a. Effects on Biotic Communities
 Dramatic changes in benthic communities occur along rocky
shorelines, estuaries, and shallow coastal marine environments
exposed to polluting oil.

Low-energy habitats likely to trap oil, such as salt marshes,
mangroves, and sea grasses, are generally teeming with life.
Once the oil permeates through the bottom sediments, it creates
long-term hazardous conditions that threaten the overall
stability and health of the benthos.

Low oxygen concentrations in deeper sediment layers hinder
bacterial degradation of the oil.
 The rate of recovery of an intertidal or shallow subtidal marine
habitat is controlled by the number of oiling events and the
depth of oil penetration into the substrate.

Shallow-rooted annuals with limited food reserves are much
more susceptible to oil pollution than perennials with.
 The magnitude of oil impacts on estuarine and marine
organisms is contingent upon many factors, the most notable
being
(1) The amount of the oil;
(2) Composition of the oil;
(3) Form of the oil (i.e., fresh, weathered, or emulsified);
(4) Occurrence of the oil (i.e., in solution suspension, dispersion, or
adsorbed onto particulate matter);
(5) Duration of exposure;
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(6) Involvement of neuston, plankton, nekton, or benthos in the
spill or release;
(7) Juvenile or adult forms involved;
(8) Previous history of pollutant exposure of the biota;
(9) Season of the year;
(10) natural environmental stresses associated with fluctuations in
temperature, salinity, and other variables;
(11) types of habitat affected; and
(12) cleanup operations (e.g., physical methods of oil recovery and
the use of chemical dispersants).
 Organisms which are trapped, smothered, and suffocated by an oil
spill. Those individuals surviving the physical impact of the oil
may lose normal physiological or behavioral function if coated,
thus predisposing them to greater long-term risk of death.
 Sub-lethal effects, such as the impairment of organisms to obtain
food or to escape from predators after being coated by the oil,
likewise increase mortality of individuals within day or weeks of a
spill.
 Fish tend to avoid oil spills because they can swim.
Hence,
immediate impacts on fish populations may not be apparent.
 Mammals and seabirds exhibit an array of response to oil. Sublethal
effects
chronicled
in
marine
mammals
include
gastrointestinal and blood disorders, respiratory problems, changes
in enzymatic activity in the skin, renal deficiencies, interferences
with swimming, eye irritation.
2. Polycyclic Aromatic Hydrocarbons
a. Sources and Concentrations
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 PAH compounds originate from a variety of anthropogenic sources
(e.g., municipal and industrial effluents, creosote, oil spills, urban
and agricultural runoff, and fossil.

Incomplete combustion of organic matter, especially in the high
temperature (500-800oC) range, is a primary mechanism for
atmospheric contamination by PAH compounds, many of which
enter marine waters via fallout.
b. Distribution
PAHs in Estuarine and Coastal Marine Environments
 The transport of PAHs to marine environments occurs via surface
waters and the atmosphere.
 Bottom sediments of estuaries and near shore coastal marine waters
located near urban and industrial centers serve as major
repositories of PAHs.
 Because of the strong affinity of PAHs for sediments and other
particulate matter, they accumulate too much higher concentrations
on the seafloor than in overlying waters.
 The concentrations of PAHs in seafloor sediments usually exceed
those in the water column by a factor of 1000 or more.
c. Effects on Biotic Communities
 Polycyclic aromatic hydrocarbons adversely affect marine life
as revealed by both laboratory experiments and field
observations. However, the response of marine organisms to
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PAH exposure varies widely in nature, owing to variation in
bioavailability.

Taxonomic groups with poorly developed mixed function
oxygenase (MFO) capability.
compounds efficiently.
Do not metabolize the
Hence, PAHs readily accumulate in
these organisms, and they are often used as bio-monitors of
PAH contamination in coastal waters.
 Fish exposed to PAHs commonly develop lesions and tumors,
and some investigators have reported a correlation between
tissue levels of PAHs and neoplasia in mollusks.
 Bacteria oxidize PAHs to carbon dioxide and water and in the
process produce dihydrodiols and catechols.
 Marine community changes caused by individual PAHs are
more difficult to delineate than those generated by oil spills.

This is so because PAHs affect organisms through multiple
pathways (e.g., physical contact, smothering, toxic action, and
habitat modification).
 Although acute lethal effects associated with elevated PAH
level (e.g., local mass fish kills) have been rarely observed in
nature,
sub-lethal
effects
manifested
at
much
concentrations are a chronic problem in some regions.
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lower
3. Halogenated Hydrocarbons
Sources
 More dangerous than the effects of sewage sludge dumping or
major oil spills are the impacts of halogenated hydrocarbons that
slowly accumulate in the marine hydrosphere.
 Organochlorine compounds, such as DDT, chlordane, and PCBs,
provide examples (Figure 10).
 These chemical contaminants enter marine waters via multiple
routes including urban and agricultural runoff, sewage waste
disposal, industrial waste input, and atmospheric deposition.
 Two other classes of halogenated hydrocarbons, the chlorinated
dibenzo-p-dioxins (CDSs) and chlorinated dibenzofurans (CDFs),
are considerably toxic to marine organisms.

These aromatic heterocyclic compounds originate from numerous
anthropogenic sources, most notably industrial discharges from
pulp and paper mills, wood treatment plants.
 Many halogenated hydrocarbons are broad-spectrum poisons that
affect entire biotic communities.
Chlorinated Hydrocarbons
 The Joint Group of Experts on the Scientific Aspects of Marine
Pollution classifies chlorinated hydrocarbons compounds into five
groups:
(1) Lower-molecular-weight compounds (up to three carbons);
(2) Aliphatic and aromatic herbicides (up to six carbons);
(3)Long-chain chlorinated paraffins;
(4) chlorinated insecticides (e.g., mirex and camphenes); and
(5) chlorinated aromatic industrial chemicals (e.g., PCBS).
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 A diverse group of biocides (insecticides, herbicides, and
fungicides) has been found in estuarine and near shore oceanic
waters.
 Fungicides of importance include chlorinated benzenes and
phenols.
Chlorophenoxy compounds, such as 2,4-D and 2,4-T, are selective
herbicides of note.
i. DDT
 The synthetic pesticide DDT and its breakdown derivative DDE
pose a significant hazard to estuarine and marine organisms.
 DDT and DDE are extremely persistent and recalcitrant to
degradation in marine environments.
 DDT attacks the central nervous system of insects and nontarget
species.
 As a universal contaminant, DDT has been detected in seawater,
sediment, and biotic samples from most estuarine and coastal
regions worldwide, as well as from many offshore and deep-sea
locations. Substantially higher residue levels have been recorded
in higher-trophic-level organisms, most notably fish, dolphins,
porpoises, whales, and seals.
ii. Polychlorinated Biphenyls
 Among the most important industrial contaminants in marine
ecosystems are polychlorinated biphenyls (PCSs), a group of
synthetic halogenated aromatic hydrocarbons that has been linked
to a number of environmental and public health concerns.
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 PCBs enter marine waters most directly via waste discharges from
manufacturing facilities and industries.

Secondary sources include leaching from dumpsites, volatilization
by vaporization from plastics, and inefficient burning in
incinerators followed by adsorption onto particulates.

Atmospheric transport is a major reason for the global distribution
of PCBs.
 When expose to sufficiently high PCB levels, fish experience a
greater incidence of epidermal lesions, blood anemia, altered
immune responses, and fin erosion, and marine mammals (e.g.,
porpoises, seals, sea lions, whales), an array of reproductive
abnormalities, such as pathological changes in reproductive organs
and accompanying depression of reproductive potential.
 PCB levels typically peak in the surface microlayer.
 As in the case of DDT, PCBs rapidly sorbs to fine-grained
sediments and other particulate matter and subsequently settle to
the seafloor.
 The concentrations of PCBs increase by a factor of 10 to 100 times
when proceeding upward through marine food chains.
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