfish locomotion, which are not critical to strongly prefer clear water, and are rarely moment-to-moment survival – like reef fish found in turbid reefs, while the cinnamon having no emergency fund saved up at the clownfish and spiny chromis members of bank. the family are common in both turbid inshore and clear offshore reefs. Contrastingly, spiny chromis and false orange clownfish protected their ability to Using a microscope to take a close look at increase their metabolic rate, even at very thin sections of the tiny gills, the team high sediment concentrations. The investigated whether suspended sediments authors chalked this up to compensatory lead to gill damage and reduced gas responses somewhere in the myriad of exchange. The structures on the gills that physiological steps involved in translating absorb oxygen in the blood and remove oxygen uptake into metabolic waste products (lamellae) of cinnamon performance, like heart or haemoglobin clownfish and spiny chromis were shorter function. That the false orange clownfish,

RESPIRATION after sediment exposure, implying less which is only found in clear water, functional gas exchange surface. In outperformed the cinnamon clownfish, Coral reefs are on the front line of climate contrast, the team found that the distance which tolerates turbid reefs, took the change, and they are losing ground. that gases had to travel across the lamellae authors by surprise. They suggest that the Unfortunately, reef inhabitants have to was reduced in all three species. This poor tolerance of the false orange combat more than coral bleaching and bucks the usual trend – sediment-exposed clownfish’s sea anemone partner to elevated temperatures alone: their pristine gills usually take defensive action, like suspended sediments may limit the homes are also getting dirtier. And while thickening the protective cell layers or distribution of its clownfish lodger. we know that poor water quality causes increasing mucus secretion, which shield species decline and ecological changes in their fragile gill structures at the cost of The frantic pace of human development in reefs, the mechanisms at play remain increasing the distance that gases must scenic coastal locales stirs up the water mysterious. Perhaps sediments directly diffuse through the gill. However, whether and challenges the inhabitants of the reef. influence the physiology of reef fishes by this reduced diffusion distance was a Given the complex interactions between irritating or damaging their gills and response to compensate for gill damage, or the direct effects of sediment exposure on impairing oxygen uptake into the blood. simply due to abrasion of the gill tissue, fish physiology, the potential responses of Additionally, indirect effects like the loss was unresolved. other reef inhabitants – such as host of visual range can prevent larvae from anemones – and other stressors such as finding shelter or prey. Wading into the The team then moved on to investigate ocean acidification, the future of coral murk and gloom, Sybille Hess and her whether the alterations that they had reefs is as clear as mud. colleagues, based at James Cook identified in the gill influenced the fish’s 10.1242/jeb.170316 University and the University of metabolism, as damaged gills can limit Queensland, Australia, sought a metabolic performance. They found that mechanistic link between water quality the cinnamon clownfish was unable to Hess, S., Prescott, L. J., Hoey, A. S., McMahon, S. A., Wenger, A. S. and Rummer, J. L. (2017). and physiology. They focused on three increase its metabolic rate as much as Species-specific impacts on gill structure and species, cinnamon clownfish unexposed fish when performing exercise function in coral reef fishes. Proc. R. Soc. B. 284, (Amphiprion melanopus), false orange and had a higher baseline metabolic rate 20171279. doi: 10.1098/rspb.2017.1279. clownfish (Amphiprion percula) and while at rest. This leaves them with less Brittney Borowiec spiny chromis (Acanthochromis energy available for ‘extracurricular McMaster University polyacanthus), with different activities’, such as reproduction and [email protected]

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