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Tide wave - wave caused by the gravitational pull of the Sun and Moon on the Earth. The effect is mainly on the ocean. Its length is aproximately 1/2 around the world. Early tide tables were worked out by observation. There is a high and a low height of these tides, determined by the alignment of the Sun and the Moon. When the Sun and Moon are aligned togather at New and Full Moon phases, the most pull (the gravities are cumulative) is exerted and the tides are higher. This is known as Spring Tide. When the Sun and Moon are aligned at right angles, First and 3rd Quarter Moons, the pull is at its least and the tides are negligible. This is known as Neap Tide
The pull of the Moon, although is is much smaller than the Sun, is greater because it is much closer, as shown by Newtons universal law for gravity. the height of the tide is also determined by the shape and slope of the coast. Constriction such as at the Bay of Fundy can greatly increase the height (16m between high and low tide).
Estuary - semi-enclosed area where fresh and salt water mix. It is rich in nutriants. Sediments are stired up by tides.
Uses of estuaries:
Bioaccumulation the accumulation of pollution through the food chain. Algae will absorb a small amount of pollution. Then a fish eats enough algae to have 10 times the pollution of the algae. Abigger fish then eats the smaller fish again increasing the amount of pollution by 10. By the time a human eats the fish the pollution has increased by 1000, the maximum amount. This can have disasterous results.
A sample of such a bio-magnification disaster is Minainata Bay in Japan. There was big fishing industry there. The people would cut off the heads of the fish during cleaning and feed them to stray cats. The people and cats began having shakes and birth deformities and brittle bones.
It was discovered that a local industry was dumping mercury into the bay. The murcury was being absorbed by the algae, which was then eaten by fish and so on up the food chain until the people and cats were being impacted. Mecury concentrates aroud the brain and nervous system and stays, so it increases over time. It can cause miscarr1ages as well as deformaties.
Several kinds of food fish can pick up the pollution and effect humans. These include; tuna, sword fish, and sharks. Tuna are the worst. they are very fast and pick up more polluted fish. Eating raw fish is the most dangerous. Some pollution can be reduced by cooking.