Human Impacts on the Ocean and Marine Conservation

I.                    Pollution and eutrophication

A.     Oil (tar in tows)

1.      major oil spills from tankers or drilling platforms -- e.g., Exxon Valdez (1989)

Big Spills: 37 Million Gallons

Only about 5 percent of oil pollution in oceans is due to major tanker accidents, but one big spill can disrupt sea and shore life for miles

Offshore Drilling: 15 Million Gallons

 a.       crude oil usually floats

b.      evaporation results in some sinking

c.       offshore well spills are potentially more devastating -- more oil released

d.      MARPOL

 2.      many minor oil spills

Down the Drain

Routine Ship Maintenance

Up in Smoke

3.      some areas of natural oil seepage

4.      slow degradation

5.      effects on organisms

a.       low energy environments most vulnerable and recover slowest

b.      birds

c.       coats shallow subtidal and intertidal -- smothers communities

d.      detergents used to break up the oil can also be toxic

e.       hot water used to scour the beaches also causes intertidal mortality

f.        less effect on pelagic communities (except birds)

 
B.     Sewage and Runoff

1.      sewage -- eutrophication and disease

a.       with small volumes and/or good treatment it is hard to determine effects on open coasts

b.      problems with large volume, small or enclosed embayments, and poor treatment

c.       examples

2.      runoff

Agriculture and Livestock

Urban Runoff

Land Clearing

3.      eutrophication – excess nutrients

a.       algal blooms

b.      ‘dead zones’ – e.g. in Gulf of Mexico, >22,000 km2

(1)   lack of oxygen

(2)   may affect 80% of the water column

(3)   mobile organisms leave

(4)   sessile organisms killed

 C.     Garbage -- plastics

1.      found floating everywhere

2.      eaten by fishes, seabirds and marine mammals

3.      only slow degradation

4.      the ‘dirty dozen’

1) cigarette butts

2) paper pieces

3) plastic pieces

4) styrofoam

5) glass pieces

6) plastic food bags

7) plastic caps and lids

8) metal beverage cans

9) plastic straws

10) glass beverage bottles

11) plastic beverage bottles

12) styrofoam cups

D.     Chemicals

1.      biological magnification – accumulation of toxins in levels above that in the water and food as you go up the food chain

2.      industrial wastes –

a.       Mercury levels high in swordfish and tuna

b.      Minamata Bay, Japan -- neurological disorder and severe birth defects (Minamata disease)

(1)   factory producing plastics (vinyl chloride) and formaldehyde released Hg into Minamata Bay

(2)   bacteria methylated Hg - allowed it to enter food web; biomagnification

(3)   >100 people poisoned; ~50% died; diagnosed as poisoning in 1959, but not until 1970’s was mercury discharge slowed

(4)   birth defects

c.       other heavy metals – lead, cadmium

3.      organic chemicals -- DDT, TBT, PCBs (polychlorinated biphenyls), dioxins, furans…

a.       DDT, dichlorodiphenyltrichloroethane, synthetic pesticide

(1)   Began use in 1945

(2)   Very stable – it and its breakdown product DDE persist for years

(3)   Enters ocean through runoff and atmosphere

(4)   Adheres to plankton and biomagnifies in the lipids of marine organisms

(5)   Marine fish can sometimes exceed allowable limits

(6)   Marine birds had thin eggs (e.g., brown pelican)

(7)   Slow recovery

b.      TBT, tributyltin, anti-fouling compound for boats; deformation and death of many oysters and shellfish near ports; use of TBT was reduced or banned in many places, and shell deformation has decreased

 c.       Many toxic compounds are carried and deposited atmospherically all around the world; e.g. PCB’s can evaporate into the atmosphere; when they condense they are carried in rain to the ground – these compounds tend to concentrate in the poles – high levels in polar bears, whales, human inhabitants; endocrine disrupters

d.      Release of toxins accumulated in sediments during dredging

 E.      Radioactive Wastes – dumped at sea

1.      accidents

2.      only low-level wastes are currently dumped intentionally

3.      discussion of deep-sea deposition of high level wastes in sediment of abyssal plains – stable, removed from humans

 II.                 Transport of exotics – ‘biological pollutants’

1.      intentional releases –oysters; striped bass

2.      unintentional introductions – ballast water; organisms unintentionally brought with bait and ballast water; canals; aquarium escapees

a.       ctenophore Mnemiopsis leidyi in the Black Sea (from North America)

b.      periwinkle – Littorina littorea, mid 1800s invaded US from Europe

c.       Caulerpa

d.      Small organisms – bacteria, viruses, parasites

III.              Habitats

1.      coastal development

      beach/shoreline engineering and modification
coastal navigation

2. bottom trawling

          3.      silt from dredging 

4.      thermal pollution

5.      decrease in freshwater input

a.       affects estuaries and nearshore areas

b.      affect migrating fish

c.       damming

d.      irrigation – responsible for much of modern agriculture’s production

e.       some solutions – water conservation (low flow toilets); more efficient irrigation; release of water at critical times for organisms

IV.              Fisheries, Mariculture, Harvesting

A.     Fisheries discussed previously; have humans reached the limit of fish exploitation?

1.  marine mammals

            2. fin fish

3. bycatch

B.     Mariculture -- attempts to cultivate aquatic organisms under controlled conditions for foods or products (e.g., pearls)

1.      History and extent --

a.       has a long past, but often not a significant food source; 

b.      most common in other countries

c.       generally confined to shallow coastal embayments and artificial ponds

2.      Species cultivated – seaweeds, shrimps, oysters, mussels, abalone, salmon...

3.      Yields

4.      Problems

a.       difficult to maintain proper physical and chemical characteristics for organisms in culture ‘ponds’ -- expensive filtration

b.      pelagic larval stages of marine organisms -- hard to rear in captivity

c.       many species difficult to culture – require large spaces

d.      diseases and parasites in crowded conditions

e.       escapes; genetic contamination of stocks

f.        expensive permitting process in the US

g.       concerns about pollution/habitat destruction

5.      Case studies

6.      Solutions? 

 C.     Aquarium trade and effects on reef communities

 V.                 Global warming

 
OTHER SOLUTIONS?

VI.              Regulations to reduce pollution; monitor fisheries

VII.            Marine Reserves

A.     National Marine Sanctuary Program, 1972; 18,500 square miles

B.     Everything from ‘wilderness areas’ to managed areas from sustainable fisheries…

VIII.         Habitat restoration –

A.     salt marsh and mangrove seeding

B.     artificial reefs

IX.              Difficulties with reserves and restoration

A.     dispersal

B.     planktonic life forms

C.     global pollution

D.     global warming and sea level changes

WHAT CAN YOU DO? (a short list)

  1. Support pollution control; conservation efforts
  2. If you eat fish/shellfish, try to consume those in least danger (seafood.audubon.org)
  3. Help develop new technologies & policies!
  4. Education – exotics, pollution…
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