CAPE Environmental Science IA Unit 2

An investigation on the rearing practices of Tilapia in the la vega estate pond, gran couva, Trinidad

NAME: SHARANA MOHAMMEDSUBJECT: ENVIRONMENTAL SCIENCE I.A. UNIT 2

SCHOOL: PRINCES TOWN WEST SECONDARY YEAR: 2015 - 2016

Table of ContentsAcknowledgements..................................................................................................................................1

Introduction..............................................................................................................................................2

Scope....................................................................................................................................................2

Purpose.................................................................................................................................................2

Literature Review....................................................................................................................................4

Methodology..........................................................................................................................................14

Activities and Data Collection...........................................................................................................14

Laboratory Tests................................................................................................................................15

Presentation and Analysis......................................................................................................................17

Laboratory Tests....................................................................................................................................17

Discussions of Findings.........................................................................................................................24

Conclusions............................................................................................................................................26

Recommendations..................................................................................................................................27

Bibliography..........................................................................................................................................28

Appendices.............................................................................................................................................29

Appendix 1.............................................................................................................................................29

Site Visits.......................................................................................................................................29

Appendix 2.........................................................................................................................................42

Laboratory Entries.........................................................................................................................42

Acknowledgements

Completing this IA gave me a sense of fulfilment and I would like to thank the following people for their contributions. Firstly, I would like to thank God for giving me wisdom and the serenity needed in completing this project. My gratitude goes to my Environmental Science teacher for his guidance and assistance in completing this project diligently. Sincere thanks goes to my parents for supporting me and giving me much needed help when necessary. Lastly, I pay gratitude to the authors of the various websites via the internet services which allowed me to obtain vital information needed for this Internal Assessment.

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Introduction

Tilapia is an African freshwater cichlid fish that is grown mainly in the wild. These fish are attractive, easily bred, hardy and resistant to disease and, can live in a wide range of water conditions. They can be stocked at high densities and feed on both prepared rations and natural foods. Also, their flesh is firm and of excellent eating quality, as they contain numerous health benefits, which include a rich source of nutrients, vitamins, and minerals, including significant amounts of protein, omega-3 fatty acids, selenium, phosphorous, potassium, vitamin B12, niacin, vitamin B6, and pantothenic acid. Due to these many attributes, tilapia was commercialized as they make an excellent food source (Organic Facts, 2016).

In the Caribbean, there’s a wide variety of tilapia present. In the island of Trinidad, tilapia production began in 1951, with the culture of the Mozambique tilapia, “Oreochromis Mossambicus”. The Mozambique tilapia was crossed with other species to produce hybrids, which include the “black tilapia”, “silver tilapia” and various red hybrids, known as the Red Nile Tilapia (Ramnarine & Barrath, 2004). However, the Red Nile, was first introduced to Trinidad from Jamaica in 1985, and is the most common hybrid of the Mozambique tilapia, in Trinidad. It was found to be most suitable for aquaculture in our island and are bred specifically for their bright red and orange hues. These red hybrids are stronger and faster growing than their pure-line parents and due to their bright red colour, they are more attractive and appealing to consumers than their wild caught (Gabbadon , de Souza, & Titus, 2008).

However, there are many issues faced with tilapia rearing. Firstly, in a pond, among other species, tilapia are the invasive species, thus affecting the survivability of the other organisms (Hailey, 2015). Additionally, farmed tilapia is less healthy than wild tilapia because reared tilapia is fed an unnatural, unhealthy diet of cheap grains and soy pellets, rather than plankton, plants and algae, and also contain less healthy fatty acids than their wild counterparts. Furthermore, tilapia is at risk of parasitic diseases due to biological factors such as age, stress, poor diet, high stocking densities and environmental factors such as salinity, poor water quality, culture system, as report by Komar & Wendover (2007).

Scope

This study is focused on the rearing of tilapia in a selected pond in Trinidad. This is done to ascertain the environmental findings of Komar & Wendover (2007) in order to highlight the possible advantages and disadvantages of farmed tilapia as opposed to wild tilapia.

Purpose

Tilapia is commercialized in the island of Trinidad as it makes an excellent and economical food source. Resulting from this commercialization are attributes such as income and

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employment for the citizens of the country. However, reared tilapia is exposed to a different environment than naturally occurring or wild tilapia. As such, the purpose of this study is to recognize the differences between farmed and wild tilapia and to investigate the ecosystem and pollution level resulting from farmed tilapia as opposed to its wild counterparts.

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Literature Review

The two most prominent means of rearing tilapia are via tanks and ponds. Confinement tanks allow tilapia to grow well at high densities, when good water quality is maintained, through aeration and continuous water exchange, to renew dissolved oxygen (DO) supplies and remove wastes. Whereas, pond culture is advantageous as it allows tilapia to utilize natural foods. Pond culture may utilize extensive systems, where only organic or inorganic fertilizers are used, or intensive systems, which makes use of high protein feed, aeration and water exchange. Regardless, in both rearing methods, the optimum water temperature should be maintained at 82-860F; at temperatures below 54°F, tilapia lose their resistance to disease and are subject to infections by bacteria, fungi and parasites (Rakocy & McGinty, 1989).

Research Professor at the University of the West Indies, Indar Ramnarine, indicated that, in Trinidad, most tilapia rearing projects use earthen ponds. However, there is a tank culture operation in central Trinidad that utilizes injected oxygen in their system. He further stated that, Caroni (1975) Limited and the Sugarcane Feeds Centre also use concrete and metal tanks, but production from tank culture is limited, and, at the Bamboo Grove Fish Farm, there are four octagonal concrete tanks with a solids removal system (Ramnarine & Barrath, 2004).

Tilapia feed can contribute to making the water toxic. Uneaten tilapia food results in undissolved solids, that are suspended in the water or rests on the bottom, which toxifies the water. These solids eventually dissolve in the water, forming dissolved solids. Dissolved solids are partly made up of tilapia feed, that has been broken down into very fine particles, that remain suspended in water and further contributes to the formation of more toxic compounds, such as un-ionized ammonia. The ammonia is consumed by naturally occurring bacteria, known as nitrosomonas, however, these bacteria give off even deadlier compounds, called nitrites that oxidize to nitrates, which further affects the water quality. Furthermore, resulting from the tilapia feed, are other dissolved contaminants, such as tannins and phenols, which decolorizes the water and makes it smell bad, thereby further toxifying the water (Lakeway Tilapia, 2016).

In the wild, tilapia consume a diet of algae and various plants, however, farmed tilapia is fed an unnatural, unhealthy diet of GMO corn and soy pellets. When humans consume farmed tilapia, this unnatural diet results in health issues, such as aggravation in the body like asthma, joint inflammation and coronary disease. Another primary ingredient in the feed of farmed tilapia is chicken feces as it’s a cheaper alternative to standard fish food. This results in ten times the normal amount of carcinogenic, or cancer causing, agents as wild tilapia. Another impact resulting from tilapia feed is that it produces eleven times the amount of a lethal substance, dioxin, in the farmed tilapia fish than those in wild (Simple Organic Life, 2015). Additionally, tilapia is deemed healthy due to its richness in the omega-3 fatty acids. However, these acids are greater in wild tilapia than farmed. Due to the farmed tilapia consuming a diet of corn and soy rather than lake plants, they’re rich in omega-6 acids, which studies have been proven to harm the heart and the brain (Eat This, Not That!, 2014).

Water quality comprises of physical, biological and chemical parameters that affect the growth and welfare of cultured organisms. It affects the general condition of cultured organisms as it determines the health and growth conditions of these organisms. Quality of

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water is, therefore, an essential factor to be considered when planning for high aquaculture production (Mallya, 2007). One of the five basic needs of tilapia is clean water. However, as a result of tilapia rearing, due to factors such as leaching into ponds, the types of feed, and improper waste disposal, is the predicament of the physicochemical characteristics of the pond water being altered and affected. As such, water quality tests are done to quantitatively determine the effects of tilapia rearing on water systems and the environment (eXtension, 2012).

These test were –

a) Biological Oxygen Demandb) Temperaturec) pH d) Turbiditye) Total Solids f) Total Phosphatesg) Nitrites h) Alkalinityi) Salinity j) Ammonium ionk) Coliform

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Biological Oxygen Demand

Essential for respiration and decomposition, DO comes from atmospheric oxygen and photosynthesis but because photosynthesis depends on the amount of light available to aquatic plants, it takes time for the oxygen to fully dissolve and for correct levels to be maintained. Tilapia is highly tolerant of low dissolved oxygen (DO) concentrations at concentrations below 0.3 mg/L. However, the DO concentration in tilapia ponds should be kept at 1 mg/L, to prevent reductions in growth and disease resistance. In a “healthy” body of water, oxygen is replenished quicker than it’s used by aquatic organisms. However, in some bodies of water, aerobic bacteria decompose such a vast volume of organic material, that oxygen is depleted from the water faster than it can be replaced. The resulting decrease in dissolved oxygen is known as the Biochemical Oxygen Demand (BOD).

Vital nutrients, for example nitrates and phosphates, which stimulate aquatic plant and algae growth, are released via decomposition. If the load of decomposing organic material is excessive, dissolved oxygen levels can be critically diminished. In a body of water with substantial amounts of decaying organic material, the dissolved oxygen levels may decline by 90%, this would represent a high BOD. This can be widely impacted by pollution and therefore needs to be monitored. Table 1 shows the effect of various levels of BOD in the water.

Table 1 – The interpretation of BOD Levels

BOD Level (mg/L)

Status

1-2 Clean water with little organic waste.

3-5 Moderately clean water with some organic waste.

6-9 Lots of organic material and bacteria.

10-20 Very poor water quality. Large amounts of organic material in the water common to treated sewage.

20-100 Untreated sewage or high levels of effluents from industries or high levels of erosion.

>100 Extreme conditions. Siltation and stationary water.

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Temperature

Aquatic organisms are extremely fragile to the temperature of their environment. The growth rate of tilapia is best between a temperature of 220C (72F) and 290C (84F). If the temperature of the water isn’t at this optimum range, the tilapia won’t be able to survive and reproduce and may eventually die. Therefore, the measure of the temperature of the water is very important as an indication of water quality. Table 2 shows the cause and effect relationship with changes in temperature.

Table 2 – The causes and effects of changes in water temperature

Changes in Water Temperature

Causes Effects

- Air Temperature - Solubility of dissolved oxygen

- Amount of shade - Rate of plant growth

- Soil erosion from increasing turbidity - Metabolic rate of organisms

- Thermal pollution from human activities - Resistance in organisms

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pH

Aquatic organisms are extremely fragile to the pH of their environment. The growth rate of tilapia is best between a pH of 7 – 9. If the pH of the water isn’t at this optimum range, the tilapia won’t be able to survive and reproduce and may eventually die. Therefore, the measure of the pH of the water is very important as an indication of water quality. The factors that affect pH can be seen in Table 3.

Table 3 – Factors that affect pH levels

Factors Affecting pH Levels

- Acidic rainfall

- Algal blooms

- Level of hard-water minerals

- Releases from industrial processes

- Carbonic acid from respiration or decomposition

- Oxidation of sulphides in sediments

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Turbidity

Turbidity is a measure of the transparency of water, and one of the main contributors to it in a tilapia pond is phytoplankton. If phytoplankton are allowed to grow to very high density, a high turbidity results. This is because an abundance of plankton discolours water and reduces sunlight penetration. Water with high turbidity is cloudy, whereas water with low turbidity is clear. A high turbidity is as a result of light reflecting off of particles in the water thus resulting in the cloudiness. As such, the more particles in the water, the higher the turbidity. Also, the rate of photosynthesis will decrease due to this because a high turbidity will decrease the amount of sunlight that’s able to penetrate the water. When the water is cloudy, sunlight will warm it more efficiently because the suspended particles in the water absorb the sunlight, warming the surrounding water. This may lead to many issues linked to increased temperature levels. Therefore, the Turbidity of a beach needs to be measured to guarantee it doesn’t produce unwanted effects as shown in Table 4.

Table 4 – The sources and effects of turbidity in coastal waters

Change in Water Temperature

Source Effect

- Soil erosion – silt & clay - Reduces water clarity

- Urban runoff - Aesthetically displeasing

- Industrial waste – sewage treatment effluent particulates

- Decreases photosynthetic rate

- Abundant bottom dwellers – stirring up sediments - Increases water temperature

- Organics – microorganisms & decaying plants & animals

Total Solids

A measure of all the suspended, colloidal, and dissolved solids in the water is known as Total solids, TS. This includes dissolved salts for example, sodium chloride, NaCl, and solid particles such as silt and plankton. Total solids have the same impacts as Turbidity and are described in Table 4.

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Total Phosphates

Phosphorus is a vital nutrient for other species present in the tilapia ponds such as aquatic plants and algae. However, only a minute amount is necessary, therefore, an excess can easily occur. An excess amount is classified as a pollutant as it results in eutrophication, the condition whereby there’s an excessive richness in nutrients, such as phosphorous, which results in increased plant and algal growth. Eutrophication can lower the levels of dissolved oxygen in the water and can make the water uninhabitable by the tilapia. Phosphorus is frequently the limiting factor that controls the extent of eutrophication that occurs. Table 5 shows the sources and effects of phosphate levels in water.

Table 5 – The sources and effects of phosphate levels in water

Phosphate levels

Source Effect

- Human and animal wastes

- High levels of – eutrophication, increased algal bloom, increased BOD, decreased DO

- Industrial wastes - Low levels – limiting factor in plant and algal growth

- Agricultural runoff

- Human disturbance of land

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Nitrites

Nitrites are an essential source of nitrogen required by plants and animals to synthesize amino acids and proteins. Nitrate levels below 10mg/L are not directly toxic to tilapia. However, it becomes toxic when levels exceed 25 - 30 mg/L, and as a result may lead to death of the tilapia. Nitrate pollution, caused by fertilizer runoff and concentration of livestock in feedlots, has also become a major ecological issue in tilapia farms. Table 6 shows the sources of nitrate ions in surface water.

Table 6 – Sources of Nitrate Ions

Sources of Nitrate Ions

- Agriculture runoff

- Urban runoff

- Animal feedlots and barnyards

- Municipal and industrial wastewater

- Automobile and industrial emissions

- Decomposition of plants and animals

Alkalinity

A measure of how much acid water can neutralize is known as the Alkalinity of water. Alkalinity levels should be maintained at 100 to 250 mg/L, and it acts as a buffer, protecting the water from immediate changes in pH. This ability to neutralize acid, is vital in ensuring the survival of reared tilapia. Table 7 shows the effect of alkalinity to surface water.

Table 7 – The effects of alkalinity levels

Effects of Alkalinity Levels

- Buffers water against sudden changes in pH

- Protects aquatic organisms from sudden changes in pH

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Salinity

Salinity is the measure of all the salts dissolved in water. All tilapia are tolerant to brackish water. The tolerance of tilapia to salinity depends on the type of species, strains, size, adaptation time and environmental factors. However, the ideal salinity for tilapia growth is up to 15 ppt.

Ammonia

Ammonia, NH3, is a compound composed of nitrogen and hydrogen molecules. The levels of ammonia have a strong impact on the water quality for tilapia, and levels which are two high may result in the death of tilapia. Ammonia exists in two forms – unionized ammonia, NH3, and ionized ammonia, NH4+. Unionized ammonia most toxic to tilapia, especially those which are smaller in size. Both ammonia and ammonium are present in the water at all times, and the percentage is influenced by temperature and pH. Warmer water, higher pH values and low levels of dissolved oxygen concentrations favor unionized ammonia which is more toxic.

Table 8 – The consequences of ammonia levels

Ammonia level (mg/L NH3-N) Consequence

<0.6 Preferred ammonia level for tilapia

0.6 – 2.0 Lethal concentration for tilapia

1.0 Concentrations as low as 1.0 mg/L NH3 –N will decease growth and performance in tilapia

>2.0 Tilapia start to die

Coliform

Both fresh and brackish water fishes can harbour human pathogenic bacteria, specifically the coliform group. Faecal coliforms, e.g. “Escherichia coli” which originates from faeces of warm blooded animals, in fish indicate the level of pollution of their environment because coliforms are not the normal flora of bacteria in fish. Since these bacteria originate from the wastes of animals or humans, high numbers of E. coli in a pond may come from septic systems, runoff from barnyards, or from wildlife. The enteric bacilli include E. coli, Klebsiella spp., Citrobacter spp., Enterobacter spp., Serratia spp., and Edwarsiella spp. However, in Trinidad, bacterial density in rearing ponds has never been reported, therefore, the present test was used to investigate the occurrence of coliforms reared in ponds so that it could be used as a standard for further studies on fish quality.

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The highlighted concern with this method of the rearing of tilapia is that, if it is not done within the prescribed parameters of the pond size and fish density, it may result in the fish becoming contaminated with a virus or human pathogenic bacteria. Araujo et al (1989) found that there was a strong link between the presence of coliforms between 9 to 107 cfu/100 ml and these human pathogens in fresh water with average presence of 102–109 cfu/100 ml. Further, Madal et al (2009), found a strong correlation between the absorption of these microbia into the tilapia fish posing a threat to health and safety of humans.

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Methodology

Activities and Data Collection

For this study, various tilapia ponds were visited in Trinidad. The population size of the tilapia in the pond was determined by using the ecological sampling method of “mark, release, recapture” was utilized. Firstly, the tilapia was captured, after which, it was carefully tagged. It was then released back into the pond and recaptured once more. The equation

Population Estimate (N )=(Total Number Captured , Marked∧Released(n1)) x (Number Captured(n2))Total Number Captured with Mark(n3)¿

¿

was used to calculate the overall population, whereby N was the total population, n1 was the number of tilapia captured, marked and released, n2 was the total number captured on the second occasion and n3 was the number of marked tilapia recaptured. Additionally, upon capturing the tilapia, their size was measured, and their general colour was observed. Overall, the aforementioned processes were done so that the findings could be compared to the data from the Literature Review, in order for generalizations about the various aspects of tilapia to be made.

Furthermore, water samples were collected from each site and water quality tests were done on these samples. This is because, water plays an essential role in the sustainability of tilapia, since they need clean water to survive and to produce a healthy fish. Various factors, such as the type of feed, and pollution, would affect the physicochemical characteristics of the pond water, thereby altering its natural balance. As such, water quality tests were done to quantitatively determine the effects of tilapia rearing on water quality.

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Laboratory Tests

Water quality tests will give information about the “health” of the pond water. By testing water over a period of time, the alterations in the quality of the water can be seen. However, due to the limitation of time with the borrowed equipment, reagents and time only one set of tests could have been performed for each site visited. The parameters that were tested in this project included temperature, pH, turbidity, nitrites, phosphates, BOD5, alkalinity, coliform, ammonia and salinity. A qualitative visual assessment of the aquatic system was also carried out.

A LabQuest2 water quality testing package, provided by the University of Trinidad and Tobago, Agricultural and Food Technology Department, was used to test the water quality parameters.

The LabQuest2 water quality testing kit included probes for testing water, temperature, pH, turbidity, nitrates, phosphates, BOD and alkalinity.

The LabQuest2 is a portable, hand held device, to which various probes are used to determine the properties of the sampled water. At each site, each group of the three groups collected four (4) water samples using plastic bottles from the water of the beach. These bottles were labelled A to D. In addition to the four water samples taken, another five (5) samples were taken using glass bottles to test for BOD5, these bottles were labelled E1 to E5.

The water samples were collected by completely submerging the bottles into the water and allowing water to fill up to the “mouth” of the bottle. After this, the lid was quickly fastened on the bottle, while it was still under water. The bottles were then packaged and transported to the laboratory. This method of sampling was done for all the sites visited. Each sample set was then brought to the laboratory for testing using the LabQuest2 to obtain the following readings of –

Biochemical Oxygen Demand – Bottles E1 to E5 which were stored in ice and wrapped in foil were used for this. The dissolved oxygen levels present on the initial day and at the end of the five day period were measured using the Dissolved Oxygen Sensor. The difference and average was then determined as the BOD5. (Refer to Lab 1)

Temperature. – The Stainless Steel Temperature Probe was placed into bottle “A” and after the temperature stabilized on the interface, the reading was recorded. (Refer to Lab 2)

pH – The pH Sensor Probe was placed into bottle “A” and swirled until a reading of the pH was stabilised on the interface and the reading was recorded. (Refer to Lab 2)

Nitrites – The nitrate-ion concentration in the water sample from bottle “A”, in mg/L NO2, was measured by placing the electrode from the Nitrite Ion-Selective Electrode into the bottle. The reading was then recorded. (Refer to Lab 2)

Turbidity – The Turbidity in NTU was determined using the Turbidity Sensor. Water from sample bottle “A” was poured into a cuvette and placed into the Turbidity Sensor. The reading was then recorded. (Refer to Lab 2)

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Salinity - The Salinity of the water samples was determined by placing a salinity sensor in each water sample to determine the total dissolved salt content in each solution. (Refer to Lab 2)

Ammonia - After standardization, an ammonium ion select probe was placed in each water sample to determine the ammonium ion concentration of each sample. (Refer to Lab 2)

Total Solids – A precise amount of water from Bottle “B” was measured and placed into a clean, dried and weighed beaker. A drying oven was then used to evaporate the water and the beaker was reweighed. The difference between the final and initial mass the total solids was calculated. Calculations were also made to convert the mass to mg/L total solids. (Refer to Lab 3)

Total Phosphates – A colorimeter was used to create a 4-point standard curve of phosphate absorbance vs concentration, by using a set of four phosphate standards. The water sample from bottle “C” was then poured into the cuvette and placed into the colorimeter to determine its absorbance. The concentration of the total phosphates was deduced from the graph, using the absorbance of the water sample. (Refer to Lab 4)

Alkalinity – Alkalinity of the water samples was determined by titrating 0.001M sulphuric acid against the water sample in Bottle “D”, using a methyl orange indicator to determine the end point of the reaction. At the end point of the reaction, the alkalinity was determined using the stoichiometric ratio between sulphuric acid and calcium carbonate. (Refer to Lab 5)

Coliform - To determine the level of E-Coli present at each site, a plate count using agar was done, after seven serial dilutions. (Refer to Lab 6)

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Presentation and Analysis

Laboratory Tests

Graph 1 –

A B C D0

102030405060708090

100

Graph Showing The BOD (mg/L), Total Solids (mg/L) and Turbid-ity (NTU) Level At Each Site

BOD (mg/L)Total Solids (mg/L)Turbidity (NTU)

Site

Ave

rage

BO

D (m

g/L)

, Tot

al S

olid

s (m

g/L)

, and

Tu

rbid

ity (N

TU)

From the graph above it is observed that as the level of Total Solids increases, the level of Biological Oxygen Demand and Turbidity also increases. Site B had the highest level of Total Solids which was 90mg/L, whilst Site A had the lowest which was 75mg/L. The BOD level at Site C was the highest, which was 7.38mg/L and Site D was the lowest, at 6.02mg/L. Site D had the highest Turbidity level which was 27NTU, whereas Site A had the lowest level, which was 18NTU.

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Graph 2 –

A B C D0

1

2

3

4

5

6

7

8

Graph Showing The BOD (mg/L) and Salinity (ppt) Level At Each Site

BOD (mg/L)Salinity (ppt)

Site

Ave

rage

BO

D (m

g/L)

and

Sal

inity

(ppt

)

From the graph above it is observed that as the level of Salinity increases, the level of Biological Oxygen Demand also increases. The Salinity level at Sites C and D are the highest with a value of 1.3ppt, whilst Sites A and B had similar levels which were 1.2ppt and 1.1ppt respectively. The BOD level at the four sites ranged between 6.02mg/L and 7.38mg/L.

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Graph 3 –

A

B

C

D

0 2 4 6 8 10 12 14

Grah Showing The Total Phosphates (mg/L), Nitrates (mg/L) and pH Level At Each Site

Total Phoshates (mg/L)Nitrates (mg/L)pH

Level of Total Phosphates (mg/L), Nitrates (mg/L), pH

Site

The graph above indicates that there were fluctuations among the levels of Nitrates and Phosphates present at the sites; site B had the highest level of Nitrates (12.7mg/L) and Phosphates (4.63mg/L). The pH values of the four visited sites were fairly similar with values ranging between 7.31 – 7.84.

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Graph 4 –

A B C D0

5

10

15

20

25

30

35

40

45

Graph Showing The Alkalinity (mg/L) And Nitrate (mg/L) Level At Each Site

Nitrate (mg/L)Alkalinity (mg/L)Ammonium (mg/L)

Site

Leve

l of A

lkal

inity

(mg/

L) a

nd N

itrat

es (m

g/L)

The above graph shows that when the Alkalinity level in water is high, the Nitrate level is low. Site C had the highest Alkalinity level at 39mg/L, and therefore the lowest Nitrate level at 6.4mg/L. In contrast, Site D had the lowest Alkalinity level, which was 31mg/L and a Nitrate level of 9.8mg/L. The Ammonium level at all sites were similar ranging between 0.7mg/L – 0.9mg/L.

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Graph 5 –

A B C D0

5

10

15

20

25

30

Graph Showing The Temperature (0C) And BOD (mg/L) Level At Each Site

TemperatureBOD

Site

Leve

l BO

D (m

g/L)

and

Tem

pera

ture

(0C

)

From the graph above it is observed that as Temperature increases, the level of Biological Oxygen Demand also increases. At each site, the temperature and BOD levels were fairly similar, ranging between 24.440C – 27.430C and 6.02mg/L – 7.38mg/L respectively.

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Graph 6 –

1.85E+08

7.35E+07

1.11

E+08

Donut Chart Showing The Average Colonies/100mL

Total CountColiscan - purple (E.coli)Coliscan - red, pink & purple (coliforms)

The graph above shows that the Coliform value was 1.11E+08, which was higher than the value of E. Coli which was 7.35E+08. The Total Count of both values was 1.85E+08.

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Graph 7 –

8.60E+07

9.10E+079.30E+07

9.95E+07

Pie Chart Showing The Total Coliform per 100mL of Water At Each Site

A B C

D

The above graph shows that sites A, B, C and D had relatively similar Total Coliform values, ranging between 8.60E+07 - 9.95E+07.

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Discussions of Findings

The results of the tests indicated that each site had a moderate level of Biological Oxygen Demand ranging between 6.02 – 7.38. Aquatic organisms obtain oxygen in the form of dissolved oxygen. When aerobic bacteria decompose a vast volume of organic material such that oxygen is depleted faster than it can be replaced, the resulting decrease in dissolved oxygen is known as the Biological Oxygen Demand. From the information presented in the Literature Review, it is noted that a BOD level ranging from 6 -9 indicates that the water contained lots of organic material and bacteria. This is justified since, the level of BOD in water would be affected by the level of Turbidity and Total Solids. Turbidity is a measure of water’s lack of clarity and can thus be interrelated to the level of Total Solids, which consist of solid particles which may have a dark appearance, since a high level of Total Solids present would cause water to lose its clarity and thus results in a high Turbidity level. Furthermore, the dark appearance of the large amounts of solid particles in water will attract heat from the sun and cause the temperature of the water to increase. This therefore causes water loses its ability to hold dissolved oxygen which therefore results in an increase in the Biological Oxygen Demand.

Another factor which would result in an increase in the level of Biological Oxygen Demand would be Salinity. From the Literature Review, Salinity is defined as “the measure of all the salts dissolved in water”, and tilapia can survive at Salinity levels of up to 15 ppt. When Salinity increases, there will be more salt particles being present in the water. These salts may have a dark appearance when present in the water and would thus attract heat via sunlight. As a result, there will be an increase in water temperature, thereby causing the water to lose its ability to hold dissolved oxygen, which results in an increase in the Biological Oxygen Demand. However, from the results obtained, it was deduced that the Salinity levels at each site was 1.3 ppt and less, which according to the Literature Review, will allow for the survival of the tilapia.

Temperature also has an effect on the Biological Oxygen Demand. As mentioned above, when the temperature increases, water loses its ability to hold dissolved oxygen which therefore results in an increase in the Biological Oxygen Demand. From the information presented in the Literature Review, it is noted that the growth rate of tilapia is best between a temperature of 220C and 290C. The results of the tests depicted that the temperature of the sites ranged between 24.440C – 27.430C. Thus, it is confirmed that the water temperature at each site is appropriate for the growth and reproduction of tilapia.

Furthermore, from the research done, it is noted that different forms of agricultural processes take place at the La Vega estate. As such, Nitrate and Phosphate fertilizers may have been utilized, which would have therefore entered the pond water. Nitrates, which are acidic in nature, and Phosphates, which are basic in nature, would affect the pH of water. The pH of each site ranged between 7.31 – 7.84. On the pH scale, a pH of 7 is neutral, below 7 is acidic and above 7 is basic. As such, these pHs would be considered relatively neutral. Since the pH of the sites was fairly neutral, it can be established that the existence of both Nitrates and Phosphates in water kept the pH at a relative balance. Furthermore, from the data established in the Literature Review, it is noted that the growth rate of tilapia is best between a pH of 7 –

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9. Therefore, the pH of the water at each site would allow for the optimum growth of the tilapia.

Additionally, the level of Nitrates present would be affected by the level of Alkalinity of the water. This is because the Alkalinity of water is a measure of how much acid it can neutralize. When the Alkalinity level is high, the Nitrate level would therefore be low as water is able to neutralize nitrates which are acidic in nature. From the results obtained, it was seen that each site had a high level of Alkalinity and nitrate levels which were lower than 12.7mg/L and less. From the Literature Review, it is noted that nitrate levels above 25mg/L would be toxic to the tilapia. Therefore, these levels would not be toxic to the tilapia since the high alkalinity of the water is able to keep the nitrate levels within a low range.

Apart from nitrates, the presence of ammonia in the pond will result in an overall increase in the nitrogen supply to the tilapia and other aquatic organisms. According the Literature Review, unionized ammonia – NH3, is toxic to tilapia however ionized ammonia – NH4+ (ammonium), isn’t toxic. From the results obtained, the ammonium concentrations were 0.9mg/L and less, which will not be toxic to the tilapia and allow them to survive comfortably.

Lastly, there are toilet facilities near the pond, with the sewage water pipe running into the pond. Due to this, there may be human related bacteria present in the pond. This is justified from the results obtained as it showed that the average colonies per 100mL were high in value, with the highest value being 7.35E+07, which was from the Coliscan – purple. In addition to this, the Total Coliform per 100mL of water at each site was relatively high and similar to each other, with values ranging between 8.60E+07 – 9.95E+07. As a result, the Total Coliform in the pond was high. From the Literature Review, it was established by “Araujo et al (1989)”, that there was a strong link between the presence of coliforms between 9 to 107 cfu/100 ml and human pathogens in fresh water with average presence of 102–109cfu/100 ml. In addition to this, “Madal et al (2009)”, found a strong correlation between the absorption of these microbia into the tilapia fish posing a threat to health and safety of humans. As such, the results obtained would justify the information presented in the Literature Review since the levels of Total Coliform at each site was relatively high. Although the tilapia would be able to survive under these conditions and would not be directly affected, if the tilapia is consumed by humans, it may result in health complications. Additionally, the high levels of bacteria present would contribute to an increase in Total Solids, Turbidity and BOD, which would cause harm to the fish, thereby inhibiting their survival.

25

Conclusions

Within the limits of experimental errors, from the various observations made throughout this Internal Assessment and tests carried out at all four sites, all sites, and therefore the entire pond, provided the necessary conditions for the rearing of tilapia. However, certain parameters such as Total Solids, BOD and Turbidity contained values which were higher than the required ranges for the survival of tilapia. These increased values would therefore have an effect on the growth and reproduction of tilapia in the pond.

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Recommendations

- An alternative method to running the waste water pipe into the pond should be used.- The restroom facilities should be located away from the pond.- The quality of water of the pond, at all sites, should be monitored frequently so that

the tilapia and other aquatic organisms have an optimum environment for growth and maintenance.

27

Bibliography

Eat This, Not That! (2014). How Tilapia is a More Unhealthy Food Than Bacon. Retrieved from Eat This, Not That!: http://www.eatthis.com/tilapia-is-worse-than-bacon

eXtension. (2012, October 17). Water Quality in Aquaculture. Retrieved from eXtension: http://articles.extension.org/pages/58707/water-quality-in-aquaculture

Gabbadon , P., de Souza, G., & Titus, A. (2008). A Manual for Commercial Tilapia Production. Institute of Marine Affairs.

Komar, C., & Wendover, N. (2007, June 18). Parasitic Diseases Of Tilapia. Retrieved from The Fish Site: http://www.thefishsite.com/articles/294/parasitic-diseases-of-tilapia/

Lakeway Tilapia . (2016). Tilapia farming guide - Understanding the five needs of tilapia. Retrieved from Lakeway Tilapia: https://lakewaytilapia.com/How_To_Raise_Tilapia.php

Organic Facts. (2016). Health Benefits of Tilapia. Retrieved from Organic Facts: https://www.organicfacts.net/health-benefits/animal-product/tilapia.html

Rakocy, J. E., & McGinty , A. S. (1989). Tank and Pond Culture of Tilapia. Southern Regional Aquaculture Centre (SRAC) Publication.

Ramnarine, I. W., & Barrath, C. (2004). Tilapiia Culture In Trinidad and Tobago: Yet Another Update.

Simple Organic Life. (2015, April 5). Here’s Why You Should Never Eat Tilapia Again. Retrieved from Simple Organic Life: http://simpleorganiclife.org/never-eat-tilapia/

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http://simpleorganiclife.org/never-eat-tilapia/

Appendices

Appendix 1

Site Visits

Site Visit: 1

Date: 20/01/2016

Location: La Vega Estate, Gran Couva

Map:

Map 1: Showing location of Site A in the La Vega Estate pond

Title: Environmental Survey of tilapia production in an earth pond.

Aim: To assess fish population, feeding practices its effects on the environment and water quality and hence deduce the quality of the fish.

29

Objectives:

- To observe the overall practice of Tilapia rearing and identify areas of waste production

- To assess tilapia population.- To identify and record waste management strategies being employed.- To assess water quality of the pond

Introduction: The Tilapia pond is located at the La Vega Estate, Gran Couva, which is in Central Trinidad. The Estate is approximately 250 acres, however the pond itself is approximately 2.67 acres or 10, 800 sq meters. The uses of the pond range from recreational to the rearing of a range of fishes, predominantly Tilapia for the local market. Over the years, tilapia became the dominant species in the pond, which is currently made up primarily of Mozambique tilapia. For this investigation, the pond was divided into 4 sites.

Site A is located near the huts, with the nearby vegetation being mainly lawn grass, with some ornamental trees such as palms and fruit trees (golden apple and jamon). The water at this site of the pond was light brown in colour, however, the water near the bank was fairly transparent.

Image 1: Showing the aerial view of the La Vega Estate pond

30

Image 2: Showing the longitudinal view of Site A in the La Vega Estate pond

Methodology/Activities: The “Mark and Recapture” method was used to estimate the population of tilapia at Site A of the pond. The fishes were also observed for any form of discolorations as indications of illness. Furthermore, water sample were taken and were quality tests were done. The feeding practices and harvesting were also documented.

Mark and Recapture -

Day 1 –

For this method, feed pellets were used to attract the tilapia to a specific location and nets were used to capture several tilapia alive at one time. Each tilapia was marked by tagging them with a T-bar and they were then released back into the pond, unharmed. After two hours, the fish were again caught and data was taken pertaining to how many tilapia were captured with and without tags. The mathematical formula below was used to estimate the population size of the tilapia. The total size of the pond was 10, 800 sq meters, however, the sample area used was 36 sq meters.

31

Observations and Results:

Trial Number Number Captured Number Recaptured with mark1 17 82 17 63 17 64 18 65 18 76 18 87 19 68 21 79 18 610 17 5

Total: 180 65

Population Estimate=180 ×7265

=199 in 36 sq meters

Total population based on this estimate = 19936

×10,800=59,700

*Ideal population based on the size of pond = 10,800 × 4=43,200

This is based on the literature finding which indicated that the ideal conditions for Tilapia is 4 fish to 1 sq meter.

Difference in population – 59, 700 – 43, 200 = 16, 500

Percentage difference – 16, 500/43, 200 x 100 = 38%

Discussion: Based on the size of the pond, the ideal population of tilapia was determined to be 43, 200. However, after using the formula to estimate the population of Tilapia in the pond from the first 10 trials, it was found that the total estimated population was 59, 700. Therefore, the total estimated population of tilapia present at Site A of the pond was 38% greater than the ideal population. This is because the sampling technique used was biased, as it gave only an estimated population of the tilapia rather than the actual value, thus resulting in a higher population figure.

Conclusion: The total estimated population of Tilapia at Site A of the La Vega Estate pond was 59, 700 fish.

Follow Ups: The site should be visited during other months of the year, between both the dry and rainy season, and the physicochemical tests and the experiment for the population size of the tilapia should be carried out, in order to obtain more accurate data.

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Site Visit: 2

Date: 27/01/2016


Map:

Map 1: Showing location of Site B in the La Vega Estate pond



Objectives:



Introduction: The Tilapia pond is located at the La Vega Estate, Gran Couva, which is in Central Trinidad. The Estate is approximately 250 acres, however the pond itself is approximately 2.67 acres or 10, 800 sq meters. The uses of the pond range from recreational to the rearing of a range of fishes, predominantly Tilapia for the local market. Over the years,

33

tilapia became the dominant species in the pond, which is currently made up primarily of Mozambique tilapia. For this investigation, the pond was divided into 4 sites.

Site B is located near the huts, with no major vegetation being present. At this site, the color of the water in the pond was light brown. However, the pond water was mostly covered with lilies, which limited the water clarity.

Methodology/Activities: The “Mark and Recapture” method was used to estimate the population of tilapia at Site B of the pond. The fishes were also observed for any form of discolorations as indications of illness. Furthermore, water sample were taken and were quality tests were done. The feeding practices and harvesting were also documented.


Day 1 –




Total: 200 61

Population Estimate=200×7261



×10,800=70,800

*Ideal population based on the size of pond = 10,800 × 4=43 ,200

34




Discussion: Based on the size of the pond, the ideal population of tilapia was determined to be 43, 200. However, after using the formula to estimate the population of Tilapia in the pond from the first 10 trials, it was found that the total estimated population was 70, 800. Therefore, the total estimated population of tilapia present at Site B of the pond was 64% greater than the ideal population. This is because the sampling technique used was biased, as it gave only an estimated population of the tilapia rather than the actual value, thus resulting in a higher population figure.

Conclusion: The total estimated population of Tilapia at Site B of the La Vega Estate pond was 70, 800 fish.


Site Visit: 3

Date: 03/02/2016


Map:

35

Map 1: Showing location of Site C in the La Vega Estate pond

Image 1: Showing the longitudinal view of Site C in the La Vega Estate pond



Objectives:

36




Site C is located near the huts, with the nearby vegetation being mainly lawn grass. The water at this site of the pond was brown in color and was relatively transparent.



Day 1 –




37

Total: 190 59

Population Estimate=190 ×7259



×10,800=69,300





Discussion: Based on the size of the pond, the ideal population of tilapia was determined to be 43, 200. However, after using the formula to estimate the population of Tilapia in the pond from the first 10 trials, it was found that the total estimated population was 69, 300. Therefore, the total estimated population of tilapia present at Site C of the pond was 60% greater than the ideal population. This is because the sampling technique used was biased, as it gave only an estimated population of the tilapia rather than the actual value, thus resulting in a higher population figure.

Conclusion: The total estimated population of Tilapia at Site C of the La Vega Estate pond was 69, 300 fish.


Site Visit: 4

Date: 10/02/2016


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Map:

Map 1: Showing location of Site D in the La Vega Estate pond



Objectives:




Site D is located near the restroom areas. The nearby vegetation is mainly forested trees. The water at this site of the pond was dark brown in color and was not transparent. The sewage waste water pipe was seen entering the pond at this site.

39



Day 1 –




Total: 184 66

Population Estimate=184×7266



×10,800=60,000





40

Discussion: Based on the size of the pond, the ideal population of tilapia was determined to be 43, 200. However, after using the formula to estimate the population of Tilapia in the pond from the first 10 trials, it was found that the total estimated population was 60, 000. Therefore, the total estimated population of tilapia present at Site A of the pond was 39% greater than the ideal population. This is because the sampling technique used was biased, as it gave only an estimated population of the tilapia rather than the actual value, thus resulting in a higher population figure.

Conclusion: The total estimated population of Tilapia at Site D of the La Vega Estate pond was 60, 000 fish.


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Appendix 2

Laboratory Entries

Lab: 1

Date: The lab was done on the same dates the site visits were carried out

Title: Biochemical Oxygen Demand

Aim: To determine the Biochemical Oxygen Demand (BOD5) of all four sites.

Materials and Apparatus:

1. Vernier LabQuest 2 interface2. BOD Water Sample3. Vernier Dissolved Oxygen Probe 4. 100% calibration bottle5. D.O. Electrode Filling Solution6. Wash bottle with distilled water7. Sodium Sulfite Calibration Solution8. Sample water from each site9. Pipette10. 250 mL beaker

Procedure:

Day 0

1. At each of the four sites visited, the group collected five water samples for the BOD test.

2. Each of the glass BOD sample bottles were then placed approximately 10cm below the water’s surface and kept there for 1 minute until all air bubbles were removed and the bottle was completely filled. The BOD bottle lid was secured tightly, while still submerged.

3. Each bottle was then wrapped in foil and labelled E1 to E5 and with the name of its corresponding site. The bottles were stored in ice and returned to the laboratory for testing.

4. At the laboratory, the bottles E1 to E5 were removed from the ice and the initial dissolved oxygen reading was measured using the LabQuest2 Dissolved Oxygen probe.

5. Sodium Sulphite solution was used to calibrate the LabQuest2 Probe. The probe was washed with distilled water and the readings of the samples were then taken.

6. The results were recorded in Table1 as the “initial dissolved oxygen level”.7. The BOD bottles were then placed in an incubator (dark closet) at around 27 °C for

five days.

Day 5

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8. The BOD bottles were removed from the incubator at approximately the same time of day they were placed into the incubator and the dissolved oxygen was measured following step 5.

Data Collection/Results:

Table 1 – Results of Group 1 showing the level of dissolved oxygen in samples E1 – E5 after 5 days for each site

Site Dissolved Oxygen E1 E2 E3 E4 E5 Average (BOD5) (mg/L)

A Initial (mg/L) 10.8 10.8 10.7 10.9 10.8

Final (mg/L) 3.4 3.7 3.3 3.6 3.4

BOD5 (mg/L) 7.4 7.1 7.4 7.3 7.4 7.32

B Initial (mg/L) 11.3 11.2 10.9 11.1 11.1

Final (mg/L) 5.2 4.4 4.3 4.7 4.5

BOD5 (mg/L) 6.1 6.8 6.6 6.4 6.6 6.50

C Initial (mg/L) 11.1 11.1 11.3 11.1 11.2

Final (mg/L) 3.9 3.8 3.8 3.6 3.8

BOD5 (mg/L) 7.2 7.3 7.5 7.5 7.4 7.38

D Initial (mg/L) 8.3 8.7 8.5 8.5 8.7

Final (mg/L) 2.3 2.4 2.8 2.9 2.2

BOD5 (mg/L) 6 6.3 5.7 5.6 6.5 6.02

Data Analysis:

BODE1 = Final Dissolved Oxygen (mg/L) – Initial Dissolved Oxygen (mg/L)

BOD5 = BODE 1+BODE2+BODE3+BODE4+BODE 5

5 mg/L

The results for the values of BODE1 – BODE5 and BOD5 are shown in Table1 above.

Discussion: This lab was done to determine the Biochemical Oxygen Demand of the water samples taken from each of the four coastal zones visited. In a “healthy” body of water, oxygen is replenished quicker than it’s used by aquatic organisms. However, in some bodies of water, aerobic bacteria decompose such a vast volume of organic material, that oxygen is depleted from the water faster than it can be replaced. The resulting decrease in dissolved oxygen is known as the Biochemical Oxygen Demand (BOD). Also, oxygen is vital to aquatic species as they use it to build energy through respiration. Dissolved oxygen is the form of oxygen accessible to aquatic organisms.

After testing, it was found that the average level of BOD in sites “A”, “B”, “C” and “D” was calculated to be 7.32mg/L, 6.50mg/L, 7.38mg/L and 6.02mg/L respectively. A level of BOD between 6mg/L – 9mg/L indicates that the water is contains lots of organic material and

43

bacteria. Furthermore, to prevent reductions in growth and disease resistance, the dissolved oxygen concentration in tilapia ponds should be kept at 1 mg/L. Therefore, it can be deduced that the water in the four sites “A”, “B” and “C” and “D” contained a lot of organic material and bacteria, and was not suitable for the optimum growth of tilapia and would thus reduce their ability to resist diseases.

Conclusions: The BOD5 levels of the four visited sites were investigated and determined. The BOD5 levels of the sites “A”, “B”, “C” and “D” were 7.32mg/L, 6.50mg/L, 7.38mg/L and 6.02mg/L respectively. All four sites had unacceptable BOD levels for the optimum growth of tilapia and maintaining their ability to resist diseases.

Limitations: The resources and time were limited for this experiment and thus a simple method for the calculation of BOD5 was employed. As such, to obtain a precise measure of BOD5 it should be conducted over a longer period of time period so that the changes can be better observed, thus resulting in a clear cut representation of the various levels present in the water.

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Lab: 2


Title: Temperature, pH, Nitrates, Turbidity, Salinity and Ammonium

Aim: To determine the Temperature, pH, Nitrates, Turbidity, Salinity and Ammonium level of all four sites.


1. Vernier LabQuest 2 interface2. Vernier pH Sensor3. Vernier Temperature Probe4. Nitrate Ion-Selective Electrode5. Vernier Turbidity Sensor 6. Wash Bottle7. Distilled Water 8. Sample water from each site

Procedure:

1. Water samples were collected at each of the visited sites by placing the water bottles under water for 1 minute, until all the air bubbles were removed. The lid of the bottle was then tightened quickly under water. The bottle was then labelled “Bottle A” with the name of its corresponding site. The bottles were then taken back to the laboratory for testing.

2. The laboratory technician pre-standardised each probe before testing the samples.3. Each sample was tested in succession for Temperature, Turbidity, pH, Nitrates,

Ammonia and Salinity. For each test the relevant probe was connected to the LabQuest2 interface and placed into Sample Bottle A and the reading recorded in Table 1.

4. Between each test the probes were washed and securely stored away.


Table 1 – Results showing the values obtained for pH, Turbidity, Nitrates and Temperature at the four sites

Site pH Temperature (°C)

Ammonium

NH4+ -N (mg/L)

Turbidity (NTU)

Nitrates (mg/L)

Salinity (ppt)

A 7.31 24.44 0.8 18 8.9 1.2

B 7.73 27.43 0.7 23 12.7 1.1

C 7.84 24.50 0.9 25 6.4 1.3

D 7.33 25.73 0.8 27 9.8 1.3

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Discussion: This lab was done to determine the Temperature, pH, Nitrates, Turbidity, Salinity and Ammonium level of the water samples taken from each of the four sites visited. Temperature refers to the degree of heat and is a measure of the average heat or thermal energy of the particles in a substance. Many aquatic organisms are cold blooded and have their own specific optimum temperature. The growth rate of tilapia is best between a temperature of 220C and 290C. It was determined that the temperatures of the samples of water for sites “A”, “B”, “C” and “D” were 24.440C, 27.430C, 24.500C and 25.730C respectively. These temperatures were within the range required for the standard living of tilapia and as such the temperatures were not harmful to them.

Also, aquatic organisms are extremely sensitive to the pH of their environment. The growth rate of tilapia is best between a pH of 7 – 9. If the pH of the water isn’t at this optimum range, the tilapia won’t be able to survive and reproduce and may eventually die. The pH scale ranges from 0 – 14 with a pH of 7 being neutral, a pH of less than 7 being acidic and a pH of above 7 being basic. It was found that the pH of the samples of water for each site “A”, “B”, “C” and “D” was 7.31, 7.73, 7.84 and 7.33. Thus, it can be inferred that the pH of the water of the four sites visited was relatively neutral and was appropriate for the survival and reproduction of tilapia.

Additionally, another parameter which was tested was turbidity. Turbidity refers to the measure of water’s lack of clarity. Water with high turbidity is cloudy, whereas water with low turbidity is clear. For aquatic life, turbidity levels should be less than 25 NTU. It was detected that the values of Turbidity of the samples of water for the sites “A”, “B”, “C” and “D” were 18, 23, 25 and 27 NTU respectively. With respect to sites “A”, “B” and “C”, the turbidity was within the required range and as such the water was clear, allowing light to enter which thus allowed for the growth and reproduction of tilapia. In contrast, the turbidity of coastal zone “D” was slightly higher than acceptable. This therefore indicates that there was a limitation in light penetration into the water, which may cause a decrease in the dissolved oxygen levels and can suffocate the tilapia and other aquatic organisms which live there, which may eventually result in death.

Furthermore, nitrates, NO3-, which are soluble in water, are an essential source of nitrogen required by plants and animals to synthesize amino acids and proteins. The acceptable nitrate level in water for tilapia growth is below 10 mg/L, however, toxicity only occurs at levels above 25 mg/L. This is because, above this level, there is an increase in plant growth and decay, promotion of bacterial decomposition and a decrease in oxygen levels in water, which may kill the tilapia and other aquatic organisms which live there. It was found that the Nitrate level of the samples of water for the sites “A”, “B”, “C” and “D” were 8.9mg/L, 12.7mg/L, 6.4mg/L and 9.8mg/L respectively. As such, the nitrate level of the water samples from sites “A”, “C” and “D”, were within the appropriate range. Even though the nitrate level at site “B” was slightly higher than the acceptable level, it wasn’t high enough to result in toxicity. Therefore, the nitrate level at all sites would have allowed the tilapia to grow and reproduce efficiently.

In addition, salinity was another tested parameter. Salinity is the measure of all the salts dissolved in water, and the ideal salinity for tilapia growth is 15ppt and under. It was determined that the level of salinity in the water in sites “A”, “B”, “C” and “D” was 1.2ppt, 1.1ppt, 1.3ppt and 1.3ppt respectively. As such, the salinity level of the water sample from

46

the four visited sites was within the acceptable range, thereby allowing for the optimum growth of tilapia.

Lastly, ammonium, a compound made of nitrogen and hydrogen, occurs in two forms – unionized (NH3) and ionized (NH4+). Unionized ammonia is toxic to tilapia and high levels would eventually cause death. The concentration of unionized ammonia in water for the efficient survival of tilapia should be below 0.6mg/L. However, ionized ammonia occurs in the form of ammonium and isn’t toxic to tilapia. From the results obtained, it was deduced that the ammonium level at sites “A”, “B”, “C” and “D” was 0.8mg/L, 0.7mg/L, 0.9mg/L and 0.8mg/L respectively. These values were low enough so that it would not have produced unionized ammonia as aforementioned, and thus would not be toxic to the tilapia, therefore allowing them to comfortably survive.

Conclusions: The Temperature, pH, Nitrates and Turbidity of the water from the four visited sites were investigated and determined. Sites “A”, “B”, “C” and “D” were within the required ranges for Temperature, which was 24.440C, 27.430C, 24.500C and 25.730C respectively, pH, which was 7.31, 7.73, 7.84 and 7.33 respectively and Salinity, which was 1.2ppt, 1.1ppt, 1.3ppt and 1.3ppt respectively. The turbidity level of the four site was 18, 23, 25 and 27 NTU respectively. Sites “A”, “B” and “C” had an acceptable level of turbidity whereas site “D” had a value which was slightly higher than the acceptable level. The level of Nitrates found in the four sites “A”, “B”, “C” and “D” was 8.9mg/L, 12.7mg/L, 6.4mg/L and 9.8mg/L respectively. The nitrate level of sites “A”, “C” and “D” was within the acceptable range, however, despite the level at site “B” being slightly over the acceptable range, it wasn’t high enough to be toxic to the fish. Therefore, the nitrate level at all four sites would have been appropriate for the survival of tilapia. The Ammonium level at sites “A”, “B”, “C” and “D” was 0.8mg/L, 0.7mg/L, 0.9mg/L and 0.8mg/L respectively. These levels were low and would not be toxic to the tilapia, thus allowing them to grow and reproduce efficiently.

Limitations: To obtain a specific evaluation of whether or not the water quality was ideal for the growth and survival of tilapia, these parameters should be collected over a longer period of time to allow the true levels and fluctuations to be seen.

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Lab: 3


Title: Total Solids

Aim: To determine the level of Total Solids present in the water sample collected for all four sites.


1. Analytical balance (0.001g)2. Drying oven3. Tongs4. 100mL graduated cylinder5. Four (4) 250mL beakers6. Sample water from each site

Procedure:

1. Water samples were collected at each of the visited sites by placing the water bottles under water for 1 minute, until all the air bubbles were removed. The lid of the bottle was then tightened quickly under water. The bottle was then labelled “Bottle B” with the name of its corresponding coastal zone. The bottles were then taken back to the laboratory for testing.

2. A measuring cylinder was used to measure and pour 200 cm3 of sample water from each site into each of the pre-dried and weighed 250mL beakers.

3. The beakers were placed in a drying oven at a 100 °C until the following day.4. The beakers were then removed and placed in a desiccator until they were cooled to

room temperature.5. Each beaker was weighed to determine the difference by mass.6. The results were tabulated in Table 1.


Table 1: Results showing the Total Solids present in each water sample collected at the various sites.

Site Mass of empty beaker (g)

Mass of beaker plus solids (g)

Mass of Solids (g)

Mass of Solids (mg)

Total Volume (L)

Total Solids (mg/L)

A 97.850 97.865 0.015 15 0.2 75

B 95.950 95.968 0.018 18 0.2 90

C 103.550 103.567 0.017 17 0.2 85

D 96.995 97.011 0.016 16 0.2 80

Discussion: This lab was done to determine the level of Total Solids present in the water samples taken from each of the sites visited. Total Solids is a measure of all the suspended,

48

colloidal, and dissolved solids in a sample of water. It was detected that the level of Total Solids of the samples of water for the four sites “A”, “B”, “C” and “D” were 75, 90, 85 and 80 respectively. As such, it can be inferred that all four sites contained a high level of suspended, colloidal and dissolved solids. This may endanger the tilapia live there since a high level of Total Solids causes a decrease in the photosynthetic rate and also reduces water clarity.

Conclusions: The levels Total Solids present in the four visited sites were investigated and determined. The levels of total solids of sites “A”, “B”, “C” and “D” were 75, 90, 85 and 80 respectively. All sites contained high levels of total solids which would endanger the tilapia and other aquatic organisms which live there.

Limitations: To obtain a specific evaluation of whether or not the water quality was ideal for the growth and survival of tilapia, the level of Total Phosphates should have been tested for over a longer period of time to allow the true levels and fluctuations to be seen.

49

Lab: 4


Title: Total Phosphates

Aim: To determine the level of Total Phosphates in the water sample collected for all four sites.


1. Sample water from each site2. 0.1M HCl3. LabQuest 2 Interface 4. 2.63 M H2SO45. Vernier Colourimeter 6. 10 mL graduated cylinder7. Phosphate Standard (10.0 mg/L PO4)8. 25 mL graduated cylinder9. one cuvette 10. four 50 mL Erlenmeyer flasks11. 5.0 M NaOH 12. Hot plate13. PhosVer 3 Phosphate Powder Pillow14. Distilled Water15. Sulphate Powder Pillows

Procedure:

1. Water samples were collected at each of the visited sites by placing the water bottles under water for 1 minute, until all the air bubbles were removed. The lid of the bottle was then tightened quickly under water. The bottle was then labelled “Bottle C” with the name of its corresponding site. The bottles were then taken back to the laboratory for testing.

2. A 25mL graduated cylinder was used to measure and place 25 mL of sample water from each site into each flask.

3. Water samples from each facility were mixed as follows –a) One Sulphate powder pillow was added to each flask and swirled.b) A 10mL graduated cylinder was used to measure and add 2.0 mL of 2.63M

H2SO4 to each flask swirled.c) The samples were boiled for 30 minutes while adding small amounts of distilled

water to keep the volume near, but not above 25mL.d) After 30 minutes, the flasks were removed from the hot plate and allowed to cool.e) A 10mL graduated cylinder was used to add 2.0mL of 5.0 M NaOH to each flask

and swirled to neutralise the acid.f) If a flask contained below 25 mL of liquid, the volume was made up to 25mL

using distilled water.g) One PhosVer3 Phosphate Powder Pillow was added to each sample and

completely dissolved prior to reading on the colourimeter.

50

4. The phosphate standards and standard curve was already done for us by the University of Trinidad and Tobago and stored on the LabQuest2 interface for use in the determination of our sample readings. The data was tabulated in Table 1.

5. An empty cuvette was filled ¾ full with distilled water and the lid was sealed to prepare a blank.

6. The blank was then placed into the vernier colourimeter and the blank button was clicked on the interfaced.

7. The cuvette was washed after each reading and the samples for each site was then read on the colourimeter and tabulated in Table 2.


Table 1 – Results showing the Standards Absorbance ReadingsFlask Number 10.0 mg/L

PO4 (mL)Distilled H2O (mL) Concentration

(mg/L PO4)Absorbance

1 5 20 2 0.34142 10 15 4 0.7373 15 10 6 0.8444 20 5 8 1.179

Table 2: Results Showing the Absorbance values for the various SitesSite Absorbance Total Phosphates Concentration

(mg/L) PO4Total Phosphorus Concentration (mg/L- PO4)

A 0.4011 2.35 0.768B 0.7903 4.63 1.513C 0.2270 1.33 0.435D 0.3619 2.12 0.693

Discussion: This lab was done to determine the level of Total Phosphates present in the water samples taken from each of the four sites visited. Minute amounts of phosphorus are required for all aquatic plants and algae as it is a vital nutrient to these species. An excess amount results in eutrophication, the condition whereby there’s an excessive richness in nutrients, which results in increased plant and algal growth. Eutrophication lowers the levels of dissolved oxygen in the water and makes the water uninhabitable by many aquatic organisms, including tilapia.

It was found that the values for the concentration of the Total Phosphates present in the samples of water for sites “A”, “B”, “C” and “D” was 2.35mg/L, 4.63mg/L, 1.33mg/L and 2.12mg/L respectively. These values were relatively low and as such it would not result in eutrophication, thus allowing tilapia and other aquatic organisms to live there easily.

Data Analysis:

Calculation of Phosphorus –

Phosphorus (mg/L PO4-P) = phosphates(mg / L PO 4)

3.06

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Conclusions: The level Total Phosphates present in the four sites was investigated and determined. The levels of total phosphates of sites “A”, “B”, “C” and “D” were 2.35mg/L, 4.63mg/L, 1.33mg/L and 2.12mg/L respectively. All four sites zones contained acceptable levels of total phosphates.

Limitations: To obtain a specific evaluation of whether or not the water quality was ideal for the growth and survival of tilapia, the level of Alkalinity should have been tested for over a longer period of time to allow the true levels and fluctuations to be seen.

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Lab: 5


Title: Alkalinity

Aim: To determine the Alkalinity of the water samples collected for all four sites.


1. Sample water from each site (B1) 2. 100 mL graduated cylinder3. Methyl Orange4. Wash bottle with distilled water5. Conical Flask 6. 0.00100 M H2SO4 solution (A1)7. 50 mL burette8. 25 cm3 pipette9. Three 250 cm3 conical flasks

Procedure:

1. Water samples were collected at each of the visited sites by placing the water bottles under water for 1 minute, until all the air bubbles were removed. The lid of the bottle was then tightened quickly under water. The bottle was then labelled “Bottle D” with the name of its corresponding site. The bottles were then taken back to the laboratory for testing.

2. A1 (H2SO4) was then placed in a burette3. 25 cm3 of B1 was then pipetted into a conical flask and two drops of methyl orange

indicator was added.4. This solution was titrated with A1 until it changed colour from yellow to orange/red.5. Readings were then recorded in Table 1.6. The concentration of Alkalinity was determined assuming the following reaction –

H2SO4 + CaCO3 →H2O + CO2 + CaSO4


Table 1: Results showing the Titration of B1 with A1 at the various sitesSite A B C DFinal burette reading / cm3 6 13 20 32Initial burette reading / cm3 0 6 13 20Volume of A1 used / cm3 6.1 6.6 7.2 12.0

Table 2: Results showing the Alkalinity level of the various sitesSite Alkalinity (mg/L)A 33B 36C 39D 31

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Discussion: This lab was done to determine the level of Alkalinity present in the water samples taken from each of the four sites visited. Alkalinity refers to the measure of how much acid water can neutralize. Alkalinity acts as a buffer as it protects water and its life forms from immediate changes in pH. In order for tilapia to survive, the Alkalinity level should be maintained between 100 to 250 mg/L. However, it was found that the values for the level of Alkalinity present in the samples of water for sites “A”, “B”, “C” and “D” were 33mg/L, 36mg/L, 39mg/L and 31mg/L respectively. Thus the Alkalinity level at all four sites was relatively low and as such the water, the tilapia and the other aquatic organisms which live there will be highly affected by changes in pH.

Data Analysis:

M1V1 = M2V2

M1 = 0.001 Molar H2SO4

V1 = Volume of H2SO4 titre into the conical flask

M2 = Concentration of CaCO3

V2 = 25 ml

Molar Concentration of CaCO3 (mol dm-3) to Mass Concentration of CaCO3 (g dm-3)

g/dm−3 ofCaC O3=M 2

136

¿mg /dm−3=M 2

136 ×1000

Conclusions: The level of Alkalinity present in the four sites were investigated and determined. The Alkalinity levels of sites “A”, “B”, “C” and “D” were 33mg/L, 36mg/L, 39mg/L and 31mg/L respectively. All sites contained an Alkalinity level which was below the acceptable range; as a result, this may lead to the death of the tilapia and other aquatic organisms which live there.

Limitations: To obtain a specific evaluation of whether or not the water quality was ideal for the growth and survival of tilapia, these parameters should be collected over a longer period of time to allow the true levels and fluctuations to be seen.

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Lab: 6


Title: Bacterial Concentration

Aim: To determine the amount of E. Coli present in the tilapia pond


1. 2 sterile sample tubes2. Autoclave3. 2 bottles of Total Count (TC)4. Bleach5. 2 bottles of Coliscan Easygel 6. Waterproof marker7. 4 pretreated petri dishes8. Masking tape or parafilm9. 2 sterile 3 mL pipettes

Procedure:

Day 1: Collection of Water Samples

1. A waterproof marker was used to label two sterile sample tubes with the site name, date, and time of collection.

2. The sample water was collected using a sterile technique.a) The top of the sterile sample tube was opened or the cover was gently peeled off of a

sterile pipette from the bulb end.b) The sample tube was immersed or the pipette was tipped 5–8 cm below the surface to

collect the sample in the flowing portion of the pond. If a dropper was used, the top of a sterile sample tube was gently opened and the sample was pipetted into the tube. Note: it was ensured that the person collecting the sample was standing downstream from the sample.

c) The cap was carefully placed back on the sample tube; touching the sample was avoided.

3. Step 2 was repeated for the second sample.4. Two bottles of Total Count (TC) Easygel® and two bottles of Coliscan Easygel®

were obtained.5. Each bottle was labelled with the site name and date of sample.6. Four pretreated sterile petri dishes were obtained and each petri dish was labelled

with the culture type, site name, date, and volume of sample.7. Using sterile technique, the appropriate volume of water was transferred from the

sample tubes into the bottles of TC Easygel® and Coliscan Easygel®. Note: Proper sample amount for inoculation depended on the level of contamination of the water source. Recommended volumes were 0.1–0.5 mL for TC medium and 1.0–5.0 mL for Coliscan medium.

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8. Using sterile technique, the bottles were gently swirled to distribute the sample in the medium.

9. Each bottle of medium was opened and poured into the correctly labeled petri dishes. The lids were placed back on each of the petri dishes immediately.

10. The petri dish was gently swirled in a circular motion to evenly distribute the media on the bottom of the dish.

11. The plates were allowed to sit undisturbed in order to allow the media to gel. This took 45–60 min.

12. Steps 4–11 were repeated for the remaining samples.13. Once the media was gelled, the petri dishes were stacked upside down and

incubated for 24 hours at 35°C. If no incubator was available, the dishes were placed in a warm area in the room and covered with a towel. The dishes were incubated at room temperature for 30–48 hours. Note: The petri dishes were stacked upside down before they were incubated.

14. Day 2: Counting Colonies and Calculations15. When the petri dishes were incubated for at least 24 hours, they were removed from

the incubator. The dishes were kept upside down so condensation that was formed on the lid did not drip onto the culture. Note: If dishes were incubated at room temperature, they were incubated for 30–48 hours. Plates were not counted past 48 hours.

16. While the plate was upside down, the colonies on the Total Count dish were counted. Very small or “pin-point” colonies (smaller than a period) were not counted. Note: It was easier to count a quarter or a half of the culture and then multiply to get an estimated colony count.

17. The number of colonies on the Total Count dish was recorded in Table 1.18. All the purple colonies on the Coliscan dish were counted. Any white or light blue

colonies were not counted. Again it was ensured that the plate was upside down and pin-point colonies were not counted.

19. The number of purple colonies as E. coli colonies was recorded in Table 1.20. All the red, pink, and purple colonies on the Coliscan dish were counted. Any white

or light blue colonies were not counted. It was ensured that the plate was upside down and pin-point colonies were not counted.

21. The number of red, pink, and purple colonies as coliform colonies was recorded in Table 1.

22. Steps 15–20 were repeated for the second sample collected.

Calculations:

1. The equation below was used to determine the concentration of bacteria per 100 mL for each sample collected. The values were recorded in Table 2.

2. Once the concentrations were calculated for each sample, the two values were averaged together to determine the average concentration of bacteria per 100mL. The average values were recorded in Table 2.

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A dilution factor of 1:6 was made as 1:1 to 1:5 resulted in Too many to Count (TMC) for each plate. Adjustments were made prior by the technician who advised a 1:8 dilution be used.

Table 1: Results showing the Total Colonies of each siteSite Medium type Inoculation

volumeTotal count Coliscan – red,

pink, & purple (coliforms)

Coliscan – purple (E. colt)

1

Count for Sample 1

1 167 103 64

Count for Sample 2

1 177 108 69

Average 172 105.5 66.5

2

Count for Sample 1

1 180 107 73

Count for Sample 2

1 184 112 72

Average 182 109.5 72.5

3

Count for Sample 1

1 185 110 75

Count for Sample 2

1 187 114 73

Average 186 112 74

4

Count for Sample 1

1 197 113 84

Count for Sample 2

1 201 123 78

Average 199 118 81

Table 2: Results showing the Colonies per 100 mL of WaterMedium type Site 1 Site 2 Site 3 Site 4 Average

(colonies/100 mL)

Total count 172 182 186 199 1.85E+08Coliscan – purple (E. coli)

66.5 72.5 74 81 7.35E+07

Coliscan – red, pink, & purple (coliforms)

105.5 109.5 112 118 1.11E+08

Total Coliform /100 ml per site

8.60E+07 9.10E+07 9.30E+07 9.95E+07

Discussion: This lab was done to determine the amount of E. Coli present in the water samples taken from each of the four sites visited. E-coli is a form of faecal coliform which

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originates from the faeces of humans or animals. It is an indication of the level of pollution in a tilapia pond because coliforms are not the normal flora of bacteria in fish. Even though it doesn’t not directly harm the tilapia, it can harm persons who consume the infected fish. It was found that the total coliform per 100mL of sites “A”, “B”, “C” and “D” was 8.60E+07, 9.10E+07, 9.30E+07 and 9.95E+07 respectively. These values were similar and relatively high, thus indicating that the pond in general was highly polluted. Even though the tilapia may survive in the pond, if they are consumed by humans, it may result in infections and illness.

Conclusions: The level of E-Coli, a form of Faecal Coliform, present in the four sites were investigated and determined. The Faecal Coliform per 100mL levels of sites “A”, “B”, “C” and “D” were 8.60E+07, 9.10E+07, 9.30E+07 and 9.95E+07 respectively. Tilapia may survive with these levels, however if they are consumed by humans, it may result in health issues to the persons.

Limitations: To obtain a specific evaluation of whether or not the water quality was ideal for the growth and survival of tilapia, the level of E-Coli should have been tested for over a longer period of time to allow the true levels and fluctuations to be seen.

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CAPE Environmental Science IA Unit 2

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