EXOTIC DIVE TOUR

SEAWATER fACTOR

Relative Weight
It is interesting to note that 1liter of air weighs .013N and 1liter of water weighs 10N, that is 770 times heavier than air. The relative weight of seawater depends on the density and temperature of the water. Density itself, though insignificantly, depends on temperature. That is why at 20ºC the density of the water is lower by .2% than it is at 4ºC. Pure distilled water has a relative weight of 1 at a temperature of 4ºC, that is, 1 cm3 of water weighs 1g. Seawater is heavier than fresh water by 2.5–3% because of the greater amount of salts dissolved in it; its relative weight is 1.025. It may be concluded that a diver weighs less in seawater than in fresh water. Relative weight is important for determining buoyancy.

Resistance

Just like any other liquid, water practically does not shrink. That is why its density almost does not change at different depths. At a pressure of 500at water shrinks by 1/47,000,000 of its volume. If it did not shrink at all, however, the sea level would rise by 30m. Water resistance is greatest in the surface layer. Therefore, less effort is needed for swimming in that layer.
Transparency The relative transparency of seawater is determined by the average depth, at which a white disc of a 30cm diameter is no longer seen. Greatest transparency has the Sargatian Sea (66.5m), second greatest transparency have the Syrian coasts of the Mediterranean Sea. Least transparent is the North Sea (the British Channel) – some 6.5–12m.
The heat capacity of seawater is 3134 times greater than that of air. Water has insignificant heat conductivity. That is why distribution of heat to greater depths is very slow and is mainly achieved through convection.
The highest temperature of water is registered to occur between 3 and 4 p.m., and the lowest – a couple of hours after sunrise. There are three temperature layers of seawater: surface layer (epilymnion), intermediate layer (metalymnion), and deepest layer (hypolymnion). The thickness of the former two layers varies with the weather, season, and currents. The temperature of the surface layer is almost constant, being between 19 and 25ºC in the summer. As the deepest layer begins, temperature drops by a few more degrees and it remains constant thereafter (7–9ºC). That is the temperature of sea depths and it does not depend on the season.

Water Motion

Water motion constitutes sea currents and waves. The reason for the formation of currents might be the different density of water, constant winds, etc. Ocean currents are usually caused by constant winds, whereas local ones are mainly due to the character of coastlines. According to he direction of their flow, currents can be classified as vertical or horizontal. There are three main types of waves: wind waves, standing waves, and seismic waves.

Wind

is the main reason for the formation of waves. The process of wave formation can be divide into different stages. When the speed of wind is less than 1m/s, air motion does not affect the surface of the water. If wind intensifies, these rows of waves become irregular and peaks appear, which are due to the different pressure at the front and at the back of the wave. At a greater speed of wind large waves are formed, running in parallel rows. Th largest waves reaching hundreds of meters continue even when the wind has ceased. They create the so-called dead drift.

Water and senses

Standing waves

are formed when the level of the water rises at one coast and in the same time drops at the other. A sudden decrease of atmospheric pressure at one of the coasts, appearance of strong wind or heavy rain can all be the causes for standing waves. The fluctuation of the sea level may reach 80cm, which is dangerous for vessels at the harbors.
Seismic waves are formed because of underwater earthquakes. A vessel that is nest the site of the earthquake experiences a hydraulic blow which is why old maps frequently contain non-existent reefs. Seismic waves are often present in the Hawaii region where they have the special name zunami. Such waves are formed in the Pacific Ocean, the Mediterranean, the Caribbean Sea, and the Malaya Archipelago as well. Sometimes, these waves reach the height of 35m and are dangerous not only for the ships but also for the native population because of their destructive power.
Waves change their form

when they reach shallow regions. When the depth becomes equal to the height of the wave, the water particles no longer move in a circle: their orbit becomes elliptical. The length of the waves decreases and the height increases. The front slope of the wave becomes vertical, the top is inclined forward, then it falls and eventually destroys the wave. This phenomenon is called a surf. Its force may reach up to 38 tonnes/m2.
Difficulties The change of water density, resulting from changes of temperature, salinity, and pressure has no practical importance to diving. Even though, water is a dense medium and creates significant difficulties for a diver’s movements. He or she cannot walk or turn as fast as in the air. While working under water, divers must choose positions and movements that create least resistance, e.g. walking sidewards being slightly bent forward. The use of tools is also hindered. For example, the use of a hammer is much more difficult under water than it is in the air. As a result, divers quickly get tired. That is why the work that is to be performed under water should be organized so as to facilitate the diver by minimizing unnecessary movements and providing possible help from the surface. Rapid currents additionally impede the accomplishment of underwater work. Mire, too, can create considerable difficulties for divers. Even the execution of simplest types of work becomes complicated and requires dexterity, resistance, and fitness. That is why rigorous physical preparation is crucial

Gas Presure Theory

First of all, we should point out that the pressure on a diver under water is the result of two separate forces which act simultaneously upon him or her. These are:

1. The weight of the water

2. The weight of the atmosphere over the surface of the water.
The table on the left provides mathematical equivalents necessary for converting barometric pressure units. The various types of pressure exerted upon divers are summarized further below. As atmospheric pressure increases, the height of the mercury in the tube also increases and vice versa. That is, the weight of the mercury in the tube always corresponds to the atmospheric pressure.
In the middle of the 17th century Italian scientist Evangelista Toricelli determined the value of normal atmospheric pressure with the following experiment. A mercury-filled glass tube with a section area of 1cm2 and a closed end was vertically immersed in a vessel full of mercury (Hg), the open end pointing downwards. The level of the mercury inside the tube decreased to a certain extent. Further decrease was impeded by the atmospheric pressure that acted upon the surface of the mercury in the vessel. It turned out that the mercury level in the tube measured 760mm and weighed 1033g. If water had been used instead, a different tube would be necessary. It would have to be longer as many times as water is lighter than air. The level of the water in the tube would correspond to the atmospheric pressure and would equal 10.33m. Therefore, at sea level air exerts a pressure of 1033g/cm2. Having in mind that the total area of the human body is 17,000–18,000cm2, it can be calculated that atmospheric air exerts upon us a pressure of 17 to 18 tonnes!
Scientists have proven that the critical point of the mechanical effect of hydrostatic pressure depends on the evolution level of the organisms. Lower unicellular organisms such as spores, bacteria, and viruses can withstand pressures of thousands of atmospheres. A further increase of pressure causes physical and chemical changes in the cellular structures, thus altering the characteristics of the species.
Divers do not feel the great pressure because the tissues of the human organism contain 65% of liquids that practically do not shrink. In inner cavities, the pressure of the inhaled air counteracts the external pressure. During descent, divers usually do not feel the increasing pressure. They only feel a slight difficulty while breathing because they inhale gases that are under a pressure equal to that of the surrounding water. All underwater diving suits ensure the intake of air held under a pressure that corresponds to the depth at which the diver is. Otherwise, the absence of this condition would cause quick death.
Although divers do not feel the pressure itself, its rapid change may lead to different sicknesses. A quick decrease of pressure during ascent is particularly dangerous and may result in a serious disease called decompression sickness. Read more on that in the Medicine Section.
While under water, a diver feels unequal pressure on the different parts of his or her body. Low parts, if in greater depths than the upper body, endure pressure that is greater by .15–.20x105 Pa than the one on the upper body.

DEEP_SEA DIVING GAS

A GAS used by deep-sea divers could help to treat severe asthma attacks. Tests showed the gas boosts lung function and speeds up recovery within an hour of being given.
French scientists who trialled the diving gas predict it could be a new emergency treatment for asthma sufferers who turn up at hospital in the throes of an attack. The therapy works because it contains a mixture of oxygen and helium. Normal air is made up of 20 per cent oxygen and nearly 80 per cent nitrogen.

Coral and Fish

exotic Blue Deep Sea

Increasing Awareness

In June of 2003 – after hearing testimony in a public forum, during which more than a few local fishers spoke of the long-term benefits of protecting the deep-sea coral, and, consequently, the fish that rely upon the coral – the South Atlantic Fishery Management Council voted to indefinitely extend the fishing restrictions within the Oculina HAPC.
Support from the fishing industry is certainly an encouraging sign. Fishers, managers and scientists together led the charge to extend the Oculina HAPC closure after 2004. As John Reed points out, protected areas mean little without public awareness. More maps indicating the boundaries of the Oculina HAPC would certainly help, as will a further understanding of the importance of these reefs as habitat for important commercial fish species.

Oculina, says Reed, “are like the redwood forests. These reefs are thousands of years old. And there are no others like them in the world.” This alone should make them worth saving and restoring for future generations.

Inner-space trek

During the spring Oculina expedition, aboard the NASA’s 176-foot ships Liberty Star and Freedom Star, Reed was among a team of scientists, support personnel, and media types who looked on as a camera mounted to a remotely operated vehicle (ROV) documented in real-time the contours and conditions of the ocean floor. The view afforded was a spectacular one – an inner space every bit as exotic as images transmitted by NASA from the surface of Mars. The Oculina reefs are home to many fish species, such as red grouper, scamp, tattlers, yellowtail reef fish, bigeyes, rough-tongue bass, amberjack and many more, including some species that are of considerable economic importance to the South Atlantic fishing industry (Figure 3). These fish species rely on the health of the Oculina, and their association with deep-sea coral has been long confirmed. For example: Oculina reefs have traditionally been home to grouper spawning aggregations.

Primary among the objectives of the 2003 expedition were to understand changes in the Oculina HAPC coral and fish populations over the past twenty years and to establish a monitoring baseline for future comparisons.

Evidence of coral destruction was at times overwhelming – once rich thickets, rendered rubble, no fish in view; subterraneous ghost towns (Figures 4 and 5).

The discovery

“When I was first out of graduate school,” says Reed, “I was hired at HBOI, and this was just after they’d discovered the deep-water Oculina reefs using a submersible. They had come across one of these 60- to 100-foot-high deep-sea coral reefs. “My first study, in 1976, was to see what lived in the coral, what used it for habitat. I began to study the invertebrates, and what I found out was that a small coral colony with a head the size of a basketball could hold up to over 2,000 individual animals and hundreds of species, including worms, crabs, shrimp and fish. It was an incredible biologically diverse environment that we had never known about before.

Organisms use brown or dead Oculina as well as white living Oculina for habitat.

Figure 2: Whether dead (brown) or alive (white) – Oculina serves as a high-relief habitat for many organisms, including some commercially important fish species. Photo credit: L. Horn, NURP/UNCW

“By 1980, we realized that this was a totally unique habitat found nowhere else in the continental United States. And possibly nowhere else in the world (Figure 2).

“At the same time, I began to look at how fast the coral grows. So my next study was to see how old the colonies’ heads were. We were seeing coral heads the size of a Volkswagen Beetle. I did a study over two years and found that they actually grow very slowly, about a half an inch a year. So a large head could easily be 100 to 200 years old. Then I did a coral core sample into one of these reefs and determined the age of the dead coral that came from the inside of the reef.”

What Reed and his colleagues learned by radiocarbon dating the dead coral that came from the inside of the reef was that the coral was around 10,000 to 12,000 years old, meaning it began life near the end of the last Ice Age.

“We also came to realize,” Reed continues, “how fragile the coral was: the branches themselves are the diameter of a pencil, and the reefs form into big bushes. So imagine how any heavy weight, like fishing gear, dragging through it could very easily crush it.

“At that time, in the early ‘80s, there was indication that boats were coming down from the Georgia coast and up from the Gulf of Mexico and fishing with roller trawls that were able to fish over the bottom of high-relief areas. Roller trawls have wheels that allow them to easily roll over the bottom of the ocean floor.”

These rare coral reefs, home to hundreds of species, including commercially important fish, were being destroyed. Because of their slow growth rates, it will take hundreds of years to restore them, if they can be restored at all. “My main concern is that while on paper this has been a protected area since 1984, they’ve still been heavily fished,” both by poachers and by the unaware. “Tremendous damage can be done by an errant shrimp trawler going across one of these coral reefs. One pass can destroy a great many Oculina corals.”

Protecting Deep-Sea Corals

Twenty miles off the coast of Florida, stretching from Daytona Beach down to Ft. Pierce, close to the edge of the continental shelf, deep-water coral reefs of Oculina varicosa, or the ivory tree coral (Figure 1), lie 150 to 300 feet beneath the water’s surface. Oculina are quite unique, the only known stand of their variety in the world. As such, in 1984, the South Atlantic Fishery Management Council, under the advice and guidance of NOAA Fisheries, designated a 92-square-nautical-mile portion of these reefs as the Oculina Habitat Area of Particular Concern (Oculina HAPC). In 1994, the Oculina HAPC was closed to all manner of bottom fishing and was designated as the Experimental Oculina Research Reserve. In 2000, the area was expanded to 300-square-nautical-miles and prohibited all gears that caused mechanical disruption to the habitat.


Walk into a bait shop along the coast of Florida, though, and odds are the fishing map you pull from the rack will have little or no indication of the Oculina HAPC, no mention of fishing restrictions and no acknowledgement of an area closed to specific types of fishing. And that’s a problem.
It certainly doesn’t make John Reed’s job any easier. Reed is a marine scientist with the Harbor Branch Oceanographic Institution (HBOI) in Ft. Pierce, Florida. In spring of 2003, Reed served as co-principal investigator on an eight-day expedition led by NOAA's Undersea Research Program (NURP) Center at the University of North Carolina at Wilmington, in collaboration with NOAA Fisheries and the National Aeronautics and Space Administration (NASA). The purpose of the mission was to learn more about the Oculina reefs. Reed has been studying Oculina for 25 years. It was he, in fact, who nominated the Oculina reefs as an HAPC.

DEEP SEA CORAL

EXOTIC DEEP SEA AREA

DEEP OCEAN ARTISTIC

DEEP OCEAN SCIENCE

PlanktonNet


Atlantis Gangway


Pressure


Crane


Ocean Spider