If you’ve ever dived on a coral reef, you may have peeked into a staghorn coral and seen small fish whizzing through its branches. But few realise that these small fish, such as tiny goby fish, play a crucial role in helping corals weather the storm of climate change.
But alarmingly, our new research found gobies decline far more than corals do after multiple cyclones and heatwaves. This is concerning because such small fish — less than 5 centimetres in length — are critical to coral and reef health.
Unfortunately, the number of cyclones and heatwaves is on the rise. These disasters have begun to occur back-to-back, leaving no time for marine life to recover.
With the recent push by UNESCO to list the Great Barrier Reef as “in danger”, the world is currently on edge about the status of coral reefs. We’re at a critical stage to take all the necessary measures to save coral reefs worldwide, and we must broaden our focus to understand how the important relationships between corals and fish are affected.
Goby fish: the snack-sized friends of coral
In all environments, organisms can form relationships where they work together to improve each other’s health. This is called a mutual symbiosis, like a you-scratch-my-back principle.
Gobies that live in corals are small, snack-sized fish that rarely venture beyond the prickly borders of their protective coral homes. The Great Barrier Reef is home to more than 20 species of coral gobies, which live in more than 30 species of staghorn corals.
Even if their corals become stressed and bleached, they remain steadfast within the coral, helping it to survive. Without their full-time cleaning staff, corals would be more susceptible when threatened with climate change.
Unfortunately, just like Nemos (clownfish) living inside anemones, climate change threatens the mutual symbioses between gobies and corals.
Coral gobies in decline
While SCUBA diving, we surveyed corals and their goby friends over a four-year period (2014-17) of near-continuous devastation at Lizard Island, on the Great Barrier Reef. Over this time, two category 4 cyclones and two prolonged heatwaves wreaked havoc on this world-renowned reef.
What we saw was alarming. After the two cyclones, the 13 goby species (genus Gobiodon) and 28 coral species (genus Acropora) we surveyed declined substantially.
But after the two heatwaves, gobies suddenly fared even worse than corals. While some coral species persisted better than others, 78% no longer housed gobies.
Importantly, every single goby species either declined, or worse, completely disappeared. The few gobies we found were living alone, which is especially concerning because gobies breed in monogamous pairs, much like most humans do.
Warmer water is even changing reef fish on a genetic level. Fish are struggling to reproduce, to recognise what is essential habitat, and to detect predators. Research has shown clownfish, for example, could not tell predatory fish (rockcods and dottybacks) from non-predators (surgeonfishes and rabbitfishes) when exposed to more acidic seawater.
The bigger picture looks bleak. Corals are likely to become increasingly vulnerable if their symbiotic gobies and other inhabitants continue to decline. This could lead to further disruptions in the reef ecosystem because mutual symbioses are important for ecosystem stability.
We need to broaden our focus to understand how animal interactions like these are being affected in these trying times. This is an emerging field of study that needs more research in the face of climate change.
The federal government is considering changes to Australia’s marine reserves to implement a national system. This week The Conversation is looking at the science behind marine reserves and how to protect our oceans.
Off Australia’s northeastern coastline, extending eastwards from the outer edge of the Great Barrier Reef, is a vast extent of ocean known as the Coral Sea.
Almost a million square kilometres of the Coral Sea is within Australian waters, making up one of six regions used for planning national networks of marine reserves. Unlike the other regions, virtually all of the Coral Sea is within a single reserve.
On the face of it, this should encourage people who are concerned with conservation of marine biodiversity. But, as often happens, the devil is in the detail.
The effectiveness of the reserve hinges on its internal zones – subdivisions that vary in the uses and activities they allow. So “protected” is a slippery concept. Just how protected the Coral Sea is depends on where and how large the different zones are.
The review of Commonwealth marine reserves, released earlier this month, recommended changes to the zoning arrangements put in place when the network was declared in 2012, but not for the better.
A world-class sea
The Coral Sea is almost entirely open ocean, reaching depths of more than 4,000m. Scattered through this expanse of deep blue are important patches of coral and rock: cays and islets, 30 atoll systems with shallow-water and low-light coral reefs, and seamounts and pinnacles supporting deep-sea, cold-water ecosystems.
The global significance of the Coral Sea for marine biodiversity – including corals, fish, turtles, seabirds, and whales – has been reviewed recently, but new discoveries continue.
The southern Coral Sea is also a global hotspot for predators. The protection of large predatory species such as sharks and marlin is particularly important, given their key roles in open ocean ecosystems and the massive worldwide decline of these animals at the hands of industrialised fishing.
The Coral Sea’s remoteness does not make it immune from human impacts. Some fishing methods alter the structure and composition of seabed ecosystems. Globally and in eastern Australia, pelagic long-lining takes a large toll in bycatch (non-target fish that are discarded, often dead, including shark species listed as vulnerable).
Many reefs in the Coral Sea are open to line fishing, which is known to deplete target populations and adversely affect corals in the neighbouring Great Barrier Reef.
The 2016 coral bleaching event that affected 93% of the Great Barrier Reef also caused significant death on reefs in the northern and central Coral Sea.
The importance and vulnerability of the Coral Sea call for well-planned protection. That protection should also be precautionary – where impacts are unknown or uncertain we should increase protection, or at least not put marine ecosystems at risk. This is one of the explicit principles of marine planning in Australia.
Commercial and recreational fishing present ecological risks that need to be managed carefully. Precaution is also called for because most parts of the Coral Sea, even those in relatively shallow water, are still largely unexplored, with the discovery of new species likely.
The Coral Sea reserve
In November 2012, the Labor federal government announced massive increases to Australia’s marine reserves, including large additions to existing smaller reserves in the Coral Sea. The zoning of the Coral Sea Marine Reserve that resulted was typical of the larger picture.
Zones that prohibited fishing (“no-take” zones, shown in green in the left-hand map below) were mostly far offshore in very deep waters where little or no fishing occurred.
Zones that protected the marine environment from open ocean long-lining were placed in areas where little or no long-lining occurred. Most reefs, cays and seamounts remained open to fishing. So did the world’s only known black marlin spawning aggregation.
Overall, the no-take zones were strongly “residual” – placed in areas left over from commercial and recreational uses, and least in need of protection – rather than designed to mitigate known threats.
The approach could be described as “business as usual”, with priority given to existing uses and conservation coming a poor second.
Just over a year after they were established, the new reserves were “re-proclaimed” by the Coalition government, effectively rendering them empty outlines on the map. The strength of the pushback against the reserves was perplexing, given that they were obviously designed to have minimal effect on fishing and no effect on extraction of oil and gas.
Before the release of the review, a cynic might have predicted, given statements when the review began, that the process was intended to convert a largely residual reserve system into a completely residual one. As it happens, that is close to what has been recommended for the Coral Sea.
A major feature of the recommended zoning is a reduction of no-take by more than 93,000km², or 9.3% of the Coral Sea Marine Reserve (no-take zones, or national park, now cover 40% of the reserve). No-take zoning is now even more strongly concentrated in remote, deep water where it will make even less difference to fishing than before.
The panel recommended new no-take zones in areas next to those in the central and southern Great Barrier Reef Marine Park, but large parts of the same region in the Coral Sea are proposed to be reopened to demersal trawling.
Some reefs have less protection than before, and some have more. Notably, two of the most important reefs in the Coral Sea – Osprey and Marion – are partly open to fishing and partly no-take. Split zones are known to pose problems for compliance and are typically avoided in conservation planning. Fishing on Osprey could also compromise its value as a globally significant dive destination, specifically for its sharks and pelagic fish.
There are net increases in areas open to gear types known to pose ecological risks: sea floor longlines (2,400km² of the reserve, including the Fraser Seamount), sea floor trawl (26,300km²), and open sea long-lining (269,000km²). These changes appear inconsistent with advice on ecological risks.
When evidence was limiting, it appears that the Expert Scientific Panel placed the burden of proof on the environment, not on commercial and recreational users.
Protecting the Coral Sea from what?
Protected areas are meant to protect biodiversity from threats to its survival. Why bother saying that?
Because the 2012 marine reserves made almost no difference to activities threatening marine biodiversity. There is a key difference between protection, which stops threats from affecting species and ecosystems, and re-badging large tracts of ocean in ways that make no difference.
At least for the Coral Sea, the proposed new zones involve further re-badging but less overall protection. A similar mentality appears to underlie both the 2012 and recommended zonings: marine protected areas are good things to have, providing they don’t get in the way of socioeconomic interests.
While the new zones largely failed to protect the Coral Sea’s biodiversity, the review’s Expert Scientific Panel favourably assessed the “performance” of the Coral Sea Marine Reserve in ways that are simply uninformative and distracting.
For instance, one of the measures used by the review is the number of conservation features (such as seafloor types) in reserves. This measure is misleading in three ways: many of the represented features don’t need protection, others are affected to varying, but unstated, degrees by fishing, and we don’t know how much of each feature needs protection.
At the core of systematic conservation planning, which is widely accepted as the most effective way of designing reserve systems, are quantitative objectives for features, preferably reflecting ecosystem structure and function, scaled to reflect levels of threat. But these objectives were notably absent from the assessment of performance of the Coral Sea Marine Reserve, and from the review process that recommended the new zones.
How to do things better
Better planning for the Coral Sea would move beyond the qualitative goals and principles advocated by the Expert Scientific Panel, which can be readily interpreted to favour economic considerations over conservation.
Because of the global significance of the Coral Sea and uncertainty around the actual risks posed by fishing, effective planning would be truly precautionary, prioritising the persistence of biodiversity where there is doubt. It would also engage with managers and governments in adjacent marine regions to limit cross-boundary threats.
The amount of protection needed for species and other conservation features, including types of open sea and other significant habitats, would be identified quantitatively by experts on marine biodiversity, considering distinctiveness, threats, and reliance on Australian waters for their persistence.
Those conservation objectives would be achieved by a mix of zones that varied levels of protection from place to place and perhaps seasonally to limit the adverse effects of fishing and other extractive activities. The relative contributions of those zones to each objective would be assessed and put into the mix.
Such an explicit approach was a major reason for the lasting, worldwide recognition of the Great Barrier Reef rezoning in 2004, but has been avoided elsewhere in Commonwealth waters to maximise flexibility for extractive interests.
And finally, effective planning would acknowledge that no-take zones in areas with no fishing make no contribution to conservation.
*Update: this article has been updated to clarify the use of conservation features in measuring reserve performance
With the many threats currently impacting on the Great Barrier Reef and the growing intensity of those threats into the future, just what does the future look like for the reef? The link below is to an article that looks into that question and the answer may not be a good one.
The link below is to an article on a massive new marine park established in the Coral Sea. This marine park is just one of a number of new protected areas that now give Australia the most comprehensive network of marine reserves in the world.
The following link is to an article reporting on calls for an expansion to the planned marine park in the Coral Sea. The planned marine park will protect an area of almost 1 million square kilometres, making it the world’s largest protected marine area.