Why do zebras have stripes?

A mother zebra with a foal in Tanzania’s Tarangire National Park. Credit: Brenda Larison/UCLA

One of nature’s fascinating questions is how zebras got their stripes.

A team of life scientists led by UCLA’s Brenda Larison has found at least part of the answer: The amount and intensity of striping can be best predicted by the temperature of the environment in which zebras live.

In the January cover story of the Royal Society’s online journal, Open Science, the researchers make the case that the association between striping and temperature likely points to multiple benefits — including controlling zebras’ body temperature and protecting them from diseases carried by biting flies.

“While past studies have typically focused their search for single mechanisms, we illustrate in this study how the cause of this extraordinary phenomenon is actually likely much more complex than previously appreciated, with temperature playing an important role,” said Thomas B. Smith, professor of ecology and evolutionary biology in the UCLA College and senior author of the research.

Larison, a researcher in UCLA’s department of ecology and evolutionary biology and the study’s lead author, and her colleagues examined the plains zebra, which is the most common of three zebra species and has a wide variety of stripe patterns. On zebras in warmer climes, the stripes are bold and cover the entire body. On others — particularly those in regions with colder winters such as South Africa and Namibia — the stripes are fewer in number and are lighter and narrower. In some cases, the legs or other body parts have virtually no striping.

Zebras evolved from horses more than 2 million years ago, biologists have found. Scientists have previously hypothesized that zebras’ stripes evolved for one, or a combination of, four main reasons: confusing predators, protecting against disease-carrying insects, controlling body temperature and social cohesion. And while numerous previous studies of the phenomenon focused on a single hypothesis, the Larison-led study was the first to fully test a large set of hypotheses against one another.

Analyzing zebras at 16 locations in Africa and considering more two dozen environmental factors, the researchers found that temperature was the strongest predictor of zebras’ striping. The finding provides the first evidence that controlling body temperature, or thermoregulation, is the main reason for the stripes and the patterns they form.
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Separate research by Daniel Rubenstein, a Princeton University professor of ecology and evolutionary biology and a co-author of the Open Science paper, and Princeton undergraduate Damaris Iriondo strongly suggests that boldly striped zebras have external body temperatures about five degrees Fahrenheit cooler than other animals of the same size — like antelopes — that do not have stripes but live in the same areas. The Rubenstein study is not yet published, but it is cited in the Open Science paper.

Larison has studied many zebras during her field work throughout Africa — including in Kenya, South Africa, Tanzania, Uganda and Zimbabwe. Using the fact that their stripes are unique like fingerprints, she is able to distinguish one zebra from another.

In addition to Rubenstein, arguably the world’s leading expert on zebras, the study’s co-authors were Alec Chan-Golston and Elizabeth Li, former UCLA undergraduates in mathematics; Ryan Harrigan, an assistant adjunct professor in UCLA’s Center for Tropical Research; and Henri Thomassen, a former UCLA postdoctoral scholar and current research associate at the Institute for Evolution and Ecology at Germany’s University of Tübingen.

The research was supported by the National Geographic Society Committee for Research and Exploration.

Larison and her research team have also collected zebra tissue samples and have used cutting-edge technology to sequence zebra DNA to try to identify which genes code for striping. The team is continuing to study the benefits stripes provide.

Source: UCLA

Mass animal die-offs may be increasing, new research shows

Large numbers of dead sunfish and largemouth bass in April 2014 following a severe winter on Wintergreen Lake, Kalamazoo County, Michigan. (Photo courtesy of G. Mittelbach)

Mass die-offs of animals may be increasing in frequency and — for birds, fishes, and marine invertebrates — in severity as well, according to a study of 727 mass mortality events since 1940.

Despite the ecological importance of individual mass mortality events, in which a larger than normal number of individuals die within a population, little research has been conducted on patterns across mass mortality events. The new study will help researchers better assess trends in mass mortality events and their causes, according to the authors of the paper in the Jan. 12 issue of the Proceedings of the National Academy of Sciences.

“The initial patterns are surprising, in terms of the documented changes to frequencies of occurrences, magnitudes of each event, and the causes of mass mortality,” said Samuel Fey, a postdoctoral fellow in the Department of Ecology and Evolutionary Biology at Yale and co-lead author of the paper. “These data also show that we have a lot of room to improve how we document and study these types of rare events.”

Fey, along with fellow researchers at the University of San Diego and University of California-Berkeley, report that the magnitude of the die-offs has increased in birds, fishes, and marine invertebrates, held steady among mammals, and decreased in frogs and amphibians. The authors recognized that more scientific research has been done on mass mortality events in the last few decades but said even accounting for this “discovery bias” does not explain all of the increase in such events. The increase in mass mortality events appears to be associated with a rise in disease emergence, biotoxicity, and multiple interacting stressors, they note.

Overall, disease was the primary culprit, accounting for 26% of the mass die-offs. The impacts of direct human activity, primarily from environmental contamination, caused 19% of such events. Another major cause was biotoxicity triggered by events such as algae blooms, rapid increases of algae in water systems. Processes directly influenced by climate — such as weather extremes, thermal stress, oxygen stress, or starvation — also contributed accounted collectively for about 25% of mass mortality events.

The most severe events were those with multiple causes, the paper shows.

“This study should improve our understanding of the continuum of mortality patterns and processes that exist between background mortality levels and species-level extinctions,” Fey said.

Adam M. Siepielski of the University of San Diego was co-lead author of the paper. Stephanie M. Carlson of the University of California-Berkeley was senior author. Fey began working on this research while a graduate student at Dartmouth College.

Source: Yale University

Hox cluster found in Crown of Thorns starfish a surprise

A Crown of Thorns starfish, Acanthaster planci, feeding on several species of Montipora corals. The image was taken off the coast of Okinawa near Sesoko Island. Credit: Yuna Zayasu

New research published in the journal genesis, by Kenneth Baughman, Dr. Eiichi Shoguchi, Professor Noriyuki Satoh of the Marine Genomics Unit at the Okinawa Institute of Science and Technology Graduate University, and collaborators from Australia, reports an intact Hox cluster in the Crown of Thorns starfish, Acanthaster planci. This surprising result contrasts with the relatively disorganized Hox cluster found in sea urchins, which are also echinoderms, classification of animals including starfish, sea lilies, and sea cucumbers. Stanford University Professor Christopher Lowe, who studies developmental biology in echinoderms, summarizes the paper: "The translocation of the Hox cluster in echinoderms has been a major red herring for understanding their evolution. It's really good to have some hard data showing that some echinoderms exhibit some oddities that are not representative of all echinoderms."

The Hox cluster is a classic example of an 'evo-devo' genetic toolkit. The term "evo-devo" refers to the study of genetic programs that control development, which can be compared between species, and thus, across evolutionary time. 

The Hox genes coordinate segmental identity along the head to tail (anterior-posterior) axis. The Hox cluster is evolutionarily conserved and has been 

repurposed repeatedly during the evolution of the animal body plan, or how animals are shaped. Past studies have shown that Hox clusters organize the development of brain and central nervous system regions in chordates, limb bud identity in vertebrates, and, classically, antennae or wing segment identity in fruit flies.

Generally, the Hox cluster shows "colinearity," in which gene order correlates with the location of expression, or the developmental stage of expression. "For example, anterior Hox genes are expressed in regions that are closer to the head of an embryo, and are expressed sooner during development, versus the posterior Hox genes," explained Baughman. "Thus, we were surprised to see chordate-like Hox cluster organization in starfish, which have a radial body plan." Echinoderms are classical model organisms for embryology, and more recently evo-devo. Baughman added, "Interacting with the speakers and students of theOIST Winter Course 'Evolution of Complex Systems' (OWECS) allowed me to appreciate the importance of finding an intact Hox cluster in starfish."

The Crown of Thorns starfish, a predatory starfish which feeds on corals, is famous for its dramatic changes in population density on the reefs near Australia, as well as Okinawa. Over the past 50 years, this has resulted in a measurable loss of coral reefs. A recent 27-year reef monitoring study of the Great Barrier Reef estimated that the starfish accounts for 42% of the loss in coral cover, 2nd only to typhoons. While population control was the initial motivation for Crown of Thorns genome research, the Hox cluster report is one of the first to show that the species can be useful for studies in evolutionary-developmental biology. "We were excited to see the entire Hox cluster on a single genomic scaffold, a result which confirmed the remarkably high quality of the genomic data," said Prof. Satoh.

As is often the case with science, the discovery raises more questions than it answers. If starfish have a collinear Hox cluster, what accounts for their dramatic departures in body plan organization? Do starfish express Hox genes during development in a manner similar to chordates, as indicated by the organization of their Hox cluster? Baughman looks forward to addressing these questions and many more as part of his doctoral research. "I look forward to pursuing developmental biology studies that may suggest methods for mitigating damage to the coral reef caused by the Crown of Thorns starfish."

More research is being conducted at OIST on the Crown of Thorns starfish in the Marine Biophysics Unit by Masako Nakamura in cooperation with local fishermen. In addition to the research collaboration highlighted by the Hox publication, recent efforts by the Okinawa Prefectural Government and Australian Institute of Marine Science are also working on projects to protect the existing coral reefs from the Crown of Thorns starfish.

Source: Okinawa Institute of Science and Technology - OIST

Teeth, sex and testosterone reveal secrets of aging in wild mouse lemurs

A brown mouse lemur in the wild. Mouse lemurs, weighing a mere 30 to 80 grams, are the world's smallest primates. Credit: Jukka Jernvall

Mouse lemurs can live at least eight years in the wild -- twice as long as some previous estimates, a long-term longitudinal study finds.

PLOS ONE published the research on brown mouse lemurs (Microcebus rufus) led in Madagascar by biologist Sarah Zohdy, a post-doctoral fellow in Emory's Department of Environmental Sciences and the Rollins School of Public Health. Zohdy conducted the research while she was a doctoral student at the University of Helsinki.

"It's surprising that these tiny, mouse-sized primates, living in a jungle full of predators that probably consider them a bite-sized snack, can live so long," Zohdy says. "And we found individuals up to eight years of age in the wild with no physical symptoms of senescence like some captive mouse lemurs start getting by the age of four."

It is likely that starvation, predation, disease and other environmental stressors reduce the observed rate of senescence in the wild, Zohdy notes, but a growing body of evidence also suggests that captive conditions may affect mental and physical function.

"We focused on wild mouse lemurs because we want to know what happens naturally when a primitive primate is exposed to all of the extrinsic and intrinsic mortality factors that shaped them as a species," Zohdy says. "Comparing longevity data of captive and wild mouse lemurs may help us understand how the physiological and behavioral demands of different environments affect the aging process in other primates, including humans."

The study determined ages of wild mouse lemurs in Madagascar's Ranomafana National Park through a dental mold method that had not previously been used with small mammals. In addition to the high-resolution tooth-wear analysis for aging, fecal samples underwent hormone analysis.

The researchers found no difference between the longevity of male and female mouse lemurs, unlike most vertebrates where males tend to die first.

"And even more interestingly, we found no difference in testosterone levels between males and females," Zohdy says. Mouse lemurs are female dominant, which may explain why their testosterone levels are on a par with males.

"While elevated male testosterone levels have been implicated in shorter lifespans in several species, this is one of the first studies to show equivalent testosterone levels accompanying equivalent lifespans," Zohdy says.

A co-author of the study is primatologist Patricia Wright of the Centre ValBio Research Station in Madagascar and Stony Brook University. Other institutions involved in the study include Colorado State University, Duke University and the University of Arizona, Tucson.
Mouse lemurs, found only on the island of Madagascar, are the world's smallest primates. They are among nearly 100 species of lemurs that arrived in Madagascar some 65 million years ago, perhaps floating over from mainland Africa on mats of vegetation.

Mouse lemurs weigh a mere 30 to 80 grams but in captivity they live six times longer than mammals of similar body size, such as mice or shrews. Captive gray mouse lemurs (Microcebus murinus) can live beyond age 12. By age four, however, they can start exhibiting behavioral and neurologic degeneration. In addition to slowing of motor skills and activity levels, reduced memory capacity and sense of smell, the captive four-year-olds can start developing gray hair and cataracts, Zohdy says.

The wild brown mouse lemurs in the study were trapped, marked and released during the years 2003 to 2010. A total of 420 dental impressions were taken from the lower-right mandibular tooth rows of 189 unique individuals. Over the course of seven years, 270 age estimates were calculated. For 23 individuals captured three or more times during the duration of the study, the regression slopes of wear rates were calculated and the mean slope was used to calculate ages for all individuals.

"We found that wild brown mouse lemurs can live at least eight years," Zohdy says. "In the population that we studied, 16 percent lived beyond four years of age. And we found no physical signs of senescence, such as graying hair or cataracts, in any wild individual."

Limitations of the study include the inability to document gradual physiological symptoms of senescence in the wild. "Our results do not provide information about wild brown mouse lemurs that can be directly compared to senescence in captive gray mouse lemurs," Zohdy says. "Further research, using identical measures of senescence, will help to reveal whether patterns of physiological senescence occur consistently across the genus and in both captive and wild conditions."

Another confounding factor Zohdy cites is "the Sleeping Beauty effect," the fact that wild mouse lemurs hibernate for half the year, possibly boosting their life span.
"We now know that mouse lemurs can live a relatively long time in the wild," she says, "but we don't know the exact mechanisms behind why they live so long."

Source: Emory Health Sciences

Dolphins are attracted to magnets: Add dolphins to the list of magnetosensitive animals, French researchers say

Bottlenose dolphins

Add dolphins to the list of magnetosensitive animals, French researchers say. Dolphins are indeed sensitive to magnetic stimuli, as they behave differently when swimming near magnetized objects. So says Dorothee Kremers and her colleagues at Ethos unit of the Université de Rennes in France, in a study in Springer's journal Naturwissenschaften -- The Science of Nature. Their research, conducted in the delphinarium of Planète Sauvage in France, provides experimental behavioral proof that these marine animals are magnetoreceptive.

Magnetoreception implies the ability to perceive a magnetic field. It is supposed to play an important role in how some land and aquatic species orientate and navigate themselves. Some observations of the migration routes of free-ranging cetaceans, such as whales, dolphins and porpoises, and their stranding sites suggested that they may also be sensitive to geomagnetic fields.

Because experimental evidence in this regard has been lacking, Kremers and her colleagues set out to study the behavior of six bottlenose dolphins in the delphinarium of Planète Sauvage in Port-Saint-Père. This outdoor facility consists of four pools, covering 2,000 m² of water surface. They watched the animals' spontaneous reaction to a barrel containing a strongly magnetized block or a demagnetized one. Except from this characteristic, the blocks were identical in form and density. The barrels were therefore indistinguishable as far as echolocation was concerned, the method by which dolphins locate objects by bouncing sound waves off them.

During the experimental sessions, the animals were free to swim in and out of the pool where the barrel was installed. All six dolphins were studied simultaneously, while all group members were free to interact at any time with the barrel during a given session. The person who was assigned the job to place the barrels in the pools did not know whether it was magnetized or not. This was also true for the person who analyzed the videos showing how the various dolphins reacted to the barrels.

The analyses of Ethos team revealed that the dolphins approached the barrel much faster when it contained a strongly magnetized block than when it contained a similar not magnetized one. However, the dolphins did not interact with both types of barrels differently. They may therefore have been more intrigued than physically drawn to the barrel with the magnetized block.

"Dolphins are able to discriminate between objects based on their magnetic properties, which is a prerequisite for magnetoreception-based navigation," says Kremers. "Our results provide new, experimentally obtained evidence that cetaceans have a magenetic sense, and should therefore be added to the list of magnetosensitive species."

Source: Springer Science+Business Media

Trade winds ventilate the tropical oceans: Explanation for increasing oxygen deficiency

Scheme of the tropical Pacific: Strong growth of plankton (1) leads to a high oxygen consumption and extended oxygen minimum zones (2). Ocean currents (3) at a few hundred meters depth provide an influx of oxygenated water from the subtropics (4). Fluctuations of the trade winds (5) influence the strength of these currents. Credit: Graphics: Claus Böning, Markus Scheinert, GEOMAR

Long-term observations indicate that the oxygen minimum zones in the tropical oceans have expanded in recent decades. The reason is still unknown. Now scientists at the GEOMAR Helmholtz Centre for Ocean Research Kiel and the Collaborative Research Centre 754 "Climate -- Biogeochemical Interactions in the Tropical Ocean" have found an explanation with the help of model simulations: a natural fluctuation of the trade winds. The study has been published in the international journal Geophysical Research Letters.

The changes can be measured, but their reasons were unknown. For several decades, scientists have carefully observed that the oxygen minimum zones (OMZ) in the tropical oceans are expanding. These zones are a paradise for some specially adapted microorganisms, but for all larger marine organisms such as fish and marine mammals they are uninhabitable. Thus, their expansion has already narrowed down the habitat of some fish species.

Marine scientists from the GEOMAR Helmholtz Centre for Ocean Research Kiel and the Kiel Collaborative Research Centre (Sonderforschungsbereich, SFB) 754 "Climate -- Biogeochemical Interactions in the Tropical Ocean" now have found a possible reason for these changes by using a model simulation of climate and biological processes. As their study shows, the trade winds north and south of the Equator play a crucial role in the supply of oxygen to tropical sea water. "So fluctuations in the trade winds could also be responsible for the observed enlargement of the oxygen minimum zones in recent years," explains Dr. Olaf Duteil, lead author of the study, which has now been published in the international journal Geophysical Research Letters.

OMZs exist in different intensities at the eastern edges of all tropical oceans. Because nutrient-rich water from the depths reaches the surface in these areas plankton thrives particularly well. Therefore large amounts of plankton organisms die there, too. After their death they sink down to the ocean floor. On the way down bacteria start to decompose the biomass. In doing so they consume the oxygen. The largest of these OMZs stretches from the coasts of Chile and Peru far into the Pacific ocean.

At the same time currents at a few hundred meters depth transport oxygen-rich water from the subtropics towards the tropics, where the oxygen minimum zones lie. "One can think of the tropical Pacific Ocean as a bathtub. When I open the tap, I fill the bathtub with water or 'oxygen', respectively. When the siphon is open, too, we lose oxygen at the same time. We then have an instable equilibrium between input and output," explains Dr. Duteil, "If I turn off the tap a little, the tub empties slowly."

As the researchers were able to determine in a computer simulation of the oxygen balance now, the strength of the currents and thus the oxygen flow to the tropics is directly related to the strength of the trade winds. "It is well known that they vary on a decadal time scale," says co-author Prof. Dr. Claus Böning from GEOMAR, "but these variations haven never been investigated in relation to the oxygen budget of tropical oceans. "

Since the trade winds have been in a weak phase since the mid-1970s, this could be the explanation for the observed enlargement of the oxygen minimum zones. "The oxygen bathtub of the tropical oceans is emptying," says Dr. Duteil. Once the trade winds come back into a stronger phase, the process will be reversed.

This does not mean that external processes such as the general global warming have no influence on the oxygen concentrations in the tropical oceans. "There is evidence that global change affects the major wind systems of the Earth. That would have a direct impact on the oxygen transport in the subtropical and tropical ocean," explains Prof. Andreas Oschlies, co-author and speaker of the SFB 754. "But it is important that according to this study the trade winds in any case as must be considered as a factor for long-term development of tropical oxygen minimum zones," Oschlies adds.

Source: Helmholtz Centre for Ocean Research Kiel (GEOMAR)

Microplastics in the ocean: Biologists study effects on marine animals

A marine isopod of the genus Idotea with food pellets.
Credit: Photo Alfred Wegener Institute / Julia Hämer

Ingestion of microplastic particles does not mechanically affect marine isopods. This was the result of a study by biologists at the North Sea Office of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) that was published recently in the journal Environmental Science and Technology. The study marks the launch of a series of investigations aimed at forming a risk matrix on the sensitivity of different marine species to microplastic pollution.

Uptake of large plastic items by birds and fish may cause blockage of the gastrointestinal tract and severe starvation of the animals. "We were wondering whether small plastic particles have a comparable effect on smaller animals," says Dr. Lars Gutow from AWI's North Sea Office. "Only very limited research has been done on the effects of microplastics on living beings. Accordingly, there is great uncertainty about the implications for marine animals," the biologist explains the motivation for the study.

Lars Gutow and his colleagues selected the isopod Idotea emarginata as their model organism for an initial case study. In feeding experiments the researchers offered the isopods artificial algal food supplemented with plastic particles. The food contained three different kinds of microplastics in varying concentrations. They used industrially produced polystyrene particles with a diameter of ten micrometers as well as self-made fragments and fibres made of polyethylene and polyacryl, respectively.

The researchers studied the fate of the different materials under a light microscope, with the help of a fluorescence microscope, and with an electron microscope. They were able to trace the path of the microplastic particles through the isopods and determine the concentrations of the particles in different sections of the digestive system. The study showed that the concentration of microplastics in the faecal material of the isopods was as high as in the food. The scientists found small amounts of microplastics both in the stomach and in the gut of the animals. However, they did not detect any microparticles in the digestive glands. "The isopods ingested and excreted the artificial food with the microplastic particles without absorbing or accumulating the particles," Gutow summarises the results. Thus, plastic particles in the specific size range studied do not represent a direct mechanical risk for isopods and probably not for other crustaceans either. "In the case of Idotea emarginata, the microplastic particles did not enter the digestive gland, which is the principle organ in crustaceans where digestion and resorption of nutrients takes place," states the biologist from AWI's North Sea Office.

In a long-term experiment the scientists could also show that isopods did not display any long-term effects even after feeding on microplastic enriched food for six to seven weeks. 

Fitness parameters such as survival rate and growth did not differ between animals that were fed with and without microplastics, respectively. In an earlier study, however, AWI biologist Prof. Dr. Angela Köhler demonstrated that mussels show inflammatory reactions if they take up and absorb high concentrations of microplastic in an experiment. This clearly shows that different animal species react differently to microplastics. "In contrast to filter feeding mussels, isopods of the genus Idotea probably take up more frequently indigestible particles with their food in their natural habitat and may, thus, have adapted accordingly," elucidates Gutow.

But the biologists are not only interested in the feeding type: "We want to study systematically how the life style, habitat, physiology and anatomy of different marine organisms influence the uptake and utilisation of microplastic particles in order to come up with a risk matrix for diverse types of organisms," says Lars Gutow. "Therefore, it will be necessary to also study the possible chemical (toxic) and biochemical effects in addition to the physical effects that we looked at," he outlines future tasks.

Source: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

Dolly Varden are a species of char common in southeast Alaska. The fish shown is in spawning coloration.

Not all species may suffer from climate change. A new analysis shows that Dolly Varden, a species of char common in southeast Alaska, adjust their migrations so they can keep feasting on a key food source -- salmon eggs -- even as shifts in climate altered the timing of salmon spawning.

The resiliency of species to climate change may depend on how well they adapt to climate-driven changes in their food and habitat, such as altered growth of plants they feed on. A mismatch in timing between predators and the availability of prey could cause some species to lose access to food. But others such as Dolly Varden that successfully adjust to shifts in climate and prey offer a climate change story with a happy ending, according to the study published in Freshwater Biology.

Ignoring environmental cues may help this predator

The Dolly Varden's secret appears to be that instead of taking its migration cues from environmental variables such as water temperature or streamflow, the species cues directly off the presence of salmon the Dolly Varden depend on for food, the study found.

"Despite warming temperatures and shifting salmon migrations, Dolly Varden do a great job of following their food," said lead author Chris Sergeant of the National Park Service's Inventory and Monitoring Program in southeast Alaska. "Species that can handle a high degree of variability are the ones that should be most resilient to further changes associated with climate."

Dolly Varden get most of their energy over the course of each year by gorging themselves on salmon eggs, which are abundant in summer and rich in energy thanks to the same fatty acids that make fish healthy for humans. Eggs from any single species of salmon may be available during a narrow spawning window of two to six weeks. The Dolly Varden must follow salmon migrations closely to take full advantage of this annual salmon egg bonanza.

Sticking with salmon to find food

But salmon migrations are shifting as the climate warms. Previous research by the University of Alaska and NOAA Fisheries' Alaska Fisheries Science Center in southeast Alaska's Auke Creek has shown that pink and coho salmon now migrate to their spawning grounds 10 to 17 days earlier while sockeye salmon migrate eight days earlier.

Instead of falling out of synch with salmon, though, seagoing Dolly Varden in Auke Creek have accurately adjusted their annual migrations from the ocean back to freshwater to stick with the salmon. The adjustment has maintained their access to egg meals, according to the new research that includes coauthors from the University of Wyoming and NOAA Fisheries' Northwest Fisheries Science Center.

Researchers rely on long record of fish migration data

The research depended on a wealth of fish data from a weir on Auke Creek maintained primarily since 1980 by NOAA Fisheries' Alaska Fisheries Science Center Auke Bay Labs, supported by collaborations with the University of Alaska Fairbanks and Alaska Department of Fish and Game. From 1997 to 2006 crews counted and measured Dolly Varden migrating from the ocean, past the weir and into Auke Creek, providing an unusual long-term picture of fish migration times.

"We're really indebted to the people who kept that record going for so long," said Eric Ward of the Northwest Fisheries Science Center. "It turns out to be very valuable in understanding how species are responding to the changing climate."

Researchers in the new study used the weir data to examine the relationship between migrations of salmon and Dolly Varden from year to year. They found the timing of Dolly Varden migration more closely related to the presence and timing of the salmon than on environmental variables such as temperature and precipitation that are often seen as driving animal migrations.

In short, the Dolly Varden are shifting their migration to follow their food instead of following temperatures or other environmental cues that, as the climate changes, might otherwise lead them to migrate at a different time than the salmon that provide their most important food.

The researchers cautioned that it's unclear whether other salmon predators could adjust their timing to follow salmon as effectively as Dolly Varden do, apparently by watching salmon passing by or detecting salmon eggs through smell. But the adaptability of Dolly Varden suggests that at least some species may be more resilient to climate-induced changes in migration timing than ecologists might assume.

Source: NOAA Fisheries West Coast Region

You can hear the coral reefs dying, experts say

A lionfish in an Indonesian reef. Credit: Image courtesy of University of Essex

You can hear the sound of former bustling coral reefs dying due to the impact of human activity, according to new research from the Universities of Essex and Exeter.

Coral reefs are amongst the noisiest environments on our planet and healthy reefs can be heard using underwater microphones from kilometres away.

However, scientists have found that coral reefs impacted by human activity, such as overfishing, are much quieter than protected reefs, which can have a big impact on the fish and invertebrates which rely on the reefs for survival.

Led by Dr Julius Piercy, from the University of Essex, the study, which also involved the University of Derby, involved taking acoustic recordings of coral reefs with different levels of protection around islands in the Philippines. The research found that the noise produced by the few remaining resident fish and crustaceans on unprotected reefs was only one third of the sound produced at bustling, healthy reef communities

This is particularly important to the larval stages of reef fish and invertebrates, which spend the first few days of their life away from reefs and use sound as an orientation cue to find their way back. With less sound being produced at impacted reefs, the distance over which larvae can detect habitat is ten times less, impacting on the replenishment of future generations needed to build up and maintain healthy population levels.

"In an environment where underwater noise plays such an important role in the population dynamics of coral reefs, it is alarming to find such a large effect of human impact on the natural acoustic environment," explained Dr Piercy. "This puts reef sound in the spotlight for the people who manage coral reef ecosystems on two counts. Firstly, that they might need to consider reef sound as an integral part of the design of marine protected area networks to ensure that there is sufficient recruitment of larvae within and between reserves and neighbouring reefs. Secondly, this study shows sound can be useful in monitoring the health of coral reefs."

With growing evidence demonstrating the direct impacts of human-made noise on aquatic life, these findings highlight additional indirect human impacts -- such as overfishing and landscape development -- on natural underwater sounds.

Dr Steve Simpson, from Biosciences at the University of Exeter, added: "Taking sound recordings is a cheap, fast and objective way to get a broad idea of whether a reef is in a good condition or not. While it cannot replace detailed visual surveys conducted by snorkelers or divers, it gives a good account of the cryptic and nocturnal species missed in visual census, and quickly provides a general picture of the state of coral reefs without requiring time-consuming surveys and extensive training."

The researchers also found that reef sounds can be detected further away than predicted, increasing previous estimates of the likely detection zone for recruiting larvae and increasing the potential importance of reef sound in attracting new fish and crustaceans to coral reefs.

The study highlights the need to further characterise reef soundscapes and identify acoustic cues that larvae tune into when seeking a suitable home. Dr Simpson said: "We still know very little about what sounds these animals are listening to and it is likely to be very different between species. Combined with recent findings that fish dislike the smell of impacted reefs (another homing cue used by the larvae), there is a real need to understand how human impacts can indirectly affect the success of future generations of reef organisms."

Source: University of Essex

Combatting illegal fishing in offshore marine reserves

Fishing boat. Credit: Henry Wolcott

Conservation scientists say there needs to be a new approach to protecting offshore marine reserves.

Illegal fishing in marine reserves will be a major focus at the IUCN World Parks Congress, which has opened in Sydney.

Researchers at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University, who are attending the conference, have found a way to predict illegal fishing activities to help authorities better protect marine reserves.

Marine reserves are the most common strategy used to protect and maintain marine ecosystems around the world.

The International Convention of Biological Diversity aims to have 10 per cent of the world's marine areas protected by 2020.

Many countries are contributing to this target by protecting remote, offshore areas. For example, the United States recently created the world's largest fully protected marine reserve, covering almost 1.27 million square kilometres in the central Pacific Ocean.

But scientists are concerned that while a great deal of effort is being made to create reserves, many countries are simply not able to enforce the laws that are supposed to protect them.

fishing gear. Image: Todd Steiner, Sea Turtle Restoration Project
The majority of fishers obey the law, but some don't.

"The success of protected areas depends on whether people comply with the regulations," says Professor Joshua Cinner from Coral CoE.

"Enforcement and compliance issues for large off-shore marine parks are fundamentally different to near-shore protected areas," Professor Cinner says.

He explains that the biggest problems facing countries trying to enforce offshore marine reserves is their distance from land and the difficulty and cost of patrolling large tracts of ocean.
"The distances to these areas can be very large. They are a long way from prying eyes and quite often the regulations are such that you have to actually catch people illegally fishing to prosecute them," Professor Cinner says.

"It can be extremely difficult for authorities to catch illegal fishers in the act."

In a bid to combat the problem, researchers at Coral CoE examined five years' worth of data collected from the World Heritage-listed Cocos Island National Park, a unique marine protected area in the Pacific Ocean about 500 kilometres off the west coast of Costa Rica.
From the records they were able identify illegal fishing patterns and predict both when and where illegal fishing was likely to happen.

They found that illegal fishing was concentrated in a few 'hotspots' and really ramped up during specific lunar phases of some months.

Professor Bob Pressey, also from Coral CoE, says authorities could use this knowledge to match patrols to the time and place when illegal fishers are most likely to be in action.
"Using a targeted approach helps authorities catch and deter illegal fishers, while saving money on patrols," Professor Pressey says.

"Rather than just hoping you can catch illegal fishers effectively by random patrols, we have used previous patrols to look for patterns which tell us when and where people fish illegally," adds Professor Cinner.

Study lead author, Coral CoE PhD candidate, Adrian Arias says the model of predicting illegal patterns from old records can be used to increase the success of patrols in other locations.

"Our research in Costa Rica showed how a systematic and periodic analysis of patrol records can help to increase the probability of catching illegal fishers. This could be done pretty much anywhere that patrol data are available," he says.

Professor Cinner adds that by better targeting limited resources, authorities have a greater chance of successfully protecting marine parks.

"Targeting resources is particularly important for developing countries such as Costa Rica, which have taken on the conservation challenge but don't have the same funding to ensure compliance as a country such as Australia."

Source: ARC Centre of Excellence in Coral Reef Studies

Seeing the forest for the trees: Youngest trees in a forest tell the biggest story

LSU ecologist Kyle Harms co-authors first study to quantify the process of diversification in forests and likely all other sessile ecosystems. Credit: Louisiana State University

The largest trees in a forest may command the most attention, but the smallest seedlings and youngest saplings are the ones that are most critical to the composition and diversity of the forest overall. While many people gaze up into the forest canopy, scientist Joseph Connell has spent much of his career looking down quite closely at the forest understory. Connell, who is a professor emeritus in the Department of Ecology, Evolution and Marine Biology at the University of California at Santa Barbara, established one of the world's longest, in-depth ecological research studies on the planet. The Connell Plots Rainforest Network has thus far produced a 50-year collection of data on individual trees in Australia's protected rainforests.

"Having such a long-term, detailed dataset is highly unusual. It's the kind of temporal depth we need to answer some of the big questions such as, what are the ecological processes that maintain diversity?" said Kyle Harms, professor in the LSU Department of Biological Sciences and a collaborator with Connell.

Early in his career, Harms was a post-doctoral researcher in Connell's lab at U.C. Santa Barbara. There, he met former fellow post-doctoral researcher and current collaborator Peter Green, who is a senior lecturer at La Trobe University in Melbourne, Australia.

Harms and Green were inspired to use their mentor's dataset; therefore, they devised an analysis to test the long-standing hypothesis that the patterns of composition and diversity among a forest's mature trees are largely set by processes that occur in trees' earliest life stages. Harms ran statistical analyses on 7,977 individual trees across 186 species that were censused in one of Connell's tropical Australian forest plots from 1971-2013.

He repeatedly ran simulation analyses on six tiers of trees based on size in order to predict the expected outcome of diversity at each tier. Then he compared the expected levels of diversity in each tier with the true collected data.

"What we found was that the seedlings are more diverse than the statistical expectations predicted them to be, but the larger trees' levels of diversity were about the same as the predictions" he said.

These results are the first quantitative evidence that the earliest life cycle stages of individual trees are more critical than later stages to the overall relative abundances of mature trees in a forest. Their findings will be published online in the Proceedings of the National Academy of Sciences this week.

The stronger influence of ecological sorting processes operating at the earliest life cycle stages compared to later life stages, which they quantified, also likely occurs in other highly diverse ecosystems with rooted, or sessile, organisms including grasslands, herbaceous plant communities and marine communities of coral.

"I think this is something that is happening broadly in ecosystems across the planet," Harms said.

He and his collaborators' results underscore the importance of support for long-term, in-depth datasets, as well as the need to investigate the early life stages -- for example, the smallest, newly germinated seedlings -- where the most critical processes are occurring.

"I think it helps us understand where to focus in order to really understand the biased sorting processes that create the composition and diversity patterns in the forest overall," he said.

Source: Louisiana State University

How pace of climate change will challenge ectotherms

Turtles sunning themselves (stock image). Turtles are ectotherms, one of many that will be threatened by climate change, researchers say.
Credit: © xoanon / Fotolia

Animals that regulate their body temperature through the external environment may be resilient to some climate change but not keep pace with rapid change, leading to potentially disastrous outcomes for biodiversity.

A study by the University of Sydney and University of Queensland showed many animals can modify the function of their cells and organs to compensate for changes in the climate and have done so in the past, but the researchers warn that the current rate of climate change will outpace animals' capacity for compensation (or acclimation).

The research has just been published in Nature Climate Change (Letters), written by Professor Frank Seebacher School of Biological Sciences and Professor Craig Franklin and Associate Professor Craig White from the University of Queensland.

Adapting to climate change will not just require animals to cope with higher temperatures. The predicted increase to fluctuations in temperature as well as to overall temperature would require animals to function across a broader range of conditions. This is particularly important for ectotherms, animals that rely on external sources of heat to control body temperature, and are therefore more influenced by environmental temperatures.

The research showed that many groups of ectotherms, which make up more than 90 percent of all animals, are able to change their physiological function to cope with an altered environment, but the rapid pace and fluctuations of human-induced climate change present serious challenges.

The researchers studied 40 years of published data to assess how biological functions change in response to a sudden fluctuations in environmental temperatures. They found that the physiological rates of ectothermic animals, such as heart rate, metabolism and locomotion, had already increased over the past 20 years with increasing average temperatures.

"It is important that animals maintain the right balance between the large number of physiological functions despite environmental fluctuations. An increase in temperature that leads to changed reaction rates can upset that balance and cause the decline of individuals and species," said Professor Seebacher. "For example, movement requires energy and oxygen to be delivered to muscles. However, if metabolism or the cardiovascular system can't cope with increased temperatures, animals can no longer move to forage, migrate or interact with each other.

"The overall trend in the last 20 years has been to increased physiological rates, and we predict that this would continue to increase with increasing temperature. "Even if animals are able to maintain the balance of their physiological functions in a warmer climate, increased metabolism leads to increases in the food resources needed and could upset the balance in ecosystems, particularly if predator and prey populations respond very differently to the environmental temperature change."

Source: University of Sydney

Biologist reveals how whales may 'sing' for their supper

Humpback whales.
Credit: Susan Parks

Humpback whales have a trick or two when it comes to finding a quick snack at the bottom of the ocean. But how they pinpoint that meal at night, with little or no available light, remains a mystery.

Susan Parks, assistant professor of biology in the College of Arts and Sciences, in collaboration with a consortium of other researchers, has been studying these unique feeding behaviors. Her research emphasizes the importance of specific auditory cues that these mammoth creatures emit as they search the deep ocean for their prey.

Her findings are the subject of an article in the December issue of Scientific Reports ("Evidence for acoustic communication among bottom foraging humpback whales," 2014), co-authored by researchers at Moss Landing Marine Laboratories, Oregon State University, Gerry E. Studds Stellwagen Bank National Marine Sanctuary and the Whale Center of New England.

"Humpback whales are known to cooperate with others to corral prey near the surface," says Parks, who studies marine science and acoustic communication. "Recent studies suggest they may cooperate [with each other], when feeding on bottom prey, as well."

Parks was part of a collaborative multi-institutional consortium that has spent a decade monitoring humpback feeding behaviors in the Gerry E. Studds Stellwagen Bank National Marine Sanctuary, off the coast of Massachusetts. Whales were tagged with special underwater recording devices so Parks could determine how specific acoustic sounds correlated with successful seafloor feeding.

The investigation revealed that whales make "tick-tock" noises while hunting together at night in deep, pitch-black water, but are silent when hunting alone.

On the menu? Mostly sand lance -- eel-like fish known to bury themselves in the sand of the ocean floor. Parks suggests that whales' vocal sounds may help flush the sand lance out of hiding to where they're scooped up and eaten.

The clock-like sounds created by whales may also serve as a dinner bell of sorts for other nearby whales during late-night feedings.

"Hints of behavior suggest that other whales who overhear the sounds are attracted to them and may eavesdrop on other whales hunting for food," Parks adds.

Prior to joining Syracuse's faculty in 2011, Parks held various appointments at Pennsylvania State University, Cornell University and the Woods Hole Oceanographic Institution. She is the recipient of numerous honors and awards, including the Presidential Early Career Award for Scientists and Engineers, the U.S. government's highest honor for scientists and engineers.

Source:  Syracuse University

Bald reef gets new growth with seaweed transplant

Transplanted seaweed is attached to a reef by a team member. Credit: Image courtesy of University of New South Wales

Marine ecologists in Sydney have successfully restored a once thriving seaweed species, which vanished along a stretch of the city's coastline during the 1970s and 80s when there were high levels of sewage.

A team of researchers from UNSW, the Sydney Institute of Marine Science and the NSW Department of Primary Industries has transplanted fertile specimens of the missing crayweed (Phyllospora comosa) onto two barren reef sites where it once grew abundantly.

They took seaweed from Palm Beach and Cronulla and transplanted it to Long Bay and Cape Banks. Their results are reported in the journal PLOS ONE.

"Seaweeds are the 'trees' of the oceans, providing habitat structure, food and shelter for other marine organisms, such as crayfish and abalone," says lead author, Dr Alexandra Campbell, from the UNSW Centre for Marine Bio-Innovation.

"The transplanted crayweed not only survived similarly to those in natural populations, but they also successfully reproduced. This creates the potential for a self-sustaining population at a place where this species has been missing for decades," she says.

Large brown seaweeds -- known as macroalgae -- along temperate coastlines, like those in NSW, also encourage biodiversity and are important to the region's fishing and tourism industries.
However, these seaweed ecosystems face increasing threats of degradation due to human impacts and ocean warming. The authors say the potential environmental and economic implications of losing these habitats would be comparable to the more highly publicised loss of Australia's tropical coral reefs.

In 2008, researchers from UNSW and the NSW Department of Primary Industries (DPI) showed that a 70 km stretch of this important habitat-forming crayweed had vanished from the Sydney coast decades earlier, coinciding with a period known for high levels of sewage.

Despite improved water quality around Sydney after the introduction of better infrastructure in the 1990s, which pumped sewage into the deeper ocean, the 70 km gap of depleted 'underwater forest' -- between Palm Beach and Cronulla -- has never been able to recover naturally.

Now, with some well-executed intervention, it looks as though this habitat-forming crayweed could make a successful comeback in Sydney's coastal waters.

"This is an environmental good news story," says research supervisor UNSW Professor Peter Steinberg, Director of the Sydney Institute of Marine Science.

"This kind of restoration study has rarely been done in these seaweed-dominated habitats, but our results suggest that we may be able to assist in the recovery of underwater forests on Sydney's reefs, potentially enhancing biodiversity and recreational fishing opportunities along our coastline."

The researchers say their results could provide valuable insights for restoring similar macroalgae marine ecosystems in Australia and globally, but further research is needed to understand the complex processes that affect recruitment and survival.

This project was funded in part by a grant from the NSW Recreational Fishing Trust.


Source:  University of New South Wales

Scientists uncover hidden river of rubbish threatening to devastate wildlife

The sheer amount of plastic recovered shows there is an unseen stream of rubbish flowing through London which could be a serious threat to aquatic wildlife. Credit: Image courtesy of University of Royal Holloway London

Thousands of pieces of plastic have been discovered, submerged along the river bed of the upper Thames Estuary by scientists at Royal Holloway, University of London and the Natural History Museum.

The sheer amount of plastic recovered shows there is an unseen stream of rubbish flowing through London which could be a serious threat to aquatic wildlife. The findings, published online in Marine Pollution Bulletin, highlight the cause for concern, not only for ecosystems around the river but for the North Sea, in to which the Thames flows.

Using nets designed to catch Chinese mitten crabs, Royal Holloway and the Natural History Museum scientists documented rubbish collected during a three-month trial. More than 8,000 pieces of plastic were collected, including large numbers of cigarette packaging, food wrappers and cups, but more than a fifth of waste was made up of sanitary products.

Dr Dave Morritt, a Senior Lecturer in Marine Biology at Royal Holloway and co-author of the study says: "The unusual aspect of the study is that these nets are originally designed to trap fish and crabs moving along the river bed, so we can see that the majority of this litter is hidden below the surface. This underwater litter must be taken into account when predicting the amount of pollution entering our rivers and seas, not just those items that we can see at the surface and washed up on shore. The potential impacts this could have for wildlife are far reaching: not only are the species that live in and around the river affected, but also those in seas that rivers feed into."

The waste collected for the study is only a small snapshot of the volume of litter which may exist at the bottom of the Thames. Plastic bags and other large items were unlikely to get caught in the small nets so the true extent of the problem is still unknown.

Dr Paul Clark, a researcher, at the Natural History Museum and co-author of the study says: "All of this waste, which was mostly plastic, was hidden underwater so Londoners probably don't realise that it's there. Plastic can have a damaging impact on underwater life. Large pieces can trap animals but smaller pieces can be in advertently eaten. This litter moves up and down the river bed depending on tides. The movement causes the pieces of plastic to break down into smaller fragments. These are small enough to be eaten by even the smallest animals, which are in turn eaten by larger fish and birds. Once digested, plastic can release toxic chemicals which are then passed through the food chain. These toxic chemicals, in high doses, could harm the health of wildlife."

Scientists are increasingly pressing for changes to both policy and consumer behaviours, as the dangers of plastics become more apparent.

Source: University of Royal Holloway London

Better regulations needed for deep-sea biology

Deep-sea biology. Credit: Image courtesy of Radboud University Nijmegen

Although we know relatively little about the deep sea, we do extract raw materials for electronics and medicines from it. Biologist Erik Dücker describes the history of deep-sea biology in his thesis. He also gives some pointers on policy and on how to protect this remarkable but rather inaccessible area. He will receive his PhD at Radboud University on 23 September.

Deep-sea biology involves doing research below a depth of one thousand metres. 'The upper thousand metres and the seabed are familiar areas, since they are relatively easy to research', Dücker explains, 'but we are very much in the dark, literally and metaphorically, about the area in between. Deep-sea research is extremely expensive and complicated. Just one expedition day costs $30,000. However, the field biologists that do go down to that depth discover new species on every expedition. So the prospects for new knowledge are good.'

Harvesting manganese nodules from the deep sea
Such prospects make it essential to have a clear policy. Industries like deep-sea mining will do anything to obtain licences to exploit the area, while the consequences of mining remain underexplored. For example, they want to harvest manganese nodules from the seabed. These 'lumps' have taken millions of years to grow and contain traces of the valuable rare-earth metals used to produce electronic appliances like iPhones. Inactive hydrothermal vents -- cracks in the Earth's crust -- contain such metals too.

Policy on rare-earth metals
At present, 95% of rare-earth metals come from China. Buyers (mainly Western countries) are therefore looking for alternative sources. Many have set their sights on the deep sea. However, 'harvesting manganese nodules is anything but sustainable. They are not replaceable because nodule formation is the slowest geological process we know. In addition, harvesting is technically difficult and expensive, so for a long time it was thought to be impossible. Nevertheless, experts expect this harvesting to happen on a larger scale within the next ten years, so we quickly need to agree on ways of doing this properly.'

Double role for deep-sea biologists
Dücker hopes his thesis will make policymakers realise that they not only have to protect the deep sea but also the deep-sea biologists. 'There are few deep-sea biologists, so they often have a double role. Governments as well as companies and environmental protectionists ask them to do research and to gather information. They have a heavy responsibility to deal fairly with conflicting interests and to remain autonomous.'

Source:  Radboud University Nijmegen