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Marine reserves saved coral reefs from Queensland floods

Marine reserves are a hot topic in Australia, with federal and state governments debating whether to allow recreational fishers to take fish from within their boundaries. But new research demonstrates…

Floodwater plumes, like this one in Moreton Bay, do less damage to reefs that are in marine reserves. Healthy Waterways/supplied

Marine reserves are a hot topic in Australia, with federal and state governments debating whether to allow recreational fishers to take fish from within their boundaries. But new research demonstrates that reserves can have a real benefit for marine ecosystems — by protecting coral reefs from floods.

We enjoy fishing; but we also appreciate that marine reserves have many positives. Yes, they restrict fishing in certain areas, but they have been shown to increase the numbers of catchable fish outside reserves.

Our study shows that reserves can also improve the resilience of the habitats that fish rely on. Without them, there would be fewer fish for everyone.

Reefs better off in reserves

Our research, published today in Global Change Biology, investigates how coral reefs respond to disturbance. In 2011 Queensland was struck by catastrophic flooding, which which resulted in three-quarters of Queensland being declared a flood disaster zone – an area as big as France, Germany and Italy combined.

While the disaster on land is well documented, we wondered what happened out to sea. We looked at coral reefs in Moreton Bay near the mouth of the Brisbane River, which drains into the bay.

Ten coral reefs were surveyed by a team of divers before the flood, immediately after the flood had passed, and again one year later. Four reefs were inside marine reserves and six reefs were open to fishing.

We found that reefs in marine reserves, where no fishing is allowed, were better able to cope with flood impacts compared to reefs where fishing is allowed.

How floods affect reefs

The shift in catchment land-use from predominantly forested to agricultural and urban means that floods dump lots of sediment into coastal waters. This smothers inshore coral reefs and fuels the rapid growth of algae. Algae compete with coral for space and can overgrow and harm coral when nutrients are in plentiful supply (as is the case after floods).

On healthy coral reefs the growth of algae is kept under control by herbivorous fish (i.e. fish that eat plants) such as rabbitfish, parrotfish and surgeonfish.

The settlement of baby corals is also important and helps to maintain coral dominance. Both grazing by herbivorous fish and coral settlement are vital to sustaining the reef’s health.

Our Moreton Bay research shows that coral reefs inside marine reserves support more herbivorous fish, which are harvested by spear and net fishers outside reserves. Reserve reefs also experience greater herbivory and coral settlement than similar reefs that are open to fishing. This means that after the 2011 floods, algae was rapidly removed from reefs in marine reserves, but wasn’t controlled on similar fished reefs.

Rabbitfish are important herbivores on coral reefs in Moreton Bay Dr Andrew Olds

Do reserves protect other ecosystems from disturbance?

So we know reserves can help protect reefs from floods — could the same apply to other ecosystems?

To withstand disturbances (such as floods), reserves need to promote processes that enable ecosystems to function. In the case of reefs in Moreton Bay, this is herbivory and coral settlement.

Other studies have shown that reserves can have benefits for ecological processes (like herbivory and predation) in kelp forests, seagrass meadows and forests. But we don’t yet know if this will translate into greater capacity to recover from disturbances.

Ultimately, protecting marine ecosystems from disturbance depends on how reserves are designed, why they’re created, and how they are managed. Recent research led by the University of Tasmania showed that by-and-large, marine reserves aren’t doing the job of protecting marine life, but well-designed and managed reserves can have eight times the number of large fish.

Reserves could lead in fight against climate change

The main purpose of conservation strategies such as marine reserves is to maintain and enhance biodiversity. But there is now also great interest in using reserves to improve the resilience of degraded ecosystems.

Our research adds weight to the idea that reserves can promote ecosystem health, at least in coastal waters. Our study also suggests marine reserves can play a key role in protecting coastal ecosystems from future disturbance, and particularly some of the effects of climate change. The capacity of marine reserves to protect coral reefs from floods will likely be important in the future, given that the frequency and severity of extreme weather events are projected to increase.

Our findings provide strong evidence that well designed and managed marine reserves can deliver sound benefits for ecosystems – many of which take time to become apparent.

The ecosystem benefits of marine reserves stem from the key roles that fish play in coastal habitats. For example, herbivorous fish on coral reefs remove algae and promote coral health, but can also be harvested heavily by spear and net fishers.

Re-opening marine reserves to fishing can, therefore, have unintended consequences that extend beyond direct effects on fish and fishers, and may impact on the functioning of coastal ecosystems.

Dr Andrew Olds conducted this study at Griffith University and has since moved to the University of the Sunshine Coast.

Join the conversation

14 Comments sorted by

  1. David Arthur

    resistance gnome

    Thanks for this article, and thank you for the important work on which it is based.

    At present, the Senate Environment and Communications References Committee is conducting an inquiry into "The adequacy of the Australian and Queensland Governments’ efforts to stop the rapid decline of the Great Barrier Reef ..." for which the Committee is accepting public submissions until 2 June 2014.

    I think the Committee's Inquiry would be greatly aided by a submission based on the work you describe here. For more information, see

    1. Wade Macdonald


      In reply to David Arthur

      David, have you ever considered the fact that the reefs closed to all forms of fishing have disproportionately effected reefs still open to all forms of fishing? In effect the zones themselves have detrimentally impacted one reef in the hope of saving another reef.

      I would like to think that scientists could use methods of management that better distinguish between fishing methods and effects rather than advocate blanket bans on sustainable fishing methods like trolling surface lures for pelagics which would have little to no impact on what is being advocated in this article.

    2. David Arthur

      resistance gnome

      In reply to Wade Macdonald

      The effects on adjacent reefs, Wade, is that they are more resilient, better able to recover because fish are constantly leaving the nursery "no-take" reefs for opportunities elsewhere.

      The benefits of "no-take" zones for other reefs was realised fairly soon after their inception, as described by McCook et al, "Adaptive management of the Great Barrier Reef: A globally significant demonstration of the benefits of networks of marine reserves" (2010)

    3. Wade Macdonald


      In reply to David Arthur

      Spillover doesn't always transpire as evidenced by Edgars recent reports so spare me the generalisations.

      Mc Cook et al....a report brought into question, and subject to an investigation from my knowledge for many reasons because of its claims. Its a poor example David.

      I am fully aware of the benefits of marine parks but they are a blunt tool being used to ban all forms of fishing before utilising smarter, fairer and socially acceptable management regimes against fishing while at the same time wasting money that should be spent addressing our land use and other ingressive detriments.

      Great for anti fishing antagonists who want rec anglers to wake up every day wondering when the next area of ocean will be removed from under their boat hull.

      Sound management before exclusion of sustainable activities please.

    4. David Arthur

      resistance gnome

      In reply to Wade Macdonald

      "Mc Cook et al....a report brought into question" questioned by whom, Mr McDonald? Libertarian fisherfolk who might resent any restriction whatsoever?

      While there may be queries and doubts around the veracity of published research, Mr McDonald, until those queries and doubts find their way into the published peer-reviewed literature, I'm not sure that we can credibly alter policy.

      I'm not arguing that present marine sanctuaries are panaceae - but bear in mind that what's optimal for recreational anglers may not always be optimal for coral - and hence for coastal protection ("Coral Reefs Protect Coastlines",

    5. David Arthur

      resistance gnome

      In reply to David Arthur ?

      Wally Starck ? WTF? He's the bloke who reckons Australian fisheries are underutilised because they're not fished as intensively as Indonesian fisheries. Err, like there are no Indonesian fishing boats in Australian waters because they can't get enough fish at home are there?

      Sorry, but Dear Old Wally is big in the Australian Environment Foundation, an astroturfing mob as credible as Nigel Lawson's Global Warming Policy Foundation.

      ie you're trying to feed us crap.

    6. Wade Macdonald


      In reply to David Arthur

      An increasing gw yes but not the catastrophe you and others espouse through modelling. The feedbacks have mitigated that despite your dodgy climate and marine park references. Wally's postion and claims has merit in this instance if not always.

    7. David Arthur

      resistance gnome

      In reply to Wade Macdonald

      "An increasing gw yes but not the catastrophe you and others espouse through modelling."

      Err, no need to resort to modelling. A simple comparison of modern atmospheric CO2 with early-mid Pliocene (5-4 Mya) tells us we're on course for a ~10 m sea level rise over the next millennium or so.

      My view is that Wally's position is ill-founded, and lacks objective merit - but I daresay his words fall on sympathetic ears in some circles.

  2. Wade Macdonald


    These herbivores may be affected by netting processes but fishing is diverse in method, selectivity and recreational line fishermen could be managed without bans and still protect these species biomass through release etc if caught as bycatch accidentally. This would In turn maintain stated reef resilience and allow access.

    I would like a response as to why disturbance solely focuses on eliminating all forms of fishing but is void of the impacts of diving, snorkelling, boating, international…

    Read more
  3. Wade Macdonald


    Ever considered addressing the human induced pollutants in floodwaters or is every natural reef and blade of seagrass only safe with management regimes that use 'all forms' of fishing as a sop and promote other human activities instead?

  4. Mike Jubow

    Forestry nurseryman at Nunyara Wholesale , Forestry consultants, seedling suppliers.

    A good little bit of news at 11AM today 23th May14, where the Deutcher Bank has decided Not to fund the Abbott Pt expansion because of the likely hood of damage to the GBR.

    Media release-----------

    "Deutsche “will not be involved” in Reef port expansion

    Deutsche Bank has backed away from Indian company Adani’s Abbot Point coal port expansion, after an international campaign focussed intense pressure ahead of the bank’s AGM.

    At the AGM, Deutsche Bank Co-Chair Juergen Fitschen…

    Read more
  5. Bruce WILDCARD Davey

    4th generation Professional Fisherman at WILDCARD WILDCAUGHT Pty Ltd


    There is always 3 sides to the truth.
    1. Your side.
    2. My side.
    3. Somewhere in the middle is the truth.

    As Wade suggests; Simply locking fishers out of large ocean tracts in the name of protection is not good preservation and fails the most basic cost/ benefit analysis.