13 ecosystems2 1
Transcript of 13 ecosystems2 1
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AnnouncementsMar. 9, 2011
March 8 @ 12 noonUniversity YMCA | Latzer Hall The Sustainable Student Farm: Learn, Grow Food, Eat It Zack Grant, Farm Manager/Project Coordinator
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Lecture Objectives:
Types of Ecosystems II
1.Learn the characteristics of the major biomes - aquatic systems
2.Learn about human impacts on freshwater and marine systems
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Aquatic Biomes
Occupy the largest part of the biosphere- two thirds of the Earth is covered by oceans
Marine algae and photosynthetic bacteria produce large portion of world’s oxygen and consume large amounts of CO2
Differ by salt concentration:- freshwater- saline
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Aquatic Biomes
Aquatic biomes primarily influenced by:Light penetration
Type of bottom substrate
Water temperature
Dissolved materials
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Human Impacts on Marine Systems
Many threats to words oceans
We will focus on:
Overfishing
Aquaculture
Coral reefs
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Pelagic Marine
Pelagic - open water environment
Euphotic zone where all photosynthesis occurs Upper layer where suns rays penetrate
Primary producers are phytoplankton Small, microscopic algae and bacteria Nutrient concentration extremely important in determining
productivity
Phytoplankton consumed by zooplankton, consumed by crustaceans and fish, consumed by larger fish
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Biomes: Pelagic Marine (cont.)
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Benthic MarineBenthic - bottom
Several types: coral reefs, mangrove swamps, abyssalType determined by substrate, temperature and depth
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Benthic MarineCoral reefs
•Require shallow, clear, warm water•Coral is a sessile animal that excretes a hard, exoskeleton•Animals have symbiotic relationship with algae•One of most diverse and productive biomes on earth•Protect coasts from storms, uptake carbon
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Threats to Coral ReefsMost threatened marine habitat
1. Trawling and dynamite fishing - breaks up reefs
2. “Bleaching” - death/loss of algae3. Runoff – pollutants
4. Aquarium industry5. Global warming - corals need shallow water
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Benthic MarineMangrove swamps
•Occur in warm, shoreline areas, with low wave action•Important nursery area for shrimp, fish
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Benthic MarineAbyssal ecosystem
Deep, no light; depend on organic matter from above
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Oceanic Fisheries
Worldwide, 25% of animal protein
70% of world’s marine fisheries are overexploited or in danger of becoming overexploited
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Oceanic FisheriesNumber of fish caught rose steadily until 1990’s, but per capita number caught decreased
Human population growing faster than increase in catch
Leads to increased demand and overfishingmany species commercially extinct - no longer economically profitable to harvest
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Sustainable harvest
Ideal strategy: harvest population to maximize growth rate
determines how quickly fish can be removed, while still maintaining healthy stock
keep population at half carrying capacity (too little or too much harvest, population grows slowly)
Most fisheries harvest too much!
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Why does overfishing occur?Economics - Tragedy of the Commons
Each group tries to maximize individual returns at expense of common resource
Quota problemsOften a fixed number, not percentage
(Harvesting constant number of decreasing population leads to severe impacts)
Technological “Improvements”
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Overfishing Example: Bluefin Tuna
Large, wide ranging, fast animal Grows to 1500 lbs. Swims up to 50 mph Can migrate across oceans
One of most valuable and over-exploited fish Single fish sold for $172,000 in Tokyo fish
market auction - sashimi Adult population declined 90% since 1975
250,000 to about 22,000
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Overfishing: Bluefin Tuna
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Overfishing: Bluefin Tuna
International Commission for the Conservation of Atlantic Tunas (ICCAT) responsible for management
Manages tunas and tuna-like species (marlins, swordfish) Supposed to manage for maximum sustainable yield
Has scientific committee
Compile catch statistics and models population trends
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Overfishing: Bluefin Tuna
Commission’s managers repeatedly ignored scientists’ advice
e.g., 1981 own scientific committee concluded Atlantic tuna population depleted, quotas should be set close to zero
Set 1160 metric ton quota for “scientific study”
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Overfishing: Bluefin Tuna
Population continued to decline, but doubled quota
Early 1990s - Sweden wanted to list bluefin on CITES (Convention on International Trade in Endangered Species)
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Overfishing: Bluefin Tuna
Lobbying by U.S., Canada, and Japan, forced Sweden to accept compromise
50% reduction in catch
Why did efforts fail?1. Lack of commitment by Commission
conflicts of interest - some work for seafood industry
2. Quota problem - number not percent3. Lack of international support4. Non-member nations
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Tuna ban 'justified' by scienceBy Richard Black 29 October 2009
Banning trade in Atlantic bluefin tuna is justified by the extent of their decline, an analysis by scientists advising fisheries regulators suggests.
The International Commission for the Conservation of Atlantic Tunas' (ICCAT) advisers said stocks are probably less than 15% of their original size.
For a number of years, ICCAT has set quotas higher than scientists' recommendations.
The pressure this puts on stocks has been compounded by illegal fishing for this valuable species, which according to some estimates adds 30% to the official quota.
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Bluefin tuna trade ban gains European Union backing
By Richard Black 10 March 2010
EU nations have decided to support a ban on international trade in Atlantic bluefin tuna until stocks recover.
The bloc has agreed to back a motion for a ban during next week's meeting of the Convention on International Trade in Endangered Species (CITES).
The US has already given its support, but Japan - where most bluefin is eaten - may opt out of CITES controls.
The EU is backing exemptions for traditional fishers, and deferring the ban for a year.
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Bluefin tuna ban proposal meets rejection
By Richard Black 18 March 2010
A proposal to ban international trade in Atlantic bluefin tuna, which is a sushi mainstay in Japan, has been rejected by a UN wildlife meeting.
Thursday's decision occurred after Japan, Canada and many poor nations opposed the measure on the grounds it would devastate fishing economies.
Stocks have fallen by about 85% since the industrial fishing era began.
"Welcome to the strange world of globalisation."
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Is Aquaculture the answer?
Aquaculture - breeding and raising of fish and shellfish for food
Rapidly increasing industry
Provides 1/4 world’s marine fisheries
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AquacultureProblems
1. Still depletes natural fish populationsFeeds often include fishmeal from wild populations
especially problematic for carnivores fish (e.g. salmon)
2. Fish wastes - aquatic pollution, disease
3. Genetic diversityraised fish escape and breed with wild fish
4. Can still be bycatch
5. Habitat destruction - loss of mangroves, coastal wetlands habitats
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GMO Salmon
GMO fish grow faster and need less food
Concern over possible escape from aquaculture
“Trojan gene affect” – Muir & Howard, 1999; Howard et al. 2004
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Freshwater Ecosystems
Overharvesting of resourcesHabitat Modification
ChannelizationDamsDraining wetlandsChanges in terrestrial landscape
Invasive Species (e.g., zebra mussel, lamprey)
Pollution (will discuss invasions and pollution in later lectures)
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Estuary
Shallow, partly enclosed area where salinity changes with tides
Very productiveNutrients from riversLight penetration
Important nursery areas for crustaceans and fish
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Freshwater - lakes
Three main habitats:Littoral Zone: shallow areas with rooted submergent and emergent plants
Pelagic Zone: deeper areas of open water
Benthic Zone: Bottom
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Rivers and Streams
Characterized by running water
Attached algae main producer
Many nutrients come from input of terrestrial organic matter
In large rivers, floodplain important source of nutrients, spawning habitat for fish
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Channelization
the dredging and straightening of stream channels
Why?
Divert water for irrigation
Drain fields for agriculture
Increase “usable” land
Prevent flooding
Kissimmee River, FL1961
Present
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Problems with Channelization
Altered flow regimesMany species not adapted to different flows
Loss of habitatReduces habitat complexity
Total stream areaFloodplains
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Dams and stream modifications
Long history of modifying riversEgypt had irrigation ditches by 3200 B.C. and dams by 2760 B.C.
Dams built per year steadily increased from around 1800 to a peak in the 1970’s.
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Dams and stream modifications
75,000 dams over 2m tall, plus 2.5 million smaller dams in the U.S. alone
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Effects of DamsBenefits:
Water supplyNavigationHydropowerFlood Control
Decreased frequency, but increased severity
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Physical Effects of Dams
Alterations of flowPrevents movement of sediment, nutrients downstream
Slower flows upstream leads to settling of sediment reservoirs can fill by as much as 80% in 12 years
More unpredictable flows downstreamDisturbs normal flood-pulse in spring
Interchange of nutrients between river and floodplains
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Biological Effects of Dams
Interrupts fish migration (e.g., salmon)Fish ladders can helpStill can have 10-20% fish loss during outmigration
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Human Health Effects of Dams
Aswan Dam, Egypt – completed in 1970
Schistosomiasis (Bilharzia )
Parasite passes from humans to snails to humans
Irrigation from lake provided more habitat for snails
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Wetlands
Transitional habitats between aquatic and terrestrial environments, where water table is at or near the surface
Includes marshes, swamps, bogs, estuaries, temporary ponds, etc.
Estimated loss of 53% of total wetlands in U.S.9.2 million acres lost between 1950’s-1970’s
2.6 million acres lost between 1970’2-1980’s
current loss of 124,000 acres per year
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Wetland Loss
Wetlands provide important ecosystem services1. Mitigate flooding
2. Retention of sediments, nutrients, pollutants Natural sewage treatment plants
3. Wildlife habitat 20% of threatened and endangered species associated
with wetlands
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Audubon Society Seafood Ratings
Green – abundant, well managedFarmed mussels
and clamsAlaska salmonTroll caught
MahimahiU.S. farmed TilapiaPole/troll caught
yellowfin, bigeye, albacore tuna
Yellow – some concern over status.Longline caught
MahimahiPacific codRainbow troutMaine lobsterSquid (calamari)Canned tuna
Red – severe overfishing, poor managementAtlantic codShrimpAtlantic flounders and
solesSharksFarmed salmonOrange RoughyChilean seabass
(toothfish)
http://www.montereybayaquarium.org/cr/cr_seafoodwatch/download.aspx
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Points to know: 1. What factors affect the type of ecosystem that will
develop?2. Know the characteristics of the major terrestrial biomes. 3. Aquatic biomes can be categorized by several axes:
1. Marine, Freshwater, or Estuary2. Benthic, Pelagic, Littoral
4. What are some differences between lakes/ponds and rivers/streams?
5. Understand differences between primary and secondary succession.
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Points to know 2
1) What is channelization? Why is it done and what problems can it cause?
2) What can be the problems with dams and flood control? How do they affect sediment & water flows, fish migration, and floodplains?
3) What is a wetland and how much has been lost in the U.S.? What ecosystem services do they provide?
4) Why is oceanic fishing important (2 reasons)? Name 3 reasons for overfishing. What does the bluefin tuna example tell us about the effects politics & conflict of interests on fishing policies?
5) What are the pros and cons of aquaculture?
6) Why should you care about the destruction of coral reefs?