Deep coral reefs in Papahanaumokuakea Marine National Monument (PMNM) may contain the highest percentage of fish species found nowhere else on Earth, according to a study by NOAA scientists published in the Bulletin of Marine Science. Part of the largest protected area in the United States, the islands, atolls and submerged habitats of the Northwestern Hawaiian Islands (NWHI) harbor unprecedented levels of biological diversity, underscoring the value in protecting this area, scientists said.Hawaii is known for its high abundance of endemic species — that is, species not found anywhere else on Earth. Previous studies, based on scuba surveys in water less than 100 feet, determined that on average 21 percent of coral reef fish species in Hawaii are unique to the Hawaiian Archipelago.However, in waters 100 to 300 feet deep, nearly 50 percent of the fish scientists observed over a two-year period in the monument were unique to Hawaii, a level higher than any other marine ecosystem in the world. The study also found that on some of PMNM’s deeper reefs, more than 90 percent of fish were unique to the region. These habitats can only be accessed by highly trained divers using advanced technical diving methods.”The richness of unique species in the NWHI validates the need to protect this area with the highest conservation measures available,” said Randy Kosaki, PMNM’s deputy superintendent and co-author of the study. “These findings also highlight the need for further survey work on the monument’s deeper reefs, ecosystems that remain largely unexplored.”Data for the study was collected during two research expeditions to the NWHI aboard NOAA Ship Hi’ialakai in the summers of 2010 and 2012. Some of the unique fish species that were observed include: Redtail Wrasse (Anampses chrysocephalus), Thompson’s Anthias (Pseudanthias thompsoni), Potter’s Angelfish (Centropyge potteri), Hawaiian Squirrelfish (Sargocentron xantherythrum), Chocolate Dip Chromis (Chromis hanui), Masked Angelfish (Genicanthus personatus), and Blueline Butterflyfish (Chaetodon fremblii).Story Source:The above story is based on materials provided by NOAA Headquarters. Note: Materials may be edited for content and length.Read more
Aug. 19, 2013 — Scientists are taking the public with them to study the world’s coral reefs, thanks to 360 degree panoramas from Google’s underwater street-view format. Results from this pioneering project — which will allow ecologists to harness people power to discover how coral reefs are responding to climate change — will be presented at INTECOL, the world’s largest international ecology meeting, in London this week.Professor Ove Hoegh-Guldberg of the University of Queensland leads the research associated with the Catlin Seaview Survey. The Survey uses image recognition technology to automatically assess creatures on the seabed; so far it has already taken hundreds of thousands of images on the Great Barrier Reef and in the Caribbean.”This new technology allows us to rapidly understand the distribution and abundance of key organisms such as corals at large scales. Our expeditions in 2012 to the Great Barrier Reef recorded over 150 km of reef-scape using these methods,” he says.The project is now being expanded by building citizen science into the research, which he hopes will raise awareness and provide more data. “We are planning to involve online citizens to help us count a wide range of organisms that appear in the high-definition images. Anyone with access to a computer will be able to help us log creatures such as stingrays, turtles, fish and Crown of Thorns starfish.””Only 1% of humanity has ever dived on a coral reef and by making the experience easily accessible the survey will help alert millions of people around the world to the plight of coral reefs,” he says.Professor Hoegh-Guldberg will also report findings from ground-breaking research on the impact of climate change on the Great Barrier Reef. At Queensland’s Heron Island research station, he has been running the first-ever long-term climate simulation experiments using computer-controlled systems to manipulate carbon dioxide levels and temperature to simulate past, present and future climate conditions around coral reefs.”Coral reefs have had a hard time adjusting even to the conditions we find ourselves in today with respect to high carbon dioxide levels and sea temperatures. Our work is showing some interesting observations, such as the lack of adaptation of reef communities to the changes that have occurred up until the present,” he explains.”Worse still, our results show that even under the most moderate climate change projections from the Intergovernmental Panel on Climate Change, most corals will struggle to survive and reefs will rapidly decalcify.”Exposing coral and their symbiotic microorganisms, known as dinoflagellates, to future ocean conditions is also revealing how these key organisms cope with changes in acidity and temperature.Professor Hoegh-Guldberg’s experiments show that responses involve the whole organism, not only one or two features of its biology. “The idea that evolution is likely to operate rapidly within these systems is largely unfounded. …Read more
July 10, 2013 — The seeding of marine clouds to cool sea surface temperatures could protect threatened coral reefs from being bleached by warming oceans. Research, published in Atmospheric Science Letters, proposes that a targeted version of the geo-engineering technique could give coral a fifty year ‘breathing space’ to recover from acidification and warming.”Coral bleaching over the last few decades has been caused by rising sea temperatures and ocean acidification,” said Dr Alan Gadian, from Leeds University. “Our research focuses on how Marine Cloud Brightening (MCB) could quickly lower sea temperatures in targeted areas.”There is a strong association between warmer-than-normal sea conditions and cases of coral bleaching. Bleaching is most likely to occur when a 1˚C temperature rise over a prolonged period, typically a 12-week period.To brighten clouds unmanned vehicles are used to spray tiny seawater droplets, which rise into the cloud, thereby increasing their reflectivity and duration. In this way, more sunlight is bounced back into space, resulting in a cooling sea surface temperature.While MCB was originally envisaged to be a global counter measure against warming, in principle the technique could be more targeted. In 2012 Dr. Gadian wrote how the use of MCB in the Atlantic could tame hurricanes.The new modeling study focuses the impact of seeding marine stratocumulus clouds over the Caribbean, French Polynesia, and the Great Barrier Reef. The study shows how the projected increases in coral bleaching, caused by rising CO2 levels, were eliminated while sea surface temperature cooled to pre-warming levels.Mild and severe coral bleaching events were projected over a 20-year period for the three target regions. Without MCB the amount of coral bleaching was seen to be severe; however, simultaneous deployment of MCB eliminated the risk of extra bleaching.”We estimate that MCB would have an annual cost of $400 million, however political, social and ethical costs make a true figure difficult to estimate, said Gadian. “Whatever the final figure, it will be less expensive than the damage the destruction of coral would wreck on neighboring countries, the local food chain and global biodiversity.”Public and political skepticism of geo-engineering projects remains a hurdle to their development; however, as the least disruptive form of Solar Radiation Management, the authors believe small-scale use of MCB for conservation would be unlikely to generate public opposition.The authors propose field-testing of MCB on a scale of 100 square metres, which could demonstrate its use, without producing significant climate effects. …Read more
June 17, 2013 — Ocean acidification due to rising carbon dioxide levels will reduce the density of coral skeletons, making coral reefs more vulnerable to disruption and erosion, according to a new study of corals growing where submarine springs naturally lower the pH of seawater.The study, led by researchers at the University of California, Santa Cruz, and published in the Proceedings of the National Academy of Sciences (PNAS), is the first to show that corals are not able to fully acclimate to low pH conditions in nature.”People have seen similar effects in laboratory experiments,” said coauthor Adina Paytan, a research scientist in the Institute of Marine Sciences at UC Santa Cruz. “We looked in places where the corals are exposed to low pH for their entire life span. The good news is that they don’t just die. They are able to grow and calcify, but they are not producing robust structures.”With atmospheric carbon dioxide rising steadily, the oceans are absorbing more carbon dioxide, which lowers the pH of the surface waters. Ocean acidification refers to changes in seawater chemistry that move it closer to the acidic range of the pH scale, although seawater is not expected to become literally acidic. Paytan’s team studied coral reefs along the Caribbean coastline of Mexico’s Yucatan Peninsula where submarine springs lower the pH of the surrounding seawater in a localized, natural setting. The effect is similar to the widespread ocean acidification that is occurring as the oceans absorb increasing amounts of carbon dioxide from the atmosphere.Led by first author Elizabeth Crook, a graduate student in Paytan’s lab, the researchers deployed instruments to monitor seawater chemistry around the springs and removed skeletal cores from colonies of Porites astreoides, an important Caribbean reef-building coral. They performed CT scans of the core samples to measure their densities and determine annual calcification rates in the laboratory of coauthor Anne Cohen at Woods Hole Oceanographic Institution.The results showed that coral calcification rates decrease significantly along a natural gradient in seawater pH. Ocean acidification lowers the concentration of carbonate ions in seawater, making it more difficult for corals to build their calcium carbonate skeletons.”Carbonate ions are the building blocks they need to grow their skeletons. When the pH is lower the corals have to use more energy to accumulate these carbonate building blocks internally. …Read more
June 5, 2013 — Better land use is the key to preventing further damage to the world’s coral reefs, according to a study published this week in the online science journal Nature Communications.The study, by an international team including a researcher from The University of Western Australia’s Oceans Institute, has important implications for Australia’s Great Barrier Reef.The study authors write that preventing soil erosion and sediment pollution arising from human activities such as deforestation are crucial to reef survival.The study — ‘Human deforestation outweighs future climate change impacts of sedimentation on coral reefs’ — looked at the effects of future climate change on the hydroclimate of Madagascar’s reefs and different deforestation scenarios.”The findings are very relevant for Australia since intense land use and past deforestation have transformed the river catchments tremendously and are seen as a major threat to coral reefs in the Great Barrier Reef and elsewhere,” said Dr Jens Zinke, of UWA’s Oceans Institute.”Managing hinterland land use is the major action needed to buy time for corals growing near rivers.”Dr Zinke said the study looked at four watersheds near coral reef ecosystems in Madagascar, which has different climate zones that mimic most of the world’s coral reef climate and a range of different land uses.”With Madagascar, we wanted to understand how soil erosion and sediment discharges into coral reefs adjacent to river catchments are going to change with these two factors,” he said.”Curbing sediment pollution to coral reefs is one of the major recommendations to buy time for corals to survive ocean warming and bleaching events in the future.”Our results clearly show that land use management is the most important policy action needed to prevent further damage and preserve the reef ecosystem.”The major question is: how do we manage the sedimentation through reforestation efforts and proper coastal management?”Our study clearly shows that we need to have specific reforestation goals/targets for specific regions and make sure that the amount of land allocated for reforestation is enough to reduce sediments significantly.”Until we precisely understand these relationships, reforestation as a tool for coral reef conservation might not meet its objective of sediment and pollution reduction.”The study was the result of a collaboration between the UWA Oceans Institute, the Australian Institute of Marine Science, Macquarie University, the Institute for Environmental Studies at the VU University Amsterdam (Netherlands) and the Wildlife Conservation Society in the US.The lead author is Joseph Maina from Macquarie University.The study was funded through the Marine Science for Management program of the Western Indian Ocean Marine Science Association.Read more
May 9, 2013 — Scientists have identified many benefits for restoring oyster reefs to Chesapeake Bay and other coastal ecosystems. Oysters filter and clean the water, provide habitat for their own young and for other species, and sustain both watermen and seafood lovers.
A new study co-authored by Professor Roger Mann of the Virginia Institute of Marine Science adds another item to this list of benefits — the ability of oyster reefs to buffer the increasing acidity of ocean waters.
The study, “Ecosystem effects of shell aggregations and cycling in coastal waters: An example of Chesapeake Bay oyster reefs,” appears in Ecology, the flagship journal of the Ecological Society of America. It is co-authored by George Waldbusser of Oregon State University and Eric Powell of the Haskin Shellfish Research Laboratory at Rutgers University.
Concerns about increasing acidity in Chesapeake Bay and the global ocean stem from human inputs of carbon dioxide to seawater — either through the burning of fossil fuels or runoff of excess nutrients from land. The latter over-fertilizes marine plants and ultimately leads to increased respiration by plankton-filtering oysters and bacteria. In either case, adding carbon dioxide to water produces carbonic acid, a process that has increased ocean acidity by more than 30% since the start of the Industrial Revolution.
A more acidic ocean concerns marine-life experts, who cite its corrosive effects on the calcium carbonate shells of oysters, clams, and other mollusks, as well as its possible physiological effects on the larvae of fish and other marine creatures. At current rates of increase, ocean acidity is predicted to double by 2100.
The Ecology paper reports on the research team’s efforts to calculate past and present shell budgets for Chesapeake Bay, with a goal of estimating how effective healthy oyster reefs might be in moderating ocean acidity, and whether today’s depleted reefs can withstand future acidity increases.
“Oyster shells are like slow-dissolving TUMS in the belly of Chesapeake Bay,” explains Mann. “As ocean water becomes more acidic, oyster shells begin to dissolve into the water, slowly releasing their calcium carbonate — an alkaline salt that buffers against acidity. An oyster reef is a reservoir of alkalinity waiting to happen.”
The team’s calculations suggest that in 1870 — before people began large-scale harvesting of oyster meat and shells from the Chesapeake — the amount of oyster shell exposed to Bay waters was more than 100 times greater than today, with an equally enhanced capacity to buffer acidity.
“Our data show that that oyster reefs likely played a key role in the pH budget of pre-harvest Chesapeake Bay,” says Mann. “The amount of carbonate in the shells of living oysters at that time was roughly equal to the total amount of carbonate dissolved in the modern Bay. If similar numbers of oysters were alive today, they could take up about half of the carbonate that rivers currently carry into Bay waters.”
Many people are familiar with the notion that the cloudy waters of the modern Bay would be clearer if over-harvesting and disease hadn’t drastically reduced the oyster population and its capacity to filter particles from the water. Mann says, “Our study suggests a similar loss of ecosystem function, but in terms of buffering acidity rather than improving water clarity. This has significant ecological ramifications, but hasn’t really been on anyone’s radar screen.”
Returning oyster shells to Bay waters — a practice that began in earnest in the 1960s to restore reefs for food and filtering — has helped buffer acidity in the Bay, but to nowhere near historical levels. Today, scientists estimate that the Bay loses 100 million bushels of oyster shell each year to harvesting and corrosion in Maryland waters alone, despite the return of 20-30 million bushels of shell through dredging and restaurant recycling.
The study by Mann and his colleagues estimates that oysters now contribute only 4% to buffering of acidity baywide, whereas they were responsible for 70% of all baywide buffering in 1870.
Looking towards the future, the team’s concern is that oyster reefs in the modern Bay — fewer and smaller than their pre-harvest counterparts and featuring smaller oysters — may be unable to keep pace with the increasing acidity of Bay waters.
“The shells of dead oysters degrade rapidly in estuarine environments,” says Mann, “with a half-life of only 3 to 10 years. For a reef to maintain the structure needed to support future generations, oysters must grow fast enough and large enough so that their rate of shell production exceeds that of shell degradation.”
The optimal rate of shell addition, says Mann, “occurs with larger, older animals that contribute more shell carbonate per mortality event.” But, he adds, “the onset of disease has unfortunately reduced the life span and maximum size of Bay oysters, thus compromising the shell budget.”
“What’s worrisome about this is that the shell reservoir is getting smaller and smaller,” says Mann. “Could we reach a tipping point where increasing acidity so overwhelms the decreased buffering capacity of dead shells that it then begins to significantly affect live oysters, further limiting their ability to add shell to the alkalinity buffer? If so, we could end up with a negative feedback loop and a worst-case scenario.”Read more
May 14, 2013 — Limiting the amount of warming experienced by the world’s oceans in the future could buy some time for tropical coral reefs, say researchers from the University of Bristol.
The study, published by the journal Geophysical Research Letters, used computer models to investigate how shallow-water tropical coral reef habitats may respond to climate change over the coming decades.
Elena Couce and colleagues found that restricting greenhouse warming to three watts per square metre (equivalent to just 50-100 parts per million carbon dioxide, or approximately half again the increase since the Industrial Revolution) is needed in order to avoid large-scale reductions in reef habitat occurring in the future.
Shallow-water tropical coral reefs are amongst the most productive and diverse ecosystems on the planet. They are currently in decline due to increasing frequency of bleaching events, linked to rising temperatures and fossil fuel emissions.
Elena Couce said: “If sea surface temperatures continue to rise, our models predict a large habitat collapse in the tropical western Pacific which would affect some of the most biodiverse coral reefs in the world. To protect shallow-water tropical coral reefs, the warming experienced by the world’s oceans needs to be limited.”
The researchers modelled whether artificial means of limiting global temperatures — known as solar radiation ‘geoengineering’ — could help. Their results suggest that if geoengineering could be successfully deployed then the decline of suitable habitats for tropical coral reefs could be slowed. They found, however, that over-engineering the climate could actually be detrimental as tropical corals do not favour overly-cool conditions. Solar radiation geoengineering also leaves unchecked a carbon dioxide problem known as ‘ocean acidification’.
Elena Couce said: “The use of geoengineering technologies cannot safeguard coral habitat long term because ocean acidification will continue unabated. Decreasing the amount of carbon dioxide in the atmosphere is the only way to address reef decline caused by ocean acidification.”
Dr Erica Hendy, one of the co-authors, added: “This is the first attempt to model the consequences of using solar radiation geoengineering on a marine ecosystem. There are many dangers associated with deliberate human interventions in the climate system and a lot more work is needed to fully appreciate the consequences of intervening in this way.”Read more