BESC 201 11 4 2013 Lecture 27 Outline of Last Lecture I Forest Management Outline of Current Lecture II Chapter 12 Central Case Study III Freshwater Systems IV The Ocean V Marine and Coastal Systems Current Lecture 11 4 2013 Fresh Water Oceans and Coasts Central Case Study Starving the Louisiana Coast of Sediment The state of Louisiana is shrinking Wetlands are disappearing beneath the waters of the Gulf of Mexico Louisiana has lost nearly 4 900 km of coastal wetlands an area roughly the size of Delaware The state s coastal wetlands protect cities from storms Louisiana s millions of acres of coastal wetlands were created over the past 7 000 years as the Mississippi River fanned out and deposited its sediments at its delta before emptying into the Gulf of Mexico People have modified the Mississippi River so extensively that its sediments no longer reach the wetlands that need them The river s basin contains roughly 2 000 dams which slow river flow and allow sediments suspended in the water to settle in reservoirs This not only prevents sediments from reaching the river s delta but also slowly fills in each dam s reservoir decreasing its volume and shortening its life span The Mississippi River is also lines with levees which prevent small scale flooding The extraction of large quantities of oil natural gas and saline groundwater associated with oil deposits causes the land to compact lowering soil levels They also enable salty ocean water to penetrate inland and damage freshwater marshes Proposed solutions for coastal erosion center on restoring the system to its natural state by diverting large quantities of water from the Mississippi River into coastal wetlands points to the Atchafalaya River These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Freshwater Systems Fresh Water water that is relatively pure with few dissolved salts Groundwater plays key roles in the water cycle Groundwater water beneath the surface held within pores in soil or rock Aquifers porous spongelike formations of rock sand or gravel that hold water Zone of Aeration contains pore spaces partly filled with water Zone of Saturation the spaces are completely filled with water The largest known aquifer is the Ogallala Aquifer Surface water converges in river and stream ecosystems Surface Water liquid fresh water located atop Earth s surface Surface water becomes groundwater by infiltration Groundwater becomes surface water through springs Tributary a smaller river flowing into a larger one Watershed the area of land drained by a river and all its tributaries Floodplain areas nearest a river s course that are flooded periodically Frequent deposition of silt from flooding makes floodplain soils especially fertile Lakes and ponds are ecologically diverse systems Littoral Zone abounds in invertebrates on which fish birds turtles and amphibians feed Benthic Zone extends along the bottom of the lake or pond from shore to the deepest point and is home to many invertebrates Limnetic Zone the open portion of a lake or pond far from shore sunlight penetrates these shallow waters Oligotrophic low in nutrients and high in oxygen Freshwater wetlands include marshes swamps bogs and vernal ponds Wetlands systems in which the soil is saturated with water Freshwater Marshes shallow water allows plants such as cattails and bulrushes to grow above the water surface Swamps consist of shallow water rich in vegetation but they occur in forested areas Bogs ponds covered with thick floating mats of vegetation and can represent a stage in aquatic succession Vernal Pools seasonal wetlands that form in early spring from rain and snowmelt and dry up once weather becomes warmer The Ocean The physical makeup of the ocean is complex Currents vest riverlike flows that move in the upper 400 m of water horizontally and for great distances Upwelling the rising of cold dense water toward the surface Downwellings warm surface water rich in dissolved gases is displaced downward providing an influx of oxygen for deep water life The deepest spot in the oceans the Mariana Trench in the South Pacific Longest mountain range is under water the Mid Atlantic Ridge Photic Zone well lit top layer Pelagic habitats and ecosystems occurring between the ocean s surface and floor Benthic habitats and ecosystems that occur on the ocean floor Currents affect climate Thermohaline Circulation worldwide current system in which warmer fresher water moves along the surface and colder saltier water which is denser moves deep beneath the surface El Ni o Southern Oscillation ENSO a systematic shift in atmospheric pressure sea surface temperature and ocean circulation in the tropical Pacific Ocean El Ni o triggered when air pressure decreases in the eastern Pacific and increases in the western Pacific weakening the equatorial winds and allowing the warm water to flow eastward La Ni a cold waters rise to the surface and extend westward in the equatorial Pacific when winds blowing to the west strengthen and weather patterns are affected in opposite ways Marine and Coastal Systems Fresh water meets salt water in estuaries Estuaries water bodies where rivers flow into the ocean mixing fresh water with salt water Salt marshes line temperate shorelines Salt Marshes occur where the tides wash over gently sloping sand or silty substrates Tidal Creeks channels where rising and falling tides flow in and out Mangrove forests line coasts in the tropics and subtropics Mangroves salt tolerant and they have unique roots that curve upward like snorkels to attain oxygen or that curve downward like stilts to support the tree in changing water levels Intertidal zones undergo constant change Intertidal Littoral spread between the uppermost reach of the high tide and the lowest limit of the low tide Tides the periodic rising and falling of the ocean s height at a given location caused by the gravitational pull of the moon and sun The rocky intertidal zone is so diverse because environmental conditions such as temperature salinity and moisture change dramatically from the high to the low reaches Kelp forests harbor many organisms Kelp large brown algae Coral reefs are treasure troves of biodiversity A coral reef is a mass of calcium carbonate composed of the skeletons on tiny invertebrate animals known as corals Zooxanthellae symbiotic algae which inhabit their bodies and produce food through