They estimated that they found approximately species per km along the seabed they sampled. Extrapolations of this figure suggested that there may be 1 - 10 million macrofaunal species in the deep sea. What's more, some scientists argued that Grassle and Maciolek's estimates represented only a small part of the species diversity in the ocean depths. Dr John Lambshead of London's Natural History Museum pointed out that Grassle and Maciolek had not examined the smallest animals in sediments — the meiofauna — made up of tiny nematode worms, copepods and other animals.
These are at least an order of magnitude more diverse than the macrofauna, suggesting that as many as million species may inhabit the deep ocean. However, given that the latest approximation of the Earth's biodiversity is 10 million species in total, Lambshead's number appears to be an overestimate. Scientists have since realized that there are major problems with estimating the species richness of large areas of the deep sea based on local samples.
Today we understand that species diversity in the deep ocean is high, but we still don't know how many species live in the sediments of the continental slope and abyssal plains. We also don't understand the patterns of their horizontal distribution or the reasons for the parabolic pattern of species diversity as it relates to depth.
Evidence suggests, however, that the functioning of deep-sea ecosystems depends on a high diversity of animals — although exactly why remains open to conjecture. In , German scientist Alfred Wegener put forward his theory of continental drift to address many questions that engaged the geologists and biologists of his time. For example, why do the continents appear to fit together as though they had once been joined? Why are many of the large mountain ranges coastal? And, perhaps most intriguing, why do the rocks and fossil biotas combined plant and animal life on disconnected land masses appear to be so similar?
Wegener's theory provoked a major scientific controversy that raged for more than 50 years between "drifters" and "fixists. In the search for an alternate mechanism to explain continental drift, British geologist Arthur Holmes suggested that radioactive elements in the Earth were generating heat and causing convection currents that made the Earth's mantle fluid.
Holmes argued that the mantle would then rise up under the continents and split them apart, generating ocean basins and carrying the landmasses along on the horizontally-moving currents. Following World War II, scientific expeditions employing deep-sea cameras, continuously recording echo-sounders, deep-seismic profilers and magnetometers lent support to the arguments of Holmes and his fellow "drifters.
These ridges were characterized by fresh pillow lavas, sparse sediment cover, intense seismic activity and anomalously high heat flow. Scientists found geologically-synchronous magnetic reversals in the rocks of the ocean crust moving away from either side of the mid-ocean ridges.
Added to this was the fact that nowhere could scientists find sediments older than the Cretaceous in age. Together, these findings suggested that new oceanic crust was being formed along the mid-ocean ridges, while old oceanic plates are forced underneath continental plates and destroyed along the ocean trenches. By the late s, the bitter scientific debate between the "fixists" and the "drifters" was finally settled.
During the next decade, scientists investigating volcanic activity at mid-ocean ridges became interested in the associated phenomenon of hot springs in the deep sea. Anomalously high temperature readings over mid-ocean ridge axes led scientists to mount an expedition in to the 2. From the submersible Alvin, the scientists observed plumes of warm water rising from within the pillow lavas on the seabed.
Living amongst the pillows were dense communities of large vesicoyid clams, mussels, limpets and giant vestimentiferan tube worms Siboglinidae. Subsequent investigation confirmed that the giant tube worms, clams and mussels actually hosted symbiotic sulphur-oxidizing bacteria in their tissues. The discovery caused huge excitement in the scientific community. Here was life thriving in the deep sea, where primary production — the basis of the food web — was independent from the sun's energy. Furthermore, as scientists discovered additional vent communities and surveyed elsewhere in the mid-ocean ridge system, they found that environmental conditions were extreme, with high temperatures, acidic waters, hypoxia lack of oxygen and the presence of toxic chemicals the norm.
The implications of this were enormous and went well beyond the study of the ocean itself. First, it meant that life could exist elsewhere in our solar system in environments previously thought too extreme. Second, it widened the potential area for habitable planets around suns elsewhere in the universe. For example, the discovery in of the Lost City alkaline hydrothermal vents presented an environment that some scientists suggest is analogous to the conditions in which life evolved on Earth.
Subsequently, chemosynthesis has been discovered in many places in the ocean, including deep-sea hydrocarbon seeps, in large falls of organic matter such as whale carcasses, and from shallow-water sediments associated with, for example, seagrass beds. Over the past two decades, we've developed a much deeper understanding of the relationship between humankind and the natural world, including the Earth's oceans.
In Robert Costanza and his colleagues published a paper in Nature that estimated the economic value of the goods and services provided by global ecosystems.
Climate change and ocean acidification — both the result of our reliance on fossil fuels — are having more and more extreme impacts on ocean health. If need be, they can exceed the A4 size; however, they need to be properly folded in order to fit into the thesis body. Foreign applicants will be required to pass the TOEFL exam with a score of or greater, or equivalent score on computer administered tests. The curriculum and other requirements can accommodate students currently in the workforce. At the centre's simulated rock pool I thrived on the opportunity to share my enthusiasm for marine crustaceans and was rewarded by the excitement on the children's faces when the hermit crabs started fighting over a shell.
These goods and services were later grouped into supporting e. While this knowledge may have been intuitive for many people, Costanza's recasting of the environment in economic terms forced policymakers, industry leaders and others to recognize the importance of long-term environmental sustainability.
With the support of international agencies such as the World Bank, many countries are now implementing natural capital accounting procedures through legislation. The purpose of this is to help monitor and regulate the use and degradation of the environment and to ensure that the critical ecosystem goods and services underpinning economic activity and human well-being are not undermined.
Although it seems like a modern preoccupation, sustainability is actually a centuries-old challenge, particularly as it relates to marine environments. For example, there is evidence that aboriginal fisheries in ancient times may have overexploited marine species. Certainly by medieval times in Europe, a thriving market for fish, coupled with other developments like changing agricultural practices, forced species such as salmon and sturgeon into decline.
The Industrial Revolution led to an increase in hunting fish, seals and whales, thanks to the development of steam- and then oil-powered fishing vessels that employed increasingly sophisticated means of catching animals. Pelagic whaling began in the early 20th century; the development of explosive harpoons, the ability to process whales at sea, and the strong demand for margarine made from whale oil all contributed to dramatic rises in catches.
Dissertation binding worcester. Steven sievers dissertation key stage 1 leader personal statement. Essay on leave application. Monetary policy macroeconomics case study. Topics creative writing competition.
Essay on apj abdul kalam in words in hindi. Stephen hawking latest research paper pdf.
Bibliography for research paper example sample business plan for poultry project. Year 9 homework booklet english.
Format of essay writing. How to reference a book in essay. A pakistani wedding essay with outline. Essay on environment day pdf. Cover letter for it manager.
Christopher columbus annotated bibliography. Preparing a curriculum vitae cv. Example nursing student cover letter. Business plan administration department. Essay 2 paper 7th class. Channel island fox case study. Sample introduction case study. Afsa high school essay scholarship.
Homework for high school. Examples of a thesis statement in an argumentative essay. Manchmal hat es das Hotelpersonal auch nicht einfach wenn sich Touristen so benehmen.
Manchmal ist es schon echt kurios was so gechattet wird. Hier ein paar echt lustige Beispiele. Machmal richtig witzig und ab und zu auch zum Nachdenken anregend. Aber immer treffen sie genau ins Schwarze.