Seagrass meadows help to support world fisheries productivity
“The chasm that exists between coastal habitat conservation and fisheries management needs to be filled to maximise the chances of seagrass meadows supporting fisheries, so that they can continue to support human wellbeing”
“Scientific research has provided the first quantitative global evidence of the significant role that seagrass meadows play in supporting world fisheries productivity… The study provides evidence that a fifth of the world’s biggest fisheries, such as Atlantic Cod and Walleye Pollock are reliant on healthy seagrass meadows. The study also demonstrates the prevalence of seagrass associated fishing globally….
….Dr Unsworth said: “The coastal distribution of seagrass means it is vulnerable to a multitude of both land and sea based threats, such as land runoff, coastal development, boat damage and trawling. There is a global rapid decline of seagrass and when seagrass is lost there is strong evidence globally that fisheries and their stocks often become compromised with profound negative economic consequences. To make a change, awareness of seagrasses role in global fisheries production must pervade the policy sphere. We urge that seagrass requires targeted management to maintain and maximise their role in global fisheries production.”
Richard K.F. Unsworth, Lina Mtwana Nordlund, Leanne C. Cullen-Unsworth. Seagrass meadows support global fisheries production. Conservation Letters, 2018; e12566 DOI: 10.1111/conl.12566
Underwater grasses that provide vital places for fish and crabs to live and hide from predators covered more than 100,000 acres of the Chesapeake Bay in 2017 — the most ever recorded in a 34-year aerial survey, scientists said Tuesday.
The Virginia Institute of Marine Science found 104,843 acres of grasses across the estuary, the first time since it began its survey in 1984 that vegetative coverage surpassed the 100,000-acre threshold.
It was a third straight year that grass acreage grew, gaining by 5 percent from 2016 to 2017.
The Patapsco River was among the areas with the strongest grass growth. Acreage jumped more than three times, from 3 acres in 2016 to 14 acres in 2017.
Officials with the Chesapeake Bay Program, the federal office that released the data, said the survey results show that its work with bay watershed states to limit pollution is working. The federal-state partnership adopted a “blueprint” in 2010 to reverse decades of environmental degradation and restore the bay’s health by 2025.
The Annapolis-based bay program has faced proposals of cuts from President Donald J. Trump’s administration, but Congress has spared its $73 million budget.
“This achievement is a true example of the power a partnership can have and I call upon all of our partners to continue their efforts toward this remarkable recovery,” said Jim Edward, the program’s acting director…..
Seagrass and kelp may be quite beneficial for reducing the impacts of ocean acidification, especially in California’s bays
Restoring or preserving seagrass and kelp is a win-win measure that would also bring a number of other benefits including providing habitat for many marine species, including economically important fisheries like crab and moderating wave impacts, protecting coastlines from storms.
Hill showed that sediment inside seagrass meadows can contain up to two times as much organic carbon as habitats without vegetation; in summer months, the presence of seagrass can make water significantly less acidic, changing water chemistry up to 0.1 pH units.
Seaweeds and seagrasses have potential to mitigate some effects of ocean acidification, according to a new report presented to the California state legislature earlier this month. The report was supported by the Ocean Protection Council. California Sea Grant Extension Specialist Joe Tyburczy, who is based at Humboldt State University, served on the working group that wrote the report.
“The major take-home message in the report is that seagrass and kelp may be quite beneficial for reducing the impacts of ocean acidification, especially in California’s bays,” Tyburczy says. While many details remain to be studied, the researchers say that restoring or preserving seagrass and kelp is a win-win measure that would also bring a number of other benefits. For example, seagrass meadows are important habitat for many marine species, including economically important fisheries like crab. Kelp and seagrasses can also moderate wave impacts, protecting coastlines from storms.
“There are many reasons we’d want to restore or preserve seagrass meadows. The potential of seagrasses to remove carbon from the water is just icing on the cake,” says University of California, Davis scientist Tessa Hill, who has conducted related research on the topic.
…In her California Sea Grant-funded research in Tomales Bay, California, Hill showed that sediment inside seagrass meadows can contain up to two times as much organic carbon as habitats without vegetation. She also found that in summer months, the presence of seagrass can make water significantly less acidic, changing water chemistry up to 0.1 pH units.
The results of the project were so promising that they led to a larger project to expand the research across the state, and also compare seagrass meadows that were restored rather than native.
The idea of a nature-based solution with multiple benefits sounded good to policymakers who are working on strategies to address ocean acidification. The question will be when, where, and how to prioritize seagrass restoration and protection. That’s where current research aims to fill the gaps…..
Seagrass meadows are CO2 sinks, known as ‘Blue Carbon ecosystems’. They take up and store carbon dioxide in their soils and biomass through biosequestration.
we need to advance our understanding of how seagrass ecosystems, especially those living close to their thermal tolerance, will respond to global change threats, both direct and through interactive effects with local pressures.
In the summer of 2010-2011 Western Australia experienced an unprecedented marine heat wave that elevated water temperatures 2-4°C above average for more than 2 months. The heat wave resulted in defoliation of the dominant Amphibolis antarctica seagrass species across the iconic Shark Bay World Heritage Site…
….Over the three years following the event, the loss of seagrass released up to nine million metric tons of carbon dioxide (CO2) into the atmosphere. This amount is roughly the equivalent to the annual CO2 output of 800,000 homes, two average coal-fired power plants, or 1,600,000 cars driven for 12 months. It also potentially raised Australia’s annual estimate of national land-use change CO2 emissions by up to 21%….
…”This is significant, as seagrass meadows are CO2 sinks, known as ‘Blue Carbon ecosystems’. They take up and store carbon dioxide in their soils and biomass through biosequestration. The carbon that is locked in the soils is potentially there for millennia if seagrass ecosystems remain intact,” explains Professor Pere Masqué, co-author of the study and researcher at ICTA-UAB and the UAB Department of Physics….
…”We need to advance our understanding of how seagrass ecosystems, especially those living close to their thermal tolerance, will respond to global change threats, both direct and through interactive effects with local pressures….
A. Arias-Ortiz, O. Serrano, P. Masqué, P. S. Lavery, U. Mueller, G. A. Kendrick, M. Rozaimi, A. Esteban, J. W. Fourqurean, N. Marbà, M. A. Mateo, K. Murray, M. J. Rule & C. M. Duarte. A marine heatwave drives massive losses from the world’s largest seagrass carbon stocks. Nature Climate Change, 2018 DOI: 10.1038/s41558-018-0096-y
Massive seagrass beds in Western Australia’s Shark Bay — a UNESCO World Heritage Site — haven’t recovered much from the devastating heat wave of 2011, according to a new study demonstrating how certain vital ecosystems may change drastically in a warming climate.
RJ Nowicki, JA Thomson, DA Burkholder, JW Fourqurean, MR Heithaus. Predicting seagrass recovery times and their implications following an extreme climate event. Marine Ecology Progress Series, 2017; 567: 79 DOI: 10.3354/meps12029
Every continent save Antarctica is ringed by vast stretches of seagrass, underwater prairies that together cover an area roughly equal to California.
Seagrass meadows, among the most endangered ecosystems on Earth, play an outsize role in the health of the oceans. They shelter important fish species, filter pollutants from seawater, and lock up huge amounts of atmosphere-warming carbon.
The plants also fight disease, it turns out. A team of scientists reported on Thursday that seagrasses can purge pathogens from the ocean that threaten humans and coral reefs alike. (The first hint came when the scientists were struck with dysentery after diving to coral reefs without neighboring seagrass.)
But the meadows are vanishing at a rate of a football field every 30 minutes. Joleah B. Lamb, a postdoctoral researcher at Cornell University and the lead author of the new study, said she hoped it would help draw attention to their plight….
…The plants also draw fertilizer runoff and other pollutants out of the water, locking them safely away in meadow soil. Scientists have estimated that an acre of seagrass provides more than $11,000 worth of filtering every year….
In one survey, they collected seawater and put it in petri dishes to see if colonies of disease-causing bacteria known as Enterococcus grew from the samples. Levels of the bacteria in water from seagrass meadows, they found, were a third of the levels in water from other sites. In a second search, the scientists grabbed fragments of DNA floating in seawater. By examining the sequences, they identified 18 kinds of disease-causing bacteria. Water from the seagrass meadows had only half the level of this DNA, compared with water collected at other sites. The scientists next turned their attention to coral reefs around the islands. Reefs next to seagrass meadows, they found, were half as diseased as those without meadows.
…Seagrass meadows can store enormous amounts of carbon. Their soils don’t decompose because they have very little oxygen in them. As a result, seagrass meadow soil around the world has accumulated an estimated nine billion tons of carbon.
As seagrass meadows disappear, that carbon is being released back into the ocean. Some of it may make its way into the atmosphere as heat-trapping carbon dioxide. As dire as the situation has become, there is cause for hope. In recent years, Dr. Orth and his colleagues have successfully restored seagrass meadows off the coast of Virginia. “Now we have 6,200 acres of seagrass,” he said, “where in 1997 there wasn’t a single blade of grass.
Seagrass meadows — bountiful underwater gardens that nestle close to shore and are the most common coastal ecosystem on Earth — can reduce bacterial exposure for corals, other sea creatures and humans, according to new research.
…While research is beginning to reveal the mechanisms driving bacterial-load reductions in these ecosystems, it is evident that an intact seagrass ecosystem — home to filter-feeders like bivalves, sponges, tunicates (marine invertebrates) — removes more bacteria from water.
As seagrass meadows and coral reefs are usually linked habitats, Lamb’s team examined more than 8,000 reef-building corals for disease. The researchers found lower levels — by twofold — of disease on reefs with adjacent seagrass beds than on reefs without nearby grasses. “Millions of people rely on healthy coral reefs for food, income and cultural value,” said Lamb….
Joleah Lamb et al. Seagrass Ecosystems Reduce Exposure to Bacterial Pathogens of Humans, Fishes and Invertebrates. Science, 2017 DOI: 10.1126/science.aal1956
A new study links a long-term decline in Chesapeake Bay’s eelgrass beds to both deteriorating water quality and rising summertime temperatures. It also shows that loss of the habitat and other benefits that eelgrass provides comes at a staggering ecological and economic cost…….”Declining water clarity has gradually reduced eelgrass cover during the past two decades, primarily in deeper beds where lack of light already limits growth. In shallow beds, it’s more that heat waves are stressing the plants, leading to the sharp drops we’ve seen in recent summers.”
“Not only have we lost a huge ecological resource, there have been real economic and recreational consequences….Blue crab fisheries, for example, have probably lost a year or more of catch based on the amount of eelgrass we’ve already lost. For silver perch, it’s 10-20 years. In all, we estimate the potential economic cost to citizens at $1-2 billion.”…
…mean summertime water temperature in the lower Chesapeake Bay has already increased by more than 2 degrees Fahrenheit since 1984 — from 76.8° to 79.5°F — and that the frequency of extreme warm spells with water temperatures exceeding 82° has doubled in the last decade….As global warming continues to raise the area’s water temperatures — a conservative estimate is a further 3.5° F increase by 2040 — the team predicts a further 38% decline in eelgrass cover. And if water clarity follows its current downward trajectory during the next 30 years, eelgrass would decline an additional 84%. When both declining clarity and warming are considered, say the researchers, the predicted increases in temperature and turbidity would result in a loss of 95% of Bay eelgrass — a near total eradication…
…”Our analysis suggests that eelgrass could still persist in the face of moderate increases in temperature, if the water remains clear enough” adds Lefcheck. “But that will only happen if managers adopt an integrated perspective, and continue with their efforts to curb inputs into the Bay.“
Jonathan S. Lefcheck, David J. Wilcox, Rebecca R. Murphy, Scott R. Marion, Robert J. Orth. Multiple stressors threaten the imperiled coastal foundation species eelgrass (Zostera marina) in Chesapeake Bay, USA. Global Change Biology, 2017; DOI: 10.1111/gcb.13623
Seagrasses are disappearing at rates that rival those of coral reefs and tropical rainforests, losing as much as seven percent of their area each year. Replanting success rates have been unpredictable — but scientists are making new advances that could change that…
….In the Bay Area, the long strands of eelgrass provide shelter for fish nurseries, prime substrate for the sticky eggs of herring, and food for the small “grazers” that eat the algae coating on the grass. The plant beds also forestall erosion by trapping sediments and slowing down waves or currents. Although researchers estimate around 9,490 hectares (more than 23,000 acres) of the San Francisco coastline could support eelgrass beds, these plants grow on less than one percent of that shoreline. “There are so many different environs in San Francisco Bay, we’d like to come up with a template that helps us determine what methods would work best for each site,” says Boyer, who keeps her office at the Romberg Tiburon Center for Environmental Studies stocked with wetsuits….
…One failure, still unexplained, occurred in Corte Madera Bay, where healthy grass beds died suddenly after years of apparently healthy persistence. Although Boyer wants to keep looking for an answer, she says there isn’t time for that — not if scientists plan to meet the goal of getting 36 more acres of seagrass planted before the nine-year project ends.
If there have been surprising failures, there have also been unexpected successes. Eelgrass is thriving in Elkhorn Slough, an estuary about 100 miles south of San Francisco. Bordered by agricultural fields, the runoff is rich with fertilizer, making the water prone to algal blooms that usually kill seagrass. When algae coats the eelgrass, it diminishes the light available for photosynthesis and plant survival. Despite these conditions, the eelgrass in the Slough is abundant. That anomaly made Brent Hughes, a marine biologist from the University of California at Santa Cruz, wonder: Why?…