Aquatic Biomes

<h1>Text Preview</h1> <p>Aquatic biomes are categorized as freshwater and marine biomes. Freshwater biomes include lakes, rivers, wetlands, and estuaries. </p> <p>Marine biomes are often grouped together as the oceanic biome, which is subdivided into a number of zones. These are the intertidal zone between the low and high tide marks; coral reefs; the open ocean, or pelagic zone; the ocean bottom, or benthic zone; and the deepwater trenches of the abyssal zone. The abyssal zone actually consists of the very deepest benthic zones.</p> <p>Large bodies of fresh water are called lakes. Deep lakes are low in nutrients. Shallow lakes have higher nutrient levels, usually because they are warmer, and sunlight allows more phytoplankton to flourish.</p> <p>Rivers and streams are bodies of fresh water that continually flow in one direction. Rivers generally carry more nutrients and more sediment from soil erosion than streams do. Near the wider mouth of a river, the bottom is usually composed of silt from the deposition of sediment over long periods of time. </p> <p>Wetlands are areas saturated with moisture. Bogs, marshes, and swamps are all wetlands. Some wetlands are only periodically flooded, while others are wet throughout the year. </p> <p>Over the past few hundred years, humans have destroyed wetlands to clear land for cities. In the United States, before white settlers arrived there were almost 400 million acres of wetlands. Today, just over 100 million acres remain.</p> <p>Estuaries and their associated wetlands, called mudflats and saltmarshes, are areas in which salt water meets freshwater, usually at the mouth of a river. Estuarine animals and plants are adapted to respond to changes in salinity that occur along with the rise and fall of the tides. Seaweeds, marsh grasses, and, in the tropics, mangrove trees are typical estuarine plants.</p> <p>Organisms that live in the intertidal zone, the seashore region between high tides and low tides, have to respond to the mechanical action of waves, as well as a daily cycle of drying out and flooding. </p> <p>Coral reefs are widely distributed in warm shallow waters. They are composed of relatives of hydras called cnidarians, and the living polyps are covered by a hard shell of calcium carbonate.</p> <p> Cnidarians are associated with photosynthetic algae, which provide the cnidarians with nutrients. </p> <p>Coral reefs are home to a wide variety of invertebrates, fishes, sea urchins, and other organisms.</p> <p>The pelagic zone is made up of the world’s open oceans. The topmost layer of the ocean is affected by the sun’s light, and this area is home to plankton and a variety of fish species. If the water is clear, photosynthesis can occur at depths of up to 500 feet, although 100 to 300 feet is more usual.</p> <p>The benthic zone is the ocean’s bottom. It consists of sand, silt, and decaying organisms. Animals and plants found in the benthic zone include seaweed, bacteria, fungi, sponges, sea anemones, worms, sea stars, and fishes.</p> <p>The very deepest parts of the oceans form the abyssal zone. Although the water in this region is very cold—around 3° Celsius, the abyssal zone supports many species of invertebrates and fishes. </p> <p>Hydrothermal vents, geysers that produce super-hot, mineral-rich water, help support a diverse community of organisms found along the ocean floor. </p> <p>Chemoautotrophs, bacteria that can synthesize organic compounds without natural light, thrive near these vents because of the warmth and the large amounts of hydrogen sulfide and other minerals they can use as nutrients.</p> <p>The white tube worms with red feathery caps live alongside hydrothermal vents, where the chemoautotrophic bacteria inside them provide the nutrients they need to survive.</p> <p id="TextCopyright">Copyright 2006 The Regents of the University of California and Monterey Institute for Technology and Education</p>