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Water Earth’s Hydrosphere • Hydrosphere = all the parts of the earth that are made up of water – Oceans, Lakes, Rivers – Underground water, clouds The Hydrosphere • More than 70% of Earth’s surface is covered by water. • > 97% of the hydrosphere is salt water – Oceans – Salt Lakes (Great Salt Lake in Utah) • Salt water = Water that contains dissolved salts – 35 g of salt/liter of ocean water Fresh Water • Less dissolved salt than salt water • Lakes, ponds, streams & underground water • <3% of the hydrosphere – >2/3 = frozen glaciers and ice caps Fresh Water • Surface water = water in lakes, streams, and rain runoff • Ground water = found beneath the surface of the earth – Moves more easily through rock layers that are porous – Aquifer = an underground layer of porous rock that contains water Aquifers • Sometimes flow between two layers of rock that water cannot seep through • Pressure accumulates – Water pressure – Weight of rock layer above water • Artesian Wells = wells in which water flows to the surface due to high pressure • Water contained in aquifers is replenished very slowly Aquatic Biomes Aquatic Biomes • Water covers more than 70% of earth. • Aquatic Habitat = a habitat in which organisms live in or on water. Aquatic Biomes • Not grouped geographically the way that terrestrial biomes are • Aquatic biomes are: – Scattered – Determined by depth rather than location Abiotic Factors • Abiotic factors which determine aquatic biomes and terrestrial biomes are not the same • Abiotic factors in terrestrial biomes: – Temperature – Rainfall Abiotic Factors: Aquatic Biomes • • • • Amount of dissolved salts in the water Depth of the water Rate of water flow Amount of dissolved oxygen in the water Salinity • Aquatic biomes can be divided into two main groups based on the amount of dissolved minerals in the water. – Saltwater – Freshwater • All water contains some dissolved salts and other minerals. – Saltwater contains more than freshwater. Salinity • Salinity = the amount of dissolved salts in a sample of water. – Measured in parts per thousand or parts per million (ppm) – Ocean water = 30 parts per thousand – Freshwater = < .5 parts per thousand Salinity • Brackish Water = water that is more saline than freshwater but less saline than ocean water. Ex: Where the Mississippi River meets the Gulf of Mexico – Common in river deltas and coastal marshes – Where fresh water meets the ocean Freshwater Salinity • Lakes, Ponds, Rivers • Exceptions = hypersaline (more saline than the ocean!) lakes – Great Salt Lake in Utah, Mono Lake in California – 40 parts per thousand Salinity vs. Density • Saltwater is denser than fresh water: – Salinity is tested using a hydrometer – Measures buoyancy (how much mass can float on the water) Temperature vs. Density • Warm water is less dense than cooler water – Water temperatures decrease & density increases at lower water depth zones Depth • Ecosystem is greatly influenced by the amount of sunlight that penetrates to the bottom. – Determines the type of plants that grow – Remember: producers (includes plants) form the base of the food web! Depth Zones • Photic Zone = the top layer of water, which receives enough sunlight for photosynthesis to occur – Depth of the photic zone depends upon the turbidity of the water – Open ocean - photic zone = up to 200 m deep Depth Zones • Aphotic Zone = below the photic zone, sunlight never reaches the aphotic zone – Only found in the ocean and deep lakes Depth Zones • Benthic Zone = The floor of a body of water – Ocean = supports microscopic decomposers & scavengers – Shallow freshwater = sunlight allows insect larvae, snails, catfish and turtles to survive
