Marine Biology 1060            Chapter 17             Study Guide

                   Selected Topics from Impacts of Humans on the Marine Environment

Terms:

trawling        pollution        thermal Pollution        eutrophication        sewage        sludge
dredging        crude oil        DDT                        PCB                        mercury
biodegradable                    pesticides                  fertilizer                 biological magnification

Concepts:

I. Threats to softbottom intertidal zones
    A. trawling for benthic species digs up substrate and associated organisms
    B. dredging channel increases wave damage, wind damage
    C. changing estuarine channels often alters salinity within seagrass, salt marsh and mangrove habitats
    D. Oil spills do much  more damage in soft bottom intertidal habitats then in rocky intertidal habitats
        1. oil becomes intermixed with sediments and is not as readily degraded or removed
 
II. Sewage pollution threatens all habitat types
    A. large quantities of human waste and sewage is dumped directly into marine waters
    B. enriched organics cause algal and bacterial blooms which use up the oxygen
    c. system crashes and most organisms die in anoxic conditions - eutrophication
    D. these effects are seen in salt marsh, mangrove, beach, mud, rocky intertidal, coral reef,
        and open water habitats
    E. even treated sewage - sludge- has eutrophic effects
III. Chemical pollution
    A. Amoco Cadiz spilled 230,000 tons of crude oil off the Britanny Coast in 1978
    B. Exxon Valdez spilled 35,000 tons off Alaska coast - 1989 - cost was  approximately $8 billion
        1. estimated kills: 300,000 sea birds, 3,500-5,000 sea otters, unknown numbers of fish and unseen species
    C.  Fortunately oil is biodegradable by bacteria, but the recovery time for damaged systems is long.
        . The effects of the Exxon Valdez spill are predicted to last 70 - 100 years
    E. DDT was responsible for the near extinction of many marine birds in the 1960s. Brown Pelicans
        and the Osprey were two examples. Malformed eggs, deformed and dead hatchlings
    F. Polychlorinated Biphenyls (PCBs) are highly toxic pollutants from the electrical industry which
        are highly persistent in marine systems. Do not biodegrade. Other examples are dioxins
    G. Mercury poisoning - heavy metal toxins are a common marine pollutant of industry.
    H. many toxins become more and more concentrated in organisms which feed higher on the food
        chain. This effect is called biomagnification and is a particular threat to humans.