Effects of Temperature and Salinity on the Growth of Microalga Tetraselmis Sp. and Tilapia oreochromis Sp. in Culture Pond, Tamil Nadu, India

Abstract

The Aquaculture industry development of the fish culture has been happened by the lack of virulent and saline tolerable fish strain in marine food sector. This paper reports the recent development of aquaculture species of tilapia fish. The natural climatic changes were increased the water bodies temperature and salinity in aquaculture industry. This research examined saline tolerable micro algae (Tetraselmis sp.) and tilapia (Oreochromis sp.) fish stain. Microalgae and tilapia can survive the range of temperature 22.3 to 36.4°C, salinity 45 to 92.5%. pH 8.3 to 9. During 2013 and 2014 years the physiochemical and biological changes were hardly occurred, even though the density of microalgae was not much affected , the maximum density 368000 cells/ml , it’s declined up to 750 cells/ml. Tilapia fish survived optimum level of temperature and salinity , but unable to survive above 90%of salinity. The range of tilapia size 7.6 cm to 25.6 cm and weight 80 gram to 250 grams. All this results show that the Tetraselmis sp. and tilapia fish strain could be culture hyper saline water and improve the aquaculture product against of climatic changes.

Keywords

Temperature, Salinity, Tetraselmis spices, Oreochromis spices, Climatic change.

Introduction

The world water environment contains various kinds of living organisms with various ecosystems. The plankton plays a significant role in aquatic environment. These organisms provide energy to higher trophic consumers and their tissue development. In recent years, raising climatic changes affecting living organisms via food chain and web. Microalgae play an important role in the water environment especially for marine ecosystem as a primary producer which contribute to maintain the secondary production and eventually to enhance the fishery production. Some species of microalgae are used as live feed for finfish, shellfish and other invertebrates in aquaculture farms [1-3]. Some species are also used for industrial purpose to eliminate organic matters in waste disposal through gas exchange [4]. The physiology of microalgae is affected by physico-chemical factors such as water temperature, salinity, pH, light intensity and nutrient concentration.

Tilapia has been referred to as the ‘aquatic chicken’. An Oreochromis sp. could be easily identified by dark bands of strips found on their body which is most prominent in mature forms. Nile tilapia Oreochromis sp. (Family: Cichlidae) having vital importance to fisheries. Tilapias are one of the most economically important groups of aquaculture species because they serve as major sources of protein in most countries. They are versatile species of fish, which is found in almost all type of tropical aquaculture systems ranging from traditional to highly intensive production systems. They withstand wide range of environmental conditions and perform well regardless of the water salinity and temperatures to which they are exposed to some species are even able to thrive and breed in full strength seawater. Among the tilapia species, the Nile tilapia, Oreochromis sp. is the preferred species for culture as this fish dominates production in freshwater and brackishwater ponds and cages [5]. However, it has low tolerance to high salinity levels.

On the other hand, the Mozambique tilapia, Oreochromis mossambicus is a euryhaline species and is one of the best studied tilapias in terms of elucidating the mechanisms involved in euryhalinity among fishes [6]. One of the constraints in the culture of tilapias in high saline environments is its sensitivity to handling and susceptibility to secondary infections [7]. Hence the tilapia living in natural environment like ponds, lakes, pools etc. is depending natural herbs for that feeds. The natural climatic changes are affecting growth of micro algae and fishes, especially traditional fish of Tilapia. Because of these problems, there have been intensive research efforts made on improving the salinity tolerance of tilapias either through modifications in the culture techniques or stock improvement. The culture of tilapias in saline waters is well-documented based on numerous research studies done in the past years. The limited space for freshwater aquaculture and pressures on providing the food demands of the population, tilapias are now being cultured in brackishwater ponds and even in marine cages. This scenario will further intensify in the years to come in order to cope with food requirements of the increasing human population. This article focuses on the effect of temperature and salinity on the growth of cultured microalgae and tilapia fish in pond system.

Material and Methods

Micro Algae Culture

Microalga Tetraselmis sp. collected from the Bay of Bengal, Tuticorin, Tamil Nadu and the species were isolated and maintained at the laboratory in the cell density between 5 and 10 million cells/ml using Conway’s culture medium [8] for maintaining indoor culture of Tetraselmis sp. while commercial grades of fertilizers (Urea, NPK, silicate) were used for outdoor culture of Tetraselmis sp. where cell density reached 0.5-3 million cells/ml. Micro algae were maintained at optimum level of physicochemical parameters. The physico-chemical parameters were analysed according to Cho [9].

Tilapia Culture

Nile tilapia (Oreochromis sp.) seeds (2500 numbers and initial size of 3 to 5 cm) were collected from Tuticorin back water and released in to 1500 m3 earthen pond. The temperature and salinity were maintained in the range of 25-33°C and 33-50 ppt respectively. Microalgae and tilapia were maintained in the same culture pond and determined the effect of temperature and salinity on the growth of microalgae and tilapia.

Length-Weight Relationship

Monthly sampling of tilapia fish was made. The total length and weight of the fishes were noted to the nearest 1.0 mm and 1.0 gram respectively. The study was based on the length and weight data of 2500 specimen (length 7.6 to 25.6 cm and Weight 80 gram to 250 gram) collected during the study period 2013 to 2014 .The method suggested by Le Cren [10] was followed to compute the length and weight relationship. Accordingly, the length-weight relationship can be expressed as:

W = _aL^b

Where W and L are weight (g) and length (cm) of the fish respectively and ‘a’ and ‘b’ are two constants (initial growth index and regression constants respectively). When expressed logarithmically be above equation becomes a straight line of the formula: Log W= Log a+b Log L Where, a= intercept, y=log W; x=log L and b=slope.

Results

Analyses of Physico-Chemical Parameters

The physico-chemical parameters were observed in the culture ponds and it was fluctuated based on the atmospheric temperature. During 24 months observation, the minimum temperature of 22.3 and 23.1oC was observed in the month of October, 2013 and 2014 respectively while the maximum temperature of 36.2 and 36.4 was recorded during June 2013 and 2014. The minimum salinity (45 ppt and 50 ppt) was reported during October (2013) and (2014) while the maximum salinity (89 ppt and 92.5 ppt) observed during September (2013) and (2014). The detailed statistical calculation was shown in Tables 1 and 2 and Figures 1 and 2.

Table 1: Univariate statistical value of water Temperature for 2013 and 2014.

Table 2: Univariate statistical value of water salinity for 2013 and 2014.

Figure 1: Temperature variations between 2013 and 2014.

Figure 2: Salinity variations between 2013 and 2014.

Variation in density of Tetraselmis sp.

The minimum microalgae density of 800 and 750 cells/ml were recorded during the month of September 2013 and 2014 respectively. The maximum microalgae density of 365000 and 368000 cells/ml was recorded during December 2013 and 2014 respectively. The statistical variation shown in Table 3 and Figure 3.

Table 3: Univariate statistical value of Algae density for 2013 and 2014.

Figure 3: Algae density between 2013 and 2014.

Growth (Length-weight) variations of Tilapia fish (Plate-1)

The length-weight of tilapia fish were examined and minimum size of 7.6 and 8.1 cm noticed during the month of October 2013 and 2014 respectively. Maximum length of 25.6 and 25.5 cm were recorded during the month of May 2013 and 2014 respectively. The least weight (89 and 80gm) was observed during October 2013 and 2014 while the highest weight was noticed during August 2013 (247 grams) and June 2014 (250 grams). The Linear regression was shown in Table 4 and Figures 4-5.

Table 4: Regression parameters for length-weight relationship of Tilapia fish.

Figure 4: Length – weight relationship of Tilapia fish (2013).

Figure 5: Length – weight relationship of Tilapia fish (2014).

Plate 1: Growth view of Tilapia fish (Oreochromis sp.)

Discussion

The fluxion of climatic changes are affecting natural aquatic environment through increasing of atmospheric temperature. In past few years, world aquatic ecosystem are suffering by several natural disasters, these natural sick significantly affects the aquatic organisms especially micro and macro algae, micro and macro faunas and fishes etc. Present investigation determined the changes of micro algae and tilapia fish in aquaculture ponds by increased water temperature and salinity through rising of atmospheric temperature. The physico-chemical and biological parameters were examined in culture pond and observed vast changes in micro algae density and growth of tilapia fishes. The present study inferred that the increasing temperature and salinity were adversely affects the growth of micro algae and tilapia fish. In the present investigation, the microalgae showed potential growth at 45 to 50 ppt of salinity and further increase in salinity from 50 ppt can leads to the declined growth. In our study tilapia can survived up to 80 ppt salinity and more than this salinity range the fish shown mortality. However the earlier worker stated that the tilapia fish tolerates maximum of 50 ppt salinity [11].

However, noticed that when there was an abrupt change in salinity to a maximum increase of 5 ppt per day, the fish were sluggish for a few minutes after exposure but recovered within one hour after and resumed their normal feeding activity. We have also observed that when the salinity level reached at least above 50 ppt the fish had dark pigmentation, showed erratic swimming behavior and stopped feeding but resumed to normal conditions within a few hours after they adjusted to the salinity conditions. In the course of the salinity tolerance test, we maintained the optimum water quality parameters in the containers. One important factor that we considered was water temperature, which was noticed in range of 25-32°C. This optimum water temperature is crucial in maintaining a steady state plasma osmolality in the fish during exposure to salinity changes [12] and could also be partly responsible in preventing mortalities in the fish.

The physico-chemical observations made discussed by Goldman and Ryther and the culture depth by Persoone [13]. However, the growth of microalgae is affected and influenced by the culture conditions such as light intensity, nutrient limitation, temperature, pH, and salinity [9]. The presently obtained growth on tilapia (Oreochromis niloticus) culture technique with different physico-chemical parameters was positively correlated with Thongprajukaew [14]. Effects of different salinities on the growth and proximate composition of Nannochloropsis sp. and Tetraselmis sp. isolated from South China Sea was earlier studies by [3].

In aquaculture, only microalgae with valuable properties were used and the composition of the algal biomass with regards to lipid, carbohydrate and protein determines its overall economic potential [15]. Nannochloropsis sp. and Tetraselmis sp. are common microalgae species that have promising potential especially in aquaculture industry application [16]. A good alternative is a commercial-scale production of microalgae biomass because this could reduce the cost and ecological impact of intensive fish farming [17]. The increasing in the prices for these fish-based products leads to the search of alternatives to these sources [18].

Decreasing salinity is a unique way to change the biochemical composition of marine microalgae although the changeable role of salinity on starch metabolism indicates it’s species-specific and cultivation condition-dependent nature [19]. Beyond initial survival in brackish and seawater salinities debate continues as to whether tilapia could survive external factors (predators, current, temperatures, disease) they might encounter. Most notable of these factors is temperature. There is little information available on the interactive effects of temperature and salinity tolerance in tilapia [20] and further examination is warranted.

Tilapias are widely cultured throughout the world, and many tilapia species have been evaluated for culture purposes. Several recent research initiatives in tilapia aquaculture involve genetic improvement of these stocks described [21,22]. Oreochromis aureus and O. mossambicus both have higher tolerances for salinity with experimental production of blue tilapia occurring at 44 ppt [23]. Tilapia surviving exposure to 64 ppt salinity. Nile tilapia, O. niloticus; blue tilapia, O. aureus; and mossambique tilapia, O. mossambicus these three species have differing salinity tolerances. The Nile tilapia exhibits a moderate tolerance to salinity with 60 ppt fish surviving direct transfer up to 25 ppt, but its highest growth is achieved at 0-10 ppt [24].

This paper defined the measurement of a tilapia’s ability to survive elevated salt concentrations. Tolerance of Nile tilapia in moderate salinity (20 ppt) and high salt tolerance (>35 ppt) blue tilapia have been documented and were determined to be suitable for comparisons of salinity tolerance with the two hybrid-based varieties. The Nile tilapia will reportedly thrive in any aquatic habitat except for torrential river systems and the major factors limiting its distribution are salinity and temperature [25]. Results suggest that several notable characteristics among varieties of tilapia expressed the greatest tolerance for elevated salinity levels, with 96% survival at 20 ppt and 30 ppt salinities. As blue tilapia were exposed to 35 ppt salinity, survival decreased abruptly to 49%. Blue tilapia has been recognized to have high salt tolerance, in excess of 35 ppt in prior studies with survival at as high as 53 ppt after acclimation [23].

The survival of blue tilapia is 35 ppt and the salinity increase the animal may get to mortality, but previous studies have indicated while direct transfer to seawater can result in almost complete mortality, graduated acclimatization is sufficient to acclimate salt tolerant tilapia successfully [26,27] Nile and Mississippi commercial tilapias withstood rapid acclimatization up to 20 ppt salinity. A more gradual acclimation of tilapia might increase survival, but may not properly model an accidental release of tilapia. Studies have also indicated that early exposure to salinity while in the egg or larval stage increases salinity tolerance significantly [28-30].

Depending on the food source, they will feed either via suspension filtering or surface grazing (GISD 2012), trapping plankton in a plankton rich bolus using mucus excreted from their gills [31]. Nile tilapia are known to feed on phytoplankton, periphyton, aquatic plants, invertebrates, benthic fauna, detritus, bacterial films [32] and even other fish and fish eggs. The average size (total length) of O. niloticus is 20 cm [33]. Aid organizations promoted aquaculture as a means of improving food security with low grain to feed conversion rates, and minimal environmental impacts [34]. Today, tilapia is often farmed with multiple species in the same pond, such as shrimp and milkfish. Nile tilapia can live longer than 10 years (GISD 2012). Food availability and water temperature appear to be the limiting factors to growth for O. niloticus [35]. Optimal growth is achieved at 28-36ºC and declines with decreasing and increasing temperature [32,36]. This study was aimed to determine the optimum temperature and salinity that can result in higher growth of Tetraselmis sp. and tilapia fish. These results can be applied by farmers and industry in culturing microalgae and tilapia with a targeted growth and achieved under certain culture conditions.

Conclusion

The results presented in this paper have demonstrated that the climatic changes affecting physico-chemical and biological properties in aquaculture industry. The raising of atmospheric temperature can adversely affects the water temperature, salinity, micro algae and fishes in aquaculture pond. During the study period, salinity was gradually increased and same time density of micro algae (Tetraselmis sp.) was declined up to 80 ppt of salinity, beyond this range the algae cell attained reverse-osmosis and slowly the algae cell was attained lethal in nature. The change in microalga growth caused by elevated water temperature and salinity can concomitantly affects the growth of cultured fish (Oreochromis sp.). Present study concluded that the maximum temperature and salinity tolerable range of microalga Tetraselmis sp. are 25-32ºC and 40-50 ppt. Likewise tilapia Oreochromis sp. can tolerate the temperature and salinity range of 22.3-36.4ºC and 45-92.5 ppt respectively.

Acknowledgements

The authors were thankful to The Head, Department of Marine Science, Bharathidasan University, Tiruchirappalli-24, Tamil Nadu, India, for providing necessary facilities. One of the author (s) thank the University Grants Commission, New Delhi, Government of India, for Post-Doctoral Fellowship (Ref.No.F./PDFSS-2014-15-SC-TAM-8547; dated, 05.02.2015).

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