Effect of different treatments on the periphyton quantity and quality in experimental fishponds

Abstract

Periphyton development and composition were studied in three different treatments: (i) two fishpond units of wetland-type wastewater treatment pond systems, (ii) two fishponds in combined intensive-extensive fish farming systems and (iii) three traditional polyculture fishponds. Results showed that amounts of periphyton developed in traditional polyculture fishponds (iii) were different compared to the other treatments (i and ii), where the main function of ponds was stated wastewater treatment. Negative correlation was also observable between water quality parameters and periphyton production. The lower trophity, halobity and saprobity level of ponds indicated higher amount of periphyton. The dry matter content of periphyton was significantly higher in the samples, which were developed in traditional polyculture fishponds (2.84±3.02 g m -2 day -1, whereby the ash content in dry matter 74%), than samples taken from (i) (1.60±2.32 g m -2 day -1, 61%) and (ii) fishponds (0.65±0.45 g m -2 day -1, 81%).

Full text

Abstract—Periphyton development and composition were
studied in three different treatments: (i) two fishpond units of
wetland-type wastewater treatment pond systems, (ii) two fishponds
in combined intensive-extensive fish farming systems and (iii) three
traditional polyculture fishponds. Results showed that amounts of
periphyton developed in traditional polyculture fishponds (iii) were
different compared to the other treatments (i and ii), where the main
function of ponds was stated wastewater treatment. Negative
correlation was also observable between water quality parameters
and periphyton production. The lower trophity, halobity and
saprobity level of ponds indicated higher amount of periphyton. The
dry matter content of periphyton was significantly higher in the
samples, which were developed in traditional polyculture fishponds
(2.84±3.02 g m
−2
day
-1
, whereby the ash content in dry matter 74%),
than samples taken from (i) (1.60±2.32 g m
-2
day
-1
, 61%) and (ii)
fishponds (0.65±0.45 g m
-2
day
-1
, 81%).
Keywords—
Artificial substrate, fishpond, periphyton, water
quality
I. I
NTRODUCTION
ERIPHYTON is the complex of organisms found on
submerged substrates that are of materials different from
those of the water bottom and clearly distinguishable from
them [1]. Periphyton is composed of algae, fungi, bacteria,
and protozoa associated with substrates in aquatic habitats.
Periphyton is often the dominant contributor to nutrient
cycling in aquatic ecosystems and it is an excellent indicator
for changes occurring in the aquatic environment [2]. The
periphyton quantity and quality depends on abiotic and biotic
factors (nutrients, light intensity and quality, temperature,
water level, as well as the substrate type and the grazing
activity of the fish and invertebrates). Nutrient availability is
an important regulating factor for bacterial and algal
production and growth. The bacteria can take up algal
exudates and the algae may benefit from the regeneration of
nutrients performed by the bacteria. Bacterial activity is high
T. Kosáros is with the Research Institute for Fisheries, Aquaculture and
Irrigation, Szarvas, Hungary (phone: +36-66-515-310; fax: +36-66-312-142;
e-mail: kosarost@haki.hu).
D. Gál is with the Research Institute for Fisheries, Aquaculture and
Irrigation, Szarvas, Hungary (e-mail: gald@haki.hu).
F. Pekár is with the Research Institute for Fisheries, Aquaculture and
Irrigation, Szarvas, Hungary (e-mail: pekarf@haki.hu).
Gy. Lakatos is with the University of Debrecen, Department of Applied
Ecology, Debrecen, Hungary (e-mail: lakgyu@delfin.klte.hu).
Financial support for the research work was provided by the SustainAqua
EC-project (COLL-CT-2006-030384).
within periphyton [3], [4]. The autotrophic organisms of
periphyton produce organic material and oxygen by using
light energy and absorbing nutrients. The organic material
produced in that way can provide valuable nutrition for the
periphytic zoo-organizms and other heterotrophic
communities in the water. The heterotrophic organisms also
use drifting, produced, settling or settled organic material in
their metabolic processes [5].
The use of periphyton in aquaculture improves both the
water quality and aquatic production. The idea is originally
derived from traditional fishing methods from tropical
countries, such as the „acadjas” of Africa [6], the “samarahs”
of Cambodia [7] and the “katha” fisheries of Bangladesh [8],
where tree branches are placed in shallow open waters to
attract fish and enhance productivity.
In our study, the periphyton appearing on artificial
substrates in different types of experimental fishponds were
examined. Since traditional periphyton based aquaculture does
not exist yet in Hungary, detailed knowledge on the
quantitative and qualitative changes of the periphyton may
give possibilities to increase fish yield and improve water
quality in fishponds, even under the temperate climate.
II. M
ATERIALS AND METHODS
The experiment was carried out in seven experimental
fishponds at the Research Institute for Fisheries, Aquaculture
and Irrigation (HAKI), Szarvas, Hungary in 2007.
A. Description of studied sites
W1 (0.25 ha) and W2 (0.12 ha) fishponds are parts of two
wetland-type pond systems constructed for experimental
wastewater treatment. These systems are comprised of four
serially-connected ponds, two earthen fishponds (first and
second units) and two macrophyte-covered earthen ponds
(third and fourth units). The effluent water from an intensive
African catfish farm was canalled into the first ponds. Our
studies were carried out in the second pond units stocked with
silver carp (Hypophthalmichthys molitrix V.) and common
carp (Cyprinus carpio L.) at an initial stocking biomass of
800-1000 kg ha
-1
.
IE1 and IE2 fishponds (0.03 ha) were the extensive units of
two combined intensive-extensive systems, where one cage
per system was operated as the intensive unit (mean water
depth 1 m). In the intensive units European catfish (Silurus
glanis L.) were cultured and fed with pellet – initial stocking
Effect of Different Treatments on the Periphyton
Quantity and Quality in Experimental Fishponds
T. Kosáros, D. Gál, F. Pekár and Gy. Lakatos
P
World Academy of Science, Engineering and Technology 40 2010
363

biomass was 90 kg (10 m
3
) –, whereas in the extensive units
common carp (Cyprinus carpio L.) and Nile tilapia
(Oreochromis niloticus L.) were raised without any artificial
feeding – initial stocking biomass was 30 kg. The periphyton
appearance in the extensive units was investigated.
FP1, FP2 and FP3 were traditional polyculture fishponds
with a surface area of about 0.15 ha. Common carp (Cyprinus
carpio L.), hybrids of silver carp and bighead carp
(Hypophthalmichthys molitrix V. x Aristichthys nobilis R.),
grass carp (Ctenopharyngodon idella V.) and European
catfish (Silurus glanis L.) were stocked in polyculture in the
proportion of 67:22:9:2%, respectively.
B. Water quality measurements
Water quality was checked three times a week at the outlets
of the ponds for water temperature (TEMP), conductivity
(Cond), pH and dissolved oxygen concentrations (DO) with
portable meters (WTW, model Oxi 315i; YSI 556 Multi Probe
System and Horiba U-10). The whole water column was
sampled for water chemical measurements at periphyton
sampling (biweekly in W and IE ponds, and every second
months in FP ponds) of the ponds, and the samples were
analysed for nutrient concentrations − ammonium-nitrogen
(NH
4
-N), total organic and inorganic nitrogen (KN, TIN),
total nitrogen (TN) and soluble reactive phosphorus (PO
4
-P),
total phosphorous (TP), volatilised suspended solids (VSS),
total suspended solids (TSS), biochemical oxygen demand
(BOD
5
), chemical oxygen demand (COD
Cr
) according to
Hungarian Standard Methods (MSZ). The chlorophyll-a (Chl-
a) and pheophytin (Pheop) concentrations were determined by
colorimetric analysis using a spectrophotometer after
extraction with 90% ethanol [9].
C. Periphyton measurements
The periphyton samples were collected from epyphalotical
habitats (plastic pipe substrates – diameter 1.8 cm – placed
vertically in the ponds). The pipes were enclosed in small
cages which were used to avoid periphyton consumption by
fish. Samples were taken between June and November in 2007
periodically. The first sampling was done 14 days after
submersion. From each pond, two pipes were selected per
sampling and sub-samples of periphyton were taken at two
depths (20 and 50 cm below the water surface) per pipe. The
four sub-samples were mixed into two single samples (20 cm,
50 cm) which were analysed separately. Substrates were
replaced after collecting the samples to allow further
development and periodical sampling of periphyton.
The periphytic material was scraped with a scalpel from a
known surface area − 2x113 cm
2
+ 2x170 cm
2
− (wet mass).
These samples were dried at 105
°
C until constant weight
(24 h), and kept in a desiccator until weighed dry matter
content (DM). Ash-free dry matter (AFDM) was determined
after the samples ashed at 500
o
C for 4 hours. Chl-a
concentration was determined by colorimetric analysis using a
spectrophotometer after extraction with methanol [9].
D. Data analysis
The data were analysed by SPSS using significant
difference comparison (T-test) to determine the differences
between treatments at 0.05 level of probability. The
correlations among the water quality parameters and
periphyton quantity parameters were determined using
Pearson correlation.
III. R
ESULTS AND DISCUSSION
A. Water quality parameters
Comparing the measured water quality parameters of
different ponds no significant differences were found (except
FP1 and FP2 conductivity t=3.55, p=0.024). Water quality
parameters of treatments are shown in Table I.
Three water quality parameters were used to classify the
treatments (Table II) [9]. W and IE treatments were similar
according to trophity and saprobity levels. Water condition
(conductivity) was indicating high degree of halobity in W.
According to the grades of trophity, intensity of primary
production was high in these treatments. Water treatment
TABLE I
W
ATER QUALITY PARAMETERS IN THE TREATMENTS
Parameters W (n=22) IE (n=16) FP (n=9)
Cond µS cm
-1
1014±
135
412±
17
394±
20
BOD
5
mg l
-1
19.0±
11.1
27.3±
12.1
11.3±
4.8
COD mg l
-1
100±
43
80.0±
37.9
52.4±
21.9
NH
4
-N mg l
-1
4.57±
3.58
0.209±
0.124
0.058±
0.040
TIN mg l
-1
7.55±
4.09
0.702±
0.504
0.096±
0.058
KN mg l
-1
3.26±
1.80
3.40±
1.05
2.50±
0.92
TN mg l
-1
10.8±
3.8
4.10±
1.37
2.60±
0.89
PO
4
-P mg l
-1
1.25±
0.59
0.120±
0.070
0.068±
0.050
TP mg l
-1
1.79±
0.66
0.432±
0.207
0.247±
0.089
Chl-a ug l
-1
389±
340
595±
391
112±
44
Pheop ug l
-1
575±
452
819±
457
165±
46
DO mg l
-1
5.61±
2.34
a
8.60±
1.07
b
6.19±
2.34
c
TEMP °C
20.1±
6.78
a
21.8±
3.95
b
17.5±
6.12
c
pH -
8.60±
0.93
a
8.78±
0.34
b
n.d.
Values are means ± S.D. − n.d.: no data,
a
(n=16),
b
(n=15),
c
(n=12)
World Academy of Science, Engineering and Technology 40 2010
364

function of W and IE was shown by saprobity level that
indicated the high organic content of inflow water and mass
development of bacteria that were involved in decomposition
processes. FP was found eu-politrophity and alpha-
mesosaprobic according to this classification.
The treatments were also separated by significant
differences of water chemical parameters (Table III). The
lowest concentration of different water chemical parameters
was found in the FP except DO and TSS concentrations.
B. Periphyton quantity and quality
The average periphyton composition on each plastic pipes
was calculated. Substrates, submersion time and depth were
the same in the treatments. Comparing the measured
parameters of periphyton production, there were no significant
differences (p>0.05) between W1 − W2, IE1 − IE2, and FP1 −
FP2 − FP3 ponds similarly to the water chemical parameters.
Thus, the fishponds can be characterised by the amount of
periphyton similarly to the water chemical parameters. The
DM of periphyton was significantly higher in the samples,
which were developed in FP (2.84±3.02 g m
-2
day
-1
, whereby
the ash matter was 2.11±2.18 g m
-2
day
-1
) than samples were
taken from W and IE (Table IV, Fig. 1). Results showed that
amounts of periphyton developed in traditional polyculture
fishponds were different compared to the other treatments,
where the main function of ponds were wastewater treatment.
Maximal periphyton biomass could be observed where the
combination of light and nutrient are optimal [10]. The
maximums of periphyton dry matter development were found
in IE (0.654
g m
-2
day
-1
at 18.06.2007), in FP
(0.327 g m
−2
day
−1
at 28.08.2007) and in W (0.114 g m
-2
day
-1
at 02.07.2007) in the summer months.
Higher ash ratio was observed in IE than in the other
treatments (ash content in dry matter IE=81%, FP=74%,
W=61%). The high amount of inorganic fraction of
periphyton was caused by the using of paddle aerators for
water-circulation and inorganic particles from the water
column increased the ash content.
Mean periphyton Chl-a pigment varied between
0.061±0.080 mg m
-2
day
-1
and 0.143±0.168 mg m
-2
day
-1
.
Relatively more Chl-a was present in W and IE than in FP.
Significant difference was found only between W and FP
regarding the dry matter of periphyton (n=16, n=10, t= -2.889,
p=0.008) and the quantity of ash (t= -3.119, p=0.005).
0
1
2
3
4
5
WIEFP
DM (gm
-2
day
-1
)
AFDM
Ash
Fig. 1 Mean (+SD) periphyton dry matter in different treatments
TABLE II
C
LASSIFICATION OF TREATMENTS
Treatments Feeding
Halobity
(Con)
Trophity
(Chl-a)
Saprobity
(COD
Cr
)
W no
oligo-
mesohalobity
politrophity
alpha-meso-
polisaprobic
IE no
beta-alpha
oligohalobity
politrophity
alpha-meso-
polisaprobic
FP yes
beta-alpha
oligohalobity
eu-
politrophity
alpha-
mesosaprobic
TABLE III
S
IGNIFICANT DIFFERENCE BETWEEN WATER QUALITY
PARAMETERS IN THE DIFFERENT TREATMENTS
Parameters W-IE W-FP IE-FP
Cond
t=17.69
p<0.001
t=13.58
p<0.001
t=2.263
p=0.033
BOD
5
t=-2.187
p=0.035
−
t=3.743
p=0.001
COD
Cr
−
t=3.165
p=0.004
−
TIN
t=6.636
p<0.001
t=5.412
p<0.001
t=3.560
p=0.002
KN − −
t=2.140
p=0.043
TN
t=6.811
p<0.001
t=6.427
p<0.001
t=2.948
p=0.007
PO
4
-P
t=7.586
p<0.001
t=5.938
p<0.001
−
TP
t=7.883
p<0.001
t=6.878
p<0.001
t=2.525
p=0.019
Chl-a − −
t=2.971
p=0.008
Pheop −
t=2.192
p=0.038
t=3.447
p=0.003
DO
t=-4.526
p<0.001
−
t=3.566
p=0.001
TABLE IV
C
OMPARISON OF PERIPHYTON IN DIFFERENT TREATMENTS
Parameters W (n=16) IE (n=16) FP (n=10)
DM g m
-2
day
-1
0.649±
0.452
1.600±
2.32
2.836±
3.02
Chl-a mg m
-2
day
-1
0.143±
0.168
0.110±
0.094
0.061±
0.080
Ash g m
-2
day
-1
0.398±
0.344
1.290±
2.09
2.110±
2.18
AFDM g m
-2
day
-1
0.251±
0.164
0.310±
0.265
0.726±
0.954
World Academy of Science, Engineering and Technology 40 2010
365

C. Influence of water chemical parameters at different
sampling time
The periphyton dry matter and related water chemical
parameters showed significant correlation in IE and W
treatments. In every case the correlation was negative between
the water chemical parameters and the periphyton dry matter
(Pearson correlation, p<0.05, n=16, W−BOD
5
: -0.583,
IE−COD: -0.577, KN: -0.621, TN: -0.581, TP: -0.530, Chl-a:
−0.509, Pheop: -0.539).
The significant difference of dry matter and quantity of ash
in the different treatments was tested with two samples t-
probe. Significant difference between the treatments at the
same sampling date was observed in 50, 50 and 33% of W-IE,
W-FP and IE-FP comparisons. Results of two sampling dates
are shown here only for detailed discussion. In Table V is
showed the third sampling date, where the higher periphyton
production was found in W than in IE (DM:
1.033±0.009 g m
−2
day
-1
vs. 0.726±0.063 g m
-2
day
-1
). The
values of conductivity and the NH
4
-N concentration were
showed significant difference and negative correlation.
The eighth sampling dates are showed in Table VI. Higher
periphyton production was found in FP than in IE ponds (DM:
5.49±1.00 g m
-2
day
-1
vs. 0.745±0.490 g m
-2
day
-1
). Significant
difference was showed to the assay in seven water parameters
(BOD
5,
COD
Cr
, NH
4
-N, TIN, TN, PO
4
-P, TP). In these cases,
the negative correlations were also observable between water
quality parameters and periphyton production. The lower
trophity, halobity and saprobity level indicated higher amount
of periphyton. These results were close to the third sampling
date.
R
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TABLE V
S
IGNIFICANT DIFFERENCE BETWEEN THE TREATMENTS AT THE THIRD
SAMPLING
(16.07.2007)
Parameters W IE Sig. diff. (n=2)
DM g m
-2
day
-1
1.033±
0.009
0.726±
0.063
t=6.801
p=0.021
Ash g m
-2
day
-1
0.767±
0.0389
0.057±
0.0213
t=6.280
p=0.024
Cond µS cm
-1
1081±
33.9
406±
1.41
t=28.10
p=0.001
NH
4
-N mg l
-1
0.0525±
0.07
0.290±
0.0233
t=-4.561
p=0.045
TABLE VI
S
IGNIFICANT DIFFERENCE BETWEEN THE TREATMENTS AT THE
EIGHTH SAMPLING
(24.09.2007)
Parameters IE FP
Sig. diff.
(n=2)
DM g m
-2
day
-1
0.745±
0.490
5.49±
1.00
t=-6.00
p=0.027
Ash g m
-2
day
-1
0.448±
0.348
4.48±
1.23
t=-4.43
p=0.047
BOD
5
mg l
-1
22.5±
3.53
5.66±
1.15
t=8.20
p=0.004
COD
Cr
mg l
-1
97.0±
21.2
50.3±
2.31
t=4.12
p=0.026
NH
4
-N mg l
-1
0.294±
0.046
0.034±
0.011
t=10.1
p=0.002
TIN mg l
-1
0.884±
0.365
0.061±
0.037
t=4.23
p=0.024
TN mg l
-1
4.35±
0.156
3.71±
0.090
t=6.04,
p=0.009
PO
4
-P mg l
-1
0.111±
0.007
0.010±
0.003
t=23.9
p=0.000
TP mg l
-1
0.391±
0.088
0.177±
0.029
t=4.15
p=0.025
World Academy of Science, Engineering and Technology 40 2010
366