COMMUNITY METABOLISM IN UNDRAINABLE RURAL FISH PONDS

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Community Metabolism in Tropical Undrainable Rural Fish Ponds

J. Olah, V.R.P. Sinha, S. Ayyappan, C.S. Purushothaman
and S. Radheyshayam

Freshwater Aquaculture Research and Training Centre Dhauli, Orissa, India,
and Fisheries Research Institute, Szarvas, Hungary

Abstract

The process of community metabolism including primary production and community respiration in eighteen undrainable rural fish ponds in India was quantified using the diurnal oxygen curve method. A considerable portion of the gross primary production that was in the moderate ranges, was consumed for the community respiration. Negative, and low positive values of net primary production indicated the significance of the allochthonous supply in these organic enriched systems. The low values of sediment respiration signified the reduced condition of stagnating sediment acting as energy trap.

1. Introduction

During the last decade, fish culture activity has been extended primarily to monsoon-fed undrainable rural ponds in Orissa, India, initiated by the Freshwater Aquaculture Research and Training Centre, Dhauli. The culture practised in these fish ponds corresponds to the management level of organic fertilization technology. The fish production in these village ponds is based mainly on the utilization of the natural fish food resources maintained and enhanced by the introduction of organic carbon. A study of the community metabolism of these ponds was made in which the basic production processes were measured using the diurnal oxygen curve analysis.

2. Methods

The few studies on the primary production of the Indian freshwaters have been carried out by the classical light and dark bottle method, measuring the changes of oxygen concentration in the bottles after long incubation periods (Sreenivasan, 1963, 1976; Vijayaraghavan, 1971). In these hypertrophic waters, the application of this method often results in a significant underestimation of the planktonic primary production as well as community respiration (Kalbe, 1972; Oláh et al., 1978). Primary production and respiration of the macrophyte and benthic communities are also not included in this measurement. Hence, a method for the analysis of the diurnal oxygen curve was employed, measuring the in situ levels by a Beckman Monitor II system oxygen meter. As significant variations were noticed in the size, area, water depth and organic loads of these undrainable ponds, a simplified version of the diel curve analysis was used in order to monitor the representative number of ponds. Diurnal variations of dissolved oxygen were monitored with three measuring points. The McConnel (1962) equation was used to calculate the primary production and community respiration. The only shortcoming in the analysis of the diuiral oxygen curve is that the diffusion rate at the air-water interface is not incorporated in the calculations. However, this error on estimations is minimal as there is very little tuibulence in these ponds due to high embankments and thick vegetations around.

Published in Int. Revue ges. Hydrobiol. Vol. 71 (June 1986), pp. 807–812.

To determine the magnitude of the sediment oxygen consumption in the whole community respiration, intact sediment cores were collected manually in glass tubes (20 cm length; 3.5 cm dia), with at least 10 cm of the overlying bottom water remaining undisturbed. After having measured the initial oxygen concentrations in the water above the sediment, the tubes were incubated under in situ conditions and in dark for 2 hours. The final oxygen levels were measured with electrode of Monitor II Beckman model. The production and respiration values were calculated as g C m^-2 d^-1 using a conversion factor of 0.375 for the oxygen values measured.

3. Results

The community metabolism in IS and sediment respiration in 10 undrainable rural ponds were measured in February 1985. Some of the rural ponds monitored are upto 100 years old, with deep, soft sediment rich in organic matter (Table 1). Most of them, however, are new or have been reconstructed within the last 2 to 8 years. Majority of the ponds have a water surface area below 1 ha, with an average being less than 1000 m².

Table 1. Main characteristics of undrainable rural fish ponds in Orissa, India

The largest pond, number 4, however, has an area of 2.13 ha. The water depth varies from as low as 48 cm to 225 cm, the average being around 100 cm. The stocking structure and density varied from 2800 to 7000 ha^-1, with the three Indian major carps, catla Catla catla Hamilton, rohu Labco rohita HAMILTON, and mrigal Cirrhinus mrigala (HAMILTON), as well as the common carp. In some ponds, it was supplemented with silver carp. These small ponds serve many purposes in the life of the villages and the organic enrichment is also supported by these activities. Thus, the magnitude of organic fertilization related to the size of human population and animals associated with the particular ponds. The human population ranged between 10 and 1250 ha^-1. They are the point-source of organic enrichment during dry seasons and a diffuse source during the monsoons.

The gross primary production in the ponds ranged from 1.76 to 4.79 g C m^-2 d^-1, except in pond 1 where it was extremely high, being 12.3 g C m^-2 d^-1 (Table 2). The average gross primary production worked out to 3.73 g C m^-2 d^-1. No significant correlation between the primary production levels and the main characteristics of these ponds could be discerned. However, production levels were high in old ponds with moderate organic load (pond 1) or moderately old ponds with high organic load (pond 10). The production was generally low in young shallow ponds with moderate organic load (pond 3) or moderately old ponds with low organic load (pond 9). Production levels were observed to reach higher levels even in young ponds receiving scant organic load through human population and animal livestock, as in pond 12, largely because of the additional organic manuring and supplementary feeding.

Table 2. Community metabolism in undrainable rural fish ponds, g C m^-2 d^-1

The magnitude of total community respiration was close to the gross production values, being in the range of 1.66 to 4.69 g C m^-2 d^-1, except a high value of 11.34 g C m^-2 d^-1 in pond 1 (Table 2). The average community respiration value was 3.60 g C m^-2 d^-1. The benthic community respiration ranged widely, amounting to 5.3 to 30.0 per cent of the total community respiration. The quantum of respiration at the sediment-water interface as a percentage of the primary production was lower in the more productive ponds, compared to the less productive ones.

The net primary production as a final result of the daily production and consumption processes was negative in seven ponds and positive in the other eleven.

4. Discussion

The perennial undrainable ponds in tropical monsoon regions with longer insolation are ideal fish culture systems. Multipurpose use of these ecosystems by the villagers facilitates continuous organic enrichment, and hence the fish culture practised in such systems depends largely on the management level of organic fertilization where the bacterial-detrital food chain dominates besides the algal food chain in the production process.

The community metabolism in this type of fish rearing ecosystem is usually represented by negative net primary production values. In the present study, however, only seven ponds out of eighteen were characterised by negative net primary production. Although the picture might change on an annual basis, i.e., more ponds may show negative values, the present results represent the average conditions of the production processes in these village ponds. In case of positive net primary production, the surplus between the organic carbon input through daily primary production together with average daily allochthonous organic enrichment and the output quantified as total community respiration, appears in the carbon accumulation sedimented at the bottom. The difference between the larger input due to organic enrichment and the smaller output with sediment organic carbon forms the actual values of the daily net primary production.

The main feature of these undrainable ponds is the large amount of organic matter. For instance, pond 1 which is about 100 years old, has a sediment depth of 144 cm with 3.11 % organic carbon content, 12 dm^-3 m^-2 of gas accumulated as well as a significant amount of reduced substances. Sediment gas was collected with a tunneltrap device (OLÁH et al., in prep.). In these shallow ponds, organic accumulation creates anaerobic conditions at the sediment-water interface due to low turbulence through wind and convection currents. In the 10 ponds surveyed, the magnitude of the sediment respiration or benthic community respiration was generally low. In most cases, it was smaller than it would correspond to Hargrave's relation describing the percentage of the sediment respiration to the primary production as a function of water depth (HARGRAVE, 1973). This may also be due to the limited transport mechanism at the sediment-water interface.

The primary production was moderate in all the fish ponds surveyed, except pond 1. Studies on the seasonal pattern of the primary production in Indian waters have shown that February is a period with average values (VIJAYARAGHAVAN, 1971; Ayyappan, 1977) and hence, the values measured may represent the annual average situation in these village ponds. Similar primary production levels have been measured in other Indian freshwaters (SREENIVASAN, 1972; AYYAPPAN, 1977), but with the light and dark bottle method, whose underestimation has been established (KALBE, 1972; Oláh et al., 1978). Even with the organic enrichment in these ponds by the surrounding human and animal populations which is considerable though not precisely quantified, the primary production is in moderate range (Table 3). Evidently, the sediment layers rich in organic matter are acting here as energy traps due to their anaerobic and reduced conditions, as also proved by high values of their chemical respiration.

Table 3. Ranges of community metabolism in freshwater ecosystems, g C m^-2 d^-1

5. Summary

1. The quantification of community metabolism including primary production and community respiration of eighteen undrainable rural fish ponds using the diurnal oxygen curve method has been attempted for the first time. Earlier attempts have used the light and dark bottle method, that has been proved to underestimate the production levels.

2. The gross primary production values in terms of g C m^-2 d^-1 varied from 1.76 to 4.79, except in pond 1 with a high value of 12.30. Considering the method employed, they provided the first real estimates of the primary production in these ponds that was in the moderate range.

3. The total community respiration values were close to the production values, being 1.66 to 4.69 g C m^-2 d^-1, with an exception of 11.34 g C m^-2 d^-1 in pond 1. The sediment or the benthic community respiration values measured in ten ponds ranged from 0.15 to 1.27 g C m^-2 d^-1.

4. While low values of positive net primary production of 0.03–1.35 g C m^-2 d^-1 were observed in 11 ponds, negative values of -1.29 to -0.13 g C m^-2 d^-1 were recorded in the remaining seven. This indicates the significance of allochthonous organic matter and a lot of other factors operating in these systems enriched organically.

5. Though similar values of primary production have been reported in other Indian freshwaters as in the present case, the former have generally underestimated the production by the light and dark bottle method. The present values appear to be the real estimates, being in the moderate range of productivity.

6. References

Ayyappan, S., 1977: Observations on plankton with reference to hydrography of Ramasudra tank. Dakshina Kannada.-M.F.Se. dissertation, submitted to the University of Agricultural Sciences, Bangalore, 198 pp.

Baumgardner, R.K., 1966: Oxygen belance in a stream receiving domestic and oil refinery effluents.-Ph. D.Thesis. Oklahoma State University, 70 pp.

Cole, J., and S. G. Fisher, 1978: Annual metabolism of a temporary pond ecosystem.-American Midland Naturalist 100: 15–22.

Duffer, W.R., and T. C. Dorris, 1966: Oxygen balance in a southern great plains stream in Southeastern Oklahoma.-Limnol. Oceanogr., 11:141–151.

Fontaine III, T. D., and K.C. Ewel, 1981: Metabolism of a Florida lake ecosystem.-Limnol. Oceanogr., 26: 754–763.

Hannan, H.H., 1967: Macrophyte standing crop and metabolism in a constant temperate river-Ph. D. Thesis. Oklahoma State University, 47 pp.

Hargrave, B.T., 1973: Coupling carbon flow through some pelagic and benthic communities.-J. Fish. Res. Bd. Can. 30: 1317–1326.

Kalbe, L., 1972: Sauerstoff und Primärproduktion in hypertrophen Flachseen des Havelgebietes.-Int. Rev. ges. Hydrobiol., 57: 825–862.

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McConnel, W.J., 1962: Productivity relations in carboy microcosm.-Limnol. Oceanogr. 7: 335–343.

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Oláh, J., A. Zsigri, and Á. V. Kintzly, 1978: Primary production estimations in fish ponds by the mathematical evaluation of daily oxygen curves.-Aquacultura Hungarica 1: 3–14.

Sreenivasan, A., 1963: Primary production in three upland lakes of Madras State, India.- Curr. Sci. 32: 130–131.

Sreenivasan, A., 1972: Energy transformations through primary productivity and fish production in some tropical freshwater impoundments and ponds. pp. 505–514 in Z. Kajak and A. Hillbricht-Ilkowska (eds): Productivity problems in freshwaters.-Polish Scientific Publishers, Warsaw, Poland.

Sreenivasan, A., 1976: Limnological studies of and primary production in temple pond ecosystems.-Hydrobiologia 48: 117–123.

Vijayaraghavan, S., 1971: Seasonal variations in primary productivity in three tropical ponds.-Hydrobiologia 38: 395–408.

Dr. J. Oláh
Fisheries Research Institute
H-5541 Szarvas, Hungary