New research confirms that drastic changes in ocean salinity from, for example, severe freshwater flooding, as recently experienced off the coast of north-east Queensland from abnormal monsoonal conditions, provoke a similar stress response in corals as extreme heating, resulting in “freshwater bleaching” and if unabated, coral death.Researchers from the ARC Centre of Excellence for Coral Reef Studies at James Cook University (Coral CoE) and University of Technology Sydney (UTS) report that extreme and sudden changes in salinity, or the ocean salt concentration, cause a biochemical response in corals that is similar to marine heatwaves, but in some ways, more damaging to their cells ability to function.
sensitive organisms, known to only tolerate slight changes in their
environment. Thriving in clear, sunlit waters – the majority of reef-building
corals are found in tropical and subtropical waters with a salinity between 32
to 42 parts per thousand,” said senior author Prof David Miller of
recent flooding, there are reports that nearshore reefs were exposed to roughly
half the normal ocean salinity.”
research shows that this kind of environmental change causes a shock response
in corals that prevents normal cell function.”
researchers used the sequenced genome – a biological blueprint – of the common
reef-building coral, Acropora millepora to detect changes in the coral’s biology.
sophisticated labs at the National Sea Simulator, we put
both young and adult corals under a salinity stress test to see how they
respond to differing salinity concentrations,” said co-author Dr
Jean-Baptiste Raina of UTS.
that there was a common response between both coral life-stages – with the
younger corals being more sensitive to low salinity conditions, but faring
slightly better with exposure over time.”
general, we found that the coral’s cells launch a similar chemical response to
reduced salinity as they do for heat stress,” Prof Miller explained.
unlike the heat stress response, corals exposed to reduced salinity experience
a complete collapse of their internal cellular protein balance, suggesting that
their cells are in deep trouble.”
the central Great Barrier Reef may have been spared mass thermal bleaching due
to higher-than-normal ocean temperatures this summer, there are many coastal
reefs left battling dramatic changes in water conditions from the massive
plumes of floodwater.
frequency and severity of heavy rainfall and runoff events predicted to
increase by 2050, management interventions to increase the resilience of reefs
are needed now more than ever.
Paper: Aguilar C, Raina J-B, Fôret S, Hayward DC, Lapeyre B, Bourne DG, Miller DJ (2019). Transcriptomic analysis reveals protein homeostasis breakdown in the coral Acropora millepora during hypo-saline stress. BMC Genomics 20:148
Images are available here.
Prof David Miller, ARC Centre of Excellence for Coral Reef Studies at James Cook University
Raina, UTS – Climate Change Cluster
ARC Centre of
Excellence for Coral Reef Studies
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