News Article | February 27, 2017
An invasive species of marsh grass that spreads, kudzu-like, throughout North American wetlands, may provide similar benefits to protected wetlands as native marsh grasses. According to new research from North Carolina State University, the invasive marsh grass's effects on carbon storage, erosion prevention and plant diversity in protected wetlands are neutral. The findings could impact management strategies aimed at eradicating the invasive grass. Phragmites australis, known as the common reed, is an invasive marsh grass that can spread at rates up to 15 feet per year. It thrives throughout North American wetlands, and studies have demonstrated that its densely packed growth pattern chokes out native marsh plants, thereby reducing plant diversity and habitat used by some threatened and endangered birds. However, other studies have shown that Phragmites may help reduce shoreline erosion in marshlands and store carbon at faster rates than native grasses. Since managing the threat is costly - in 2013, efforts to eradicate Phragmites cost about $4.5 million - Seth Theuerkauf, a Ph.D. candidate in marine, earth and atmospheric sciences at NC State, decided to look at how relative abundance of the marsh grass affected the ecosystem services that humans value from marshes, such as their ability to stabilize shorelines. Theuerkauf and his colleagues looked at impacts of Phragmites on marshes in two protected reserves within the northeastern portion of the North Carolina Coastal Reserve system. In particular, they wanted to compare ecosystem services - plant diversity, shoreline stabilization and carbon storage - between marshes with varying amounts of Phragmites: those with only native grasses, those with a mix of grasses and those with only Phragmites. The findings were encouraging. The team found no significant differences between ecosystem services of the marshes they studied, indicating that Phragmites' effect was largely neutral. However, Theuerkauf points out that the neutral effect could be due to the protected status of the wetlands they studied and the specific ecosystem services evaluated. "Studies that associate Phragmites with negative impacts on wetlands are often conducted in areas that have seen significant human interventions, such as shoreline development or construction of drainage canals, whereas our study was conducted in undisturbed marsh habitat within a protected reserve system," Theuerkauf says. "Our findings highlight the importance of maintaining protected reserves, as they may provide a strong defense against the negative impacts of invasive species and could reduce the time and money spent on trying to eradicate these species," adds Theuerkauf. "Additionally, our results suggest that Phragmites management efforts should also take ecosystem services into account." The research appears online in PLOS ONE. The work was funded in part by North Carolina Sea Grant and the North Carolina Coastal Reserve. Brandon Puckett, research coordinator for the North Carolina Coastal Reserve; NC State graduate student Kathrynlynn Theuerkauf; Ethan Theuerkauf, formerly of UNC-Chapel Hill's Institute of Marine Science and currently at Illinois State Geological Survey; and Dave Eggleston, professor of marine, earth and atmospheric sciences at NC State contributed to the work. Note to editors: An abstract of the paper follows "Density-dependent role of an invasive marsh grass, Phragmites australis, on ecosystem service provision" Invasive species can positively, neutrally, or negatively affect the provision of ecosystem services. The direction and magnitude of this effect can be a function of the invaders' density and the service(s) of interest. We assessed the density-dependent effect of an invasive marsh grass, Phragmites australis, on three ecosystem services (plant diversity and community structure, shoreline stabilization, and carbon storage) in two oligohaline marshes within the North Carolina Coastal Reserve and National Estuarine Research Reserve System (NCNERR), USA. Plant species richness was equivalent among low, medium and high Phragmites density plots, and overall plant community composition did not vary significantly by Phragmites density. Shoreline change was most negative (landward retreat) where Phragmites density was highest (- 0.40 ± 0.19 m yr-1 vs. -0.31 ± 0.10 for low density Phragmites) in the high energy marsh of Kitty Hawk Woods Reserve and most positive (soundward advance) where Phragmites density was highest (0.19 ± 0.05 m yr-1 vs. 0.12 ± 0.07 for low density Phragmites) in the lower energy marsh of Currituck Banks Reserve, although there was no significant effect of Phragmites density on shoreline change. In Currituck Banks, mean soil carbon content was approximately equivalent in cores extracted from low and high Phragmites density plots (23.23 ± 2.0 kg C m-3 vs. 22.81 ± 3.8). In Kitty Hawk Woods, mean soil carbon content was greater in low Phragmites density plots (36.63 ± 10.22 kg C m-3 ) than those with medium (13.99 ± 1.23 kg C m-3) or high density (21.61 ± 4.53 kg C m-3), but differences were not significant. These findings suggest an overall neutral density-dependent effect of Phragmites on three ecosystem services within two oligohaline marshes in different environmental settings within a protected reserve system. Moreover, the conceptual framework of this study can broadly inform an ecosystem services-based approach to invasive species management.
Bertotti L.,Institute of Marine science |
Cavaleri L.,Institute of Marine science
Journal of Marine Systems | Year: 2012
We have explored the possibility of deriving coastal wave conditions from the archived data of operational large scale modelling. Starting from this data, a high resolution nested grid has been used to derive wave results at two locations where buoy data is available. The comparison suggests that the used solution can be used to provide long term statistics or reliable forecasts at desired coastal locations. The accuracy and the limitations of the approach have been explored by analysing the sensitivity of the results to the frequency of the archived information and of the wave model spectral shape. The problems connected to inputting the correct spectral shapes are discussed. © 2012 Elsevier B.V.
Bertotti L.,Institute of Marine science |
Cavaleri L.,Institute of Marine science
Ocean Dynamics | Year: 2011
We have explored the predictability of storms in a small enclosed basin with a complicated surrounding orography. We have considered two exceptional storms in the far past and three mild events happened in recent years. A posteriori forecasts have been done up to 6 days before the events. The results have been compared versus measured data and the related analysis. Good predictability (10-15% error in surface wind speed and wave height) have been found up to day 4, mildly larger (<30%) up to day 6 before the event. In no case was a storm missed. This suggests that the effective predictability in more open basins may extend to even larger ranges. © 2011 Springer-Verlag.
McCulloch M.,University of Western Australia |
Falter J.,University of Western Australia |
Trotter J.,University of Western Australia |
Montagna P.,Laboratoire Des Science Du Climat Et Of Lgenvironnement |
And 2 more authors.
Nature Climate Change | Year: 2012
Rapidly rising levels of atmospheric CO 2 are not only causing ocean warming, but also lowering seawater pH hence the carbonate saturation state of the oceans, on which many marine organisms depend to calcify their skeletons. Using boron isotope systematics, we show how scleractinian corals up-regulate pH at their site of calcification such that internal changes are approximately one-half of those in ambient seawater. This species-dependent pH-buffering capacity enables aragonitic corals to raise the saturation state of their calcifying medium, thereby increasing calcification rates at little additional energy cost. Using a model of pH regulation combined with abiotic calcification, we show that the enhanced kinetics of calcification owing to higher temperatures has the potential to counter the effects of ocean acidification. Up-regulation of pH, however, is not ubiquitous among calcifying organisms; those lacking this ability are likely to undergo severe declines in calcification as CO 2 levels increase. The capacity to up-regulate pH is thus central to the resilience of calcifiers to ocean acidification, although the fate of zooxanthellate corals ultimately depends on the ability of both the photosymbionts and coral host to adapt to rapidly increasing ocean temperatures. © 2012 Macmillan Publishers Limited. All rights reserved.
Portilla-Yandun J.,Escuela Polytechnic NacionalQuito Ecuador |
Cavaleri L.,Institute of Marine science
Journal of Geophysical Research: Oceans | Year: 2016
In this paper, a new methodology is proposed for the computation of Background Errors in wave data assimilation systems. Background errors define the spatial influence of an observation in the model domain. Since at present the directional wave spectrum is the fundamental variable of both state-of-the-art numerical models and most modern instrumentation, this is at the core of the proposed methodology. The advantage of the spectral approach is that the wave spectrum contains detailed information of the different wave systems and physical processes at work (e.g., wind-sea or swells). These systems have different origins and may be driven by different mechanisms, having therefore different spatial structures, length scales, and sensitivity to local wind conditions. The presented method enables making consistent and specific corrections to each component of the spectrum, in time and space. The innovations presented here require an integral look at the data assimilation algorithm for which a suitable scheme is also proposed. Examples of computed background errors are presented for shelf and oceanic basins showing the spatial structures of the different wave systems active in these areas. © 2015. American Geophysical Union.
Bertotti L.,Institute of Marine science |
Cavaleri L.,Institute of Marine science |
Loffredo L.,Catholic University of Leuven |
Monthly Weather Review | Year: 2013
Nettuno is a wind and wave forecast system for the Mediterranean Sea. It has been operational since 2009 producing twice-daily high-resolution forecasts for the next 72 h. The authorshave carried out a detailed analysis of the results, both in space and time, using scatterometer and altimeter data from four different satellites. The findings suggest that there are appreciable differences in the measurements from the different instruments. Within the overall positive results, there is also evidence of differences in Nettuno performance for the various subbasins. The related geographical distributions in Nettuno performance are consistent with thevarious satellite instruments used in the comparisons. The extensive system of buoys around Italy is used to highlight the difficulties involved in a correct modeling of wave heights in Italy's coastal areas © 2013 American Meteorological Society.
Cavaleri L.,Institute of Marine science |
Fox-Kemper B.,University of Colorado at Boulder |
Hemer M.,Center for Australian Weather and Climate Research |
Bulletin of the American Meteorological Society | Year: 2012
The Earth climate system contains a vast range of processes and feedbacks, so it is natural to focus first on the dominant ones, for example, those dominating planetary heat and carbon budgets. However, these basic processes have been modeled with increasing accuracy since the days of Arrhenius (1896a,b). Nowadays, we seek to improve representation and quantify the uncertainty of many more processes. Quite often dominant processes modulate the subdominant, and vice versa, with a whole cascade of reciprocal actions and feedbacks. This last point, feedback, is where difficulties arise, particularly if it occurs within interactions spanning multiple scales. Then practical difficulties of measuring the relevant interactions or the excessive computer power required for simulation limit our development of theoretical and quantitative assessment of how important these feedbacks may be. In this situation, we take a shortcut and use a parameterization that summarizes one, or several, processes into a simplified algorithm. Progress, bias analysis, and experience tell us how much further we need to go to have more accurate and reliable results. Today it is obvious that the atmosphere and ocean are heavily interacting-enormous quantities of heat, energy, water vapor, and carbon dioxide are exchanged each instant through their boundary layers. After the overall radiation balance, these exchange processes are the next priority in providing predictions of the climate system from seasons to centuries. The role of these exchanges is clear, in that the heat capacity of only a few meters of the ocean equals that of the whole atmosphere, and the carbon reservoir of the ocean dwarfs all but the lithosphere. However, having in mind the scale of the planet, it is natural to look at the problem on a large scale. Waves are small in comparison, a tiny distributed detail. However, it is a beautiful example of the little process modulating the overall large-scale behavior. Granted that some of the small-scale processes do affect the large-scale ones, the question is how much they affect the climate. One point of view is that the climate is established by the overall budget of incoming and outgoing radiation. Even if this is the case, two aspects need to be pointed out. First, the distribution of temperature and other parameters will vary based on small-scale processes rather than overall balances, and such distributions and their variations are relevant to humans even if they only slightly affect the global energy balance. Second, as climate is progressively changing through natural and anthropogenic changes, we live in a permanent transient situation. Only application of our best physical principles, rather than empirical parameterizations, can be robust in the face of a changing climate. Science has been slow to appreciate the extent of the interaction between ocean and the atmosphere. It took even longer to understand how these exchanges are modulated by the characteristics of the surface that separates the two phases. Here, we have tried to emphasize how sea state, particularly during wave-breaking conditions and when waves are not equilibrated with the wind, strongly modulates many of the processes that have a direct influence on climate. We still do not grasp the whole physics nor an accurate measure of the degree to which the mean state and climate feedbacks are affected by these modulations, but having an idea of where we want to go is certainly a good start. Many groups worldwide are attempting to quantify these effects of waves on climate in observations, models, and theory, and we celebrate their accomplishments and look forward to their discoveries. We need to carry on, understanding more and more the physics of the thin layer of fluid that, in the immensity of space, surrounds the planet that is our home. © 2012 American Meteorological Society.
News Article | November 5, 2015
COCONUT ISLAND, Hawaii (AP) — Scientists at a research center on Hawaii's Coconut Island have embarked on an experiment to grow "super coral" that they hope can withstand the hotter and more acidic oceans that are expected with global warming. The quest to grow the hearty coral comes at a time when researchers are warning about the dire health of the world's reefs, which create habitats for marine life, protect shorelines and drive tourist economies. When coral is stressed by changing environmental conditions, it expels the symbiotic algae that live within it and the animal turns white or bright yellow, a process called bleaching, said Ruth Gates, director of the Institute of Marine Biology at the University of Hawaii. If the organisms are unable to recover from these bleaching events, especially when they recur over several consecutive years, the coral will die. Gates estimated that about 60 to 80 percent of the coral in Kaneohe Bay has bleached this year. "The bleaching has intensified and got much more serious," said Gates of the coral around the bay. Where they once looked for the bleached coral among the healthy, Gates said her team is now "looking for the healthy individuals in a sea of pale corals." Gates and her team are taking the coral to their center on the 29-acre isle, once a retreat for the rich and famous and home to television's Gilligan's Island, and slowly exposing them to slightly more stressful water. They bathe chunks of coral that they've already identified as having strong genes in water that mimics the warmer and more acidic oceans. They are also taking resilient strains and breeding them with one another, helping perpetuate those stronger traits. The theory they are testing is called assisted evolution, and while it has been used for thousands of years on other plants and animals, the concept has not been applied to coral living in the wild. "We've given them experiences that we think are going to raise their ability to survive stress," Gates said. She said they hope to see these corals, which will soon be transplanted into the bay, maintain their color, grow normally and then reproduce next summer. In early October, the National Oceanic and Atmospheric Administration said that coral reefs worldwide are experiencing bleaching, calling the event extensive and severe. "We may be looking at losing somewhere in the range of 10 to 20 percent of the coral reefs this year," NOAA coral reef watch coordinator Mark Eakin said when the report was released. "Hawaii is getting hit with the worst coral bleaching they have ever seen." And this is the second consecutive year Hawaii has experienced widespread bleaching. Scientists say some coral has already fallen victim to global warming. About 30 percent of the world's population has already perished as a result of above average ocean temperatures, El Nino's effects and acidification. Gates and her team understand the challenges of scalability and time. Having success locally does not necessarily mean they will be able to scale their project to address a massive, global marine crisis before much of the world's coral reefs are already gone. Tom Oliver, a marine biologist and team leader at NOAA's Coral Reef Ecosystem Division, said the project is scalable with the requisite amount of effort and funding. He said, "the question is not can they do it, it's can they do it fast enough?" Oliver said that many reef restoration projects struggle because of the cost and time involved with raising standard coral and planting it in the ocean. "Restoration needs to have brood stock that can handle the changing conditions on reefs," he said. Gates said more research needs to be done before they can begin to address scalability. In 2013, Gates and her Australian counterpart Dr. Madeleine van Oppen, who does coral research at the Australia Institute of Marine Science, won the $10,000 Paul G. Allen Ocean Challenge for their proposal to assist coral evolution. Allen's foundation then asked them for a proposal to fully fund the idea, which they eventually did with a $4 million grant in June. Allen, who co-founded Microsoft with Bill Gates, has various climate-related projects in his philanthropic portfolio.
News Article | January 13, 2016
The research, from the University's Institute of Marine Science, led by Master's student Lucy van Oosterom and including Dr Craig Radford and Professors John Montgomery and Andrew Jeffs, is the first direct evidence that fish communicate to maintain group cohesion. While scientists have known fish send messages to each other for mating purposes or to defend territory, this is the first time research has proved they also use contact calls to keep together. The research team used captive wild Bigeyes (Pempheris adspersa) in the study, a species commonly found along New Zealand's north-east coast. Bigeyes are generally nocturnal, retreating to caves during the day and foraging at night in loosely-knit shoals. Previous work by Dr Radford has shown Bigeyes have a distinctive 'pop' call with an estimated maximum range of 31.6m. This vocal behaviour, coupled with relatively sensitive hearing organs, led researchers to assume Bigeyes communicated in groups but up to now the evidence has been anecdotal. Using underwater hydrophones, a GoPro camera and an MP3 player, the researchers collected almost 100 fish from the Leigh coast north of Auckland and put them in saltwater tanks at Leigh Marine Laboratory. In experiments carried out over five months, they played two types of sound to the captive fish: one of the normal reef environment at Leigh where the fish live, and another recording of Bigeye vocalisations. When the sound recordings were played, the Bigeyes increased their own calling rates by more than five times in order to maintain contact over and above the background noise. They also swam closer together. When there were no sound, the fish swam further apart. "This study means that fish are now the oldest vertebrate group in which this behaviour has been observed and that has interesting implications for our understanding of evolutionary behaviour among vertebrates," Ms van Oosterom says. Explore further: Fish talk to each other, researcher finds More information: L. van Oosterom et al. Evidence for contact calls in fish: conspecific vocalisations and ambient soundscape influence group cohesion in a nocturnal species, Scientific Reports (2016). DOI: 10.1038/srep19098
News Article | November 6, 2015
With ongoing threats that most coral reefs in the world face, scientists are finding ways to save them. Emerging science suggests that "assisted evolution" could be the solution to protecting the corals from damage. Coral reefs protect a wide array of marine species by providing them with a home. However, reef health is in continuous decline as a result of human-induced global warming, which has altered marine ecosystems and robbed species of their natural habitat. The temperature of water is directly proportional to its acidity. As warming waters in the ocean increase its temperature, acidic levels also surge and, as a result, bleaching and weakening of corals occurs. In fact, the researchers said that around 60 to 80 percent of corals in Kaneohe Bay, off the northeast coast of Oahu, have been bleached this year. Scientists will venture into an experiment to grow evolved corals that could withstand warmer and more acidic waters that happen as a side effect of climate change. "The bleaching has intensified and gotten much more serious," said Ruth Gates, director of the Hawaii Institute of Marine Biology and one of the proponents of the study. They are looking for healthy corals in the area to use in their experiment. The team is transferring the healthy coral to its center on Hawaii's Coconut Island to slowly expose it to more stressful water which mimics the level of acidity and temperature of sea water influenced by climate change. They've also developed stronger and more resilient strains by cross-breeding the most resilient coral samples. "We've given them experiences that we think are going to raise their ability to survive stress," Gates said. They are hoping that the corals will grow normally, reproduce and maintain their color when they are brought back to the sea. The theory they wanted to test is called assisted evolution. Gates and her partner, Dr. Madeleine van Oppen, who does coral research at the Australia Institute of Marine Science, first proposed this study in the 2013 Paul G. Allen Ocean Challenge, winning $10,000. After winning, the foundation asked them to conduct a full-blown study with funding of $4 million. Further research will be conducted to ensure efficacy of their theory.