Chapter 8: Aquatic Biodiversity

1. Chapter 8: Aquatic Biodiversity Jason Zheng

2. 8-1: What is the General Nature of Aquatic Systems The Earth is made mainly of Water. Saltwater covers around 71% of the earth’s surface. Freshwater occupies only about 2.2% Global Ocean: is a single and continuous body of water, geographers divide it into four large areas- Atlantic, Pacific, Arctic, and Indian. The Largest ocean is the Pacific, which contains more than half of the earth’s water.

3. 8-1 Cont. Aquatic life Zones- saltwater and freshwater portions of the biosphere that can support life. Distribution of many aquatic organisms is determined largely by the water’s salinity. Saltwater or marine life zones: Oceans, bays, estuaries, coastal wetlands, shorelines, coral reefs, and mangrove forests. Freshwater life zones: Lakes, rivers, streams, and inland wetlands.

4. 8-1 Cont. Saltwater and freshwater contains organisms called planktons. There are three groups of planktons: Phytoplankton which includes many types of Algae. Zooplankton which consists of primary consumers, they feed off of each other. Ultraplankton which are small photosynthetic bacteria which are in 70% of ocean surface. Decomposers: breaks down organic compounds in dead bodies and wastes.

5. 8-2: Why are Marine Aquatic Systems Important? The marine coastal ecosystems make over $12 Trillion per year. Coastal Zone- The warm, nutrient-rich, shallow water that extends from the high-tide mark on land to the gently sloping, edge of continental shelf. Most coastal zone aquatic systems such as estuaries, coastal marshes, mangrove forests, and coral reefs have a high net primary productivity. Estuaries- are where rivers meet the sea.

6. 8-2 Cont. Coastal Wetlands- coastal land areas covered with water all or part of the year. Sea grass beds are another component of coastal marine biodiversity. Mangrove forests are found along some 70% of gently sloping sandy coastlines in tropical and subtropical regions, especially Australia and Southeast Asia.

7. 8-2 Cont. Intertidal zone- The area of shoreline between low and high tides. Organisms living in this zone must not be swept away or crushed by waves. Some coasts have steep rocky shores that are pounded by waves. Other shores have sloping sandy shores that has different types of organisms. Coral reefs are the worlds oldest, most diverse, and productive ecosystem. Open sea- sharp increase in water depth at the edge of the continental shelf separates the coastal zone from the vast volume of the ocean.

8. 8-3: How Have Human Activities Affected Marine Ecosystems? In 2008, scientists have tried 17 different human activities in oceans and it affect the worlds ocean by 41%. In 2010, 45% of the worlds population and more than half of the US population lived along the coast has experienced rapid changes. Major Threats include: Coastal development, Runoff of nonpoint source pollutants, Point-source pollutants, Pollution and degradation, overfishing, and fishing trawlers.

9. 8-3 Cont. Between 1940 and 2007, the number of people living in the Chesapeake Bay area grew from 3.7 million to 16.8 million, and could reach 18 million by 2020. The estuary receives wastes from point and non- point sources scattered throughout a huge drainage basin in parts of six states and the District of Columbia.

10. 8-3 Cont. However, by 2008, despite 25 years of effort costing almost $6 billion, the program had failed to meet its goals. This was because of increased population and development, a drop in state and federal funding, and lack of cooperation and enforcement among local, state, and federal officials.

11. 8-4: Water Stands in Some Freshwater Systems and Flows in Others Freshwater life zones include standing bodies of freshwater such as lakes, ponds, and inland wetlands, and flowing systems such as streams and rivers. Although these freshwater systems cover less than 2.2% of the earth’s surface, they provide a number of important ecological and economic services. Lakes are large natural bodies of standing fresh- water formed when precipitation, runoff, streams, rivers, and groundwater seepage fill depressions in the earth’s surface.

12. 8-4 Cont. Freshwater lakes vary tremendously in size, depth, and nutrient content. Deep lakes normally consist of four distinct zones that are defined by their depth and distance from shore. The top layer, called the littoral zone, is near the shore and consists of the shallow sunlit waters to the depth at which rooted plants stop growing. The next layer is the limnetic zone, the open, sunlit surface layer away from the shore that extends to the depth penetrated by sunlight. The main photosynthetic zone of the lake, this layer produces the food and oxygen that support most of the lake’s consumers. Next comes the profundalzone, a layer of deep, open water where it is too dark for photosynthesis. The bottom layer of the lake is called the benthic zone, inhabited mostly by decomposers, detritus feeders, and some species of fish.

13. 8-4 Cont. Ecologists classify lakes according to their nutrient content and primary productivity. Lakes that have a small supply of plant nutrients are called oligotrophic lakes. Glaciers and mountain streams supply water to many such lakes, bringing little in the way of sediment or microscopic life to cloud the water. Over time, sediment, organic material, and inorganic nutrients wash into most oligotrophic lakes, and plants grow and decompose to form bottom sediments. A lake with a large supply of nutrients needed by producers is called a eutrophiclake.

14. 8-5: How Have Human Activities Affected Freshwater Ecosystems? First, dams and canals fragment about 40% of the world’s 237 largest rivers. Second, flood control levees and dikes built along rivers disconnect the rivers from their floodplains. A third major human impact on freshwater systems comes from cities and farms. Fourth, many inland wetlands have been drained or filled to grow crops or have been covered with concrete, asphalt, and buildings.

15. 8-5 Cont. The rest were lost to mining, logging, oil and gas extraction, highway construction, and urban development. The heavily farmed U.S. state of Iowa has lost about 99% of its original inland wetlands. This loss of natural capital has been an important factor in increased flood damage in the United States, which are examples of unnatural disasters. Many other countries have suffered similar losses. For example, 80% of all inland wetlands in Germany and France have been destroyed.

16. 8-5 Cont. Three Big Ideas: Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface, and oceans dominate the planet. The earth’s aquatic systems provide important ecological and economic services. Human activities threaten biodiversity and disrupt ecological and economic services provided by aquatic systems.