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SHORT COMMUNICATION
A portable, low-cost, multipurpose,
surface–subsurface plankton sampler
S. NAYAR1*, B. P. L. GOH2 AND L. M. CHOU1
1REEF ECOLOGY LABORATORY, DEPARTMENT OF BIOLOGICAL SCIENCES,  SCIENCE DRIVE , NATIONAL UNIVERSITY OF SINGAPORE, SINGAPORE
  AND 2NATURAL SCIENCES ACADEMIC GROUP, NATIONAL INSTITUTE OF EDUCATION,  NANYANG WALK, SINGAPORE  
*CORRESPONDING AUTHOR: [email protected]
This note describes a portable, low-cost, pump-based, multi-purpose, surface–subsurface, phytoplankton and zooplankton sampler. It is self-powered by a small 12 V DC battery, and is portable
and ideal for use from a small boat in a river, estuary, or sea. The sampler is equipped with a very
sensitive microprocessor-controlled flow sensor for precise determination of the volume of water
processed by the sampler. A study was carried out to evaluate the performance of this sampler in comparison to the conventional towed plankton net. The results of this study suggest that this pumpbased sampler is as efficient in collecting plankton as using conventional plankton nets, with little
damage to the organisms.
The identification and enumeration of plankton communities is one of the most commonly monitored parameters in aquatic ecological studies, as it provides an
indication of the biological status of the ecosystem. Many
researchers have designed new equipment for plankton
collection and analysis to improve the efficiency of sampling these communities (Smith et al., 1968; Burney, 1984;
George et al., 1984; Rey et al., 1987; Filion, 1991;
Knoechel and Campbell, 1992; Setran, 1992; Madden
and Day, 1992; Brander et al., 1993; McQueen and Yan,
1993; McKinney et al., 1997). Plankton nets are one of the
most popular gears for plankton collection (McQueen and
Yan, 1993), but large errors may arise from improper
design and calibration (Edmondson and Winberg, 1971).
It is not uncommon to encounter problems with shallow
depths, precise subsurface horizontal tows, clogging and
improper metering while using towed plankton gears such
as a plankton net. In addition, it is often tedious to tow a
phytoplankton net beside a zooplankton net, in simultaneous collections along a transect. Owing to problems
encountered with towed gears, several plankton
researchers have embarked on modifying or fabricating
new sampling gears. Pump-based samplers have gained
popularity in recent years, owing to simplicity in their
operation and the precision and accuracy that can be
© Oxford University Press 2002
achieved by integrating electronic accessories (Filion,
1991), such as the microprocessor-based flow sensor in our
sampler described in this paper.
This short note introduces a portable, battery-operated,
continuous phytoplankton and zooplankton sampler
specifically designed to collect plankton from any depth.
In order to determine the efficiency of sampling, we compared the plankton collected using the newly designed
sampler with that collected using a conventional plankton
net.
The sampler was designed to be deployed from a small
boat in any aquatic ecosystem. It was self-powered using
batteries, and therefore portable. The system consisted of
a rigid frame made of aluminium strips holding two large
plastic funnels, each with a capacity of 5 litres, and an
inverted funnel functioning as a splash guide (Figure 1).
The two funnels, namely the parts numbered 5 and 6 in
Figure 1, were lined with zooplankton (upper funnel) and
phytoplankton (lower funnel) netting respectively, held in
place using small plastic clips. The two funnels for collection of zooplankton and phytoplankton were installed
very close to each other to prevent splashing, but at the
same time ensuring sufficient space to facilitate removal
and replacement of the plankton mesh. The spout of the
lower funnel (no.6) held a protective strainer of 250 µm
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mesh size to prevent coarse particles from entering the
flow sensor. The upper inverted funnel was seated on small
slits cut into the aluminium strips, to allow it to be lifted to
facilitate the removal of the zooplankton mesh. All funnels
were attached to the aluminium frame using nuts with
‘butterfly-wing’ bolts, facilitating tightening of the nuts,
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which might otherwise loosen from the constant vibration
of the pump during operation.
The inlet section, which drew water from the source,
comprised a garden hose reel of the desired length and
diameter, depending on the discharge rate, determined by
the efficiency of the pump, and the depth of sampling. A
150 cm
LEGEND
1.
Inlet with a coarse strainer
2.
Reel with the hose
3.
Jabsco Par Max 4 bilge pump
4.
Plastic funnel guide
5.
Plastic funnel with the zooplankton mesh
6.
Plastic funnel with the phytoplankton mesh
7.
Mac Naught digital flow sensor
8.
Outlet
9.
12 V DC battery and back-up
25 cm
10. Aluminium frame
4
∼500 cm
5
10
100 cm
2
3
6
9
8
30cm
7
1
Fig. 1. Schematic diagram showing various components of ZOOPHY.
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S. NAYAR, B. P. L. GOH AND L. M. CHOU
A NEW PLANKTON SAMPLER
coarse strainer in the inlet prevented debris and other
materials from entering the system and causing clogging.
The garden hose reel was fastened to the main frame of
the trolley in our prototype (Figures 1 and 2) using hooks
so that it could be easily removed for maintenance and
cleaning.
The hose was flexible and of non-collapsible PVC. A
short piece of PVC tubing was used to connect the garden
hose reel to a battery-operated marine bilge pump
( JABSCO Par-Max 4, model 30705), with a discharge
capacity of 14.4 l.min–1 and suction lift of 3 m. The prototype described here could effectively collect plankton
samples from depths of up to 15 m but the depth of collection is a function of the suction head of the pump. The
pump of the sampler was powered using a 12 V DC, 24
Ah Yuasa NP24-12B maintenance-free battery. The main
battery and another stand-by were packed in polythene
covers, and placed in a plastic tray near the pump on the
floor of the trolley. The battery was connected to the
pump by a snap-on connector through a waterproof
switch. All electrical connections on the prototype were
insulated using waterproof materials to prevent shortcircuiting. Glass cartridge fuses were installed online to
protect the pump from current surges. The pump was
used to obtain sub-surface water against gravity, while filtration of water samples was achieved by gravity flow. The
selection of a suitable pump is of paramount importance,
B
not only for the efficient functioning of the system, but
also to reduce damage to the delicate planktonic organisms collected. The pump was bolted to the bottom of the
trolley, buffered by a dense rubber seating to reduce vibration. A 1.5 m length of PVC tube was used to connect the
discharge of the pump to the spout of the splash-guard
funnel (part no.4, Figure 1).
A precise, battery-operated, microprocessor-controlled
digital flow sensor (Mac Naught, M5ARG) capable of
metering up to 83.l min–1 was installed at the outlet. It was
connected to the spout of the lower funnel (part no.6,
Figure 1) through a ‘spring-back’ coiled PVC tubing,
similar to that used in household washing machines. For
the outlet from the flow sensor, a longer length of the same
PVC material was used, so that the outlet could be
dropped overboard during filtration.
The whole system was placed on a small trolley, which
in this case was an improvised carrier used to move outboard motors of boats. The entire sampler was made of
non-toxic plastics (PVC, PE and polycarbonate) to minimize the risk of metal contamination because the prototype was also designed to collect surface and subsurface
water samples for monitoring heavy metals and other
physico-chemical and biological parameters. The protoFig. 2. Front (A) and rear (B) view of ZOOPHY with the automatic type of the sampler, which we fabricated, was called
flow sensor and the short outlet pipe.
‘ZOOPHY’ (Figure 2).
A
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The novelty of this sampler lies in its simplicity, and the
low cost and easily available materials with which it was
fabricated. Most components were procured from local
hardware stores, with the exception of the MacNaught
flow sensor. The instrument can in fact be calibrated using
a timer and a graduated bucket to determine the flow rate.
The cost of this prototype was approximately US$ 180,
excluding the flow sensor.
Experiments to test the performance of ZOOPHY
were carried out in July 2000 at four stations on the
Ponggol estuary, situated on the northeastern coast of
Singapore, and four stations in the adjacent East Johor
Strait, between latutudes 01°2487N and 01°2545N
and longitudes 103°5280E and 103°5470E. Comparative studies of ZOOPHY were made with the conventional towed nets for phytoplankton (60 µm mesh) and
zooplankton (200 µm mesh) tied to an outrigger and
towed slowly on either side of an inflatable rubber dinghy
powered by an outboard motor. The nets were 0.5 m in
diameter, with an overall length of 1 m. A digital current
meter (General Oceanics 2030) was towed alongside the
nets to determine the towing distance. Similar mesh sizes,
of 200 µm and 60 µm, were used to sample zooplankton
and phytoplankton respectively using ZOOPHY. Care
was taken to ensure that both ZOOPHY and the conventional plankton nets were deployed simultaneously, at
the same depth, and that the same volume of water was
filtered to minimize sampling errors. All collections were
made from surface waters, as the nets could not be towed
horizontally in subsurface waters. Phytoplankton and zooplankton collected by the two methods were suspended in
filtered sea water taken from each station and preserved
with 10% buffered formalin. Species composition and
numerical abundance were assessed using an Olympus
BX 50 binocular microscope. Factorial analysis of variance (ANOVA) on the log-transformed datasets of phytoplankton and zooplankton biomass was performed using
MINITAB version 13.2 statistical software to test for significant differences between the two methods.
The contribution of the major phytoplankton and zooplankton groups to the total abundance in the estuary and
strait were analysed. It was observed that the stations in
the estuary showed Bacillariophyceae to be dominant, followed by Cyanophyceae and Chlorophyceae (Figure 3a).
The Bacillariophyceae was dominated by Skeletonema costatum, while Chlorococcum humicola and Straustrum orbicularae
dominated the Cyanophyceae and Chlorophyceae groups
respectively (Table I). Stations in the East Johor Strait also
recorded a dominance of Bacillariophyceae and
Cyanophyceae. Skeletonema costatum and Coscinodiscus nitidus
dominated the former, while, the latter was almost wholly
dominated by Chlorococcum humicola. Stations in the estuary
were dominated by copepod nauplii and unidentified
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Bacillariophyceae
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phytoplankton biomass
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Chlorophyceae
Cyanophyceae
100.00
99.80
99.60
99.40
99.20
99.00
98.80
98.60
Estuary
(b)
Mastigophora
Ciliata
Strait
Calanoida
Miscellaneous
100%
% composition to total
zooplankton biomass
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80%
60%
40%
20%
0%
Estuary
Strait
Fig. 3. (a) Relative contribution of different groups of phytoplankton
to the total phytoplankton abundance in Ponggol estuary and East Johor
Strait. (b) Relative contribution of different groups of zooplankton to
the total zooplankton abundance in Ponggol estuary and East Johor
Strait.
bivalves, which accounted for the bulk of the zooplankton
(Figure 3b and Table II). This was also observed at the
stations in the East Johor Strait. The stations in the estuary
were also observed to have a representation of ciliates,
calanoid copepods and dinoflagellates. Dominant forms
recorded under ciliates included Favella ehrenbergii, F. campanula and Tintinnopsis nordguisti. Calanus sp. and Stegosoma
magnum dominated the calanoid copepods, while Dinophysis ovum, Ceratium fusus and Gymnodinium neglectum
accounted for the bulk of the dinoflagellates recorded
from the estuary.
Our results showed a consistent similarity in the total
phytoplankton and zooplankton counts sampled from all
stations using the two methods (Figure 4). The results from
factorial ANOVA (Table III and IV) performed on the data
reveal significant differences between the stations, plankton groups and the interaction effect between stations and
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A NEW PLANKTON SAMPLER
Table II: Percentage species composition of
dominant zooplankton groups recorded from
Ponggol estuary and East Johor Strait
Table I: Percentage species composition of
dominant phytoplankton groups recorded
from Ponggol estuary and East Johor Strait
Species
Estuary
Strait
Dinophysis ovum
25.00
–
Ceratium fusus
24.74
–
C. pennatum
3.12
–
C. furca
6.12
–
12.50
–
Peridinium breve
6.64
–
–
Heterodinium mediterraneum
3.12
–
–
Ornithoceros splendicus
1.04
–
Estuary
Strait
94.60
64.90
Stephanophyxis turris
1.63
2.27
Rhizosolenia hebetata
0.41
1.97
Chaetoceros costatus
0.51
Coscinodiscus gigas
0.63
6.21
C. nitidus
0.58
15.77
Nitzchia philippinarum
0.42
Melosira malayensis
0.34
Species
MASTIGOPHORA
BACILLARIOPHYCEAE
Skeletonema costatum
–
Gymnodinium neglectum
Melosira granulata
–
5.70
CILIATA
Cyclotella kutzingiana
–
1.55
Favella ehrenbergii
32.15
–
F. campanula
31.39
–
F. fistulicauda
3.56
–
26.41
–
T. gracilis
1.29
–
CYANOPHYCEAE
Chlorococcum humicola
69.80
90.09
Anabaena circinalis
18.86
2.20
Tintinnopsis nordguisti
Oscillatoria principes
8.30
–
O. limosa
0.96
5.87
Campanella umbellaria
2.83
–
Merismopedia elegans
2.07
1.84
Amphorellopsis tetragonia
1.19
–
Undella hemispherica
1.19
–
CHLOROPHYCEAE
Straustrum orbicularae
55.21
–
CALANOIDA
Dictyosphaerium pulchellum
19.79
–
Calanus sp.
39.99
–
Spirogyra prolifica
10.00
–
Stegosoma magnum
25.00
–
Mougeotia viridis
10.00
–
Temora turbinata
5.01
–
5.00
–
Paracalanus aculeatus
5.01
–
Cosmarium granatum
MISCELLANEOUS
Nauplii
Crustacean eggs
Bivalve larvae
Gastropod larvae
groups, but no significant differences between the
methods. Although there were significant differences
between the different groups of phytoplankton and zooplankton collected from different stations, statistical analysis showed no significant differences in the species
composition using the two methods. This showed that
collection of both phytoplankton and zooplankton using
ZOOPHY was as efficient as the use of conventional
plankton nets.
In examining the pros and cons of various commonly
used plankton sampling gears, McQueen and Yan gave a
detailed review on metering filtration efficiency of freshwater zooplankton (McQueen and Yan, 1993). They
documented major errors observed in plankton collection
by towed gears due to improper metering. In addition,
Brander et al. reported clogging as one of the major problems encountered that reduced filtration efficiency in
towed plankton gears (Brander et al., 1993). The reduction
67.51
1.43
29.62
1.02
79.39
–
18.83
–
in efficiency of towed nets due to clogging, contamination
by substrate materials and suspended particulate materials, particularly in estuarine habitats, has been documented by other researchers (Barlow, 1955; Cuzon du
Rest, 1963; Barnett et al., 1984). These studies recommend pump-based samplers for plankton collection. In
contrast, Rey et al. reported dissimilarities in both the
quantitative and the qualitative estimates of zooplankton
collected by pump and net samplers, based on a study in
a shallow marsh and estuary in Florida (Rey et al., 1987).
This study reported a similarity of only 70% for certain
groups of zooplankton by the two gears. Their study contradicts our findings where we observed a close similarity
in not only the total phytoplankton and zooplankton
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Phytoplankton counts
-3
(Log 10 No.m )
Zoophy
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Net
8.5
8
7.5
7
6.5
6
5.5
5
4.5
4
E1
E2
E3
E4
S1
S2
S3
S4
Stations
(Log10 No.m )
6
-3
Zooplankton count
7
5
4
3
2
1
0
E1
E2
E3
E4
S1
S2
S3
S4
Stations
Fig. 4. A comparison of total plankton counts collected by the two sampling gears.
biomass retained by the two gears, but also in the major
groups observed using both methods. Scatter plots
(Figures 5 and 6) of the abundance observed indicate that
ZOOPHY sampled most groups with an efficiency equal
to that of the conventional plankton net. Organisms such
as the bivalve larvae, copepod nauplii and larval polychaetes were the major cause of discrepancies when a 200
µm mesh-size net was used by Rey et al. (Rey et al., 1987).
We obtained similar results in this study. The flexibility of
our design for ZOOPHY allows the option of changing
to different plankton mesh sizes, making it ideal for
operation under any conditions and for the collection of
different sizes of plankton.
We observed that the percentage of organisms
damaged after their passage through the pump was negligible. However, some damage to the very delicate forms,
such as Ctenophores and fish eggs, was observed,
although they were not abundant. In a similar study of a
lake in Finland, Rahkola et al. reported pump-related
damage of organisms ranging from 20 to 47% (Rahkola
et al., 1994). In contrast to this, the presence of live nauplii
larvae in our samples confirms that the damage to
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Table III: Summary of factorial anova of
Log-transformed data, testing retention of
> 60 µm phytoplankton groups by the two
sampling gears at different sampling
locations
DF
F
y = 1.0005x + 313.11
R2 = 1
P-value
Stations
7
39.11
0.000*
Groups
2
2103.37
0.000*
Gears
1
2.54
14
121.85
Stations Gears
7
2.19
0.100
Groups Gears
2
1.13
0.351
Stations Groups
3000000
Zoophy
Source
A NEW PLANKTON SAMPLER
Bacillariophyceae
2000000
1000000
0
0.133
0
0.000*
1000000
2000000
3000000
Net
Chlorophyceae
*Significant difference.
5000
Table IV: Summary of factorial anova of
Log-transformed data, testing retention of
> 200 µm zooplankton groups by the two
sampling gears at different sampling
locations
y = 0.8001x + 79.745
R2 = 0.5646
Zoophy
4000
3000
2000
1000
Source
DF
F
P-value
0
Stations
7
1513.83
0.000*
Groups
9
6358.24
0.000*
Gears
1
1.53
Stations Groups
0
1000
2000
3000
4000
5000
Net
0.221
63
407.78
Stations Gears
7
1.36
0.000*
0.236
Groups Gears
9
1.35
0.231
Cyanophyceae
50000
*Significant difference.
40000
Zoophy
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planktonic organisms, besides fish eggs and ctenophores,
is not significant. A high correlation was also observed for
different groups collected by the two methods (Figure 5
and 6). More research is currently being conducted on a
new design, with which planktonic forms could be collected before they pass through the pump, in order to
reduce the damage to certain groups of organisms. Such
a sampler would be suitable for collecting fish eggs,
Ctenophores and other organisms with delicate bodies.
y = 1.0187x - 600.87
R2 = 0.9945
30000
20000
10000
0
0
10000
20000
30000
40000
50000
Net
Fig. 5. Scatter plot of total counts (No. m–3) of major phytoplankton
groups collected by the two gears.
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Mastigophora
Zoophy
2000
0
4000
6000
8000
Net
Calanoida
Zoophy
2000
0
10000
Brander, K. M., Milligan, S. P. and Nicholas, J. H. (1993) Flume tank
experiments to estimate the volume filtered by high speed plankton
samplers and to access the effect of net clogging. J. Plank. Res., 15,
385–401.
15000
Net
Burney, C. (1984) A subsurface flexible plastic enclosure for the in situ
study of short-term microbiological and chemical dynamics. Limnol.
Oceanogr., 29, 1140–1144.
Ciliata
Cuzon Du Rest, R. P. (1963) Distribution of the zooplankton in the salt
marshes of southeastern Louisiana. Publ. Inst. Mar. Sci. Univ. Texas, 9,
132–155.
Zoophy
40000
y = 1.1113x - 349.32
R2 = 0.9967
Edmondson, W. T. and Winberg, G. G. (eds) (1971) A Manual of Methods
for the Assessment of Secondary Productivity in Freshwaters. Blackwell Science,
Oxford.
20000
Filion, J. M. (1991) Improving zooplankton samplers with simple electronics. Limnol. Oceanogr., 36, 204–210.
10000
George, D. G., Hurley, M. A. and Winstanley, B. (1984) A simple plankton splitter with a note on its reduced subsampling variance. Limnol.
Oceanogr., 29, 429–433.
0
0
10000
20000
30000
40000
Knoechel, R. and Campbell, C. E. (1992) A simple inexpensive device
for obtaining vertically integrated, quantitative samples of pelagic
zooplankton. Limnol. Oceanogr., 37, 675–680.
Net
Madden, C. J. and Day, J. W. (1992) An instrument system for highspeed mapping of chlorophyll a and physico-chemical variables in
surface waters. Estuaries, 15, 421–427.
Miscellaneous
McKinney, E. S. A., Gibson, C. E. and Stewart, B. M. (1997) Planktonic
diatoms in the north-west Irish sea : a study by automatic sampler. Proc.
R. Irish Acad., 97 B, 197–202.
100000
y = 1.0289x - 2563.6
R2 = 0.9918
80000
Zoophy

Barnett, A. M., Jahn, A. E., Sertig, P. D. and Watson, W. (1984) Distribution of icthyoplankton off San Onofre, California, and methods for
sampling very shallow coastal waters. Fish. Bull., 82, 97–111.
6000
4000
30000
‒
Barlow, J. P. (1955) Physical and biological processes determining the
distribution of zooplankton in a tidal estuary. Biol. Bull., 109,
211–225.
10000 y = 0.9706x - 16.58
R2 = 0.9991
8000
5000
PAGES
REFERENCES
12000
0

We thank Professor Torkel Gissel Nielsen, from the
Department of Marine Ecology and Microbiology,
National Environment Research Institute, Denmark, for
his critical reading of the manuscript and his valuable
comments. Thanks are due to Mr Abdul Latiff for his
assistance in the field. This research was supported by a
research grant (MBBP/MB1/BG1) made available to the
Tropical Marine Science Institute (National University of
Singapore) by the National Science and Technology
Board, Singapore.
4000
2000
NUMBER
AC K N O W L E D G E M E N T S
8000
y = 1.0603x + 48.768
R2 = 0.9911
6000
0

60000
40000
McQueen, D. J. and Yan, N. D. (1993) Metering filtration efficiency of
freshwater zooplankton hauls: reminders from the past. J. Plankton
Res., 15, 57–65.
20000
0
0
Rahkola, M., Karjalainen, J. and Viljanen, M. (1994) Evaluation of a
pumping system for sampling zooplankton. J. Plankton Res., 16,
905–910.
20000 40000 60000 80000 100000
Net
Fig. 6. Scatter plot of total counts (No.m–3) of major zooplankton
groups collected by the two gears.
Rey, J. R., Crossman, R. A., Kain, T. R. and Vose, F. E. (1987) Sampling
zooplankton in shallow marsh and estuarine habitats: gear description
and field tests. Estuaries, 10, 61–67.
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S. NAYAR, B. P. L. GOH AND L. M. CHOU
efficiency of plankton nets due to clogging under tow. J. Cons. Int.
Explor. Mer, 32, 232–248.
Setran, A. C. (1992) A new plankton trap for use in the collection of
rocky intertidal zooplankton. Limnol. Oceanogr., 37, 669–674.
Smith, P. E., Counts, R. C. and Clutter, R. I. (1968) Changes in filtering
A NEW PLANKTON SAMPLER
Received on August 27, 2001; accepted on June 6, 2002
