Chapter 7 Biodiversity in Aquatic Systems

Key Concepts  Factors that influence aquatic systems  Saltwater life zones  Freshwater life zones  Human activities that affect aquatic systems

Mangroves Coral reefs Rivers Lakes

Aquatic Life Zones Aquatic life zones = aquatic biomes 2 major types 2 major types 1. saltwater or marine: estuaries, coastlines, coral reefs, coastal marshes, mangrove swamps, oceans 2. freshwater: lakes, ponds, streams, rivers, inland wetlands

What lives in water?  Phytoplankton: plant plankton; producers  Zooplankton: animal plankton; herbivores  Nekton: consumers; strong swimmers; fish, whales, turtles  Benthos: bottom-dwellers; barnacles, worm that burrow, lobsters, crabs  Decomposers: bacteria

Advantages Water buoyancy Constant temperature Nourishment from dissolved nutrients Easy dispersal Less exposure to UV radiation Dilution of pollutants Disadvantages Can tolerate a narrow range of temp. Exposure to pollutants Fluctuating population size Aquatic offspring separated from parents © 2004 Brooks/Cole – Thomson Learning

What Factors Limit Life?  Temperature  Access to sunlight for photosynthesis (mainly euphotic zone)  Dissolved oxygen: high near surface (photosynthesis), low in deep, cool water  Availability of nutrients: fewer nutrients available in deep area (lower net primary productivity )

Saltwater Life Zones  Oceans cover 71% of the planet  Oceans contain 250,000 species of plants and animals  Oceans provide many ecological and economic services

Figure 7-6 Page 147 Marine Systems Ecological Services Climate moderation CO 2 absorption Nutrient cycling Habitats and nursery areas for marine and terrestrial species Biodiversity Economic Services Animal and pet feed Pharmaceuticals Harbors and transportation routes Recreation Employment Offshore oil and natural gas Minerals Marine Systems

Ocean Life Zones 1. Coastal Zone: shallow, nutrient-rich, warm, extends to continental shelf, 90% all ocean species (high or low NPP?) 2. Euphotic Zone: upper zone, photosynthesis, low nutrient levels, dissolved O 2 high 3. Bathyal Zone: dimly lit, no producers 4. Abyssal Zone: dark, deep ocean, dissolved O 2 low

Coral Reefs  Form in clear, coastal waters  Oldest, most diverse ecosystems  Complex interaction between organisms  Vulnerable to damage because: 1. Grow slowly 2. Disrupted easily 3. Thrive only in warm, clear, shallow water

Coral Reef

Ocean warming Algae growth from fertilizer runoff Rising sea levels Increased UV exposure from ozone depletion Using cyanide and dynamite to harvest coral reef fish Coral removal for building material, aquariums, and jewelry Damage from anchors, ships, and tourist divers Threats to Coral Reefs

 Coral Bleaching: whitening of corals, due to stress or death of their symbiotic protozoa (zooxanthellae), or due to the loss of pigmentation within the protozoa  Under stress, corals may expel their zooxanthellae, which leads to a lighter or completely white appearance (“bleached”)

Coral bleaching can be induced by:  increased (most commonly) or reduced water temperatures  increased solar radiation  changes in water chemistry  starvation caused by a decline in zooplankton  increased sedimentation (due to runoff)  pathogen infections  changes in salinity  wind  low tide air exposure  fishing

Highly Productive Areas  Estuaries: where saltwater mixes with freshwater (ecotone)  Coastal wetlands: land areas covered with water (river mouths, inlets, bays)  Mangroves: forest swamps; protect coastlines and coral reefs; important habitat * constant water movement stirs up nutrients, making estuaries and wetlands very productive areas

Estuary

Mangrove

Intertidal Zone  Area of shoreline between low and high tides  Stressful zone  Animals may be crushed or swept away may be immersed during high tide may be left to dry during low tide  Salinity is constantly changing  Example: rocky shores, barrier beaches

Rocky Shores and Barrier Beaches  Intertidal Zones  Both have great variety of species, lots of available niches  Rocky shores have lots of pools in rocks where animals live  Barrier Beaches-most animals survive by burrowing, digging, tunneling in the sand

Rocky Shore Beach

Barrier Beach

Barrier Islands  Long, thin, low offshore islands of sediment  Parallel to the shore  Protect mainland by dispersing storm waves (“barrier”)

Human Impact on Marine Systems  ½ world’s original wetlands (91% Ca) have been destroyed  35% mangroves destroyed  70% beaches eroding rapidly  Boats with chains/nets destroy ocean bottom habitats  27% coral reefs severely damaged  11% coral reefs destroyed  Prediction: 70% coral reefs destroyed by 2050

Megalodon Shark  Miocene Period-20 mya  60 ft long; jaws 5 ft long

Freshwater Life Zones  Less that 1% salt concentration  2 types: 1. Standing: lakes, ponds 2. Flowing: streams, rivers  Freshwater systems cover less than 1% of earth’s surface  Runoff from land provides FW zone with organic matter, nutrients, pollution

Freshwater Systems Ecological Services Economic Services Climate moderation Nutrient cycling Waste treatment and dilution Flood control Habitats for aquatic and terrestrial species Genetic resources and biodiversity Scientific information Food Drinking water Irrigation water Hydroelectricity Transportation corridors Recreation Employment © 2004 Brooks/Cole – Thomson Learning

Freshwater Life Zones  Littoral zone: shallow, sunlit water surface near shore  Limnetic zone: open, sunlit water surface away from shore; main photosynthetic part  Profundal zone: deep, open water; too dark for photosynthesis  Benthic zone: bottom of the lake, cool temp, low oxygen levels (why?)

How do Plant Nutrients affect Lakes?  Lakes are classified according to: nutrient content and productivity  Newly-formed lake = oligotrophic lake (poorly nourished); clear water  Established lake= eutrophic lake (well- nourished); murky water  Cultural eutrophication: human inputs of nutrients accelerates eutrophication

Seasonal Changes in Lakes  Thermal stratification: three distinct layers with different temperatures 1. Epilimnion: upper layer of warm water, high dissolved oxygen (warm water on top, less dense) 2. Thermocline: cooler “middle” layer, moderate levels of dissolved oxygen 3. Hypolimnion: lower layer of cold water, low concentration of dissolved oxygen (more dense)

Seasonal Changes in Lakes

Seasonal Changes in Lakes, cont.  Fall: surface water cools, thermocline disappears as warm water becomes colder (and more dense) fall overturn: brings nutrients from bottom to top, brings dissolved oxygen from surface to bottom  Winter: cold temp, water separates into different densities  Spring: surface water sinks (becomes more cold dense) spring overturn: brings nutrients from bottom to top, brings dissolved oxygen from surface to bottom

Streams and Rivers  Remember hydrologic cycle!  Runoff: precipitation that does not sink into the ground or evaporate--flows into streams  Watershed: land area that delivers runoff to a stream  Small streams join to form rivers; rivers flow downhill to the ocean (hydrologic cycle)

Stream and River--Life Zones 1. Source zone: cold, clear water (from mountains) rushes over waterfalls and rapids; dissolves large amounts of oxygen with turbulence; cold water fish and lots of algae and mosses on rocks 2. Transition zone: streams merge to form wider streams; fewer obstacles; warmer water supports more producers 3. Floodplain zone: streams move across valleys; slow-moving; warmer temp; less dissolved oxygen; muddy, lots of silt

Rain and snow Water Sediment Lake GlacierRapids Waterfall Tributary Flood plain Oxbow lake Salt marsh Delta Ocean Deposited sediment Source Zone Transition Zone Floodplain Zone

Inland Wetlands  Land covered with freshwater all or part of the time  Includes: marshes, swamps, prairie potholes (from glaciers), floodplains, bogs  Important for flood control

Freshwater marsh

Cypress Swamp

Prairie Potholes

Human Impact of Freshwater Systems  60% of world’s rivers are fragmented by dams and canals (destroys wildlife habitats by reducing water flow)  Flood control levees destroy habitats, eliminate wetlands (fish breeding grounds)  In U.S., 53% of inland wetlands have been drained or filled and covered with asphalt/concrete for buildings

How Sustainable are Aquatic Ecosystems?  Most pollutants end up in the ocean  Aquatic life zones are constantly renewed because: 1. water is purified by hydrologic cycle 2. nutrients cycle in and out 3. populations can be replenished  However, this can happen ONLY if over- polluting and over-fishing do not occur!!