Heavy Metal and Microbial Analyses of Janitor Fish (Pterygoplichthys spp.) in Laguna de Bay, Philippines

Journal Journal of Environmenta Environmentall Science and and Management Management 9(2):31-40 9(2):31-40 (December (December 2006 ) ISSN 0119-1144 0119-1144

Heavy Metal and Microbial Analyses Analyses of Janitor Fish (Pterygoplichthys spp.) in Laguna de Bay, Philippines Hannibal M. Chavez, Elvira A. Casao, Eunice P. P. Villanueva, Villanueva, Madeleine P. P. Paras, Marites C. Guinto and Marilou B. Mosqueda Abstract Janito Janitorr fish fish (Ptery (Pterygop goplic lichth hthys ys spp.) spp.) and water water sam sample pless were were obtaine obtained d from the the three three samplin sampling g stations in Laguna de Bay (central, east and west bay) for heavy metal and microbial analyses during the dry and wet season. Results revealed that cadmium and chromium were not detected in the water samples. Copper concentration of water samples during the dry season in Taguig for west Bay (0.0767 mg/L) and Jala-jala for central Bay (0.097 (0.097 mg/L) exceeded the limit of 0.05 mg/L for Class C waters. The fish flesh obtained from the three sampling stations had lead concentration ranging from from 0.0573 0.0573mg mg/kg /kg to to 0.1900 0.1900 mg/kg mg/kg (we (wett weight weight). ). Arsen Arsenic, ic, cadm cadmium ium,, chromi chromium um and and mercur mercuryy in fish fish fles flesh h wer weree not not dete detect cted ed duri during ng the the dry dry seas season on,, but but pres presen entt at low conce concent ntra rati tion onss durin during g the the wet wet seas season on.. The total bacterial and coliform count of water samples differed in the three sampling stations. The total bacterial count in fish flesh in the three sampling stations were 800 to 5,650,000 cfu/g during the wet season and from 200,000 to 2,230,000 cfu/g during the dry season. Coliform were present in all sampling stations (22 to >1,600MPN/g). Pterygoplichthys spp. introduced introduced species, heavy heavy Keywords : Laguna de Bay, janitor fish, Pterygoplichthys metal concentrations, microbial analyses

INTRODUCTION

Laguna de Bay, comprising a total area of 90,000 ha is considered the second largest lake in Southeast Asia. The most important use of Laguna de Bay is its Lag una Lake Development Devel opment fishery resource ( Laguna Authority Authority 1974). The Laguna de Bay watershed area has 5,009 industrial and agricultural establishments whose wastes directly or indirectly empty into the lake (LLDA 2005). Heavy metals are among the waste products discharged into the lake. The increasing input of wastes from industries and domestic sources, agricultural run-off and soil erosion in the watershed contribute to the rapid decline in lake’s water quality. Likewise, the concentrations of heavy metals and sediments in Laguna de Bay and some tributary rivers show some signs of industrial pollution (LLDA 1987; Barril 1990; LLDA 2005). Microbial contamination of the lake has exceeded the prescribed limit for Class C waters (Barril 1990).

Two species of janitor fish ( Pterygoplichthys parda pardalis lis and Pterygoplichthys disjunctivus ) which initially thrived in the lake due to escapement from ponds had an impact on the environment which favored their establishment. The complex environmental problems of the lake, particularly increasing wasteloads from industrial activities, increasing nutrient wasteloads from domestic households, expanded agricultural and livestock production and intensive fish pen operations favored the growth and proliferation of these species. Their proliferation can be attributed to the following: their ability to tolerate poor water quality, easily adaptable to even the harshest conditions, and being omnivores and bottom feeders as they can eat any food available in the environment. In 2002, LLDA reported that janitor fish comprised 10-38% of the total fish corral catch in Siniloan, Laguna.

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Heavy metal and microbial analyses of Janitor Fish (Pterygoplichthys spp.) in Laguna de Bay, Philippines

At present, a significant population of janitor fish has been observed by the fishermen along the shorelines of Laguna de Bay (Siniloan, Jala-Jala, Binangonan and Taguig) and along the Marikina river. The rapid increase of this species has affected the livelihood and fishing operation of the fisherfolk which led to a decrease in marketable catch of endemic and commercial fish species due to its predominance in gill net and fish corral catch. Some fishermen have even tried to cook and eat the fish not knowing its adverse effect on their health. The determination of heavy metals and microbial content of janitor fish and water, would aid in the evaluation of the effect of the environment on the janitor fish. Results of the study are essential in determining seasonal variation of heavy metal concentrations and microbial content in fish and water; and in ascertaining whether the concentration of heavy metals and microbial content of janitor fish is within acceptable limits for human consumption and its wise utilization.

These sites were selected due to the presence and proliferation of janitor fish. Samples of janitor fish and water were obtained from the study sites from March to May 2004 for the dry season and July to November 2004 for the wet season.

MATERIALS AND METHODS

Water Samples

Three sampling stations covering four sites were established in Laguna de Bay. After a preliminary investigation of the area, the sampling sites chosen were Siniloan, Laguna for east bay, Binangonan, Rizal and Taguig, Metro Manila for west bay and JalaJala, Rizal for central bay (Figure 1).

Physico-chemical Parameters

The determination of physico-chemical parameters such as air and water temperature, water depth, turbidity, pH, nitrite, dissolved oxygen and salinity was done in situ in each sampling site. Temperature was measured using a laboratory thermometer, turbidity using a Secchi disk, pH using a pH meter and nitrite using a Hack kit. The salinity measurements were done using a refractometer and dissolved oxygen was measured using a YSI D.O. Meter. Heavy Metals

One liter water samples were collected using a Kemmerer water sampler. Surface water samples below 20 cm were obtained. Middle and bottom samples were collected from the water column and near the lake bottom, respectively. Water samples were kept in a refrigerator at 4oC after acidification with 1.5 ml nitric acid. Fish Samples

Live janitor fish samples 50 g to 1550 g size for the dry season and 100 g to 560 g size for the wet season were caught in the fish corral from the four sampling sites. Ten samples of fish per site were degutted, fish flesh were removed and ground using an osterizer. A 300 g homogenized fish flesh was taken for three replicates, and refrigerated until frozen. The frozen fish flesh and acidified water samples were brought to University of the Philippines - Natural Science Research Institute (UP-NSRI), Research and Analytical Service Laboratory in Diliman, Quezon City for heavy metal analyses using the methods in Table 1. Figure 1. Sampling sites of the study.

Journal of Environmental Science and Management Vol. 9. No. 2 (December 2006) Table 1. Methods of analysis for metals in water & fish. Metals Water a. Arsenic

b. Cadmium & Lead c. Chromium, Copper & Zinc d. Mercury

Fish a. Arsenic

b. Cadmium, Chromium, Copper, Lead & Zinc c. Mercury

Methods of Analysis

Atomic Absorption Spectrometry, by Hydride Generation (APHA et al. 2001) Anodic Stripping Voltametry (APHA et al, 2001) Atomic Absorption Spectrometry, by Flame (APHA et al. 2001) Atomic Absorption Spectrometry, by Cold Vapor Technique (APHA et al. 2001) Atomic Absorption Spectrometry, by Hydride Generation (APHA et al. 2001 & AOAC 2002) Atomic Absorption Spectrometry, by Flame (APHA et al. 2001 & AOAC 2002) Atomic Absorption Spectrometry, by Cold Vapor Technique (Bouchard 1973)

Microbial Analyses Water and Fish Samples

One hundred ml water samples collected from the surface of the four sites during the dry and wet season were kept cool and brought immediately to the South Harbor Laboratory for microbial analyses. The fish samples were brought immediately to the South Harbor Laboratory for microbial analyses. A 200 g homogenized flesh sample per sampling station for two replicates was used for the analyses. Microbial analyses of water samples included total bacterial count (TBC), total coliform count, and E.coli. For fish flesh samples, microbial analyses included total bacterial count, total coliform, S. aureus, E. coli, Salmonella and Shigela based on the procedures described by U.S. Food and Drug Administration (1995). Statistical Analysis

Kruskal-Wallis Test was used to determine the significant differences in the concentrations of heavy metals in water, fish flesh and physico-chemical parameters among the four sampling sites in relation to seasonal variation (dry and wet season) using the statistical package, SPSS version 11.5. RESULTS

Heavy Metals in Water Table 2 presents the mean concentrations of heavy metals (arsenic, cadmium, chromium, copper,

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lead, mercury, and zinc) in the water samples. Cadmium and chromium were not detected in the water samples collected in the four sites during the dry and wet season. Arsenic, mercury, zinc and lead, concentrations although detected, were still within the limit set by Department of Environment and Natural Resources Administrative Order No. 34. (1990). Copper concentration of water samples (0.0767 mg/L and 0.097 mg/L) during the dry season and (0.13 mg/L and 0.0767 mg/L) during the wet season in Taguig and Jala-Jala , respectively, exceeded the limit of 0.05 mg/L for Class C waters. Low concentrations of copper during the dry and wet season was observed in Siniloan (0.033mg/L and 0.0274mg/L) and Binangonan (0.026mg/L and 0.0127mg/L), respectively. The comparison of concentrations of heavy metals in water samples among the four sampling sites during the dry and wet season is shown in Table 3. During the dry season, the four sampling sites had significant differences in lead concentration in the water (P<0.05). The concentrations of arsenic, cadmium, chromium, copper, lead, mercury, and zinc in the water during the wet season were not significantly different among the four sampling sites (P>0.05). Heavy Metals in Fish

The most dominant fish caught in the fish corrals were janitor fish. During the dry season, almost all of the fish samples collected were gravid females with eggs. Table 4 shows the mean concentrations of heavy metals in janitor fish. Arsenic, cadmium, chromium and mercury were not detected during the dry season. However, during the wet season, these heavy metals were detected at low concentrations. Lead concentration in fish flesh collected in the four sites during the dry season ranged from 0.0600 mg/kg to 0.1900 mg/kg (wet weight). The concentrations were slightly higher than fish flesh collected during the wet season with values of 0.0573 mg/kg to 0.0933 mg/kg (wet weight) which were below the standard limit set by Fisheries Administrative Order No. 210 (2001). The comparison of concentrations of heavy metals in fish flesh among the four sampling sites during the dry and wet season is shown in Table 5. Results showed that there was a significant difference in the concentration of zinc in fish flesh among the four


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Table 2. Mean concentrations of trace metals in water samples collected during the wet and dry season in the east, west and central bays of Laguna de Bay. Sampling Stations/Sites

As, mg/L

1. East Bay Siniloan 2. West Bay Binangonan Taguig 3.Central Bay Jala-jala

Cu, mg/L

Pb, mg/L

Hg, mg/L

Zn, mg/L

Dry

Wet

Dry

Wet

Dry

Wet

Dry

Wet

Dry

Wet

0.00127

0.00067

0.033

0.0274

NDb

ND

ND

ND

0.583

0.0227

0.0026 0.0032

0.0016 0.00073

0.026 0.0767

0.0127 0.13

NDb 0.017a

0.00197 0.0267

ND 0.00053

0.000253 ND

0.0503 0.096

0.0453 0.1377

0.0037

0.0005

0.097

0.0767

NDb

0.01

0.0003

0.0001

0.12

0.0807

*Standard for Class C Waters mg/L

0.05

* DAO No. 34. 1990

0.05

ND – Not Detected

0.05

0.002

2.0

ND for Cd and Cr

Table 3. Comparison of concentrations of heavy metals in water samples among the four sampling sites during the dry and wet season. Heavy Metals

p – value *

As Cd Cr Cu Pb Hg Zn

.149 1.0 1.0 .785 .013 .138 .772

* - using Kruskal-Wallis Test

Dry season Significance at P<0.05 ns ns ns ns s ns ns

s - significant

p – value * .522 1.0 1.0 .227 .417 .530 .574

Wet season Significance at P<0.05 ns ns ns ns ns ns ns

ns - not significant

Table 4. Mean concentrations of trace metals in janitor fish samples (mg/kg wet wt.) collected during the wet and dry season in the east, west and central bays of Laguna de Bay. Sampling Stations/Sites 1. East Bay Siniloan 2. West Bay Binangonan Taguig 3.Central Bay Jala-jala

As,mg/kg

Cr,mg/kg

Cu,mg/kg

Pb,mg/kg

Hg,mg/kg

Zn,mg/kg

Dry

Wet

Dry

Wet

Dry

Wet

Dry

Wet

Dry

Wet

Dry

Wet

ND

0.0024b

ND

0.0400

0.2800

0.2823c

0.1800

0.0860

ND

0.0050

8.5700b

8.1000

ND ND

0.0070a 0.0051a

ND ND

0.0557 ND

0.3633 0.2900

0.3423b 2.6333a

0.0600 0.1567

0.0573 ND

ND ND

0.0157 ND

8.3467b 6.0900c

6.8667 7.6670

ND

0.0017b

ND

ND

0.4067

1.9000a

0.1900

0.0933

ND

ND

10.0667a

8.0333

*Standard mg/ kg (wet wt.)

**

* FAO No. 210. 2001

**

**

** No standard limit established

0.5

0.5

**

ND for Cd

Table 5. Comparison of concentrations of heavy metals in janitor fish flesh among the four sampling sites during the dry and wet season. Dry season p – value *

Heavy Metals As Cd Cr Cu Pb Hg Zn * - using Kruskal-Wallis Test

1.0 1.0 1.0 .152 .458 1.0 .033 s - significant

Wet season Significance at P<0.05 ns ns ns ns ns ns s ns - not significant

p – value * .024 1.0 .269 .017 .289 .172 .231

Significance at P<0.05 s ns ns s ns ns ns

Journal of Environmental Science and Management Vol. 9. No. 2 (December 2006)

sampling sites during the dry season (P<0.05). However, there were no significant differences in the concentrations of arsenic, cadmium, chromium, copper, lead, and mercury (P>0.05). During the wet season, the four sampling sites had significant differences in the concentrations of arsenic and copper (P<0.05) but none in the concentrations of cadmium, chromium, lead, mercury and zinc in fish flesh (P>0.05). Microbial Analyses in Water and Fish

Results of the microbial analyses of water are presented in Table 6. The total bacterial count of water samples differed in the four sites. The highest bacterial count during the wet season was recorded in Siniloan and Jala-Jala (251,000 cfu/100 ml). Low bacterial count (1,343 cfu/100 ml and 1,553 cfu/100 ml) during the dry season was recorded in Binangonan and Jala-jala, respectively. E. coli was high in JalaJala (4.25 MPN/100 ml) and Siniloan (5.4 MPN/100 ml) during the dry season. Table 7 shows the microbial load of janitor fish flesh collected during the dry and wet season in the four sampling sites. The total bacterial count in fish flesh during the dry season ranged from 200,000 to 2,230,000 cfu/g and during the wet season ranged from 800 to 5,650,000 cfu/g, respectively. The highest total bacterial count obtained in the fish flesh samples collected from Jala-Jala, Taguig, and Siniloan during the wet season exceeded the standard limit of 500,000 cfu/g. S. aureus was significantly high during the wet season in Jala-Jala, Siniloan and Taguig. The total count exceeded the limit of 1,000 cfu/g. Coliform were present in all sampling stations (22 to >1,600 MPN/ g). Salmonella (absent in 25 g) were recorded in Siniloan, Binangonan, Taguig and Jala-Jala during the dry season. Shigela was positive in Siniloan.

The results of microbiological analyses of fish flesh samples during the wet season revealed that most of the parameters analyzed were above the standard limits set by the International Commission on Microbial Specifications for Foods (1986). Physico-chemical Parameters Table 8 presents the mean values of physicochemical parameters in the central, east and west bay

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of Laguna de Bay. The highest water depth was recorded during the wet season in Binangonan (3.2 m) and the lowest was observed in Siniloan (0.4 m) during the dry season. Water transparency and temperature ranged from 20 cm to 50 cm and 25.5 ºC to 32.2 ºC in the four sampling sites, respectively. Comparison of water parameters among the four sampling sites is shown in Table 9. During the dry season, there were significant differences in pH, dissolved oxygen and salinity among the four sampling sites (P<0.05) and no significant difference in NO 2. The dissolved oxygen, salinity and NO2 had no significant difference (P>0.05) during the wet season. DISCUSSION Heavy Metals in Fish and Water

The adverse effects of heavy metals in the aquatic environment has been well-documented in the literature. The ability of algae to accumulate large quantities of heavy metals has been reported. Previous studies on the kinetics of heavy metal accumulation by algae showed uptake to be an extremely rapid phenomenon (Jennett et al.1983). Another significant source of increased metal levels in fish is metalcontaminated diet. Planktons which serve as natural food of the fishes have a tendency to accumulate metals in the system (Madamba and Pamulaklakin 1994). The heavy metals predominantly present from industrial activities, domestic households, agricultural and livestock production empty into the lake in the form that can readily be assimilated by phytoplankton, other aquatic plants and organisms which could result to higher metal uptake. Thus, the metal concentration in the water is a significant source of increased metal levels in fish (Relon 1996). The concentration of heavy metals in janitor fish shows that as an omnivore and bottom feeder, their heavy metal uptake comes mostly in the food they eat which can easily be absorbed through water and in the environment they inhabit. Bernard and Andreae (1984) reported that the largest concentration of heavy metals was found in omnivorous fish, followed by herbivorous and carnivorous. According to Spehar et al. (1979), phytoplankton-feeding fishes had higher copper and zinc levels than the fish preying on invertebrates. The


36

Table 6. Mean microbial load of water samples collected during the dry and wet season in the central, east and west bay of Laguna de Bay. EAST BAY Siniloan Dry Wet 93,750 TNTC 730 >1,600 5.4 Negative

PARAMETERS Total Bacterial Count cfu/100ml Total Coliform, MPN/100ml E. coli, MPN/100ml

WEST BAY Binangonan Taguig Dry Wet Dry Wet 1,343 100,000 22,575 217,000 129 <1.8 920 110 Negative Negative 11 <1.8

CENTRAL BAY Jala-Jala Dry Wet 1,553 251,000 525 350 4.25 <1.8

Table 7. Mean microbial load of janitor fish flesh collected during the dry and wet season in the central, east and west bay of Laguna de Bay. EAST BAY Siniloan

PARAMETERS

Dry

WEST BAY Binangonan

Wet

CENTRAL BAY Jala-Jala

Taguig

Dry

Wet

Dry

1,465,000

223,500

800

200,000

2,290

850

35

Wet

Dry

Wet

1,650,000

278,500

5,560,000

500,000

1,400

6,400

1,365

1,155

1,000

9.1

Negative

<1.8

11

>1,600

4

Total Bacterial Count cfu/g S. aureus, cfu/g

2,230,000

E.coli, per g

Negative

Positive

2

Negative

Negative

Total Coliform, MPN/g

>1,600

>1,600

>1,600

22

350

absent in 25g

Negative

absent in 25g

Negative

absent in 25g

-

Salmonella

absent in 25g

Shigela

Positive

Negative

Negative

Negative

Negative

-

Negative

650

STANDARD LIMIT*

>1,600

>1,600

-

absent in 25g

Negative

*International Commission on Microbial Specification for Food (ICMSF), 1986

Table 8. Mean values of physico-chemical parameters of east, west and central bays of Laguna de Bay during the dry and wet season. East Bay Siniloan

Parameters

West Bay Binangonan

Central Bay Jala-Jala

Taguig

Water depth (m) Water Transparency Air Temperature

Dry 0.4 32 26.6

Wet 1.2 35 26

Dry 2.25 50 30.2

Wet 3.2 45 27

Dry 1.5 37 27.5

Wet 2.5 48 23

Dry 1.7 34 30.1

Wet 2.4 20 23

Water Temperature pH

27.6 6.75

31 8.25

28.8 7.75

30.5 8.25

29.7 7.75

26 7.75

32.2 7.75

25.5 7.75

D.O. mg/L NO2 mg/L Salinity, g/L

2.03 0.068 0

9.05 0 0

6.85 0.022 2

6.47 0 0

6.78 0 2

6.5 0 0

4.28 0 2

7.3 0 0

Table 9. Comparison of the physico-chemical parameters in water during the dry and wet season collected in the four sampling sites. Water Parameters

Dry season

pH

.012

Significance at P<0.05 s

D.O.

.086

ns

.129

ns

NO2 Salinity

.041 .012

s s

1.0 1.0

ns ns

* - using Kruskal-Walis Test s - significant ns – not significant

p –value*

Wet season p –value* .012

Significance at P<0.05 s


pathway of the accumulation of mercury in the fish, is probably via the food chain (Hasselrot and Gothberg 1974; Bebbington et al. 1977). The environmental condition of Laguna de Bay provides a good habitat for janitor fish. According to Chavez et al. (2006), news reports state that janitor fish proliferating in the waters of Laguna de Bay was being blamed for the decrease in the commercial marketable fish catch from the lake. This nonindigenous species is a major economic, environmental and health concern in the 21st century (http:// www.science.hq.nasa.gov). Invasive species may compete with and replace native species resulting to degradation of the environment and decline in production. Invading species have undoubtedly been responsible for the decline of native species and an invader can cause major alterations to fish communities (Moyle 1998). The above findings of the water samples were below the levels reported by the LLDA. According to the report, the cadmium concentration in January and April 1998 exceeded the criterion of 0.01 mg/L in all lake stations. Lead concentration exceeded by 0.05mg/L in October 2000 in the four lake stations but decreased the following quarter (LLDA 2005). Tables 11 and 12 show the data and values of the different water quality parameters. A high significant negative correlation of temperature with copper and significant negative correlation of dissolved oxygen with lead was observed. The transparency readings had positive correlation with copper and highly significant negative correlation with lead during the dry season.

During the wet season, temperature and pH had high significant positive correlations with chromium and mercury and has high negative correlation with copper. The high positive correlation of transparency with arsenic and inverse correlation with lead and zinc maybe attributed to suspended particles in the water column. Dissolved oxygen had a significant positive correlation with lead and zinc and had a negative correlation with arsenic. High dissolved oxygen favors the formation of iron-hydroxides that seems to be the main sinks for heavy metals such as copper, chromium, lead and zinc (Houba et al. 1983). Heavy metals are known to adhere to suspended particles (Salim

37

1983), thus settling of these particles results in lower levels of heavy metals in the water.

In this study, the levels of heavy metals in water and fish were within acceptable limits. However, heavy metals are not only acutely toxic but also cumulative poisons. Cadmium and lead are recognized as toxic metals and incidences of poisoning from environmental pollution and clinical symptoms are well known (Madamba and Pamulaklakin 1994). Copper and zinc are basically essential, but these become toxic in excessive amounts. Although the concentrations of heavy metals in janitor fish were quite low, these should not be ignored. Sublethal doses of heavy metals are known to have a number of physiological and genetic effects on several species of fish (Cuvin-Aralar 1989). . Microbial Content of Water and Fish The highest bacterial count in the water and fish flesh was greatly influenced by the seasonal variation (dry and wet season) in the central, east and west bay of Laguna de Bay. The highest total bacterial count in fish flesh was obtained in the samples collected from Jala-Jala, Taguig, and Siniloan during the wet season, which exceeded the standard limit of 500,000 cfu/g. The rapid increase in total bacterial count during the wet season maybe attributed to the contamination during the rainy days’ run-off and flushing of domestic and agro-industrial wastes coming from the watershed. Barril and Tumlos (1997) reported that coliform bacterial population in the lake had exceeded the criteria for Class C waters by 200-fold. The high microbial counts were attributed to the high population pressure in the area and the contamination of the water with human, animal and industrial wastes (Sanchez et al. 1978). LLDA (2005) reported that liquid and solid wastes from point and non-point sources accumulate during the dry season. At the onset of rainy season, these accumulated wastes are flushed into Laguna de Bay. The total coliform count from 1995 to 2004 in the lake was within tolerable limits for Class C waters. The low bacterial population in 1998, 1999, and 2003 could be explained by the cleansing effect brought about by high chloride concentration during summer months. The lake water is still suitable for the growth and propagation of fish as Class C waters.


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Table 10. Length and weight data of janitor fish for two seasons per sampling station. Dry season Station/Site

Wet season

Binangonan

L (cm) 42.0 – 50.5

Wt. (g) 540 – 1,550

L (cm) 30.9 – 35.8

Wt. (g) 250 – 550

Jala-Jala Siniloan

20.6 – 44.5 37.7 – 44.5

50 – 400 –

620 600

20.1 – 37.0 29.7 – 42.7

100 – 300 200 – 550

Taguig

37.0 – 46.7

350 – 1,200

27.0 – 43.0

150 – 550

Table 11. Correlation coefficients for levels of heavy metals in water with different water quality parameters during the dry season in the four sampling stations. Parameters

Cu

Pb

Zn

Temperature (˚C)

-0.84**

0.33

0.40

pH

-0.17

-0.37

-0.12

DO (mg/L)

0.35

-0.66*

0.52

NO2

0.38

0.06

0.14

Transparency (cm)

0.58*

-0.99**

0.15

Salinity

-0.17

-037

0.12

* - significant

** - highly significant

df =10 (n-2)

Table 12. Correlation coefficients for levels of heavy metals in water with different water quality parameters during the wet season in the four sampling stations. Parameters

As

Cr

Cu

Pb

Hg

Zn

Temperature (˚C)

0.29

0.95**

-0.94**

0.30

0.76*

-0.33

pH

0.31

0.97**

-0.97**

0.34

0.81**

-0.37

0.20

-0.48

0.62*

-0.18

0.69*

0.34

-0.03

-0.81**

0.41

-0.63*

DO (mg/L) Transparency (cm) * - significant

-0.69* 0.84**

** - highly significant df = 10 (n-2)

The results of microbiological analyses of fish flesh samples collected during the wet season revealed that most of the parameters analyzed were above the standard limit set by the International Commission on Microbial Specifications for Foods (1986). Thus, seasonal variation greatly influenced the microbial load of fish flesh. CONCLUSION AND RECOMMENDATIONS

The concentrations of heavy metals and microbial load in the janitor fish flesh in the four sampling sites revealed that metal uptake and microbial load in the janitor fish flesh were greatly influenced by the environment and seasonal variation during the dry and wet season. The influx of organic wastes and the massive amounts of pollutants coming from different sources pose a great threat to the lake that favored the proliferation of this species. Most toxic heavy metals are absorbed or tied up in the sediments as precipitated hydroxides. Once converted by bacterial

action into organic form, it can easily enter into the food chain. In this study, the levels of heavy metals in janitor fish flesh were within the standard limits but these should not be ignored. Heavy metals are acutely toxic in excessive amounts and tend to bioaccumulate at low concentration. The microbiological analyses of janitor fish flesh samples collected during the wet season revealed that most of the parameters analyzed were within the standard limits except for copper. Based from the results of the study, janitor fish flesh cannot be processed into fishery products nor fish ingredients for hogs and livestock since these are not suited for human consumption. Although, it can be processed as fertilizer for ornamental plants, forest trees and feeds for ornamental fishes. The skin can also be used as leather material for accent due to its exotic appearance.


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ACKNOWLEDGMENT

The authors would like to thank the Bureau of Fisheries and Aquatic Resources-Region IVA, for funding this study.

ABOUT THE AUTHORS

Hannibal M. Chavez, Manager* Elvira A. Casao, Aquaculturist II/Chemist * Eunice P. Villanueva, Senior Aquaculturist* Madeleine P. Paras, Laboratory Analyst* Marites C. Guinto, Chemist* Marilou B. Mosqueda, Aquaculturist I*

* Regional Fisheries Research and Development Center, Bureau of Fisheries and Aquatic Resources (BFAR)-Region IVA, Bambang, Los Baños, Laguna

Heavy Metal and Microbial Analyses of Janitor Fish (Pterygoplichthys spp.) in Laguna de Bay, Philippines

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