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

Low tide Coastal

Zone

Open

Sea

Depth in

meters

High tide Sun

Sea level

50 Estuarine

Zone

Euphotic

Zone 100

Ph

oto

syn

the

sis

Continental

shelf 200

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

Dark

ness

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

http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/http://permaculturenews.org/2012/11/07/ocean-fertilization-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:

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 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.

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

Recreation Habitats 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 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

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

Sunlight

Painted

turtle

Blue-winged

teal

Green

frog Muskrat

Pond

snail Littoral zone Plankton

Diving

beetle Northern

pike

Yellow

perch Bloodworms

NATURAL CAPITAL

Freshwater Systems

Ecological

Services

Economic

Services

Climate moderation Food

Nutrient cycling Drinking water

Waste treatment Irrigation water

Flood control

Hydroelectricity Groundwater

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 with

depth in a lake in the summer. How does this

pattern generally 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

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 Lakes http

://ww

w.y

outu

be.c

om

/watc

h?v=

X2

6ocQ

khN

H4

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.

Wetlands Lands 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.