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Marine Ecology
 The word "ecology" is of recent origin, derived from the Greek oikos
which means "house".
 This branch of biology is concerned particularly with the interactions
of organisms in the groups which they form in nature and their
relationship with the environment (their "house- keeping").

Ecology is "the study of the structure and function of nature" –
 Ecologists are concerned mainly with levels of organization beyond
that of individual organisms;

Population is a group of individuals of one kind of plant or animal.
 Community includes all of the populations in a given area.
 Ecosystem is any biological community considered together with its
non-living environment.
 A dynamic equilibrium is established in which, over the course of
time, fluctuations in one component are balanced by compensating
fluctuations in another.
 The more diverse the biological community, the more stable is the
ecosystem, because more components are available to provide these
compensating effects.
 Serious disturbances of established ecosystems are caused mainly by
un-usually severe or long-term changes in the environment or by
invasions of unfamiliar plants or animals.
 Human activities may disturb the ecological balance by reducing in
the diversity in the elimination of weeds, pests or "useless" species, by
the conscious or unintentional introduction of exotic organisms or by
modification of the environment itself.
 The history and effects of invasions of alien species mostly brought
about by man.
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 The more damaging pollutants often cause severe effects because of
their unfamiliarity; the plants and animals have developed no defenses
against them and the established ecosystem is thus very susceptible.
 By insisting that the diversity of an ecosystem is important, biologists
are consciously abandoning normal human judgments of the plants
and animals around them. All species are important to the stability of
an ecosystem, whether we think them beautiful or ugly, useful or
destructive.
 There are a number of measures of diversity by the formula d =s/n
where d is the diversity index, s the total number of species present
and n the total number of individuals of all these species.
The Marine Environment
 Sea is a very stable environment, as it is because of the high specific
heat of water and the great volume of the oceans; temperature changes
are small and take place very slowly.
 The chemical composition of sea-water is also reasonably constant,
with a bicarbonate content sufficient to maintain the pH (which is a
physico-chemical variable of great importance to all living organisms)
within a very small range.
 Although some dissolved nutrients may be in short supply in the open
ocean, adequate oxygen is supplied by the photosynthetic action of
phytoplankton throughout the depths to which light penetrates or by
solution from the atmosphere across its large surface area, and
circulated by the mixing effects of waves, currents and convection.
 The mechanical properties of water provide a support for small
organisms and a medium for the larger ones.
 Living organisms from all major kingdoms are represented in the sea.
 Temperature is
distribution
the principal
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factor regulating
geographical
 There are four major vertical divisions:
(i) PLANKTON - Floating plants and animals occupying the upper
layers, whose swimming movements (if they perform any) merely
maintain them at a selected depth (Phytoplankton and zooplankton).
(ii) PLEUSTON - Few animals of medium size which float rather
helplessly at the surface (jellyfish).
(iii) NEKTON - Larger animals, swimming powerfully enough to be more
or less independent of water movements and occurring at most depths
(fish, porpoises and whales).
(iv) BENTHOS - Bottom-living plants and animals. Animals live at all
depths. Plants are restricted to regions receiving sufficient light for
photosynthesis (Euphotic zone).
The Sea Shore
 The intertidal zone lacks the stable conditions.
 Barometric pressure or seiches (internal oscillations) can cause
differences in water level of a metre or more.
 Tides have the greatest amplitude; the sea usually retreats twice daily.
 Within twelve hours, plants and animals better accustomed to
moderate sea temperatures might be exposed in turn to hot sun and
night frosts.
 Low water also exposes shore life to drying winds and brings
problems in respiration, feeding, excretion and reproduction for
animals.
 Heavy rainfall may saturate their tissues with fresh water, while the
evaporation of a rock pool can, conversely, produce concentrated
brine.
 Waves, which merely impart a lifting motion to an object floating in
mid-ocean, expend all their energy in breaking on the shore. Whilst
developing various means of protecting itself from these unfavorable
influences.
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 Animal inhabiting the intertidal region has also to evade or defend
itself from predation by such terrestrial enemies as birds and
scavenging mammals as well as the fish, crustaceans or molluscs
which may prey on it when the tide is in.
 The lowest levels on the shore, which suffer emersion only during
fortnightly spring tides, form the sublittoral fringe.
 This generally at higher levels environmental conditions become more
demanding and fewer species are able to tolerate them.
 The most prominent elements of the sublittoral fringe are the kelps,
oar weeds and other large algae.
 The midlittoral is characterized by a covering either of brown seaweed
or of barnacles and mussels, up to about the high water mark of neap
tides.
 The supralittoral "splash zone" which is wetted by swash of Normal
wave action.
 The nature of shore life varies according to the degree to which the
shore is sheltered from the force of wind and waves.
 Sandy or muddy shores also offer few hard surfaces suitable for algae,
and other marine animals.
 In spite of the superficially lifeless appearance of such a shore,
animals and different species may attain abundances.
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Interactions, cycles and successions.
 The important of shore and shallow sea-bottom to the economy.
 Giant kelp and Sargasso weed.
 Planktonic and shallow water larvae.
 Inshore waters serve as the nursery not only of shore life, but also of
many commercially valuable fish.
 Life in the sea, as on land is ultimately depending on energy shored by
green plant.
 Energy is not normally transmitted only in a straight line, however the
situation is more realistically illustrated by "food web" (Fig 1:4) .
 Man enters this cycle not only as high-level consumer but also as
supplier of nutrients and detritus in sewage and other waste discharge.
 It has been emphasized that lower shore is the site for intense
competition for space.
 If surface were clear the following steps "succession" will occurs:
1-first colonizers are bacteria and other microscopic plants
2-larger plant and animals
3-Nature of late occupants depends on season.
4- "Climax" as community will depend both on physical and
biological features of the ecosystem.
 Experiment of boy's and objects placed in the sea.
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Water Pollution
A. Definition and General Effects
 British lawyers, define the pollution of rivers as the addition to the
water of anything which changes its properties so that the riparian
owner does not receive it in its natural state.
 Pollution: is defined as any impairment of water quality which
adversely and unreasonably affects its subsequent beneficial use. For
purposes of rapid enforcement, the term "contamination" is used to
distinguish pollution which causes a public health hazard. British law
similarly divides offensive discharges into poisonous, noxious or
polluting categories implying respectively the destruction of life,
injury to a lesser degree and the addition of materials which are foul
or offend the senses.
 Dictionary definitions also refer to the fouling or contaminating
aspects of pollution, so it should perhaps be mentioned that "fouling"
also means to marine scientists the un- desirable growth of seaweeds,
barnacles and other encrusting organisms on a ship's hull or harbour
structures.
 Biologist's pollution, more broadly, as "the addition to an
environment of any material which has a detrimental effect on the
ecosystem".
 From the point of view of control and enforcement, pollution of the
sea differs from that of fresh waters mainly in that the sea has no
owner.
 The powers of river authorities have recently been extended to tidal
estuaries, where they overlap with those of the Sea Fishery
Committees.
 Discharges into estuaries or the sea from sewage works, factories and
other large undertakings are subject to scrutiny by these and other
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bodies in the course of obtaining planning consent, and must be
licensed by the Department of Trade and Industry
 The usual and most obvious effect of pollution is to reduce diversity
of some organisms will be unable to tolerate the toxicant.
 Species could be reduced but total of "biomass" could increase as a
result of one species. (dry weight per volume or area).
 lower plants such as blue-green algae or "sewage fungus"
which form slimes and scum, or bacteria which produce evil-smelling
gases in the absence of proper aeration. Such gross impoverishment of
the environment has been reported in the vicinity of oil-refinery
outfalls, even where they carry no more than an acceptable quantity of
suspended oily matter.
 Most modern insecticides also kill at very low concentrations the
shrimps and other small crustaceans which form much of the diet of
inshore and estuarine fish. Toxicants like these persistent biocides are
cumulative and can become concentrated as they pass up food-chains,
usually affecting the long-lived carnivores at the top much more
seriously than the rapidly reproducing primary producers at the
bottom.
 Fatal neurotoxic disorders ("Minamata disease") and abnormal births
in some Japanese fishing villages have been traced to methyl-mercury
biosynthesized from industrial waste.
 Plankton in Colombia river have 2000 times the radio-activities due to
phosphourous -32 from Hanford nuclear rector.
 Tunicate are known to extract vanadium from the sea, concentrating it
from 0.0003 ppm in the water to 500 ppm in some tissue.
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B. Some Common Pollutants
 Materials which pollute water have a purely mechanical effect; silt
washed out by floods or stirred up by dredging, coal- washings or ash
dumped by industry.
 Suspended materials are not usually harmful to fish up to about 75
ppm but found that more than 100 ppm of an inert suspension
depresses the feeding- rate of oysters by 50%.
 Kelps may grow in depths of 15 m or more, the natural turbidity of
coastal waters in the west of Britain restricts them to the top four
metres.
 Some chemicals are highly poisonous - for example, copper, zinc and
chlorine kill trout at 0.1-0.2 ppm in fresh water.
 Many heavy-metal salts are only slightly soluble in sea-water, so that
the load of a polluted river is mostly deposited at its mouth, but
marine fish swallow water continuously, extracting its salts to control
their fluid level.
 Copper and zinc act synergistically, a mixture being eight times more
toxic than the same quantity of either alone. The constituents of two
effluents may also react to produce compounds of greater toxicity
(Table 2:1).
 Chlorinated hydrocarbons DDT and BHC, together with the
organophosphorous compound Parathion, kill shrimps at 0.003 ppm
although cockles survive up to 10 ppm
 The temperature in the immediate vicinity of a discharge of cooling
water may be lethal, although its effects on the organisms in the
receiving water are more likely to result in long-term ecological
changes. Heating also has the indirect effect of deoxygenating the
water and increasing the metabolic activity of its inhabitants, thus
enhancing the effects of other pollutants.
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
Detergents also reduce the oxygen tension, whilst organic wastes especially sewage solids and other discarded animal or vegetable
material.
 Domestic sewage adds to the rivers and sea vast quantities of
inorganic plant nutrients which would otherwise be in short supply
there. When the process is accelerated by such human activities - the \
"cultural eutrophication".
 Blooms of blue-green algae which occasionally occur in freshwater
reservoirs, or sea "red tide" of dinoflagellates in the sea leading to
paralytic shellfish poisoning.
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C. Toxicity Testing
 In industrial practice, a ready criterion is required for the toxicity of a
factory effluent; this is usually the death of some convenient
organism within a short test period.
 The effects of increasing concentration are cumulative (that is, in
testing any given concentration, all those individuals susceptible to
lower values will also die) so the curve will be sigmoid rather than the
familiar hump-backed shape (see Fig. 2:2).
 I n pharmacology, toxicity is expressed in terms of LDso (the dose
which is lethal to 50% of test organisms within a specified time).
When considering aquatic organisms, it is obviously difficult to
determine the actual dose which each has received, so an LC5o (the
concentration in the water which is lethal to 50% of its occupants) is
used instead, generally over a period of 24,48 or 96 hours.

This value may also be referred to as the median tolerance limit
(TLm). These are measures of the acute toxicity of the pollutant;
procedures which should be followed in making such tests are
considered.
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 I n industrial practice, it is usual to assume that the "safe" or
"permissible" concentration of a polluting discharge lies , between
one-tenth and one-hundredth of its LC5o over 48 or 96 hours.
 Safe concentration could be calculated as =
The "maximum safe concentration" in which all the fish under test
survived and the minimum concentration for 100% kill".
 If this period is considerably longer than lat of the toxicity test, then it
may receive a lethal dose by accumulation from a "safe"
concentration. The curve of intensity of some sub-lethal effect against
concentration is often a rectangular hyperbola (Fig. 2:3).
 At the lowest concentrations, a point is reached where no effect is
obtained - a "biological zero" determined by the rate of detoxication,
excretion or loss of toxicant by some process such as hydrolysis or
absorption.
 Carcinogenic materials have no safe limit, although lengthy
exposure may be necessary to produce any effect in practice, a single
molecule could potentially produce a genetic change in a cell.
 The most sensitive stage often occurs only just after hatching. When
interpreting the results of the test, it is also necessary to distinguish
between bare survival and useful life (Fig 2:4—2:6).
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