1	Aquatic ecosystems All life is dependent on WATER. Salt- and fresh- water ecosystems have major differences, but both have been significantly impacted by human activities.
2	READING ASSIGNMENT Chapter 50, p1155- 1160; Essay p1164. A review of the Water lecture, x1 05, may help to understand this lecture. Your text has nothing on the impact of humans on aquatic ecosystems.
3	AQUATIC ECOSYSTEMS Freshwater Wetlands with emergent vegetation Ponds and Lakes Streams and Rivers –flowing water Saltwater Inland, e.g., Great Salt Lake Oceans
4	Freshwater versus Saltwater Rain starts close to pure water, but it does have gases from atmosphere dissolved in it. Once in the ground the water picks up or exchanges additional materials that dissolve in it. The ocean is 3.5% solids (salt). Organisms in freshwater have to pump water out of their cells, while organisms in saltwater have to do work to keep water inside their cells.
5	Oceans Most of the water on earth is in oceans. Depth is important: The pressure is equal to 1 atmosphere for every 10 m of depth. –Bends of divers Sun light is absorbed and below 40 m it is dark Deep areas are dependent on currents to bring oxygen which is essential for animals. Strange organisms live in the ocean depths. Hydrothermal vents are source for life.
6	The water cycle Net movement of water from oceans to the land. Precipitation events (or lack thereof) can result in flooding and drought. The water that returns via rivers carries materials dumped into the river or picked up from land.
7	Streams and Rivers Watershed of a stream is the patch of land that catches precipitation for that stream. Channel size is determined by flow rates. Greater drops in elevation per unit length make the water flow faster. Slow flowing rivers naturally meander, curve in loops rather than go in a straight line. ‘Flood stage’ is a depth when river overflows its banks.
8	Transportation by Rivers People have used rivers to get themselves and goods to new places for a long time. People have also used flowing water to clean and get rid of waste. Sewers collect waste water which flows to & thru a processing plant removing BOD before being returned to a river. Flowing water transports both nutrients and sediments.
9	Oxygen in Water Oxygen is not very soluble in water, 16 mg/l. Metabolism of aqueous organic compounds can quickly use all the oxygen in water, creating anaerobic conditions which kill fish. BOD, biological oxygen demand, measures how much oxygen would be used in respiration of organics in water in 5 days.
10	Estuary Typically sediments transported by rivers accumulate in ocean forming shallow areas near the river mouth known as estuaries. Shallowness encourages emergent plants, while the transport of nutrients by the river and mixing caused by ocean tides making oxygen available make estuaries very productive.
11	Ocean Dead Zones Nutrient transport can have negative consequences. Nitrogen transported by the Mississippi River has increased algal growth in the Gulf of Mexico. When they die, algae sink to the bottom and their BOD (via decomposition) has depleted the oxygen near the bottom of the ocean. Fish flee water without oxygen and from the fisherman’s point of view that part of the ocean is a ‘dead zone’.
12	Shallow Ocean Most continents are surrounded by a ‘shelf’ where the ocean is relatively shallow (less than 200 m) far out from the shore. Continental shelfs are where almost all the ocean fishing occurs. A fish population that can no longer provide a good catch, because the population is now too small is said to be ‘overfished’.
13	Overfishing There have been many examples of overfishing. Sardine fishery of Monterey CA Lake trout in Lake Michigan Herring in the North Sea Cod off MA and Canada Some overfished populations recover after fishing stops, but most have not recovered.
14	Lake Michigan 6^th largest freshwater lake in the world 3^rd largest of the Great Lakes Ave depth = 85 m, Max = 282 m Volume = 4,920 km³, retention time 99 years Total drainage basin = 118,000 km² IL drainage basin = 300 km² Sand dunes on south and east sides
15	Lake Michigan
16	Water Crib Chicago water comes from pumping stations far out in Lake Michigan
17	Fish of Lake Michigan Lake trout, Whitefish and Perch are the native fish of Lake Michigan The fauna has been dramatically altered by invasions and deliberate introductions. Invaders Sea Lamprey, Alewife, Round Gobi Introductions Smelt, Coho Salmon, Chinook Salmon
18	Pollution Pollution can be defined as inputs that significantly alter a community. There are many forms of pollution Poisons, biocides Physical factors, e.g., heat Nutrients can be pollutants Organisms, biological pollution
19	Pollution: Fecal Contamination E. coli is the common bacteria of the human gut. It does not (normally) cause disease, but its presence in water indicates potential contamination by sewage which may contain disease causing organisms. The ‘fecal coliform count’ determines the density of E. coli in water. Beaches are closed if count exceeds a threshold.
20	Eutrophication A form of nutrient pollution Clear water implies that the density of fine particles, including small organisms, is not high. Lakes with low nutrients and few algae, such as Lake Michigan, are called oligotrophic. Lakes with high abundance of nutrients and small organisms are called eutrophic. While the prefix ‘eu’ means ‘good’, often such lakes have too much of a ‘good’ thing.
21	Thermoclines and Lake Turnover Water is most dense at 4° C, both ice and warm water ‘float’. In summer the warmest water is at the surface. The thermocline is a depth where the temperature drops dramatically as one goes deeper. In fall the surface water cools and when it gets colder than 4° C it sinks to the bottom, bringing dissolved oxygen to the bottom of the lake.
22	Vocabulary Freshwater Saltwater Eutrophic Pollution Thermocline Biological Oxygen Demand, BOD Dead zone Overfishing Estuary Flood stage Oligotrophic Water cycle