1. Introduction
It has been observed that estuaries are among the most productive
ecosystems in the world and are very vulnerable to anthropogenic
activities. Despite this, they are subject to development pressures such
as harbour development, land reclamation, urban encroachment, pollution
and other anthropogenic inputs [1,2]. Many researchers have used
meiofauna and nematodes in particular as indicators of pollution in
different environments. They include [3-9]. A similar study [10] that
applied toxicity tests on the whole nematode community from Restronguet
Creek, a severely contaminated estuary, showed that nematodes are more
resistant to copper than those from an adjacent, less contaminated
estuary. This is a result of an increase in the abundance of Cu
resistant species, the evolution of enhanced Cu tolerance in some
species and the probable exclusion of more sensitive species.
Grant et al. observed that tolerance to copper and zinc in the
benthic polychaete Nereis diversicolor is inherited [2]. This makes it
possible to use the occurrence of metal tolerant individuals to map the
ecological impact of contamination by these metals.
Although there have been some studies on meiofauna in South Africa
[11-14], only a few have concentrated on using nematodes as pollution
indicators [15,16]. The community structure of the benthic meiofauna of
the Swartkops estuary, with special reference to nematodes, was
investigated in relation to contaminants in the estuary [15]. No studies
on the meiofauna of the Gamtoos estuary have been undertaken prior to
this study.
The Swartkops estuary is located in a highly industrialised area in
Port Elizabeth, in the Eastern Cape Province of South Africa (Figure 1).
There are different forms of agricultural activities in the upper
reaches of the estuary as well. The Gamtoos estuary on the other hand is
not industrialised. The impact on the Gamtoos is mainly from farming
activities in the form of irrigation and livestock watering.
One objective of this study was to use differences in benthic
meiofauna (nematode) communities as a means to contrast the
"polluted" Swartkops estuary and the less impacted Gamtoos
estuary. Another objective of the study was to confirm the pollution
indicator status of some of the nematode genera identified by [15].
2. Study Area
The Swartkops River estuary is situated in Algoa Bay, about 15 km
east of the Port Elizabeth Harbour at 33.87[degrees] S and
25.63[degrees] E. The estuary is 16 km long from its mouth to the head.
The estuary is characterised by sandy beaches on the south bank and at
the mouth, but the north bank rapidly gives way to many jetties and
launching ramps from the residential area of Amsterdamhoek. In the lower
and middle reaches, mud flats and salt marshes occur, but these become
less extensive as the estuary narrows towards the upper reaches. At the
head of the estuary, which is marked by a concrete causeway, the
substratum consists of rounded boulders and the banks are steep.
[FIGURE 1 OMITTED]
The Gamtoos River discharges into St. Francis Bay, west of Port
Elizabeth and is situated at 33.88[degrees] S and 25.62[degrees] E. The
upper reaches of the Gamtoos River estuary are characterised by sandy
beaches with shrub vegetation along their banks. Unlike the Swartkops
River which is highly urbanised and industrialised, the Gamtoos River
estuary flows through agricultural lands. The Gamtoos River estuary is
about 21 km in length.
3. Methods
Field sampling for meiofauna and environmental factors was
undertaken in the two estuaries from May 1997 to March 1998 on
bi-monthly basis at neap tide in sub-tidal zones. This sampling period
follows a previous study of the meiofauna community in the Swartkops
River estuary conducted between May 1995 and March 1996 [15]. The
sampling sites in the Swartkops River estuary were selected to include
sites CRM & KC, identified as polluted and L as unpolluted [15]. The
salinity ranges were 25 30; 10 - 18; 5 - 7 and 0 - 0.5 PSU units for
sites L, CRM, J and KC respectively. The sites selected along the
Gamtoos River estuary, GA, GB, GC and GD had salinity gradients and
sediment particle size distributions similar to the corresponding sites
selected along the Swartkops River estuary. Sampling was done using a
hand held perspex corer (1 m long and 6.5 cm diameter) which penetrated
to a depth of 10 cm as most of the meiofauna are normally found in the
top 10 cm of the sediment [17]. Three replicate samples were taken for
meiofaunal analysis at each site on each sampling trip. Samples for
heavy metal analyses were taken in May 1997 and in March 1998 since the
concentrations of the metals did not vary on a bi-monthly basis. Two
water samples per site were taken bimonthly for chlorophyll-a analysis
over the sampling period.
Nematode extraction was done using a centrifugal flotation method
using sucrose solution as a separating agent [18]. Nematodes were placed
in 5% formalin and counted under stereo microscope using a sorting tray
as described in [15]. Nematode counts were converted to numbers per
[m.sup.2] and identification done using the pictorial key [19].
Heavy metal analyses were carried out, using the methods described
in [15]: Shimadzu sequential plasma spectrometer (ICPS-1000II) and the
calibration curve method. The chlorophyll-a concentration was
determined, using the method [20]. Sediment analysis was done using the
method described by [21]: A 30-g portion of the sediment from each site
was washed with tap water and reweighed after drying. The dry samples
were put on the topmost of a nest of sieves (with mesh size ranging from
0.002 |am to 2 mm) and sieved by a machine for 8 minutes. The fractions
of each sieve were weighed. The median grain size, sorting values, mud
composition and all the other sand fractions were determined using a
computer programme, SANDX--Sandsta.baj as described by [15].
4. Statistical Analyses
Normal distribution tests were done to assess the homogeneity or
normality of samples. ANOVA and LSD tests were used to compare the
nematode densities, organic content, chlorophyll-a, trophic and
population structure at all eight sites in the two river estuaries
during the sampling months. Statistical tests were made for similarities
in, and difference between the sampling sites within and between the
estuaries in the nematode attributes and environmental factors
(salinity, pollutants and sediment particle size distribution). The
nematode densities were log-transformed to reduce variability in the
replicate samples. Absolute numbers were however used in relative
abundance calculations. The relationship between seasons and the
environmental factors on the nematode attributes was also investigated
using correlation and regression analysis, (parametric and
non-parametric) including Spearman-Rank Correlation and Bioenv test
which is a programme within the [22] package. The Spearman-Rank Weighted
Correlation/Bioenv test ranks all the environmental factors based on
their influence on a particular community attribute, e.g. density or
diversity.
The Maturity Index (MI) [23]: was calculated as the weighted
average of the individual colonizer-persister (c-p) values.
MI = [SIGMA] v(i) f (i)
where, v is the c-p value of the taxon (genus) (i) and /(i) is the
frequency of the taxon in the sample. The MI is proposed here as a semi
quantitative value, which indicates the condition of an ecosystem, based
on the composition of the "nematode community".
Multivariate statistical techniques allow us to summarize the
structure of the species associations with minimal loss of complexity
[24]. A similarity matrix was constructed using the Bray--Curtis measure
of similarity on 4th root transformation of the nematode attributes to
further assess the similarity between the sites. The environmental
factors were superimposed on the nematode attributes using the Primer
programme. The relationship between the community structure and
environmental parameters was analysed using the CCA (Canonical
Correspondence Analysis) option from the software CANOCO [25]. It was
used on the data to determine which species are associated with
environmental factors that are most important in the structuring of the
communities [24].
5. Results
5.1. Sediment Particle-Size Distribution
The two estuaries varied little in their particle-size
distribution. There was very little or no very coarse sand (VCS) at most
of the eight sites studied. Apart from site GD, all the sites showed
negatively skewed distributions of the various sediment particle-size
components. The total carbonate component (%) of the sediment was
similar in the two river estuaries although differences existed between
specific sites. The % carbonate was highest at site GA. Site L in the
Swartkops River estuary has a similar sediment particle-size
distribution to sites GA, GC and GD in the Gamtoos River estuary. Site
GB in the Gamtoos River estuary had a similar sediment particle-size
distribution to the other three sites in the Swartkops River estuary,
namely CRM, J and KC (Table 1). The percentage organic carbon content of
the sediment at the eight sites in the two estuaries is shown in Table
1, and indicates that the Swartkops River estuary is relatively enriched
with organic matter.
5.2. Chlorophyll-a Concentrations of Bottom Sediments
There were higher benthic chlorophyll-a concentrations in the
Swartkops River estuary, especially at site KC, compared with sites in
the Gamtoos River estuary (Table 2). There was no significant difference
(P > 0.05, ANOVA) in chlorophyll-a between sites in the Swartkops
estuary. There was also no significant difference (P > 0.05, ANOVA)
in chlorophyll-a on a temporal basis, at each of the four sites in the
Swartkops River estuary. Lower chlorophyll-a values were recorded in the
Gamtoos River estuary. Significant differences however existed between
sites both spatially and temporally in the Gamtoos estuary.
5.3. Heavy Metals in the Sediments of the Swartkops and Gamtoos
River Estuaries Sites GA had the lowest concentrations of the metals.
Site CRM was found to be significantly different (P < 0.05, ANOVA)
from the other sites in terms of metal concentrations. Sites J and KC
also had high concentrations of the metals Cu, Fe, and Mn as compared
with other sites in both river estuaries (Table 3).
5.4. Meiofauna
The main meiofauna taxa in the Swartkops River estuary were found
to be nematodes, Turbellaria, ostracods and copepods, in order of
numerical importance. Copepods had a lower percentage composition
amongst the meiofauna in the Swartkops River estuary compared with the
Gamtoos River estuary (Table 4). Gastrotricha was not represented at all
in the Swartkops River estuary in this study. A percentage dominance
curve of the meiofauna taxa in the two river estuaries is shown in
Figure 2. It shows that the Swartkops River estuary had a higher
percentage dominance of the meiofauna taxa (very few taxa with higher
numbers) as compared to the Gamtoos River estuary. Thus, Gamtoos River
estuary had a greater number of taxa (diversity) with no significant
differences in their numbers.
[FIGURE 2 OMITTED]
ANOVA performed on the nematode numbers, both spatial and temporal,
in the Swartkops River estuary indicated a significant difference (P
< 0.05) between sites and sampling months (Table 5). There was a
significant difference (P < 0.05, ANOVA) nematode numbers between
sites in the Gamtoos estuary but not between the sampling. Site L had
the highest total mean number (0.8 x [10.sup.6] ind/[m.sup.2]) of
nematodes and site J (0.18 x [10.sup.6] ind/[m.sup.2]) the lowest in the
Swartkops River estuary during the period of study. Site GD had the
lowest number of nematodes (0.03 x [10.sup.6] ind/[m.sup.2]) in the
Gamtoos River estuary (Table 6). Higher nematode densities were obtained
during the summer months of September and November 1997 in both
Swartkops and Gamtoos River estuaries. Nematodes numbers were lowest in
May 1997 in the Gamtoos River estuary but in the Swartkops, lower
numbers were obtained in January and March 1998.
The genera recorded in this study are presented as Table 7.
Significant difference (P < 0.05, ANOVA) existed between the four
sites and the sampling months in the numerical distribution of the
nematode genera in the Swartkops River estuary over the one-year
sampling period. Site L at the mouth of the Swartkops River estuary had
the highest number of nematode genera, while site CRM had the least
number of genera over the study period. No significant difference (P
> 0.05, ANOVA) in the number of nematode genera existed either
between the sampling months or between the four sites in the Gamtoos
River estuary, GA, GB, GC and GD. Thus, unlike the Swartkops River
estuary, distribution of the nematode genera in the Gamtoos River
estuary appeared to be more uniform. The highest mean number of genera,
8, was recorded in the middles reaches of the Gamtoos River estuary, at
sites GB and GC.
5.5. Nematode Trophic Diversity
All four feeding types (1A, 1B, 2A and 2B--Wieser's
classification based on mouthparts) were represented in the two
estuaries during the period of study. The percentage composition of the
four feeding types varied from site to site in the Swartkops River
estuary (Figure 3). Non-selective deposit feeders, (Type 1B) contributed
a large percentage of the nematode composition in May, 50%; July, 67%
and September, 66% respectively. Epi-growth feeders (Type 2A)
contributed a higher percentage composition than the Type 1B in November
1997, January 1998 and March 1998 but the differences were only 9%, 9%
and 5% respectively. Type 1B was therefore the dominant feeding type in
the Swartkops.
In the Gamtoos River estuary, Type 1B was the dominant feeding type
during four non-consecutive months. Type 1B contributed 57%, 56.8%,
54.2% and 43.8% of the nematode composition for the months of July 1997,
September 1997, November 1997 and March 1998, respectively. In May 1997
Type 2A was the dominant feeding type comprising 53.1% of the nematode
composition whilst the predators and omnivores (Type 2B) were the
dominant feeding type in January 1998 in the Gamtoos estuary, with a
composition of 46.4%. Spatially, Type 1B was dominant in the Gamtoos as
well (Figure 3). Feeding Type 1B was therefore the dominant feeding
group in both estuaries, but with different degrees of dominance:
Swartkops River estuary--52% and the Gamtoos River estuary--41%. The
mean percentage composition of the nematode feeding types indicates that
Type 2A had the second highest composition in the Swartkops River
estuary comprising 27% of the total. Type 2B was the second most
abundant in the Gamtoos River estuary with composition of 32%. Selective
deposit feeders (Type 1A) had the lowest representation in both the
Swartkops and Gamtoos River estuaries, with a composition of 10% and 2%,
respectively.
5.6. Nematode Attributes in Relation to Environmental Factors
The four nematode feeding types from the two estuaries were pooled
together and the effect of environmental factors investigated using
BIOENV tests. Table 8 gives the score of the weighted Spearman's
correlation between the nematode feeding types and the environmental
factors.
[FIGURE 3 OMITTED]
The metals Zn and Pb, organic carbon and bacterial numbers
correlated with the nematode trophic structure (P < 0.05). All the
other factors listed in Table 8 had influence on the structuring of the
nematode community (the insignificant variables were not listed in Table
8).
A total of fifty-six genera were recorded in this study, from the
two river estuaries. Many of the genera occurred in both estuaries, but
several genera were found exclusively in either the Swartkops or the
Gamtoos River
estuary. Genera such as Aegialoalaimus, Cobbia, Comesoma,
Dorylaimopsis, Haliplectus, Longicyatholaimus, Marylynnia,
Metacyatholaimus, Monhystera, Nannolaimoides, Paracomesoma,
Paramonohystera, Rhynconema, Rhabditis, Scaptrella, Mesodorylaimus and
Mesotheristus occurred only in the Swartkops River. There were seven
genera recorded in the Gamtoos River estuary but not in the Swartkops,
namely Aponema, Ethmolaimus, Euchromadora, Gammarinema, Oncholaimellus,
Tripyloides and Mononchus. Figure 4 depicts the similarities and
differences in nematode communities the two river estuaries between
sites.
Sites CRM and KC are at the extreme ends of the plot. This means
that the two sites have nematode communities that are different from
those found at the other sites based on their preference for the
prevailing environmental conditions. Figure 4 also shows that the
nematode community structure in the Gamtoos River estuary is very
similar at all the four study sites. Whilst the Swartkops River estuary
had an average number of two genera dominating the four sites, the
Gamtoos River estuary had an average of three dominant genera at all
four sites. Paramonohystera was dominant at site L, the mouth of the
Swartkops estuary, comprising 46% of the nematode community.
Paradontophora, Neochromadora and Viscosia were co-dominant at site J,
sharing 46.2% of the nematode community between them. Theristus was the
dominant genus at site CRM, making up 93.5% of the total numbers of the
nematode community structure. Rhabditis was the most dominant (37.1%)
genus at site KC, followed by Haliplectus (14.1%) and Terschellingia
(13.4%).
[FIGURE 4 OMITTED]
The nematode community structure in the Gamtoos River estuary was
different. Viscosia was dominant in the nematode communities at all the
sites in the Gamtoos. Viscosia constituted 59.5%, 30.3%, 35.9% and 18.8%
of total numbers at sites GA, GB, GC and GD, respectively. By contrast,
Viscosia was not abundant along the sites in the Swartkops River
estuary. A Canonical Correspondence Analysis (CCA) was performed to
investigate the possible causes of this distribution pattern. The
results of the analysis displayed in Figure 5 indicate that the nematode
community structure found at sites J, L, GA, GB, GC and GD might have
been caused by sediment characteristics. A greater number of the
nematode communities was associated with the fine sand (FS) sediment
component at these sites (Figure 6) and hence the aggregation of these
sites as indicated in Figure 5.
The ability of nematode species to survive under harsh
environmental conditions, e.g., metal or organic pollution has been
documented [23]. According to these authors, c-p values have been
assigned to various nematode genera based on their response and survival
capabilities in times of stress or disturbance. Table 9 gives the MI
calculated as the weighted average of c-p values, for the nematodes at
various sites in the two river estuaries. Sites that had higher metal
and or organic concentrations (e.g. CRM and KC) have nematode
communities with lower MI values.
[FIGURE 5 OMITTED]
6. Discussion
Site KC had higher concentrations of Cu, Fe and Mn in this study as
compared to the other sites in the Swartkops River estuary. Although Zn
is not particularly considered toxic to marine organisms [26], this
study found it to have influenced the structuring of the nematode
communities in the two estuaries. A similar observation was made [3]
that nematode community structure appears to change in an ordered
fashion with increasing metal concentration through time. There is a
historic record of heavy metal concentrations in the Swartkops River
estuary [15,27] and Gamtoos River estuary [28]. Sites CRM and KC were
identified as sites with higher metal and organic carbon concentrations
[15]. Table 3 gives the concentrations of the seven heavy metals
analysed in the two estuaries during this study.
Several authors [29-32] have observed that certain nematode species
including, Rhabditis and Monhystera are tolerant to hypoxic and anoxic
conditions. These two genera were only found in the Swartkops River
estuary at site KC which has high metal concentrations. As indicated
earlier, there were seven nematode genera identified in the Gamtoos but
not found in the Swartkops River estuary. Apart from Tripyloides and
Mononchus, the other five genera were recorded in an earlier study in
the Swartkops River estuary [16]. This observed change in distribution
(absence of some species) might be attributed to increasing levels of
pollution in the Swartkops River estuary.
[FIGURE 6 OMITTED]
It has been indicated that the nematode community in the Swartkops
River estuary varies in composition and species abundance at specific
sampling sites as a result of prevailing and variable environmental
conditions along the river estuary [15]. The present study has confirmed
the above observation that meiofauna density and diversity varied with
respect to environmental factors such as metal concentrations in the
Swartkops River estuary. The metals zinc (Zn), iron (Fe) and manganese
(Mn) were negatively correlated with the density of nematodes in the
Swartkops and Gamtoos River estuaries. A similar observation as to the
correlation of nematode density with Zn, Pb, Mn and Fe [33].
One possible explanation of the results in Table 9 is that nematode
genera found at sites CRM and KC might be opportunists as compared to
the other sites, especially, those in the Gamtoos River estuary. The
exposure of sites CRM and KC to anthropogenic activities, such as,
industry, extensive agriculture and increased deposition of organic
matter from the settlements along the river estuary, might also account
for these species ability to "colonise" these two sites. These
mentioned activities have increased the concentrations of metals and
organic carbon in the Swartkops River Estuary over time. The MI values
confirm the Non-metric multidimensional scaling (NMMDS) plots in Figures
5 and 6, in that, the sites with low MI are considered to be under
stress from metal and organic pollution. The nematode genera associated
with site KC include Monhystera, Metalinhomoeus, Rhabditis,
Diplolaimella, Mesotheristus and Terschellingia. Since the metal
concentrations and organic carbon concentrations were higher at this
site, the genera present at this site may be tolerant to the two types
of pollution. Theristus is found in organic polluted sites. It was the
only genus that dominated the site CRM which is also considered as
polluted (higher concentrations of Pb, Sn and organic carbon). It is
therefore difficult to pin-point which of the two, metal or organic
carbon pollution, is solely responsible for the dominance of Monhystera,
Metalinhomoeus, Rhabditis, Diplolaimella, Mesotheristus and
Terschellingia at KC or Theristus at site CRM. The differences in the
composition of benthic meiofauna communities in the two river estuaries
might therefore largely depend on the synergistic effects of prevailing
environmental factors. The dominant nematode feeding type 1B was present
at the sites considered to be stressed. This feeding type 1B may adapt
to stressed conditions better than the other feeding types. Apart from
the fine sand (FS) component of the sediment (see Figures 5 and 6), no
other environmental factors were found to have significantly influenced
the structuring of the following genera; Paramonohystera, Euchromadora,
Aponema, Viscosia, Oncholaimellus, Oncholaimus, Nannolaimus, Perrickia,
Praeacanthonchus, Elzalia, Polygastrophora, Cobbia, Longicyatholaimus,
Scaptrella, Axonolaimus, Adoncholaimus, Dorylaimopsis, Comesoma,
Rhynchonema, Xyala, Neochromadora, Ethmolaimus, Daptonema,
Chromadorella.
7. Conclusions
This study has revealed that it is difficult to differentiate
between the quantitative effects of individual metals (e.g. Cu, Zn, Fe,
Pb), on the structure of nematode communities. Concentrations of the
metals (Cu, Zn, Fe, Pb), organic carbon and chlorophyll-a are higher in
the sediments of the Swartkops River estuary. The sites with higher
concentration of metals and organic carbon had a distinct nematode
structure (e.g. site CRM with Theristus as the only genus). It is
unclear if the nematode genera identified at sites CRM and KC preferred
the organic carbon or the metals associated with these sites. None of
the organic carbon or the individual metals can be singled out as the
actual cause for the structuring of the nematode communities, as
concentrations of organic carbon and the identified metals were high at
these two sites. This contrasts with the observations made [34,35], who
showed the effects of different metals on the structure of meiobenthic
communities, could be differentiated from one another. A laboratory
experiment on the meiofauna (nematodes) [16] confirmed that there is no
unique way of response to specific metal contaminants by nematodes. It
has been observed that responses of nematodes to lead and zinc
contaminations were varied [9].
Monhystera, Metalinhomoeus, Rhabditis, Diplolaimella,
Mesotheristus, Theristus and Terschellingia showed a preference for
stressed conditions, including metal and organic pollution, and can
therefore be considered as genera that can indicate stressed conditions.
These genera were only found in the Swartkops estuary. [15] suggested
that Theristus and Monhystera could be indicator species for organic and
metal pollution. Since the various analyses in this study and [15],
isolate Theristus, Monhystera and Rhabditis as species that prefer or
can colonise polluted sites, it can be implied that nematodes can
actually be used as organism that can provide an indication of sediment
pollution in the coastal rivers of the Eastern Cape of South Africa. The
different analyses performed in this study also confirm that the sites
in the Swartkops River estuary are more polluted than those in the
Gamtoos River estuary. It is suggested that more studies of this kind be
carried out along the coast of Africa and globally to establish the
potential indicator value of nematodes.
8. Acknowledgements
I am grateful to the Zoology Department of the University of Port
Elizabeth and Rand Water Analytical Services (both in South Africa), for
the use of their laboratory facilities during the study period. I also
thank Dan Baird (South Africa) and Tom Bongers (Dept. of Nematology,
University of Wagahegen, Netherlands) for their inputs, Ann Vanreusel
(Ghent, Belgium) and Aldo Zulini (Italy) for their help during the
identification of some of the nematode species.
doi: 10.4236/jwarp.2011.37057
Received March 31, 2011; revised May 2, 2011; accepted June 7, 2011
9. References
[1] P. Morant and N. Quinn, "Influence of Man and Management
of South African Estuaries," In: B. R. Allanson and D. Baird, Eds.,
Estuaries of South Africa, Cambridge University Press, Cambridge, 1999,
pp. 289-320.
[2] A. Grant, J. G. Hateley and N. V. Jones, "Mapping the
Ecological Impact of Heavy Metals on the Estuarine Polychaete Nereis
Diversicolor Using Inherited Metal Tolerance," Marine Pollution
Bulletin, Vol. 20, No. 5, 1989, pp. 235-238.
doi:10.1016/0025-326X(89)90438-4
[3] P. J. Sommerfield, M. J. Gee and R. M. Warwick, "Benthic
Community Structure in Relation to an Instantaneous Discharge of Waste
Water from a Tin Mine," Marine Pollution Bulletin, Vol. 28, No. 6,
1994, pp. 363-369. doi:10.1016/0025-326X(94)90273-9
[4] S. Gascon, D. Boix, J., Sala and X. D. Quintana, "Nematode
Assemblages and Their Responses to Disturbances: A Case Study from the
Emporda Wetlands (Northeastern Iberian Peninsula)," Journal of the
North American Benthological Society, Vol. 25, No. 3, 2006, pp. 643-655.
doi:10.1899/0887-3593(2006)25[643:NAATRT]2.0.CO;2
[5] E. Abebe, I. Andrassy and W. Traunspurger, "Fresh Water
Nematodes--Taxonomy and Assemblages," CABI Publishing, Wallingford,
2006.
[6] N. Smol, K. A. Willems, J. C. R. Govaere and A. J. J. Sandee,
"Composition, Distribution, Biomass of Meiobenthos in the
Oosterschelde Estuary (SW Netherlands)," Hydrobiologia, Vol.
282-283, No. 1, 1994, pp. 197-217. doi:10.1007/BF00024631
[7] F. Boufahja, A. Hedfi, J. Amorri, P. Aissa, H. Beyrem and E.
Mahmoudi, "An Assessment of the Impact of Chromium-Amended Sediment
on a Marine Nematode Assemblage Using Microcosm Bioassays,"
Biological Trace Element Research, Vol. 142, No. 2, 2010, pp. 242-255.
[8] H. Beyrem, E. Mahmoudi, N. Essid, A. Hedfi, F. Bou fahja and P.
Aissa, "Individual and Combined Effects of Cadmium and Diesel on a
Nematode Community in a Laboratory Microcosm Experiment,"
Ecotoxicology and Environmental Safety, Vol. 68, No. 3, 2007, pp.
412-418. doi:10.1016/j.ecoenv.2006.12.007
[9] E. Mahmoudi, N. Essid, H. Beyrem, A. Hedfi, F. Bou fahja, P.
Aissa and P. Vitiello, "Mussel-Farming Effects on Mediterranean
Benthic Nematode Communities," Nematology, Vol. 10, No. 3, 2008,
pp. 323-333. doi:10.1163/156854108783900285
[10] N. R. Millward and A. Grant, "Assessing the Impact of
Copper on Nematode Communities from a Chronically Metal-Enriched Estuary
Using Pollution-Induced Community Tolerance," Marine Pollution
Bulletin, Vol. 30, No. 11, 1995, pp. 701-706.
doi:10.1016/0025-326X(95)00053-P
[11] A. McLachlan, "Studies on the Psammolittoral Meiofauna of
Algoa Bay. South Africa. II. The Distribution, Composition and Biomass
of the Meiofauna and Macrofauna," Zoology African, Vol. 12, 1977,
pp. 33-60.
[12] L. E. McGwynne, A. McLachlan and J. P. Furstenberg,
"Wrack Breakdown on Sandy Beaches: Its Impact on Interstitial
Meiofauna," Marine Environmental Research, Vol. 25, No. 3, 1988,
pp. 213-232. doi:10.1016/0141-1136(88)90004-9
[13] J. P. Furstenberg and M. Vincx, "The New Chromadoropsis
Species. (Nematoda, Desmoridae) from Southern Africa and the North
Sea," South African Journal of Zoology, Vol. 23, No. 3, 1988, pp.
215-223.
[14] J. P. Furstenberg and M. Vincx, "Two New Species of the
Family Microlaimidae (Nematoda: Order Chromadorida) from South
Africa," Cahiers de Biologie Marine, Vol. 33, No. 2, 1992, pp.
245-251.
[15] T. K. Gyedu-Ababio, J. P. Furstenberg, D. Baird and A.
Vanreusel, "Nematodes as Indicators of Pollution: A Case Study from
the Swartkops River Estuary, South Africa," Hydrobiologia, Vol.
397, 1999, pp. 155-169. doi:10.1023/A:1003617825985
[16] T. K. Gyedu-Ababio and D. Baird, "Response of Meiofauna
& Nematodes to Increased Levels of Contamination in a Laboratory
Experiment," Ecotoxicology and Environmental Safety, Vol. 63, No.
3, 2006, pp. 443-450. doi:10.1016/j.ecoenv.2005.01.010
[17] C. Heip, M. Vincx and G. Vranken, "The Ecology of Marine
Nematodes," Oceanography and Marine Biology, Annual. Revue, Vol.
23, 1985, pp. 399-489.
[18] R. T. Lackey and B. E. May, "Use of Sugar Flotation and
Dye to Sort Benthic Samples from Marine and Limnic Sediments,"
Netherlands Journal of Sea Research, Vol. 7, 1971, pp. 233-243
[19] H. M. Platt and R. M. Warwick, "Free Living Marine
Nematodes, Part II: British Chromadorids," Cambridge University
Press, Cambridge, 1988.
[20] R. Mantoura and C. Llewellyn, "The Rapid Determination of
Algal Chlorophyll and Carotenoid Pigments and Their Breakdown Products
in Natural Waters by Reverse-Phase High-Liquid Chromotography,"
Analytica Chimica Acta, Vol. 151, 1983, pp. 297-314.
doi:10.1016/S0003-2670(00)80092-6
[21] S. Parker, "Determination of Soil Organic Content,"
In: R. E. Carver, Ed., Procedures in Sediment Petrology, John Willey
& Sons, New York, 1983, pp. 389-401.
[22] Plymouth Marine Laboratory, "PRIMER, Plymouth Rou tine in
Marine Environmental Research. Non-Metric Multidimensional
Scaling," Oceanography and Marine Biology, Annual. Revue, Vol. 37,
No. 1, 2002..
[23] T. Bongers, R. Alkemade and G. W. Yeates, "Interpretation
of Disturbance-Induced Maturity Decrease in Marine Nematode Assemblages
by Means of the Maturity Index," Marine Ecology Progress Series,
Vol. 76, 1991, pp. 135-142. doi:10.3354/meps076135
[24] J. Mees and O. Hamerlyncl, "Introduction to Descriptive
Multivariate Statistics," Tutorial Handout, Marine Biology Section
of the University of Gent, 1996, p. 18.
[25] C. J. F. Ter Braak, "CANOCO-FORTRAN Program for Canonical
Community Ordination by (Partial) Detrended (Canonical) Correspondence
Analysis and Redundancy Analysis," TNO Institute of Applied
Computer Science, Statistical Department, Wageningen, 1987.
[26] G. W. Bryan and W. J. Langston, "Bioavailability,
Accumulation and Effects of Heavy Metals in Sediments with Special
Reference to UK Estuaries: A Review," Environmental Pollution, Vol.
76, No. 2, 1999, pp. 89-131. doi:10.1016/0269-7491(92)90099-V
[27] R. J. Watling and H. R. Watling, "Metal Surveys in South
African Estuaries. II. Gamtoos River. Report II. Zoology
Department," University of Port Elizabeth, Port Elizabeth, 1982.
[28] R. J. Watling and H. R. Watling, "Metal Surveys in South
African Estuaries. I. Swartkops River," Water SA, Vol. 8, 1988, pp.
26-35.
[29] T. M. Fenchel and R. J. Riedel, "The Sulphide System: A
New Biotic Community underneath the Oxidised Layer of Marine Sand
Bottoms," Marine Biology, Vol. 7, No. 3, 1970, pp. 255-268.
doi:10.1007/BF00367496
[30] J. A. Ott, "Determination of Fauna Boundaries of
Nematodes in an Intertidal Sand Flat," Internationale Revue der
gesamten Hydrobiologie und Hydrographie, Vol. 57, No. 4, 1972, pp.
645-663. doi:10.1002/iroh.19720570413
[31] J. A. Ott and F. Schiemer, "Respiration and Anaerobiosis
of Free Living Nematodes," Oecologia, Vol. 2, 1973, pp. 251-291.
[32] J. A. Ott and R. Novak, "Living at an Interface:
Meiofauna at the Oxygen/Sulfide Boundary of Marine Sediments," In:
J. S. Ryland and P. A. Tyler, Eds., Reproduction, Genetics and
Distribution of Marine Organisms, Olsen & Olsen, Fredensborg, 1989,
pp. 415-422.
[33] N. Smol, K. A. Willems, J. C. R. Govaere and A. J. J. Sandee,
"Composition, Distribution, Biomass of Meiobenthos in the
Oosterschelde Estuary (SW Netherlands)," Hydrobiologia, Vol.
282-283, No. 1, 1994, pp. 197-217. doi:10.1007/BF00024631
[34] M. C. Austen, A. J. McEvoy and R. M. Warwick, "The
Specificity of Meiobenthic Community Response to Different Pollutants:
Results from Microcosm Experiments," Marine Pollution Bulletin,
Vol. 28, No. 9, 1994, pp. 557563. doi:10.1016/0025-326X(94)90075-2
[35] M. C. Austen and P. J. Sommerfield, "A community level
sediment bioassay applied to an estuarine heavy metal gradient,"
Marine Environmental Research, Vol. 43, No. 4, 1997, pp. 315-328.
doi:10.1016/S0141-1136(96)00094-3
Thomas Kwadwo Gyedu-Ababio
Kruger National Park, Phalaborwa, South Africa
E-mail: thomas.gyedu-ababio@sanparks.org
Table 1. Sediment particle-size distribution at the
8 study sites in the Swartkops and Gamtoos River
estuaries (May 1997-March 1998).
SITE
VARIABLE SWARTKOPS
L CRM J KC
MEDIAN (urn) 2.64 2.33 3.1 2.65
MEAN (um) 2.57 2.29 2.8 2.62
SORT (um) 0.35 0.55 0.67 0.83
SKEWN (um) -0.21 -0.07 -0.3 -0.03
KURT (um) 0.57 0.93 1.6 0.55
>VCS 0 0 1.2 0
VCS 0 1.9 1.6 0.4
CS 0 0.8 1.9 0.6
MS 3.4 11.2 2.6 6.2
FS 88 39.8 13.4 17.4
VFS 6.4 3.6 27.3 14.4
MUD 2.2 42.6 51.8 61
ORGANIC 1.07 3.96 4.33 5.5
CARBONATE 9.68 4.75 12.6 5.26
VARIABLE GAMTOOS
GA GB GC GD
MEDIAN (urn) 2.19 3.29 2.57 2.65
MEAN (um) 2.17 3.15 2.54 2.68
SORT (um) 0.5 0.64 0.45 0.63
SKEWN (um) -0.04 -0.21 -0.07 0.05
KURT (um) 0.67 0.47 0.94 0.76
>VCS 0 0 0 0
VCS 0 0 0 0.1
CS 1.2 0.1 0.4 2.4
MS 30.9 1.4 7.8 10.2
FS 60.4 12 61.4 56.9
VFS 3.9 24.6 12.5 26.9
MUD 3.6 62 18 3.5
ORGANIC 0.48 1.39 0.65 0.7
CARBONATE 23.15 4.26 2.22 1.9
>VCS--more than very coarse sand; VCS--very coarse sand;
CS--coarse sand; MS--Medium sand; FS--fine sand;
VFS--very fine sand.
Table 2. Chlorophyll-a values ([micro]g per [m.sup.2])
at the sites in the two river estuaries (May 1997 to
March 1998).
Month SWARTKOPS
L CRM J KC
May '97 21.48 24.44 5.04 52.00
July '97 11.91 17.42 8.71 21.39
September '97 12.34 15.71 47.76 946.02
November '97 12.13 16.57 28.24 483.71
January '98 15.24 19.19 20.51 120.23
March '98 14.46 18.53 22.44 41.22
Mean 14.59 18.64 22.12 277.43
Std deviation 3.64 3.11 15.29 370.53
Std Error 1.49 1.27 6.24 151.27
Month GAMTOOS
GA GB GC GD
May '97 6.96 8.87 3.48 6.52
July '97 3.48 4.52 1.22 3.04
September '97 59.69 30.83 8.51 19.62
November '97 31.58 17.67 4.86 11.33
January '98 23.37 14.74 4.40 9.73
March '98 25.43 15.47 4.52 10.13
Mean 25.09 15.35 4.50 10.06
Std deviation 20.18 9.00 2.37 5.57
Std Error 8.24 3.67 0.97 2.27
Table 3. Mean metal concentrations ([micro]g/g sediment)
at the sampling sites in the Swartkops and Gamtoos River
esturies in May 1997 and March 1998 (SD values in brackets).
SITES
Metals SWARTKOPS
L CRM
Cu 46 (0.03) 65 (3.0)
Fe 1900 (14.14) 4500 (84.85)
Mn 64 (5.66) 188 (2.83)
Pb BD 39 (4.24)
Sn 3050 (14.14) 9660 (226.27)
Zn 24 (1.41) 69 (2.83)
Metals
J KC
Cu 67 (7.02) 69 (8.58)
Fe 16420 (565.69) 16400 (282.84)
Mn 229 (1.70) 302 (2.83)
Pb BD BD
Sn 1240 (141.42) 1910 (197.99)
Zn 72 (14.14) 210 (0)
Metals GAMTOOS
GA GB
Cu 57 (0.15) 65(1.41)
Fe 3520 (28.28) 12630 (77.78)
Mn 161 (7.07) 191 (1.41)
Pb BD BD
Sn 6680 (183.85) 190 (14.14)
Zn 22 (1.41) 39 (0)
Metals
GC GD
Cu 54 (0.07) 55 (4.19)
Fe 6850 (70.71) 5600 (141.42)
Mn 104 (5.66) 84 (0.71)
Pb BD BD
Sn 300 (21.21) 820 (28.28)
Zn 30 (0) 43 (2.12)
BD--Below detection limit
Table 4. Mean percentage composition of meiofauna in the
Swartkops and Gamtoos River estuaries (May 1997-March 1998).
SAMPLING SITES
MEIOFAUNA SWARTKOPS
L CRM J KC
Nematodes 82 41 31 61
Copepods 2 24 15 3
Turbellarians 11 8 33 4
Amphipods 0 0 1 0
Halocarida 0 2 1 1
Polychaetes 0 0 1 0
Kinorhynchia 1 0 5 1
Oligochaetes 0 2 1 11
Insects 0 4 2 1
Gastrotricha 0 0 0 0
Ostracods 4 19 10 18
Ciliophora 0 0 0 0
Cladocera 0 0 0 0
MEIOFAUNA GAMTOOS
GA GB GC GD
Nematodes 62 23 44 41
Copepods 14 18 20 7
Turbellarians 9 5 2 10
Amphipods 0 4 3 0
Halocarida 5 3 1 4
Polychaetes 0 16 0 5
Kinorhynchia 4 16 18 3
Oligochaetes 1 3 7 0
Insects 3 3 0 5
Gastrotricha 0 0 0 3
Ostracods 2 9 5 22
Ciliophora 0 0 0 0
Cladocera 0 0 0 0
Table 5. Variation in nematode numbers on spatial and
temporal basis in the Swartkops River estuary
(May 1997 to March 1998)
Source of Variation SS df MS
Months (temporal) 541579.3 5 108315.9
Sites (spatial) 280462.3 3 93487.44
Error 275199.7 15 18346.64
Total 1097241 23
Source of Variation F P-value F crit
Months (temporal) 5.903852 0.003282 2.801295
Sites (spatial) 5.095615 0.012499 3.287383
Error
Total
Table 6. Mean monthly nematode density (No./[m.sup.2])
at the study sites in the Swartkops and Gamtoos River
estuaries from May 1997 to March 1998 (SD in brackets).
SITES
Density/[m.sup.2] SWARTKOPS
L CRM
May '97 1.32 x [10.sup.6] 0.07 x [10.sup.6]
July '97 0.30 x [10.sup.6] 0.66 x [10.sup.6]
September '97 1.61 x [10.sup.6] 1.04 x [10.sup.6]
November '97 1.30 x [10.sup.6] 0.54 x [10.sup.6]
January '98 0.15 x [10.sup.6] 0.01 x [10.sup.6]
March '98 0.13 x [10.sup.6] 0.01 x [10.sup.6]
Mean (SD) 0.80 x [10.sup.6] 0.39 x [10.sup.6]
(0.6 x [10.sup.6]) (0.43 x [10.sup.6])
Density/[m.sup.2]
J KC
May '97 0.34 x [10.sup.6] 0.36 x [10.sup.6]
July '97 0.07 x [10.sup.6] 0.39 x [10.sup.6]
September '97 0.44 x [10.sup.6] 0.73 x [10.sup.6]
November '97 0.20 x [10.sup.6] 0.44 x [10.sup.6]
January '98 0.02 x [10.sup.6] 0.04 x [10.sup.6]
March '98 0.01 x [10.sup.6] 0.03 x [10.sup.6]
Mean (SD) 0.18 x [10.sup.6] 0.33 x [10.sup.6]
(0.18 x [10.sup.6]) (0.26 x [10.sup.6])
Density/[m.sup.2] GAMTOOS
GA GB
May '97 0.10 x [10.sup.6] 0.01 x [10.sup.6]
July '97 0.39 x [10.sup.6] 0.11 x [10.sup.6]
September '97 0.39 x [10.sup.6] 0.04 x [10.sup.6]
November '97 0.29 x [10.sup.6] 0.06 x [10.sup.6]
January '98 0.13 x [10.sup.6] 0.06 x [10.sup.6]
March '98 0.02 x [10.sup.6] 0.08 x [10.sup.6]
Mean (SD) 0.22 x [10.sup.6] 0.06 x [10.sup.6]
(0.16 x [10.sup.6]) (0.03 x [10.sup.6]
Density/[m.sup.2]
GC GD
May '97 0.09 x [10.sup.6] 0.03 x [10.sup.6]
July '97 0.23 x [10.sup.6] 0.05 x [10.sup.6]
September '97 0.05 x [10.sup.6] 0.01 x [10.sup.6]
November '97 0.09 x [10.sup.6] 0.02 x [10.sup.6]
January '98 0.66 x [10.sup.6] 0.03 x [10.sup.6]
March '98 0.18 x [10.sup.6] 0.04 x [10.sup.6]
Mean (SD) 0.22 x [10.sup.6] 0.03 x [10.sup.6]
(0.23 x [10.sup.6]) (0.01 x [10.sup.6])
Table 7. Nematode numbers, feeding type and c-p values at
study sites in the Swartkops and Gamtoos River estuaries
(May 1997 to March 1998).
Genus c-p value Feeding
Type
Adoncholaimus 3 2B
Aegialoalaimus 4 1A
Anoplostoma 2 1B
Aponema 3 2A
Axonolaimus 2 1B
Butlerius 1 2B
Chromadorella 3 2A
Cobbia 3 1B
Comesoma 3 2A
Daptonema 2 1B
Dichromadora 3 2A
Dipolaimella 2 1A
Dorylaimopsis 2 2A
Elzalia 2 1B
Ethmolaimus 3 2B
Euchromadora 3 2A
Gammanema 2 2B
Gonionchus 2 1B
Halalaimus 4 1A
Haliplectus 2 1A
Karkinochromadora 3 2A
Longicyatholaimus 3 2A
Marylynnia 3 2B
Mesodorylaimus 4 2A
Mesotheristus 2 1B
Metachromadora 3 2A
Metacyatholaimus 3 2A
Metalinhomoeus 2 1B
Microlaimus 2 2A
Monhystera 2 1B
Mononchus 4 1A
Nannolaimoides 3 2A
Neochromadora 3 2A
Oncholaimellus 3 2B
Oncholaimus 3 2B
Paracanthonchus 2 2A
Paracomesoma 3 2A
Paracyatholaimus 2 2A
Paramonohystera 2 1B
Parodontophora 4 2B
Perrickia 4 2A
Polygastrophora 4 2B
Pomponema 3 2B
Praeacanthonchus 3 2A
Pseudochromadora 3 2A
Rhabditis 1 1A
Rhynconema 3 2B
Sabatieria 2 1B
Scaptrella 2 2B
Synodontium 2 1B
Synonchium 3 2B
Terschellingia 3 1B
Theristus 2 1B
Tripyloides 2 1B
Viscosia 3 2B
Xyala 3 1B
SITE
Genus SWARTKOPS
L CRM
Adoncholaimus 8 0
Aegialoalaimus 0 0
Anoplostoma 6 1
Aponema 0 0
Axonolaimus 18 0
Butlerius 0 0
Chromadorella 9 0
Cobbia 7 0
Comesoma 1 0
Daptonema 18 0
Dichromadora 3 0
Dipolaimella 0 0
Dorylaimopsis 8 0
Elzalia 0 0
Ethmolaimus 0 0
Euchromadora 0 0
Gammanema 0 0
Gonionchus 18 0
Halalaimus 0 0
Haliplectus 0 0
Karkinochromadora 0 0
Longicyatholaimus 10 0
Marylynnia 6 0
Mesodorylaimus 0 0
Mesotheristus 0 0
Metachromadora 10 10
Metacyatholaimus 7 0
Metalinhomoeus 5 4
Microlaimus 23 2
Monhystera 10 19
Mononchus 0 0
Nannolaimoides 47 0
Neochromadora 3 2
Oncholaimellus 0 0
Oncholaimus 0 0
Paracanthonchus 4 0
Paracomesoma 18 0
Paracyatholaimus 44 0
Paramonohystera 407 0
Parodontophora 1 0
Perrickia 6 0
Polygastrophora 2 0
Pomponema 30 0
Praeacanthonchus 10 0
Pseudochromadora 2 2
Rhabditis 0 5
Rhynconema 4 0
Sabatieria 8 0
Scaptrella 33 0
Synodontium 0 0
Synonchium 0 0
Terschellingia 0 0
Theristus 0 673
Tripyloides 0 0
Viscosia 76 2
Xyala 10 0
Genus SWARTKOPS
J KC
Adoncholaimus 0 0
Aegialoalaimus 0 34
Anoplostoma 33 5
Aponema 0 0
Axonolaimus 24 0
Butlerius 0 1
Chromadorella 0 0
Cobbia 0 0
Comesoma 0 0
Daptonema 41 0
Dichromadora 8 0
Dipolaimella 0 44
Dorylaimopsis 65 0
Elzalia 7 0
Ethmolaimus 0 0
Euchromadora 0 0
Gammanema 0 0
Gonionchus 0 2
Halalaimus 7 47
Haliplectus 0 123
Karkinochromadora 0 3
Longicyatholaimus 0 0
Marylynnia 4 0
Mesodorylaimus 0 2
Mesotheristus 0 1
Metachromadora 0 0
Metacyatholaimus 0 1
Metalinhomoeus 16 35
Microlaimus 58 1
Monhystera 42 56
Mononchus 0 0
Nannolaimoides 0 8
Neochromadora 110 0
Oncholaimellus 0 0
Oncholaimus 0 1
Paracanthonchus 2 0
Paracomesoma 15 39
Paracyatholaimus 2 7
Paramonohystera 32 0
Parodontophora 136 2
Perrickia 0 0
Polygastrophora 10 0
Pomponema 0 0
Praeacanthonchus 0 0
Pseudochromadora 8 0
Rhabditis 0 323
Rhynconema 0 0
Sabatieria 0 0
Scaptrella 0 0
Synodontium 0 0
Synonchium 0 11
Terschellingia 0 117
Theristus 2 8
Tripyloides 0 0
Viscosia 77 0
Xyala 0 0
Genus GAMTOOS
GA GB
Adoncholaimus 78 7
Aegialoalaimus 0 0
Anoplostoma 3 12
Aponema 0 3
Axonolaimus 93 1
Butlerius 0 0
Chromadorella 2 0
Cobbia 0 0
Comesoma 0 0
Daptonema 8 4
Dichromadora 0 0
Dipolaimella 0 0
Dorylaimopsis 0 0
Elzalia 0 4
Ethmolaimus 0 4
Euchromadora 2 0
Gammanema 58 27
Gonionchus 10 6
Halalaimus 7 0
Haliplectus 0 0
Karkinochromadora 0 0
Longicyatholaimus 0 0
Marylynnia 0 0
Mesodorylaimus 0 0
Mesotheristus 0 0
Metachromadora 2 0
Metacyatholaimus 0 0
Metalinhomoeus 0 0
Microlaimus 1 7
Monhystera 0 0
Mononchus 0 0
Nannolaimoides 0 0
Neochromadora 3 13
Oncholaimellus 12 10
Oncholaimus 0 0
Paracanthonchus 0 2
Paracomesoma 0 0
Paracyatholaimus 0 1
Paramonohystera 0 0
Parodontophora 4 35
Perrickia 0 0
Polygastrophora 0 0
Pomponema 0 3
Praeacanthonchus 0 41
Pseudochromadora 4 7
Rhabditis 0 0
Rhynconema 0 0
Sabatieria 4 0
Scaptrella 0 0
Synodontium 0 0
Synonchium 4 5
Terschellingia 0 15
Theristus 8 19
Tripyloides 0 0
Viscosia 472 100
Xyala 18 4
Genus GAMTOOS
GC GD
Adoncholaimus 12 0
Aegialoalaimus 0 0
Anoplostoma 16 4
Aponema 0 0
Axonolaimus 26 8
Butlerius 0 3
Chromadorella 0 0
Cobbia 0 0
Comesoma 0 0
Daptonema 190 26
Dichromadora 1 5
Dipolaimella 4 0
Dorylaimopsis 0 0
Elzalia 2 0
Ethmolaimus 3 5
Euchromadora 0 0
Gammanema 74 16
Gonionchus 0 0
Halalaimus 0 0
Haliplectus 0 0
Karkinochromadora 4 0
Longicyatholaimus 0 0
Marylynnia 0 0
Mesodorylaimus 0 0
Mesotheristus 0 0
Metachromadora 0 0
Metacyatholaimus 0 0
Metalinhomoeus 0 5
Microlaimus 2 0
Monhystera 0 0
Mononchus 0 4
Nannolaimoides 0 0
Neochromadora 5 3
Oncholaimellus 0 0
Oncholaimus 7 7
Paracanthonchus 10 31
Paracomesoma 0 0
Paracyatholaimus 0 1
Paramonohystera 0 0
Parodontophora 20 6
Perrickia 0 2
Polygastrophora 0 0
Pomponema 25 2
Praeacanthonchus 2 0
Pseudochromadora 3 1
Rhabditis 0 0
Rhynconema 0 0
Sabatieria 0 0
Scaptrella 0 0
Synodontium 1 0
Synonchium 0 5
Terschellingia 1 3
Theristus 4 1
Tripyloides 0 8
Viscosia 231 31
Xyala 0 0
* c-p = coloniser-persister.
Table 8. Results of Spearman's weighted correlation
between nematode feeding types and environmental factors
(May 1997-March 1998).
Environmental factor r
Zn 0.449
Pb 0.581
VCS 0.586
Organic carbon 0.659
Bacteria 0.757
Table 9. Maturity Index (MI) values at study sites in the
Swartkops and Gamtoos River estuaries
(May 1997 to March 1998).
Month SWARTKOPS
L CRM J KC
May '97 2.38 2.00 2.17 2.73
July'97 2.26 1.99 2.24 1.25
Sep '97 2.25 2.00 2.20 1.39
Nov '97 2.24 1.98 2.9 1.36
Jan '98 2.47 2.9 2.67 2.86
Mar '98 2.49 2.12 2.57 2.88
Mean 2.35 2.03 2.33 2.13
Month GAMTOOS
GA GB GC GD
May '97 1.85 2.33 1.52 2.03
July'97 2.81 2.62 2.00 2.08
Sep '97 2.70 2.26 2.69 2.14
Nov '97 2.68 2.24 2.60 2.9
Jan '98 2.85 2.74 2.82 2.67
Mar '98 2.63 2.72 2.66 2.42
Mean 2.67 2.52 2.43 2.26