Aquatic Biodiversity Study Handouts

CHAPTER 7 AQUATIC BIODIVERSITY Objectives 1. Summarize the distribution of light, salt, and temperature in different aquatic life zones. 2. Evaluate the significance of the ecological contributions of the oceans. 3. Briefly describe the characteristics and ecological significance of coral reefs. Describe environmental and economic problems of coral reefs. 4. Distinguish between coastal and inland wetlands. Describe the ecological functions performed by wetlands. Describe environmental problems associated with coastal and inland wetlands. 5. List and compare the four zones of a lake. Distinguish between oligotrophic and eutrophic lakes. Describe stratification and a turnover in a lake. 6. Define watershed. List and distinguish the three zones of a river system. Key Terms (Terms are listed in the same font style as they appear in the text.) polyps (p. 128) xooxanthellae (p. 128) coral bleaching (p. 128) aquatic life zones (p. 128) salinity (p. 128) saltwater (marine) (p. 128) freshwater (p. 128) plankton (p. 129) phytoplankton (p. 129) zooplankton (p. 129) ultraplankton (p. 129) nekton (p. 129) benthos (p. 129) decomposers (p. 129) euphotic zone (p. 129) coastal zone (p. 130) continental shelf (p. 131) estuary (p. 131) coastal wetland (p. 131) mangrove forest swamps (p. 133) intertidal zone (p. 133) rocky shores (p. 133) barrier beaches (p. 133) sand shores (p. 133) barrier islands (p. 133) coral reefs (p. 135) open sea (p. 136) euphotic zone (p. 136) bathyal zone (p. 136) abyssal zone (p. 137) deposit feeders (p. 137) filter feeders (p. 137) freshwater life zones (p. 137) standing (lentic) (p. 137) flowing (lotic) (p. 137) lakes (p. 138) glaciation (p. 138) crustal displacement (p. 138) littoral zone (p. 138) limnetic zone (p. 138) profundal zone (p. 138) benthic zone (p. 138) oligotrophic lake (p. 138) eutrophic lake (p. 139) cultural eutrophication (p. 140) mesotrophic lake (p. 140) surface water (p. 140) runoff (p. 140) watershed (p. 140) drainage basin (p. 140) source zone (p. 140) transition zone (p. 140) floodplain zone (p. 141) inland wetlands (p. 141) marshes (p. 141) swamps (p. 141) prairie potholes (p. 141) floodplains (p. 141) arctic tundra (p. 141) seasonal wetlands (p. 141) Chapter 7 review questions Instructions: You should be able to answer these questions once you have finished the chapter: 1. Define the boldfaced terms in this chapter. (OMIT) 2. What are coral reefs and coral polyps? How are coral reefs formed? List seven ecological and economic services that coral reefs provide. What is coral bleaching, and what are its main causes? 3. What are the two major types of aquatic life zones? 4. Distinguish among phytoplankton, zooplankton, ultraplankton, nekton, benthos, and decomposers found in saltwater and freshwater life zones. 5. Describe major advantages and disadvantages of living in an aquatic environment. 1 6. List four major factors determining the types and numbers of organisms found in the surface, middle, and bottom layers of aquatic systems. How do the concentrations of carbon dioxide and dissolved oxygen vary in these three layers?? 7. What major ecological and economic services are provided by the world’s marine systems? 8. What is the coastal zone? Distinguish among estuaries, coastal wetlands, and mangroves. List three reasons why temperature and salinity vary widely in estuaries and coastal wetlands, and explain why they have such a high NPP. 9. What is the intertidal zone? Distinguish between rocky shores and sandy beaches, and describe the major types of aquatic life found in each. 10. What are barrier islands? Why are they so attractive for human development, and why are human structures built there so vulnerable to destruction? Why is it important to preserve the dunes on barrier islands and beaches? 11. List three reasons why coral reefs are vulnerable to damage. List ten harmful impacts of human activities on coral reefs. 12. What is the open sea, and what are its three major vertical zones? Why is the NPP per unit of area so low in the open sea? 13. List five major harmful human impacts on coastal zones. 14. What is a freshwater life zone, and what are the two major types of such zones? 15. What major ecological and economic services are provided by freshwater systems? 16. What is a lake? Distinguish among the littoral, limnetic, profundal, and benthic zones of a lake. 17. What are the three types of lakes, based on their nutrient content and primary productivity? 18. Distinguish among surface water, runoff, and a watershed. Describe the properties and general forms of life found in the three zones of a river as it flows from mountain highlands to the sea. 19. What are inland wetlands? List six examples of such wetlands. What are seasonal inland wetlands? 20. List four major harmful human impacts on freshwater systems. Outline 7-1 Aquatic Environments A. Saltwater and freshwater aquatic zones cover about 71% of the earth’s surface. These are the equivalent of terrestrial biomes. B. Salinity of the water determines the major types of organisms found in an aquatic environment. C. There are four major types of organisms in aquatic systems. 1. P120 2. Plankton are free-floating, weakly swimming, generally one-celled organisms. There are three major types of plankton: phytoplankton (plant plankton), zooplankton (animal plankton) that they may be single-celled protozoa to large invertebrates such as jellyfish, and ultraplankton that are no more than 2 micrometers wide and are photosynthetic bacteria. 3. Ultraplankton may be responsible for as much as 70% of the primary productivity near the ocean surface. 4. Nekton is a second group of organisms. These are fish, turtles, and whales. 5. A third group of organisms is benthos, which are bottom dwellers; barnacles, oysters, worms, lobsters, and crabs are examples of benthos organisms. 6. Decomposers are a fourth group. These organisms break down organic matter into simple nutrients for use by producers. D. Aquatic environment living has both advantages and disadvantages. Physical boundaries are less fixed, making it more difficult to manage/count aquatic populations of organisms. 1. Food webs are longer, more complex than on land due to fluidity of medium and variety of bottom habitats. 2. Size and less visibility make them more difficult to study. E. Three layers of aquatic life zones can be used: surface, middle, and bottom. 2 Chapter 7 1. 2. 3. 4. 5. 6. 7. Temperature, sunlight availability, dissolved oxygen, and nutrient availability determine types and numbers of producers found in these zones. The euphotic zone is the upper layer where sunlight can penetrate. Clouding or excessive algal growth reduces depth of the euphotic zone. Dissolved oxygen levels are higher near the surface due to photosynthesis in this area. CO2 levels are lower near the surface and higher in deeper, darker layers due to aerobic respiration. Open oceans tend to have limited amounts of nitrates, phosphates, iron, and other nutrients that limit productivity. Shallow waters are generally well supplied with nutrients for growth. Deep dwelling species depend on animal and plant material that die/float to the bottom. Large fish are vulnerable to overfishing depletion. 7-2 Saltwater Life Zones A. Oceans have two major life zones: the coastal zone and the open sea. B. The coastal zone interacts with the land and is much affected by human activities. 1. Ecosystems in coastal zones have a high net primary productivity per unit area. They constitute 10% of the oceans and contain 90% of all marine species. 2. There is ample sunlight and nutrient flow from land, and wind/currents distribute them. 3. The coastal zone extends from the high-tide mark on land to the edge of the continental shelf. 4. Estuaries and coastal wetlands are subject to tidal rhythms, runoff from land, and seawater that mixes with freshwater and nutrients from rivers and streams. 5. Mangrove forest swamps grow in sheltered regions of tropical coasts. They collect mud and anaerobic sediment. 6. Coastal wetlands/estuaries make nutrients available due to constant stirring of bottom sediment. 7. These areas filter toxic pollutants and excess plant nutrients, reduce storm damage, and provide nursery sites for aquatic species. 8. Humans are destroying/degrading these ecosystems; one-third have already been lost. C. Organisms living in the intertidal zone have adapted ways to survive the daily changes in wet/dry conditions and changes in salinity. D. Barrier beaches/sandy shores are gently sloping. Organisms tunnel or burrow in the sand to survive daily changes in conditions. E. Low, sandy, narrow islands that form offshore from a coastline are barrier islands. They generally run parallel to the shore. 1. The islands help protect the mainland, estuaries, and coastal wetlands from heavy storm damage. 2. People want to live on these islands, but they are subject to damage. In spite of this, almost onefourth of barrier islands are developed. 3. Sand is constantly shifting due to winds and parallel currents along the islands. 4. Undisturbed beaches have one or more rows of sand dunes on them. Grass roots hold the sand in place, and the dune is a first line of defense against storms. It is safer to build behind the second set of dunes if any building occurs. 5. Developers want to build on the islands and do not consider the protective services that the dunes provide. Large storms can and have swept away or severely damaged seaside buildings. 6. Governments often provide funds for rebuilding and insurance at fairly low rates for building on the dunes. 7. Some people think that persons building in such risky places should accept all responsibility for repair or replacement due to storm damage. F. Coral reefs in shallow coastal zones of tropical and subtropical oceans support a very diverse, complex ecosystem. 1. They grow slowly and are vulnerable to damage. 2. They thrive in clear, warm, fairly shallow water with a high salinity. The ideal water temperature is between 18–30oC and will bleach if the water warms above this by so much as 1oC. 3. Severe storms, freshwater floods, and invasions of predatory fish adversely affect the reefs. They have survived natural disturbances for a long geologic history. 4. The greatest threats today are due to sediment runoff and other human activities. Coral reef systems may not have enough time to adapt to these rapidly changing conditions. 3 5. There are indications that recovery is possible when restrictions are imposed and pollution is reduced. G. The open sea is divided into three vertical zones based primarily on penetration of light. 1. The euphotic zone is lighted, has floating phytoplankton carrying on photosynthesis, and has low nutrient levels except at upwellings. 2. Dissolved oxygen level is high. 3. Large, fast-swimming predatory fish like swordfish, shark, and bluefin tuna live in this zone. 4. The bathyal zone is the dimly lit middle zone; no producers are in this zone. Zooplankton and smaller fish live in this zone. 5. The abyssal zone is dark and very cold with little dissolved oxygen. The nutrients on the ocean floor occult support about 98% of species living in the ocean. 6. Organisms in this area are deposit feeders, or filter feeders. 7. Hydrothermal vents are present in some areas where specialized bacteria feed on chemical nutrients and are food for other organisms. 8. Low average primary productivity and NPP occurs, but oceans are so large they make the largest contribution to NPP overall. H. About 40% of the world population lives along coasts. Over half of the U.S. population lives within 62 miles of the coast. 7-3 Freshwater Life Zones A. Freshwater life zones contain less than 1% by volume of salt. These zones include standing (lentic) bodies such as lakes, ponds, and wetlands and flowing (lotic) systems such as streams and rivers. B. Lakes are large natural bodies of standing water found in depressions. 1. Rainfall, melting snow, and stream drainage feed lakes. 2. Lakes generally consist of four distinct zones depending on depth and distance from shore. a. The littoral zone is shallow, sunlit water near the shore. b. The limnetic zone is open, sunlit surface water away from shore and is the most productive area for food and oxygen production. c. The profundal zone is deep, open water too dark for photosynthesis. Oxygen levels are lower. d. The benthic zone consists of decomposers and detritus feeders. Fish swim from one zone to another. Sediment washing and dropping detritus feed this area. C. Stratification of water occurs in deep temperate lakes into temperature zones; no mixing occurs. D. During fall and spring, lakes have turnover of water that brings up nutrients, reoxygenates bottom levels, and evens out water temperature. E. Lakes are described with reference to their plant nutrients. 1. An oligotrophic lake is one that has been newly formed and has a small supply of plant nutrients. They often have deep, crystal-clear blue or green water with low net primary productivity. 2. A eutrophic lake has a large or excessive supply of nutrients. They typically are shallow with murky brown or green water with low visibility and high net primary productivity. Cultural eutrophication accelerates this process. 3. Lakes between these two extremes are called mesotrophic lakes. F. Waters flowing from mountains to sea create different aquatic conditions and habitats. 1. Surface water does not sink into the ground. 2. Runoff is surface water that flows into streams and rivers, and the area it drains is called a watershed or drainage basin. G. Three aquatic life zones, each with different conditions can be identified along stream flow. 1. The source zone is narrow and fast moving. It dissolves large amounts of oxygen from air and most plants are attached to rocks. Light is available, but is not very productive. 2. The transition zone forms wider, deeper streams that flow down gentler slopes. The water is warmer, with more nutrients and supports more producers, but has slightly lower dissolved oxygen. 3. The floodplain zone has wider, deeper rivers. Water temperature is warmer, less dissolved oxygen is present, and flow is slower. There may be fairly large numbers of producers such as algae, cyanobacteria, and rooted plants. H. Streams are fairly open ecosystems and receive many nutrients from surrounding lands. 4 Chapter 7 I. Farms, power plants, cities, and recreation areas are often found in floodplains. This also increases excessive nutrient input and pollutant input into the river system. J. Inland wetlands cover the land for a part of all of each year. Wetlands include swamps, marshes, prairie potholes, floodplains, and arctic tundra in summer. 1. Scientists also use soil composition and plant life to define whether a particular area is a wetland. 2. Wetlands provide a number of free ecological services such as filtering toxic wastes/pollutants, absorbing/storing excess water from storms, and providing habitats for a variety of species. K. Human activities have four major impacts on freshwater systems. 1. Dams, diversions, and canals fragment ~60% of the world’s large rivers and destroy habitats. 2. Flood control dikes and levees alter rivers and destroy aquatic habitats. 3. Cities and farmlands add pollutants. 4. Wetlands have been drained or covered with buildings. The U.S. has lost more than 50% of its wetlands since the 1600s. 5. These systems are able to recover when destructive practices are stopped or reduced. Summary 1. The basic types of aquatic life zones are the surface, middle, and bottom layers. The life in aquatic life zones are influenced by temperature, access to sunlight for photosynthesis, dissolved oxygen content, and availability of nutrients. 2. The major types of saltwater life zones are the coastal zone and the open sea. Coastal ecosystems contain estuaries, wetlands, and mangrove swamps. Because of their close proximity to man’s activities, they are under constant assault from water pollution, industrial runoff, construction and soil erosion, agricultural pesticides flowing into rivers and streams, and aquaculture farming. The open sea contains the euphotic zone that is the lighted upper zone of the ocean. The bathyal zone is in the middle and is dimly lit. The lowest zone, the abyssal zone, is dark and very cold. But all are being undermined by human activities: over-harvesting, oil spills, filling-in of wetland areas, agricultural and industrial development and pollution, rising sea levels, and careless fishing/trawling techniques. 3. The major types of freshwater life zones are lakes, wetlands, and rivers. Human activities, such as dams or canals; flood control levees and dikes; and industrial, urban, and agricultural pollutants, all affect the flow and health of freshwater zones. Much of U.S. wetlands have been drained and filled to farm and/or to construct homes and businesses. These actions increase flood potential and encourage droughts. People overfish the waters, pollute the streams, rivers, and lakes, and dump excessive nutrients from pesticides and waste lots into the freshwater sources. 4. We must protect aquatic life zones from the pollutants, water controls, and deterioration that we press upon them every day. 5