Marine Heatwaves Spell Trouble For Tropical Reef Fish — Even Before Corals Die

Marine Heatwaves Spell Trouble For Tropical Reef Fish — Even Before Corals Die A school of convict tang (Acanthurus triostegus) swim on Kiritimati’s dead reefs after the 2015–16 marine heatwave. (Kevin Bruce), Author provided

Despite the many challenges facing the world’s oceans today, coral reefs remain strongholds of marine biodiversity. Thousands of species of fish of all shapes and sizes call these colourful, complex and economically important ecosystems home. Impending ocean warming, however, spells trouble for these fishes.

Ever since the first global coral bleaching event devastated reefs in the late 1990s, scientists have worked to document the effects of these catastrophic phenomena on coral reef fishes. In the wake of severe bleaching, coral mortality often leads to changes in the community of fish that live on the reef: fish that feed on corals decline, while those that feed on algae increase as the latter proliferates.

But what happens to fish during a severe heat stress event — that is, when water temperatures rise, but the corals have not yet bleached and died? It seems that very few scientists have tried to find out.

Our new study, published in Ecological Applications, surveyed reef fish communities before, during and after the 2015–16 El Niño on Kiritimati, a coral atoll in the Pacific Ocean, that is part of the country of Kiribati. Our research suggests that short-term increases in water temperature may have devastating impacts on reef fish populations and the local communities that rely on them.

Heating up the world’s largest atoll

Kiritimati, or Christmas Island, is the world’s largest coral atoll — ring-shaped reef — by land mass. The nearest major airport is more than 2,000 kilometres away, in Hawaii. The people who live on Kiritimati are highly dependent on reef fish as a source of both food and income.

Marine Heatwaves Spell Trouble For Tropical Reef Fish — Even Before Corals Die A healthy coral reef on Kiritimati, prior to the El Niño in 2015–16. (Kristina Tietjen), Author provided

While the 2015–16 El Niño wreaked havoc on reefs worldwide, its effects were especially catastrophic around Kiritimati. Unprecedented levels of heat stress persisting for 10 straight months led to over 80 per cent coral mortality around the island, but not before triggering a change in the local fish community.

Stressed-out reef fish

After just two months of heat stress, reef fish populations around the atoll had plummeted by half. The number of fish species also declined, with some species disappearing entirely. Five species, including the Chevron butterflyfish, which feeds exclusively on live coral, have not been seen since.

One year after the heatwave, however, we found — somewhat surprisingly — that total reef fish biomass and abundance had recovered, rebounding to levels similar to those we’d observed in years prior to the heatwave. This begs the question: What exactly happened during those long, heat-stricken months?

Marine Heatwaves Spell Trouble For Tropical Reef Fish — Even Before Corals Die The pufferfish Arothron meleagris, one of the many reef fish species on Kiritimati that declined during the heatwave. (Sean Dimoff), Author provided

While severe heat stress can lead to decreased fitness and even mortality in reef fishes, we believe that most of the missing fish sought shelter on the deeper, cooler reefs around the island during the heatwave. Once the heat had subsided, they could have easily returned to the shallows.

Yet the recovery of the reef fish community was not the same across the board. Sites on the atoll nearest to the villages, where the reefs have been heavily affected by dredging, fishing and pollution, had impaired recovery relative to areas of the atoll far from villages where the reefs were nearly pristine prior to the heatwave.

This suggests that local environmental protection could help make reefs more resilient to the ravages of severe ocean warming. While it may not be enough to entice fish to stay put during a severe warming event, high-quality reefs may be more attractive to these fish upon their return.

A window into the future

If the reef fish return once the heat stress is over, is their disappearance in the short-term really a big deal? Considering that the survival of millions of people worldwide depends on tropical reef fishes, we believe the answer to this question is a resounding yes.

Marine Heatwaves Spell Trouble For Tropical Reef Fish — Even Before Corals Die A healthy coral reef on Kiritimati, prior to the heatwave. (Kieran Cox), Author provided

The impacts of climate change on coral reefs are only predicted to worsen in the coming decades. Studying the effects of severe heat stress in the present can serve as a window into the future, foreshadowing the consequences of gradual ocean warming and more frequent and severe marine heatwaves that are predicted to occur.

By understanding how fish populations react to elevated water temperatures, we can also attempt to predict and mitigate the effects of ocean warming on highly reef-dependent communities such as those on Kiritimati.

Within the realm of coral reef research, most studies on heat stress to date have focused on the link between heat stress and coral bleaching, and the knock-on effects of catastrophic bleaching on reef fishes. However, corals are not the only animals affected by the heat stress itself. Unless we intervene to limit climate change globally, we may risk losing not only corals but critically important reef fishes as well.The Conversation

About The Author

Jennifer M.T. Magel, Research Assistant, Biology, University of Victoria and Julia K. Baum, Professor of Biology, University of Victoria

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Related Books

Life After Carbon: The Next Global Transformation of Cities

by Peter Plastrik , John Cleveland
1610918495The future of our cities is not what it used to be. The modern-city model that took hold globally in the twentieth century has outlived its usefulness. It cannot solve the problems it helped to create—especially global warming. Fortunately, a new model for urban development is emerging in cities to aggressively tackle the realities of climate change. It transforms the way cities design and use physical space, generate economic wealth, consume and dispose of resources, exploit and sustain the natural ecosystems, and prepare for the future. Available On Amazon

The Sixth Extinction: An Unnatural History

by Elizabeth Kolbert
1250062187Over the last half-billion years, there have been Five mass extinctions, when the diversity of life on earth suddenly and dramatically contracted. Scientists around the world are currently monitoring the sixth extinction, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. This time around, the cataclysm is us. In prose that is at once frank, entertaining, and deeply informed, New Yorker writer Elizabeth Kolbert tells us why and how human beings have altered life on the planet in a way no species has before. Interweaving research in half a dozen disciplines, descriptions of the fascinating species that have already been lost, and the history of extinction as a concept, Kolbert provides a moving and comprehensive account of the disappearances occurring before our very eyes. She shows that the sixth extinction is likely to be mankind's most lasting legacy, compelling us to rethink the fundamental question of what it means to be human. Available On Amazon

Climate Wars: The Fight for Survival as the World Overheats

by Gwynne Dyer
1851687181Waves of climate refugees. Dozens of failed states. All-out war. From one of the world’s great geopolitical analysts comes a terrifying glimpse of the strategic realities of the near future, when climate change drives the world’s powers towards the cut-throat politics of survival. Prescient and unflinching, Climate Wars will be one of the most important books of the coming years. Read it and find out what we’re heading for. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook-icontwitter-iconrss-icon

 Get The Latest By Email

{emailcloak=off}

LATEST VIDEOS

Methane Emissions Hit Record Breaking Levels
Methane Emissions Hit Record Breaking Levels
by Josie Garthwaite
Global emissions of methane have reached the highest levels on record, research shows.
kelp forrest 7 12
How The Forests Of The World’s Oceans Contribute To Alleviating The Climate Crisis
by Emma Bryce
Researchers are looking to kelp for help storing carbon dioxide far beneath the surface of the sea.
Tiny Plankton Drive Processes In The Ocean That Capture Twice As Much Carbon As Scientists Thought
Tiny Plankton Drive Processes In The Ocean That Capture Twice As Much Carbon As Scientists Thought
by Ken Buesseler
The ocean plays a major role in the global carbon cycle. The driving force comes from tiny plankton that produce…
Climate Change Threatens Drinking Water Quality Across The Great Lakes
Climate Change Threatens Drinking Water Quality Across The Great Lakes
by Gabriel Filippelli and Joseph D. Ortiz
“Do Not Drink/Do Not Boil” is not what anyone wants to hear about their city’s tap water. But the combined effects of…
Talking About Energy Change Could Break The Climate impasse
Talking About Energy Change Could Break The Climate Impasse
by InnerSelf Staff
Everyone has energy stories, whether they’re about a relative working on an oil rig, a parent teaching a child to turn…
Crops Could Face Double Trouble From Insects And A Warming Climate
Crops Could Face Double Trouble From Insects And A Warming Climate
by Gregg Howe and Nathan Havko
For millennia, insects and the plants they feed on have been engaged in a co-evolutionary battle: to eat or not be…
To Reach Zero Emissions Government Must Address Hurdles Putting People Off Electric Cars
To Reach Zero Emissions Government Must Address Hurdles Putting People Off Electric Cars
by Swapnesh Masrani
Ambitious targets have been set by the UK and Scottish governments to become net-zero carbon economies by 2050 and 2045…
Spring Is Arriving Earlier Across The US, And That's Not Always Good News
Spring Is Arriving Earlier Across The US, And That's Not Always Good News
by Theresa Crimmins
Across much of the United States, a warming climate has advanced the arrival of spring. This year is no exception.

LATEST ARTICLES

Two-thirds Of Glacier Ice In The Himalayas Could Be Lost By 2100
Two-thirds Of Glacier Ice In The Himalayas Could Be Lost By 2100
by Ann Rowan
In the world of glaciology, the year 2007 would go down in history. It was the year a seemingly small error in a major…
Rising Temps Could Kill Millions A Year By Century’s End
Rising Temps Could Kill Millions A Year By Century’s End
by Edward Lempinen
By the end of this century, tens of millions of people could die each year worldwide as a result of temperatures rising…
New Zealand Wants To Build A 100% Renewable Electricity Grid, But Massive Infrastructure Is Not The Best Option
New Zealand Wants To Build A 100% Renewable Electricity Grid, But Massive Infrastructure Is Not The Best Option
by Janet Stephenson
A proposed multibillion-dollar project to build a pumped hydro storage plant could make New Zealand’s electricity grid…
Wind Farms Built On Carbon-rich Peat Bogs Lose Their Ability To Fight Climate Change
Wind Farms Built On Carbon-rich Peat Bogs Lose Their Ability To Fight Climate Change
by Guaduneth Chico et al
Wind power in the UK now accounts for nearly 30% of all electricity production. Land-based wind turbines now produce…
Climate Denial Hasn't Gone Away – Here's How To Spot Arguments For Delaying Climate Action
Climate Denial Hasn't Gone Away – Here's How To Spot Arguments For Delaying Climate Action
by Stuart Capstick
In new research, we have identified what we call 12 “discourses of delay”. These are ways of speaking and writing about…
Routine Gas Flaring Is Wasteful, Polluting And Undermeasured
Routine Gas Flaring Is Wasteful, Polluting And Undermeasured
by Gunnar W. Schade
If you’ve driven through an area where companies extract oil and gas from shale formations, you’ve probably seen flames…
Flight Shaming: How To Spread The Campaign That Made Swedes Give Up Flying For Good
Flight Shaming: How To Spread The Campaign That Made Swedes Give Up Flying For Good
by Avit K Bhowmik
Europe’s major airlines are likely to see their turnover drop by 50% in 2020 as a result of the COVID-19 pandemic,…
Will The Climate Warm As Much As Feared By Some?
Will The Climate Warm As Much As Feared By Some?
by Steven Sherwood et al
We know the climate changes as greenhouse gas concentrations rise, but the exact amount of expected warming remains…