Chapter 8 - Aquatic Environments
A. Saltwater and freshwater cover 71% of the earth’s
surface.
B. Salinity of the water determines the major types of
organisms in aquatic environments.
C. Four major types of organisms in aquatic systems:
1. Plankton are free-floating, generally one-celled
organisms.
Three major types of plankton: phytoplankton (plant
plankton), zooplankton (animal plankton) and
ultraplankton - photosynthetic bacteria – 2
micrometers wide.
2. Nekton - fish, turtles and whales
3. Benthos are bottom dwellers - barnacles, oysters,
worms, lobsters and crabs
4. Decomposers
D. Three layers of aquatic life zones: surface, middle,
bottom.
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1. Temperature, sunlight, dissolved oxygen D.O., and
nutrient availability determine types and numbers of
producers found in these zones.
2. Photosynthesis is confined to the upper layer –
euphotic zone or photic zone – at lower depth
respiration from animals replaces photosynthesis
Turbidity –cloudiness of water. Can be caused by
algal blooms in the euphotic zones of lakes
*List the ecological an economic services of marine
ecosystems
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Saltwater Life Zones
A. Oceans have three major life zones: coastal and open
ocean
1. The coastal zone interacts with the land – highly
affected by human activities.
- High NPP per unit area - 10% of the oceans and
90% of all marine species.
- sunlight and nutrients flow from land.
- extends from top of high water mark out to the
edge of the continental shelf.
- subject to tidal rhythms, runoff from land, and
seawater that mixes with freshwater and nutrients.
- Mangrove forest swamps grow in sheltered regions
of tropical coasts.
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- estuaries (where rivers and sea meet) make
nutrients available due to constant stirring of bottom
sediment.
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- they filter toxic pollutants, filter excess plant
nutrients, reduce storm damage and provide nursery
sites for aquatic species.
- 1/3 have already been lost by degradation.
- Intertidal zone – area of shoreline between high and
low tide organisms need several adaptations for this
habitat (waves, temp, salinity) and have specialized
niches (pg. 131- 133) –
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Barrier beaches – gentle sloping and sandy
- Barrier islands are low, narrow sandy, islands that
form offshore from a coastline.
These help protect the mainland, estuaries, and
coastal wetlands from heavy storm damage.
(list the various issues with people living on these
islands).
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- Coral reefs in shallow coastal tropical oceans
support a very diverse ecosystem.
- They grow slowly and are vulnerable to
damage.
- Coral bleaching occurs if temperature increases
1degree over maximum range
(List the various threats to coral reefs)
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Ocean warming
Soil erosion
Algae growth from fertilizer runoff
Mangrove destruction
Bleaching
Rising sea levels
Increased UV exposure
Damage from anchors
Damage from fishing and diving
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2. The open sea is divided into vertical zones based on
light.
a. The euphotic zone - floating phytoplankton carrying
on photosynthesis – low nutrient levels
D.O. level is high. swordfish, shark and bluefin tuna.
b. The bathyal zone is the dimly lit middle zone; no
producers. Zooplankton and smaller fish
3. The abyssal zone is dark, very cold with little
dissolved oxygen. The nutrients from above –marine
snow – feed deposit feeders and nutrients on the ocean
floor – feed filter feeders.
hydrothermal - specialized bacteria feed on
chemical nutrients
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*Low average primary productivity and NPP occurs,
but oceans are so large they make the largest
contribution to NPP overall.
* 45% of the world population lives along coasts. Over
half of US population lives near the coast.
List natural capital degradation of marine ecosystems
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Half of coastal wetlands lost
to agriculture and urban
development
Over one-third of mangrove
forests lost to agriculture,
development, and
aquaculture shrimp farms
Beaches eroding because of
coastal development and
rising sea level
Ocean bottom habitats
degraded by dredging and
trawler fishing
At least 20% of coral reefs
severely damaged and 30–
50% more threatened
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Freshwater Life Zones
Standing (lentic) bodies - lakes, ponds and wetlands
Flowing (lotic) systems - streams and rivers.
*List the ecological and economic services of
Freshwater ecosystems
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Lakes - feed by rainfall, melting snow, streams
Four zones
Littoral area near shore with rooted plants
Limnetic zone is open, sunlit water near shore most
productive area for food and oxygen production.
Profundal zone is deep open water too dark for
photosynthesis less oxygen.
Benthic zone -decomposers and detritus feeders.
Sediment washing and dropping detritus feed this
area.
Deep layers become stratified by temperature – no
mixing
During fall and spring turnover of water brings up
nutrients, re-oxygenates bottom levels, and evens out
water temperature.
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Lakes are described by amount of plant nutrients.
oligotrophic lake
eutrophic lake
mesotrophic lakes
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Streams
Watershed - surface water flows into streams and
rivers and the area it drains
Three aquatic life zones along stream flow
1. source zone
- narrow and fast moving.
- large amounts of oxygen from air
- plants are attached to rocks. not very productive.
- fallen debris from trees add most productivity
2. The transition zone
- wider, deeper streams, flow down gentler sloped.
- warmer, with more nutrients and support more
producers – more algae
- slightly lower dissolved oxygen.
3. The floodplain zone
- wider, deeper rivers
- water temperature is warmer, less dissolved oxygen
is present and flow is slower
- large numbers of producers such as algae,
cyanobacteria, and rooted plants.
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Streams are fairly open ecosystems and receive many
nutrients from surrounding lands.
(List some of these sources)
Inland wetlands - swamps, marshes, prairie potholes,
floodplains
- number of days of saturation, soil type, and
vegetation determine wetland
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- wetlands provide ecological services such as filtering
toxic wastes/pollutants, absorbing/storing excess
water from storms and providing habitats for a
variety of species.
 List the four major impacts humans have on freshwater
ecosystems
 Cultural eutrophication:
 Human inputs of nutrients from the atmosphere
and urban and agricultural areas can accelerate
the eutrophication process – runoff of fertilizers,
livestock, sewage – excess algae – die and
decomposers use up oxygen
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