Kemi Seminal 2(1)
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Transcript of Kemi Seminal 2(1)
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1.0 INTRODUCTION
Lagoons are shallow brackish bodies of water separated from the ocean by a barriers
island or sand bank and connected at least intermittently to the open ocean by one or
more restricted tidal inlets, found on all continents, usually oriented parallel to the coast,
Lagoon system vary greatly on size from as small as hectare in area to more than
10,000km2 eg Lagoa dos patos, Brazil) ) and north merica !1"#$%), the coast of sia
!1'%) south merica 12#2% ustralia 11#(% and urope !*#&%) +he most etensive
stretch of coastal lagoons is along the atlantics and -ulf coastal united states, where day
cover . 2#'00 km of shoreline however there also common along the eastern coasts of
/outh merica and ndia, /outhern Britain and western rance, the western coast of
frica, and south eastern ustralia as well as along the shores of the Baltic, Black,
aspian and 3editerranean seas, n 4igeria, there are ten lagoons found only in south5
western 4igeria !Lagos) +hey are the 6loge, 7ewa, Badagry, yagbe, 8uramo, 6ni9edi,
Lagos, pe, Lekki and 3ahin lagoons these lagoons run parallel to the -ulf of -uinea
coastline over a distance of about 2&"km# 6ni9edi lagoon is the only closed lagoon in the
region while the 8uramo lagoon is seasonally closed and flows into the sea in the wet
season via the 8uramo ll the other eight, are open lagoons# lagoon may or may not be
sub9ect to tidal miing, and salinity can vary from that of a coastal fresh5water lake to a
hyper saline lagoon, depending on the hydrologic balance# Lagoons formed as a result of
rising sea level mostly during the :olocene and the building of coastal barriers by marine
processes# +hey are often highly productive and ideal systems for a;uaculture pro9ects
but are, at the same time, highly stressed by anthropogenic inputs and human activities#
Lagoons are common in the coastal environment of many islands# +hey are areas of water
with some link to the sea, but sufficiently cut off or protected so that there are special
environmental conditions inside them# +hey therefore present special problems forenvironmental management# +he types of lagoon depends on the form and origin of the
island and often the stage of coral reef development, since it is often coral reefs growing
up to the surface that cut off and protect an area of water, making a lagoon# ven a
fringing reef may have a depression between the reef crest and the shore, forming a
narrow shallow lagoon# barrier reef can be up to several kilometers offshore, creating a
large lagoon which may be tens of meters deep and contain island and patch reefs#
!4wilo, 1
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Figure 1: Lagoon system showing Lagos Lagoon Source: Onyema !00"#
$%ate 1: Image o& the Lagos Lagoon Source: UN'$ 1""(#
+he Lagos Lagoon is a ma9or geographical feature in Lagos, being the largest of the
network of lagoons that stretch from =epublic of Benin through to the 4igerian 4iger
>elta# ?arts of the lagoon waterfront have degenerated into slums, with mainly shanties at
various points, wood preservation, markets and sand dredging activities, robbing the area
of potential urban tourism revenue# -rowing statistics indicate financial gains in
eploiting water tourism# n recognition of this, the Lagos -overnment is pursuing an
aggressive tourism and waterfront development strategy for Lagos 3etropolis# +o
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determine the place of landscape features of the Lagos Lagoon on its viability for
tourism, the research evaluates the lagoon@s landscape characteristics and answers
;uestions of landscape perception of the area !69olowo, 2012)#
Lagos lagoon is a ma9or water body in the Lagos metropolis# t cuts across the southern
part of the metropolis, linking the tlantic 6cean !in the west and south) and Lekki
Lagoon !in the east)# t is about $&*(#"0' s;# km in area and 2'* km in perimeter#
reaA 20's; km
>epth A verage of 1m !ecept for areas that are dredged)
Length A *0km
idthA 1&km
BridgesA +hird mainland bridge, ko bridge, arter bridge
t also provides a good platform for inland waterways transportation which has
potentialities of reducing transportation problems in Lagos metropolis and a place of
abode for the some of the indigenous fishing communities such as the la9es and 9aws
!/tilts housing)# +he Lagos lagoon is one of the four ma9or lagoons in the 4igerian
coastal system, and a significant tourist attraction centre in Lagos /tate# >ue to the level
of primary production in the lagoon, it is usually inhabited periodically by fish species of
fresh water and marine origins, in search of food and good nursery ground !mmanuel,
2010)# t has been reported that about &(% of fishes observed in this ecosystem are of
freshwater origin and the remaining being marine# 3ullets, sardine and bonga
!lupeidae) were classified as permanent fishes in this habitat# +he fisheries productivity
of the Lagos Lagoon system is put above "* kgChaCyear and the fishermen from the
4igerian coastal lagoon and estuaries contribute more than *0% of the current domestic
fish production of about '00,000 metric tons# t was also reported that about 2' metric
tonnesChaCyear of oysters are produced annually from this ecosystem# s a result oflagoon@s rich fauna, especially in fishes, fishing activities are usually witnessed on a daily
basis# =ecently, the state government is proposing using the Lagos Lagoon for cage
culture as a form of contribution to food security and research# ish and fisheries
products are generally regarded as an important part of a healthy diet# n the developing
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ountries, fish and fisheries products apart from being a source of cheap animal protein,
are widely consumed as they have high ;uality protein and other essential nutrients, and
are low in saturated fat while containing 6mega & fatty acids# n 4igeria, most
investigations of the Lagos Lagoon have focused on the sediments and benthic
communities, the diversity and density of macrobenthic fauna in the western part of the
lagoon, trend of heavy metals concentrations are in the Lagos Lagoon, the food and
feeding interrelationships of the fishes and the biology of some fishes and the fisheries#
+here is however, a need to update most of these studies and provide current information
on the diversity of the edible fishery and the effects of pollutants on the health and
abundance of these organisms inhabiting the Lagos Lagoon# By virtue of its position, the
Lagos Lagoon is surrounded by the densely populated !about fifteen million people) and
highly industrialized Lagos metropolis, making it a convenient dumping site for
numerous industrial and domestic wastes, an estimated 10,000 m& of industrial effluents
are discharged into the Lagos Lagoon per day# +hese estimates also confirmed that the
industries are the ma9or source of metal contaminants in the drains, streams and lagoon,
since the graded prominence of metal types was similar in the sampled effluents and
a;uatic systems !delegan, 200()#
+he continued discharge of all sorts of untreated waste materials into the lagoon threatens
the state of ecological e;uilibrium and diversity of fisheries resources in the lagoon, theuse of the lagoon as a dump for waste materials has reduced annual fish production in the
Lagos Lagoon by over five folds between 1
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Lagos Lagoon have focused on the sediments and benthic communities, the diversity and
density of macrobenthic fauna in the western part of the
Lagoon, trend of heavy metals concentrations are in the Lagos Lagoon, the food and
feeding interrelationships of the fishes and the biology of some fishes and the fisheries#
+here is however, a need to update most of these studies and provide current information
on the diversity of the edible fishery and the effects of pollutants on the health and
abundance of these organisms inhabiting the Lagos Lagoon# By virtue of its position, the
Lagos Lagoon is surrounded by the densely populated !about fifteen million people) and
highly industrialized Lagos metropolis, making it a convenient dumping site for
numerous industrial and domestic wastes, an estimated 10,000 m& of industrial effluents
are discharged into the Lagos Lagoon per day# +hese estimates also confirmed that the
industries are the ma9or source of metal contaminants in the drains, streams and lagoon,
since the graded prominence of metal types was similar in the sampled effluents and
a;uatic systems !delegan, 200()# +he Lagos lagoon system is the largest of the four
lagoon systems of the -ulf of -uinea !hukwu, 2002)# +his a;uatic ecosystem is habitat
to a variety of biota which include the plankton, nekton and benthos in a comple trophic
interrelationship !mmanuel and 6nyema, 200")# +he Lagos lagoon ecosystem is habitat
to a variety of biota which include the plankton, nekton and benthos in a comple trophic
interrelationship !mmanuel and 6nyema, 200")#
ccording to by 6nyema !200
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FIN )ND S*'LL FIS*
ommon fin and shellfish in the Lagos lagoon include our species of cichlidae were
identified# +hey are Sarotherodon melanotheron, !emichromis fasicatus and "ilapia
guineensis# 6ther species include larias gariepinus hrysichthys nigrodigitatus
aran$ hippos, %ugil cephalus,Bathygobius soporator, &leotris vitata, Batanga
lebretonis and Gobioides africanus, 'phichthus rufus and Li(a falcipinnis# /ome
common shellfishes were allinectes amnicola, Penaeus notialis, %acrobrachium
vollenhoevenii and%acrobrachium macrobrachion#
+he continued discharge of all sorts of untreated waste materials into the lagoon threatens
the state of ecological e;uilibrium and diversity of fisheries resources in the lagoon, the
use of the lagoon as a dump for waste materials has reduced annual fish production in the
Lagos Lagoon by over five folds between 1
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Lagoons that are open to the sea may have many of the same corals, fish and other sea
life as well as the ocean itself !?edro, 200()# s the conditions in a lagoon get more
variable and more etreme, the number of kinds of things that can live there will get
smaller and smaller, although those things that can live there may get to be more
common# +he life of lagoons may be more productive and abundant than in the sea
outside if there are nutrients that go into it from the land, or if it is able to accumulate
nutrients because it is protected# +he shallow lagoon bottom is often covered with beds of
sea grass or sea weed and reef corals may grow on the lagoon edges and on patch reefs
within it# t may provide important breeding or feeding areas for fish or other animals
outside the lagoon as well# /ome lagoons support fisheries that are very important for the
island# +hey may have bait fish that can be used to fish while some certain lagoons have
important beds of pearl oyster others may have shell fish that are collected locally for
food !Lawal, 200')# f a lagoon becomes too closed, however, there may not be enough
water echange and the lagoon may become stagnant and support much less life# +here
may even be no oygen left on the bottom for animals to live, because the lagoon
environment is often less managed there may be big changes in the kinds of plants and
animals that grow there something may multiply until it seems to be everywhere then it
may die off, to be replaced by something else# +hese changes may follow the season or
they may happen without any apparent reason !6yewo, 200()#
Lagoons like the other parts of the coastal system may go through important changes over
a long period of time the coral reef may grow up and cut them off more and more from
the ocean !Brown, 2012)# +hey may gradually fill up with sediment until they become
part of the land# f the island is sinking, a lagoon may gradually lose its protective barriers
and become part of the ocean shoreline, if the island is rising, the lagoon may be lifted up
until its bottom is dry land, sometimes a natural change may seem sudden, as when a
growing reef finally stops the flow of the ocean water into a lagoon#
astes and run off from the land may also collect in a lagoon and pollute it# /ome islands
have had cholera epidemics spread by the pollution of seafood caught in the lagoon#
Lagoons are particularly vulnerable to the development of towns or cities around their
edge !E4?, 200()#
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Lagoons are epenses of shallow coastal salt water of varying salinity and water volume,
wholly or partially separated from the sea by sand banks or less fre;uently by rocks#
/alinity may vary from brackish water to hypersanility depending on rainfall, evaporation
and through the addition of fresh sea water from storms, temporary flooding of the sea in
winter or tidal echange# n addition, salinity is one of the ma9or factors that determine
the types of plants and animal that lives in a lagoon#
+he characteristics of many lagoons !e#g# low fishing or high retention times, fine
sediments stratification species restricted to lagoons)# n lagoons the low fishing times
means that internal processes !biological and geochemical) will have a significant effect
!?earce, 2012)# Biological processes will include increased phytoplankton growth in
response to nutrient inputs, subse;uent death and retention of the resulting organic
particulate matter and retention of nutrient arising from breakdown of this organic
material# ?articulate nitrogen in the forum of detritus , for eample, from benthic and
floating macrophytes that respond opportunistically to nutrient enrichment, is also likely
to contribute to the internal source of nutrients for subse;uent to take by algae# 6ther
eamples that contribute to a perpetuating state that affect a lagoon include reduction in
benthic pelagic coupling, changes to benthic food webs and the uncoupling on
nitrification identification !6nyema, 200$)# s a conse;uence of the few case studies of
lagoons and observations in similar systems to lagoons in con9unction with the
characteristics of lagoons, it is concluded that many, if not most saline lagoons would
have a low recovery potential from water ;uality impact and eutrophication impacts
within accepted management and planning time frames#
fter a long day in the full sun, lagoon temperatures can rise ;uite high# f the lagoon is
deep enough and the water miing caused by the wind does not reach to the bottom, thena thermocline may develop !E4/6, 200
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+ransportation !boats and canoes are involve in transporting goods and humans from one
part to another)#
ishing activity !fishing operation is purely at artisanal level)#
n ideal centre for education and scientific research#
Lagoons can also create avenues for harbours and ports development s natural
environment of fishing activity is always very high however, fishing operation is purely
at artisanal level#
=ecreational uses of lagoons involve boating in lakes and natural swimming pools mainly
because of their shelter and conse;uent lack of strong wave action#
Lagoons can be considered as models of the larger marine ecosystem#
Lagoons can also create avenue for harbour@s and ports development#
Im+ortance o& Lagoons
1# oastal lagoons have eceptional ecologic, recreational and commercial value
2# +hey provide diverse habitats !open water, submerged a;uatic vegetation, creeks
and fringing wet land)
+hey serve as nursery, feeding and refuge areas for numerous estuaries, marineand terrestrial orgs many marine sp# 6f recreational and commercial imp# /pend at
least a portion of their life cycles in lagoon and ad9oining coastal wetland habitats#
(# side from the value of their fisheries, coastal lagoons are used by humans for
a;uaculture, electric power generation, biotechnology, transportation and shipping
industries in9ect billions of dollarsCnaira into the economies of coastal region
worldwide#
*# Lagoons serve as number of vital physical and chemical functions involving the
trampy and transformation of nutrient and wastes, filtering of contaminant, and
biogeochemical cycling of substance# +hey therefore can strongly influence the
enital ;uality of coastal :2os#
6. Lagoons also protect coastal watershed are buffering the infrastructure from the
damaging effects of storms, floods and erosion.
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6n the aspect of conservation, it is important we manage and conserve biological
diversity and succession in our coastal waters in order to avail ourselves of the capacity
to counteract negative impacts caused by human beings# lot more effort needs to be
made in order to create awareness about the environment# e should learn from
eperiences of the developed world where they are relatively poor in biodiversity because
they have gained their current ;uality of life at the epense of their biodiversity of
neighbouring countries# ?eople should develop positive attitudes and conserving
behaviour towards the natural resources#
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2#0 T,$'S OF L)-OONS
orms and types of Lagoons !Base on lassification)#
89efre !1
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.0 F)CTORS )FF'CTIN- L)-OONS
?ollution is the introduction by man directly or indirectly of substances or energy into the
a;uatic environment resulting in such deleterious effect as to harm living resources,
hazard to human health, hindrance to a;uatic activities including fishing and impairment
for use of water and reduction of amenities# +he ma9or sources of pollution in the lagos
lagoon are land based#!onyema et al#,200&)# :owever, they may be grouped into twomain sources depending on their mode of entry into the water
i# ?oint source !direct discharge)
ii# 4on5point source !diffuse)#
+he point source include the domestic waste, human and solid waste, waste arising from
petroleum related industries, commercial and industrial activities# +he non5point source
includes agricultural runoff containing nutrients and pesticides, urban run5off and soil
erosion# +hese pollutants can be either natural or unnatural substances and can be
grouped into four types depending on their nature and mode of eistence,
i# ?hysical pollutantsA including discarded ob9ects, weeds, silt clay, other sediments
and decaying organic matters#
ii# hemical pollutantsA toic heavy metals such as cadmium, nickel, organic
pollutantH pesticides, phenols#
iii# 3icrobial pollutantsA microorganism resulting from pollution !sewage) of waters
e#g scherichia coli#
iv# =adioactive pollutantsA include radioactive substances such as radium 22$#
Listed below are the ma9or sources of land based pollution
>omestic waste
ndustrial wastes
gricultural runoff
Erban runoff
/olid and human waste
Domestic wastes
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/ewage pollution of surface waters !lagos lagoon) is a common and consistent
occurrence# +he carter bridge end of the lagos harbour served as a disposal site for
untreated domestic sewage in the lagos municipality# or years, the deterioration and
etrophication of the lagos lagoon water have been steadily accelerating which is primarily
due to the etensive pollution by large ;uantities of industrial and domestic sewage
introduced into the water# +he abundance and distribution of faecal bacterial in the lagos
lagoon is influenced by the salinityof the water# Lower counts of # coli were observed at
the southward area of the lagoon which reccieved seawater from the harbour, while
higher counts were recorded in areas which receive freshwater from river ogun# lso
seasonal variations were observed in the distribution of faecal indicator bacterial in lagos
lagoon# :igher counts were observed during the rainy season when the salinity of the
water is low and the lagoon receives runoff from land#
kundayo !1ifferent industries produce different kinds of products and the type of industrial activity
determines the pollutant generated# 6f all the industrial effluents from various industries,
the waste waters from the petroleum related industry and oil spillage constitute a ma9or
land based source of pollution of 4igerian coastal waters# ctivities of crude oil
eploration and eploitation are to a very large etent going on in all parts of the 4iger
delta# 6il spills originate from sources which includeH oil wells, refineries, oil terminals
and 9etties#
6ther sources of oil pollution include petrochemical plants, numerous oil servicingcompanies which pollute the waters with spent oil grease and other chemical mitures
!adhekpukoli, 1
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$%ate 2: Fish /eath associate/ to chemica% +oisoning &rom in/ustria% +o%%ution.
Source: Se%& ac3uire/ !014#
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)gricu%tura% runo&&
+he campaigning for increased food production in 4igeria has resulted in the
establishment of large farms by a number of individual and companies# Large scale
agriculture often involves the use of fertilizers for improved growth of crops and
pesticides for control of pests# +hese fertilizers could be a source of water pollution
especially during rainy seasons when they are washed from farmlands into wetlands#
Lagos has some odour and taste in 3ay, 1
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2.0 )D)$T)TION OF OR-)NIS7 IN L)-OONS
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4.0 $*,SIO6C*'7IC)L $)R)7'T'R OF T*' L)-OONS
?:7/L 4> :3L +6=/ D=+64/ 4 L-664/
$*,SIC)L
+ides
+emperature
urrents and waves
>epth
+ransparency
olour
urrent
C*'7IC)L
/alinity
p:
4utrients
onductivity
>issolved 6ygen
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8.1.1 7)N)-'7'NT )ND STR)T'-I'S ON *O TO I7$RO9'
'N9IRON7'NT)L ST)T' OF L)-OOS
The &o%%owing management strategies are o&ten +ro+ose/ to im+roe theenironmenta% state estuaries an/ coasta% %agoons:
ncrease monitoring and research to identify impacts and to develop remedial actions thatrestore natural environmental conditions#
?ursue open space ac;uisition and smart development in coastal watersheds to protecthabitat# mplement effective restoration efforts to revitalize altered habitat#
ormulate tighter regulations to limit nutrient and chemical contaminant inputs to estuar5ies and lagoons#
stablish more estuarine reserves to minimize anthropogenic impacts, and to provide pro5tected areas for basic and applied research#
mprove the management of estuarine fisheries to preclude ecessive use or overharvestcommercially and recreationally important finfish and shellfish populations#
3onitor, assess, and remediate water ;uality and habitat degradation associated with a;uHculture operations#
ncrease the interactions between scientists, resource managers, and policy makers tensure informed decisions regarding estuaries and coastal lagoons#
>evelop education and outreach programs that inform students and the general public theimportance of maintaining healthy and viable estuarine and lagoonal environments#
Organi;ations an/ 5o/ies such as
ederal nvironmental ?rotection gency !?)
>epartment of ?etroleum =esources !>?=)
4igerian nstitute for 6ceanography and 3arine =esearch !463=)
ll these bodies including -overnment ministries of transportation, works and
agriculture have a key role to play in the protection and conservation of environment#
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(.0 R'F'R'NC'
)/am= $.7. D. >ertness= ). ?. Day= an/ @e/%er ?.>. !00(#. Sa%tmarsh. In: N. 9. C.
$o%unin e/.#=Aquatic ecosystems: Trends and global prospects.
Cam5ri/ge: Cam5ri/ge Uniersity $ress. $+. 14oca Raton= F%ori/a: CRC $ress. . $+.1168!.
>ere= $.R. an/ 7anta6Conroy= 7. !000#. )re we +%anning &or sustaina5%e /ee%o+mentE
)n ea%uation o& 0 com+rehensie +%ans. J. Am. Plan. Assoc.88: $+!16.
>a/si= h. O%i%a/a%i= *. Lou/ii 7. '%ha&a= 7. Cha%i= R. an/ )amiri= ). !010# 'co%ogica%
&actors a&&ecting the /istri5ution o& ;oo+%anton community in the 7)SS)
%agoonSouthern 7orocco#African Journal of environmental science and technology.
9o%211#= $+
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)ag5e F.'.= Osi5ona O.). an/ Otito%ou= ).). !01!#.Diersity o& the e/i5%e &ishes o& the
Lagos
%agoon.Internationa% ourna% o& &isheries an/ a3uacu%ture. 241#: 24642.
)ao= '. ).= Oyewo= '. an/ Unyima/u= ?. $. 1""8#. ) reiew o& the $o%%uton o& Coasta%
aters in Nigeria . NIO7R Tech $a+er.No. 10o%+s.
Inestment Limite/= Lagos= Nigeria. !18++.
>ir/= '. C. F. 1"(!. Changes on 5arriers an/ s+its enc%osing coasta% %agoons.
'ceanologica Acta2464.
>ir/= '. C. F. 1""2. $hysica% setting an/ geomor+ho%ogy o& coasta% %agoons. $+. "6"= In: >.
er&e e/.#= Coastal lagoon processes.)mster/am: '%seier.
*ein; Center= !00!.!uman lin(s to coastal disasters.ashington= D.C.: The *. ?ohn*ein; III Center &or Science= 'conomics an/ the 'nironment.
$h%eger= F. >. 1"8". Some genera% &eatures o& coasta% %agoons. $+. 46!8= In: ).
)ya%a6Castaneres e/.#= agunas costeras" unsimposio= Uniersi/a/
Naciona% )utonoma /e 7eHico= 7eHico= DF.
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O/iete= .O.= Nwaooro. R.C. an/ )/aramo%a= T. !00#. >io%ogica% assessment o& &our
water courses in Lagos metro+o%is receiing in/ustria% an/ /omestic waste
/ischarges.Journal of #igerian Environment Society.11#: 1612.
OUTLIN'
1.0 INTRODUCTION
De&inition o& %agoons
Im+ortance o& %agoons
!.0 T,$'S )ND FOR7 OF L)-OONS >ase on c%assi&ication#
.0 F)CTORS )FF'CTIN- L)-OON
2.0 )D)$T)TION OF LIF' IN L)-OONS
4.0 $*,SIO6C*'7IC)L $)R)7'T'R OF T*' L)-OONS
8.0 7)N)-'7'NT )ND STR)T'-I'S ON *O TO I7$RO9'
'N9IRON7'NT)L ST)T' OF L)-OONSS
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