Transcript No Slide Title

Aquatic Ecology
Factors Affecting Aquatic Ecosystems
Light decreases with depth.
- Only 1% of light below 200 m
- No light below 1000 m
Turbidity (cloudiness) affects light.
Temperature decreases with depth due to decreasing
energy input from sun.li
Sea level
0
50
Euphotic
Zone
Estuarine
Zone
Depth in
meters
100
Continental
shelf
200
Photosynthesis
Sun
Open
Sea
500
Bathyal Zone
1,000
Twilight
High tide
Low tide
Coastal
Zone
1,500
2,000
Abyssal
Zone
3,000
4,000
5,000
10,000
0
5
10
15
20
Water temperature (°C)
25
30
Darkness
Water temperature drops
rapidly between the
euphotic zone and the
abyssal zone in an area
called the thermocline .
Discuss with your table partner:
Study the pattern of oxygen
with depth.
The red line represents
approximately the start of the
aphotic (no light) zone.
What process accounts for the depletion of
oxygen at this depth?
Decomposition of organic matter (most of which comes
from above) by aerobic organisms depletes the oxygen.
Why is the level of oxygen higher closer to the
surface (besides diffusion of O2 into the H2O)?
Enough light for photosynthesis which adds oxygen.
Discuss with your table partner:
Temperature and pressure also affect the levels of
dissolved oxygen and other gases.
How does temperature affect the amount of dissolved
gas?
Temperature varies inversely with maximum DO.
How does pressure affect the amount of dissolved
gas? (Consider what happens when you release the
pressure on a sealed bottle of soda.)
Pressure varies directly with maximum DO. More
dissolved gas at higher pressure.
Factors Affecting Aquatic Ecosystems
Nutrient availability
most limiting macronutrients are phosphorus (P) &
Limiting micronutrients include iron (Fe); essential for
growth of phytoplankton.
A failed experiment to increase the carbon stored in the
ocean by seeding it with iron to stimulate phytoplankton
growth did not work because it also caused a bloom of
toxic diatoms.
http://permaculturenews.org/2012/11/07/oceanfertilization-promotes-toxic-algae-in-haida-gwaii/
Discuss with your table partner:
Study the pattern of nitrate levels
with depth.
What accounts for the increase in
nitrates, which corresponds
approximately with the lower
levels of oxygen?
Decomposition of materials (much of which falls
from above) provide available nitrates.
Why are lower levels of nitrates not available
closer to the surface?
Greater rate of uptake of nitrates and other nutrients.
Phytoplankton use up much of the nitrates.
Discuss with your table partner:
Note that in most locations, the surface has low levels of
nitrates. Relate the areas of higher nitrates off the west
coast of South America to our weather unit.
Location
of upwelling
bring
nutrient-rich
water from
How
do areas
of high that
nitrates
along
coast of South
deeper ocean
America
relate.to weather unit?
Life zones of the Ocean
Vertical Zones:
Euphotic Zone: 0 - 200 m
Greatest amount of light.
(Eu = good, photo = light)
Bathyl Zone:
200 - 4500 m
Abyssal Zone:
4500 - 11,000
“marine snow” – dead organisms
from above
(Abyss= the deep)
Hadal Zone:
> 6000m
Benthic Zone =
Region along bottom
of sea
Benthos =
bottom dwelling sea
creature.
Pelagic Zone = open sea
Region that is not near
the shore or close to the
bottom.
NATURAL CAPITAL
Marine (salt water) Ecosystems
Marine Ecosystems
Ecological
Services
Economic
Services
Climate moderation
Food
CO2 absorption
Animal and pet feed
Nutrient cycling
Pharmaceuticals
Waste treatment
Harbors and
transportation routes
Reduced storm impact
(mangroves, barrier
islands, coastal
wetlands)
Habitats and nursery
areas
Genetic resources
and biodiversity
Scientific information
Coastal habitats for
humans
Recreation
Employment
Oil and natural gas
Minerals
Building materials
Estuaries & Coastal Wetlands
Estuary: where seawater mixes with freshwater from land,
generally at the mouth of a river
Coastal wetland: areas of coastal land covered all or part of the
year with salt water
Brackish= mix of salt water and fresh
Importance
• nutrient rich and high
primary productivity
• nurseries for fish & other
aquatic animals
• waterfowl & shorebird
breeding areas
• filter water pollutants
Estuaries & Coastal Wetlands
Human Impacts
• world has lost over
half of its estuaries &
coastal wetlands
• percentage lost in the
U.S. even higher.
Most lost to coastal
development
• causes of
degradation: urban
runoff, sewage
treatment plant effluent,
sediment & chemical
runoff from agricultural
lands
Barrier Islands
Barrier Islands: long, thin, low offshore islands of
sand that run parallel to the shore. They do not
remain stationary over time.
Importance
• protect mainland
from offshore
storms
• shelter inland
bays, estuaries,
& wetlands
Barrier Islands
Human Impacts
• Development on barrier islands
– destroys dunes & dune
vegetation
– causes beach erosion
(through trying to keep
Ocean City, MD
islands in place)
– destroys or disturbs wildlife habitat (e.g., some
endangered birds nest on barrier islands)
Protecting barrier islands
– jetties & seawalls
– beach replenishment
– replanting dune vegetation, controlling development
Coral Reefs
• reefs formed by mutualism
between polyps & algae
• reefs built as colonies of polyps
secrete limestone; hard deposits
remain when the polyps die
• reefs located in coastal zones of
tropical oceans
Coral Reefs
Importance
• high biodiversity: “tropical
rain forests of the ocean”
• protect coastlines from
storms & high waves
• nurseries for many fish
species
• disappearing
Vulnerability
• slow growing
• easily disturbed
• thrive only in clear water
Human Impacts
• sediment runoff & effluent
• increased UV radiation (ozone
depletion)
• fishing with cyanide & dynamite
Mangrove Swamps
• Salt-tolerant trees & shrubs
• Warm tropical coastal areas
• Too silty for coral reefs
• Protect coastlines from
erosion, especially during
typhoons & floods
• Trap nutrient-rich sediments
• Provide habitat for fish, birds,
invertebrates, and plants
Freshwater Ecosystems
Lakes
Littoral zone: shallow area near the shore, to the depth at which
rooted plants stop growing.
Limnetic zone: open, sunlit, surface layer away from the shore.
Depth is the limit of light penetration.
Profundal zone: deep, open water where there is no light
penetration.
Benthic zone: the bottom of a lake; inhabited by insect larvae,
decomposers, & clams.
Sunlight
Painted
turtle
Blue-winged
teal
Green
frog
Pond
snail
Muskrat
Littoral zone
Plankton
Diving
beetle
Northern
pike
Yellow
perch
Bloodworms
NATURAL CAPITAL
Freshwater Systems
Ecological
Services
Climate moderation
Nutrient cycling
Economic
Services
Food
Drinking water
Waste treatment
Irrigation water
Flood control
Groundwater
recharge
Hydroelectricity
Habitats for many
species
Transportation
corridors
Genetic resources
and biodiversity
Recreation
Scientific information
Employment
Discuss with your table partner:
Describe the normal pattern of temperature (and
density) with depth in a lake in the summer. How
does this pattern result in stratification (layers)?
Upper layer is warmer. Since this warmer layer
is less dense it remains on the top.
•epilimnion: warm, upper layer
epi= above
•thermocline: zone where
temperature changes rapidly
•hypolimnion: colder, denser
lower layer hypo= below
Discuss with your table partner:
In temperate locations, there is often a turnover over
spring
fallSpring
(temperate
zone
lakes)
water
in &the
and Fall,
which
can help
redistribute nutrients and oxygen. Explain why these
overturns occur.
When the surface water cools in the Fall it becomes
more dense and sinks.
In the Spring, as ice melts it becomes more dense
and sinks.
Video: Overturn in Temperate Lakes
http://www.youtube.com/watch?v=X26ocQkhNH4
Atmosphere vs. Bodies of Water
In the atmosphere, there is more heating at the
bottom. (Not much blocking of light by the
atmosphere).
- This heating at the bottom creates
convection currents such as the Hadley Cells.
In bodies of water, most of the heating is at the
surface since light can not penetrate very far
into the more dense water.
- This often leads to thermal stratification.
Lands covered with
Wetland functions
Wetlands
• wildlife habitat, especially for waterfowl & amphibians
• filter sediments & pollutants from runoff , “nature’s kidneys”
• flood attenuation
Human impacts:
• some states have lost over 90% of their wetlands by filling or draining.