Constantine Alexander's Journal

Conserving coral communities

Study suggests coral restoration projects can help restore fish communities.

A diversity of corals. Photo by Toby Hudson (CC BY-SA 3.0).

Spending hours a day diving in and around the coral reefs off St. Croix in the U.S. Virgin Islands sounds like the stuff of a dream vacation, but for Annie Opel it was serious business.

As part of her undergraduate thesis, Opel spent much of her time in the water working on a study showing efforts to restore coral reefs have a positive impact on local fish populations, both in the short term and over time. The study is published in the December issue of Marine Biology with Opel as first author, a rare accomplishment for an undergraduate.

"Reefs are not only biologically important - more than 4,000 species of fish rely on these ecosystems - but they're also really important for humans," Opel said. "We depend on them for commercial and recreational fisheries, they provide protection for coastal communities and they bring in a great deal of money through tourism.

"But right now they're threatened by a number of anthropogenic inputs, from pollution to the effects of climate change," Opel said. "Coral reefs have experienced bleaching and mass mortality all over the world, causing ecosystem degradation that affects the marine life that rely on the reefs to survive."

While there have been efforts to address the problem by transplanting corals grown in underwater "nurseries" to damaged reefs, the effectiveness of such restoration projects on Caribbean reefs has never been rigorously studied, Opel said.

"In St. Croix, they've been restoring corals since 2009," Opel said. "(But) no one is really looking at what's happening after the fact...so no one knows if this is an efficient way to restore (those) reef systems."

What she found, Opel said, is that in as little as a week after creating experimental coral beds, significantly more fish and a greater diversity of species could be found. The study also showed that, over time, the fish community changed as additional species began visiting the sites.

"Overall, it's a success story - we out-planted corals and there were more fish," she said. "That's really exciting and something people took for granted in these restoration projects, but no one had quantified it before. I think it's going to be interesting for future studies to use this as a benchmark to know what's going on after transplanting corals."

The project was a natural fit for Opel, as it allowed her to combine both her interest in ocean conservation and the sciences.

During a gap year after finishing high school, Opel spent time in St. Croix, working with The Nature Conservancy on coral restoration projects. As a sophomore at Harvard, she joined the lab of Colleen M. Cavanaugh, the Edward C. Jeffrey Professor of Biology in the department of Organismic and Evolutionary Biology, and later proposed the coral study for her senior honors thesis. Prof. Cavanaugh took on the challenge of advising Annie on her own independent research with the help of her Post-doctoral Fellow, Dr. Joey Pakes Nelson, an invertebrate biologist and ecologist, and a former Post-doc, Dr. Randi Rotjan, a coral reef expert now an assistant professor at Boston University.

"This work was really cool for a variety of reasons," said postdoctoral fellow Joey Pakes Nelson. "As a global community, we spend a lot of money on coral reef restoration, but few studies describe how this practice affects the reef community, so Annie's work provides justification for investments in this type of conservation.

"When it came time to choose a thesis topic, Annie wanted to combine her love of research with her love of coral," she added. "She had great resources because of her work in the Nature Conservancy, she knew about transplanting corals, she had diving experience and she had a great question."

But having a great idea, however, didn't make it any easier to execute.

"I went down to St. Croix in March over spring break and in collaboration with other researchers, out-planted four two-by-two meter plots of an endangered species of coral found in the Caribbean called Acropora cervicornis," Opel said. "We also designated control plots ten and 20 meters away."

Opel returned to the island at the end of the academic year to plant four additional plots and began the hard work of collecting data almost entirely on her own.

"Each survey day, I spent two hours underwater where I took five minute surveys on each of my 16 plots. I sat there with underwater paper and a clipboard and I would basically mark every fish I saw for that five minutes," Opel said. "It was a steep learning curve, because I needed to learn how to identify every species of fish by sex and age before I started taking my surveys. I took surveys three times a week for all 16 plots, and I counted something like 15,000 fish in total, so it was a lot of sitting underwater in my bright orange wetsuit counting and identifying fish."

One of the most challenging parts of the project, she said, was finding partners to accompany her on dives.

"For safety reasons, you always dive with another person," Opel said. "But it's not like I had an assistant or anyone working with me, so I had to crowdsource my volunteers. I asked around at local dive shops in St. Croix and got put in contact with a lot of great people that wanted to help me with my research. One day my dad even came with me, so that was really special. One of my favorite parts of the paper is the acknowledgments, because I got the chance to thank all the volunteer divers and all of the people that helped make this project happen. And I am really thankful to have had three rock star female scientists to mentor me through this academic journey".

Citation: Opel, A.H., Cavanaugh, C.M., Rotjan, R.D. Joey Pakes Nelson;  Marine Biology 164:221 (2 November 2017); DOI: 10.1007/s00227-017-3248-0.

This research was supported with funding from the Harvard College Office of Undergraduate Research and Fellowships, Harvard University Center for the Environment, Museum of Comparative Zoology, Marine Conservation Action Fund and the National Science Foundation.

Contact: Peter Reuell
Harvard University

 

World War I era maps help track history of kelp forests in Pacific Northwest

Ecologist uses maps produced before World War I, which have quite a history of their own, to track the growth of kelp beds in the Pacific Northwest over the last century.

Prof. Cathy Pfister compares 100-year-old kelp survey maps to modern surveys, finding that most modern kelp beds along the Washington coast have remained as abundant.

In the early 1900s, the U.S. Department of Agriculture recognized a problem. The United States relied heavily on fertilizer to grow crops and support its burgeoning economy, yet a crucial ingredient for fertilizer - potash, a mixture of potassium and salts - was mined almost exclusively in Germany. German mines supplied nearly the entire world's supply of potash, and at the time the U.S. used about a fifth of its output, half of the amount exported from Germany.

"It is obviously undesirable that the United States should be dependent upon any other nation for its supply of a necessity," wrote Frank Cameron, an officer "in charge of chemical, physical and fertilizer investigations" for the USDA, in a 1915 report.

Seeking ways to ease this dependency, the USDA commissioned several surveys of an alternative source of potash: kelp beds in the Pacific Northwest. The large, hardy seaweed is a natural source of potassium, nitrogen and salts, and had been used as fertilizer for years by Native Americans and settlers. If kelp could be harvested and processed in large enough quantities, it could be a viable source of potash to offset German imports.

So, the USDA sent surveyors -- including George Rigg, an ecologist from the University of Washington -- to map the kelp beds along the coast of California, Oregon, Washington and Alaska. Rigg set out in a yacht with a 40-horsepower motor and mapped the coastline around Puget Sound in 1911-12. More than 100 years later, scientists at the University of Chicago used these maps to track historical changes in the kelp forests of the Pacific Northwest.

As it turned out, the original maps from the kelp surveys ended up at the University of Chicago Library, where Cathy Pfister, PhD, professor in the department of ecology and evolution, discovered them. She worked with the library's preservation staff to digitize the maps, and compared them to modern surveys conducted by the Washington State Department of Natural Resources over the past 26 years.

What they found is a relatively rare positive story when it comes to ecological studies in a time of accelerating climate change. The abundance of most modern kelp beds along the Washington coast has remained constant over the last century despite a seawater temperature increase of 0.72 degrees Celsius. The few exceptions are kelp beds closest to Puget Sound, Seattle and Tacoma.

"Kelp are a robust and resilient structure. You can see that in the data, as long as they have access to good water quality and waves flush through them, then they persist," Pfister said.

 

Pfister and her team also studied the competition among kelp species in the area. While the kelp beds were persistent over the decades, their populations could fluctuate greatly from year to year. There are two dominant species -- the annual bull kelp and the perennial giant kelp -- and they fluctuated similarly, meaning that if one was abundant in a given year, so was the other. And good years, it turns out, are associated with colder seawater temperatures, an unfortunate preference for kelp as ocean temperatures continue to rise.

Understanding how changes in the ocean affect kelp is important because they're what's called a "foundation species," a crucial source of food and habitat for organisms.

"Kelp are a natural feature that generates habitat for hundreds, probably thousands of species of fish, invertebrates and microbes," Pfister said. "They're really a locus for biodiversity along these shores, so it's important to understand how they respond to climate change."

While Cameron's 1915 report delves into the chemistry of potassium salts, nitrogen and fertilizer, it's vague on exactly what the U.S. government wanted do with a new kelp-based source of potash. But given that the world's supply of potash came from an increasingly belligerent German Empire just before World War I broke out, one could read between the lines and look to another industry that sprung up around the same time in California. These outfits focused on harvesting kelp and extracting chemicals from it, one of which, potassium nitrate or saltpeter, is a major ingredient of gunpowder.

Ultimately, kelp never became a major source of potash for the U.S. agricultural industry. Following the war, harvesting kelp for nitrogen became far more costly than a new commercial process invented by Fritz Haber in Germany to pull nitrogen from the atmosphere. For the benefit of the many species that depend upon them, the kelp beds (and the historic maps) remain.

Citation: Catherine A. Pfister, Helen D. Berry & Thomas Mumford; The dynamics of Kelp Forests in the Northeast Pacific Ocean and the relationship with environmental drivers; Journal of Ecology, 2017; DOI: 10.1111/1365-2745.12908.

Contact: Matt Wood
University of Chicago Medical Center

Marine turtles dying after becoming entangled in plastic rubbish

This is a live leatherback turtle entangled in fishing ropes which increases drag, Grenada 2014. Credit: Kate Charles, Ocean Spirits.

Hundreds of marine turtles die every year after becoming entangled in rubbish in the oceans and on beaches, including plastic 'six pack' holders and disgarded fishing gear.

The rise in plastic refuse in the ocean and on beaches is killing turtles of all species, with a disproportionate impact on hatchlings and young turtles, research by the University of Exeter shows.

A world-wide survey covering the major oceans where turtles live found that found that 91 per cent of the entangled turtles were found dead. They also suffered serious wounds from entanglement, leading to maiming, amputation or choking. Others that survived were forced to drag disgarded rubbish or debris with them.

The survey found turtles are being tangled up in lost fishing nets, plastic twine and nylon fishing line, as well as six pack rings from canned drinks, plastic packaging straps, plastic balloon string, kite string, plastic packaging and discarded anchor line and seismic cable. Turtles were also discovered entangled in discarded plastic chairs, wooden crates, weather balloons and boat mooring line.

The research, published in Endangered Species Research, sheds light on the true threat of plastic pollution to marine turtles, which, other research has shown, also eat plastic rubbish, and marine creatures caught up in it.

Professor Brendan Godley. Professor of Conservation Science and Director of the Centre for Ecology & Conservation at the University of Exeter's Penryn campus and the lead author warned that as plastic pollution increases more and more turtles are likely to become entangled.

Mortality from entanglement has increased substantially over the last century, as with marine mammals and birds.

84 per cent of the 106 experts surveyed on the Atlantic, Pacific Caribbean, Mediterranean and Indian ocean coast, who responded said they had found turtles tangled in rubbish, including plastic debris and lost or disgarded fishing gear.

The report concluded that, based on the survey results, that more than 1000 turtles are likely to die due to entanglement. But the figure is likely to be a 'gross underestimation' of the scale of the threat to turtles. Not all dead turtles strand on beaches, especially young animals, and some decay at sea. Some of the experts surveyed said that not all stranded turtles are found and that some are removed by local people to eat.

This is a Drowned Green turtle entangled in ghost nets in Uruguay. Credit: Karumbe.

Hatchlings and young sea turtles are particularly susceptible to getting tangled up in lost or disgarded fishing gear or floating debris. Juvenile turtles ride on ocean currents to zones where floating rubbish and debris is concentrated creating an 'ecological trap'. They also 'set up home' near floating debris and can remain there for years.

Professor Godley, the lead author, said the mortality rate from becoming tangled up in human refuse was, in practice, likely to be far higher than 1,000 turtles a year estimated by the limited survey.

"Plastic rubbish in the oceans, including lost or disgarded fishing gear which is not biodegradable, is a major threat to marine turtles. We found, based on beach strandings, that more than 1000 turtles are dying a year after becoming tangled up, but this is almost certainly a gross underestimate. Young turtles and hatchings are particularly vulnerable to entanglement," he said.

"Experts we surveyed found that entanglement in plastic and other pollution could pose a long term impact on the survival of some turtle populations and is a greater threat to them than oil spills. We need to cut the level of plastic waste and purse biodegradable alternatives if we are to tackle this grave threat to turtles' welfare."

The Exeter University research team, which included two research students Emily Duncan and Zara Botterell who work in conjunction with Plymouth Marine Laboratory, surveyed experts who rescue and rehabilitate stranded turtles in 43 countries, to find out if they had discovered turtles which had been tangled up. They also found 23 reports of entangled turtles in peer-reviewed publications, magazines, newspapers and reports.

All species of turtle were found entangled, but Olive Ridley turtles are the most likely species to get tangled up. The species nests in the hundreds of thousands. It forages in areas where marine debris can aggregate. It may also be attracted to feeding on marine rubbish, including disgarded fishing tackle.

Most entanglements recorded were in lost or discarded fishing gear known as 'ghost fishing' rope, nets and lines. Since the 1950s the fishing industry has replaced natural fibres such as cotton, jute and hemp with synthetic plastic materials such as nylon, polyethylene and polypropylene which doesn't biodegrade in water.

The report concludes: "Entanglement with anthropogenic plastic materials, such as discarded fishing gear, as well as land based sources, is an under reported and under researched threat to marine turtles."

But it points out some communities are actively working to rescue turtles that get tangled up. Fishermen in Sicily volunteer to take part in the rescue of turtles in difficulty at sea and on beaches, and are trained to transfer them to rescue centres.

Citation: Duncan EM, Botterell ZLR, Broderick AC, Galloway TS, Lindeque PK, Nuno A, Godley BJ; REVIEW: A global review of marine turtle entanglement in anthropogenic debris: a baseline for further action; Endangered Species Research Vol. 34: 431-448 (December 11, 2017); DOI: 10.3354/esr00865.

Contact: Marie Woolf
University of Exeter

 

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Study finds ways to avoid hidden dangers of accumulated stresses on seagrass

Hundreds of millions of cubic meters of vital seagrass meadows worldwide can potentially be at risk of collapse from accumulated effects of repeated dredging and natural stress.

QUT Research Fellow Dr. Paul Wu is part of a research team working towards saving seagrass from dredging. Photo by Anthony Weate/QUT Marketing & Communication.

A new QUT-led study has found ways to detect hidden dangers of repeated stresses on seagrass using statistical modelling.

The research, published by the Journal of Applied Ecology, found cumulative maintenance dredging which affected the light on the sea floor increased risks on seagrass survival. It found, globally, seagrass meadows can be at risk of collapse from accumulated effects of repeated dredging and natural stress.

However, lead researcher QUT's Dr Paul Wu said maintenance dredging programs of one or two weeks (common in Queensland) were unlikely to impact seagrass.

• Seagrass provide shelter and food to marine life, including at-risk species like dugongs and green turtles
• Globally, hundreds of millions of cubic metres of sediment are dredged annually
• Dredging repeated every 1, 2 or 3 years, or for three months or more duration, needs careful management to avoid a loss of resilience
• Latest research builds on recently released research pinpointing 'ecological windows' for timing of dredging

"Our model predicts ahead of time how much repeated stress is too much," Dr Wu said. "Our results show dredging can be successfully managed to maintain healthy seagrass meadows in the absence of other disturbances. The research isn't about stopping dredging. It's about being able to predict how resilient the seagrass will be by incorporating environmental conditions such as storms, cyclones and run-off from agriculture." Dr Wu said port authorities and coastal developers could use the research to support a risk-informed management strategy.

 

Coastal development is commonly associated with dredging, which presents a hazard to ecosystem health via stressors including light degradation and water quality reduction.

"Generally, dredging repeated every one, two or three years, or of three months duration or more, needs careful management to avoid a loss of seagrass resilience," Dr Wu said.

Dr Wu said the development of a risk modelling approach, based on a Bayesian Network, was a tool increasingly applied in ecology.

The findings of the study are specific to hazards and environmental conditions for individual sites.

"For instance, dredging repeated every one, two or three years on a Halophila meadow at Hay Point was predicted to be at risk of losing resilience," he said.

"We developed 960 hazard scenarios including frequency of dredging durations of between one to six months and the level of light stress and the month when dredging occurred."

Dr Wu is an Associate Investigator with the ARC Centre of Excellence for Mathematical and Statistical Frontiers (ACEMS) within QUT's Mathematical and Statistical Sciences Faculty.

Citation: Paul Pao-Yen Wu, Kathryn McMahon, Michael A. Rasheed, Gary A. Kendrick, Paul H. York, Kathryn Chartrand, M. Julian Caley, Kerrie Mengersen; Managing seagrass resilience under cumulative dredging affecting light: Predicting risk using dynamic Bayesian networks; Journal of Applied Ecology, 2017; DOI: 10.1111/1365-2664.13037.

Contact: Debra Nowland, Queensland University of Technology

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