FATE OF WASTES AND POLLUTANTS
 Biogeochemical processes govern the distribution and fate of
anthropogenic wastes and associated pollutants in estuarine and
coastal marine environments, discharging and dumping wastes in
estuaries and coastal marine waters is an expected dilution
response.

Dilution may be defined as “the process by which one constituent
is mixed with others, causing the ingredients to spread out over a
large volume than before, with a consequent reduction in
concentration.
 Diffusion enhances dilution of waste materials, resulting in lower
concentrations of pollutants at points of discharge.

In the coastal zone, hydrographic processes produce more
complex circulation patterns than in offshore areas, with water
movement being influenced by coastal boundary layer effects, a
broad spectrum of turbulent eddies, and flow modulated by local
bathymetry and shoreline configurations.

Estuarine circulation appears to be even more problematic. New
monitoring techniques and dispersion models have been introduced
to study mixing and transport mechanisms.

Hydraulic and numerical models have been employed for many
years to examine the spread of pollutants in estuarine and coastal
marine waters.

It is difficult to construct a single model for the movement,
transformation, and fate of a pollutant because of the many diverse,
unrelated forces acting on it simultaneously when released into
marine waters.
1
 Organisms likewise can transport wastes and contaminants from
one location to another.
 Many fauna, particularly fish, migrate long distances from open
ocean and coastal waters into estuaries to breed and to seek nursery
habitats for their offspring.
 The seafloor is the ultimate repository for many pollutants.
Flocculation and sedimentation facilitate the flux of wastes and
pollutants to the seafloor.

Excretory products and the remains of marine organisms, which
commonly contain contaminants, also accumulate on the bottom.
 Contaminants can be remobilized by bioturbation activities of
benthic organisms, by chemical processes, by waves and currents
which soil bottom sediments. Advection processes often transport
these substances long distances from original depositional sites.
VI. BIOTIC EFFECTS OF WASTE INPUTS
Biological concerns of waste loading in marine environments have
focused on four main points:
1. The accumulation and transfer of metals and xenobiotic
compounds in marine food webs, including accumulation in
commercial resources;
2. The toxic effects of such contaminants on the survival and
reproduction of marine organisms and the resulting impact on
marine ecosystems;
2
3. The uptake and accumulation of pathogenic organisms in
commercially harvested species destined for human consumption,
and
4. The release of degradable organic matter and nutrients to the
ocean, resulting in localized eutrophication and organic
enrichment.
 The uptake of the contaminants by marine organisms occurs
through the ingestion of food and detritus particles, water exchange
of feeding and respiratory surfaces, and adsorption of chemicals
onto body surfaces.

The capacity to store, remove and detoxify contaminants varies
among different taxa.
 The bioavailability of contaminants, their chemical form, the
physiological state of the organisms, and its ability to regulate
contaminant uptake must be considered in bioaccumulation studies.

Toxicologists often employ the terms “biococentration and
“biomagnification”
when
describing
bioaccumulation.
Bioconcentration refers to an organism’s ability to accumulate a
contaminant significantly in excess of that in ambient water.
 Biomagnification, in turn, is the concentration of a pollutant up
the food chain, with relatively low levels accumulating in
organisms at the base of the chain and higher levels, possibly
reaching harmful or lethal amounts, in organisms at the top of the
chain.
 The responses of estuarine and marine organisms to waste inputs
are manifested on four levels of biological organization: cellular,
organismal, population, and community levels (Table 5).
3

The earliest detectable changes within the cell in response to toxic
environmental
chemicals
(xenobiotics)
involve
subcellular
organelles.
 Some biochemical processes respond specially to certain types of
pollutants (e.g., the cytochrome P450-mediated system of mixed
function oxygenation of organic compounds, and the metal-binding
proteins).
 Individual organisms display multiple responses to pollutant stress.
 Physiological response of marine organisms to pollutants depends
on the bioavailability, uptake, accumulation, and disposition of
contaminants in the body, and on the interactive effects of multiple
contaminants.

Other reproductive and developmental processes may be
adversely affected, which can ultimately lower the reproductive
and developmental potential of the population and lead to serious
long-term problems, (e.g., genetic damage).
 Chronic exposure to chemical contaminants occasionally results in
modifications of adaptive and feeding behaviors.
Changes in
population structure and dynamics may also become evident.

Individuals generally exhibit greater susceptibility to disease
when exposed to elevated contaminant levels, as manifested by
histophathological disorders that develop.
4
 Effects of an insidious and cumulative nature on communities
include graded responses to pollutants, such as:
(1) loss of rare or sensitive species;
(2) quantitative changes (e.g., in age structure) of longer-lived
species;
(3) decreased species diversity.
(4) dominance of opportunistic species.
 Benthic communities, in particular, undergo dramatic shifts in
species composition, abundance, and other parameters because of
the variable sensitivities of the constituent species to pollutant
exposure.

In these communities, acute pollutant stresses cause death in
many cases, whereas the effects of chronic pollutant stresses are
more subtle, with alterations in community structure often
ascribed
to
changes
in
growth,
physiological processes, or other factors.
5
fecundity,
recruitment,