Chapter 8 Aquatic Biodiversity Core Case Study: Why Should We Care About Coral Reefs? Coral reefs form in clear, warm coastal waters of the tropics and subtropics. Formed by massive colonies of polyps. Figure 6-1 Healthy coral reef in the Red Sea covered by colorful algae. Fig. 6-1a, p. 126 Bleached coral reef that has lost most of its algae. Fig. 6-1b, p. 126 Core Case Study: Why Should We Care About Coral Reefs? Help moderate atmospheric temperature by removing CO2 from the atmosphere. Act as natural barriers that help protect 14% of the world’s coastlines from erosion by battering waves and storms. Provide habitats for a variety of marine organisms. AQUATIC ENVIRONMENTS Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface Figure 6-2 Ocean hemisphere Land–ocean hemisphere The salty oceans cover 71% of the earth’s surface. About 97% of the earth’s water is in the interconnected oceans, which cover 90% of the planet’s mostly ocean hemisphere (left) and 50% of its land–ocean hemisphere (right). Freshwater systems cover less than 1% of the earth’s surface. AQUATIC ENVIRONMENTS Figure 6-3 What Kinds of Organisms Live in Aquatic Life Zones? Aquatic systems contain floating, drifting, swimming, bottom-dwelling, and decomposer organisms. Plankton: important group of weakly swimming, free-floating biota. • Phytoplankton (plant), Zooplankton (animal), Ultraplankton (photosynthetic bacteria) Necton: fish, turtles, whales. Benthos: bottom dwellers (barnacles, oysters). Decomposers: breakdown organic compounds (mostly bacteria). Life in Layers Life in most aquatic systems is found in surface, middle, and bottom layers. Temperature, access to sunlight for photosynthesis, dissolved oxygen content, nutrient availability changes with depth. Euphotic zone (upper layer in deep water habitats): sunlight can penetrate. SALTWATER LIFE ZONES The oceans that occupy most of the earth’s surface provide many ecological and economic services. Figure 6-4 Natural Capital Marine Ecosystems Economic Ecological Services Services Climate moderation Food CO2 absorption Animal and pet feed Nutrient cycling Pharmaceuticals Waste treatment Harbors and Reduced storm transportation routes impact (mangroves, barrier islands, Coastal habitats for coastal wetlands) humans Habitats and Recreation nursery areas Employment Genetic resources and Oil and natural gas biodiversity Minerals Scientific Building materials information Fig. 6-4, p. 129 The Coastal Zone: Where Most of the Action Is The coastal zone: the warm, nutrient-rich, shallow water that extends from the high-tide mark on land to the gently sloping, shallow edge of the continental shelf. The coastal zone makes up less than 10% of the world’s ocean area but contains 90% of all marine species. Provides numerous ecological and economic services. Subject to human disturbance. The Coastal Zone Figure 6-5 High tide Coastal Open Sun Zone Sea Low tide Sea level Estuarine Euphotic Zone Zone Continental Photosynthesis shelf Bathyal Zone Abyssal Zone Darkness Fig. 6-5, p. 130 Marine Ecosystems Scientists estimate that marine systems provide $21 trillion in goods and services per year – 70% more than terrestrial ecosystems. Figure 6-4 View of an estuary taken from space. Fig. 6-6, p. 130 Estuaries and Coastal Wetlands: Centers of Productivity Estuaries include river mouths, inlets, bays, sounds, salt marshes in temperate zones and mangrove forests in tropical zones. Figure 6-7 Herring gulls Peregrine falcon Snowy Egret Cordgrass salt marsh Short-billed ecosystem Dowitcher Marsh Periwinkle Phytoplankton Smelt Zooplankton and small crustaceans Soft-shelled clam Clamworm Bacteria Producer to Primary to Secondary to All consumers primary secondary higher-level and producers consumer consumer consumer to decomposers Fig. 6-7a, p. 131 salt marsh ecosystem, Peru. Fig. 6-7b, p. 131 Mangrove Forests Are found along about 70% of gently sloping sandy and silty coastlines in tropical and subtropical regions. Figure 6-8 Estuaries and Coastal Wetlands: Centers of Productivity Estuaries and coastal marshes provide ecological and economic services. Filter toxic pollutants, excess plant nutrients, sediments, and other pollutants. Reduce storm damage by absorbing waves and storing excess water produced by storms and tsunamis. Provide food, habitats and nursery sites for many aquatic species. Rocky and Sandy Shores: Living with the Tides Organisms experiencing daily low and high tides have evolved a number of ways to survive under harsh and changing conditions. Gravitational pull by moon and sun causes tides. Intertidal Zone: area of shoreline between low and high tides. Rocky and Sandy Shores: Living with the Tides Organisms in intertidal zone develop specialized niches to deal with daily changes in: Temperature Salinity Wave action Figure 6-9 Rocky Shore Beach Sea star Hermit crab Shore crab High tide Periwinkle Sea urchin Anemone Mussel Low tide Sculpin Barnacles Kelp Sea lettuce Monterey flatworm Nudibranch Fig. 6-9, p. 132 Barrier Beach Beach flea Peanut worm Tiger Beetle Blue crab Dwarf Clam Olive High tide Sandpiper Ghost Silversides Low tide Mole Shrimp Shrimp White sand Sand dollar Moon macoma snail Fig. 6-9, p. 132 Barrier Islands Low, narrow, sandy islands that form offshore from a coastline. Primary and secondary dunes on gently sloping sandy barrier beaches protect land from erosion by the sea. Figure 6-10 Primary Secondary Bay or Ocean Beach Dune Trough Dune Back Dune Lagoon Intensive No direct Limited No direct Most suitable Intensive recreation, passage recreation passage for development recreation no building or building and walkways or building Grasses Bay shore or shrubs No filling Taller shrubs Taller shrubs and trees Fig. 6-10, p. 133 Threats to Coral Reefs: Increasing Stresses Biologically diverse and productive coral reefs are being stressed by human activities. Figure 6-11 Gray reef shark Green sea Sea nettle turtle Fairy basslet Blue tangs Parrot fish Sergeant major Hard corals Algae Brittle star Banded coral shrimp Phytoplankton Symbiotic Coney algae Zooplankton Blackcap basslet Sponges Moray eel Bacteria Producer to Primary to Secondary to All consumer primary secondary higher-level and producers consumer consumer consumer to decomposers Fig. 6-11, p. 134 Threats to Coral Reefs: Increasing Stresses Figure 6-12 Natural Capital Degradation Coral Reefs Ocean warming Soil erosion Algae growth from fertilizer runoff Mangrove destruction Bleaching Rising sea levels Increased UV exposure Damage from anchors Damage from fishing and diving Fig. 6-12, p. 135 Biological Zones in the Open Sea: Light Rules Euphotic zone: brightly lit surface layer. Nutrient levels low, dissolved O2 high, photosynthetic activity. Bathyal zone: dimly lit middle layer. No photosynthetic activity, zooplankton and fish live there and migrate to euphotic zone to feed at night. Abyssal zone: dark bottom layer. Very cold, little dissolved O2. Effects of Human Activities on Marine Systems: Red Alert Human activities are destroying or degrading many ecological and economic services provided by the world’s coastal areas. Figure 6-13 Natural Capital Degradation Marine Ecosystems Half of coastal wetlands lost to agriculture and urban development Over one-third of mangrove forests lost to agriculture, development, and aquaculture shrimp farms Beaches eroding because of coastal development and rising sea level Ocean bottom habitats degraded by dredging and trawler fishing At least 20% of coral reefs severely damaged and 30– 50% more threatened Fig. 6-13, p. 136 FRESHWATER LIFE ZONES Freshwater life zones include: Standing (lentic) water such as lakes, ponds, and inland wetlands. Flowing (lotic) systems such as streams and rivers. Figure 6-14 Natural Capital Freshwater Systems Ecological Economic Services Services Climate moderation Food Nutrient cycling Drinking water Waste treatment Irrigation water Flood control Hydroelectricity Groundwater Transportation recharge corridors Habitats for many Recreation species Employment Genetic resources and biodiversity Scientific information Fig. 6-14, p. 136 Lakes: Water-Filled Depressions Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of: Littoral zone (near shore, shallow, with rooted plants). Limnetic zone (open, offshore area, sunlit). Profundal zone (deep, open water, too dark for photosynthesis). Benthic zone (bottom of lake, nourished by dead matter). Lakes: Water-Filled Depressions During summer and winter in deep temperate zone lakes the become stratified into temperature layers and will overturn. This equalizes the temperature at all depths. Oxygen is brought from the surface to the lake bottom and nutrients from the bottom are brought to the top. Lakes: Water-Filled Depressions Figure 6-15 Sunlight Green Painted Blue-winged frog turtle teal Muskrat Pond snail Littoral zone Limnetic zone Diving beetle Plankton Profundal zone Benthic zone Northern Yellow Bloodworms perch pike Fig. 6-15, p. 137 Effects of Plant Nutrients on Lakes: Too Much of a Good Thing Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support. Figure 6-16 Effects of Plant Nutrients on Lakes: Too Much of a Good Thing Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support. Oligotrophic (poorly nourished) lake: Usually newly formed lake with small supply of plant nutrient input.