Importance of Aquatic Ecosystems
 Why is preserving these ecosystems important?
 What services do they provide to other ecosystems,
organisms, or humans?
 What are ways that humans are threatening these
ecosystems? (specific ways)
Threats to Aquatic
Ecosystems
Chapter 11
Human Impacts on Biodiversity
 Specific threats to Aquatic Biodiversity
 Pollution (non-point and point source)
 Degradation of coastal/inland wetlands and estuaries
 Overfishing
 Invasive species
 Altering lake/river flow—dams and irrigation
 Climate change
 Ocean Habitat destruction (ocean bottom and coral
reefs)
Threats to Aquatic Biodiversity…
and biodiversity in general
 HIPPCO
 H-Habitat Loss and Degradation
 I- Invasive Species
 P- Human Population Growth
 P- Pollution
 C- Climate Change
 O- Overexploitation
HIPPCO
 Habitat Loss and Degradation
 little is understood about the ocean and its organisms
 90% of all fish species spawn on coral reefs, coastal wetlands and
marshes, in mangrove forests, and rivers.
 these are among the most threatened aquatic ecosystems
 Sea grass beds (which act as nurseries) are being lost or degraded
 Rising sea levels (due to climate change) will destroy reefs and
swamp coastal wetlands
 Sea bottom habitats destroyed due to harmful fishing practices
(trawling/dredging)
 In freshwater ecosystems...


dams alter river flows
irrigation for agriculture provides enormous stress on water
resources
HIPPCO
 Invasive Species
 introduced deliberately or accidentally
 displace or cause the extinction of native
species and disrupt ecosystem functioning
 most have arrived in ship ballast water
(globalization)
HIPPCO
 Human Population Growth
 majority of the worlds population lives in coastal areas, this
increase has added additional pressure to these ecosystems

oceans becoming more crowded (collisions with whales
and ships)

oceans becoming noisier (disrupt communication and
migration patterns)
HIPPCO
 Pollution
 most comes from land-based activities

run-off of nitrogen and phosphorus fertilizers
increase eutrophication and cause algal blooms

toxic chemicals (DDT, PCBs, mercury)from industry
can kill aquatic species or alter their physiology

Plastic. Mimic food sources and are accidentally
ingested. Release toxic compounds to the water.
HIPPCO
 Climate Change
 Rising sea levels

destroy reefs,
wetlands, and
other ecosystems

displace humans to
other areas
 Warmer and more
acidic water.

increases dissolved
CO2, breaks down
shells of organisms
HIPPCO
 Overexploitation
 Overfishing.


Industrial fishing fleets include
~4 million boats
currently harvesting 57% more
than the sustainable yield
 “Commercial Extinction”--no longer
profitable to continue harvesting
the species

If given time, fisheries can recover
quickly, but if continued to be
exploited then less likely to bounce
back.

larger fish species (tuna, cod,
marlin, swordfish) are increasingly
scarce...so begin to fish “down the
food chain” which provides less
food for larger species
Too many boats, chasing
too few fish….
 Fishery: concentration of a particular wild aquatic
species suitable for commercial harvesting
 Fishprint: defined area of ocean needed to sustain the
fish consumption of an average person, nation, or
world.
 Bycatch: unwanted, accidentally caught organisms
that are thrown back (33% of total catch)
 20 million metric tons are destroyed a year
 80,000 whales, dolphins, seals, and turtles are among
the animals
 Shrimp trawlers throw back 5.2 pounds of marine life
that will eventually die for every pound of shrimp caught
 As fisheries continue to be exploited their recovery
time increases
 Commercially valuable wild species (cod, tuna,
marlin, swordfish, mackerel, even sharks) will be
driven to extinction if continued to be harvested at
current rates.
 Some estimate as soon as 2050!
 Aquatic species are disappearing 5 times faster than
terrestrial ones
 Example: Atlantic Cod off the coast of Newfoundland


Species was hunted to brink of extinction.
Ban on fishing was implemented in early 1990s. Populations
have still not recovered. (Tragedy of the Commons!)
Industrial Fishing Practices
 Modern fishing boats are very
sophisticated using GPS,
sonar, spotter planes, large
nets and long fishing lines to
find the fish.
 Essentially the fish have no
chance to hide…
 Cause tremendous ecosystem
damage and reduce
biodiversity
 A large portion of the fishing
vessels come from lessdeveloped countries
(especially Asia)
 Many which don’t abide by
international fishing quotas
Trawling
 Used to catch cod, flounder,
shrimp and scallops
 Drag a funnel shaped net along the
ocean bottom, weighted with
chains and plates
 Some nets large enough to hold 12
747s!!
 VERY destructive. Destroys
everything in its path
 Same as clear cutting a forest
Purse-Seine
 Used to catch surface
dwelling species (tuna,
mackerel, anchovies ,
salmon and herring),
schooling species
 A large net encloses the
school, tightens around it
then brings fish to the
boat
Long-Line
 Lines up to 60 miles long
with thousands of baited
hooks
 Depth of line adjusted to
catch open-ocean species
(swordfish, tuna, shark) or
ocean-bottom species
(halibut and cod)
 Accidently catch sea turtles,
birds, and dolphins on hooks
Driftnet (gill net)
 Drifting nets go as deep as 50 feet
and 40 miles long
 Leads to unwanted fish caught as
well as overfishing of certain
species
 Accidentally catch mammals,
turtles ,and bird
 Lines longer than 1.2 miles
banned by the UN in 1992 in
international waters
 Compliance is voluntary!
Whaling Industry
 During the height of the whaling industry 1.5 million
whales were killed (1950-1975)
 Drove 8 of the 11 major species to commercial extinction
 Right, bowhead, blue, fin, sei, humpback, minke and sperm
whales
 Blue whale numbers (largest mammal) are less than 5000
 1946 International Whaling Commission was established
to regulate industry
 1986 set moratorium on whaling (banned) including the
sale of whale products

Iceland (minke, fin) Japan (minke, sei and fin), and Norway
(minke) ignore ban
Fisheries Management
 Difficult to estimate fish numbers due to size of ecosystem and
migration
 Aim for harvesting “optimum sustained yield”
 Set quotas and fishing allotment (fishing seasons)
 Decrease government subsidies on fish
 Consumer vote (buy sustainably harvested fish)
 Marine Stewardship Council Labels
 Ask where fish came from
 Protect predator species (eat lower on food chain)
 Aquaculture “farming fish”
 Presents a new set of problems…
Protecting and Sustaining
Aquatic Biodiversity
Challenges…
 Difficult to protect aquatic ecosystems due to rapidly
growing human population and expanding ecological
footprint
 Damage isn’t always visible
 Historically have believed ocean is an inexhaustible
resource
 Ocean lies outside the legal jurisdiction of any country—
or have rivers/lakes that span multiple countries
 Leads to overexploitation (Tragedy of the Commons)
Laws and Treaties
 1975- Convention on the International Trade in Endangered
Species
 Ensures trade of organisms doesn’t harm their survival
(endangered and threatened species)
 1979 Global Treaty on Migratory Species
 Protects migration routes and habitat for terrestrial, aquatic and
avian species (UN)
 1972 Marine Mammal Protection Act
 Listed organisms may not be “taken” in US waters or high seas or
their products imported
 1973- US Endangered Species Act
 Lists and protects endangered species and their habitats
 1976- US Whale Conservation and Protection Act
 Protects whales along US coasts including Mexico and Canada;
prohibits sale of whale products (including imports)
 1995- International Convention on Biological Diversity
 Develop strategies to sustain and protect biodiversity on a
global level
 1986- International Moratorium on Whaling
 Globally prohibits the hunting of whales and selling of whale
products
**All of these are difficult to enforce international compliance
Marine Ecosystems
 Economic Incentives to Protect Species (ecotourism)
 Animals worth more alive than dead
 Marine Sanctuaries
 Countries allocate offshore fishing zones (it regulates up to 200 nautical
miles from shoreline)


Boats may only fish here with permission
“high seas”- ocean area beyond any legal jurisdiction (difficult to monitor and
enforce)
 “Law of the Sea Treaty”
 Outlines who can fish where
 Need to switch focus to protecting ecosystems, not just individual species
 Less than 1% of the ocean currently protected in marine reserves, recommended to
protect 30-50%
Freshwater Ecosystems
 Wetlands




Develop land areas away from them
Permit required to fill in more than 3 acres
Only 6% of remaining wetlands protected
“mitigation banking”—may destroy wetlands as long as recreate the same
size in another area (not always effective)
 Lakes and Rivers
 1968 Wild and Scenic Rivers Act—protects only 3% of US rivers
 Preserve rivers in their natural “free-flowing” state
 Minimize exposure to invasive species, or work to remove those already
present
 Protect watersheds

Identify pollutant sources
 Damming rivers causes ecosystem disruption
 Prevent fish species from spawning