Life as we know it on this planet is based on water. The chemical
required to maintain life take place in water, either inside or outside of
cells. Living organisms either live in water or have specific
and structures to collect and conserve water within their
adjust their behavior so as to maximize the availability of water for their
needs. Also the balance of chemicals in seawater is very similar to
balance of chemicals found in the fluids of land-dwelling creatures,
suggesting a movement from the oceans onto land.
Survival also requires energy input to drive these chemical reactions
and environmental conditions suitable to maximize the efficiency of these
reactions. Organisms in the oceans and on land have come to develop
required mechanisms to meet these needs. There are many examples of situations
where organisms have developed very interesting mechanisms to take
advantage of environmental conditions where they can have an edge on the
competition: two of these are coral reefs and hydrothermal vents.
Coral reefs are vast structures formed by the skeletons of living and
coral polyps. They require huge amounts of calcium carbonate in seawater to
provide the basis for the structural material of the
skeletons. Temperature affects the solubility of calcium carbonate,
with larger amounts dissolving in warmer waters. Therefore, corals
tend to form reefs
in areas with temperatures around 21 degrees celcius, normally between
25 degrees N and 25 degrees S latitude (cold currents in these areas, however,
limit the areas of reef development).
Temperature has the opposite effect on the solubility of gases; gases
are more soluble in cold water and less so in warm.
Therefore, the warm tropical waters favorable to reef development because of
the mineral content are unfavorable because of lack of oxygen.
However, it is within these waters that reefs exist.
To provide oxygen so the corals can survive in warm waters,
an interesting symbiotic relationship developed between the coral polyps
and dinoflagellates called zooxanthellae. The zooxanthellae carry out
photosynthesis to produce oxygen. Photosynthesis the biochemical
process that combines water and carbon
dioxide, in the presence of sunlight, to produce sugars and oxygen.
Zooanthellae also help in the formation of skeletal material from
In return, the coral polyps provide a safe haven, carbon dioxide, and a
the sunlight for the zooanthellae. This symbiosis, a true mutualistic
relationship, helps explain the tremendous productivity of the coral
Hydrothermal vents are found at the opposite end of the oceans; while coral
reefs exist mainly in the upper 30 meters of the ocean, hydrothermal
near the bottom at depths in excess of 2800 meters. Vents were first
discovered in 1977 by Robert Ballard
(the JASON Project man) and J.F. Grassle of Woods Hole while diving
near the Galapagos Islands in the submersible Alvin. These hot springs
water at temperatures in excess of 350 degrees celcius with large
quantities of dissolved
metals and sulfur. Since then, additional sites have been discovered in
the Atlantic and Pacific oceans, and within the freshwater lakes of Lake
Baikal in Siberia and Yellowstone Lake in the U.S. More intriguing still
was the discovery of vast numbers of organisms living in the vicinity
of these vents, despite the fact that there is absolutely no sunlight,
which means no photosynthesis.
The vent organisms, like the corals, have also developed symbiotic
relationships so they can survive in these harsh conditions.
The best known of the vent-dwellers is the vent tube worm, which is
approximately 3 meters in length! These worms have a symbiotic
relationship with chemosynthetic bacteria. Instead of capturing the
sunlight's energy by photosynthesis, chemosynthetic bacteria
produce energy by oxidizing hydrogen sulfide gas from the vent water. Other
energy-rich compounds used by chemosynthetic bacteria include metals,
methane gas, and petroleum. The energy is then used to convert carbon
dioxide into carbohydrates, which are food for the worm. The waste
products from the worm then nourish the bacteria to complete the
Thus we see that, while chemistry dictates the environmental conditions of
the oceans, organisms have evolved ways of occupying specific, if initially
inhospitable, areas and surviving quite successfully.
This completes How does Seawater Chemistry affect Marine Life?
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