Archive for July, 2009

Ocean dead zones cause for concern

July 14, 2009

By Stuart Wakeham

Professor, Skidaway Institute of Oceanography

When you look at the activities in the waters of Coastal Georgia and you see an ocean seemingly teeming with life, it is difficult to comprehend that large sections of the world’s oceans are considered “dead zones.” These are areas of the oceans where low levels of dissolved oxygen have either killed or driven off most of the fish and shell fish sought by commercial and recreational fishermen.

Dr. Stuart Wakeham

Dr. Stuart Wakeham

Oxygen‑deprived areas of ocean around the world have spread exponentially since the 1960s. They now affect a total area of more than 95,000 square miles. Georgia’s waters may not be immune to the threat.

Dead zones are caused by both natural and man-made processes. It begins when excessive loads of nutrients are introduced to the water from sewage, storm runoff containing fertilizer and other sources. These nutrients promote the growth of microscopic marine algae called phytoplankton. When the phytoplankton die and decay, the process, if excessive, can consume much of the dissolved oxygen in the water. Oxygen deficit (hypoxia) occurs when dissolved oxygen in seawater falls below 0.2 mg of O2/liter.

Some dead zones occur naturally along the western boundaries of continents where nutrient-rich, cold water is occasionally upwelled from the deeper ocean. However, they also occur in areas where rivers deliver excess of nitrogen from farm fertilizers, sewage and emissions from vehicles and factories. The most infamous coastal dead zone is in the northern Gulf of Mexico, where the Mississippi River dumps fertilizer runoff from the Midwest.

Although not considered a dead zone, Georgia’s coastal waterways are showing discouraging signs. Skidaway Institute scientist Peter Verity has monitored local water conditions for more than 20 years and documented a steady decline in dissolved oxygen to the point where some areas approach hypoxic during the summer.

Dead zones strongly affect marine life and threaten fisheries. The expansion of dead zones may lead to diminished biodiversity and increase the distributions of organisms that have adapted to oxygen‑poor waters, such as jellyfish.  Motile animals such as fish might flee the suffocation of hypoxia, but slow moving or non-motile creatures that dwell on the bottom such as clams, lobsters and oysters, are less able to escape. The result is mass mortality due to low levels of dissolved oxygen.

Scientific studies suggest that in many areas of the oceans there is a small margin of safety against oxygen dropping to deadly levels. It is therefore of critical importance to develop a clear understanding of the functioning of oxygen‑deficient zones.

At Skidaway Institute, we have been studying how carbon cycles under conditions of low oxygen levels. This understanding is essential if we are to assess how coastal oxygen‑deficient zones occur and function as a result of man-made influences.

The need for a clear understanding of how dead zones develop and function is more pressing than ever as new research indicates global warming could aggravate the problem, leaving fish and other marine life in oxygen‑poor oceans for thousands of years to come if global warming continues unchecked.

Increases in the emissions of carbon dioxide could change rainfall patterns. In some areas, this could lead to increased levels of run‑off from rivers into the seas. While previous studies have established a link between climate change and dead zones, new computer simulations by Danish researchers, among others, suggest the dead zones could persist for millennia and lead to a considerable purge and restructuring of ocean life.

Dead zones currently make up less than two percent of the world’s ocean volume. The model predicts that global warming could cause dead zones to grow by a factor of ten or more by the year 2100.

In the worst‑case scenario, dead zones could encompass more than a fifth of the world’s oceans. The impact on global ecosystems will be substantial.

“Fishing trip”

July 13, 2009

Two of our professors, Marc Frischer and Gus Paffenhöffer and their research teams are taking the R/V Savannah out for a four-day “fishing trip.”

R/V Savannah

R/V Savannah

However, marlin and swordfish have nothing to fear from these guys. They are hunting the elusive doliolid (doe-lee-OH-lid). “What is a doliolid?” You may ask.

Doliolid

Doliolid

It is a tiny, not quite microscopic, gelatinous organism that looks a little like a beer barrel and occasionally “swarms” in the waters on the continental shelf. A single doliolid ranges in size from about the size of the period at the end of this sentence to about the size of the letter “o.”

Drs. Frischer and Paffenhöffer are working on a NSF grant funded project to find out more about these little creatures, especially what they eat and what eats them. Decreasing pH in the ocean could cause these little critters to proliferate. Right now, we know very little about how they live and where they fit in to the whole food-web scheme of things.

Pogo was right; the enemy is us

July 9, 2009

by Richard Jahnke

Professor Emeritus

Skidaway Institute of Oceanography

“Unlike plagues of the dark ages or contemporary diseases we do not yet understand, the modern plague of overpopulation is soluble by means we have discovered and with resources we possess. What is lacking is not sufficient knowledge of the solution but universal consciousness of the gravity of the problem and education of the billions who are its victims.” Martin Luther King, Jr., 1966.

In the midst of the ongoing debate over global climate change (aka: global warming), there is a gigantic ‘elephant in the room’ that no one wants to acknowledge. That figurative pachyderm is human population growth, an issue that may overwhelm any efforts by developed nations to reduce their greenhouse gas emissions.

Dr. Richard Jahnke

Dr. Richard Jahnke

Although many may wish to put their heads in the sand and pretend it isn’t happening, the science is quite clear – the earth is warming. On a year-to-year basis, the global average fluctuates, down a little for a year or two and then up a little for another few years. Observed on the short term, the data are very noisy, but when you step back and look at a larger picture, the trend becomes clear. Over the past 130 years, the upticks have surpassed the downticks. Even adjusting for a generous margin of error, the world is nearly a degree-Celsius warmer than it was when Ulysses Grant was president.

Most scientists agree that the increase in greenhouse gases such as carbon dioxide (CO2), methane and nitrous oxide are significant contributors to the warming trend. By analyzing gas bubbles trapped in Antarctic ice, scientists have been able to paint a picture of the Earth’s atmosphere going back 800,000 years. Until the 19th century, CO2 levels fluctuated roughly between 200 and 280 parts per million (ppm). However, over the past 150 years, CO2 levels have broken out of those limits and shot nearly straight up to approach 400 ppm.

All efforts to reduce greenhouse emissions may be for naught, if we ignore the ‘elephant’, population growth. Even if all rich nations cut back dramatically on their consumption and emission rates and live more simply, it will merely push the breaking point a little further into the future. As developing nations advance, their citizens justifiably strive to become more comfortable, to consume more – more energy and more resources. And there are a lot of citizens out there in developing countries.

Between 2000 and 2050, world population is expected to grow by nearly three billion people. Stabilizing or slowing the rate of greenhouse gas build-up in the atmosphere in the face of this increasing human pressure is a daunting challenge. Indeed, if the emission rate for every person on earth could be reduced by one third, that increase in population would balance the emission reduction, and atmospheric greenhouse gas concentrations would continue to rise at the present rate. Considering that approximately 30 percent of the heat-trapping effects are due to non-CO2 greenhouse gases like methane and nitrous oxide, which are released mostly through agricultural activities to feed the growing population, and the challenge of stabilizing emissions is even greater.

The most effective method of slowing population growth is education, and particularly the education and emancipation of young women and girls. This is a significant issue in the developing world where much of the future population growth is expected.

One important consideration overlooked by those in developed nations who object to the idea of limits on population is that without a decrease in worldwide population growth, all nations will become overpopulated, as desperate migrants from impoverished, crowded regions seek work in developed nations. More stringent immigration policies won’t stop desperate people.

As the comic strip character, Pogo, famously once said, “We have met the enemy and he is us.”  Ultimately, sustainability of the environment requires population stabilization. Until this is achieved, there is much that can and must be done. Small reductions in population growth provide major benefits and permit future generations more time to recognize their impact and adjust to changing earth conditions. Such achievements require, however, that we open the door for an honest dialog about population – the elephant that future generations need us to acknowledge.