The studying status and use of benthic macro invertebrates for assessment and biomonitoring of water quality in Vietnam

Transcription

1 The studying status and use of benthic macro invertebrates for assessment and biomonitoring of water quality in Vietnam Ho Thanh Hai Institute of Ecology and Bioresources

2 1. Semi-quantitative biotic indices 2. Diversity indices 3. Advantages of using benthic macro invertebrates 4. Difficulties of using benthic macro invertebrates 5. Application of using benthic macro invertebrates for biomonitoring of water quality in Vietnam

3 Biomonitoring Biomonitoring can be defined as the systematic use of biological responses to evaluate changes in the environment with the intent to use this information in a quality control program. In recent years, biomonitoring has been marked by considerable progress such as the evolution of rapid assessment techniques.

4 Biotic indices Among bio-indices, benthic macro invertebrates are often used as an index for rapid assessment of water quality. Developed countries of Europe, North America, particularly some countries in Asia such as China, India and Thailand have studied the use of aquatic organisms for assessment and monitoring of environment. All over the world, studies on use of biotic index for assessment, monitoring of environmental quality have reached to certain achievements in science and real significance as well.

5 1. Semi-quantitative biotic indices Based on using of benthic invertebrates, many countries have established biotic indices of their own for assessment of water quality (Belgic Biological index-bbi; French index-fi; England index-trend Index). Lotic ecologists in the United Kingdom have used the Biological Monitoring Working Party (BMWP) score (ISO, 1979; Amitage et al., 1983) to standardize the assessment of water quality. The BMWP score was designed by using macro benthos for assessment of biological condition of rivers and streams. The BMWP is the sum of the score of each family present in a sample. This total score can then divided by the number of scoring taxa in the sample to produce the Average Score Per Taxon (ASPT). The BMWP score was widely used in several countries such as India, Australia, Thailand and Vietnam. Up to now, there are about 50 different biological indices in use for assessment of water quality.

6 2. Diversity indices Diversity indices are used to measure stress in the environment. It is considered that unpolluted environment are characterized by a large number of species, with no single species making up the majority of the community. The most widely used indices of diversity are the Shannon index (Shannon and Weave, 1949), which assumes that individuals are randomly sampled from an indefinitely large population: H = Ni/N log2 Ni/N Ni = Number of individuals of the ith species. N = Total number of animals in sample Wilhm and Dorris (1968), after examining diversity in a range of polluted and unpolluted streams, concluded that a value of H greater than 3 indicated clear water, values in the range 1-3 were characteristic of moderately polluted conditions and values of less than 1 indicated heavily polluted conditions. However, beside of Shannon index, several other diversity indices are also used for assessment and biomonitoring of environment such as Simpson index, Margaleft index.

7 3. Advantages of using benthic macro invertebrates They are ubiquitous, therefore, they can be affected by environmental disturbances in many different types of aquatic ecosystems and in habitats within those waters. The large number of species involved offered a spectrum of responses to environmental stresses. Their basically sedentary nature allows effective spatial analyses of pollutant or disturbance effects. They have a long life cycles compared to other groups, which allows elucidation of temporal changes caused by perturbations. As a result, benthic macro invertebrates act as continuous monitors of the water they inhabit, enabling long-term analysis of both regular and intermittent discharges, variable concentration of pollutants, single of multiple pollutants, and even synergistic or antagonistic effects.

8 4. Difficulties of using benthic macro invertebrates 4.1. In term of study design: Quantitative sampling is difficult because the contagious distribution of benthic macro invertebrates required high numbers of samples to achieves desirable precision in estimating population abundance. The distribution and abundance of benthic macro invertebrates can be affected by factors such as current velocity or nature of substrate other than water quality. Well-defined seasonal variations in abundance and distribution, especially of insects. Drift behavior in lotic waters can carry macro invertebrates into areas in which they do not normally occur In term of analysis: Certain groups are taxonomically difficult such as larvae of Chironomidae, some Tricoptera, Oligochaeta. The multiplicity of biotic and diversity indices available for working with benthic macro invertebrates may indicate that workers are not satisfied with the results that they provide.

9 Method of biomonitoring using benthic macro invertebrates (BMWP) for rapid assessment of fresh waters quality was presented in detail by Nguyen Xuan Quynh et al, (2000). The steps conducted in the BMWP score: - Choice of sampling sites, - Description of sampling sites, - Invertebrate sampling and - Data processing.

10 5. Application of using benthic macro invertebrates for biomonitoring of water quality in Vietnam 5.1. In Vietnam, the study on use of bioindices to assess environmental quality has just been carried out a few years ago but only in terms of qualitative levels of assessment. There are two considerable projects on study of using biological indices for assessment of freshwater quality: The project on Biological surveillance of fresh waters, using macro invertebrate was conducted in three years ( ) by Hanoi National University, Field study council and Institute of Fresh water Ecology. One of actions of this project is conduction of case studies in Vietnam: one in Tao Dao (in the north) and one in Da Lat (in the south of Vietnam). In , The project on Study and application of some biological factors for assessment of environmental quality in Vietnam was conducted by Institute of Ecology and Bioresources. One of contends of this project was study of using biotic indices for assessment of water quality.

11 In reference to the BMWP used in the UK and the BMWP Thai, a system of new BMWP score that is suitable for macrobenthos fauna and natural conditions of Vietnam was established and therefore called the BMWP Vietnam score. This BMWP Vietnam and the ASPT were performed to assess the quality of some lotic water bodies in northern Vietnam as Tam Dao, Da Lat (HNU), Sa Pa, Tam Dao, Ha Hang, Me Linh and To Lich-Nhue etc (IEBR). We have some remarks as follows: The results show that the BMWPvietnam score can be used for rapid evaluation of water quality in lotic waterbodies in Vietnam. Protocols for lakes, ponds, and sampling devices for certain types of habitats in these systems need to be developed. These results indicate that the BMWP score can be changed by suitable taxa that are present in the macrobenthos fauna of each country or geographical region. In some countries such as Belgium, the score value of BBI of 6 which is considered a permissible standard of surface water quality. The value of ASPT score of 5 will be proposed as a permissible standard of surface water quality in Vietnam (equal to ß Mesotrobic). Eventually, the BMWP score can be widely used in Vietnam, because of the identification of macrobenthos will require only to family level, that can be easily conducted by technicians (non taxonomist).

12 These projects had proposed a program of biomonitoring to assess surface water quality in Vietnam. Scientific fundamentals of this proposal are based upon the following premises: i/ There are already experiences in survey and studied results on aquatic fauna of Vietnam. ii/there is a network of 48 stations for monitoring water quality which was established in whole country since iii/ There are initial results of biomonitoring with collection of samples and analysis of biotic indices.

13 5.2. Recent time, there are also some projects on study of benthic communities, for assessment of coastal waters, which had conducted in Ha Long bay, in several estuarine waters, and aquaculture ponds of the nothern part. In these projects, the Shannon diversity index is only used for evaluation of water quality. Among them, the Shannon diversity index of Nematoda communities was calculated and used to evaluation of water quality in coastal areas. Other biotic indices, especially semi-quantitative biotic indices need to be studied in order to establishment of tolerance scores that have been based on organic pollution and other types of pollution of coastal waters.

14

15

16

17

18

19

20

21

22