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Tide pools can be the best or worst of microhabitats depending on their position on the shore. There are many physical factors at work in these pools. Let's review these factors...

Tide Pool Physical Factors

A large, shallow pool has a large surface area to volume ratio or a lot of the pool is exposed at the surface. A small, deep pool has a small surface area to volume ratio. Shape and volume become important when we consider the other factors that contribute to stress in a tide pool.
The temperature of tide pools is affected by air temperature and direct sunlight on the pool. Shallow pools with large surface areas are likely to be more affected by temperature. The major impact of temperature changes on organisms is a change in rates of photosynthesis and respiration. For every 10 degrees centigrade, photosynthesis increases by one and a half times and respiration by two to three times. This causes a build up of by-products, such as carbon dioxide and oxygen, within the water.
Photosynthesis in plants, especially algae, cause oxygen concentrations to peak in the afternoon. At night, available oxygen is depleted rapidly and animals migrate to the surface. A pool with a large surface area to volume ratio will allow more oxygen to diffuse into the water from the air.
Carbon Dioxide and pH
The other result of photosynthesis during the day is that carbon dioxide is taken up by the plants. As the level of carbon dioxide drops, the pH rises, making the water more alkaline. This change is reversed at night when photosynthesis stops but plants and animals continue to respire - using up oxygen and releasing carbon dioxide. High levels of dissolved carbon dioxide in the water make the pool more acidic.
The sun and wind evaporate water from the surface of pools. In isolated tide pools, this causes an increase in salinity (salt-concentration). Heavy rainfall can lower salinity rapidly, however the less dense freshwater often forms a layer above the salty water. The mixing is not always uniform and animals and plants in the pool's depths may remain unaffected. Some species are able to survive a wide salinity range.

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