Marine Habitat Destruction: National Geographic

Habitat destruction occurs when the conditions necessary for plants and animals to survive are significantly compromised or eliminated. Most areas of the world's oceans are experiencing habitat loss. But coastal areas, with their closeness to human population centers, have suffered disproportionately and mainly from manmade stresses. Habitat loss here has far-reaching impacts on the entire ocean's biodiversity. These critical areas, which include estuaries, swamps, marshes, and wetlands, serve as breeding grounds or nurseries for nearly all marine species.

Causes of Ocean Habitat Loss

Humans and Mother Nature share blame in the destruction of ocean habitats, but not equally. Hurricanes and typhoons, storm surges, tsunamis and the like can cause massive, though usually temporary, disruptions in the life cycles of ocean plants and animals. Human activities, however, are significantly more impactful and persistent. Wetlands are dredged and filled in to accommodate urban, industrial, and agricultural development. Cities, factories, and farms create waste, pollution, and chemical effluent and runoff that can wreak havoc on reefs, sea grasses, birds, and fish. Inland dams decrease natural nutrient-rich runoff, cut off fish migration routes, and curb freshwater flow, increasing the salinity of coastal waters. Deforestation far from shore creates erosion, sending silt into shallow waters that can block the sunlight coral reefs need to thrive. Destructive fishing techniques like bottom trawling, dynamiting, and poisoning destroy habitats near shore as well as in the deep sea. Tourism brings millions of boaters, snorkelers, and scuba divers into direct contact with fragile wetland and reef ecosystems. Container ships and tankers can damage habitat with their hulls and anchors. Spills of crude oil and other substances kill thousands of birds and fish and leave a toxic environment that can persist for years.

Climate Change
Perhaps the most devastating of all habitat-altering agents, however, is climate change. Scientists are still coming to grips with the consequences that excessive atmospheric carbon dioxide and Earth's rapid warming are having on ecosystems. But there is ample evidence indicating that the oceans are bearing the brunt of these changes. As Earth's temperature rises, it is primarily the oceans that absorb the extra heat. Even small temperature changes can have far-reaching effects on the life cycles of marine animals from corals to whales.
In addition, warmer temperatures cause excess melting of ice caps and glaciers, raising sea levels and flooding estuaries. High levels of atmospheric carbon dioxide, caused mainly by the burning of fossil fuels, are absorbed by the oceans, where the gas dissolves into carbonic acid. This elevated acidity inhibits the ability of marine animals, including many plankton organisms, to create shells, disrupting life within the very foundation of the ocean's food web. Full article click here....

Climate Change Reducing Ocean's Carbon Dioxide Uptake, New Analysis Shows: ENN

As one of the planet's largest single carbon absorbers, the ocean takes up roughly one-third of all human carbon emissions, reducing atmospheric carbon dioxide and its associated global changes.

But whether the ocean can continue mopping up human-produced carbon at the same rate is still up in the air. Previous studies on the topic have yielded conflicting results, says University of Wisconsin-Madison assistant professor Galen McKinley.
In a new analysis published online July 10 in Nature Geoscience, McKinley and her colleagues identify a likely source of many of those inconsistencies and provide some of the first observational evidence that climate change is negatively impacting the ocean carbon sink.

"The ocean is taking up less carbon because of the warming caused by the carbon in the atmosphere," says McKinley, an assistant professor of atmospheric and oceanic sciences and a member of the Center for Climatic Research in the Nelson Institute for Environmental Studies.

The analysis differs from previous studies in its scope across both time and space. One of the biggest challenges in asking how climate is affecting the ocean is simply a lack of data, McKinley says, with available information clustered along shipping lanes and other areas where scientists can take advantage of existing boat traffic. With a dearth of other sampling sites, many studies have simply extrapolated trends from limited areas to broader swaths of the ocean.

McKinley and colleagues at UW-Madison, the Lamont-Doherty Earth Observatory at Columbia University, and the Universite Pierre et Marie Curie in Paris expanded their analysis by combining existing data from a range of years (1981-2009), methodologies, and locations spanning most of the North Atlantic into a single time series for each of three large regions called gyres, defined by distinct physical and biological characteristics.

They found a high degree of natural variability that often masked longer-term patterns of change and could explain why previous conclusions have disagreed. They discovered that apparent trends in ocean carbon uptake are highly dependent on exactly when and where you look -- on the 10- to 15-year time scale, even overlapping time intervals sometimes suggested opposite effects.

"Because the ocean is so variable, we need at least 25 years' worth of data to really see the effect of carbon accumulation in the atmosphere," she says. "This is a big issue in many branches of climate science -- what is natural variability, and what is climate change?"

Working with nearly three decades of data, the researchers were able to cut through the variability and identify underlying trends in the surface CO2 throughout the North Atlantic.

During the past three decades, increases in atmospheric carbon dioxide have largely been matched by corresponding increases in dissolved carbon dioxide in the seawater. The gases equilibrate across the air-water interface, influenced by how much carbon is in the atmosphere and the ocean and how much carbon dioxide the water is able to hold as determined by its water chemistry.

But the researchers found that rising temperatures are slowing the carbon absorption across a large portion of the subtropical North Atlantic. Warmer water cannot hold as much carbon dioxide, so the ocean's carbon capacity is decreasing as it warms.

In watching for effects of increasing atmospheric carbon on the ocean's uptake, many people have looked for indications that the carbon content of the ocean is rising faster than that of the atmosphere, McKinley says. However, their new results show that the ocean sink could be weakening even without that visible sign.

"More likely what we're going to see is that the ocean will keep its equilibration but it doesn't have to take up as much carbon to do it because it's getting warmer at the same time," she says. "We are already seeing this in the North Atlantic subtropical gyre, and this is some of the first evidence for climate damping the ocean's ability to take up carbon from the atmosphere."

She stresses the need to improve available datasets and expand this type of analysis to other oceans, which are relatively less-studied than the North Atlantic, to continue to refine carbon uptake trends in different ocean regions. This information will be critical for decision-making, since any decrease in ocean uptake may require greater human efforts to control carbon dioxide levels in the atmosphere.

McKinley's work on the project was supported by the National Aeronautics and Space Administration.