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CHAPTER ONE
1.0 BACKGROUND INFORMATION
Lagoon is derived from the Italian word laguna, which refers to the waters
around Venice, the Lagoon of Venice. Laguna is attested in English by at
least 1612, and had been Anglicized to "lagune" by 1673. In 1697 William
Dampier referred to Lagune or Lake of Salt water on the coast of
Mexico.[Lagoons are prominent features along the coastal regions of
South-Western Nigeria. Some of these Lagoons are part of West African
lagoon system in origin and location but are in form and features similar to
freshwater lakes (Webb, 1958). The other types of lagoons are essentially
brackish and tidal effects are experienced particularly in the dry season.
However, all the lagoons of south-western Nigeria enter the sea through
the Lagos Harbor (Nwankwo, 1998a). Epe lagoon the only lagoon in south-
western Nigeria sandwiched between two lagoons (Lagos and Lekki
lagoons).
Out of the six lagoons (Mahin, Lekki, Epe, Lagos, Ologe and Yelwa) on
the south-western coast, the Lagos lagoon is the most extensively studied
in relation to the others. This may obviously be attributed to the
metropolitan nature of Lagos and the ease of access.
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Just like every other environment of deposition, sediments are deposited in
the Lagoon. Microfossil assemblages in lagoon sediments contain many
valuable clues to paleoclimate and paleo-oceanography, Water Quality.
Unfortunately, our understanding of production, dissolution, redisposition,
and other processes of microfossil sedimentation is but rudimentary.
Lacking direct observations, information largely rests on comparisons
between abundance and composition patterns of life-, death, and sediment-
assemblages (Berger 1971).
According to (Sattarova et al, 2015), Diatom assemblages reflect present-
day water masses characterized by high nutrient content, surface water
circulation, and sedimentation conditions for different parts of the study
area. Analysis of this new data also highlights changes in the response of
diatom flora due to abiotic factors.
Several microfossil groups are particularly useful in bio-stratigraphic
correlation, paleo-environmental reconstruction, and paleoceanography
(Braiser 1995).
Thus, Diatoms are used extensively in environmental assessment and
monitoring.
Furthermore, because the silica cell walls do not decompose, diatoms in
marine and lake sediments can be used to interpret conditions in the past.
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Paleoecology is a field that utilizes both living and subfossil diatom valves
that are preserved in marine and freshwater sediments (Smol et al 2010).
1.1 STATEMENT OF PROBLEM
Epe lagoon lays in-between two lagoons the Lagos and the Lekki lagoons
which are relatively more documented. The paucity of information on the
micro-paleontological characteristics of this sandwiched lagoon prompted
this present work. A survey of the microfossil of the sediment from Epe
lagoon was carried out in the early April 2015.
The micro-paleontological studies of the Epe lagoon have been carried out
very few times in recent survey. The types of microfossils present; their
structures, morphology, shape, age-range is less known. This study will
add to the wealth and body of existing information and present a more input
into further studies. The study of microfossils, particularly in fresh water
lagoon is used to infer the depositional environment of the lagoon, at the
same rate they are also used for paleo-environmental reconstruction. But
due to the low level of micro-paleontological research carried out in the
Epe lagoon, inferring the depositional environment may pose a difficult
task.
To a very large extent, this research work will be able to proffer solutions
the aforementioned challenge.
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1.2 AIM
The aim of this study is to determine the microfossil composition of the
Epe Lagoon sediments; its morphology and its characteristics. Also, to use
the microfossils present to infer the depositional environment of the
lagoon.
1.3 OBJECTIVES
Objectives of the study include;
-Identification of Microfossils (Diatoms) present in the sediments
-Estimating the percentage composition of each component
-Identifying Microfossils that serve as indicators
1.4 DESCRIPTION OF THE STUDY AREA
1.4.1 Location of Area
Epe lagoon is located in Lagos state, South-west Nigeria; it lays in-between
two lagoons, the Lagos lagoon (Brackish water) to the west and the Lekki
lagoon (Fresh water) to the east, both of which are relatively more
documented (Fig 1).
Epe lagoon is connected to the Atlantic Ocean through the Lagos harbor,
It lies between longitudes (N 06o 33.710 o E 004 o 03 o.710) and latitudes
(N06 o 31.893o E 003 o 31. 912 o). The Epe lagoon has a surface area of 243
km (Kusemiju 1988).
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The lagoon has an average depth of about 1.8m and a minimum depth of
2.8m. (Edokpayi et al, 2008).
The Epe lagoon supports a major fishery in Lagos state, Nigeria and it is
also used as transportation route for people, goods and timber logs from
Epe to other places in South-Western Nigeria. The lagoon houses the Egbin
thermoelectric power plant which serves as a major source of electric
power generation in Western Nigeria. The lagoon is the major source of
water for the inhabitants of Epe and other villages situated along its bank.
Over the years the population of Epe and other villages along the bank of
the lagoon has increased through expanding commercial activities.
1.4.2 Climate
The wet and dry seasons are observable in the climate of southwestern
Nigeria, which is tropical in nature. The temperature ranges from 21 to 34
0C, while the annual rainfall ranges from 150mm to about 300mm
(Faleyimu et al., 2013). There are two peak periods of annual rainfall,
which are June to July and September to October, with a slight break in
August referred to as “August break” (Onakomaya, 1992; Ikhane et al
2013). The wet season is associated with the southwest monsoon wind
from the Atlantic Ocean, while the dry season is associated with the
northeast trade wind coming from the Sahara desert. Due to its closeness
to metropolitan cities of Lagos state the settlement sites are characterized
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by floating mate of aquatic vegetation dominated by water hyacinth
(Eichhornia crassipes).
1.4.3 Rainfall
Rainfall season is characterized by two equinoctial maxima in Lagos state
and its environs. Mean monthly rainfall varies between 19mm and 64mm
during the dry season (November to March). During the rainy season
(April-October), mean monthly rainfall ranges between 162mm and
237mm. The first rainfall maxima experienced between May and July is
intense and could be characterized by abnormal rain amounts of between
200 and 264mm daily (Awosika et al., 2011).
1.4.4 Temperature
Air temperature in and around Lagos state vary from high to very high
throughout the year. The maximum temperatures in Lagos range between
32oC and 35oC. These high temperatures are experienced between the
months of January and March (pre-rainy season). Minimum air
temperature in Lagos ranges between 22.5oC and 26.0oC in January, July
and August. However, there are certain periods in January, July and August
when minimum temperatures exceed 25oC. Temperatures in July and
August are unusually low, (between 23oC-25oC).
1.4.5 Vegetation
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The vegetation around the Epe lagoon (its shores) is characterized by still
rooted trees, the most discernible is the palm trees ranging in heights. There
is also the presence of water hyacinth, Eichhomia crassipes usually are
very many at the edges of the lagoon and also floating like an island on the
surface of the lagoon water. There is also the presence of mangrove trees
e.g. Rhizophora racemosa sp.
Study site: Epe lagoon (2°50′-4°10′N, 5°30′ - 5°40′E)
Fig 1 Epe Lagoon bounded the Lagos and Lekki Lagoon (Clement Aghatise 2011) 1.5 Literature Review
As their name implies, microfossils are very small remains of organisms
that require magnification for study. Collectively, they range in size from
less .001 mm (1 micron), which is invisible to the naked eye, to the 1 mm
size of a coarse sand grain, although some forms grow up to 20 cm. The
latter are still referred to as microfossils because they belong to the same
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taxonomic group as the minute forms, and they also require microscopic
study for identification. Whereas plants, invertebrates, and vertebrates are
distinct taxonomic groups, the paleontology sub-discipline of
micropaleontology encompasses a heterogeneous array of minute fossils.
They can be plant or animal, unicellular or multicellular, mineralized or
organic, shells or skeletons, seeds or spores, teeth or jaws, or enigmatic
forms of unknown affinity. Because they are so small, thousands of well-
preserved specimens can be retrieved from a small sample of sediment or
sedimentary rock (Bignot, G., 1985).
Micropaleontology can be roughly divided into four areas of study on the
basis of microfossil composition:
a) calcareous, as in coccoliths and foraminifera,
b) phosphatic, as in the study of some vertebrates,
c) siliceous, as in diatoms and radiolarians
d) organic, as in the pollen and spores studied in palynology.
Tests carried out in this project were aimed at determining the microfossil
composition of the Epe Lagoon; its morphology and its characteristics
details, where results will be used to infer the depositional environment for
paleo-environmental reconstruction.
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A total of 11 sediment samples preserved with formalin were collected
from the lagoon, the various samples composed of microfossils from
various location points of the lagoon notably.
Microfossils of interest in the Epe Lagoon are diatoms, Acid clean
preparation were used to treat the samples to isolate the diatoms present in
the samples.
The most common siliceous microfossils in Quaternary deposits are the
frustules of diatoms whose dimensions are of the order of 10 to 100
micrometers. Diatoms are indeed the dominant component of primary
productivity in most marine and lacustrine environments. Their
concentrations can reach millions of individuals per litre in the water
column, and hundreds of millions of frustules per cubic centimeter in the
sediment.
Diatoms are photosynthesizing algae; they have a siliceous skeleton
(frustule) and are found in almost every aquatic environment including
fresh and marine waters, soils, in fact almost anywhere moist. They are
non-motile, or capable of only limited movement along a substrate by
secretion of mucilaginous material along a slit-like groove or channel
called a raphe (Boardman, R. S 1987), Being autotrophic they are restricted
to the photic zone (water depths down to about 200m depending on clarity),
both benthic and planktic forms exist,
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According to (Jones, D. J., 1956) many of the commonly studied groups
are unicellular, such as Foraminifera, Calcareous Nanoplankton (e.g.
Coccolithophorids, discoasters), Dinoflagellates, Acritarchs, Diatoms and
Radiolarians. Others are Microinvertebrates (e.g. Ostracodes) or parts of
Macroinvertebrates (e.g. Conodonts), reproductive bodies of plants (e.g.
spores and pollen), or of uncertain affinity (e.g. chitinozoans)
The studies have been primarily on Diatoms, which are unicellular,
although they can form colonies in the shape of filaments or ribbons
(e.g. Fragilaria), fans (e.g. Meridion), zigzags (e.g. Tabellaria), or stars
(e.g. Asterionella). A unique feature of diatom cells is that they are
enclosed within a cell wall made of silica (hydrated silicon dioxide) called
a frustule (Museum of Paleontology, California 1990).
Diatoms generally range in size from 2 to 200µm (Grethe et al 1996) and
build intricate hard but porous cell walls (called frustules or tests)
composed primarily of silica (Homer 2002). Sometimes, they can be up to
2 millimeters long, the cell may be solitary or colonial (attached by mucous
filaments or by bands into long chains). Diatoms may occur in such large
numbers and be well preserved enough to form sediments composed
almost entirely of diatom frustules (diatomites) (Boardman, R. S 1987).
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This siliceous wall can be highly patterned with a variety of pores, ribs,
minute spines, marginal ridges and elevations; all of which can be used to
delineate genera and species. The cell itself consists of two halves, each
containing an essentially flat plate, or valve and marginal connecting, or
girdle band. One half, the hypotheca, is slightly smaller than the other half,
the epitheca (Lipps, J. H. 1981).
Various attempts have been made to classify diatoms, Diatoms
morphology varies although the shape of the cell is typically circular, and
some cells may be triangular, square, or elliptical.
Diatoms are traditionally divided into two orders:
• centric diatoms (Centrales) (now called the Biddulphiales) which
have valve striae arranged basically in relation to a point, an annulus
or a central areola and tend to appear radially symmetrical.
• Pennate diatoms (Pennales) (now called Bacillariales) which have
valve striae arranged in relation to a line and tend to appear
bilaterally symmetrical. The former are paraphyletic to the latter.
The valve face of the diatom frustule is ornamented with pores (areolae),
processes, spines, hyaline areas and other distinguishing features. It is these
skeletal features which are used to classify and describe diatoms, which is
an advantage in terms of palaeontology since the same features are used to
define extant species as extinct ones.
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Also, (Medlin et al 2004) propose the following classification for the
diatoms
- Bacillaryophyta
- Coscinodiscophytina
- Coscinodiscophyceae (radial centric)
- Bacillariophytina
- Mediophyceae (polar centric)
- Bacillariophyceae (pennate diatoms) The classification system developed by Simonsen (1979) and further
developed by Round et al. (1990) is currently the most commonly accepted.
Diatoms commonly found in the marine plankton may be divided into the
centric diatoms including three sub-orders based primarily on the shape of
the cells, the polarity and the arrangement of the processes. These are the
Coscinodiscineae, with a marginal ring of processes and no polarity to the
symmetry, the Rhizosoleniineae with no marginal ring of processes and
unipolar symmetry, and the Biddulphiineae with no marginal ring of
processes and bipolar symmetry. The pennate diatoms are divided into two
sub-orders, the Fragilariineae which do not possess a raphe (araphid) and
the Bacillariineae which possess a raphe.
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Fig 2 Image of Centric Diatoms (microfossil image recovery and circulation and
learning education 2012)
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Fig 3 Image of Pennate Diatoms (microfossil image recovery and circulation and learning
education 2012)
Diatoms have been studied since the late eighteenth century, however the
first real advances in the field came in the early nineteenth century when
diatoms were popular with utilising the emerging improvements in
microscope resolution. Several European workers produced hand
illustrated monographs on diatoms in the late nineteenth century. Notable
amongst these are the works of Cleve, Ehrenberg, Grunow, Schmidt and
Van Heurck. In the early twentieth century fossil diatoms were first studied
and, most famously, Hustedt (1927-1966) produced a taxonomic and
ecological study of diatoms which remains a key reference today. Perhaps
the most complete treatment of diatoms is that of Round et al. (1990).
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Diatoms can build up and produce oozes or diatomite. Diatoms are good
stratigraphic markers covering the Cretaceous to present, but are mostly
used in Neogene biostratigraphy. The distribution of diatoms depends upon
temperature, salinity and chemical characteristics of water such as pH and
nutrients. Diatoms are useful in paleo-limnology.
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CHAPTER TWO
REGIONAL GEOLOGY
2.1 INTRODUCTION
The Benin (Dahomey) Basin is a component of a system of West African
peri-cratonic basin (Klemme, 1975; Kingston et al., 1983) formed during
the early stage rifting associated with the opening of the Gulf of Guinea, in
the Early Cretaceous to the Late Jurassic (Burke et al., 1971; Whiteman,
1982).
Basement subsidence were generated as a result of rifting and graben
formation which likely began in the Late Jurassic to Early Cretaceous,
thereby giving rise to massive deposition of non-marine thick sequence of
pebbly sands and continental grits. These sequences along with the
basement complex were tilted and block-faulted in the late Cretaceous
giving rise to a series of grabens and horsts (Omatsola and Adegoke, 1981).
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Fig. 4 General geological framework of the Dahomey Basin (Modified after Bilman, 1992)
Fig. 5 Geology of the Nigerian Sedimentary Basin (OLANIYI ODEBODE)
The crustal separation which gave rise to the Dahomey Basin was preceded
by crustal thinning and accompanied by a long period of thermally
influenced basin subsidence through the Middle –Upper Cretaceous to
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Tertiary times as the South American and the African plates entered a drift
phase to accommodate the emerging Atlantic Ocean (Mpanda, 1997). The
basin extends from southeastern Ghana in the west, through southern Togo
and southern Benin Republic to the western flank of Niger Delta in
southwestern Nigeria. The Ghana Ridge, believed to be an offset extension
of the Romanche Fracture Zone, binds the basin to the west while the Benin
Hinge Line, a basement escarpment which separates the Okitipupa
Structure from the Niger Delta basin binds it to the east. The Benin Hinge
Line defines the continental extension of the Chain Fracture Zone (figure
2.1). In the onshore the basin occupies a broad arc-shaped profile area of
about 600 km2 in extent. It attains a maximum width of about 130km in the
N-S axis around the Nigerian/Republic of Benin border. The basin narrows
to about 50 km on the eastern side where the basement assumes a convex
upwards outline with accompanying thinning of sediments. Along the
northeastern margin of the basin where it makes contact with the Okitipupa
high (Ekweozor and Nwachukwu, 1989).
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Table 1 Stratigraphy of the Eastern Dahomey Basin as coupled by various authors
A good number of scholars including Jones and Hockey (1964); Ogbe
(1972); Omatsola and Adegoke (1981); Billman (1992), Nton (2001);
Elueze and Nton (2004), Ministry of Mines and Steel Development
(MMSD, 2010) etc. have analyzed the stratigraphy of the eastern Dahomey
basin and came up with different classifications as shown in table 1.1. The
major differences in the various classifications are in the area of
nomenclatures and age assignments of the lithological units in the basin.
The paragraphs below give brief descriptions of the lithostratigraphic units
of the Cretaceous to Tertiary sedimentary sequences of the eastern
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Dahomey basin as put up by Omatsola and Adegoke (1981). The described
units starting from the oldest are the Ise Formation, Afowo Formation,
Araromi Formation, Imo group, Ilaro Formation and Coastal Plain/Benin
Sands Formation. Agagu (1985) however is in agreement with John and
Hockey (1964) and Reyment (1965) that Recent Alluvium overlies the
Coastal Plain Sands.
2.1.1 Ise Formation
The Ise is the oldest formation in Abeokuta Group and unconformably
overlies the Precambrian basement complex. It comprises a basal section
of predominantly conglomerates which gives way to gritty coarse to
medium-grained loose sands interbedded with whitish kaolinitic clays. The
formation is essentially sandy. The maximum thickness of the member is
about 1865m and the age has been given to be Neocomian.
2.1.2 Afowo Formation
Succeeding the Ise formation is the Afowo Formation and is Neocomian -
Albian in age based on its palynomorph content. It indicates the
commencement of deposition in a transitional environment after the entire
basal and continental Ise Formation. The sediments are composed of
interbedded sands, shales and clays, which range from medium to fine
grains in sizes. The formation has been found to be bituminous in both
surface and sub-surface sections.
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2.1.3 Araromi Formation
The Araromi Formation is the topmost unit of the Abeokuta Group and the
sediments represent the youngest topmost sequence in the group. The
formation is composed of shales, fine-grained sand, thin interbeds of
limestone, clay and lignite bands. It is an equivalent of a unit known as
Araromi shale by Reyment. The shales are grey to black in colour, marine,
and rich in organic matter. The age ranges from Maastrichtian to
Paleocene.
2.1.4 Imo Group
The Imo group consists of the two lithostratigraphic units namely Ewekoro
and Akinbo Formations. As observed at Ewekoro and Sagamu quarries as
well as cored sections at Ibeshe, the Ewekoro Formation directly overlies
the Abeokuta Group. It is made up of grayish white and occasionally
greenish limestone which is sandy toward the base and having a thickness
that varies between 15-30m. This formation is dated Paleocene age.
Akinbo Formation on the other hand is mostly found in the western part of
the Imo Group, directly overlying the Ewekoro Formation. It consists of
thick grey highly fossiliferous shale, which is greenish in colour and
thickly laminated. The age of Akinbo Formation is considered to be
Paleocene.
2.1.5 Ilaro Formation
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The Ilaro Formation consists of fine to coarse grained sands, clays and
shales with occasional thin bands of phosphate beds. The formation is
Eocene in age.
2.1.6 Coastal Plain/Benin Sand Formation
The Coastal Plain Sand is believed to lie on top of the Ilaro Formation,
though there is no evidence to support this belief. The coastal plain sands
consist of very poorly sorted, clayey, pebbly sands, sandy clay and rare thin
lignite. The age of the Coastal plain sands ranges from Oligocene to
Pleistocene.
2.1.7 Recent Alluvium
This is the youngest unit in the Eastern Dahomey basin. It has been thought
to overlie the Ilaro Formation, though without a convincing evidence. Road
cut exposures between Ofada and Mokoliki around Ogun River show that
the sediments of this Formation are littoral/lagoon sediments which are
mostly clays and loose sands, with occasional pebbles.
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Fig 6 - OUTCROP GEOLOGY OF THE EASTERN DAHOMEY BASIN (OLANIYI ODEBODE)
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CHAPTER THREE
METHODOLOGY
Methodology deployed for study site: Epe lagoon (2°50′-4°10′N, 5°30′ -
5°40′E).
-Field Work
-Sample Preparation
-Preparation & Viewing Micro-Paleontological slides under Optical
Microscope
3.1 Field work
The study was carried out in the month of April 2015. Ten (10) sampling
points were established for this study along the Epe lagoon, each with its
longitude and latitude positions. Sample locations were taken using a
Global Positioning System (GPS).
Ten sediment samples were collected from the sample points in the lagoon
for micro-paleontological studies.
Sediment samples at each sample point were collected using a sample
grabber. The sediments were collected at the base of the lagoon at each
sample point with corresponding latitude and longitude. The sediments
were emptied into polyethylene bags and preserved with formalin. The
essence of formalin was to preserve the microfossils present in the
sediment.
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S/N Sample Points Co-ordinates Depth (m)
Ph Temp (Celcius)
PPM
Diss.Oxygen (mg/l)
(Ns) Sediment Colour/Texture
1
Location 21
Lat; 063322.2N
Lon; 0040057.8E
2
7.58
31.6
72
18.7
140
-
2
Location 8a
Lat; 063448.9N
Lon; 0035936.5E
6
7.0
32.0
-
-
-
Slightly
Brackish Water
3
Location 8b
Lat; 063433.9N
Lon; 0035930.1E
7
7.1
31.9
-
-
-
Brackish water
4 Location 9 Lat; 063442.3N
Lon; 0040018.8E
7
7.3
32.1
68
1.0
135
Brackish water
5 Location 10 Lat; 063413.7
Lon; 0040057.8E
3
7.4
32.0
69
16.4
137
-
6 Location 11 Lat; 063335.1N
Lon; 0040132.5E
4
7.55
32.1
72
30.1
144
Dark grey
Very Fine Silt
7 Location 12 Lat; 063334.6N
Lon;0040222.3E
2.2
7.57
32.1
72
-
143
Dark-Grey
Very Fine Mud
8 Location 19 Lat; 063249.6N
Lon; 0040208.7E
2.5
7.77
31.9
72
-
143
-
9 Location 20 Lat; 063259.0N
Lon; 004133.6E
2
7.6
31.6
72
14.9
141
Dark grey
Very Fine Silt
10 Location 23 Lat; 063412.5N
Lon; 0035959.2E
2
7.1
31.9
71
1.0
141
-
11 Location 24 Lat; 063423.3N
Lon; 035920.0E
2.5
7.48
31.8
68
17.0
131
-
Table 2 showing data collected from different sample points at the Epe Lagoon
3.2 Sample Preparation
Out of 20 samples collected, 10 samples were selected as representative
samples for micro-paleontological studies.
3.2.1 Autoclave water (Preparation of distilled water)
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Equipment: Autoclave Machine
Materials: Conical Flask, Foil Paper and Cotton Wool
1. Water was put into the conical flask and air-tight with cotton wool
and foils paper to prevent evaporation & contamination.
2. The conical flask was placed into the autoclave machine for
duration of 20minutes to reach a temperature of 125 degree Celsius
3. The water was brought out and allowed to cool; the end product
was pure, clean distilled water.
3.2.2 Dissolution of Sediments
Equipment: Weigh Balance
Materials: Conical Flask, Distilled Water, Palette and Cotton Wool
1. Exactly 2g of sediment (from each of the 11 different samples) is
chopped off using a scalpel and measured into 11 different conical
flasks; each labeled appropriately while using a weigh balance to
get the accurate measurement.
2. Distilled water is measured at varying ratios up to the top of the
conical flask to allow sediments dissolve properly.
3. This solution is left for 24hours to dissolve properly and settle.
4. After 24hours, the sediment is agitated to mix, and then allowed to
settle briefly then it was decanted into bottle containers and
labeled with their corresponding Locations.
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Fig 7 Image of Preparation and Dissolution of Samples
3.2.3 Acid Clean
Equipment: Hot Plate
Material: Conc. HNO3 (Nitric Acid), Distilled water, Conical Flask, Lab
Coat, Gas Masks, Hand Gloves.
1. The 10 different samples in bottle containers were poured into 10
different conical flasks each labeled appropriately; the samples fill
the conical flasks half-way.
2. Concentrated HNO3 was added to the sample solutions to fill
conical flasks up to a quarter-full
3. Hotplate was allowed to warm gently at moderate heat temperature,
and then the 11 different solutions were placed gently on the
hotplate to boil
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4. The technique was to allow the solution boil & evaporate to half of
its original measurement at a constant heat temperature in
approximately 4 Hours.
5. After 4hours of constant boiling and evaporation, distilled water
was added to fill up the evaporated portion and subsequently left
for 8hours.
6. after 8 Hours, the solution was decanted to allow rested sediments
remain in the conical flask and waste water was disposed safely
because of the hazardous nature of the solution and chemical used.
7. Distilled water was added again to fill up decanted portion, the
essence; to clean & wash the solution of impurities, this new
solution is left for another 8 hours.
3.3 Centrifuge of Samples
Equipment: Centrifuge Machine
Materials: Centrifuge Tube
1. The settled solution was poured into a centrifuge tube, total number
of centrifuge tubes were 10 as a result of 10 samples.
2. These tubes were placed inside the centrifuge Machine at a speed
of 50rounds for 10 Minutes
3. After completion of centrifuge rounds, the 11 samples were
brought out from machine and placed on a wooden holder.
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3.4 Preparation & Viewing Micro-Paleontological Slides under
Microscope
Equipment; Optical Microscope, Photo Micrograph
Material; Slides, Dropper, /Beaker, Hand Gloves, Distilled water
the standard smear slide preparation is the same as described by Bown and
Young (1998), the settling preparation follows Geisen et al. (1999). The
steps of the settling preparation method are summarized as follow:
1. The centrifuged samples were used to prepare slides to be viewed
under the optical microscope
2. A dropper was used to take tiny amounts of samples from the tube,
this tiny amount of samples were placed on the slides and enclosed
with a cover plate.
3. The dropper is washed thoroughly after use for a particular location
samples to avoid contamination of samples.
4. This process was used to create the slides and to continually view
under the optical microscope to determine the abundance and
presence of microfossils.
5. Viewing was done using microscope lense x 40.
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CHAPTER FOUR
4.1 RESULTS AND INTEPRETATION
The diatoms were of special interest in the entire microfossil content of the
Epe Lagoon. Thus, a total of 11 species of diatoms were identified in the
Epe lagoon, 8 centric diatoms and 4 pennate diatoms lettered A to K.
A – Aulacoseira
B – Amphora
C – Cyclotella striata
D – Coscinodiscus
E – Cocconeis placentula
F – Nitzschia
G – Conscinodiscus lineatus
H– Cymatopleura
I – Synedra
J– Fragilaria
K – Diploneis
4.2 IDENTIFICATION AND MORPHOLOGY
The number of species of diatoms is enormous; (Helmcke 1961) cites that
of some 100,000 species only some 10,000 may be recognized as valid.
32
A - Aulacoseira; It is a centric diatom; the frustules of Aulacoseira are
linked to one another by spines to form filaments. Cells are typically seen
in girdle view, because of the deep valve mantle. Cells often form colonies
and, depending on the species, may be joined by linking spines. The shape
of the linking and separation spines and relationship between spines and
striae are important characters that distinguish species within Aulacoseira
(Spaulding S et al 2008). Some of the species found in the Epe Lagoon are
Varida, Undulata, Granulata Var. Angustissima,
B – Amphora; It is a centric diatom; The Valves of amphora are
asymmetrical to the apical axis and symmetrical to transapical axis. On the
dorsal margin, the valve mantle is deeper than on ventral margin. As a
result, the frustule is wedge-shaped, similar to a section of an orange
(Spaulding, S. 2011).
C – Cyclotella Striata; It is a centric diatom; Cells are short and drum-
shaped and are rarely found in chains. The valve view is most commonly
seen. Valves are usually circular (sometimes elliptical) with a tangential or
concentric undulation of the valve face (rarely flat).
D – Conscinodiscus; This are very large centric diatoms, Cells are disc-
shaped, cylindrical or wedge-shaped, and solitary. Distinct rosette of large
areolae in the center of the valve, numerous chloroplasts.
33
E– Cocconeis Placentula; Valves are elliptic to linear-elliptic and
relatively flat. The raphe valve has a narrow axial area and a small circular
or oval central area.
F– Nitzschia; Nitzschia possesses an eccentric raphe, positioned in a canal
along one valve margin. The raphe systems within a frustule are positioned
on opposite, in the manner of line symmetry.
G – Conscinodiscus Lineatus; they are photosynthetic
H– Cymatopleura; Cells are linear, panduriform in valve view and
somewhat rectangular in girdle view. The valve surface is flat.
The raphe runs around the perimeter of the entire valve and is elevated by
a shallow keel (Hendey 1964).
I– Synedra; They are Centric, Cells approximately rectangular in girdle
view, typically long and thin attached by mucilage pads at the base to form
radiate colonies. There are two long plastids lying against the girdles and
overlapping slightly onto the valve face. In unhealthy material, these
plastids may split up, giving the appearance of many small discoid plastids.
J– Fragilaria; They are pennate; Valves are lanceolate, with an inflated
central margin. Valve apices are rounded to capitate. Spines are positioned
on the margin, a spine present at the end of a stria. Frustules are joined in
ribbon-like colonies (W. Smith 1980).
34
K– Diploneis; They are pennate; Frustules of Diploneis are typically
elliptical to panduriform, with bluntly rounded apices. Each valve
possesses two longitudinal canals, one on each side of the raphe. The canals
are positioned within the silica cell wall and open to the exterior through
pores, but lack openings to the interior of the cell.
4.2 PHOTOMICROGRAPH OF SAMPLES A-K
Plate 1; A – Aulacoseira
35
Plate 2; B - Amphora
Plate 3; C –Cyclotella Striata
36
Plate 4; C - Cyclotella and D- Conscinodiscus
Plate 5; E - Cocconeis placentula and C - Cyclotella Striata
37
Plate 6; F - Nitzschia
Plate 7; I-Synedra Acus
38
Plate 8; H- Cymatopleura
Plate 9; J - Fragilaria
39
4.3 PERCENTAGE COMPOSITION OF DIATOM SPECIES
Location 8
Diatoms Species Percentage composition (%)
Aulacoseira 44.1
Amphora 10
Cyclotella Striata 20
Conscinodiscus 15
Nitzsichia 9.6
Cocconeis Placentula 1
Cymatopleura -
Synedra -
Fragilaria -
Diploneis -
Table 3 for Location 8
Location 10
Diatoms Species Percentage composition (%)
Aulacoseira 50.4
Amphora 13.7
Cyclotella Striata 15.4
40
Conscinodiscus 4.2
Nitzsichia 16.3
Cocconeis Placentula -
Cymatopleura -
Synedra -
Fragilaria -
Diploneis -
Table 4 for Location 10
Location 24
Diatoms Species Percentage composition (%)
Aulacoseira 52.1
Amphora 3.2
Cyclotella Striata 20.1
Conscinodiscus 18
Nitzsichia 3.3
Cocconeis Placentula 2.3
Cymatopleura -
Synedra -
Fragilaria -
41
Diploneis 1
Table 5 for Location 24
Location 9
Diatoms Species Percentage composition (%)
Aulacoseira 41.4
Amphora 2.2
Cyclotella Striata 20.8
Conscinodiscus 14.5
Nitzsichia 1.6
Cocconeis Placentula 19.5
Cymatopleura -
Synedra 1
Fragilaria -
Diploneis -
Table 6 for location 9
Location 11
Diatoms Species Percentage composition (%)
Aulacoseira 40.2
Amphora 2.5
Cyclotella Striata 20.7
42
Conscinodiscus 13.2
Nitzsichia 4.9
Cocconeis Placentula 8.8
Cymatopleura -
Synedra 6.2
Fragilaria -
Diploneis 3.2
Table 7 for Location 11
Location 19
Diatoms Species Percentage composition (%)
Aulacoseira 80.2
Amphora 2.1
Cyclotella Striata 17.2
Conscinodiscus 0.5
Nitzsichia -
Cocconeis Placentula -
Cymatopleura -
Synedra -
Fragilaria -
43
Diploneis -
Table 8 for Location 19
Location 23
Diatoms Species Percentage composition (%)
Aulacoseira 42.1
Amphora 9.9
Cyclotella Striata 16.2
Conscinodiscus 7.1
Nitzsichia 4.1
Cocconeis Placentula 2.1
Cymatopleura 10.3
Synedra -
Fragilaria 8.2
Diploneis -
Table 9 for location 23 Location 21
Diatoms Species Percentage composition (%)
Aulacoseira 48.8
Amphora 5.9
Cyclotella Striata 26.2
44
Conscinodiscus 6.9
Nitzsichia -
Cocconeis Placentula 1.0
Cymatopleura 3.2
Synedra 5.1
Fragilaria 1.4
Diploneis 1.5
Table 10 for Location 21
Location 20
Diatoms Species Percentage composition (%)
Aulacoseira 40.5
Amphora 4.9
Cyclotella Striata 20.2
Conscinodiscus 9.9
Nitzsichia 8.1
Cocconeis Placentula 4.5
Cymatopleura 3.5
Synedra 2.9
Fragilaria 2.3
45
Diploneis 3.2
Table 11 for location 21
Location 12
Diatoms Species Percentage composition (%)
Aulacoseira 46.2
Amphora 4.1
Cyclotella Striata 24.2
Conscinodiscus 15.5
Nitzsichia 1.8
Cocconeis Placentula -
Cymatopleura -
Synedra 8.2
Fragilaria -
Diploneis -
Table 12 for Location 12
46
DISCUSSIONS
Diatom assemblages and individual species provided reliable indicators of
stream conditions throughout the Epe lagoon. A multi-dimensional
ordination showed that dissolved oxygen, alkalinity, temperature, depth
and substratum conditions were the most significant environmental
determinants influencing diatom community structure in the region. While
floater organisms may infer the climatic conditions, the benthic organisms
infer the depositional environment and substratum condition, whilst the
centric diatoms are found at the top of the stream sediments the pennate
diatoms are found at the depth of the stream sediment.
Thus, the most abundant specie of the centric diatom was the Aulacosiera
and Cyclotella while the most abundant specie of the pennate diatoms is
the Synedra and Cymatopleura.
The results show that the Aulacoseira and its many varieties constitute the
most dominant diatom throughout the Epe lagoon occurring in all Ten (10)
sample locations with very high abundance, this species are recognized as
good indicators of pollution as well as the amphora specie which was
scarcely found, these diatoms are referred to as pollution tolerant species
(S.A. Akinyemi 2007).
The high abundance of the aulocoseira brings to the fore the authenticity
of lagoon as a fresh water lagoon.
47
The second most abundant diatom is the cyclotella which were found at
varying depths ranging 2-2.5m indicates an organic-enriched lagoon
between Latitude 063423.3N and Longitude 035920.0E. The presence of
these diatoms suggests eutrophication (Mau, D.P., 2002)
Similarly, mid to high brackish water / marine forms included
Coscinodiscus, According to (Onyema 2006), the Synedra specie suggest
fresh water situation / low - moderate level nutrient levels/ moderate
organic pollution.
The pennate datoms; Fragilaria, Diploneis, Mesidictyopsis occurred in
assemblages together with centric diatom; Aulacoseira islandica at the
furthest part of the Epe lagoon study area which suggests that the different
species types exist in different parts of the deposits, which reflect temporal
and spatial variations in water depth, dissolved oxygen and salinity.
CONCLUSION
The existence of different species of diatoms in different parts of the study
area of the lagoon lead to the conclusion that the various diatoms specie
were tolerating the change in pH, salinity and dissolved oxygen of the
environment.
RECOMENDATION
48
I strongly recommend that the Micro-paleontological Study of Epe lagoon
should be carried out as often as possible; the micro-paleontological
content of the Epe lagoon is less known.
If this can be ensured, it will pave an easy way for subsequent research on
that field.
49
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