Life on the hidden doughnuts of the Great Barrier Reef is also threatened by climate change



A sea cucumber living on the Great Barrier Reef inter-reef seafloor.
Kent Holmes/Nature Ecology and Evolution, Author provided

Mardi McNeil, Queensland University of Technology; Andrew Hoey, James Cook University; Jody Webster, University of Sydney, and Luke Nothdurft, Queensland University of Technology

Mention the Great Barrier Reef, and most people think of the rich beauty and colour of corals, fish and other sea life that are increasingly threatened by climate change.

But there is another part of the Great Barrier Reef that until recently was largely hidden and under-explored.

In the northern section of the Great Barrier Reef Marine Park there are large Halimeda algal habitats called bioherms (also known as doughnuts because of their shape).

They are constructed by a type of algae (Halimeda) with a limestone skeleton. The tops of the bioherms are carpeted by a living meadow of the algae, yet much of the plant community includes other types of green, red and brown algae and some seagrasses.

A type of green seaweed.
Halimeda is a genus of green macroalgae (seaweed).
Mardi McNeil, Author provided

The bioherms cover an area greater than 6,000km², more than twice the area of shallow coral reefs.

Several maps showing the location of the _Halimeda_ bioherms.
The distribution of Halimeda bioherms in the Great Barrier Reef.
Figshare/Mardi McNeil, CC BY

Scientists have known for decades of this unusual inter-reef seafloor habitat that lies between the coast and the outer barrier reefs. But they’ve never investigated the diversity of marine life that lives there, until now.

In a new study published today in Nature Ecology and Evolution, scientists examined the community of plants and animals that inhabit these unique areas.

Let’s go deeper

Most studies of tropical marine biodiversity come from shallow coastal and coral reef habitats. We know a great deal about the biodiversity of these parts of the Great Barrier Reef.

But beyond the vision of scuba divers, deeper inter-reef habitats on the shelf, such as the bioherms, have been largely under-explored.




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In our study, we used a dataset of all the plants and animals recorded from the bioherms and surrounding seafloor habitats. The data came from the Seabed Biodiversity Project, a large study published back in 2007 of the inter-reef biodiversity in the Great Barrier Reef World Heritage Area.

What we found was surprising. An exceptional diversity of marine life and a distinct community was found to be living on the bioherms.

A diverse community

The biodiversity of marine life was up to 76% higher on the bioherms than the surrounding inter-reef habitats. Species richness was especially high for plants and invertebrates.

The average number of fish species per site was about the same in both Halimeda and non-Halimeda habitats. In total, 265 species of fish were observed in the bioherms, including sharks and rays.

Overall, more than 1,200 species of animals were recorded from the bioherms. The majority of these (78%) are invertebrates.

A feather star invertebrate.
Most of the animals living on the Halimeda bioherms are invertebrates, such as this feather star.
Mardi McNeil, Author provided

A distinct community

The composition of plant and animal communities on the bioherms was also distinctly different to the surrounding inter-reef areas.

Some 40% of bioherm species were unique to that habitat in the study area. The community included many sponges, snails and slugs, crabs and shrimps, brittle stars, sea urchins and sea cucumbers.

The fish community on the bioherms was also distinct from surrounding habitats. The two-spot wrasse, threadfin emperor and black-banded damselfish were particularly common.

A small black fish with a yellow tail and a white band near its neck.
A yellowtail angelfish (Chaetodontoplus meredithi) seen in coral waters of the Great Barrier Reef.
Sascha Schultz/iNaturalist.org/FishofAustralia, CC BY-NC

Most interesting about the bioherm fish community was the occurrence of some species such as the yellowtail angelfish generally thought to live mostly on coral reefs. Some of these reef-associated fishes have been increasingly observed in a range of non-reef habitats.

These multi-habitat users may be using the bioherms for shelter, feeding, spawning or as nursery grounds. Understanding the connections between shallow coral reefs and deeper bioherms is important to better understand how the reef and inter-reef habitats function.

An unusual habitat

The Halimeda bioherms are arguably the weirdest habitat in the Great Barrier Reef.

Recent high-resolution seafloor mapping using airborne lasers revealed the bioherms form a seafloor that looks like fields of giant doughnuts 20 metres high and 200 metres across.

The doughnuts are the connected circles on the seafloor in the yellow/green bioherm part. They look quite small but each circle is about 200 metres across.

The tops of the bioherms lie some 25-30 metres below the surface, so can’t be seen from boats passing over.

Deeper water and the remote location has meant the bioherms have been mostly invisible to marine biologists that work on the nearby shallow coral reefs.

Under threat from climate change

We are only just beginning to understand the importance of Halimeda bioherms as a habitat to support biodiversity in the Great Barrier Reef.

But just as the rest of the Great Barrier Reef is likely to be impacted by the effects of climate change, so too are the bioherms.

Potential threats to the bioherms include marine heating, ocean acidification and changes to circulation patterns.




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It has been more than 15 years since the inter-reef Seabed Biodiversity Project. The five-yearly Great Barrier Reef Outlook Report says little is known about any ecological trends in the bioherm habitat.

Our new study provides a baseline of the biodiversity of Halimeda bioherms at a single point in time. But questions remain about the present state of this ecosystem and its resilience on short and long-term physical and biological cycles.

Long-term monitoring of these unique and hidden habitats is critical to more fully understand the overall health of the Great Barrier Reef.The Conversation

Mardi McNeil, Postdoctoral researcher, Queensland University of Technology; Andrew Hoey, Senior Research Fellow, James Cook University; Jody Webster, Professor of Marine Geoscience, University of Sydney, and Luke Nothdurft, Senior Lecturer – Earth Science, Queensland University of Technology

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

Water markets are not perfect, but vital to the future of the Murray-Darling Basin



kaman985shu/Shutterstock

Neal Hughes, Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES)

Water markets have come in for some bad press lately, fuelled in part by the severe drought of 2019 and resulting high water prices.

They have also been the subject of an Australian Competition and Consumer Commission inquiry, whose interim report released last year documented a range of problems with the way water markets work in the Murray-Darling Basin. The final report was handed to the treasurer last week.

While water markets are far from perfect, new research from the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES) has found they are vital in helping the region cope with drought and climate change, producing benefits in the order of A$117 million per year.

To make the most of water markets, we will need to keep improving the rules and systems which support them. But with few “off-the-shelf” solutions, further reform will require both perseverance and innovation.

Water markets generate big benefits

Australia’s biggest and most active water markets are in the southern Murray-Darling Basin, which covers the Murray River and its tributaries in Victoria, NSW and South Australia.

Murray Darling Basin.
MDBA

Each year water right holders are assigned “allocations”: shares of water in the rivers’ major dams. These allocations can be traded across the river system, helping to get water where it is most needed.

Water markets also allow for “carryover”: where rights holders store rather than use their allocations, holding them in dams for use in future droughts.

Our research estimates that water trading and carryover generate benefits to water users in the southern Murray-Darling, of A$117 million on average per year (around 12% of the value of water rights) with even larger gains in dry years. Carryover plays a key role, accounting for around half of these benefits.

Together water trading and carryover act to smooth variability in water prices, while also slightly lowering average prices across the basin.

There’s room for improvement

One of many issues raised in the Australian Competition and Consumer Commission interim report was the design of the trading rules, including limits on how much water can move between regions.

These rules are intended to reflect the physical limits of the river system, however getting them right is extremely difficult.

The rules we have are relatively blunt, such that there is potential at different times for either too much water to be traded or too little.

National Electricity Market.
AGL

One possible refinement is a shift from a rules-based system to one with more central coordination.

For example, in electricity, these problems are addressed via so-called “smart markets”: centralised computer systems which balance demand and supply across the grid in real-time.

Such an approach is unlikely to be feasible for water in the foreseeable future.

But a similar outcome could be achieved by establishing a central agency to determine inter-regional trade volumes, taking into account user demands, river constraints, seasonal conditions and environmental objectives.

While novel in Australia, the approach has parallels in the government-operated “drought water banks” that have emerged in some parts of the United States.

Some of the good ideas are our own

Another possible refinement involves water sharing rules, which specify how water allocations are determined and how they are carried over between years.

At present these rules are often complex and lacking in transparency. This can lead to a perceived disconnect between water allocations and physical water supply, creating uncertainty for users and undermining confidence in the market.

Although markets in the northern Murray-Darling Basin are generally less advanced than the south, some sophisticated water sharing systems have evolved in the north to deal with the region’s unique hydrology (highly variable river flows and small dams).

Beardmore Dam at St George in Southern Queensland, where water markets operate under a capacity sharing system.
ABARES

There is potential for the southern basin to make use of these northern innovations (known as “capacity sharing” or “continuous accounting”) to improve transparency and carryover decisions.

Don’t throw the market out with the river water

Governance failures in the water market have led to understandable frustration.

But it is important to remember how vital trading and carryover are in smoothing variations in water prices and making sure water gets where it is needed, especially during droughts.

The ACCC’s final report (due soon) will provide an opportunity to take stock and develop a roadmap for the future.


Water markets will be discussed at Today’s ABARES Outlook 2021 conference in an online panel session at 3-4pm AEDT.The Conversation

Neal Hughes, Senior Economist, Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES)

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

Birds on beaches are under attack from dogs, photographers and four-wheel drives. Here’s how you can help them


An adult fairy tern feeding a chick.
Claire Greenwell, Author provided

Claire Greenwell, Murdoch University

Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this new series, we’ve invited them to share their unique photos from the field.


Each year, oystercatchers, plovers and terns flock to beaches all over Australia’s coastline to lay eggs in a shallow scrape in the sand. They typically nest through spring and summer until the chicks are ready to take flight.

Spring and summer, however, are also when most people visit the beach. And human disturbances have increased breeding failure, contributing to the local contraction and decline of many beach-nesting bird populations.

Take Australian fairy terns (Sternula nereis nereis) in Western Australia, the primary focus of my research and photography, as an example. Their 2020-21 breeding season is coming to an end, and has been relatively poor.

Courting pair of Fairy Terns on the beach
Australian fairy tern pair. Males feed female mates, helping to supplement nutrients and energy for egg production.
Claire Greenwell

Fox predation and flooding from tidal inundation wiped out several colonies. Unfathomably, a colony was also lost after a four-wheel drive performed bog-laps in a sign-posted nesting area. Unleashed dogs chased incubating adults from their nests, and photographers entered restricted access sites and climbed fragile dunes to photograph nesting birds.

These human-related disturbances highlight the need for ongoing education. So let’s take a closer look at the issue, and how communities and individuals can make a big difference.

Nesting on the open beach

Beach-nesting birds typically breed, feed and rest in coastal habitats all year round. During the breeding season, which varies between species, they establish their nests above the high-water mark (high tide), just 20 to 30 millimetres deep in the sand.

Fairy Tern sitting on eggs
Eggs are sandy coloured and have a mottled appearance, which help them to blend in with the environment.
Claire Greenwell
Two Fairy Tern chicks. Down feathers are lightly coloured and mottled to help increase camouflage.
Fairy tern chicks crouch close to the ground to hide from predatory birds. Down feathers are lightly coloured and mottled to help increase camouflage.
Claire Greenwell

Some species, such as the fairy tern, incorporate beach shells, small stones and organic material like seaweed in and around the nest to help camouflage their eggs and chicks so predators, such as gulls and ravens, don’t detect them easily.

An adult Fairy Tern moving shell material around the nest site to increase camouflage of the eggs.
An adult fairy tern moving shell material around the nest site to increase the camouflage of its eggs.
Claire Greenwell

While nests are exposed and vulnerable on the open beach, it allows the birds to spot predators early and to remain close to productive foraging areas.

Still, beach-nesting birds live a harsh lifestyle. Breeding efforts are often characterised by low reproductive success and multiple nesting attempts may be undertaken each season.

Eggs and chicks remain vulnerable until chicks can fly. This takes around 43 days for fairy terns and about 63 days for hooded plovers (Thinornis rubricollis rubricollis).

Adult Fairy Tern feeding a chick
Eggs and chicks are vulnerable until chicks are capable of flight.
Claire Greenwell

Disturbances: one of their biggest threats

Many historically important sites are now so heavily disturbed they’re unable to support a successful breeding attempt. This includes the Leschenault Inlet in Bunbury, Western Australia, where fairy tern colonies regularly fail from disturbance and destruction by four-wheel drives.

Species like the eastern hooded plover and fairy tern have declined so much they’re now listed as “vulnerable” under national environment law. It lists human disturbance as a key threatening process.




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Birds see people and dogs as predators. When they approach, nesting adult birds distance themselves from the nest and chicks. For example, terns typically take flight, while plovers run ahead of the threat, “leading” it away from the area.

When eggs and chicks are left unattended, they’re vulnerable to predation by other birds, they can suffer thermal stress (overheating or cooling) or be trampled as their cryptic colouration makes them difficult to spot.

Silver Gull carrying away a Fairy Tern chick
Natural predators such as silver gulls readily take eggs and chicks when left unattended.
Claire Greenwell

Unlike plovers and oystercatchers, fairy terns nest in groups, or “colonies”, which may contain up to several hundred breeding pairs. Breeding in colonies has its advantages. For example, collective group defence behaviour can drive off predatory birds such as silver gulls (Chroicocephalus novaehollandiae).

However, this breeding strategy can also result in mass nesting failure. For example, in 2018, a cat visiting a colony at night in Mandurah, about 70 km south of Perth, killed six adults, at least 40 chicks and led to 220 adult birds abandoning the site. In other instances, entire colonies have been lost during storm surges.

Adult Fairy Terns mobbing a juvenile Crested Tern
Adult fairy terns engaged in group defence or ‘mobbing’ to drive away a juvenile crested tern from a colony.
Claire Greenwell

Small changes can make a big difference

Land and wildlife managers are becoming increasingly aware of fairy terns and the threats they face. Proactive and adaptive management combined with a good understanding of early breeding behaviour is helping to improve outcomes for these vulnerable birds.

Point Walter, in Bicton, WA, provides an excellent example of how recreational users and beach-nesting birds can coexist.

Point Walter, 18 km from Perth city, is a popular spot for picnicking, fishing, kite surfing, boating and kayaking. It’s also an important site for coastal birds, including three beach-nesting species: fairy terns, red-capped plovers and Australian pied oystercatchers (Haematopus longirostris).

Point Walter, Bicton with kite surfers and kayakers
Point Walter is a popular recreational site in Perth. Recent effective management, including seasonal closures, have enabled fairy terns, red-capped plovers and Australian pied oystercatchers to nest at the end of the sand bar.
Claire Greenwell

The end of the sand bar is fenced off seasonally, and as a result the past six years has seen the number of terns increase steadily. For the 2020-2021 season, the sand bar supported at least 150 pairs.

The closure also benefits the local population of red-capped plovers and Australian pied oystercatchers, who nest at the site each year.

Fairy Tern chick being brooded by its parent.
Fairy tern brooding (sitting on) its chick.
Claire Greenwell
An adult Australian Pied Oystercatcher teaching its offspring to hunt for prey.
An adult Australian pied oystercatcher teaching its offspring to hunt for prey.
Claire Greenwell

What’s more, strong community stewardship and management interventions by the City of Mandurah to protect a fairy tern colony meant this season saw the most successful breeding event in more than a decade — around 110 pairs at its peak.

Interventions included temporary fencing, signs, community education and increased ranger patrols. Several pairs of red-capped plovers also managed to raise chicks, adding to the success.

These examples highlight the potential for positive outcomes across their breeding range. But intervention during the early colony formation stage is critical. Temporary fencing, signage and community support are some of our most important tools to protect tern colonies.

So what can you do to protect beach-nesting birds?

Fairy Tern chick
A fairy tern chick at a site dedicated to fairy tern breeding.
Claire Greenwell
  • share the space and be respectful of signage and fencing. These temporary measures help protect birds and increase their chance of breeding success

  • keep dogs leashed and away from known feeding and breeding areas

  • avoid driving four-wheel drive vehicles on the beach, particularly at high tide

  • keep cats indoors or in a cat run (enclosure)

  • if you see a bird nesting on the beach, report it to local authorities and maintain your distance

  • avoid walking through flocks of birds or causing them to take flight. Disturbance burns energy, which could have implications for breeding and migration.




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The Conversation


Claire Greenwell, PhD Candidate, Murdoch University

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

Think all your plastic is being recycled? New research shows it can end up in the ocean


Shutterstock

Monique Retamal, University of Technology Sydney; Elsa Dominish, University of Technology Sydney; Nick Florin, University of Technology Sydney, and Rachael Wakefield-Rann, University of Technology Sydney

We all know it’s wrong to toss your rubbish into the ocean or another natural place. But it might surprise you to learn some plastic waste ends up in the environment, even when we thought it was being recycled.

Our study, published today, investigated how the global plastic waste trade contributes to marine pollution.

We found plastic waste most commonly leaks into the environment at the country to which it’s shipped. Plastics which are of low value to recyclers, such as lids and polystyrene foam containers, are most likely to end up polluting the environment.

The export of unsorted plastic waste from Australia is being phased out – and this will help address the problem. But there’s a long way to go before our plastic is recycled in a way that does not harm nature.

Man puts items in bins
Research shows plastic meant for recycling often ends up elsewhere.
Shutterstock

Know your plastics

Plastic waste collected for recycling is often sold for reprocessing in Asia. There, the plastics are sorted, washed, chopped, melted and turned into flakes or pellets. These can be sold to manufacturers to create new products.

The global recycled plastics market is dominated by two major plastic types:

  • polyethylene terephthalate (PET), which in 2017 comprised 55% of the recyclable plastics market. It’s used in beverage bottles and takeaway food containers and features a “1” on the packaging

  • high-density polyethylene (HDPE), which comprises about 33% of the recyclable plastics market. HDPE is used to create pipes and packaging such as milk and shampoo bottles, and is identified by a “2”.

The next two most commonly traded types of plastics, each with 4% of the market, are:

  • polypropylene or “5”, used in containers for yoghurt and spreads

  • low-density polyethylene known as “4”, used in clear plastic films on packaging.

The remaining plastic types comprise polyvinyl chloride (3), polystyrene (6), other mixed plastics (7), unmarked plastics and “composites”. Composite plastic packaging is made from several materials not easily separated, such as long-life milk containers with layers of foil, plastic and paper.

This final group of plastics is not generally sought after as a raw material in manufacturing, so has little value to recyclers.




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Symbols on PET plastic item
Items made from PET plastic resin are marked with a ‘1’.
Shutterstock

Shifting plastic tides

China banned the import of plastic waste in January 2018 to prevent the receipt of low-value plastics and to stimulate the domestic recycling industry.

Following the bans, the global plastic waste trade shifted towards Southeast Asian nations such as Vietnam, Thailand, Malaysia, and Indonesia. The largest exporters of waste plastics in 2019 were Europe, Japan and the US. Australia exported plastics primarily to Malaysia and Indonesia.

Australia’s waste export ban recently became law. From July this year, only plastics sorted into single resin types can be exported; mixed plastic bales cannot. From July next year, plastics must be sorted, cleaned and turned into flakes or pellets to be exported.

This may help address the problem of recyclables becoming marine pollution. But it will require a significant expansion of Australian plastic reprocessing capacity.

Map showing the import and export map of plastic waste globally.
Map showing the import and export map of plastic waste globally.
Authors provided

What we found

Our study was funded by the federal Department of Agriculture, Water and the Environment. It involved interviews with trade experts, consultants, academics, NGOs and recyclers (in Australia, India, Indonesia, Japan, Malaysia, Vietnam and Thailand) and an extensive review of existing research.

We found when it comes to the international plastic trade, plastics most often leak into the environment at the destination country, rather than at the country of origin or in transit. Low-value or “residual” plastics – those left over after more valuable plastic is recovered for recycling – are most likely to end up as pollution. So how does this happen?

In Southeast Asia, often only registered recyclers are allowed to import plastic waste. But due to high volumes, registered recyclers typically on-sell plastic bales to informal processors.

Interviewees said when plastic types were considered low value, informal processors frequently dumped them at uncontrolled landfills or into waterways. Sometimes the waste is burned.

Plastics stockpiled outdoors can be blown into the environment, including the ocean. Burning the plastic releases toxic smoke, causing harm to human health and the environment.

Interviewees also said when informal processing facilities wash plastics, small pieces end up in wastewater, which is discharged directly into waterways, and ultimately, the ocean.

However, interviewees from Southeast Asia said their own domestic waste management was a greater source of ocean pollution.

Birds fly over landfill site
Plastic waste meant for recycling can end up in overseas landfill, before it blows into the ocean.
Anupam Nath/AP

A market failure

The price of many recycled plastics has crashed in recent years due to oversupply, import restrictions and falling oil prices, (amplified by the COVID-19 pandemic). However clean bales of PET and HDPE are still in demand.

In Australia, material recovery facilities currently sort PET and HDPE into separate bales. But small contaminants of other materials (such as caps and plastic labels) remain, making it harder to recycle into high quality new products.

Before the price of many recycled plastics dropped, Australia baled and traded all other resin types together as “mixed plastics”. But the price for mixed plastics has fallen to zero and they’re now largely stockpiled or landfilled in Australia.

Several Australian facilities are, however, investing in technology to sort polypropylene so it can be recovered for recycling.

Shampoo bottles in supermarket
High-density polyethylene items such as shampoo bottles comprise a large share of the plastic waste market.
Shutterstock

Doing plastics differently

Exporting countries can help reduce the flow of plastics to the ocean by better managing trade practices. This might include:

  • improving collection and sorting in export countries

  • checking destination processing and monitoring

  • checking plastic shipments at export and import

  • improving accountability for shipments.

But this won’t be enough. The complexities involved in the global recycling trade mean we must rethink packaging design. That means using fewer low-value plastic and composites, or better yet, replacing single-use plastic packaging with reusable options.


The authors would like to acknowledge research contributions from Asia Pacific Waste Consultants (APWC) – Dr Amardeep Wander, Jack Whelan and Anne Prince, as well as Phil Manners at CIE.




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The Conversation


Monique Retamal, Research Principal, Institute for Sustainable Futures, University of Technology Sydney; Elsa Dominish, Senior Research Consultant, Institute for Sustainable Futures, University of Technology Sydney; Nick Florin, Research Director, Institute for Sustainable Futures, University of Technology Sydney, and Rachael Wakefield-Rann, Research Consultant, Institute for Sustainable Futures, University of Technology Sydney

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