Coastal Seas & Marine Food Web Important for Carbon Sink

Note how carbon is fixed in the ocean, in two ways:

1) by the 'physical pump' (the balance between concentrations of CO2 in the atmosphere and seawater), and

2) by photosynthesis (growing of algae) which is assimilated in the marine food web (into organisms and their carbon-containing waste products).

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North Sea Efficient Sink For Carbon Dioxide

http://www.sciencedaily.com/releases/2005/10/051011065902.htm

ScienceDaily (Oct. 12, 2005) -

A relatively large number of algae grow in the North Sea. These form the basis for a much richer food chain than that found in the Atlantic Ocean. Dutch-sponsored researcher Yann Bozec calculated that coastal seas such as the North Sea remove about three times as much carbon dioxide from the atmosphere than would be expected on the basis of their small surface area.

The measured annual increase in the concentration of carbon dioxide (CO2) in the atmosphere is only 60 percent of the annual emissions from fossil fuels. The other 40 percent is absorbed by the seas and oceans. Yann Bozec investigated how the North Sea fulfils this task.

Up until now, little was known about the concentrations and transport cycle of CO2 in the North Sea. This lack of data was rectified with four expeditions, each of one-month duration, with the oceanographic research vessel 'Pelagia' from the Royal Netherlands Institute for Sea Research (NIOZ). Per expedition the researchers made a vertical water profile at 97 locations. Travelling between locations they also measured the levels of CO2, nutrients (phosphate, nitrogen and silicate), and the amount of algal growth. This resulted in the most extensive and accurate data set ever for a coastal sea.

Bozec used these data to calculate how much carbon dioxide the North Sea absorbs from the atmosphere each year and then stores in the deep North Atlantic Ocean. This storage capacity was found to be almost three times as high as the average for all of the world's seas. When the data over the entire North Sea were pooled, this gave an annual net uptake of carbon dioxide of no less than 8.5 million tonnes of carbon per year. If this performance is theoretically extrapolated to all of the world's coastal seas - of which the North Sea constitutes just 2 percent - then these would together account for about 20 percent of the carbon dioxide uptake for all of world's seas, even though they only account for 7 percent of the sea surface. Therefore coastal seas absorb CO2 far more efficiently than open oceans.

Seawater can absorb carbon dioxide in two different ways. The 'physical pump' works as a result of the CO2 concentration in the atmosphere being higher than that in the seawater. As nature always tries to restore the balance, carbon dioxide flows from the atmosphere into the surface of the seawater. In the winter, the surface water in the cold polar seas cools down and becomes slightly heavier. As a result of this it sinks under its own weight into the deep sea.

The second way is by algae fixing carbon dioxide under the influence of sunlight (photosynthesis). This mechanism is important in the North Sea. Algae grow in the surface water and form their cell material by assimilating carbon dioxide from the seawater. This reduces the carbon dioxide concentration in the seawater thereby allowing more carbon dioxide to be absorbed from the atmosphere. The algae are further assimilated in the entire food web. As a result of this water that flows out of the North Sea is much richer in organisms (and carbon-containing waste products from these) than the inflowing, blue oceanic water.

Yann Bozec's research was funded by NWO.

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Turning the tide on global warming (salt marshes & carbon)

http://www.mcgill.ca/reporter/36/15/tide/

Sara Strawczynski, Spark Writer | Geography professor Gail Chmura has made a career of playing in mud. Chmura studies salt marshes, the transitional zone between land and ocean. Salt marshes filter pollutants, buffer coasts from flooding and provide habitats for waterfowl and fish. Chmura's latest research suggests that salt marshes also function as a carbon sink -- an area that removes carbon dioxide from the atmosphere, thereby slowing global warming.

Professor Gail Chmura, Department of Geography
Claudio Calligaris

"The global significance of salt marshes is often overlooked because they comprise just a fraction of the Earth's surface, and relative to other ecosystems like tropical mangrove swamps, they host few species," explained Chmura. These temperate wetlands flood with salt water at high tide but are dry at low tide. Rising sea levels for over two centuries have created bigger tides that flood further inland, expanding salt marshes. As their area increases, so does their environmental importance.

You can see the thickness of the salt marsh soil in this photo of an exposed marsh, submerged at high tide. Chmura placed her knapsack there for scale. There are no rocks in the marshes, the ones here were once part of a road bed. Gail Chmura

Two distinct characteristics make salt marshes efficient carbon sinks. First, salt marshes accumulate soil at a remarkable rate. "They can grow in depth by up to three millimeters a year because the tides constantly deposit sediments in the marsh," said Chmura. "Forest soil might not accumulate that depth for a century." Plants and microscopic organisms living in salt marshes can get buried under newly deposited sediments. The carbon contained within these organisms gets trapped in the salt marsh and is prevented from escaping into the atmosphere, where it might act as a greenhouse gas and contribute to global warming.

A second feature that makes salt marshes efficient carbon sinks is that bacteria living in salt marshes do not emit methane. Bacteria are nature's recyclers -- they decompose organic material and release the contents into the environment. In certain conditions bacteria produce methane as a decomposition product; released into the atmosphere, this carbon-based gas might contribute to global warming. Bacteria living in salt marshes do not produce methane, perhaps because the sulfide present in salt marshes is toxic to methane producers. Alternatively, bacteria that subsist on sulfide might outcompete methane producers within the marsh.

Much of Chmura's research is based at the Huntsman Science Centre, a McGill-affiliated field station at the Bay of Fundy on Canada's East coast. Famous for its world-record high tides, the Bay of Fundy also contains salt marshes where Chmura measures sedimentation rates. "We bury metal markers on the marsh and cover the marsh surface with a layer of white clay. We come back after a year or two to measure how much sediment has accumulated" she explained. "The fun part is locating the markers we left behind. We get to walk around the marsh with a metal detector because they are completely covered in mud." Once located, the depth of accumulated soil at each marker site is documented and samples are obtained using a coring device that preserves mud's vertical profile. Back at Chmura's McGill lab, samples are tested for carbon content and the rate of carbon accumulation is calculated.

An added angle to Chmura's research is that humans have affected salt marshes to varying degrees over time. An estimated 85 percent of the salt marshes in the Bay of Fundy have been altered by humans. Starting with the Acadians in the 17th century, salt marshes were dammed and dyked to create agricultural land. Over time, many of these structures fell into disrepair, allowing marshes to flood again, though not always to the same extent as the original marsh. Chmura explained that human alteration of Atlantic salt marshes has created a giant natural experiment. "The question is to determine how each salt marsh, given its unique history and its current use, is able to accumulate carbon and perform other ecosystem functions like providing habitat for fishes and birds." In order to compare the various marshes, Chmura must piece together each marsh's muddy history. She uses old documents, aerial photographs and abandoned structures on salt marshes to unravel the human impact at each site.

Low tide at Wood Point Marsh, New Brunswick. Here McGill gratuate student Marie Graf researches grass production and mud deposition. Gail Chmura

Chmura's work suggests that natural and human modified salt marshes do not perform identical ecosystem services. "Unfortunately, farmed salt marshes no longer act as carbon sinks," she explained. "They are not nearly as valuable as carbon stores because they do not flood, and so they cannot accumulate sediments brought in by the tides." Chmura estimates that if all of the Bay of Fundy's original salt marshes were allowed to flood tidally, or were "restored," the increased carbon stored would be the equivalent to around five percent of Canada's targeted reduction of greenhouse gas emissions pledged under the Kyoto Protocol; however, dyked salt marshes serve as farmland, residential areas and even crucial infrastructure like the Trans-Canada Highway. Chmura recognizes that reverting them all back to flooding salt marshes is unrealistic. Still, she hopes that future coastal developments will consider the important ecological services that salt marshes perform.

McGill's SPARK program (Students Promoting Awareness of Research Knowledge) is funded by NSERC and run by the Faculty of Education, VP Research Office and the University Relations Office. See www.spark.mcgill.ca for more information and articles.

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Climate Change in Wetland Areas: Carbon Cycle Implications

http://www.usgcrp.gov/usgcrp/Library/nationalassessment/newsletter/1999.08/Wet.html

Climate Change in Wetland Areas Part II: Carbon Cycle Implications
From Acclimations, July-August 1999
Newsletter of the US National Assessment of
the Potential Consequences of Climate Variability and Change

By Jon Kusler, Institute for Wetland Science and Public Policy

Wetlands affect the levels of atmospheric carbon in two ways: First, many wetlands, particularly boreal and tropical peatlands, are carbon reservoirs. Carbon is contained in the standing crops of trees and other vegetation and in litter, peats, organic soils and sediments which have been built up, in some instances, over thousands of years. The magnitude of storage depends upon wetland type and size, vegetation, the depth of wetland soils, ground water levels, nutrient levels, pH and other factors discussed below. These carbon reservoirs may supply large amounts of carbon to the atmosphere if water levels are lowered or land management practices result in oxidation of soils. Second, many wetlands also continue to sequester carbon from the atmosphere through photosynthesis by wetland plants; many also act as sediment traps for carbon-rich sediments from watershed sources. However, wetlands also simultaneously release carbon as carbon dioxide, dissolved carbon, and methane. Deposited sediments are, in some instances, dislodged during floods and hurricanes. The net carbon sequestering versus carbon release roles of wetlands are complex and change over time although net, gradual sequestration occurs over time for peatlands and certain other types of wetlands. Land use practices also affect sequestering.

Wetlands as Carbon Reservoirs

In carrying out photosynthesis, wetland trees and other plants convert atmospheric carbon dioxide into biomass. Carbon may be temporarily stored in wetlands as trees and plants and the living animals which feed upon them, and detritus including fallen trees and plants and the animals which feed upon them.

Carbon may stored in the longer term in organic-rich soils, peats, and various forms of coal, shale, sandstone, and other sediments. It is long term storage that makes some wetlands effective as carbon reservoirs. Wetlands often provide longer term carbon storage than other ecosystems systems because decompositional processes are hindered by the saturated conditions, high acidity (bogs), and low temperatures (tundra). Many organic "flats" wetlands are underlain by deep layers of peat; permafrost wetlands may be underlain by more than a meter of organic rich
soil; and it is not uncommon to find ten or more meters of unconsolidated organic matter in peat lands. Significant quantities of carbon from both wetland and nonwetland sources may also be trapped and stored in wetland sediments.

The long-term effectiveness of some wetlands in storing carbon is demonstrated by the extensive coal deposits throughout the world. These were formed in wetland or wetland-like conditions, in many instances hundreds of millions of years ago.

Like wetland forests, upland forests sequester carbon in standing vegetation and to a lesser extent in debris and the upper layers of the soil. However, long storage in soils is often limited due to rapid decompositional processes and re-release to the atmosphere. Rapid decomposition and re-release also occurs in some types of wetlands such as rice paddies.

The total amount of carbon in wetland standing vegetation, debris, peats and other soils is large, and it has been estimated that wetlands hold 35% of the total terrestrial carbon. Drainage of peatlands, tundra, and other wetlands acting as carbon reservoirs results in oxidation of the organic matter, releasing it to the atmosphere as CO2, methane, and other greenhouse gases. Conversely, enhancement, restoration or creation of certain wetlands may provide important additional carbon sinks.

Wetlands as Active Carbon Sinks (Sequestration)

Photosynthesis by wetland plants converts atmospheric CO2 into biomass. Wetlands are, therefore, net carbon sinks if the rate of plant production exceeds the rate of decomposition for fallen trees, litter, and wetland soils (e.g., peats) and net export through release of gases or water transport of dissolved carbon or sediments. Wetlands often store more carbon than other ecosystems despite their low productivity due to low decompostion rates. In addition, wetlands may act also as net carbon sinks if they trap carbon-rich sediment from upland sources and such accumulation exceeds losses. Many riverine, estuarine, coastal and estuarine wetlands trap large quantities of sediment from natural and anthropogenic watershed sources.

Rates of photosynthesis in wetlands, of course, vary. Some wetlands (e.g., coastal flats, playas) have little vegetation with resulting limited production of plant biomass; some (e.g., salt marshes, tropical forests) have much vegetation and high rates of production. Trees and other vegetation grow quickly in tropical and temperate wetlands with ample sunlight, nutrients, water and warm temperatures. In contrast, the growth of trees and other vegetation is slow for high latitude wetlands (e.g., peatlands) with less sun, nutrients, and water and colder temperatures.

Rates of decomposition also vary and fluctuate over time, depending upon a variety of interrelated factors such as temperature, water levels, hydroperiod, flow of water and nutrients. In addition, removal of carbon by physical processes may occur quickly in some wetlands and very slowly in others. For example, litter, peat and carbon rich sediments may be quickly removed from some coastal wetlands by frequent coastal storms; riverine flood flows may scour some riverine wetlands. In contrast, organic mater in bogs may remain undisturbed for hundreds or thousands of years (e.g. bogs) in others.

Research on peat lands indicates that photosynthesis and decompositional processes are complex and fluctuate in a specific setting, depending upon ground water levels, temperature, substrate availability, nutrient levels, methanogene population and other factors. Research suggests that, overall, peatlands are net carbon sinks. However, releases of carbon dioxide and methane may exceed photosynthesis in some circumstances. In addition, peat lands may convert carbon dioxide to methane-a more active atmospheric gas. It has been suggested that wetlands are a source of 15% to 20% of atmospheric methane.

Processes vary at different levels with a peat deposit. The lower levels of peat (catotelm) produce larger amounts of methane while the upper levels (acrotelm) produce carbon dioxide and at least partially oxidize methane released from the lower levels. The output of methane is determined by the production of methane by methanogenic bacteria and its removal by methanotrophic bacteria. Studies suggest that if the water levels are lowered in the upper levels due to drainage, decreased precipitation, or increased evaporation and transpiration, carbon dioxide and methane production may exceed sequestration. However, this may not continue once the upper levels of peat are oxidized to the level of the new water table.

Impact of Climate Change on Wetland Carbon Sequestering

Climate change will likely affect the ability of wetlands to sequester carbon, but the results will vary and are difficult to predict. Increased CO2 in the atmosphere will result in increased plant growth in most if not all wetlands, and the potential for increased carbon sequestration will increase under certain circumstances. Increased rainfall may also result in increased sediment deposition in some wetlands. Other the other hand, increased temperatures may result in decreased ground and surface water levels for many wetlands due to increased evapotranspiration where precipitation decreases, remains steady, or only slightly increases. Decreased ground and surface water levels and increased temperatures may result in increased decomposition. The carbon storage and sequestering role of peatlands could also be reduced by the melting of permafrost. Certainly, responses will be complex. Eville Gorham wrote in 1991 that, "given the diversity of possible responses by boreal and subartic peatlands to climatic warming, it is impossible at present to predict their future contributions to the global carbon cycle" - and others have recently endorsed Gorham's conclusion.

Management Strategies for Protecting and/or Enhancing Carbon Reserves and Wetland Carbon Sequestering Capabilities

A variety of strategies are available to protect and or enhance carbon reserves and wetland carbon sequestering. Some would be compatible with broader biodiversity protection goals and other goals to protect wetland functions; others would not. Some strategies include:

• Protect natural wetlands systems.
• Conduct regional inventories and prepare management plans for wetlands of greatest importance as carbon reserves and for carbon sequestering.
• Control fires.
• Protect low flows and residual water.
• Install water control structures.
• Plant trees, other vegetation.
• Restore, enhance, and create wetlands.

Conclusions and Recommendations

There is broad agreement that certain types of wetlands contain large historic, reservoirs of carbon in above ground biomass, litter, peats, soils and sediments. There is also agreement that land management practices such as drainage may release at least a portion of the carbon. However, accurate estimates are not available for total carbon reserves in wetlands the U.S. or other countries. And, the impacts of various land management practices such as forestry upon such reservoirs are also only partially known.

Similarly, there is broad agreement that wetland plants continue to convert atmospheric carbon into biomass and carbon-rich sediments continue to be deposited in wetlands. Net carbon sequestration occurs as long as rates of conversion exceed decomposition and external transport of materials from wetlands. However, it is difficult to evaluate the net carbon sequestering role of wetlands because decomposition of organic matter, methanogenisis and sediment fluxes are extremely complex and there are gaps in scientific knowledge.

What is needed to better evaluate generically and in specific settings the roles of wetlands as carbon reservoirs and for carbon sequestering and to guide protection, enhancement, restoration or creation efforts. A combination of literature surveys, scientific consensus-building measures (workshops), field measures and laboratory studies are needed. Some priority topics for such evaluation efforts include: evaluating wetlands as carbon reservoirs; estimating sequestration rates in wetlands; and enhancing, restoring and creating wetlands.

For more information, contact:

Jon Kusler, Director, Association of State Wetland Managers, P.O. Box 269, Berne, NY 12023-9746 (518-872-1804). 

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Coastal and marine carbon introduced in the UNFCCC

On 12 June 1992, 154 nations signed the UNFCCC, which upon ratification committed signatories' governments to reduce atmospheric concentrations of greenhouse gases with the goal of "preventing dangerous anthropogenic interference with Earth's climate system."

Blue carbon related text follows, highlighted for emphasis:

United Nations Framework Convention on Climate Change / May 9, 1992 / S. Treaty Doc No. 102-38, 1771 U.N.T.S. 107

UNFCCC ART 4(1)(d

“Aware of the role and importance in terrestrial and marine ecosystems of sinks and reservoirs of greenhouse gases” – PREAMBULA

“Promote sustainable management, and promote and cooperate in the conservation and enhancement, as appropriate, of sinks and reservoirs of all 11 greenhouse gases not controlled by the Montreal Protocol, including biomass, forests and oceans as well as other terrestrial, coastal and marine ecosystems” – ART 4.1(d)

“Cooperate in preparing for adaptation to the impacts of climate change; develop and elaborate appropriate and integrated plans for coastal zone management, water resources and agriculture, and for the protection and rehabilitation of areas, particularly in Africa, affected by drought and desertification, as well as floods; ART 4.1(e)

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