Blue mussels not yet the bellwether of NE coastal environment

Marcy Cockrell installs cages to protect mussels from predators. In Maine, mussels inside cages faired as well as mussels in the wild. In Long Island Sound and Narragansett Bay it was a different story. Credit: Brown University

Ecologists sometimes look to mussel species, a well-studied and foundational genus in estuaries, as model organisms for assessing the condition of coastal habitats, which are crucial for people and well as the broader environment.

But a new study in the journal Ecosphere suggests that the seemingly simple blue mussel, when studied on regional scale from Maine to Connecticut, harbors at least three specific mysteries that must be solved if the mollusks are to serve as the "canaries in the coal mine" of the Northeast coast.

"Mussels could indeed be a good sentinel species for rocky shores, but what our work suggests is that we need to know a lot more about how they behave in these different estuarine settings to use them as an indicator of ecosystem health," said conservation scientist and study senior author Heather Leslie, the Peggy and Henry D. Sharpe Assistant Professor of Environmental Studies.

For the study, Leslie and former students Marcy Cockrell and Joanna Bernhardt monitored and experimented with mussels at 18 sites in the Casco Bay of Maine, the Narragansett Bay of Rhode Island, and the Long Island Sound of Connecticut and New York in 2010 and 2011 (a region spanning about 600 kilometers of coastline). They measured the abundance of mussels both at adult and larval stages, studied the populations of neighboring rocky shore animals and marine algae, and tracked data on ecosystem factors such as water salinity, temperature, nutrients, oxygen, and local human population density. In the experiments, the team protected some mussels with cages to expose the effect that birds, crabs and other predators have on their numbers.

In the end, the research uncovered three intriguing mysteries of mussel life across the region, particularly in Casco Bay:

Generation gaps: Adults were populous but "recruitment" of young mussels from surrounding waters was low in Long Island Sound and Narragansett Bay. The opposite was true in Casco Bay. There, juvenile recruitment was high but adult populations were low. Few Maine predators: The cage experiments showed a significant role for mussel predators in Long Island Sound and Narragansett Bay, but not in Casco Bay. There, unprotected mussels fared about as well as the protected ones. Inner vs. outer: In each estuary, Leslie's team made measurements at sites nestled well within the bay, as well as at sites closer to the open ocean. Prior research suggested that higher levels of food within the bay would promote growth and abundance for the filter-feeding mussels (due to higher levels of nutrients and phytoplankton at the inner estuary sites). The study results were notably mixed across the whole region, however, providing little support for that hypothesis.

Explanations await further research. Genetic studies could determine, for example, whether the young mussels that are so abundant in Casco Bay may be floating up from the more southerly shores. If so, that suggests that mussel population dynamics can only be understood on regional (or multi-estuary) geographic scale.

Meanwhile, understanding why predator activity seems low in Casco Bay might require learning more about the local predator populations there. The findings could shed light on whether the ecosystem is in balance or other factors are at play.

"We did this because we want to understand how these systems work," Leslie said. "Given their accessibility and how well-studied they have been in other locations, rocky shores are logical sentinel ecosystems. They provide an opportunity to investigate how climate change and other more local-scale human activities are affecting New England's coast."

It may take more work to crack open the mussels' mysteries, but the stakes are high enough to make it worthwhile, Leslie said.

Source: Brown University

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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

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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

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Recreational activity a major pollutant on Canadian coast of Pacific Ocean

This is University of Calgary associate professor in geography Stefania Bertazzon.
Credit: Robert Walker

From recreational boats and fishing vessels to commercial cruise ships and private marinas, a newly published study shows that oil discharges related to human maritime activity on the Canadian coast is posing a major threat to marine ecosystems in the Pacific Ocean.

The study -- published in the August edition of the journal Applied Geography, with University of Calgary associate professor in geography Stefania Bertazzon as lead author -- provides a geospatial analysis of oil discharges in the Canadian Pacific Ocean.

The findings show that a large portion of oil discharge within these waters stems from recreational activities, passenger traffic and fisheries. According to this scientific analysis -- conducted on oil spills observed by the National Aerial Surveillance Program with the use of remote sensing devices -- these sources are polluting the ocean along the British Columbia coast more than oil tankers and commercial cargo ships.

"Cargo ships and oil tankers are much more regulated with portside inspections and they have to meet certain standards," explains Bertazzon. "They're very aware of this surveillance and this is probably why our analysis suggests that they are responsible for a smaller portion of detected oil discharges. They have to be more careful."

Bertazzon adds: "We're not saying that cargo ships and oil tankers are not polluting. What we are saying is that they are not the only source of pollution in the Canadian Pacific Ocean."
Bertazzon and her co-authors explain that fuel docks for recreational and fishing vessels can be problematic. "We know that there's a lot of oil discharge in these fuel docks, which is largely uncontrolled," she says.

"One thing that happens in these marinas is there's a lot of old boats which have been sitting there for years slowly leaking into the ocean. These are not huge spills. It's a relatively small discharge. But there's a lot of these derelict vessels and together they make for a large source of pollution."

While there's no denying the impact of large-scale oil industry disasters such as the Gulf of Mexico spill in 2010, Bertazzon argues that the oil discharges related to maritime activities are even more devastating to marine ecosystems in the long run.
"There is scientific evidence to show that these day to day activities have a larger impact on the wild life and the marine ecosystem than those accidents that are huge, but limited in space and time," says Bertazzon. "What we're talking about happens every day, all along the coast. The impact is longer term and over a larger spatial extent."

Source:  University of Calgary

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