How has the ocean made life on land possible? Marine organisms produce over half of the oxygen that land animals currently need to breathe. In fact, that is where the plankton that provide the foundation of the ocean food web are most prolific.
The twilight zone is a part of the ocean to 3, feet below the surface, where little sunlight can reach. It is deep and dark and cold, and the pressures there are enormous. Some countries are gearing up to exploit twilight zone fisheries, with unknown impacts for marine ecosystems and global climate. Scientists and engineers at Woods Hole Oceanographic Institution are poised to explore and investigate this hidden frontier.
Scientists usually divide plankton into three groups that align with major divisions of life. The plant-like organisms are phytoplankton from…. The man responsible was the late John Martin, former director of the Moss Landing Marine Laboratory, who discovered that sprinkling iron dust in the right ocean waters could trigger plankton blooms the size of a small city. He uses techniques that span isotope geochemistry, next generation DNA sequencing, and satellite tagging to study the ecology of a wide variety of ocean species.
He recently discovered that blue sharks use warm water ocean tunnels, or eddies, to dive to the ocean twilight zone, where they forage in nutrient-rich waters hundreds of meters down.
Born in New Zealand, Simon received his B. With much of his work in the South Pacific and Caribbean, Simon has been on many cruises, logging 1, hours of scuba diving and hours in tropical environs. He has been a scientist at Woods Hole Oceanographic Institution since Gregory Skomal is an accomplished marine biologist, underwater explorer, photographer, and author.
He has been a fisheries scientist with the Massachusetts Division of Marine Fisheries since and currently heads up the Massachusetts Shark Research Program. For more than 30 years, Greg has been actively involved in the study of life history, ecology, and physiology of sharks.
His shark research has spanned the globe from the frigid waters of the Arctic Circle to coral reefs in the tropical Central Pacific. Much of his current research centers on the use of acoustic telemetry and satellite-based tagging technology to study the ecology and behavior of sharks. He has written dozens of scientific research papers and has appeared in a number of film and television documentaries, including programs for National Geographic, Discovery Channel, BBC, and numerous television networks.
His most recent book, The Shark Handbook, is a must buy for all shark enthusiasts. Robert D. He served in the U. Navy for more than 30 years and continues to work with the Office of Naval Research. A pioneer in the development of deep-sea submersibles and remotely operated vehicle systems, he has taken part in more than deep-sea expeditions.
In , he discovered the RMS Titanic , and has succeeded in tracking down numerous other significant shipwrecks, including the German battleship Bismarck , the lost fleet of Guadalcanal, the U. He eventually made a crucial conceptual leap, proposing in that phytoplankton not only reflected the chemical composition of the deep ocean, but created it 1.
He suggested that as phytoplankton and the animals that ate them died and sank to the bottom, along with those animals' faecal matter, microorganisms in the deep sea broke that material down into its chemical constituents, creating sea water with the same proportions of nitrogen and phosphorus. The sea is not the only place where microorganisms shape the environment.
Since Redfield's time, scientists have discovered that microorganisms also helped shape the chemical composition of our planet's air and land. Most dramatically, trillions of phytoplankton created the planet's breathable, oxygen-rich atmosphere.
By analysing a variety of minerals in rocks of known age, geologists discovered that for the first half of Earth's 4. They found rocks containing fossilized cyanobacteria, or blue-green algae, whose present-day cousins perform a type of photosynthesis that uses the Sun's energy to split water into hydrogen and oxygen. There were no land plants to produce oxygen until almost 2 billion years after atmospheric oxygen levels first rose. It was the oxygen these photosynthetic microorganisms that created our oxygen-rich atmosphere.
Today, different groups of microorganisms, especially in the ocean, recycle waste produced by other microorganisms and use it to power global cycles of the elements most essential to life. Different microorganisms convert amino acids and other organic nitrogen compounds to nitrogen-containing gases, returning them to the atmosphere. And others help drive the recycling of different elements essential for life, including iron, sulphur and phosphorus. Phytoplankton provide organic matter for the organisms that comprise the vast majority of marine life.
They do this by consuming carbon dioxide that would otherwise dissolve in the sea water and make it more acidic. The organisms provide organic matter for the vast majority of the marine food chain. Removing carbon dioxide from water also allows more of it to diffuse in from the air, lowering atmospheric levels of the gas.
In these ways, phytoplankton are crucial to the global carbon cycle, the circular path by which carbon atoms travel from the atmosphere to the biosphere, to the land and then back to the ocean. How do we know how individual elements such as carbon move through our vast oceans and the atmosphere? The first clues came in , when a Danish ecologist named Einar Steeman-Nielsen introduced an important technique that would shed light on how carbon cycles in the ocean.
It enabled scientists to measure an ocean ecosystem's primary productivity — the amount of organic matter that phytoplankton incorporate into their bodies through photosynthesis after meeting their own energy needs. To make this measurement, Steeman-Nielsen added bicarbonate containing a radioactive isotope of carbon called carbon to samples of sea water.
When he exposed the samples to sunlight, the phytoplankton in the samples incorporated carbon into their tissues. By isolating the phytoplankton and measuring the radio-active decay of carbon in their cells, scientists could calculate the total amount of carbon dioxide fixed into organic matter.
Phytoplankton are the foundation of the ocean food web, providing organic matter for virtually all other marine creatures. Their primary productivity limits the growth of crustaceans, fish, sharks, porpoises and other marine creatures, just as the primary productivity of land plants limits the growth of elephants, giraffes and monkeys.
By determining the productivity of phytoplankton, marine scientists can also determine how much carbon dioxide is being taken from the atmosphere. For three decades, oceanographers used Steeman-Nielsen's carbon technique to answer an important ecological question: how much organic matter do phytoplankton produce globally? The carbon technique helped them measure how quickly phytoplankton were fixing carbon at thousands of sites across the globe, but the estimates of primary productivity they generated were far too low.
They calculated that if the numbers were correct, the average phytoplankton in the ocean would take between 16 and 20 days to divide, but that didn't make sense to the biological oceanographers who were familiar with these organisms. The phytoplankton should have been growing much faster. Something was clearly wrong, but what?
In the late s, chemist John Martin at the Moss Landing Marine Laboratory in California realized that the discrepancy occurred because of contamination.
Most of the seawater samples taken over the previous three decades had been inadvertently contaminated by heavy metals from the black rubber O-rings used to seal the sampling devices.
Rubber products are chemically treated during manufacture to give them the correct mechanical properties. This process, called vulcanization, involves treating them with sulphur containing some zinc and tiny amounts of lead.
These metals leached from the O-rings and other components into the seawater samples, where they poisoned the phytoplankton. As a result, the measurements of primary production over three decades were compromised, causing scientists to seriously underestimate the importance of the world's oceans for the global carbon cycle.
Martin and others developed new sampling techniques that kept samples as free as possible of lead and other trace metals, allowing more accurate measurements of phytoplankton's primary productivity. But there was still a problem. Even with thousands of measurements of primary productivity in the world's oceans, most of the ocean was still not being observed in any given month or year.
Mathematical methods could extrapolate from the primary productivity data to help fill in the gaps, but not well enough. No one really knew how much carbon the world's phytoplankton pulled from the water around them. Obtaining reliable estimates of the ocean's primary productivity required a different approach.
The CZCS took advantage of the fact that oxygen-producing photosynthesis only occurs in organisms that have a pigment called chlorophyll a. This pigment enables the phytoplankton to absorb blue light, which would otherwise be scattered by the sea water. The more phytoplankton there are in an area of ocean, the more chlorophyll a there is and the darker the area appears from space.
Oceanographers first calibrated the colour of the ocean in CZCS photographs with measures of primary productivity such as that developed by Steeman-Nielsen, and then used the colour measurements to obtain better mathematical estimates of phytoplankton productivity than were previously available. The results from several groups of scientists showed that the world's phytoplankton incorporated a stunning 45—50 billion tonnes of inorganic carbon into their cells, twice the highest previous estimate.
The importance of phytoplankton in converting carbon dioxide into plant and animal tissue became clear. How did phytoplankton's contribution compare with that of land plants? We found that land plants incorporated 52 billion tonnes of inorganic carbon each year, just half as much as ecologists had previously estimated.
The ocean, with its enormity and mystery, has ever been part of human consciousness. As mystery gave way to mastery, whole bodies of custom, tradition and law arose defining the rights of the ships and mariners who plied the waters and of the States on the rim of the oceans.
Attempts have been made through the years to regulate the use of the oceans in a single convention that is acceptable to all nations. This effort finally culminated with the adoption of the United Nations Convention on the Law of the Sea, which has gained nearly universal acceptance since its entry into force on 16 November The United Nations Convention on the Law of the Sea provides, for the first time, a universal legal framework for the rational management of marine resources and their conservation for future generations.
Rarely has such radical change been achieved peacefully, by consensus of the world community.
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