Chapter 6 Aquatic Biodiversity

Core Case Study: Why Should We Care About Coral Reefs?  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.

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. 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).

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. Provides numerous ecological and economic services. Subject to human disturbance. Subject to human disturbance.

The Coastal Zone Figure 6-5

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. 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.

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.

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).

Effects of Plant Nutrients on Lakes: Too Much of a Good Thing Oligotrophic (poorly nourished) lake: Usually newly formed lake with small supply of plant nutrient input. 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. Eutrophic (well nourished) lake: Over time, sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth. Figure 6-16

Effects of Plant Nutrients on Lakes: Too Much of a Good Thing  Eutrophication a scientific term describing the overfertilization of lakes with nutrients and the changes that occur as a result a scientific term describing the overfertilization of lakes with nutrients and the changes that occur as a result the "bloom" or great increase of phytoplankton in a water body the "bloom" or great increase of phytoplankton in a water body  Cultural eutrophication: Human inputs of nutrients from the atmosphere and urban and agricultural areas can accelerate the eutrophication process. Human inputs of nutrients from the atmosphere and urban and agricultural areas can accelerate the eutrophication process.

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. 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.