contaminants and conservation. contaminant impacts key difficulty for measuring contaminant impacts...
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Contaminant Impacts
• Key difficulty for measuring contaminant impacts is that most if not all systems impacted by contaminants are also affected by other human-mediated changes
• Coastal systems typically experience multiple impacts and contaminants may not even be the most important stressor
Multiple Contaminants
• Petroleum• Radionucleotides• Pesticides• Herbicides• Heavy metals• Nutrient inputs (eutrophication)• Sediments• Salinity
Integrating Across Levels
• Need to integrate across levels• Biomarkers and bioindicators have
different strengths and weaknesses• Focus on organismal level with
bioindicators at population and community level with biomarkers at suborganismal levels
• Population, community and ecosystem levels will be today’s focus
Measuring Impacts
• In order to measure changes, you need to conduct some type of environmental monitoring
• Make periodic measurements of a set of attributes in a location of set of locations
• The goal is to compare the condition of either contaminated sites vs. uncontaminated (less) sites or across a gradient of sites with varying levels of contamination
Measuring Impacts
• Can’t compare everything nor measure everything
• Focus on particular taxa– Birds, fish, invertebrates, algae
• Focus on particular habitats– Salt marshes, mangroves, coral reefs
• Focus on particular groups– Predators, grazers, decomposers, primary
producers (plants)
Measuring Impacts
• Impacts of contaminants usually have a short-term (acute) and long-term (chronic) components
• Spatial and temporal scales of impacts are not typically known
• Subtle changes in the short-term that may ultimately have large long-term effects may be difficult to separate from other environmental variation
Measuring Impacts
• What properties or fractions of the contaminants that are causing harm is even difficult to determine
• Mercury is relatively inert in an inorganic phase but very toxic in an organic phase
• Bioavailability for many compounds is difficult to determine
Measuring Impacts
• Some compounds may be stored by and organism, others metabolized
• Levels of contaminant in an organism may not be a good indicator of either exposure or toxicity
• Chemical interaction among different compounds may change bioavailability or toxicity
Antifouling Paint: Tributyl Tin (TBT)
• For many years, commercial, military and recreational boaters used increasingly toxic bottom paints (copper, tin) to prevent fouling
• Organotin compounds were found to be very effective but very toxic
• Although TBT is now banned except for military ships, TBT is still present in sediments in many harbors
TBT Exposure and Imposex
• Although there have been many documented lethal effects of TBT, sublethal effects can be damaging
• At very low concentrations, TBT can result in female molluscs changing into males (not reproductive)
• Particularly in snail,s TBT can turn females into a nonreproductive males in a state called imposex
Pesticides: Pyrethroids
• Pyrethroids and related pesticides are common components of urban and surburban runoff
• They are extremely toxic to insects and other arthropods, and stable in aquatic systems
• This can accumulate on sediments and result in very toxic effects on copepods, mysids, etc. as well as fish
Creosote and PAHs
• Among the many compounds introduced in bays and harbors is creosote used to preserve wooden piers and pilings
• Polynuclear aromatic hydrocarbons (PAHs) are among the compounds released from creosote (PAHs have other sources too)
• PAHs can accumulate in toxic levels in harbors and estuaries causing lesions and tumors in marine organisms
Other Marine Contaminants
• Carbaryl (Sevin) is a pesticide used in terrestrial, aquatic and marine systems to kill arthropods (insects)
• In Pacific northwest estuaries, it is used to kill burrowing shrimp that disrupt oyster production
• Many other species are killed including crabs and shrimps, but the long-term effects are uncertain
Other Marine Contaminants
• Eradication of invasive estuarine plants involves applying herbicides like Imazypyr
• Although the herbicide is low toxicity, the surfactant that is used to apply the herbicide may be more toxic
• These are being applied over large areas of San Francisco Bay to eradicate Spartina, with hopefully minimal impacts
Petroleum: Large Scale Impacts
• Few contaminants are moved in marine systems in quantities equal to oil
• Large oil spills have occurred in many different habitats
• In most cases, effects of even large oil spills are hard to measure
• Typically few data are available prior to event to compare with post-spill data
• Sediment and tissue levels are hard to correlate with impacts
Panama Oil Spill
• There was an oil spill (3.2 million gallons) in in Panama 1968 near the Smithsonian Institution’s Goleta lab
• Studies following that oil spill as well as many ongoing scientific studies (not oil related) create substantial baseline to measure effects
• Larger oil spill (8 million gallons) in 1989 occurred as the result of a ruptured land-based storage tank
• Oil affected mangrove forests, sea grass beds and coral reef habitats
Panama Oil Spill
• Best data was available for mangroves and subtidal corals (pre-spill data from oiled an unoiled sites) less for reef flats and seagrasses
• Highest concentrations of oil in mangroves and sea grass areas occurred within a few kilometers of the spill
• Areas affected by wind driven currents were more affected by oil accumulation
• Low tides after the spill contributed to high oil concentrations at seaward borders of reef flats
Panama Oil Spill Five Years After
• Studies were conducted for the next five years in mangroves to determine long-term effects (Garrity et al. 1994, Burns et al. 1994, Levings et al. 1994)
• Effects included reduced length of mangrove forest (fringe)
• Also reduced length and number of mangrove prop roots: important structural habitat
Panama Oil Spill Five Years After
• Sediment cores looking at presence of dead mangrove roots allowed analysis of even longer term effects
• Also degradation of oil in deep muds was found to be very slow
• Burns et al. (1994) concluded that toxic effects of oil in mangrove muds could continue for at least 20 years after oil spills
Oil in New England Salt Marsh
• In 1969, a large oil spill of number 2 fuel oil spilled in West Falmouth Harbor, MA
• Large changes took place as measured 5 years afterward
• Teal et al. (1992) went back and assessed changes 20 years later
Oil in New England Salt Marsh
• They found that most of the oil had disappeared except for one of the most heavily oiled sites
• Most of the organisms sampled had only remant levels of contamination (not much above background levels)
• Conclusion is that the oil has largely broken down and that the system is functioning relative normally
Oil in Alaska
• In 1989, the Exxon Valdez dumped 11 million gallons of crude into northern Prince William Sound, AK
• It contaminated nearly 2000 km of coastline and as far as 750 km from the spill site
Oil in Alaska
• Many acute or short-term impacts (Peterson et al. 2003) including deaths of:– 1000-2800 northern sea otters– 250,000 sea birds– 300 harbor seals
• Many other immediate impacts on fisheries that were harder to quantify particularly lost recruitment
Oil in Alaska
• Long-term impacts as well (Peterson et al. 2003)
• Rate of oil degradation slowed down markedly from 56% per year up to 1992 to about 20% per year by 2001
• Depositional refuges and areas protected from sun and wave energy contribute to this remainder
• Compounds like PAHs that derive from weather oil were still in abundance years later– Toxic to pink salmon larve at <20 ppb
Oil in Alaska
• Recovery of sea otters was much slower in oiled areas of Prince William Sound – Feed on clam and mussels that still have
measurable levels of oil toxicity (for as much as 30 years)
• Harlequin ducks and Barrow’s goldeneye’s also show no recovery in oiled areas– Feed on intertidal invertebrates that show
elevated enzyme levels due to contamination
Oil in Alaska
• Juvenile pink salmon that had been exposed to sublethal doses of PAHs in lab showed only half the survival rate in the next 1.5 years in a mark-release-recapture experiment
• Exposure to sublethal doses during sensitive life stages can have significant impacts months to years later
Direct vs. Indirect Effects of Contaminants
• Contaminants rarely affect single species in natural systems
• Contaminants will effect multiple species with varying results
• By impacting some species more than others, contaminants will have both direct and indirect effects on species abundances
Indirect Effects of Contaminants
• Direct effects usually lead to reduced abundances of organisms
• Indirect effects can result in either increased or decreased abundances
• A review of 150 studies that reference indirect effects of contaminants showed such effects in 60% of the studies (Fleeger et al. 2003)
• The most common result was an increase in primary producers (plants) (trophic cascade)
• Some evidence for competitive release, but few studies have tested this
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