Lagos Lagoon provides a number of important ecosystem services that include fish supply for the indigenous fishing communities of Ilajes and Ijaws. The Lagoon is also a sink for pollutants from various point sources, including sawmilling activities at the Okobaba hub of the lagoon. The perception of stakeholders about the environmental risks of these anthropogenic activities is important considerations for sustainable management of this important coastal ecosystem. Organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) are priority pollutants that are associated with anthropogenic activities including the burning of wastes. The early life stages of fish species are useful bioindicators of pollutant effects for environmental risk assessments. This study investigated stakeholders’ environmental risks perception of the sawmilling activities on the Lagos Lagoon. Furthermore, physicochemical parameters and 16 priority PAHs were assessed in surface water, porewater, and sediment from the study area on the Lagos Lagoon. Further, the embryotoxic effects of crude and cleaned up sediment organics and porewater extracts on the African sharptooth catfish (Clarias gariepinus) embryos were evaluated. Most (70–93%) respondents observed fish declines, burn wastes on the bank of the lagoon and are aware of the environmental and human health risks of their activities. High molecular weight PAHs dominated the PAHs profile, especially in the sediment. Developmental abnormalities and decreased hatching success were observed in C. gariepinus embryos exposed to extracts from the test site compared to the controls though non-significant (P > 0.05). The results show the environmental risks of sawmill activities on the Lagos Lagoon. There is a need for targeted environmental management and stakeholders’ engagement to forestall further coastal degradation and promote sustainable fisheries in the lagoon in support of the UN sustainable development goal three (life below water).

1. © 2019, AEXTJ. All Rights Reserved 200
RESEARCH ARTICLE
Stakeholders’ Perception of Fish Decline in the Lagos Lagoon and Effects of
Sawmilling Activities on Water Quality and Clarias gariepinus Embryos
Taofeeq Adeyemi Adewuyi1
*, Temitope Olawunmi Sogbanmu1
, Oluwatoyin Fatunsin2
, Folake Echebiri2
,
Adebayo Akeem Otitoloju1,3
, Kehinde Olayinka2
1
Department of Zoology, Ecotoxicology and Conservation Unit, Faculty of Science, University of Lagos, Akoka
101017, Lagos, Nigeria, 2
Department of Chemistry, Faculty of Science, University of Lagos, Akoka 101017, Lagos,
Nigeria, 3
University of Lagos Consultancy Services, University of Lagos, Akoka Campus 101017, Yaba, Lagos, Nigeria
Received: 01-07-2019; Revised: 30-08-2019; Accepted: 10-10-2019
ABSTRACT
Lagos Lagoon provides a number of important ecosystem services that include fish supply for the indigenous
fishing communities of Ilajes and Ijaws. The Lagoon is also a sink for pollutants from various point sources,
including sawmilling activities at the Okobaba hub of the lagoon. The perception of stakeholders about the
environmental risks of these anthropogenic activities is important considerations for sustainable management
of this important coastal ecosystem. Organic pollutants such as polycyclic aromatic hydrocarbons (PAHs)
are priority pollutants that are associated with anthropogenic activities including the burning of wastes. The
early life stages of fish species are useful bioindicators of pollutant effects for environmental risk assessments.
This study investigated stakeholders’ environmental risks perception of the sawmilling activities on the
Lagos Lagoon. Furthermore, physicochemical parameters and 16 priority PAHs were assessed in surface
water, porewater, and sediment from the study area on the Lagos Lagoon. Further, the embryotoxic effects
of crude and cleaned up sediment organics and porewater extracts on the African sharptooth catfish (Clarias
gariepinus) embryos were evaluated. Most (70–93%) respondents observed fish declines, burn wastes on
the bank of the lagoon and are aware of the environmental and human health risks of their activities. High
molecularweightPAHsdominatedthePAHsprofile,especiallyinthesediment.Developmentalabnormalities
and decreased hatching success were observed in C. gariepinus embryos exposed to extracts from the test
site compared to the controls though non-significant (P 0.05). The results show the environmental risks
of sawmill activities on the Lagos Lagoon. There is a need for targeted environmental management and
stakeholders’ engagement to forestall further coastal degradation and promote sustainable fisheries in the
lagoon in support of the UN sustainable development goal three (life below water).
Key words: African sharptooth catfish embryos, environmental risks perception, Lagos Lagoon,
polycyclic aromatic hydrocarbons, sediment extracts, surface water, sustainable development goals, wood
processing activities
INTRODUCTION
The Lagos Lagoon is the largest brackish coastal
lagoon in the West African coast. It is major coastal
water in Nigeria that is of immense ecological and
economic value including being a major source of
seafood for people of Lagos.[1]
Human activities such
as oil transport, industrial wastewater discharges,
and urban runoff have adversely impacted the water
quality and biodiversity of the lagoon. These impacts
such as reduced fisheries diversity and fish catch over
the years have been reported by various authors.[2-5]
Address for correspondence:
Taofeeq Adeyemi Adewuyi
E-mail: taofeeq.adewuyi@students.unilag.edu.ng
Available Online at www.aextj.com
Agricultural Extension Journal 2019; 3(4):200-213
ISSN 2582-3302

2. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 201
The lagoon’s biodiversity is further threatened by
polluting activities such as sawmilling and burning
of wood shavings at the Okobaba (OB) bank of the
lagoon which is the hub of thriving logging and
sawmilling industry. The incessant burning of saw
dust and wood shavings near the lagoon [Figure 1] is
point sources of priority pollutants such as polycyclic
aromatic hydrocarbons (PAHs) into the lagoon which
are known to be carcinogenic and mutagenic.[11]
A study of PAHs in subsurface water of some
sampled areas of the Lagos Lagoon showed a
total PAH concentration range between 8.90 and
13.30 µg/l.[12-15]
In the sediments, values between
12.32 to 955.51 µg/kg (Alani et al., 2013) and
365.5 to 1431.9 µg/kg[16-19]
have been reported
with a predominance of four to six-ring (high
molecular weight) PAHs especially benzo(a)pyrene
and pyrene attributed to combustion/pyrogenic
sources. Embryotoxic (adverse effects on embryos/
early life stages of animals) and teratogenic (effects
on ontogeny/development of an animal) effects
of sediment organic extracts have been observed
in vivo, such as in zebrafish (Danio rerio) embryos
(Sogbanmu et al., 2016) and in vitro as in cell
lines (Perez-Albaladejo et al., 2016). Furthermore,
sediment porewater has been shown to induce toxic
responses including acute developmental toxicity
and cardiac teratogenesis in D. rerio (Fang et al.,
2014). The effects of pollutants on the early life
stages of fish provides a forecast on the availability
and sustainability of fisheries in aquatic ecosystems
(Mumuni and Sogbanmu 2018; Sogbanmu et al.,
2018).The clamor for animal alternatives in research
and rapid high-throughput assays to provide bases
for environmental management and policies has
informed the use of the early life stages of fish
species as a globally ratified method relating to the
principle of the 3 Rs. (replacement, refinement, and
reduction) (Organization for Economic Cooperation
and Development [OECD] 2013). Model fish
species indigenous to various countries have been
utilized such as the Zebrafish (D. rerio), fathead
minnow (Pimephales promelas), rainbow trout
(Oncorhynchus mykiss), and Japanese medaka
(Oryzias latipes).[6-10]
The African sharptooth
catfish (Clarias gariepinus), a commercially and
ecologically important fish species in Nigeria is
a suitable model with well-documented general
biology, transparent eggs, easy to culture, and
year-round reproduction (Nguyen and Janssen,
2001). The embryos can be spawned artificially and
development from fertilization to hatching occurs
within 24–29 h post-fertilization at 28–29°C.[20-29]
To sustainably manage coastal ecosystem resources,
particularly in the face of current global climate
change, there is a need to engage stakeholders in such
management programs. The stakeholders include
coastal aboriginal communities who consume an
average of 15 times more seafood per capita than non-
aboriginal people.[30]
However, the level of awareness
of stakeholders about the environmental and human
health risks of their direct or indirect potentially
polluting activities on coastal ecosystems is low
particularly in developing nations.[31]
There is limited
information on the OB community stakeholders’
awareness about the environmental and human
health risks of their activities on the lagoon. The
dearth of information on the impact of sediments on
native fish species, particularly their early life stages
and perception of pollution in the OB community
provided an impetus for this study. Consequently, the
study aim was to investigate the environmental risks
perception of stakeholders and the effects of sawmill
activities at the OB hub of the Lagos Lagoon on
embryos of C. gariepinus.This will aid understanding
of the nature and extent of biological impacts of the
associated pollutants on fish species for the purpose
of targeted environmental management.
MATERIALS AND METHODS
Study area
The study areas were OB (test site) and University
of Lagos high rise (HR) building area (reference/
Figure 1: Okobaba area near the Lagos Lagoon, Nigeria
showing the nature of anthropogenic activity

3. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 202
control site) on the Lagos Lagoon [Figure 2].
OB is located adjacent to zones with sawmills,
timber transport, and municipal waste discharge
while the reference site is located adjacent to the
University of Lagos staff quarters. Three stations
were sampled at each of the two study sites. The
stations were geo-referenced with the aid of global
positioning system and recorded as coordinates
of the locations [Figure 2]. Photographs of the
anthropogenic activities around the test site are
shown in Figures 1 and 3.
Questionnaire administration
Structured questionnaires were administered to
stakeholders (Sawmillers, fishermen, traders, and
residents) at the test site (OB) centered around their
perception of the environmental risks and potential
impacts of their activities on the Lagos Lagoon
(Awodele et al., 2014). A pilot study was conducted
at OB before the main fieldwork in which a total of
ten sawmillers and ten community dwellers were
interviewed as respondents. The purpose of the pilot
studywastodeterminethereliabilityofthequestions,
difficulty level, whether the questions were free
from ambiguity and whether it had the power to
discriminate over results. For the administration
of the structured questionnaires, the total sample
population that was selected randomly for the
study was 100, made up of 40 sawmillers and 60
community dwellers at OB and its environs (Olawuni
and Okunola, 2014). The target populations among
the community dwellers were fishermen, traders,
young adults, and the residents of the saw mills
vicinity near the lagoon. The information obtained
from the various respondents includes; demographic
characteristics of the community, source and
preservation of wood logs, means of livelihood, and
waste management practices around the lagoon.
Surface water and sediment samples collection
from the Lagos Lagoon
Surface water and sediment samples were collected
in the wet (June 2016–August 2016) and dry
(December 2016–January 2017) seasons. The water
samples were collected with the aid of amber-
colored glass bottles, while sediment samples were
collected with Van Veen Grab into foil papers from
three sampling points each at the test and reference
sites on the Lagos Lagoon.All samples were labeled
and stored in ice-packed (temperature: 4°C) coolers
before transportation to the Analytical Laboratory at
the Department of Chemistry, University of Lagos,
Nigeria for analysis. The samples from the three
sampling points at each site were composite before
analyses (Sogbanmu et al., 2016).
Surface water and sediment physicochemical
analysis
Surface water physicochemical parameters
(temperature, pH, conductivity, dissolved oxygen
[DO], total dissolved solids [TDS], and salinity)
Figure 2: Map of the study area showing sampling locations
on the Lagos Lagoon, Nigeria
Figures 3: (a-d) Pictures of (a) saw dust on the water,
(b) sawmilling sheds, (c) wood logs and solid wastes on
water surface, (d) burning of saw dust and thick mass of
tree logs on the lagoon and human activity of the water
surface around the Okobaba study area of the Lagos
Lagoon. (a and b) Adewuyi, T. A. – June 2016–August
2016 (wet season) sampling pictures; (c and d) Sogbanmu,
T. O. – February 2017 (dry season) sampling pictures
dc
ba

4. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 203
were measured in situ using Horiba U50G
multi-water sampler.
For the sediments, physicochemical parameters
such as total organic carbon (TOC), particle size,
pH, conductivity, and physical appearance were
analyzed. The particle size distribution of the
sediments was determined by a wet sieving and
sedimentation technique according to the British
Standard Method for Soils.[33]
Sediment pH was
determined after adding 0.01 mol/l CaCl2
(10 ml)
to 5 g of each sediment and shaken for 1 h.
Walkley-Black titrimetric method was used to
determine TOC and total organic matter. Oil and
grease were extracted ultrasonically (acetone:
n-hexane, 50:50v/v) and quantified gravimetrically
(Hong et al., 2003). The concentration of an
analyte in blanks was subtracted from field
samples.
Samples extraction and analysis of PAHs
Samples extraction
For water samples extraction, 250 ml of water
samples were liquid-liquid extracted using hexane
and dichloromethane (DCM) mixture (1:1 v/v),
according to Kafildazeh et al. (2011). Water samples
were extracted thrice using 50, 30, and 20 ml of the
solvent mixture. The solvents were combined, dried
with anhydrous sodium sulfate, and concentrated
using nitrogen gas. The extract was reconstituted
with 2 ml of n-hexane and DCM (1:1) and analyzed
for PAHs using Gas Chromatograph (GC) (Agilent
Technologies 6890N, GC system) coupled with
Flame Ionization Detector (GC–FID).
Sediment porewater samples extraction was
conducted according to Fang et al. (2014). Briefly,
5 g of sediment samples were centrifuged in glass
centrifuge tubes at 3000 rpm for 30 min to separate
the porewater from the sediment. The porewater
was collected, filtered into glass vials (this served
as the crude porewater), extracted and analyzed in a
similar manner to the water sample. Briefly, 5 ml of
porewater was liquid-liquid extracted as the water
samples using 5, 2, and 1 ml of extracting solvent.
The extract was reconstituted using 1 mL of hexane/
DCM (1:1) and kept in amber vials for analysis of
PAHs using GC–FID.
For sediment organics extraction, 5 g of sediment
samples were freeze-dried and 2 g of treated
copper turnings (copper turnings were treated
by adding 0.1 M concentrated nitric acid until
the outer layers were corroded after which the
copper turnings were washed thoroughly with
distilled water and kept in methanol for the use
to prevent sulfur interference) were added to the
sample and left overnight for 24 h (Sojinu et al.,
2013). Thereafter, the sediment samples were
ultrasonicated thrice using 10 ml, 6 ml, and 3 ml
hexane/acetone (1:1v/v) mixture for 30 min,
respectively. The extracts were combined and
concentrated using nitrogen. The extracts were
reconstituted with 5 ml of hexane. Sample cleanup
was done using Supelco solid phase extraction
C18 cartridges that have been conditioned with
methanol. The elution of the PAHs was done using
2 ml of hexane/DCM (1:1 v/v). The eluate was
analyzed using GC-FID.
Quality control and calibration
Reagent blank was carried out for the water sample
using distilled water extracted with hexane/DCM
solvent used for the liquid-liquid extraction. For
the sediment sample, a certified reference material
(clay loam two soil certified reference material
[CRM] 131 by Sigma-Aldrich) was used. The CRM
was ultrasonicated and extracted for PAHs like the
sediment samples. Spiked recovery method was
used for validation studies of the sediment samples.
The samples were spiked with 1 µl of 100 ppm
standard mixture containing the 16 priority PAHs
(naphthalene, acenaphthylene, acenaphthene,
fluorene, phenanthrene, anthracene, fluoranthene,
pyrene, benzo(a)anthracene, chrysene, benzo(b)
fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene,
indeno(1,2,3-cd)pyrene, dibenzo(a,h)anthracene,
and benzo(g,h,i)perylene) before extraction. The
spiked samples were extracted and analyzed.
The recoveries were between 75% and 105% for
both the spiked and certified reference standard, and
certified levels were obtained for PAHs in the CRM.
A mixed standard of the 16 priority PAHs was used
forexternalcalibrationoftheinstrument.Calibration
standards were prepared by serial dilution of stock
solution with DCM. A calibration curve was plotted
for each of the PAHs. All the calibration plots for
the16 PAHs had R2
=0.98–0.99 and were used to
quantify the PAHs.

5. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 204
Instrumental and analytical conditions
The concentrations of the PAHs were determined
using a GC-FID. Nitrogen gas was used as the
carrier gas with a flow rate of 40 ml/min, hydrogen
with air produced the flame. Temperature for sample
injection was 250°C and the volume of sample
injected manually was 10 µl in a split mode with a
split ratio of 100:1. The GC oven temperature was
programmed from 70°C to 175°C at 15°C min−1
then to 215°C at 10°C min−1
then to 265°C held for
0 min at 20°C min−1
to 290°C held for 8 min. The
run time was 42.25 min. The column was HP5 and
the length of the column was 30 m with an internal
diameter of 0.32 mm and thickness of 0.25 µm.
Sediment organics and porewater extraction for
embryotoxicity studies
Sediment organics extraction was conducted
as described in samples extraction above and
was solvent exchanged with acetone. The crude
sediment organic extract (CSE) stock solution was
equivalent to 1 g dry weight sediment equivalent
extract (eQsed) per milliliter while the cleaned up
sediment organic extract (CUSE) stock solution was
equivalent to 2.5 g dry weight sediment equivalent
extract (eQsed) per ml. Sediment porewater was
extracted (as described in samples extraction). The
crude sediment porewater (CPW) stock solution
was equivalent to 1 g wet weight sediment (eQsed)
per ml while the cleaned up sediment porewater
extract (CUPW) stock solution was equivalent to 5 g
wet weight sediment porewater equivalent extract
(eQsed) per ml. Acetone was used as a control.
Embryotoxicity studies with African sharptooth
catfish (C. gariepinus) embryos
Spawning of C. gariepinus embryos
C. gariepinus (chordata, osteichthyes, siluriformes,
andclariidae)embryoswerespawnedfromunexposed
broodstock (1 female and 2 males) purchased from
the University of Lagos fish farm according to
OECD (2013) and Sogbanmu et al. (2018). Briefly,
one female broodstock C. gariepinus (weight range:
1.1 kg; length range: 45 cm) was injected with
Ovaprim(SyndelLaboratoriesLtd.,Canada)hormone
at 0.5 ml/kg of fish.After 10 h latency period, a slight
pressure was applied on the abdomen of the female,
leading to a running out of the eggs which were
collected into a plastic bowl. Two males (weight
range: 1.0 ± 0.5 kg; length range: 48 ± 1.1 cm) were
euthanized and the testes were carefully removed
with the aid of a new razor blade. An incision was
carefullymadeoneachtestistoletoutthemiltusedfor
fertilizing the eggs. Fertilization was aided with the
addition of saline water to the mixture and the bowl
was gently swirled to ensure adequate mixing of the
milt with the eggs. Fertilized eggs were identified and
confirmed with the aid of a stereomicroscope (Ceti
Star – 13 ED Stereomicroscope, Medline Scientific,
United Kingdom). Fertilization was considered to
have occurred when the egg-yolk was transparent
greenish-orange and cell division was clearly visible
in the blastodisc (Oellermann, 1995; Mumuni and
Sogbanmu, 2018).
Experimental design for embryotoxicity studies
A total of 30 embryos (10 embryos in triplicates)
per concentration were exposed to sediment organic
extracts (crude and cleaned up) and porewater
(crude and cleaned up) in Petri dishes from 0 to 26 h
post-fertilization (hpf) in 40 ml of dechlorinated
water (Sogbanmu et al., 2016). The exposure
concentrations used were; 1 mg eQsed/ml (CPW),
250 µg eQsed/ml (CSE), and 1.25 mg eQsed/
ml (CUPW and 250 µg eQsed/ml (CUSEs). Two
controls were included; embryos in water alone and
embryos exposed to acetone 0.25 µl/ml (0.025% of
the highest concentration of sediment extract). The
endpoints that were assessed in the embryos were
mortality, hatching success, and developmental
abnormalities using a stereomicroscope (Ceti Star
– 13 ED Stereomicroscope, Medline Scientific,
United Kingdom). Mortality was measured as the
percentage of coagulated embryos with no structures
and/or embryos with no visible heartbeat (Kumar
et al., 2013). Hatching success was measured as
the percentage of embryos that hatched (fully
emerge from the chorion) at 26 hpf. Developmental
abnormalities were calculated as the percentage of
embryos observed under the dissecting microscope
with one or more developmental abnormalities
such as pericardial edema, yolk-sac edema, curved,
and/or stunted tail and scoliosis (Mumuni and
Sogbanmu, 2018).

6. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 205
Statistical analysis
The analysis of the responses data from the
questionnaire administration is presented in
frequency distribution tables with percentages
(Awodele et al., 2014). Physicochemical parameters
and PAH levels in surface water and sediments
as expressed as mean ± standard deviation. The
embryotoxicity (mortality, hatching success, and
developmental abnormalities) data are expressed
as mean ± standard error. One-way Analysis of
Variance was used to test for significant differences
between treatment means (physicochemical
parameters and embryotoxicity data) and controls.
t-test was used to test the significant differences in
PAHs data between sites and seasons. Post-hoc tests
were conducted using Duncan’s Multiple Range
Test (Duncan, 1955) with the level of significance
set at P 0.05. Statistical analyses were conducted
using SPSS version 22.0. Figures were prepared
using Microsoft Excel version 2010.
RESULTS
Demographic data of respondents at the OB
sawmills
The socio-demographics data revealed that male
respondents were higher in number for the two
groups of respondents (sawmillers and community
dwellers) [Figure 4]. Similarly, respondents in
the age range of 31–35 years were highest for the
two groups. Most respondents had other forms of
education (informal). The highest percentages of the
community dwellers reside in OB while the highest
percentage of the sawmillers reside in other areas.
The number of years of experience of the sawmillers
on the job was between 3 and 10 years while most
respondents in the community were students. The
demography of more than 75% of the respondents
in this study was adults (16 y and above), hence,
their responses are reliable [Figure 4].
Stakeholders’ perception about environmental
risks and wastes management at the OB
sawmills
The sole means of transportation of wood logs to
the sawmill was through the lagoon, as agreed by
all respondents [Table 1]. Solignum was identified
as the main insecticide used to treat wood logs and
most respondents agreed that over 10 logs were
processed in each factory weekly. Over 90% of
respondents agreed that saw dust and associated
wood wastes are dispersed by water into the lagoon
and continuous burning is employed to reduce the
piles of wood wastes. Some respondents attested
to health effects associated with smoke from the
wood wastes burning and these wastes adversely
impact the color of the lagoon water as strongly
agreed by most respondents [Table 1]. These wastes
were noted to cause a rise in the sediment level
in the lagoon. Most respondents strongly agreed
that they bath in the lagoon; the lagoon exudes a
foul smell and reduction in fish catch was noted
[Table 1]. As regard domestic wastes management,
most respondents recycle the waste materials, dump
solid wastes at the bank of the lagoon where they
are burnt and end up in the lagoon. Basic sanitation
and hygiene facilities such as public toilets were
not available around the study area; hence, most
respondents defecate directly into the lagoon
through wastewaters are not disposed into the
lagoon [Table 1].
Physicochemical characteristics of surface
water and sediments at test sites on the Lagos
Lagoon
The surface water physicochemical parameters at
both sites and seasons were within set limits by
National Environmental Standards and Regulations
Enforcement Agency (NESREA) except for DO
values in the dry season at OB which was lower than
Figure 4: Demographic data of sawmillers and community
dwellers at okobaba

7. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 206
the set limit and TDS values at both sites in the dry
season [Table 2]. Further, there were no significant
differences (P 0.05) in the physicochemical
parameters values between the control and test sites
in either of the seasons. However, conductivity,
TDS, and salinity values were higher in the dry
season compared to the wet season at both sites
[Table 2].
The percentage TOC in the sediment was higher
at the test site compared to the control site in both
seasons. Further, the % TOC was higher in the
wet season compared to the dry season at both
sites [Table 3]. The sediment pH was generally
acidic across the two sites and seasons, though,
the acidity was higher in the wet season compared
to the dry season. Conductivity was higher at the
test site in the wet season compared to the dry
season, while the reverse was the case for the
control site [Table 3]. The percentage sand and
silt particles size were higher in the wet season
at both sites compared to the dry season, though,
percentage clay particle size was higher in the
dry season compared to the wet season at OB
[Table 3].
PAHs concentration in surface water, sediments
and porewater of the Lagos Lagoon
The highest total PAHs in this study were recorded in
the sediments from the control site in the wet season
which was significantly higher (P 0.05) than
values recorded for sediments from OB [Table 4].
Table 1: Stakeholders’ perception about environmental risks and wastes management at the okobaba sawmills
Category Specific questions SA
Freq. (%)
A
Freq. (%)
D
Freq. (%)
SD
Freq. (%)
Transport and preservation
of wood logs
Logs are transported through the lagoon 124 (82.1) 27 (17.9) 0 (0) 0 (0)
Treatment of logs with aldrin 0 (0) 0 (0) 16 (33.3) 32 (66.7)
Treatment of logs with chlo dane 0 (0) 0 (0) 80 (100) 0 (0)
Main insecticide used to treat logs is solignum 140 (90.3) 15 (9.7) 0 (0) 0 (0)
More than 10 logs are processed weekly by each factory 72 (56.7) 33 (26) 22 (17.3) 0 (0)
Wood logs processing is done in each factory daily 72 (55) 45 (34.4) 14 (10.7) 0 (0)
Storage and management of
saw dusts
Dispersal of stored saw dust and other wood wastes by water
into the lagoon
100 (72.5) 30 (21.7) 8 (5.8) 0 (0)
Continuous burning of saw dusts and other wood wastes to
reduce their piles
112 (75.7) 36 (24.3) 0 (0) 0 (0)
Health effects from charred saw dust smoke to stakeholders 28 (23.9) 69 (59) 20 (17.1) 0 (0)
Sawmills wastes adversely impacts the color of the lagoon
water
128 (87.1) 12 (8.2) 6 (4.1) 1 (0.7)
Sawmills wastes cause a rise in the lagoon sediment level 120 (81.6) 24 (16.3) 2 (1.4) 1 (0.7)
Saw dusts are transported through the lagoon from adjacent
communities
80 (66.1) 18 (14.9) 18 (14.9) 5 (4.1)
Anthropogenic activities
near or in the Lagoon
Community dwellers bath in the lagoon 132 (68) 36 (18.6) 22 (11.3) 4 (2.1)
The lagoon water exudes foul smell 132 (64.1) 66 (32) 6 (2.9) 2 (1)
Fish sellers around the lagoon smoke fish at their stands 16 (10.5) 93 (61.2) 36 (23.7) 7 (4.6)
There is drastic reduction in the number of fishes in the lagoon 184 (86) 9 (4.2) 20 (9.3) 1 (0.5)
Wastes management Community dwellers dump domestic solid wastes at the bank
of the lagoon
168 (76.7) 45 (20.5) 6 (2.7) 0 (0)
Solid wastes are segregated before dumping at the bank of the
lagoon
0 (0) 15 (12.4) 102 (84.3) 4 (3.3)
Wastes end up in the lagoon 104 (62.3) 48 (28.7) 14 (8.4) 1 (0.6)
Wastes are dumped and burnt at the shore of the lagoon 204 (92.7) 6 (2.7) 6 (2.7) 4 (1.8)
Public toilets are available in and around the lagoon
waterfront
0 (0) 6 (5.6) 88 (81.5) 14 (13)
Community dwellers defecate directly in the lagoon 168 (85.35) 12 (6.1) 6 (3) 11 (5.6)
Wastewaters are disposed into the lagoon 4 (3.2) 15 (12) 104 (83.2) 2 (1.6)
Wastewaters are pre-treated before disposal into the lagoon 0 (0) 0 (0) 74 (76.3) 23 (23.7)
SA: Strongly agree, A: Agree, D: Disagree, SD: Strongly disagree, Freq.: Frequency of responses, %: Percentage of responses

8. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 207
Total PAHs in OB porewater and surface water were
higher than the values for the control site. In the dry
season, the total PAHs in the sediment at the control
site were higher than the values recorded for OB
[Table 4]. However, this value was significantly
lower (P 0.05) than the value recorded at the
control site in the wet season.
Furthermore, the total PAHs in the OB porewater
was significantly lower (P 0.05) in the dry
season compared to the wet season. There were no
significant differences (P 0.05) in the total PAHs
between the test and control sites in the dry season.
In general, in the wet and dry seasons, the order of
decreasing total PAHs was sediment porewater
surface water.
Embryotoxicity studies of Lagos Lagoon sediment
organics extracts and porewater on C. gariepinus
Mortality was highest in the cleaned up porewater
from the control site (HR) (CUPW-HR) followed
by the CPW-HR, CPW-OB, crude sediment organic
extract-OB (CSE-OB) compared to the controls as
well as CUPW-OB and sediment organic extracts
(CUSE-OB) from OB [Figure 5].
Hatching success was highest in the controls, CUSEs
(CUSE-OB) and porewater (CUPW-OB) from OB.
Hatching success was lowest though higher than
50% in cleaned up porewater from the control site
(CUPW-HR) [Figure 5].
The percentage abnormalities were highest in
the CUPW from the control site (HR) and lowest
water control. There were no significant differences
(P 0.05) in the mortality, hatching success and
abnormalities observed in the crude and CUSEs,
porewater, and controls [Figure 5].
DISCUSSION
In this study, we evaluated stakeholders’
environmentalrisksperceptionandeffectsofsawmill
activities on embryos of the African Sharptooth
catfish. The socio-demographic characteristics
of respondents in this study showed that the high
level of informal education (or low level of formal
education) might be a reason for the paucity of
Table 2: Physicochemical parameters of Lagos Lagoon surface water in the wet and dry season, 2016–2017
Parameter Wet season Dry season NESREA
Okobaba High rise Okobaba High rise Limits
Temperature (°C) 26.12±1.17 26.69±1.06 28.29±0.40 29.25±0.16 40
pH 8.16±0.57 9.35±1.57 6.75±0.06 6.67±0.15 6.5-8.5
Conductivity (mS/cm) 0.97±0.18 1.22±0.29 28.83±1.68 30.83±0.06 NS
Dissolved oxygen (mg/l) 9.68±5.18 8.85±3.39 4.34±0.74 9.72±3.96 6.0
Total dissolved solids (g/l) 0.65±0.06 0.76±0.20 17.90±1.04 18.83±0.06 2
Salinity (%) 0.44±0.10 0.61±0.14 17.40±1.01 19.13±0.06 NS
Values are Mean±SD (n=3); NESREA, 2010; NS: Not specified, NESREA: National Environmental Standards and Regulations Enforcement Agency
Table 3: Physicochemical parameters of Lagos Lagoon sediments in the wet and dry season, 2016–2017
Parameters Wet season Dry season
Okobaba High rise Okobaba High rise
TOC (%) 2.32±1.30 0.88±0.44 1.64±1.30 0.58±0.63
Grain particular size (%) Gravel; 0 Gravel: 0 Gravel: 0 Gravel:0
Sand: 15–22 Sand: 23-25 Sand:7.1-10 Sand: 21–23
Silt: 28–31 Silt: 35-37 Silt: 27-30 Silt:33–35
Clay: 50–54 Clay: 42-45 Clay: 63-67 Clay: 40–42
pH 4.13±0.50 4.86±0.92 5.92±0.50 5.25±1.00
Conductivity (dS/cm3
) 4927±2546 2522±1379 772±254 9473±139
Physical appearance Dark grey Dark grey Dark grey Dark grey
organic silty organic silty organic silty Organic silty
clay clay Clay Clay
TOC: Total organic carbon; n=3, Values are Mean±SD

9. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 208
Table4:PAHsconcentrationinsurfacewater,sediments,andporewateroftheLagosLagooninthewetanddryseasons,2016–2017
PAHs
(mg/l/mg/kg)
surface
Water
OkobabaWetseasonHighrise(control)Surface
water
OkobabaDryseasonHighrise(control)
SedimentSurface
Water
Pore
water
Pore
water
SedimentPore
water
SedimentSurface
water
Pore
water
Sediment
Naphthalene0.03±0.030.75±0.931.37±1.650.03±0.030.75±0.931.66±2.150.01±0.000.21±0.000.81±0.550.01±0.010.21±0.000.22±0.29
Acenaphthylene0.03±0.010.67±0.281.27±0.460.03±0.030.63±0.221.48±0.800.02±0.000.50±0.001.05±0.070.01±0.010.50±0.000.55±0.65
Acenaphthene0.29±0.470.78±0.481.47±0.800.15±0.230.73±0.404.38±7.750.02±0.000.50±0.001.01±0.010.01±0.010.50±0.001.01±0.00
Fluorene0.03±0.010.53±0.060.95±0.630.02±0.010.49±0.001.69±1.200.02±0.000.49±0.000.99±0.000.01±0.010.50±0.000.59±0.58
Phenanthrene0.16±0.210.45±0.120.88±0.280.02±0.000.45±0.122.06±0.890.05±0.040.52±0.011.04±0.010.01±0.010.52±0.001.33±0.41
Anthracene0.13±0.112.23±2.964.43±5.950.09±0.112.23±2.965.53±5.320.02±0.000.56±0.001.13±0.000.01±0.010.57±0.000.77±0.51
Fluoranthene2.11±1.610.65±0.091.26±0.100.03±0.010.65±0.091.35±0.240.10±0.110.60±0.001.20±0.000.13±0.010.60±0.001.51±0.44
Pyrene0.09±0.122.16±2.984.30±5.980.09±0.132.16±2.984.41±5.880.02±0.000.56±0.001.13±0.010.02±0.010.56±0.001.59±0.66
Benz(a)0.06±0.040.78±0.371.54±0.590.03±0.020.71±0.274.57±6.000.02±0.000.56±0.011.11±0.000.01±0.010.35±0.301.11±0.00
Anthracene
Chrysene0.17±0.260.36±0.280.75±0.500.02±0.010.36±0.280.81±0.390.02±0.000.52±0.011.035±0.010.01±0.010.42±0.151.04±0.00
Benzo(b)0.37±0.531.05±0.781.99±1.320.04±0.041.03±0.767.06±9.990.02±0.000.60±0.011.19±0.000.02±0.020.40±0.281.20±0.00
Fluoranthene
Benzo(k)
fluoranthene
0.06±0.030.68±0.581.36±1.170.03±0.020.68±0.582.72±1.170.04±0.001.02±0.002.04±0.000.03±0.031.02±0.002.05±0.00
Ene
Benzo(a)pyrene0.03±00.78±0.011.51±0.080.03±00.78±0.011.63±0.110.03±0.000.78±0.001.55±0.000.02±0.020.46±0.441.55±0.00
Indeno
(1,2,3,c-d)
0.03±0.010.54±0.061.03±0.060.02±0.010.53±0.074.82±6.290.02±0.000.52±0.021.03±0.050.01±0.010.68±0.001.53±0.00
Pyrene
Dibenz(a,h)
anthra
0.03±0.020.71±0.181.23±0.300.03±0.010.65±0.202.30±1.260.03±0.010.53±0.001.06±0.000.01±0.010.68±0.001.53±0.00
Cene
Benzo(g,h,i)0.56±0.870.54±0.420.97±0.750.39±0.650.52±0.438.00±8.560.02±0.000.27±0.000.59±0.060.02±0.010.74±0.000.63±0.00
Perylene
∑PAHs4.18±4.3313.66±10.58*26.31±20.1a
1.05±1.0013.35±9.4554.57±50.00b*
0.46±0.118.74±0.06**17.38±0.770.46±0.208.74±1.1717.97±3.54**
n=3,unitsforsurfacewaterandporewaterareinmg/lwhilesedimentsareinmg/kg,resultsarepresentedasmean±SD,*representssignificantdifferencebetweenseasonsforthesamemediawhiledifferentalphabetsuperscriptsrepresent
significantdifferencestestandcontrolsiteforthesamemediaandseasonatP0.05,PAHs:Polycyclicaromatichydrocarbons,a
ThisdenotedthatthesedimentfromOkobaba(testsite)islesssignificantwhencomparedtosedimentfrom
Highrise(controlsite)duringwetseason,b
*ThisdenotedthatsedimentfromHighriseishighlysignificantwhencomparedtosedimentfromOkobabaduringthewetseason.Also,sedimentfromHighriseduringthewetseasonishighly
significantwhencomparedtosedimentfromHighriseduringthedryseason,**ThisdenotedthatporewaterfromOkobabaduringthedryseasonislesssignificantwhencomparedtoporewaterfromOkobabaduringthewetseason.Also,
sedimentfromHighriseduringthedryseasonislesssignificantwhencomparedtosedimentfromHighriseduringthewetseason.

10. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 209
environmental responsibility and awareness of the
risks posed by the stakeholders’ activities. This has
been observed to be typical in rural areas and slums
in developing countries (Shen et al., 2013).
Furthermore, it was noted that most sawmillers
who are responsible for the major wastes generated
and disposed at the site do not reside in the
area. This might be responsible for the possible
indifference/ignorance to the environmental
and human health risks of their activities. The
stakeholders’ perception of environmental risks
revealed the nature of sawmill materials (wood
logs) transportation which is mainly through the
lagoon. This corroborates the observation by
some authors (Buraimoh et al., 2015; Elijah and
Elegbede, 2015) who reported similar results
in the study area. Furthermore, the number of
wood logs processed weekly combined with the
preponderance of sawmill factories at the site
reveals the reason for saw dusts being the major
waste generated. According to Abulude (2006),
about 104,000 cm3
of sawdusts is amassed daily
at these sawmills.
The use of solignum (active ingredient: Permethrin)
as the main insecticide for treating wood logs is
due to its efficacy in preserving and protecting
the wood from infestation by wood borers and
termites (Patrick-Iwuanyanwu et al., 2016) which
could reduce the marketability and/or quality of the
wood (Olajuyigbe and Oloyede, 2017). Solignum,
like other wood preservative chemicals such as
Timber guard and D-D Force, is sold in the open
market making them easily accessible to users like
sawmillers (Olajuyigbe and Oloyede, 2017).
The means of disposal of saw dusts which was
noted to be mainly by dumping and burning on the
bank of the lagoon may be due to the lack of land
area to store the massive quantities and poor/almost
inaccessible roads for wastes managers to collect
the wastes frequently. This agrees with Buraimoh
et al. (2015) who reported burning and dumping of
sawdusts into the lagoon as a means of disposal. The
poor esthetic value of the lagoon in terms of color as
strongly agreed by most respondents is corroborated
by Buraimoh et al. (2015) who attributed the loss
of esthetic value to the foul odor oozing from the
anaerobic decomposition of the saw dusts. Further,
health effects associated with the burning of the
sawmill wastes were noted by most respondents.
Pollutants such as carbon monoxide, sulfur dioxide,
nitrogen oxides, and particulate matter have been
associated with wood burning with attendant effects
on breathing and risks of lower respiratory infections
(Owoyemi et al., 2016). The lack of public toilets in
and around this urban slum (OB) as alluded to by
most respondents could be a reason for bathing and
defecating by stakeholders especially community
dwellers in the lagoon. These unsanitary acts may
cause skin infections (dermatitis), cholera due to
unintentional ingestion of the lagoon water and
other public health disease outbreaks associated
with a lack of sanitary facilities especially in
vulnerable persons (the elderly and children) (Boadi
and Kuitunen, 2002). The decline in fish catch in the
lagoonasnotedbymostrespondentsmightberelated
to the polluting activities at the test site as attributed
to in Buraimoh et al. (2015) and Owoyemi et al.
(2016). This creates anoxic conditions resulting in
the death or exodus of aquatic organisms. Recycling
options for these wastes such as use as poultry
animal bedding, garden mulch, and particle board
(Owoyemi et al., 2016), among others should be
considered as an environmental friendly and more
sustainable disposal method.
ThesurfacewaterDOvaluerecordedatOBinthedry
season which was lower than the NESREAlimit may
be attributed to preponderance of organic pollutants
(sawdusts) could result in anoxic conditions due
to the action of microorganisms (Buraimoh et al.,
Figure 5: Embryotoxicity indices in Clarias gariepinus
embryos exposed to extracts of sediments from test and
reference sites on the Lagos Lagoon from 0 to 26 h post-
fertilization. n=3 replicates, values are represented as %
mean ± standard error. Exposure concentrations: 1 mg eQsed/
ml (CPW), 250 µg eQsed/ml (CSE), 1.25 mg eQsed/ml
(CUPW), 250 µg eQsed/ml (CUSE), 0.25 µl/ml (acetone)

11. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 210
2015). Furthermore, the low DO may be related to
the high TDS value in the dry season at the test site
though a higher value was recorded at the control
site. In dry season, the water is more concentrated,
slightly acidic, had more dissolved solids and ions
which gave rise to higher conductivity and salinity.
The temperature of the lagoon was higher in the dry
season which is usually hotter.The lack of significant
differences in surface water physicochemical
parameters between the test and control site is rather
puzzling. The control/reference site was selected on
the basis of a lack of visible anthropogenic activity
except for its proximity to the University of Lagos
staff quarters. This may point to the very high
pollution status of the lagoon over the years. Since
water is not stagnant, its move across the lagoon
could transport pollutants from highly polluted
sections to hitherto unpolluted/lowly polluted areas.
The higher TOC values recorded in sediments at the
test site compared to the control may be because
of the continuous deposition of wood wastes at the
site which is majorly composed of carbon. Over
the years, this contributes to siltation of sediment
at the site as evidence by the high percentage of silt
and clay particle size in this study. Furthermore, the
characteristic color of the sediments is associated
with sediments that have organic matter present in
them. The high percentage TOC observed in the wet
season may be due to a higher deposition of wood
wastes into the surface water through run-off during
the heavy rains which eventually sink to the bottom
of the lagoon. Microorganisms act on this in the
sediment further compacting it (Buraimoh et al.,
2015). This might be responsible for the lower
sediment pH observed in the wet season compared
to the dry season. Sediment pH was noted to be
more acidic than surface water pH. This could be as
a result of accumulation of organics at the bottom of
the lagoon. Furthermore, the sediment conductivity
values were higher than the water samples showing
that there were more ions in the sediments probably
due to accumulated debris. The higher percentage
of sand and silt observed in the wet season may be
due to run off during rainfall from the bank of the
lagoon laden with saw mill wastes.[33-40]
The higher level of PAHs (especially high molecular
weight [4–6 rings] PAHs) in the sediments compared
to the surface water and porewater is consistent with
the findings of Sogbanmu et al. (2016) who reported
higher levels of PAHs in the sediments compared to
the surface water. Furthermore, organic pollutants
such as organochlorine pesticides have been found
to be highest in sediments followed by porewater
and least in surface water (Gakuba et al., 2018).
Sediments have been shown to act as sinks for PAHs
due to the hydrophobic nature of the latter. PAHs
adhere to organic matter in soil and sediments (Wang
et al., 2014). Moreover, the nature of the sediment, in
this case, organic, silty, and clayey can contribute to
the binding of organic compounds such as PAHs to
it. The significant decrease of PAHs in the porewater
from the test site in the dry season might be due
to the reduced remobilization of sediment PAHs
into the water column. The Lagos Lagoon is a tidal
water and suffers from longshore drift. It receives
water from the Atlantic Ocean during high tides and
returns water during low tides. During this process,
there is mixing of water (Badejo et al., 2014). The
findings in this study were similar to the findings
of Ololade et al. (2011) and Adekunle et al. (2017)
where higher concentrations of PAHs were recorded
during the wet season than in the dry season. The
cleaned up porewater in this study elicited the
highest embryotoxic responses (lowest hatching
success, highest mortality, and developmental
abnormalities). This may be attributed to the high
concentrations of PAHs detected in porewater
compared to surface water. Although sediment
PAHs were higher than porewater PAHs in this
study, the higher embryotoxic responses observed
in the porewater compared to the sediment organics
extractsmaybeduetotheconcentrationofporewater
tested which was 4 times higher than the sediment
organic extracts. The assumption for the disparity
in extract concentrations of porewater and sediment
organics was that sediment organic extracts would
be more toxic than the porewater since PAHs and
other organic contaminants have been shown to be
higher in sediments than porewater.
As observed in the previous results on
physicochemical parameters and PAHs values for
the test and control sites, embryotoxic responses
were highest in the extracts from the control site
comparedtothetestsite.Furthermore,thecleanedup
porewater and sediment organic extracts (containing
PAHs only) elicited higher embryotoxic responses
compared to the crude porewater and sediment
organic extracts at the control sites. This points to

12. Adewuyi, et al.: Stakeholders’ perception of fish decline in the lagos lagoon
AEXTJ/Oct-Dec-2019/Vol 3/Issue 4 211
an unexpected source of pollution by PAHs which
are not related to significant anthropogenic activity
as seen at OB. Possible sources could be due to oil
spills from boats that cross the area, proximity to
the University of Lagos Lagoon front which is the
berthing point for boats used by some departments
in the university.
Conversely, the crude porewater (containing
inorganic pollutants) and sediment organic extracts
(containing organic pollutants including PAHs)
from OB (test site) elicited higher embryotoxic
responses compared to the cleaned up extracts
from the same site. This point to other pollutants
(both inorganic and organic) at the site which
are capable to eliciting higher embryotoxic and
perhaps more biotoxic effects than PAHs alone.
Potential inorganic pollutants that may be present
at OB though not evaluated in this study could be
heavy metals, surfactants, sulfates, nitrates, and
phosphates (Arimoro et al., 2007), among others.
Other organic pollutants that may be present which
are potentially toxic are pesticides particularly
Solignum (permethrin-based) which was noted by
most respondents in this study as the main wood
preservative and protectant (Patrick-Iwuanyanwu
et al., 2016), tannins, and lignins (Bailey et al.,
1999), among others.
The non-significant embryotoxic responses between
extracts and controls could be due to the low
concentrations tested (250 µg eQsed/ml) compared
to the concentrations (2.5–25 mg eQsed/ml) that
elicited significant embryotoxic effects in D. rerio
embryos exposed to Lagos Lagoon sediment organic
extracts (Sogbanmu et al., 2016).
CONCLUSIONS
Our results demonstrate the environmental and
potential human health risks posed by sawmill
activities at OB is mainly due to a lack of formal
education and the non-availability of efficient waste
management systems. In spite of the non-significant
differences observed in the embryotoxicity studies
with C. gariepinus embryos compared to the
control, the observed high mortality, low hatching
success, and high developmental abnormalities in
the extracts agrees with the observation of most
respondents regarding the decline in fish catch in
the lagoon. We recommend future studies such
as in situ monitoring studies using indigenous
fish and macro-invertebrates, evaluation of other
biomarkers in model aquatic organisms, evaluation
of other pollutants such as pesticides and heavy
metals in the sediment and water, species diversity
studies and stakeholders’ engagement for holistic
evaluation and management of pollution in the
study area. Furthermore, we recommend targeted
environmental management and stakeholders’
engagement to forestall further coastal degradation
and promote sustainable fisheries in the lagoon in
support of the UN sustainable development goal
three (life below water).
ACKNOWLEDGMENTS
This project was supported in part by funds from
the PADI Foundation to T.O Sogbanmu and a
research grant to T.A Adewuyi by the Society for
EnvironmentalToxicologyandPollutionMitigation.
DECLARATION OF INTEREST
The authors report that they have no conflicts of
interest.
ETHICAL APPROVAL
All applicable international, national, and/
or institutional guidelines for the care and use
ofanimals were followed. This study followed
the principles in the Declaration of Helsinki on
the humane treatment of animals used in research
(http://www.wma.net/en/30publications/10policies/
a18/) and the principles in the AVMA Guidelines for
the Euthanasia of Animals (AVMA, 2013).
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