Case study of Bioaccumulation and Biomagnification

Orcas - endangered species of Puget Sound

Orcas = killer whales Scientific name:

Orcinus orca Largest member of

dolphin family Identifying traits:

height of dorsal fin saddle patch behind

dorsal fin white patches on

sides, belly, behind eyes

Orca biology

Birth weight: around 400 lbs Adult weight: 2.5 – 7 tons

Males larger than females Lifespan:

Females: can live 60+ yrs Males: live around 40 years

Natural History Found in all seas--- arctic to tropics Travel in pods: 3 – 150+ individuals Main food:

Fish Squid Marine mammals

Transient vs. Resident Orcas 2 major subspecies of orca Transient orcas:

Live offshore Feed mostly on marine mammals Small pods of 3-5 individuals Tend to be very quiet

Resident orcas: Live near shore Feed mostly on fish (especially salmon) Large pods: 20+ individuals Vocalize often

Puget Sound Resident Orcas

Live in extended family units called pods Pods are dominated by females (‘matriarchal’):

Oldest female is the grandmother of other orcas in pod Puget sound resident orcas

3 pods – J, K, L Summer around San Juan islands Winter on

the outer coast

Southern Resident Orcas 1995-2000: about 20% of

southern resident orcas died – now 89 orcas

Many females of reproductive age are not reproducing or young are not surviving.

Young males: dying rapidly Few males left in entire

community Listed as endangered

species in 2005 – at risk of extinction

Threats to Orcas Decreasing food supply

Many wild salmon species are also listed as an endangered species

Disturbance Physical (harassment by whale watching vessels) Acoustic (low/mid frequency sonar, drilling, dredging)

• Interferes with echolocation

Environmental contamination Bioaccumulation of pollutants

Historic threats Hunting Captured for captivity in marine parks

Pollutants

Pollutant: any agent that negatively affects the health, survival, or activities of living organisms or that alters the environment in undesirable ways

How do pollutants enter environment? Point source pollution-

specific locations of highly concentrated discharge Factories, power plants,

sewage treatment plants Non-point source pollution-

diffuse sources/scattered through Runoff from farms, roads, golf

courses, homes, etc.

NOTE: all pollutants eventually end up in the ocean

Types of pollutantsWater soluble pollutants

Dissolve in water & move rapidly and widely through an environment

Fat soluble pollutants Inside organisms, they easily get into tissues and

cells• Stored in fat deposits• Do not breakdown within an organism (protected from

metabolic break down)• Passed through breast milk to young in mammals

Tend to have much longer effects

Pollutant persistencePersistence = how long it takes to

breakdown and be removed from the ecosystem

Some compounds are very unstable and degrade rapidly Concentrations decline rapidly over time

Other compounds are specifically designed to resist degradation (don’t break-down easily) Can have severe impacts long after they are

introduced

POPs

Persistant Organic Pollutants Human made organic compounds used in

various products (from electronics to cars) that are not easily broken down in the environment

Include PCBs and DDT

Can have very long term effects in affected ecosystems

PCBs: Polychlorinated biphenyls

BOTH FAT SOLUBLE AND A POP = very stable and resists degradation

Used in: transformers, pesticides, paint, small electric parts, etcfrom 1929 - 1977

Enter mainly through non-point sources: products with PCBs leak, PCB travels into soil, carried by wind and water into environment (and eventually the ocean)

In rats – cause liver cancer, pituitary tumors, leukemia, lymphoma and intestinal cancer

In humans, classified as a probable human carcinogen (cancer causer) → banned in 1977

Bioaccumulation Process by which cells selectively absorb

and store a great variety of molecules Allows cell to accumulate nutrients and

essential minerals (like calcium, phosphorus, etc.)

However, same process can also absorb and store harmful pollutants inside an organism

• Reason some fish are not fit for human consumption (usually because of bioaccumulation of mercury)

Biomagnification Process by which the effects of

pollutants are magnified up an ecosystem through food chains When organism consumed by a

higher trophic level, only about 10% of energy moves up, however majority of the pollutant is passed on from prey to consumer

Therefore – as the pollutant moves up the food chain, the concentration of the pollutant in the body tissue increases dramatically

This is especially true for POPs since they persist for long periods of time

Biomagnification ExampleDDT residues - Long Island Estuary

Woodwell, Wurster, Isaacson, 1967

Trophic level Organism DDT (wet weight)

PrimaryProducer

Green alga 0.08 ppm (parts per million)

PrimaryConsumer

Mud snail 0.26 ppm

Secondary Consumer

Summer Flounder

1.28 ppm

TertiaryConsumer

Ring-billed gull

75.5 ppm

Puget sound orcas affected by PCB’s

Our orcas have, on average, the highest measured levels of PCB’s of any marine mammal IN THE WORLD

Almost 150 ppm (parts per million) average >10 ppm PCB known to cause immune problems

in seals Mother can pass as much as 90% of PCB’s to

her offspring via milk and through placenta Female transient orca found dead on Dungeness

spit in 2002 had 1000 ppm

Yeah, but there are banned, right?Double whammy for our orcas

PCB’s are less harmful when in fat vs. their bloodstream

When food in short supply = orcas use blubber (fat) for energy

↓PCB’s released into blood

↓PCBs interfere with normal immune function

↓Result: orcas more susceptible to disease and pathogens

Yeah, but PCB’s are banned, right?- other POP’s – the ‘Dirty Dozen’

POP (persistent organic pollutant)

Pesticide Industrial Chemical By-product

Aldrin √

Chlordane √

DDT √

Dieldrin √

Endrin √

Heptachlor √

Mirex √

Toxaphene √

Hexachlorobenzene √ √ √

PCBs √ √

Dioxins √

Furans √

New era, new threats

Many countries still use chemicals that have proven to bioaccumulate

Chemicals are stored all over the world and are often not properly disposed of

US does not have a law that insists on testing of new chemicals (unless they are used in food) Only 10% of the 85,000 chemicals used in

North America have been tested for environmental effects

PBDEs: example of a new threat

Polybrominated diphenyl ethers Group of fire-retardant chemicals (they

don’t catch fire) A POP: structurally similar to PCB’s Found in furniture, televisions,

computers Europe has banned PBDE’s, only

state to ban is California There IS an available fire retardant

shown not to bioaccumulate