Aquatic Ecology

Factors Affecting Aquatic EcosystemsLight 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

Low tideCoastal ZoneOpen Sea

Depth in meters

High tideSun

Sea level

50Estuarine Zone

Euphotic Zone

100

Ph

oto

syn

thes

is

Continental shelf200

Bathyal Zone 500

1,000

Tw

ilig

ht

1,500

Water temperature drops rapidly between the euphotic zone and the abyssal zone in an area called the thermocline .

Abyssal Zone 2,000

3,000

4,000

Dar

knes

s

5,000

10,000

0 5 10 15 20 25 30

0

Water temperature (°C)

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?

Why is the level of oxygen higher closer to the surface (besides diffusion of O2 into the H2O)?

Decomposition of organic matter (most of which comes from above) by aerobic organisms depletes the oxygen.

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?

How does pressure affect the amount of dissolved gas? (Consider what happens when you release the pressure on a sealed bottle of soda.)

Temperature varies inversely with maximum DO.

Pressure varies directly with maximum DO. More dissolved gas at higher pressure.

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/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/

Factors Affecting Aquatic Ecosystems

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:

How do areas of high nitrates along coast of South America relate to weather unit?

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 that bring nutrient-rich water from deeper ocean .

Life zones of the OceanVertical Zones:

Euphotic Zone: 0 - 200 mGreatest 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 seaRegion that is not near the shore or close to the bottom.

Marine Ecosystems

Economic Services

Climate moderation Food

CO2 absorption Animal and pet feed

Nutrient cycling Pharmaceuticals

Harbors and transportation routes

Waste treatment

Reduced storm impact (mangroves, barrier islands, coastal wetlands)

Coastal habitats for humans

RecreationHabitats and nursery areas Employment

Genetic resources and biodiversity

Oil and natural gas

Minerals

Scientific information Building materials

Ecological Services

NATURAL CAPITAL

Marine (salt water) Ecosystems

Importance

•nutrient rich and high primary productivity

•nurseries for fish & other aquatic animals

•waterfowl & shorebird breeding areas

• filter water pollutants

Estuaries & Coastal WetlandsEstuary: 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

Human Impacts

Estuaries & Coastal Wetlands

• 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: 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

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

Barrier Islands

Ocean City, MD

• 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

Coral Reefs

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

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.

Freshwater Ecosystems

SunlightPainted turtle Blue-winged teal

Green frog

Muskrat

Pond snail

Littoral zone Plankton

Limnetic zoneProfundal zoneDiving beetle

Benthic zone

Northern pike

Yellow perch

Bloodworms

NATURAL CAPITAL

Freshwater Systems

Ecological Services Economic Services

Climate moderation Food

Nutrient cyclingDrinking water

Waste treatmentIrrigation water

Flood control

HydroelectricityGroundwater recharge

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 layerepi= above

•thermocline: zone where temperature changes rapidly

•hypolimnion: colder, denser lower layer hypo= below

spring & fall (temperate zone lakes)

Discuss with your table partner:In temperate locations, there is often a turnover over

water in the Spring 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 Lakeshttp://w

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Atmosphere vs. Bodies of WaterIn 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.

WetlandsLands covered with

Wetland functions

• 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.