Chapter 6 Aquatic Biodiversity

Core Case Study: Why Should We Care About Coral Reefs?  Moderate climate (remove CO2)  Protect from erosion  Habitats  Grow slowly/disrupted easily  70% of reefs are unstable Figure 6-1

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

What Kinds of Organisms Live in Aquatic Life Zones?  Plankton:Phytoplankton (plant), Zooplankton (animal), Ultraplankton/nanoplankton (photosynthetic bacteria)  Nekton: fish, turtles, whales  Benthos: bottom dwellers (octopus, oysters)  Decomposers: breakdown organic compounds (mostly bacteria)

Life in Layers  Temperature, access to sunlight for photosynthesis, dissolved oxygen content, nutrient availability changes with depth.  Euphotic zone - sunlight can penetrate (about 200 m).

Marine Zones  Intertidal Zone  Coastal zone (from shore to continental shelf - contains 90% of all oceanic species)  Open sea - a) euphotic zone - low nutrients, high p.s., high O2 a) euphotic zone - low nutrients, high p.s., high O2 b) bathyal zone - no p.s. - lots of migration c) abyssal zone - dark, lots of nutrients, low O2 b) bathyal zone - no p.s. - lots of migration c) abyssal zone - dark, lots of nutrients, low O2

The Coastal Zone Figure 6-5

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 - brackish water. Figure 6-7

Fig. 6-6, p. 130

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  Nurseries  Filters  Sponges  Recreation

Rocky and Sandy Shores: Living with the Tides  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

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

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  Littoral zone (near shore, shallow, with rooted plants - lots of biodiversity)  Limnetic zone (open, offshore area, sunlit - main p.s. portion of lake - lots of O2)  Profundal zone (deep, open water, too dark for photosynthesis - low O2)  Benthic zone (bottom of lake, nourished by dead matter - lots of decomposers).

Lakes: Water-Filled Depressions Figure 6-15

Lakes: Water-Filled Depressions Epilimnion - upper layer - warm water, high O2 Epilimnion - upper layer - warm water, high O2 Thermocline - rapid temp. change Thermocline - rapid temp. change Hypolimnion - cold, dense bottom layer - low O2 Hypolimnion - cold, dense bottom layer - low O2 Fall overturn - surface water cools to 39 degrees, becomes denser, sinks - thermocline disappears Fall overturn - surface water cools to 39 degrees, becomes denser, sinks - thermocline disappears Spring overturn - surface water warms to 39 degrees, sinks - lake becomes homogeneous Spring overturn - surface water warms to 39 degrees, sinks - lake becomes homogeneous

Effects of Plant Nutrients on Lakes: Too Much of a Good Thing  Oligotrophic - new lake, few nutrients  Eutrophic - old lake, lots of nutrients (can be natural or cultural) Figure 6-16

Freshwater Streams and Rivers: From the Mountains to the Oceans  Watershed/drainage basin  Floodplain Figure 6-17

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 1900.

Freshwater Inland Wetlands: Vital Sponges  Prairie Potholes  Cypress swamps  Freshwater marshes 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, 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  Ex. - Lake Okechobee Figure 6-19