Chapter 7 Aquatic Biodiversity

      

Euphotic zone

- layer of water where sunlight can penetrate What is the concentration of dissolved O 2 at the surface ? at 1000 m ?

 What is the concentration of dissolved CO 2 at the surface? at 1000 m ?

Explain why dissolved O 2 high near the surface.

levels are so Graph page 146 Explain why dissolved CO 2 so low near the surface.

levels are Explain why the O 2 becomes less concentrated and the CO 2 becomes more concentrated in deeper waters.

How would you expect this graph to change at night ? Why ?

How should the pH change with depth during the day ? Explain.

Aquatic Life Zones



Saltwater or Marine



Freshwater

 · Estuaries  · Lakes and ponds  · Coastlines  · Streams and  · Coral reefs  · Coastal marshes  · Mangrove swamps  · Ocean rivers  · Inland wetlands

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

Natural capital:

a healthy coral reef in the Red Sea covered by colorful algae These diverse and productive ecosystems are being damaged and destroyed at an alarming rate.

Fig. 6-1a, p. 126

Bleached Coral Reef

That has lost most of its algae because of changes in the environment (such as cloudy water or too warm temperatures). With the algae gone, the white limestone of the coral skeleton becomes visible. If the environmental stress is not removed and no other alga species fill the abandoned niche, the corals die.

Fig. 6-1b, p. 126

Coral Reefs

-built from accumulated layers of calcium carbonate, CaCO3 laid down by relatives of sea anemones.

• 1. Most of these organism require warm shallow water • 2. Many live in a symbiotic relationship with green algae known as

zooxanthellae

• 3. A very diverse marine environment • 4. The Great Barrier Reef off the coast of Australia is one of the largest

Value of coral reefs

• Provide valuable habitat • Provide humans with seafood • Pharmaceuticals • Recreation/tourism dollars

Human Impacts

• Covered with silt from inland logging • In 1980’s coral bleaching occurred stressed corals expelled

zooxanthellae

algae • Thought to be related to warming of the seas.

Corals can recover because • 1. Hold a secret reserve of algae • 2. Can take on other algae species when one species leaves • 3. Seasonally lose up to 75% of algae • Diving and snorkeling Overfishing • Agricultural and industrial pollutants in runoff.

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.

Natural capital:

the ocean planet. 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)

Ocean hemisphere Land –ocean hemisphere

and 50% of its land –ocean hemisphere (right). Freshwater systems cover less than 1% of the earth’s surface.

Fig. 6-2, p. 127

AQUATIC ENVIRONMENTS Figure 6-3

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.

The Coastal Zone

The Open Ocean

Life Zones

Euphotic Zone

1.Light

2. Dissolved Oxygen 3. Nutrients upwellings 4.Organisms

Bathyal Zone

1.Light

2. Organisms

Abyssal Zone

1.Light

2.Oxygen

3. Nutrient levels Figure 6-5

Marine Ecosystems  Scientists estimate that marine systems provide $21 trillion in goods and services per year – 70% more than terrestrial ecosystems.

Figure 6-4

Major Human Impacts



Salt Marshes, Mangrove Forests, Sea-grass Meadows

 Filled in for coastal development  Aquaculture of shrimp 

Beaches-

Erosion 

Benthic Habitat-

 Bottom trawlers 

Coral Reefs-

 Ocean warming, pH changes associated with global warming.

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

Estuaries &Associated Coastal Wetlands

 Located at the mouth of rivers and streams  Fresh and salt water mix  Highest NPP of any ecosystem because  · 1. Nutrient runoff from land  · 2. Tides circulate nutrients and remove wastes  · 3. Light penetrates the shallow water  · 4.Plant carry out photosynthesis and trap detritus  Organisms must deal with daily changes in temperature and salinity.

Saltwater marshes

 Found associated with temperate estuaries  Dominated by salt tolerant grasses  Important services  · 1. Habitat  · 2. Sediment and pollution trapping  · 3. Storm buffering  Most are being covered over for coastal development

Mangrove Forests  Are found along about 70% of gently sloping sandy and silty coastlines in tropical and subtropical regions.

Figure 6-8

Mangrove Forests

-tropical equivalent of saltwater marsh  Network of roots of the mangrove trees are important nurseries of many commercially important fish and shellfish (shrimp)  Branches of mangrove trees provide important habitat for nesting birds: pelicans, herons, egrets.

 Roots stabilize submerged soil preventing coastal erosion  Storm buffer     · Being harmed by: Logging Coastal development Aquaculture

Intertidal Zone

- between high and low tide  · Organisms must contend with changing levels of water  In rocky shoreline habitat, most organisms are anchored in some way and have a  way to seal off their bodies to prevent moisture loss when the tide goes out.

Most sandy beach organisms either burrow in the sand or travel in and out with the tide.

The importance of

sea grass

 High NPP make them important producers in shallow water  Roots stabilize sediments reducing erosion  Provide food and habitat for many marine species, sea turtles, manatees, ducks and geese  Chinook salmon and eelgrass

Kelps Beds

 Formed from species of marine algae  Many are anchored to the bottom and have air filled bags to allow the upper part of the plant to float to the top  equivalent to the forest biome on the land  Kelp beds or forests provide habitat and food for many 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.

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

Biological Zones in the Open Sea: Light Rules 

Euphotic zone

: brightly lit surface layer.  Nutrient levels low, dissolved O 2 photosynthetic activity.

high, 

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 O 2 .

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.  Ponds are generally shallow and have only one zone-light reaches to the bottom 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).



Limnetic zone

(open, offshore area, sunlit).



Profundal zone

photosynthesis).

(deep, open water, too dark for 

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.

 What causes this overturning?

Sunlight Green frog Painted turtle Blue-winged teal Muskrat Pond snail Littoral zone Diving beetle Yellow perch Bloodworms Limnetic zone Profundal zone Benthic zone Plankton Northern 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.

Physical Properties of water

 Approaches maximum density at 4oC  At temperatures cooler than 4oC water becomes less dense and it floats  and freezes as temperatures drop to 0oC  At temperatures greater than 4oC water becomes less dense and it floats

Seasonal Overturn in Lakes 

Fall Overturn-

 Surface waters  cool to 4 o C (39 o F)  and descend to  the bottom  Nutrients  Oxygen levels 

Spring Overturn-

 Surface waters  warm to 4 o C and  descend through  the colder less  dense waters  beneath.

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 snow Source Zone Lake Glacier Rapids Waterfall Tributary Flood plain Oxbow lake Salt marsh Delta Deposited sediment Ocean Transition Zone Sediment Water 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