Canal could turn Lake Nicaragua into ‘dead zone’

Paula Leighton in SciDev.net: The Interoceanic Canal that will run through Lake Nicaragua could kill life in the vast lake and have other serious effects on the country’s environment and economy unless safeguards are put in place, an independent international panel of experts has warned.

Scientists from the InterAmerican Network of Academies of Science joined biodiversity, engineering and hydrology experts from the Nicaraguan Academy of Sciences (CAN) and the International Council for Science (ICSU) to warn that the project must minimise “unintended adverse consequences” that could do economic, environmental and social harm.

Because of a lack of publicly available information from the Nicaraguan government and HKND, the Chinese firm building the canal, the panel sought to identify “the main technical and scientific questions” in order to “contribute to a public and transparent debate”, Jorge Huete-Pérez, CAN vice-president, tells SciDev.Net.

The water in Lake Nicaragua, Central America’s largest lake, is currently suitable for drinking, irrigation and “other ecosystem services essential to Nicaragua’s economy”. The lake is particularly vulnerable because it is shallow, with an average depth of 12.5 metres, and is exposed to wind action that encourages sediment to be brought back into suspension

Canal construction, which began last month, will require the lake to be dredged to a depth of 30 metres for 105 kilometres. Together with ongoing maintenance and traffic, it will considerably lower water quality and may impair the lake’s usefulness, says the summary document of a workshop on scientific and technical issues associated with the canal, held in Managua, Nicaragua, on 10-11 November....

An 1870 map of an earlier attempt at a canal across Nicaragua. Created by Julius Bien and Company, it is titled Panoramic View of the Nicaragua Canal

Drought led to massive “dead zone” in Lake Erie

A press release from the Carnegie Institution: Lake Erie just can’t catch a break. The lake has experienced harmful algal blooms and severe oxygen-depleted “dead zones” for years, but now a team of researchers led by Carnegie’s Anna Michalak and Yuntao Zhou has shown that the widespread drought in 2012 was associated with the largest dead zone since at least the mid-1980s.

Until now, the size of the dead zone each summer and the factors explaining the variability from year to year have been elusive. Using 28 years of data collected in and around the lake, the team
was able to “measure” the size of the dead zone each summer and identify factors that explain the year-to-year variability for the first time. They found that the 2012 drought, with extremely low water inflow from tributaries, was associated with a record-breaking dead zone in the lake, and that meteorological factors together with agricultural practices explain why these events vary annually. Previous studies have focused on phosphorous from agricultural runoff as the primary driver of the lake’s dead zones, but this analysis shows that the inflow of water from tributaries is actually the largest explanatory factor. The results are published in Environmental Science & Technology.

“Fresh water dead zones—areas depleted of oxygen—result when massive amounts of phosphorus and nitrogen are added to the water, often from fertilizer runoff from agriculture,” explained Michalak. “The excessive nutrients promote excessive growth of algae. When the algae die and decompose, the oxygen in the water gets used up and can drop to levels too low for aquatic life to survive. This happens especially when the water is stratified, with warm water layered on top of cold water, keeping new oxygen from reaching the bottom of the lake.”

The revelation about the size of the dead zone in 2012 comes on the heels of the record-setting harmful algal bloom that occurred in 2011, and the closure of the Toledo water supply in August 2014 due to high concentrations of Cyanobacteria-produced toxins at the city’s water intake. Whereas the record-setting dead-zone event occurred during the 2012 drought, the 2011 record-setting algal bloom was attributed to intense spring storms and various other confounding factors....

NASA image of a 2011 toxic algae bloom in Lake Erie

Oxygen depletion in the Baltic Sea is 10 times worse than a century ago

Space Daily via SPX: After several years of discussions, researchers from Aarhus University (Denmark), Lund University (Sweden) and Stockholm University (Sweden) have determined that nutrients from the land are the main cause of widespread areas of oxygen depletion. The results were published on 31 March in the prestigious American journal Proceedings of the National Academy of Sciences.

The deepest areas of the Baltic Sea have always had a low oxygen content. The inflow of fresh water is actually limited by low thresholds at the entrance to the Baltic Sea. At the same time, there is a relatively fresh layer above the denser and saltier water in the deep layer of the sea. This results in an effective stratification of the water column, which prevents the mixing of water masses necessary to transfer oxygen to the water at the bottom.

During the last century, the areas of oxygen depletion have increased drastically from approximately 5,000 km2 in around 1900 to the present day, where they extend to 60,000 km2 - or about one and a half times the total area of Denmark.

"We analysed data for the water temperature, oxygen content and salinity stretching back for 115 years. On the basis of this analysis, we can determine that the many nutrients from the land are the main cause of the widespread oxygen depletion," says Professor Jacob Carstensen, Department of Bioscience, Aarhus University.

...During the last twenty years, climate change has also played a role in the poor oxygen situation. Warmer conditions reduce the solubility of oxygen from the atmosphere and increase oxygen consumption because the biological respiration processes are boosted.

"The water temperature has risen and will continue to rise in the years ahead. It's therefore extra important that all the countries surrounding the Baltic Sea are committed to the Baltic Sea action plan they joined, and that they comply with the necessary efforts to reduce the release of nutrients into the Baltic," emphasises Professor Carstensen, who is also director of the Baltic Nest Institute in Denmark....

Belarus and Baltic countries on Carta Marina

Ocean dead zones more deadly for marine life than previously predicted

Stony Brook University Newsroom: Ocean dead zones – regions with levels of oxygen too low to sustain marine life - have grown to become a common feature of coastal regions around the world.  A new study published in the January 8 issue of PLOS One by Christopher Gobler, Professor in the School of Marine & Atmospheric Sciences at Stony Brook University and colleagues, has found that low pH levels within these regions represent an additional, previously unappreciated, threat to ocean animals.

For decades, marine biologists have investigated the effects of low oxygen on marine life without considering pH levels. In reality, low oxygen waters are also acidified waters, but studies investigating how these two conditions affect marine life together have been lacking.

In a series of experiments on young bay scallops and hard clams, marine organisms of significant economic and ecological value, the investigators found that the combined effects of low oxygen and low pH led to higher rates of death and slower growth than by either individual factor.  Further, in some cases there was negative synergy between these environmental factors, which means that the performance of the animals was worse than predicted by either individual factor.

The paper, Hypoxia and acidification have additive and synergistic negative effects on the growth, survival, and metamorphosis of early life stage bivalves, written by Gobler, SoMAS Prof. Hannes Baumann, and Stony Brook graduate students, Elizabeth Depasquale and Andrew Griffith, has important implications for climate change as well.

“Low oxygen zones in coastal and open ocean ecosystems have expanded in recent decades, a trend that will accelerate with climatic warming,” said Gobler. “There is growing recognition that low oxygen regions of the ocean are also acidified, a condition that will intensify with rising levels of atmospheric CO2 due to the burning of fossil fuels causing ocean acidification. Hence, the low oxygen, low pH conditions used in this study will be increasingly common in the World’s Oceans in the future.”...

Image by NOAA Photo Library: fish4524, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Scientists find large Gulf dead zone, but smaller than predicted

NOAA: NOAA-supported scientists found a large Gulf of Mexico oxygen-free or hypoxic “dead” zone, but not as large as had been predicted. Measuring 5,840 square miles, an area the size of Connecticut, the 2013 Gulf dead zone indicates nutrients from the Mississippi River watershed are continuing to affect the nation’s commercial and recreational marine resources in the Gulf.

“A near-record area was expected because of wet spring conditions in the Mississippi watershed and the resultant high river flows which deliver large amounts of nutrients,” said

Hypoxia is fueled by nutrient runoff from agricultural and other human activities in the watershed. These nutrients stimulate an overgrowth of algae that sinks, decomposes and consumes most of the oxygen needed to support life. Normally the low or no oxygen area is found closer to the Gulf floor as the decaying algae settle towards the bottom. This year researchers found many areas across the Gulf where oxygen conditions were severely low at the bottom and animals normally found at the seabed were swimming at the surface.

This is in contrast to 2012, when drought conditions resulted in the fourth smallest dead zones on record, measuring 2,889 square miles, an area slightly larger than Delaware. The largest previous dead zone was in 2002, encompassing 8,481 square miles. The smallest recorded dead zone measured 15 square miles in 1988. The average size of the dead zone over the past five years has been 5,176 square miles, more than twice the 1,900 square mile goal set by the Gulf of Mexico / Mississippi River Watershed Nutrient Task Force in 2001 and reaffirmed in 2008.

...“NOAA’s investment in the Gulf of Mexico continues to yield results that confirm the complex dynamics of hypoxia and provide managers and the public with accurate scientific information for managing and restoring the nation's valuable coastal resources,” said Robert Magnien, Ph.D., director of NOAA’s Center for Sponsored Coastal Ocean Research. “For those who depend upon and enjoy the abundant natural resources of the Gulf of Mexico, it is imperative that we intensify our efforts to reduce nutrient pollution before the ecosystem degrades any further.”...

Map showing the hypoxia area on the Louisiana Gulf of Mexico shelf in 2013. Credit: LUMCON (Rabalais)

'Dead zones' could happen in the Great Lakes

Matthew Hall in the Holland Sentinel (Michigan): Scientists are studying how extreme weather associated with climate change may produce more of the algae that create dead zones in the Great Lakes. Figuring it out may help government agencies manage the threat algae poses in light of further projected changes in climate.

Climate change presents a “perfect storm” for the Great Lakes because the sequence and intensity of extreme weather creates just the right conditions for blooms to flourish, said R. Jan Stevenson, co-director of Michigan State University’s Center for Water Sciences. He heads a research team studying the situation.

This past summer, dry conditions and hot weather have contributed to pea soup conditions in parts of Lake Macatawa at Holland. The Ottawa County Health Department issued no-body-contact warnings for two local beaches in August.

Over the next three years, the work will include modeling of Muskegon Lake in Muskegon County, Saginaw Bay in Lake Huron, Grand Traverse Bay on Lake Michigan and the Grand River – the state’s longest river — which is one of the biggest sources of nutrients that flow into Lake Michigan, Stevenson said.

Algal blooms are rapid increases in algae caused by an excess of nutrients like the phosphorus and nitrogen often used in farm fertilizers. Harmful blooms can produce natural toxins. And when they die and decompose, they use up dissolved oxygen, creating a “dead zone” that suffocates fish and other organisms....

Lake Huron, viewed by NASA

Good news from the bad drought: Gulf 'Dead Zone' smallest in years

EurekAlert: The worst drought to hit the United States in at least 50 years does have one benefit: it has created the smallest "dead zone" in the Gulf of Mexico in years, says a Texas A&M University researcher who has just returned from gulf waters.

Oceanography professor Steve DiMarco, one of the world's leading authorities on the dead zone, says he and other Texas A&M researchers and graduate students analyzed the Gulf Aug. 15-21 and covered more than 1,200 miles of cruise track, from Texas to Louisiana. The team found no hypoxia off the Texas coast while only finding hypoxia near the Mississippi River delta on the Louisiana coast.

"We had to really hunt to find any hypoxia at all and Texas had none," he explains. "The most severe hypoxia levels were found near Terrabonne Bay and Barataria Bay off the coast of southeast Louisiana.

"In all, we found about 1,580 square miles of hypoxia compared to about 3,400 square miles in August 2011. What has happened is that the drought has caused very little fresh-water runoff and nutrient load into the Gulf, and that means a smaller region for marine life to be impacted."

...DiMarco says the size of the dead zone off coastal Louisiana has been routinely monitored for about 25 years. Previous research has also shown that nitrogen levels in the Gulf related to human activities have tripled over the past 50 years. During the past five years, the dead zone has averaged about 5,700 square miles and has reached as high as 9,400 square miles....

The Mississippi Delta in 1899, via Popular Science

Midwest drought brings fourth smallest Gulf of Mexico 'Dead Zone' since 1985

A little ironic good cheer from NOAA: NOAA-supported scientists have found the size of this year’s Gulf of Mexico oxygen-free ‘dead zone’ to be the fourth smallest since mapping of the annual hypoxic, or oxygen-free area began in 1985. Measuring approximately 2,889 square miles, the 2012 area is slightly larger than Delaware.

The survey also found a patchy distribution of hypoxia across the Gulf differing from any previously recorded. This is in stark contrast to last year, when flood conditions, carrying large amounts of nutrients, resulted in a dead zone measuring 6,770 square miles, an area of the state of New Jersey. The last time the dead zone was this small was in 2000 when it measured 1,696 square miles, an area slightly smaller than Delaware.

“The smaller area was expected because of drought conditions and the fact that nutrient output into the Gulf this spring approached near the 80-year record low,” said Nancy Rabalais, Ph.D., executive director of the Louisiana Universities Marine Consortium (LUMCON) who led the survey cruise. “What wasn’t expected was how the scattered distribution of hypoxia areas differed from any others documented in the past. Confirmed, however, is the strong relationship between the size of the hypoxic zone and the amount of fresh water and nutrients carried to the Gulf by the Mississippi River.”

The smallest recorded dead zone to date measured 15 square miles in 1988. The largest dead zone, also called a hypoxic zone, measured to date occurred in 2002 encompassing more than 8,400 square miles. The average size of the dead zone over the past five years has been 5,684 square miles, more than twice the 1,900 square mile goal set by the Gulf of Mexico/Mississippi River Watershed Nutrient Task Force.

Hypoxia is fueled by nutrient runoff from agricultural and other human activities in the Mississippi River watershed, which stimulates an overgrowth of algae that sinks, decomposes and consumes most of the life-giving oxygen supply in bottom waters.

The hypoxic zone off the coast of Louisiana and Texas forms each summer and threatens valuable commercial and recreational Gulf fisheries. In 2010, the dockside value of commercial fisheries in the Gulf was $639 million. More than 4.6 million recreational fishers took an estimated 22 million fishing trips in 2010, further contributing to the Gulf economy."...

NASA image of sediment and runoff in the Gulf of Mexico

What is your nitrogen footprint?

N-Print.org is a website focused on one of the main concerns of this website -- nitrogen pollution. They also have a nitrogen calculator! Worth a look: The human creation of reactive nitrogen (all N species except N2) by food and energy production has profound beneficial and detrimental impacts on people and the environment (1).  Agricultural uses, including both food production and consumption, contribute the most reactive nitrogen to the environment.  The main beneficial impact of the agricultural use of reactive nitrogen is the food produced by nitrogen fertilizer and human-enhanced biological nitrogen fixation.  These two processes provide the N to sustain about half of the world’s population (2).  The detrimental impacts result because a large fraction of the N used in food and biofuel production, and all of the N used in non-biofuel (i.e. non-agricultural) energy production, are lost to the environment.  Of the N used to produce food, about 80% is lost before consumption, and the remainder is lost after consumption as human waste.

Once lost to the environment, this nitrogen moves through the Earth’s atmosphere, forests, grasslands and waters causing a cascade of environmental changes that negatively impact both people and ecosystems.  These changes include smog, acid rain, forest dieback, coastal ‘dead zones’, biodiversity loss, stratospheric ozone depletion and an enhanced greenhouse effect (3).

The human influences on both the nitrogen and carbon cycles of the Earth are important to understand and to manage.  Over the past decade, great progress has been made in communicating to the public the role that their actions have on the carbon cycle and the environment.  For two reasons this is not the case with nitrogen.  First, there has been less scientific focus on nitrogen.  Second is the challenge in communicating to the public the complexities of nitrogen’s interactions with the environment.  One way to address the latter is through a nitrogen footprint model: N-Calculator....

A 42 foot Caterpillar Lexion combine harvester unloading wheat to an auger wagon pulled by a tracked Caterpillar Challenger tractor on the move near Pallamallawa, New South Wales, Australia. Shot by Cyron Ray Macey, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Expanding dead zones are shrinking tropical blue marlin habitat

Science Daily: The science behind counting fish in the ocean to measure their abundance has never been simple. A new scientific paper authored by NOAA Fisheries biologist Eric Prince, Ph.D., and eight other scientists shows that expanding ocean dead zones -- driven by climate change -- have added a new wrinkle to that science.

In the December 4 paper published in the scientific journal Nature Climate Change, these scientists sound an alarm that expanding ocean dead zones are shrinking the habitat for high value fish such as marlins in the tropical northeast Atlantic Ocean. As dead zones expand, marlins, other billfish and tunas move into surface waters where they are more vulnerable to fishing. Dead zones are areas in the ocean where oxygen levels are so low that creatures cannot survive over the long term.

"By combining the disciplines of oceanography and fishery biology, we are getting a much clearer picture of how climate driven dead zones are shrinking the habitat for some of the world's most valuable fish to commercial and recreational fishermen," Prince said. "With a clearer picture, we will be able to make better management decisions for the long-term health of these species and their ecosystems."

...Blue marlins and many other billfish are high energy fish that need large amounts of dissolved oxygen. By comparing the movement of the blue marlins and the location of low-oxygen areas, the scientists show that blue marlins venture deeper when dissolved oxygen levels are higher and remain in shallower surface waters when low dissolved oxygen areas encroach on their habitat from below.

"The shrinking of habitat due to expanding dead zones needs to be taken into account in scientific stock assessments and management decisions for tropical pelagic billfish and tuna," said Prince. "Without taking it into account, stock assessments could be providing false signals that stocks are healthy, when in fact they are not, thus allowing overfishing that further depletes these fish stocks and threatens the sustainability of our fisheries."...

Atlantic blue marlin, image from NOAA