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The Manta Rays of Queensland

Blog post by: Dr. Alena Pribyl
Blog post by:
Dr. Alena Pribyl

If you are a diver or snorkeler, you may have had the privilege to cross paths with the mysterious manta ray (Manta spp.). These large, graceful and harmless creatures are good at leaving one with a sense of awe and amazement as they glide silently through the water on their triangular pectoral fins, dwarfing most creatures in their path. Besides their large size and preference for being in the water column (as opposed to the ocean bottom), a good way to tell mantas from other rays is their distinctive forward fins or cephalic lobes. These are long flaps that flare into a tunnel when the manta is feeding; they help direct water into the manta’s mouth so it can filter its favorite food: zooplankton, shrimp and sometimes small fish.  When not feeding, mantas often roll these fins up, giving the appearance of horns.

Reef manta feeding. Photo credit: Project Manta
Reef manta feeding. Photo credit: Project Manta

Until recently, mantas that hang out near reefs and mantas in the open ocean were considered the same species, Manta birostris.  However, in 2009 it was discovered these were actually two species of manta ray1. There is the giant oceanic manta, M. birostris and the reef manta, M. alfredi.  The oceanic manta is larger than the reef manta, with a maximum wingspan of 7 m and weighing up to 2 tons. The reef manta, though not as large, still has a very respectable maximum wingspan of 5 m and can weigh up to 1.4 tons.1  Mantas are also very smart, boasting the largest brain to body ratio of any fish!  If you are lucky, one may decide to come over and check you out while diving.

Reef manta ray with cephalic fins rolled up. Photo credit: Project Manta
Reef manta ray with cephalic fins rolled up.
Photo credit: Project Manta

Both manta species can be found worldwide between 40ºN and 40ºS, although their populations appear highly fragmented and sparse2. They can live several decades but are slow to reproduce, producing only one pup (called a burrito) every two to three years2,3.  This means  that when populations are depleted, they will take a long time to rebuild. Right now the greatest threat to manta rays is from fishing.  They are targeted for their gill rakers and as food, or captured as bycatch3. As a result, the IUCN lists mantas as vulnerable on their Red List2,3.

Where to find mantas

In Australia, we are lucky to have both the oceanic and reef mantas occur in our waters, although the reef manta is the most commonly sighted. Populations of the reef manta extend from Perth in Western Australia around the north, and all the way to the Solitary Islands in New South Wales4. It is the reef manta we usually see on the reefs off of Queensland and New South Wales. They travel less than the oceanic mantas and can often be spotted at a favorite cleaning station. In case you haven’t seen one before, cleaning stations are usually rocks or coral bommies where small fish live that will eat the parasites, dead skin and bacteria off of larger marine animals. Some observers estimate mantas can spend between 2 to 8 hours a day at cleaning stations! And when a good cleaning station is found, word tends to get out, with some stations attracting large aggregations of mantas.

Manta cleaning station at Lady Elliot Island.

So when is the best time to see mantas? In Queensland and Northern New South Wales, the reef mantas have seasonal preferences. They hang out in the southern Great Barrier Reef near Lady Elliot Island year round, with their numbers peaking in the winter.  From mid-spring to mid-autumn many move south and are commonly seen off the SE Queensland coast, near North Stradbroke Island. And from late summer to mid-autumn they are also in Byron Bay.4 Increased food availability is likely one of the main drivers for their movements.5

Project Manta

Although reef mantas are a common sight off Queensland, little was known about their population biology and ecology before a research project called Project Manta took shape in 2007. The project started at The University of Queensland, Brisbane, with industry support from Earthwatch Institute, Lady Elliot Island Eco Resort, and Manta Lodge and Scuba Centre.  Since that time, Project Manta has expanded to cover all of Australia, teaming up with researchers from Murdoch and Deakin Universities, Ningaloo Marine Interactions in Coral Bay, WA and receiving generous support from ARC Linkage grants, Austral Fisheries and TG Kailis Marine Conservation Fund.

The project involves a large citizen science component, where photos from divers and snorkelers are used to help identify individual mantas, estimate population sizes and migration routes. As a result of this project, many knowledge gaps in the basic life history of the reef manta have been filled in such as their distribution, population size, and feeding ecology. Recent findings from this project include an expansion of the previously known range of oceanic mantas to off the coast of Tasmania.6 However, there is still a lot that remains to be learned, and continued monitoring of these gentle giants is needed to ensure populations are still around for generations to come.

How you can help

If you are a diver or snorkeler, you can help Project Manta learn more about mantas and be an active part of this exciting research. All you need is an underwater camera. Mantas can be identified by unique pigmentation markings on their underside. If in the water with a manta, try to get a photo or video of the underside that includes these three target areas:

  • Between the gill slits
  • The belly
  • The pelvic fins

Then send the file, along with the date and location of your sighting and your name to: project.manta@uq.edu.au. You can also share your photo or video on the Project Manta Facebook page.

Example of manta ray ID photo. Photo credit: Julia Sumerling
Example of manta ray ID photo. Photo credit: Julia Sumerling

If you are in the water with a manta, please observe these guidelines to avoid stressing them out:

  • Leave plenty of space for mantas to maneuver
  • Stay low (close to the seafloor), whilst remaining mindful of your surroundings so not to damage the reef
  • Be calm and patient – let the manta see you before approaching
  • Keep at least 3 m between you and the manta – let the manta come to you of its own free will
  • Avoid using a flash when photographing them
  • Avoid touching or attempting to ride mantas – this removes their protective mucus coat
  • Be mindful of your bubbles if diving – these can startle or make a manta feel trapped
  • Continue to learn more about these magnificent creatures and share your new knowledge with friends and family!

 

References

1 Marshall, A. D., Compagno, L. J. V. & Bennett, M. B. Redescription of the genus Manta with resurrection of Manta alfredi (Krefft, 1868) (Chondrichthyes; Myliobatoidei; Mobulidae). Zootaxa 2301, 1-28, (2009).

2 Couturier, L. I. E. et al. Biology, ecology and conservation of the Mobulidae. J. Fish Biol. 80, 1075-1119, (2012).

3 Marshall, A. et al. Manta alfredi The IUCN Red List of Threatened Species 2011, e.T195459A8969079, (2011).

4 Couturier, L. I. E. et al. Distribution, site affinity and regional movements of the manta ray, Manta alfredi (Krefft, 1868), along the east coast of Australia. Mar Freshwater Res 62, 628-637, (2011).

5 Jaine, F. R. A. et al. When Giants Turn Up: Sighting Trends, Environmental Influences and Habitat Use of the Manta Ray Manta alfredi at a Coral Reef. PLoS ONE 7, e46170, (2012).

6 Couturier, L. I. E., Jaine, F. R. A. & Kashiwagi, T. First photographic records of the giant manta ray Manta birostris off eastern Australia. PeerJ 3, e742, (2015).

 

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Ocean Acidification Part 2: What’s that fishy smell?

Blog post by: Meg Welch

In our last post we learned that ocean acidification makes life more difficult for marine life with calcium carbonate skeletons or shells, like corals and crustaceans. But did you know that ocean acidification also affects fish? Research is consistently finding that fish behaviour changes when seawater becomes more acidic. Fish show increased activity levels, an impaired ability to learn, and changes to their senses of hearing and smell1-3. Many of these changes have significant consequences on predator-prey interactions4,5, competition and habitat selection6.

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Fish swimming in a natural carbon dioxide seep in Papua New Guinea. Photo by Alistair Cheal.

When fish experience high CO2 levels predicted for the next 100 years7 for more than four days, they become attracted to predator odours and chemical alarm cues that they would avoid under present-day circumstances. This means that fish willingly put themselves in harm’s way, increasing their death toll. This raises concerns about the ability of fish populations to maintain themselves in the predicted high CO2 world. A few longer-term experiments and studies at natural CO2 seeps indicate that after many weeks to months of high CO2 exposure, fish behaviour remains impaired8.

What’s behind these changes?

It is believed that these behavioural changes in fish are largely due to a chemical fluctuation in the brain that occurs when fish are exposed to high levels of CO29. This action occurs in the GABA-A receptor, whose job is to reduce the activity of brain cells, called neurons, and prevent overstimulation. The changes in ocean chemistry brought on by high levels of CO2 cause changes in the fish blood and tissue, which leads to the abnormal functioning of the GABA-A receptor. This is similar to epilepsy in mammals.

What does this mean for future fish?

While research suggests that individual fish may not be able to change their behaviours back to normal in a high CO2 environment, it is important to consider how all environmental factors such as higher temperatures that will occur simultaneously with rising CO2 levels will affect fish. New research must also consider multiple generations, as CO2 levels will rise over the next 100 years, possibly allowing species enough time to adjust to climate change.

This field of research truly burns with the anticipation for the future. You can keep up to date with the most recent research on ocean acidification by signing up to this list-serve. Stay tuned for new research about fish in a changing environment!

How you can help

You can help fish smell correctly by helping to reduce CO2 emissions. Follow these easy steps to make a difference:

1. Measure your carbon footprint here: http://www.nature.org/greenliving/carboncalculator/

2. Reduce your emissions by carpooling or taking public transport. Our last post had a few more great ideas to help reduce energy consumption as well!

3. If you see anything odd while you’re out swimming, diving or fishing, send a note to Redmap: http://www.redmap.org.au/

 

References

  1. Briffa, M., et al. High CO2 and marine animal behaviour: Potential mechanisms and ecological consequences. Mar. Pollut. Bull. 64, 1519-1528 (2012).
  1. Branch, T. A., et al. Impacts of ocean acidification on marine seafood. Trends Ecol. Evol. 28, 178-186 (2013).
  1. Leduc, A. O. H. C., et al. Effects of acidification on olfactory-mediated behaviour in freshwater and marine ecosystems: A synthesis. Phil. Trans. R. Soc. B 368, 20120447 (2013).
  1. Munday, P. L., et al. Replenishment of fish populations is threatened by ocean acidification. Proc. Natl. Acad. Sci. USA 107, 12930-12934 (2013).
  1. Ferrari, M. C. O., et al. Putting prey and predator into the CO2 equation- qualitative and quantitative effects of ocean acidification on predator-prey interactions. Ecol. Lett. 14, 1143-1148 (2011).
  1. Munday, P. L., et al. Ocean acidification impairs olfactory discrimination and homing ability of a marine fish. Proc. Natl. Acad. Sci. 6, 1848-1852 (2009).
  1. Collins, M., et al. Long-term climate change: projections, commitments and irreversibility. In: Stocker, T. F., et al. (eds) Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, USA, pp 1096-1097 (2013).
  1. Munday, P. L., et al. Behavioural impairment in reef fishes caused by ocean acidification at CO2 seeps. Nature Clim. Change 4, 487-492 (2014).
  1. Nilsson, G. E., et al. Near-future carbon dioxide levels alter fish behaviour by interfering with neurotransmitter function. Nature Clim. Change 2, 201-204 (2012).
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Ocean Acidification Part 1: Reduce our carbon footprint for coral reefs

Blog post by: Regan Jade

Did you know that your daily actions are contributing to the changing chemistry of our oceans?

Coral reefs are incredibly important; they are some of the most biologically rich and economically valuable ecosystems on Earth. They provide food, jobs, income, and protection to billions of people worldwide (2).

However, our actions are threatening our beautiful coral reefs.

Humans are burning fossil fuels and releasing carbon dioxide into the earth’s atmosphere at unprecedented levels (1); this rise in carbon dioxide is a big problem as more than 25% of it is absorbed by our oceans and causing them to increase in acidity. This is termed ocean acidification.  And it’s a big problem for our coral reefs.

The problem with ocean acidification

Most marine organisms are adapted to  a relatively stable ocean pH; however since pre-industrial times, ocean acidity levels have increased by 30%.  Research suggests future ocean acidification rates could be higher than anything experienced in the previous 65 million years (3).

When the ocean increases in acidity, marine organisms like corals and crustaceans find it very difficult to build their shells and skeletons. This is because these organisms use calcium carbonate, the same material that chalk and limestone are made of, to form their shells. Calcium carbonate is typically abundant in seawater, but as the ocean becomes more acidic, it becomes less abundant. This decreases the ability of marine organisms to create structures to sustain their lives, including corals who also create habitat for a large proportion of marine life (4).

Need more convincing? Check out this video of Hermie and his reality with ocean acidification (also a great video to show the kids)

 

Carbon emissions on the rise

Human activity since the Industrial Revolution has increased carbon dioxide levels in our atmosphere from 280 parts per million to 400 parts per million. The last time carbon dioxide levels were this high for a sustained period of time was 2 – 4.6 million years ago (5). Carbon emissions caused by humans come from many sources, including the burning of fossils fuels like coal, oil and gas; deforestation, agriculture, and the production of plastic.

By reducing your carbon emissions, you can help our coral reefs. It may seem like the issue is too much to tackle as an individual but we can all make a difference with our daily actions.

Five things you can do to reduce your carbon emissions and help our coral reefs

  • Drive your car less: The burning of fossils fuels is a major contributor to carbon emissions. Can you bike to work? Take public transport or carpool with your work mates?
  • Eat locally: How far has your food traveled? Reduce your carbon emissions by opting for local produce instead of produce that has been shipped from overseas.
  • Conserve your energy use at home and switch to green energy: Turn off lights when you are not in the room, switch off power points and swap to a green energy provider like Power Shop (6).
  • Reduce your plastic use: Carbon dioxide enters the atmosphere through burning fossil fuels like oil and gas (7). Many Plastics are made from oil and gas so choose to reuse instead, recycle where possible and avoid single-use plastic.
  • Monitor your local reefs: Become a reef searcher with reef check so you can monitor the health of your local reefs over time.

Start with one action at a time and keep building on your new habits when you can. What action will you start with today to help our coral reefs? Let us know in the comments.

 

References

(1) The threat of ocean acidification to ocean ecosystems – John Guinotte and Victoria J Fabry

(2) http://oceanservice.noaa.gov/education/kits/corals/coral11_protecting.html

(3) http://phys.org/news/2010-02-ocean-acidification-fastest-million-years.html

(4) http://www.gbrmpa.gov.au/managing-the-reef/threats-to-the-reef/climate-change/how-climate-change-can-affect-the-reef/ocean-acidification

(5) http://www.sciencealert.com/earth-s-co2-levels-just-permanently-crossed-a-really-scary-threshold?0_2520304173231125=

(6) http://www.powershop.com.au/

(7) https://www.epa.gov/ghgemissions/overview-greenhouse-gases

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An Ocean of Microplastic

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Blog post by: Dr. Alena Pribyl

Plastic is hard to escape; from food and beverage containers to packaging to household items to clothing – it is everywhere in our society.  Despite efforts at recycling, much of this plastic is discarded and ends up in waterways and eventually the oceans.  It is estimated approximately 8 million metric tons of plastic enter the ocean annually1! But what happens to this plastic once it is in the ocean and how does it affect the marine ecosystem?

The dangers of large plastic debris in the oceans are well known – it can kill marine life through entanglement or ingestion. Sea turtles eat plastic bags, seabirds ingest small plastic pieces, fish and marine mammals become entangled in discarded fishing nets and rope. But another danger of marine plastic that we are just starting to understand is the effect of this plastic once it breaks down.  As large plastic pieces are exposed to UV radiation and wave action, they are eventually ground up into smaller and smaller pieces, called microplastics.

Where do microplastics come from?

microplastic

Microplastics are defined as pieces of plastic less than 5mm in size. The main sources of microplastics are large plastic debris that are broken down as described above, and a product called microbeads.  Microbeads are tiny plastic beads found in items such as soaps, facial scrubs and toothpaste where they act as abrasives.  They are usually listed as “polyethylene” or “polypropylene.”  These microbeads get washed down our drains, pass through the sewer system because they are too tiny to be filtered out, and eventually end up in the ocean.

Additionally, scientists have recently discovered another plastic source that is becoming more common in our oceans: plastic fibers from nylon and polyester fabrics.  These come off of clothes during washing, and similar to microbeads, pass through wastewater treatment systems to enter the ocean.

The dangers of a plastic diet

Once microplastics are in the ocean, filter-feeding animals often mistake them for food since they are the perfect size to ingest.  This includes animals such as  zooplankton (microscopic animals that drift in the sea and form the base of the marine food web), forage fish (e.g. sardine, herring),  shellfish (e.g. oysters, mussels), and even large marine mammals such as baleen whales.

 

A diet of plastic is no good for animals because microplastics also contain organic toxins such as polychlorinated biphenyls (PCBs), petroleum compounds, and even pesticides2. Some of these compounds are added to the plastics during manufacture, but many are picked up from the surrounding seawater.

Interesting fact: plastics are really good at taking up chemical “hitchhikers” that are present in low amounts in almost all water bodies. These chemicals are ingested along with the microplastic3.

Chemical-laden microplastics are not immediately lethal to marine animals, but cause problems over long periods of time. Growing evidence shows microplastic toxins accumulate in the tissues of marine organisms4-6 and cause long-term health problems such as reduced reproduction and liver damage7,8.  And the effect is not limited to the animals that directly eat microplastics. When these organisms are eaten by something else (including us), the toxins are transferred to the consumer, allowing them to spread throughout the food web9. This means all consumers of marine life could be at risk from microplastic toxins.

Microplastic oceans

pollutionRecent estimates put the amount of microplastic debris floating in our oceans between 93,000 to 236,000 metric tons10.  Much of this plastic collects in areas of the ocean where currents converge in circular patterns, called gyres – the so called “garbage patches” of the ocean.

However, the distribution of microplastics is not limited to the gyres – microplastics have been found in almost every marine habitat in the world, including the Arctic and remote oceanic islands11.  The spread of microplastics are creating large problems for the health of our ocean ecosystem, many of which we have only started to recognize.

How you can help

The good news is that everyone can do something to help slow this growing problem. We can take action by following these simple measures to reduce the amount of plastic entering our oceans:

  • Avoid purchasing soaps, toothpastes and cosmetics that contain “polyethylene” or “polypropylene” in their ingredients list.
  • Purchase clothes made with natural instead of synthetic fibers
  • Reduce or eliminate your use of items with large amounts of plastic packaging.
  • Use re-usable food and beverage containers.
  • Recycle as much plastic waste as possible
  • Pick up plastic waste you see lying on the ground and participate in local beach/river clean-ups.
  • Let your friends and family know what plastics are doing to our ocean and encourage them to follow these measures as well!

 

References

1 Jambeck, J. R. et al. Plastic waste inputs from land into the ocean. Science 347, 768-771, (2015).

2 Teuten, E. L. et al. Transport and release of chemicals from plastics to the environment and to wildlife. Philosophical Transactions of the Royal Society B: Biological Sciences 364, 2027-2045, (2009).

3 Bakir, A., Rowland, S. J. & Thompson, R. C. Enhanced desorption of persistent organic pollutants from microplastics under simulated physiological conditions. Environ. Pollut. 185, 16-23, (2014).

4 Browne, Mark A., Niven, Stewart J., Galloway, Tamara S., Rowland, Steve J. & Thompson, Richard C. Microplastic Moves Pollutants and Additives to Worms, Reducing Functions Linked to Health and Biodiversity. Curr. Biol. 23, 2388-2392,

5 Chua, E. M., Shimeta, J., Nugegoda, D., Morrison, P. D. & Clarke, B. O. Assimilation of Polybrominated Diphenyl Ethers from Microplastics by the Marine Amphipod, Allorchestes Compressa. Environ. Sci. Technol. 48, 8127-8134, (2014).

6 Avio, C. G. et al. Pollutants bioavailability and toxicological risk from microplastics to marine mussels. Environ. Pollut. 198, 211-222, (2015).

7 Sussarellu, R. et al. Oyster reproduction is affected by exposure to polystyrene microplastics. Proceedings of the National Academy of Sciences 113, 2430-2435, (2016).

8 Rochman, C. M., Hoh, E., Kurobe, T. & Teh, S. J. Ingested plastic transfers hazardous chemicals to fish and induces hepatic stress. Scientific Reports 3, 3263,(2013).

9 Tanaka, K. et al. Accumulation of plastic-derived chemicals in tissues of seabirds ingesting marine plastics. Mar. Pollut. Bull. 69, 219-222,(2013).

10 Erik van, S. et al. A global inventory of small floating plastic debris. Environmental Research Letters 10, 124006 (2015).

11 Lusher, A. in Marine Anthropogenic Litter (eds Melanie Bergmann, Lars Gutow, & Michael Klages)  245-307 (Springer International Publishing, 2015).