International Journal of Environment Science and Technology Center for Environment and Energy Research and Studies (CEERS) ISSN: 1735-1472 EISSN: 1735-2630 Vol. 4, Num. 1, 2007, pp. 43-48

International Journal of Enviornmental Science and Technology, Vol. 4, No. 1,Winter 2007, pp. 43-48

Comparative utilization of phosphorus from sedimentary and igneous phosphate rock by major biotic components of aquatic ecosystem

^*Chakrabarty, D.

Limnology Research Unit, Department of Zoology, Krishnagar Government College, Nadia, West Bengal, India
*Corresponding author, Email: debajyoti_chakrabarty@yahoo.co.in Tel./Fax: +91-9434148853

Received 30 April 2006;
Revised 28 November 2006
Accepted 5 December 2006
Available online 1 January 2007

Code Number: st07006

ABSTRACT: Two laboratory experiments were conducted to evaluate the amount of P utilization from two different types of sparingly soluble phosphate rock by aquatic biotic communities. The first type was Mussoorie Phosphate Rock or MPR (sedimentary in origin) and other was Purulia Phosphate Rock or PPR (igneous in origin). The two trials were with eight different treatment combinations. Among various treatments, fish and Chironomid larvae contributed to some extent in increasing the available sediment phosphate content which in turn increased the soluble reactive phosphate (SRP) of overlying water. Concentration of SRP of overlying water decreased in the treatment with zooplanktons. Depletion of SRP of overlying water due to uptake of orthophosphate by Chlorella was also observed. The sedimentary type phosphate rock proved to be more efficient in releasing phosphate than igneous one.

Key words: Phosphate rock, putilization, fish, chironomid larvae, chlorella, zooplanktons

Phosphorus is the most studied element in aquatic system primarily due to the fact that it is the most limiting factor for primaryproductivity in water bodies and is essential for living organisms and is not exchangeable with other elements in biological system. It is an important constituent of biological systems and is a macronutrient but its availability is often extremely low (Hupfer, et al., 2004). The effects of Phosphorus in nature are therefore profound. Usually phosphorus occurs in oxidized state, either as ions of inorganic orthophosphate or in organic compounds. Phosphorus in solution is normally considered to be orthophosphate (Soluble Reactive Phosphate or SRP) and is taken by different component members of an aquatic ecosystem. Boyd and Musig (1981) demonstrated that planktons in fish ponds absorbed an average of 41% of 0.30 mg/L addition of orthophosphate within 24 hours; however phosphorus that is not absorbed by planktons is rapidly absorbed mud (Hupfer, et al., 2004; Cade-menum, 2005). Pelagic invertebrates not only transform, they can also translocate the recycled phosphorus within the system (Shapiro, 1984). Phosphorus is undoubtedly a recognized nutrient for pond fertilization. Among various phosphatic fertilizers naturally occurring phosphate source (Mussoorie Phosphate Rock= MPR and Purulia Phosphate rock= PPR) can easily be used in fish farming ponds and has been amply proved to be an effective fertilizer in carp culture (Chakrabarty, 2006). The problem is its extremely low solubility in water. An attempt has been made here to quantify the difference of phosphorus utilization performances by various biotic members in laboratory condition from a marine sedimentary (MPR)and igneous (PPR) phosphate rock of Indian origin.

The chemical composition of MPR and PPR are as follows. The MPR is younger in geologic age than PPR (Table 1) and used as a cheap source of direct application fertilizer in fish farming ponds (Chakrabarty, 2006). In order to determine the extent of P-utilization from MPR and PPR by the major biotic components of the pond ecosystem, two laboratory experiments were carried out. The first experiment (trial-I) was carried out in 31 glass jars in the laboratory in presence of water and MPR all throughout, whereas the second one with water and PPR all throughout in the same manner with the previous one. For the first trial, all the 32 glass jars were filled with ground water and then subjected to following eight treatments in quadruplicate.

(i) Water – (A₁), (ii) Water + MPR – (B₁), (iii) Water + Soil – (C₁), (iv) Water + Soil + MPR – (D₁), (v) Water + Soil + MPR+ Chlorella sp. – (E₁), (vi) Water + Soil + MPR + Zooplankton -(F₁), (vii) Water + Soil +MPR+ Chironomid larvae – (G₁), (viii) Water + Soil + MPR + Fish – (H₁).

For the second trial, all the 32 glass jars were filled with ground water and then subjected to above eight treatments in quadruplicate in presence of PPR in the same manner with the previous one.

(i) Water – (A₂), (ii) Water + PPR – (B₂), (iii) Water + Soil – (C₂), (iv) Water + Soil + PPR – (D₂), (v) Water + Soil + PPR + Chlorella sp. – (E₂), (vi) Water + Soil + PPR + Zooplankton -(F₂), (vii) Water + Soil +PPR+ Chironomid larvae – (G₂), (viii) Water + Soil + PPR + Fish – (H₂).

Twenty gram of hundred mesh size ground MPR (trial-I) and PPR (trial-II) was placed in each of the experimental jars containing 2.5 l of ground water (pH 7.2). Chlorella sp. used in this experiment was procured from the laboratoryaxenic monoalgal culture (Chu– 10 medium). When the Chlorella concentration attained about 40 mg/Lof Chl- a; 10 mL of such concentrate was dispensed in each experimental jar of treatment combination of E₁ and E₂. Daphnia sp. was collected from the culture tank and concentrated to150 numbers and used in each jar. Chironomid larvae (average length 0.5 cm ± 0.025) were locally procured and then acclimatized in the laboratory prior to their use in experiment (F₁ and F₂). Thirty Chironomid larvae were used in each glass jar of treatment combination of G₁ and G₂. Advanced fry of Oreochromis mossambicus (4.20 g ± 0.25 g; 4.0 cm ± 0.60) were procured and acclimatized well in the laboratory prior to their use.

Three acclimatized fry was then placed in each glass jar in treatment combination of H₁ and H₂. Each set of glass jar was sacrificed at 0, 7 and 14 day for examination phosphorous contents of water, soil, Chlorella sp. All of them were carefully isolated, dried in hot air oven, grinded and total P content was measured using the method described by Jackson (1967). Chlorophyll-a (Chl- a) concentration of Chlorella sp. was analyzed following the method described by Vollenweider (1974). Orthophosphate concentration of water was also measured following standard methods (APHA, 2002). The results obtained in this study were statistically evaluated. Kruskal-Wallis one wayanalysis of variance by ranks was applied to find out the significance of difference among various treatments. Duncan’s Multiple Range Test (Duncan, 1955) was also performed to test the significance of difference between every possible pair of treatment of trial-I and trial-II. This experiments were carried out in Dept. of Zoology, University of Kalyani (August 1993) as well as in Krishnagar Government College (August 2004). The results expressed here as mean of two experiments.

Introduction of fish (H₁and H₂) and chironomid larvae (G₁ and G₂) resulted in considerable rise (Fig. 1 and 2) of SRP concentration of water (0.1825 and 0.1425 mg/L) and sediments (13.0-12.9 and11.7-11.5 mg kg/L) over other treatments (Figs. 3 and 4). Presence of zooplankton (F₁ and F₂) in the MPR and PPR treatment, on the other hand, caused decline of SRP level of water all throughout. For example, the amount of orthophosphate (SRP) observed on day 0 (0.165 mg/L) declined to0.0985 mg/Lin (F₁) on day 7 and finally to 0.065 mg/L on day 14.

In a same trend the amount of orthophosphate (SRP) observed on day 0 (0.125 mg/L) declinedto 0.0985 mg/L in (F₁) on day 7; and finally to0.065 mg/L on day 14 in the glass jars with F₂ combination. The result was also true for Chlorella sp. the amount of orthophosphate of water in the MPR treatment with Chlorella sp. (E₁) declined to 0.07 mg/L 0.05 on day 7 and further to 0.045 mg/L on day 14, from theinitial concentration of 0.165 Similar result was observed with the same treatment combination (F₂) with PPR (Fig. 2). Glass jarswithonlywater(A₁ andA₂) showed lowest SRP concentration (0.025 mg/L) of all, all throughout, whereas a stable and relatively high concentration of 0.155 to 0.1425 mg/Land 0.125 to 0.10 of SRP was maintained in the treatment combination of B₁ and B2. Kruskal-Wallis one way analysis of variance by ranks no significant difference (H=10.33; P>0.05) of treatment means in the beginning. Statistical analysis, however,showed significant difference (He” 14.16; P<0.05) among treatments on day 7 and 14. Six treatmentgroups such as G₁ and G₂; H₁and H₂; D₁ and D₂; E₁ and E₂, A₁ and A₂; C₁ and C₂ did not differ from each other on day 7 (Tables 2 and 3), whereas all the treatment groups expect C₁ and C₂; A₁ and A₂ showed significant difference on day 14 in both the trial. Significant difference was also found between H₁and H₂ as well as G₁ andG₂ in respect of concentration of water SRP and sediment available -P (ANOVA, P< 0.05) on 0, 7 and 14 days of observation. The treatment combination with MPR always showed higher dissolution of P from insoluble P than the combination with PPR. The amount of Chl-a concentration (Fig. 5) did not varied significantly (ANOVA, P> 0.05) between the two treatment combination (E₁ and E₂) throughout the experimental period. However, the total amount of phosphorusin chlorella (cell-P) was0.05±0.002 mg Jar^-1in day0 of both trial-I and- II. The amount increased to 0.08±0.002 mg/Jar(trial-I)) and to 0.078±0.003 mg/Jar (trial-II) onday 7 butdeclined to0.065±0.002 mg/Jar (trial-I)and to0.062±0.003 mg/Jar (trialII) inday 14.Thecell-P also did not varied significantly in any day between two series.

From the critical examination of the data it is revealed that fish and chironomid larvae contributed to some extent in increasing the available phosphate content of sediment which, in turn, increased the orthophosphate level of overlying water. This was due to their physical disturbance of the bottom sediments which induced the phosphorous release from sediment to the overlying water. The effect was perhaps brought about by the physical disturbance (Petr, 1977) and agitation of sediment enriched with phosphate rock. Similar results were obtained by Gabet, et al., (2003), Schauser, et al., (2003) and Sodergaard et al., (2003). Biomanupulation trials clearly revealed that fish and chironomid larvae had a profound influence in the release of phosphate from otherwise insignificantly soluble phosphate rock by bioturbation (Chakrabarty, 2006). There was an increase in biomass of Chlorella evident from the rise in Chl-a content. The depletion in orthophosphate level of water (0.165-0.07 mg l^-1) was due to the phosphorous uptake by the Chlorella. This was evident from the increase in cell-P of Chlorella over time. Phosphorous was found to be a growth regulatoryfactor of algae byAhlgren(1988). The critical examination of difference in liberation of available phosphorus from the two sparingly soluble phosphate sources indicated a significant difference (P<0.05) in treatment combination of H₁- H₂ and G₁ -G_{2 .}This was because of the lesser unit cell dimension (>.008 A⁰) of MPR than PPR (Table 1) as well as the higher CO₃:PO₄ mole ratio of (0.052) of MPR than PPR (0.013). As lesser and trial–II (E₂) unit cell dimension and higher CO₃:PO₄ mole ratio helps in natural dissolution of phosphate rock in natural condition (PPCL 1987). The utilization of phosphorus by chlorella indicated no significant difference between the treatment combinations of F₁and F_2. Possibly, the amount of SRP was sufficient in both the treatments for algal growth. The concentration of cell P was also similar between two series. The study clearly indicated that MPR is certainly better phosphate fertilizer than PPR in terms of releasing phosphorus in aquaculture. It also proved that sedimentary phosphate rock has better applicability than igneous type. X-ray diffraction studies identified MPR as carbonate apatite and PPR as fluorapatite. Carbonate apatite is more responsive to natural dissolution than fluorapatite (PPCL, 1987). However, both the fertilizer can be used as direct application fertilizer in fish farming ponds with bottom grazing fishes. These fertilizers are environment friendly and cheap for fish culturist.

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