Transcript Aquatic Ecology: Biodiversity in Aquatic Systems

Aquatic Ecology:
Biodiversity in Aquatic
Systems
Miller Chapter 7
Coral Reefs
• Coral reefs are formed by secretions of calcium
carbonate from millions of polyps.
• Function to:
– Remove CO2 from the atmosphere
– Serve as a natural barrier from erosion & replenish sand
to nearby beaches
– Provide food, shelter, etc to 25% of all marine species
& 65% marine fish species
– Provide resources to world’s poorest countries
(economic & food)
– Support fishing & tourism industries
Section 7-1
Salinity
• The amount of various salts such as sodium
chloride [NaCl] dissolved in a given volume of
water.
• Dictates what types of organisms will live in
an environment.
• As a result aquatic life zones are divided into:
– Saltwater or Marine
– Freshwater
Saltwater or Marine
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Estuaries
Coastlines
Coral reefs
Coastal marshes
Mangrove swamps
Oceans
Freshwater
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Lakes
Ponds
Streams
Rivers
Inland wetlands
Living in Water
Advantages
Disadvantages
- Physical support from water
buoyancy
- Fairly constant temperature
- Nourishment from
dissolved nutrients
- Water availability
- Easy dispersement of
organisms, larvae, & eggs
- Less exposure to harmful
UV radiation
- Dilution & dispersion of
pollutants
- Low/small range of
tolerance
- Exposure to dissolved
pollutants
- Fluctuating population size
for many species
- Dispersion separates many
aquatic offspring from
parents
Major Organisms
Phytoplankton
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Description – Small drifting plants
Niche – Producers that support most
aquatic food chains
Example – Cyanobacteria & many
types of algae
Major Organisms con’t
Zooplankton –
•Description
•Non-photosynthetic bacteria primary consumers
(herbivores); feed on phytoplankton
•Secondary consumers – feed on other
zooplankton
•Niche – food stock for larger consumers
•Example – krill;
small crustaceans
Major Organisms con’t
Nekton
• Description – larger, strong-swimming
consumers
• Niche – top consumers in the aquatic
ecosystem
• Example – fish, turtles,
and whales
Major Organisms con’t
Benthos
• Description – bottom-dwelling
creatures
• Niche – primary consumers,
decomposers
• Example
– Barnacles & oysters
• anchor themselves
– Worms
• burrow
– Crabs and lobsters
• walk along bottom
Major Organisms con’t
Decomposers –
• Bacteria that break down organic
compounds into simpler compounds for
producers to use.
Aquatic Organisms and Systems
• Key Characteristics:
1. More flexible boundaries than
terrestrial ecosystems  harder to
count & manage populations in
aquatic ecosystems
2. More complex food chains/webs
3. More difficult to monitor & study
because of size & location
Layers of Aquatic Life
• Surface, middle, & bottom.
• Each has a specific:
– Temperature
– Amount of sunlight
– DO content – amt. can vary depending on
temp, # of producers, # of consumers &
decomposers, & deep ocean circulation
– Nutrient availability
Euphotic Zone
• Upper layer
– Photosynthesis can occur here because
sunlight can penetrate.
– Algae growth can hinder photosynthesis
and decrease euphotic zone
• Bottom-dwellers reproduce slowly
because food is limited; vulnerable to
depletion from over fishing
Section 7-2
Saltwater Life Zones
• Marine waters cover 71% of the
planet.
• Oceans make up 99.5% of world’s
habitable volume, but only 5% has
been explored.
• Oceans contain 250,000 known
species of marine plants & animals.
Major Life Zones in Oceans
1. Coastal Zone
2. Open Sea
Coastal Zone
• Warm, nutrient-rich, shallow water area
from the coast to the shallow edge of the
continental shelf
– It is highly susceptible to harm from
human activities.
– It contains 90% of all marine species.
– Most ecosystems here have a high NPP per
unit area because of the amount of sunlight
and plant nutrients found in the zone
Estuaries
• A partially
enclosed area of
coastal water
where salt &
fresh water mix.
It is an ecotone.
Coastal Wetlands
• Land areas
covered with
water all or
most of the year
Estuaries & Coastal Wetlands
• Include river mouths, inlets, bays, sounds,
mangrove forest swamps, salt marshes in
temperate zones; they are some of the most
productive ecosystems due to constant
renewal of nutrients through water
movement.
Intertidal Zone
• Also called Littoral Zone
• Area of shoreline between high & low tides
– This is a tough area to live in because it is constantly
changing. Organisms must be able to resist being swept into
the ocean with the tides or crushed, immersed during high
tides, left high & dry at low tides, and salinity changes.
– Ex. frogs, snails, insects, fish, cattails, and water lilies.
Intertidal Zone con’t
• Rocky Shores
– areas along coasts pounded heavily by
waves
• Sandy shore (barrier beaches)
– gently sloped areas with niches for
different marine organisms; most dig in,
bury, or hide in shells
Barrier Islands
• Long, thin, low offshore islands of
sediments that generally run parallel to
the shore
• Absorb a lot of the energy from storm
waves.
Coral Reefs
• Slow growing, easily disrupted, thrive in
warm, clear, shallow salt water.
• Require certain temp, salinity.
Coral Reefs con’t
• Humans are their greatest threat:
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Ocean warming
Soil erosion
Algae growth from fertilizer runoff
Destruction of mangroves
Bleaching (due to temp increases)
Rising sea levels
UV exposure from O3 depletion
Harvesting of reef fish by cyanide & dynamite
Coral removal for building material, aquariums & jewelry
Damage from divers & ships
• A lot are now protected as national reserves or parks.
Coral Reefs con’t
Figure 7-16 Miller p 154
Main groups of Organisms
1. Attached organisms (coral, algae,
sponges)
2. Fishes
3. Small organisms that bore into, attach
to, or hide inside of the reef
Open Sea
• Area from the edge of the continental
shelf and the rest of the sea
• The vast volume of the ocean
• Low NPP per unit area
• Contains 90% of the surface area of the
oceans and 10% of its plant and animal
life. Why do you think this is?
3 Vertical Subzones
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Based on penetration of sunlight
Euphotic zone
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Bathyal zone
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lighted upper zone
dimly lit middle zone
no photosynthesizers
zooplankton & fishes
Abyssal zone
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dark, lower zone
cold, little DO
ample nutrients on ocean floor
3 Vertical Subzones
Figure 7-7 Miller p. 148
Human Impacts on Marine Systems
• Salt marshes, mangrove forests, and sea-grass
meadows are being lost and degraded at a high rate
to make way for real estate developments.
• Coastal Wetlands are disappearing due to filling in for
agricultural and coastal developments.
• The World’s beaches are eroding rapidly because of
coastal developments and rising sea level.
• Ocean bottom habitats are being degraded and
destroyed by dredging operations and trawler boats.
Section 7-3
Freshwater Life Zones
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Water flowing on or with less than 1%
salt concentration
– Examples:
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Standing bodies of water (lakes, ponds,
inland wetlands)
Flowing bodies of water (streams, rivers)
Lakes
• Large, natural, standing bodies of water
formed from precipitation & runoff
filling depressions in earth’s surface
• Can have 4 zones:
– Littoral Zone
– Limnetic Zone
– Profundal Zone
– Benthic Zone
Littoral Zone
• Shallow, sunlit water near the shore
• Stops at root depth of plants
• Lots of biodiversity
**Ponds only have one zone (euphotic
zone)
Limnetic Zone
• The open, sunlit water surface layer
away from the shore
• Extends as far as light penetrates
• Most of the lakes food & oxygen is
produced here
Profundal Zone
• Deep, cold open water
• Too dark for photosynthesis  low
oxygen content
Benthic Zone
• Bottom of the lake
• Only organisms that tolerate cold water
with poor O2 quality.
Oligotrophic Lake
• Newly formed lake with poor nutrient levels
• Often deep, crystal clear water with steep
banks and small populations of
phytoplankton & fish
Little Shore Vegetation
Clear Water
Sparse Fish Population
Sand, gravel rock
bottom
Eutrophic Lake
• A shallow lake with murky brown or
green water
• Large or excessive supply of nutrients
(nitrates & phosphates)
• Poor visibility; high NPP
Much Shore Vegetation
Murky Water
Dense Fish Population
Sand, silt, clay bottom
Mesotrophic Lake
• A lake that falls between the two
extremes
Seasonal Changes in Water Temp
• Water is densest at 4oC
• Less dense at 0oC  ice floats on water
Summer
• This causes thermal stratification of deep lakes
during the summer
– Epilimnion – upper layer of warm water with high DO
– Thermocline (metalimnion)– where the water temperature
changes rapidly with depth and with moderate DO content
– Hypolimnion – lower layer of colder, denser water with low
DO content
** The thermocline acts as a barrier for nutrient transfer
between the epilimnion & the hypolimnion during the
summer months**
Fall
• Thermocline disappears creating a
mixing called fall overturn, which
brings:
–Nutrients from bottom sediments to
the surface
–Brings DO at surface to the bottom
–Allows fish to live at various depths
Winter
• Lake separates into layers of different
densities
Spring
• Surface water reaches max density
when it reaches 40C and sinks through
& below colder water
• Winds cause mixing of surface & bottom
waters  surface DO cycled to the
bottom (spring overturn)
• Temperature & DO are same at all
depths
Seasonal Changes
Figure 7-22 Miller p.
159
Streams and Rivers
• Surface Water – precipitation that does not
evaporate or sink into the ground
• Runoff –surface water that flows into
streams
• Watershed (drainage basin) – surface that
delivers runoff, sediment, & dissolved
substances into streams
• Water flow:
– Small streams  Rivers  Ocean
Zones of Water Flow Down Mountains
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Source zone
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Transition zone
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head water or mountain highland streams of
cold, clear water rush over waterfalls and rapids;
high DO here; algae, mosses, cold-water fish
with flat bodies
headwater streams merge to form wider, deeper
streams that flow down gentle slopes; warmer
water supports more producers; lower DO
content
Floodplain zone
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streams join into wider, deeper rivers running
across broad, flat valleys; high temps & lowest
DO content; muddy water with high silt content
Zones of Water Flow Down Mountains
Figure 7-23 Miller p. 160
Inland Wetlands
• Lands covered with fresh water all or part of
the time and located away from coastal areas.
• Includes:
– Marshes
– Swamps
– Prairie potholes – depressions carved by glaciers
– Waterlogged soils, which tends to accumulate peat
– Floodplains
– Bogs
– Fens
– Wet arctic tundra
• Wetlands have important ecological &
economic roles and should be protected
Marsh
Swamp
Prairie Pothole
Floodplain
Bog
Human Impacts on
Freshwater Systems
• Disruption by dams or canals
• Flood levees altering habitats
• Pollution
Section 7-4
Sustainability of Aquatic Ecosystems
• Everything is connected! Everything that
occurs (pollute, harms, etc) in watersheds is
felt in streams, rivers & lakes that they feed
into.
• Natural processes purify water, nutrients
cycle in & out, and populations of
organisms can be replenished given
adequate time.