13 ecosystems2 1

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  

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

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

Aquatic Biomes

Aquatic biomes primarily influenced by:Light penetration

Type of bottom substrate

Water temperature

Dissolved materials

Human Impacts on Marine Systems

Many threats to words oceans

We will focus on:

Overfishing

Aquaculture

Coral reefs

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

Biomes: Pelagic Marine (cont.)

Benthic MarineBenthic - bottom

Several types: coral reefs, mangrove swamps, abyssalType determined by substrate, temperature and depth

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

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

Benthic MarineMangrove swamps

•Occur in warm, shoreline areas, with low wave action•Important nursery area for shrimp, fish

Benthic MarineAbyssal ecosystem

Deep, no light; depend on organic matter from above

Oceanic Fisheries

Worldwide, 25% of animal protein

70% of world’s marine fisheries are overexploited or in danger of becoming overexploited

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

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!

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”

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

Overfishing: Bluefin Tuna

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

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”

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)

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

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.

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.

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."

Is Aquaculture the answer?

Aquaculture - breeding and raising of fish and shellfish for food

Rapidly increasing industry

Provides 1/4 world’s marine fisheries

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

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

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)

Estuary

Shallow, partly enclosed area where salinity changes with tides

Very productiveNutrients from riversLight penetration

Important nursery areas for crustaceans and fish

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

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

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

Problems with Channelization

Altered flow regimesMany species not adapted to different flows

Loss of habitatReduces habitat complexity

Total stream areaFloodplains

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.

Dams and stream modifications

75,000 dams over 2m tall, plus 2.5 million smaller dams in the U.S. alone

Effects of DamsBenefits:

Water supplyNavigationHydropowerFlood Control

Decreased frequency, but increased severity

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

Biological Effects of Dams

Interrupts fish migration (e.g., salmon)Fish ladders can helpStill can have 10-20% fish loss during outmigration

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

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

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

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

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.

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?