OPEN ACCESS Research Journal of Environmental Toxicology
Metal Concentrations in the Helderberg Marine Protected Area,
False Bay, Cape Town
C. Sparks and B. Mullins
Department of Conservation and Marine Sciences, Cape Peninsula University of Technology, P.O. Box 652, 8000 Cape Town, South Africa
Background: The release of metals is increasing in industrial and urban areas and the impacts thereof are poorly understood. In an
attempt to protect areas from anthropogenic impacts, certain areas are declared protected. The assumption thus could be that protected
areas are free from the effects of pollutants. The Helderberg Marine Protected Area (HMPA) is situated in an urbanised region of False Bay,
Cape Town, South Africa. Although considered a protected area, the question is raised whether metals from the surrounding area are
affecting the coastal environment of the MPA. Materials and Methods: The study assessed the concentrations of 8 metals
(Al, Mn, As, Mo, Cd, Fe, Cu and Zn) in the water, sediment and mussel
. Samples were collected from within the
HMPA, at its border (Lourens river) and adjacent to the HMPA (Strand) in August, 2012. Results: The results showed that metal
concentrations were higher in the sediment than ambient coastal waters. Furthermore, metal concentrations were higher in mu ss el s
than the sediment for As, Mo, Cd, Cu and Fe. Conclusion: The most important result was that mussel Al, Mn, Cd, Cu and Fe concentrations
were similar in and adjacent to the HMPA. The results suggested that the environment of the HMPA was exposed to contaminants
(such as metals sampled in this study) from areas outside the MPA and management authorities should consider the effects of these and
other contaminants in management plans of MPAs.
, biomonitoring, metal contamination, marine protected area, sediment pollution, pollutant load index
Received: Accepted: Published:
Citation: C. Sparks and B. Mullins, 2016. Metal concentrations in the Helderberg marine protected area, False Bay, Cape Town. Res. J. Environ. Toxicol., CC:
Corresponding Author: C. Sparks, Department of Conservation and Marine Sciences, Cape Peninsula University of Technology, P.O. Box 652,
8000 Cape Town, South Africa
Copyright: © 2016 C. Sparks and B. Mullins. This is an open access article distributed under the terms of the creative commons attribution License, which
permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.
Competing Interest: The authors have declared that no competing interest exists.
Data Availability: All relevant data are within the paper and its supporting information files.
Res. J. Environ. Toxicol., 2016
Coastal environments are under considerable threat
due to the increased pressures of urbanization and
industrialization. In southern Africa, the marine environment
is considered to be relatively pristine in terms of global
standards1,2. However, taking into account the multiple use of
areas and increased population growth and development,
localised anthropogenic activities in coastal areas may be
increasing the habitat destruction and loss of vulnerable
ecosystems. To ameliorate these effects, coastal areas are
closed and declared marine protected areas. Although closed
to the general public, a key question is whether declaration of
protected areas are indeed protecting the ecosystems and
organisms that are intended to be protected.
The long term release of metals into the coastal and
aquatic environment may have negative impacts on the
physical and chemical composition of biota, productivity,
diversity and abundance3. Metals have different impacts on
the environment and species, depending on organismal and
system sensitivity to the metals4,5. Therefore, each study site
might be influenced differently by metal contamination,
based on the sites proximity to the sources of contamination
and its level of exposure6.
To ascertain the level of metal contamination in the
environment is a challenging task to undertake. Not only do
metals occur naturally in the environment and integral to
biochemical function, they can also occur in various forms
of ionic speciation, depending on a host of chemical and
physical factors7. Despite these challenges, biomonitoring
is used to asses and monitor the levels of contamination
in the environment that may be used as an indicator of
accumulation and bioconcentration5. The use of biota to
assess the quality of a habitat is based on the assumption that
some species are more tolerant to chemicals than others and
therefore can provide information on the types and level of
contamination in the environment4,8,9.
Biomonitoring studies are based on the assumptions
that organisms reflect the environmental conditions they live
in6,9. Mussels have the ability to accumulate metals directly
from the surrounding environment and absorb these into
the tissue at levels much higher than that of the existing
water and sediment10,11. T h e m us s e l,
species has been the preferred indicator species for most
biomonitoring programmes along coastal environments10-1 6.
Mussels are suitable biomonitor species as they provide
important information relating to the levels of heavy metal
contamination in the environment through the analysis of the
mussel soft tissue (or whole mussel)12. Analysing mussels to
indicate areas of elevated metal concentration in mussel soft
tissue, water and sediment17 can be useful in identifying and
describing the relationship between the concentrations in
mussels and the environment18,19.
Coastal and terrestrial based sources of pollution in
False Bay and surrounding areas of the bay are the major
contributors of contamination in the area20 with coastal
ecosystems under considerable stress caused by non-point
(maritime transportation) and point source contamination
(treated sewage effluent, agricultural, commercial and urban
development)21,22. Anthropogenic activities contribute largely
to the poor water quality and the loss of sensitive invertebrate
species along False Bay23-25.
Contamination discharged into river systems find their
way into estuaries and coastal zones, which may result in the
accumulation of contamination in the sediment and the
bioaccumulation of contaminants in living organisms26,27. A
high sensitivity to heavy metal bioaccumulation has been
observed in the development stages of bivalves and the
increase of metals concentrations at levels above the
threshold are often toxic to the organisms28,29. Heavy metal
contamination in areas of high anthropogenic activity is
increasing to levels much higher than the levels found in the
earth crust7. The Cd, Cu, Co, Zn, V and Mn occur naturally in
the environment and are important to plant and animal health
and the increase in non-essential metals released by
anthropogenic activity are polluting the environment at
The HMPA in False Bay, Cape Town (South Africa) was
proclaimed in 2000 as a strategy to rehabilitate, conserve and
protect a relatively small marine and coastal environment in
Cape Town27. The MPA consists of 4 km of sandy beaches on
the northern shore of False Bay and is situated between the
Eerste river and Lourens river mouth. There are three potential
land based pollution sources in and close to the HMPA,
namely the Macassar Waste Water Treatment Works (WWTW),
SOMCHEM national defence testing facility and the Lourens
River and catchment area (urban run-off)31. Little to no
information regarding the environmental history of HMPA and
the impacts of contaminants from pollution sources and these
are inhibiting effective management of the HMPA32,33.
are being used in Mussel Watch
Programmes (MWP) by Department of Environmental Affairs
(DEA)22 to assess the metal concentrations in False Bay.
However, metal contamination in the HMPA has never
been monitored33,34. Therefore, establishing a baseline of
the metal contamination in and outside the HMPA will assist
management authorities in developing a monitoring system
Res. J. Environ. Toxicol., 2016
to mitigate potential risk of toxic levels of contamination in
and outside the MPA. The objectives of the study were to
determine the level of metal concentration in the intertidal
water, sediment and mussels (
and outside the Helderberg Marine Protected Area.
MATERIALS AND METHODS
Study area: False Bay (34E0621.29S and 18E4631.27E) is
one of the largest true bays in South Africa31 (Fig. 1). The bay
formation is almost square with an approximate dimension of
about 35×30 km in length31. The False Bay coastline is largely
occupied by human settlement and commercial development
activities with numerous small storm water outlets that drain
into the bay22,35,36.
Three study sites along False Bay were chosen for the
study: the Helderberg Marine Protected Area (HMPA),
Lourens river mout h (Lou rens) situated at the Eastern
border of the HMPA and Strand situated in an urban coastal
area approximately 2 km from the HMPA (Fig. 1). The land
used at the three sites range from light industrial,
agricultural, commercial and residential developments,
waste water treatment works and solid waste dumpsites22.
Sampling: Specimens of the mussel
(n = 5) were collected at low tide from the three sites in
of similar sizes were
collected from the three sites at low tide when mussels beds
were exposed. On collection the mussels were stored in cooler
boxes at the site and transported to the laboratory mussels
where the mussels were depurated for 24 h, before being
stored in a freezer at -20EC until further analysis. The mussel
samples were treated by washing with deionized water, the
wet weight, length and width of each mussel sample was
measured before the mussels were dried in the oven for 48 h
Fig. 1: Study area and location of sampling sites at the Helderberg Marine Protected Area (HMPA), Lourens river and Strand
South Africa Stud
Protected Area (HMPA)
Res. J. Environ. Toxicol., 2016
Sediment and water samples (n = 5) were collected
simultaneously as the mussels at the three sites. Surface
sediment samples were taken at low tide in the intertidal zone,
using a pre-cleaned 500 mL plastic sample jar. Water samples
were collected at a depth of 30 cm above the sediment, using
a 500 mL pre-cleaned plastic sample jars. Water, temperature
and pH was measured using an Hanna portable meter.
Samples were transported to the laboratory where these were
stored at -20EC until further analysis.
Frozen sediment samples were defrosted, where after
they were oven dried for 48 h at 60EC in a Memmert drying
oven. Sediment was ground with a mortar and pestle and
subsamples (±0.2 g) used for metal analysis. Ground
sediment aliquots and defrosted water samples (5 mL water)
were digested using 10 mL of nitric acid (analar grade 60%
HNO3). Samples were then heated to 40EC in a grant UBD
heating block for one hour, thereafter to 120EC for 3 h. The
digestates were allowed to cool and then filtered through
Whatman No. 6 filter paper and then through 0.45 µm
membrane micro-filter (Millipore) paper using a syringe.
Samples were then placed in plastic centrifuge tubes
containing 5 mL digestate and 10 mL distilled water and
stored in a refrigerator until further analysis was done.
A blank accompanied all samples when analysis of
samples took place. The concentrations of the metals were
analysed with 5 replicates being done for each metal using
an Inductively Coupled Plasma-Mass Spectrophotometer
(ICP-MS), according to the methods of Mdzeke37 and the
concentrations of Al, Mn, As, Mo, Cd, Fe, Cu and Fe analysed.
Water concentrations of metals are presented as µg LG1 and
sediment and mussel tissue as µg LG1 dry weight. Analytical
standards (quality control standards) were used for all metals
to determine the analytical variation. All metal concentrations
were within 2% Relative Standard Deviation (RSD) of the
certified concentrations (except for Al which 9% RSD).
The level of metal contamination in sediment is
expressed in terms of a Contamination Factor (CF). An
equation previously used by Varol38 was used to calculate
the contamination factors for each heavy metal at each site39,
CF = Metal concentration in sediment/background levels for
marine sediment. The background concentrations for the
sediment were from concentrations recorded by Hennig40.
The extent of pollution at each site was evaluated using
methods based on Pollution Load Index (PLI). The pollution
load index is an equation that makes use of the contamination
PLI = (CFmetal 1×CFmetal 2×CFmetal 3…. ×CFnth metal)1/nth metal
Statistical analysis: Statistical analyses were performed using
SPSS 19.0 programme. Metal concentrations in water,
sediment and soft tissue of mussels were tested for normality
using the Levenes test and for variance using the Shapiro-
Wilke test. Variability of mean data was represented using the
Standard Error of the Mean (SEM). Statistical significance
differences were assumed at p<0.05.
RESULTS AND DISCUSSION
The coastal water temperatures ranged between 13.80
and 14.10EC with an overall mean of 13.91EC (SEM±0.12EC),
with no significant differences recorded between the three
sites. These measurements are similar to that previously
reported in the study area34. The pH rang ed be twee n 6.93
and 7.83 with pH decreasing from Helderberg Marine
Protected Area (HMPA) towards Strand. The mean pH at
Strand (6.93±0.09) was significantly lower than the HMPA
(7.83±0.03) and Lourens river (7.5±0.15), respectively
(p<0.05). These pH levels were similar to that measured by
.31 where the average water pH at Lourens river,
between 1990 and 1999, ranged between 7.4 and 7.7.
Metal concentrations in the water sampled from all three
sites were lower than sediment and mussels (Table 1). Of the
three sites, the highest concentrations of metals within the
water of the HMPA were reported for 50% of the metals
measured: Mn, As, Cu and Zn. The Zn concentrations were
3 times higher than the other two sites sampled with a
maximum of 15.31 :g LG1 recorded at HMPA. According to
Taljaard22 the waste water treatment and sewage out fall from
the urban-industrial areas that discharge directly into
False Bay, carry with it a wide range of chemical effluents and
pollutants that increase the heavy metal contamination in the
bay and may thus be potential sources of metal contamination
at the sites sampled.
According to Taljaard
.31 th e m ont hl y in fl ows fr om
the Lourens river estuary into False Bay increases between
May and October with an inflow peak reached between
June and August. The high flow rate from the Lourens river
into the bay suggests that there is a higher flushing and
distribution rate of metals into the bay during these periods of
the year. This could account for the relatively lower metals
concentrations measured and the Lourens river as sampling
took place during August.
Except for Cd, sediment metal concentrations increased
from HMPA towards Strand. Concentrations of Mn, As, Cd, Fe,
Cu and Zn were lower at the Lourens river than the HMPA
(Table 2). Significantly higher (p<0.05) Al, Mn and Fe
concentrations were recorded in the sediment than mussels
Res. J. Environ. Toxicol., 2016
Table 1: Metal concentrations (µg LG1, n = 5) in coastal water samples collected at the HMPA, Lourens river and Strand
Station Al Mn As Mo Cd Fe Cu Zn
Mean 0.20 0.07 0.03 0.09 <l.d <l.d 0.07 8.81
SEM 0.10 0.01 <l.d <l.d <l.d <l.d 0.01 3.42
Minimum 0.07 0.05 0.02 0.09 <l.d <l.d 0.04 3.75
Maximum 0.40 0.09 0.03 0.10 <l.d 0.01 0.08 15.31
Mean 1.45 0.04 0.02 0.09 <l.d 1.42 0.05 2.03
SEM 0.49 0.02 <l.d 0.01 <l.d 0.36 0.02 1.53
Minimum 0.68 0.01 0.01 0.08 <l.d 0.69 0.02 0.20
Maximum 2.37 0.08 0.02 0.10 <l.d 1.79 0.08 5.07
Mean 0.39 0.02 0.02 0.09 <l.d 0.11 0.01 2.45
SEM 0.06 0.01 0.01 0.00 <l.d 0.08 <l.d 0.88
Minimum 0.28 <l.d 0.01 0.09 <l.d <l.d <l.d 1.41
Maximum 0.46 0.05 0.03 0.10 0.01 0.28 0.02 4.19
<l.d: Below level of detection
Table 2: Metal concentrations (µg gG1 dry weight, n = 5) in coastal sediment samples collected at the Helderberg Marine Protected Area (HMPA), Lourens river and
Station Al Mn As Mo Cd Fe Cu Zn
Mean 256.12 6.93 1.07 0.03 0.09 723.29 0.53 4.58
SEM 12.50 0.39 0.10 <l.d 0.01 53.85 0.07 1.62
Minimum 239.35 6.25 0.93 0.03 0.08 664.20 0.45 2.70
Maximum 280.57 7.59 1.25 0.04 0.11 830.82 0.67 7.80
Mean 287.77 5.94 0.83 0.03 0.08 661.97 0.47 3.13
SEM 18.17 0.40 0.03 0.01 0.01 29.50 0.04 1.63
Minimum 257.67 5.14 0.80 0.02 0.06 623.93 0.43 1.13
Maximum 320.44 6.43 0.88 0.06 0.10 720.04 0.55 6.36
Mean 378.14 8.87 1.20 0.05 0.13 1054.55 0.75 7.84
SEM 15.87 0.22 0.05 <l.d 0.01 12.41 0.06 1.62
Minimum 348.34 8.64 1.11 0.04 0.10 1036.80 0.65 5.19
Maximum 402.51 9.32 1.27 0.05 0.15 1078.45 0.86 10.78
<l.d: Below level of detection
at all the sites sampled (Fig. 2). When comparing differences
between sites, concentrations of sediment Al, Mn and Fe
were significantly lower (p<0.05) at the HMPA than Strand.
Both water and sediment metal concentrations were below
the sediment quality guidelines proposed for the Benguela
region22, indicating that all the sites sampled were not heavily
polluted. The elevated Mn and Zn concentrations could be
related to the intensity of urban development and the run-off
related contamination from surrounding agricultural and
Sediment plays an important role in the transportation of
metals across the bay as it influences the amount of metals
that are available in the water column and ultimately the
bioavailability to filter-feeding organisms34. According to
.31 the hydrodynamics in False Bay is influenced
by the shape of the bay and this could have accounted for
similar metal concentrations at the HMPA, Lourens river and
The high coastal water Mn concentrations in the HMPA
and Lourens river may be due to the industrial discharge from
industrial activities to the north of the HMPA and the Macassar
waste water works located to the west of the HMPA37. Due to
the constant movement and fluctuation of water currents,
majority of the metal concentrations in the water ranged from
very low and undetectable levels31. The elevated sediment Mn
concentrations at the HMPA may be due to the circular
movement of longshore coastal currents along the three sites.
Concentrations of As, Mo, Cd, Cu and Zn were
significantly higher (p<0.05) in the mussel
M . g al l op r ov i nc i al i s
than sediment (Fig. 2). As filter feeding organisms, these
mussels have the potential to accumulate a significant
amount of metals from the ambient environment (water
and sediment) as metals are bioavailable to accumulate in
mussels30. Of the metals measured in mussels, Cd was
higher in the HMPA than the other two sites sampled. The
uptake of Cd in the soft tissue of mussels is influenced by the
Res. J. Environ. Toxicol., 2016
Mean Mn (µg g dry weight)
Mean Cd (µg g dry weight)
HMPA Lourens Strand
Mean Zn (µg g dry weight)
Mean Mo (µg g dry weight)
Mean Al (µg g dry weight)
Mean Fe ( dry weight)µg g
Mean As (µg g dry weight)
HMPA Lourens Stran
Mean Cu (µg g dry weight)
Fig. 2(a-h):Mean (a) Al, (b) Mn, (c) As, (d) Mo, (e) Cd, (f) Fe, (g) Cu and (h) Zn concentrations (:g gG1 dry weight) (M±SEM, n = 5)
measured in water, sediment and
(soft tissue) at the Helderberg Marine Protected Area
(HMPA) Lourens river (Lourens) and Strand, *Indicates that sediment metal concentrations are significantly different
from HMPA and #Indicates that mussel tissue metal concentrations are significantly different from HMPA
Res. J. Environ. Toxicol., 2016
Table 3: Metal concentrations (µg gG1 dry weight, n = 5) in the mussel
collected at the Helderberg Marine Protected Area (HMPA), Lourens
river and Strand
Station Al Mn As Mo Cd Fe Cu Zn
Mean 23.50 2.00 3.92 0.29 1.84 69.68 2.81 154.86
SEM 3.53 0.19 0.19 0.05 0.17 4.08 0.19 46.28
Minimum 13.88 1.53 3.37 0.16 1.22 55.83 2.26 35.44
Maximum 39.17 2.59 4.58 0.47 2.34 82.21 3.52 360.44
Mean 25.39 3.38 5.37 0.27 0.92 66.21 3.26 133.50
SEM 4.95 0.43 0.57 0.05 0.19 10.77 0.37 34.82
Minimum 7.54 1.51 3.20 0.12 0.20 23.25 1.78 42.99
Maximum 42.22 4.39 7.21 0.41 1.55 90.35 4.25 263.82
Mean 32.44 2.80 9.75 0.67 1.67 89.91 3.84 219.34
SEM 3.72 0.26 0.79 0.13 0.28 8.82 0.36 46.79
Minimum 25.06 1.72 7.45 0.48 0.76 73.14 2.58 122.94
Maximum 48.33 3.48 11.91 1.27 2.86 132.27 4.97 435.57
Table 4: Sediment Contamination Factors (CF) and Pollution Load Index (PLI) of metals at the Helderberg Marine Protected Area (HMPA), Lourens river and Strand
Al Mn As Mo Cd Fe Cu Zn PLI
HMPA ND 1.54 ND ND 0.31 1.46 0.25 1.64 0.98
Lourens ND 1.32 ND ND 0.26 1.34 0.22 1.12 0.97
Strand ND 1.97 ND ND 0.43 2.13 0.36 2.80 1.01
ND: Not determined, Background concentrations based on values from Hennig40
physio-chemical factors such as pH, temperature and the
bioavailability of Cd in the environment28. Although the Cd
concentrations in mussels were lower than that reported
.2 for the region, the results suggests that
anthropogenic sources of Cd could be the cause of elevated
Cd concentrations reported in the HMPA and requires further
investigation, even though the c on c en t ra t io n s w e re be l ow t he
recommended limit for shellfish41.
The As, Mo and Cu metals in mussels increased from
HMPA to Strand with Cd and Zn decreasing from the HMPA
to the Lourens river and then increasing to Strand (Table 3).
The Mn concentrations increased from the HMPA to the
Lourens river and then decreased towards Strand. The As with
the sediment metal concentrations recorded, the increase in
metals in mussel (As, Mo and Cu) may be attributed to the
coastal dynamics of False Bay31.
Contamination Factor (CF) of metal concentrations in the
sediment (except for Al, As and Mo) were calculated at each
site (Table 4), using the background levels of metals recorded
in False Bay by Hennig40. Contamination factors were highest
at Strand for all metals analysed, followed by the HMPA and
the Lourens river. Pollution Load Indices (PLI) calculated for
the sediment for the three sites is illustrated in Table 4.
Categorization of PLI from highest to lowest per site was:
Strand>HMPA>Lourens river. The mean PLI results reported
here are lower than that reported by El-Sammak and
Aboul-Kassim42 where an average of 1.279 was recorded for
all the sites sampled. The mean PLI recorded for the three
sites sampled in False Bay was 0.99. El-Sammak and
Aboul-Kassim42 reported that sites that had PLIs>1.2 were
considered to be affected by pollutants. Given that none of
the site PLI values were greater than 1.2, it is suggested that
none of the sites samples were negatively affected by
exposure to metals and should not be considered polluted
based on PLI values. Furthermore, the PLI values are similar
to other sites in Cape Town. Relatively though, the PLI of
HMPA is higher than the Lourens river, suggesting that,
comparatively the HMPA is not protected from coastal metal
contaminants. The relatively higher PLI level in the HMPA may
be due to the release of industrial effluent to the north of the
MPA and domestic sewage from the adjacent Macassar waste
water treatment facility31. This postulation however, needs
further investigation as the degree of metal released into the
environment is influenced by the type, source and quantity of
The research provided an account of metal
concentrations in and outside a marine protected in
South Africa. The main findings of this study were that metal
concentrations were general ly not lower ins ide the M PA
as would have been expected, suggesting that coastal
dynamics and long shore movement may be responsible for
Res. J. Environ. Toxicol., 2016
the metal concentrations in the HMPA. Furthermore, metal
concentrations in sediment may be related to the settling
rates of sediment from surrounding industrial catchment
areas and domestic effluent released into False Bay. The
elevated metal concentrations in mussels in the HMPA
(relative to sediment) suggests bioaccumulation of the
metals and requires further investigation.
The research was funded by the Cape Peninsula
University of Technology (CPUT) (University Research Fund).
We thank the technical staff at CPUT for assistance with
collecting samples and laboratory analysis as well as the
support from the City of Cape Town and Denel for granting
access to the HMPA.
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