BIOACCUMULATION AND CHROMIUM UPTAKE IN MANGROVE ECOSYSTEM OF SUNGAI SEPANG KECIL, SELANGOR, MALAYSIA

I Mushrifah * , S Baktini *, P Mangabeira **, P Galle ***, F. Escaig ***

* School of Environmental Science and Natural Resources, Faculty of Science and Technology, Universiti Kebangsaan Malaysia. 43600 Bangi, Selangor, Malaysia. < mushrifah@yahoo.com>

** Universidade estadual de Santa Cruz, Departamento de Cijncias Biolsgicas, km16 rod. Ilhius Itabuna, Bahia Brazil CEP 45650000. paom@jacaranda.uescba.com.br

***Laboratoire de Biophysics, Faculte de Medicine, Universite Val de Marne, Creteil, France. francoise.escaig@wanadoo.fr

ABSTRACT

Chromium accumulation was studied in sediments and two mangrove species Avicenia officinalis and Rhizophora mucrotata of mangal ecosytem. The percentage of sediment with particle size < 63um increased from the river mouth upstream from 20 to 90 % respectively. The concentration of chromium increases as the percentage of particle size <63um increased. A. officinalis is a better chromium accumulant showing high concentration in roots, branches and leaves. As compared to R mucronata, low accumulation was shown in branches, leaves and roots. Initial studies using secondary ion mass spectrophotometry (SIMS) seems to show that chromium is deposited within the spongy mesophylls of the leaves. In the stem chromium was deposited within the vascular cells.

INTRODUCTION

Mangrove forest or mangal forms about 3.1% of the forest in Malaysia ( Leong,1992). Mangal is rich in biodiversity providing niche for both the flora and fauna. With growing agricultural and industrial activities, production of waste such as heavy metals has a significant effect on the environment. Effluent from treated sewerage, which is rich in chromium, can end its journey in rivers. Its existance by absorption, complexation and formation to organic and non-organic, can disturb the stability of mangal ecosystem.

This study intends to quantify the fate of chromium in the mangal ecosystem. Preliminary studies using two mangrove species were used to identify the site of chromium accummulation. It was carried out using a secondary ion mass spectrometry (SIMS). Other researches have used SIMS to study the biological systems under physiological and pathological conditions. Current data on the river ecosystem is insufficient to provide further information on biodiversity management plans for the river. Therefore, a study on heavy metals contamination in the river ecosystem is vital.

Study area

Sungai Sepang Kecil is a river situated in the state of Selangor, on the western coast of Malaysia. Only the first half of the 10km long river, from the estuary is still mangal. The rest has succumbed to agriculture, agrobase industries, human settlement and plantation. The mangal provides the river with high nutrient, which was once a nursery for oyster and mussel aquaculture cottage industry by the locals to supply their local seafood restuarant in the area. Reports from the Division of Environment, Malaysia ( Jabatan Alam Sekitar, 1995) showed that degradation in the water quality is mainly due to waste from the domestic sewage, development such as the conversion of land to make way for new airports and industries. Such activity too is putting a strain to the river and the mangal ecosystem.

METHODS

About 10 sampling sites were chosen beginning from the river mouth upstream up to where the mangal ends. Both sediment and mangrove were collected and later analysed in the laboratory.

Sediments were analysed by sequential extraction as in Badri and Aston (1983). It has been shown that most of the heavy metals were found in sediment with particle size <63um. Two prominant mangrove species Rhizophora mucronata and Avicenia officinalis were identified at the10 sampling sites along the river. No mangal was observed after the 10^th sampling site. Sampling of the breathing roots, branches and mature leaves were carried out within a period of one year. These samples were used for chromium analysis and the detection of intracellular chromium. Chromium analysis was carried out using atomic absorption and wet digestion analysis.

Similar samples that were used for chromium analysis were fixed and dehydrated. Thin sections of 2um thick were cut and a first generation ion microprobe, SMI 300 Cameca with direct image was used in determination of chromium localisation as carried out by Casting and Slodzian (1962), Galle and Berry (1986).

RESULTS AND DISCUSSION

The percentage of sediment with particle size measuring <63um increased from 19.6 percent, at the river mouth, to 91.9% upstream ( Table 1). This indicated that sediment within the

Table 1: Particle size of sediment <63um at the 10 sampling sites of the mangal

and its corresponding Cr concentrations

Sampling site	Particle size <63um	Concentration of Cr, ug/g dry wt.
1	19.6± 1.6	8.01± 3.0
2	57.6 ±2.3	8.3 ±2.9
3	86.5 ±1.2	10.1± 3.7
4	70.6 ±2.4	11.7± 4.2
5	84.2 ±0.8	10.4±3.7
6	88.6 ±0.4	9.9 ±3.6
7	89.4 ±0.7	14.1± 5.2
8	82.7 ±1.4	11.6± 3.9
9	74.9 ±2.2	12.6± 4.3
10	91.9± 0.3	13.0± 5.1

mangal are mainly silt/clay and loam ( particle size 3um). Harbison (1986) has reported similar work. There is a positive linear relationship (r=0.705), indicating that with increase in % of particle size <63um, the concentration of chromium increased. Such particles provide the bioavailability to sediment-bound metals.

Figs 1 and 2 showed the accumulation of chromium by both the mangrove species. A. officinalis seems to accumulate chromium highest in roots ( range 5.3± 0.2 - 8.4± 0.7 ug/g dry wt), followed by branches ( range 0.8± 0.4 - 2.6± 0.1 ug/g dry wt) and leaves (range 0.5 0.1 -2.6± 0.3 ug/g dry wt ). The accumulation of chromium in R. mucronata is highest in branches (range 0.03± 0.04 - 0.7 ±0.3 ug/g dry wt ) while in leaves ( 0.3± 0 - 0.4± 0.1 ug/g dry wt ) and in roots (ranged from undetectable levels - 0.1± 0.01 ug/g dry wt). Boring et al (1981), has reported that metal accumulation also occurred in perennial tissues. The low chromium uptake in plant showed that there was a low availability of chromium from sediments.

The SIMS images provide a map of the distribution of Ca, Na which are the essential nutrients

for plants. Chromium signals were made in comparison to both the Ca and Na images as a bright signal. Chromium was detected within the phloem cells of the branch of A officinalis ( Fig. 3). In the leaves of the same species, only a small amount of Cr was was detected within the spongy mesophyll cells ( Fig. 4). Generally translocation of Cr from the roots to the leaves are slow. Roots act as the intermediate before Cr was transported to the xylem and the phloem to the leaves.

Organic matter, iron minerals and other reducing agents in sediment are know to reduce chromium VI to chromium III under acidic conditions. This condition persists in mangal ecosystem. Chromium accumulation in Rhizophora and Avicenia could suggest that mangal could be the reservoir for metal in the long term.

Chromium deposition in R. mucronata has been described elswhere ( Proc. in Symposium Biology in the Next Millenium. Kuala Lumpur, 1-3 December 1999- in press).

Fig. 3 Ion microscope images of A. officinalis showing the vascular cells in stem. A. ²³Na image B. ⁴⁰ Ca image

C. ⁵²Cr image. Xylem (X), Phloem (Ph), Chromium (Cr). Magnification x700

A B C

Fig. 4 Ion microscope images of A. officinalis showing the cells in leaves. A. ²³Na image B. ⁴⁰Ca image

C. ⁵²Cr image.

Spongy mesophyll cells (SM), Interstitial spaces (IS), Chromium (Cr). Magnification x700

A B C

REFERENCES

Badri MA and Aston SR (1983), Environ. Pollut. (Series B) 6:181-193

Boring LR, Monk CD, and Swank WT (1981), Ecology, 62:1244-1253.

Casting R and Slodzian G (1962),. J. Microsc. !:395-410

Chih-Yu and Chou C-H (1991)Soil Sci. Plant Nutr. 37(4):659-669

Feder, R., McGowan, JW and Shinozaki, DM (eds), Plenum Press, New York, 1986, pp 35-50

Galle P and Berry JP. Analytical ion microscopy of cells and tissue. In: Examining the Submicron World,

Glauert, AM. Fixation hydration and embedding of iological specimen. In: Practical Methods in Electron Microscope, Glauert AM (ed), North Holland Publ., Amsterdam, 1098, pp 73-123

Harbison P (1981), Search 12(8): 273-276

Jabatan Alam Sekitar (1995), Pengawasan Alam Sekitar. In: Laporan Tahunan Jabatan Alam Sekitar Negeri Selangor. Selagor Jabatan Alam Sekitar, pp 39.

Leong HN (1992),. In:2^nd Intl. Conf. On Trop. and Hardwood Tim. Struc. Kualal Lumpur , pp 44-48.

ACKNOWLEDGEMENT

This project is made possible from the following funds. UNESCO Biotechnology fellowship, IRPA 08-02-02-0006 and Laboratoire de Biophysics, Faculte de Medicine, Univ. Paris Val de Marne, Creteil, France.