Chapter 8 Aquatic Biodiversity

AQUATIC ENVIRONMENTS  Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface Figure 6-2

AQUATIC ENVIRONMENTS Figure 6-3

Biological Zones in the Open Sea: Light Rules  Euphotic zone: brightly lit surface layer. Nutrient levels low, dissolved O 2 high, photosynthetic activity. Nutrient levels low, dissolved O 2 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. 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 O 2. Very cold, little dissolved O 2.

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. Plankton: important group of weakly swimming, free-floating biota. Phytoplankton (plant), Zooplankton (animal), Ultraplankton (photosynthetic bacteria)Phytoplankton (plant), Zooplankton (animal), Ultraplankton (photosynthetic bacteria) Necton: fish, turtles, whales. Necton: fish, turtles, whales. Benthos: bottom dwellers (barnacles, oysters). Benthos: bottom dwellers (barnacles, oysters). Decomposers: breakdown organic compounds (mostly bacteria). Decomposers: breakdown organic compounds (mostly bacteria).

Marine Ecosystems  The oceans that occupy most of the earth’s surface provide many ecological and economic services.  Scientists estimate that marine systems provide $21 trillion in goods and services per year – 70% more than terrestrial ecosystems. Figure 6-4

The Coastal Zone  Warm, nutrient-rich, shallow water that extends from the high-tide mark on land to the gently sloping, shallow edge of the continental shelf.  Makes up less than 10% of the world’s ocean area but contains 90% of all marine species.

Estuaries and Coastal Wetlands  Estuaries include river mouths, inlets, bays, sounds, salt marshes in temperate zones and mangrove forests in tropical zones. Figure 6-7

Estuaries and Coastal Wetlands Estuaries and coastal marshes provide ecological and economic services. Filter toxic pollutants, excess plant nutrients, sediments, and other pollutants. 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. 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. Provide food, habitats and nursery sites for many aquatic species.  Mangrove forests are found along sandy and silty coastlines in tropical and subtropical regions.

Rocky and Sandy Shores  Organisms in intertidal zone develop specialized niches to deal with daily changes in: Temperature Temperature Salinity Salinity Wave action Wave action Figure 6-9

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

Coral Reefs Formed by massive colonies of polyps.  Form in clear, warm coastal waters of the tropics and subtropics.  Help moderate atmospheric temperature by removing CO 2 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.

Threats to Coral Reefs  Biologically diverse and productive coral reefs are being stressed by human activities. Figure 6-11

Fig. 6-12, p. 135 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 Natural Capital Degradation Coral Reefs

Effects of Human Activities on Marine Systems  Human activities are destroying or degrading many ecological and economic services provided by the world’s coastal areas. Figure 6-13

FRESHWATER LIFE ZONES  Freshwater life zones include: Standing (lentic) water such as lakes, ponds, and inland wetlands. Standing (lentic) water such as lakes, ponds, and inland wetlands. Flowing (lotic) systems such as streams and rivers. Flowing (lotic) systems such as streams and rivers. Figure 6-14

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). Littoral zone (near shore, shallow, with rooted plants). Limnetic zone (open, offshore area, sunlit). Limnetic zone (open, offshore area, sunlit). Profundal zone (deep, open water, too dark for photosynthesis). Profundal zone (deep, open water, too dark for photosynthesis). Benthic zone (bottom of lake, nourished by dead matter). 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. 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. Oxygen is brought from the surface to the lake bottom and nutrients from the bottom are brought to the top.

Effects of Plant Nutrients on Lakes  Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support. Oligotrophic (Few nutrients) newly formed or high mountain lake Oligotrophic (Few nutrients) newly formed or high mountain lake Eutrophic (well nourished) sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth. Eutrophic (well nourished) sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth.  Cultural eutrophication: Humans activities cause acceleration Humans activities cause acceleration Fertilizers & other chemicalsFertilizers & other chemicals

Freshwater Streams and Rivers  Water flowing from mountains to the sea creates different aquatic conditions and habitats. Figure 6-17

Freshwater Inland Wetlands  Inland wetlands act like natural sponges Filter and degrade pollutants. Filter and degrade pollutants. Reduce flooding and erosion by absorbing slowly releasing overflows. Reduce flooding and erosion by absorbing slowly releasing overflows. Help replenish stream flows during dry periods. Help replenish stream flows during dry periods. Help recharge ground aquifers. Help recharge ground aquifers.  Provide economic resources and recreation. Figure 6-18

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. 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. Flood control levees and dikes alter and destroy aquatic habitats. Cities and farmlands add pollutants and excess plant nutrients to streams and rivers. 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. Many inland wetlands have been drained or filled for agriculture or (sub)urban development.

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). Causes city to lie below sea-level (up to 3 meters). Global sea levels have risen almost 0.3 meters since Global sea levels have risen almost 0.3 meters since  These wetlands have been ditched and drained for cropland conversion.