July 15, 2004
The Sea in the Middle of the Earth
Real Audio Report
This is Sarah Smith speaking to you from the Odyssey in Turkey.
The Odyssey crew is spending the summer months researching in the Mediterranean Sea. Having previously surveyed the vast areas of the Pacific and Indian Oceans, working in a semi-enclosed sea is quite a change.
Derived from the Latin medius (meaning "middle") and terra (meaning "earth"), Mediterranean literally means the 'sea in the middle of the earth'. Surrounded by three continents, Africa, Europe and Asia, this is how the Romans viewed the region when they first named the sea.
Over six million years ago during the Miocene period, the Mediterranean Sea dried up completely. Throughout a long, cooling phase, massive ice sheets formed, lowering the sea level below the height of the natural dam at Gibraltar, cutting the Mediterranean Sea off from the Atlantic Ocean, and the Black Sea off from the Mediterranean. Five million years ago, subsequent warming melted the glaciers to the point where the sea level rose, causing the Atlantic to spill back into the Mediterranean.
Today, the Mediterranean Sea is connected to the Indian Ocean by the man-made Suez Canal and to the Atlantic Ocean by the natural, narrow straits of Gibraltar. It is a tectonically active zone ravaged by severe earthquakes and numerous volcanoes. Geologic and geophysical studies indicate that the Mediterranean and Black Seas are remnants of a much larger expanse of ocean that is contracting along a subduction zone as the African continent drifts northward, slowly encroaching on Europe.
The intense blue coloring of the Mediterranean Sea is testimony to the absence of life - in fact, it is the most nutrient-depleted body of water of large size on earth. The relatively cold, Atlantic Ocean water of normal salinity is gradually transformed into warm, high-salinity Mediterranean Sea water. The increase in salinity counteracts the effects of rising temperature, so that the density of Mediterranean seawater increases eastward. This dense seawater sinks, filling the depths of the basin. The formation of dense water through the process of evaporation induces downwelling (sinking) of surface water, removing nutrients from the surface and preventing their renewal in the photic zone (the sunlit upper layer). Thus the productivity of phytoplankton is low and, in general, biota at the surface and in the deep sea is sparse. On average, it can take approximately 80-100 years for water in the Mediterranean Sea to cycle back westward into the Atlantic.
While many people are unaware of the presence of whales in the Mediterranean Sea, this region contains no fewer than twenty-one species of cetaceans - at least eight of these can be considered regular inhabitants. The Mediterranean is home to two of the largest whales - both sperm whales and fin whales - the second largest animal on the planet - are found here. Striped dolphins, bottlenose dolphins, short-beaked common dolphins, Risso's dolphins, long-finned pilot whales, and Cuvier's beaked whales are other species commonly sighted in this area. Occasionally, minke whales, Northern bottlenose whales, killer whales, false killer whales, harbour porpoises, Indo-Pacific hump-backed dolphins, and rough-toothed dolphins are seen here as well.
Over the years, there have been reported sightings or strandings of Sei whales, humpback whales, Northern right whales, dwarf sperm whales, Sowerby's beaked whales, and Blainville's beaked whales. Some of these sightings may have been individuals that strayed into the Mediterranean from the Atlantic Ocean through the Straits of Gibraltar or from the Red Sea through the Suez Canal. Despite the relatively small area of the Mediterranean Sea and its adjacency to a large human population, there is still much we don't know about the ecology of cetaceans in this area. There may even be undocumented species here.
The Mediterranean is surrounded by twenty nations. There is an inherent difficulty in getting so many different governments to cooperate in the management and protection of coastal and deep-sea resources. To address this problem in relation to cetacean management and protection, many of the nations in the Mediterranean basin are working together under ACCOBAMS - the Agreement on the Conservation of Cetaceans of the Black Sea, Mediterranean Sea, and Contiguous Atlantic Area. This agreement represents collaboration among policy-makers and scientists in the countries bordering the Mediterranean and Black Seas to protect the whales and dolphins found in this area. Ratified on June 1, 2001, this agreement was created to identify and address the threats to cetaceans and increase our knowledge of their ecology in the region. Each member state must implement a detailed conservation plan for the cetaceans in their waters. ACCOBAMS is affiliated with a number of research and non-governmental organizations. Ocean Alliance, with the R/V Odyssey, will be collaborating with a number of scientists working with these organizations.
Over 400 million people live in the surrounding region of the Mediterranean. Unlike some of the remote areas the Odyssey surveyed over the past four years of the expedition, this area is heavily affected by anthropogenic activity. All animals living in the Mediterranean are subject to a number of serious threats. Over-fishing is ubiquitous in the region with numerous species killed as bycatch - including whales and dolphins. Intense human activity means animals within the Mediterranean are at increased risk for collisions with vessels, disturbance by boat traffic and noise pollution, and habitat destruction. A large human population means increased pollution in the sea, both in the form of plastics and chemical pollution - the focus of our research in the Mediterranean.
The crew of the Odyssey is excited about researching in the Mediterranean Sea. The tissue samples we collect from sperm whales will reveal much about the accumulation of Persistent Organic Pollutants (POPs) in these animals and the health of the Mediterranean Sea as a whole. We are very interested to compare the results from samples collected in the Mediterranean Sea with those from other, less populated areas. We also hope to learn more about the distribution of sperm whales, their population size and structure. We anticipate our time in the Mediterranean to be some of the most important research for the Voyage of the Odyssey program and look forward to collaborating with scientists based in the region.
- Pinet, Paul R. Oceanography: An Introduction to the Planet Oceanus.
New York: West Publishing Company. 1992.
- Earle, Sylvia A. Atlas of the Ocean: The Deep Frontier.
Washington, DC: National Geographic Society. 2001.
- ACCOBAMS Website - www.accobams.org
Log written by Genevieve Johnson & Sarah Smith.