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.
Eutrophic (well nourished) lake: Over time, sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth. Effects of Plant Nutrients on Lakes: Too Much of a Good Thing
Cultural eutrophication:
Human inputs of nutrients from the atmosphere and urban and agricultural areas can accelerate the eutrophication process. Freshwater Streams and Rivers: From the Mountains to the Oceans
Water flowing from mountains to the sea creates different aquatic conditions and habitats. Figure 6-17 Rain and Lake Glacier snow Rapids Waterfall Tributary Flood plain Oxbow lake Salt marsh Delta Deposited sediment Ocean Source Zone
Transition Zone
Water Sediment Floodplain Zone
Fig. 6-17, p. 139 Case Study: Dams, Wetlands, Hurricanes, and New Orleans
Dams and levees have been built to control water flows in New Orleans. Reduction in natural flow has destroyed natural wetlands.
Causes city to lie below sea-level (up to 3 meters).
Global sea levels have risen almost 0.3 meters since 1900. Freshwater Inland Wetlands: Vital Sponges
Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats.
Figure 6-18 Freshwater Inland Wetlands: Vital Sponges
Filter and degrade pollutants. Reduce flooding and erosion by absorbing slowly releasing overflows. Help replenish stream flows during dry periods. Help recharge ground aquifers. Provide economic resources and recreation. Impacts of Human Activities on Freshwater Systems
Dams, cities, farmlands, and filled-in wetlands alter and degrade freshwater habitats.
Dams, diversions and canals have fragmented about 40% of the world’s 237 large rivers.
Flood control levees and dikes alter and destroy aquatic habitats.
Cities and farmlands add pollutants and excess plant nutrients to streams and rivers.
Many inland wetlands have been drained or filled for agriculture or (sub)urban development. Impacts of Human Activities on Freshwater Systems
These wetlands have been ditched and drained for cropland conversion.
Figure 6-19