Abundant plankton serve as the base of the food chain for larger animals such as whales and dolphins. Within the oceanic zone there is thermal stratification where warm and cold waters mix because of ocean currents. Zooplankton, protists, small fishes, and shrimp are found in the neritic zone and are the base of the food chain for most of the world’s fisheries.īeyond the neritic zone is the open ocean area known as the oceanic zone. Phytoplankton and floating Sargassum (a type of free-floating marine seaweed) provide a habitat for some sea life found in the neritic zone. The water here contains silt and is well-oxygenated, low in pressure, and stable in temperature. Since light can penetrate this depth, photosynthesis can occur in the neritic zone. The neritic zone extends from the intertidal zone to depths of about 200 m (or 650 ft) at the edge of the continental shelf. Another consequence of the pounding waves is that few algae and plants establish themselves in the constantly moving rocks, sand, or mud. The exoskeletons of shoreline crustaceans (such as the shore crab, Carcinus maenas) are tough and protect them from desiccation (drying out) and wave damage. The shore of the intertidal zone is also repeatedly struck by waves, and the organisms found there are adapted to withstand damage from the pounding action of the waves (Figure 1). Therefore, living things that thrive in the intertidal zone are adapted to being dry for long periods of time. Organisms are exposed to air and sunlight at low tide and are underwater most of the time, especially during high tide. The intertidal zone is an extremely variable environment because of tides. ![]() In some cases, the intertidal zone is indeed a sandy beach, but it can also be rocky or muddy. Generally, most people think of this portion of the ocean as a sandy beach. ![]() ![]() The intertidal zone, which is the zone between high and low tide, is the oceanic region that is closest to land (Figure 1). Sea urchins, mussel shells, and starfish are often found in the intertidal zone, shown here in Kachemak Bay, Alaska.
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