DANIDA Danish International Development Assistance. NREB Natural Resources and Environment Board Sarawak

Transcription

1 NREB Natural Resources and Environment Board Sarawak MONITORING OF RIVERBED INVERTEBRATES IN RIVERS AND TRIBUTARIES IN THE KUCHING AREA November 2003 September 2004 DANIDA Danish International Development Assistance

2 DANIDA-SARAWAK GOVERNMENT Urban Environmental Management System Project MONITORING OF RIVERBED INVERTEBRATES IN RIVERS AND TRIBUTARIES IN THE KUCHING AREA November 2003 September 2004 Report No. UEMS_TEC_02_34 Issue No. 1 Date of Issue September 2004 Prepared Chemsain (Katherine Atack) Checked ILA Approved

3 i Table of Contents 1. Introduction Materials and Methods Sampling Locations Sampling Methods Riverbed Invertebrates Identification Results and Discussion Abundance, number of species Species Diversity Burrowing Macrobenthos Environmental factors affecting the fauna Loss of Ignition Ammonium (NH 4 -N) and Oxygen (O 2 ) Conclusion... 14

4 1 1. Introduction The Urban Environmental Management System (UEMS) project aims to implement an Environmental Management System for the City of Kuching. The project is a follow-up project to the SUD-project, which ended in May During the SUDproject, the basic framework for the urban environmental management system (UEMS) was developed and implementation was initiated. The UEMS project commissioned Chemsain to undertake the study in accordance with the TOR document. UEMS_TEC_TOR for monitoring benthos and sediment. The UEMS include monitoring of selected indicator parameters of river quality as an essential element. Benthic invertebrate population dynamics in sediments have been selected as state indicators on river quality. A baseline study on benthic invertebrate populations in sediments was carried out in November 2000 as part of the elaboration of the river quality baseline study in the SUD-project (Reported in the SUD report: "Field Studies of Sediment Contamination and Benthic Invertebrate Fauna in Sg Sarawak (SUD-02-27). This present study is to monitor the progress in river quality since the baseline study was carried out. 2. Materials and Methods Sampling was carried out in Sg. Sarawak, Sg. Kuap, Sg. Maong and Sg. Bintangor during the period 27 th October 13 th November The sampling was carried out from an open 8-person boat. Katherine Atack (Marine Biologist, Chemsain consultant) headed the sampling team comprising Danish MSc student, Tina Marienhof and Chemsain technicians. Sampling Locations Benthos and sediment sampling were carried out at ten sites in Sg. Sarawak, three sites in Sg. Kuap, two sites in Sg. Maong and one site in Sg. Bintangor, between 27 th October and 13 th of November Table 1 gives a short description and position of each sampling location, with a map of the locations depicted in Figure 1. Sg. Sarawak S1 Upstream of the confluence of Sg. Sarawak and Sg. Maong S2 Downstream of the confluence of Sg. Sarawak and Sg. Maong Table 1: Sampling sites River St No Site Description Past GPS coordinates N 01 o E 110 o N 01 o E 110 o S3 At Satok Bridge N 01 o E 110 o S4 Off Sg. Bintangor N 01 o E 110 o S5 Off Holiday Inn N 01 o E 110 o S6 Off Kuching Port Authority/ N 01 o downstream of Petanak E 110 o Market Present GPS coordinates N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o

5 2 S7 Off tributary west of Kg. Bintawa N 01 o E 110 o S8 Off Pending N 01 o E 110 o SD1 East of Pending N 01 o E 110 o S9 Downstream of Barrage N 01 o E 110 o Sg. Kuap SD2 Downstream of Sama Jaya N 01 o Free industrial zone E 110 o SD3 At Sama Jaya Free Industrial N 01 o Zone E 110 o SD4 Upstream of Sama Jaya Free N 01 o Industrial Zone E 110 o Sg. Maong Kiri SM1 About 200m above the Not sampled confluence previously Sg. Maong SM2 About 100m above the Not sampled Kanan confluence previously Sg. Bintangor SB1 Upstream past small bridge. Not sampled previously N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o N 01 o E 110 o Figure 1: Location of sampling sites for sediment and benthic macro-invertebrates in November Extra sampling locations in Sg. Kuap, Sg. Maong and Sg. Bintangor

6 3 2.2 Sampling Methods Sediment and Riverbed invertebrate monitoring was carried out at the same time with the sediment results reported in a separate document. Sites were chosen from somewhere between the middle of the river and the banks. The closer to the banks, generally, the easier it was to grab. A manual operated Van Veen (21 x 21 cm) Grab was used at all stations (Plate 1). The surface area of the grab was 576 cm 2. Four grabs samples were collected from each site. Three grabs were taken for Riverbed invertebrate analysis. This covered a total area of 0.17m 2. One grab (estimating 2 kg of sediment) was taken for sediment collection; this was used for pollutant and grain size analysis. Plate 1: Grab sampling with the Van Veen Grab The grab samples used for benthic invertebrates were first mixed into suspension with water before being poured through 2.8 mm, 1.4 mm and 1 mm sieves. All debris collected in the sieves was collected and placed in 70 % ethanol for later sorting under a microscope. All sieving was done using a large basin of water, if any un-sieved solution was spilled then the water was sieved again. At sites where there were small oligochaetes found, the water was also sieved again to confirm no oligochaetes had escaped through the 1 mm sieve. Snails were placed in the jars along with the debris. Oligochaetes and crustaceans were placed in a separate container of 70 % ethanol. Small spoons and tweezers were used to collect the debris from the sieves. Fine pointed tweezers were best for collecting small oligochaetes and crustaceans. 2.3 Riverbed Invertebrates Identification Prof. Dr. Ann Anton from the University of Malaysia Sabah (UMS) carried out the identification of the riverbed invertebrates collected.

7 4 3 Results and Discussion 3.1 Abundance, number of species In this study the abundance of benthic invertebrates range from 0 to 1189 individuals / m 2 and the number of species per station range from 0 to 9 (Table 2). From Table 2 it is clear that the Molluscan Mesogastropods dominate the fauna of Sg. Sarawak upstream of the Barrage. The most common being Terebia sp. and Gillia sp.. Sg. Kuap has the most diversity of species but over all the Oligochaetes and Gastropods are the most common. The most common benthic invertebrates in Sg. Maong are Terebia sp. and Gastropods, as in Sg. Bintangor. Table 2: Numbers of individuals of each species (abundance) at each station (number of individuals /m 2 ) Numbers of individuals of each species (abundance) at each station (number of individuals /m 2 ) Ta xa S1 S2 S3 S4 S5 S6 S7 S8 S9 SD1 SD2 SD3 SD4 SM1 SM2 SB1 Oligochaetes Tubifex tubifex Limnodrillus sp.1 12 Limnodrillus sp.2 12 Limnodrillus spp 47 Limnodrillus sp Limnodrillus sp.4 Limnodrillus sp.5 Limnodrillus sp.6 Limnodrillus sp.7 Limnodrillus sp.8 Stylaria sp. Turbellaria sp. 18 Turbellaria sp. Amphipoda Gammarus sp Mollusca Mesogastropoda Fam. Thiaridae Terebia sp Gillia sp Pygulopsis sp. Basimatopora Anchyidae sp.1 Caenogastropoda Fam Littorinidae Littorina sp Polinices sp. Turritella sp. Hastula sp. Clypeomorus sp. Tritonoturris sp. Archaeogastropoda Fam.Trochidae 12 Umbonium sp. 6 Bivalvia Fam Semelidae 6 Semela sp. Periglypta Oyster Class Hirudinea 12

8 5 (leech) Class Asteroidea 24 Crustacea Fam. Palaeomonidae (freshwater shrimp) Order Stomatopoda (mantis shrimp) 6 Pisces 29 Gastropoda Sp1 6 Sp2 6 1 Sp Sp Sp Sp Total abundance Total no species Shannon Wiener Margaleff Abundance data from the previous study in November 2000 cannot be directly compared to the current data as abundance was previously measured in volume (individuals /m 3 ) compared to abundance measured in surface area (individuals /m 2 ). It is however, possible to compare diversity indices. 3.2 Species Diversity The species richness (R) is low ranging from 0 to 1.67 (Table 2, Figure 2). The diversity and species richness of macrobenthos generally shows an increase downstream from S3 to S9. Sg. Kuap shows and overall greater species diversity and richness than the other three rivers studied. Though Sg. Maong and Sg. Bintangor show relative higher diversity and richness to that found in Sg. Sarawak. Figure 2: Diversity Index (H = Shannon Wiener index) and species richness (R1 = Margaleffs index) at each sampling site.

9 6 It is very clear from Figure 3 that there has been a decrease in species diversity since the sampling taken in November 2000 throughout almost all sites in Sg. Sarawak. The Margalef richness index is not so clear, though due to the simplicity of the statistical equation, this may not be such a true indication as the Shannon Wiener species index (Figure 4). Figure 3: A comparison of the Shannon Wiener Diversity Index for each sampling station between November 2003 and 2000 (SD1 to SD4, SM1, SM2 and SB1 where not sampled in 2000)

10 7 Figure 4: A comparison of the Margalefs species richness index for each sampling station between November 2003 and 2000 (SD1 to SD4, SM1, SM2 and SB1 where not sampled in 2000) 3.3 Burrowing Macrobenthos Comparing the composition of burrowing and surface dwelling benthic invertebrates in the sediment will give additional information on the environmental conditions. Large numbers of burrowing organisms will only be found in well-oxygenated sediments, whereas sediments with no burrowing organisms may indicate that the sediments are anaerobic and not habitable. Burrowing macrobenthos are found throughout the sampling stations of Sg. Kuap. S9 has the highest number of burrowing organisms. No burrowing organisms are found in up-river stations of Sg. Sarawak; only stations S7 and S8 closest to the barrage contained a very small number (less than 5 %). Burrowing macrobenthic species were found in the sediments of Sg. Maong Kiri (Figure 5)

11 8 Figure 5: Percentage of burrowing organisms found in the sediments taken from all sampling stations Comparison of the percentage of burrowing macrobenthos from the sediment samples taken in November 2000 and November 2003 show total macrobenthic burrowing organisms have become completely extinct from the upriver locations of Sg. Sarawak (Figure 6). The sediment samples from the 2000 study contained 100 % burrowing species from stations S1, S3 and S6-S8. The only increase in benthic organisms is found from samples from S9, outside the Barrage. Figure 6: A comparison of the percentage of burrowing organisms found in the sediments at each sampling site between November 2003 and 2000 (SD1 to SD4, SM1, SM2 and SB1 where not sampled in 2000)

12 9 From figures 7 & 8 it can be seen that the sediments from the upriver stations of Sg. Sarawak have increased in Loss on Ignition and also many of the sites have an increase in ammonia levels between November 2000 and This strengthens the idea that oxygen levels in the sediment have decreased and that the sediment is no longer conducive to the inhabitation of burrowing organisms. Loss on Ignition % S1 S2 S3 S4 S5 S6 S7 S8 S9 Station Figure 7: Comparison of the content of organic matter in the sediment (measured as loss on ignition) in Sg. Sarawak between 2000 and 2003 Ammonium (NH4-N) in Sediment mg/kg S1 S2 S3 S4 S5 S6 S7 S8 S Station Figure 8: Comparison of the content of ammonium (NH 4 -N) in the sediment in Sg. Sarawak between 2000 and Environmental factors affecting the fauna It is clear that the macrobenthic fauna population has both decreased in number and species composition since the study carried out in November This is clearly due to degradation in the quality of the sediment. Based on a substantial amount of data, Pearson and Rosenberg (1978) found a general succession pattern on benthic infauna in response to increased input of organic material to the sediment:

13 10 Increasing the input of organic matter will initially result in an increase in the number of species, the biomass and the density (abundance) of organisms because it increases the amount of food available (many benthic species feed on organic matter on the seabed). When the input of organic material reaches a certain level, the number of species, the biomass and the density start to decline. This is due to a reduction of the oxidised layer of the sediment as the decomposing process of the organic matter uses available oxygen. At very high loads, oxygen depletion in the sediment may periodically take place. Only very few species can tolerate such conditions so the number of species decrease further as a result. Longer periods of oxygen depletion lead to the extinction of the fauna. In case oxygen conditions improve the area will rapidly be re-colonised by a very few so-called opportunistic species, which may be found in high densities Loss of Ignition Figures 9 and 10 show the percentage loss of ignition (the organic load), the abundance (number of individuals) and diversity (number of species) of macrobenthos living in the sediment. For Sg. Sarawak and Sg. Kuap LOI generally ranges between 20 and 40 % but the abundance varies from 400 to 1000 indiv/m 2. But it is clear that the Sg. Maong stations have some of the highest LOI and correspondingly lowest abundance. Figure 9: Abundance (number of individuals) compared to the content of organic matter in the sediment (measured as loss on ignition) (recorded from sediment collected at the same time as the macrobenthos)

14 11 Figure 10: Number of species of benthos compared to the content of organic matter in the sediment (measured as loss on ignition) (recorded from sediment collected at the same time as the macrobenthos) Ammonium (NH 4 -N) and Oxygen (O 2 ) The situation becomes clearer when looking at the ammonium content in the sediment. Nitrites in the organic material require oxygen to become nitrates, otherwise forming ammonium. High ammonium levels indicate low oxygen levels in the sediments. Figures 11 and 12 illustrate a correlation between ammonium (NH 4 -N) and abundance and diversity of macrobenthos living in the sediment. It is clear that the higher abundance found in the downstream stations of Sg. Sarawak and Sg. Kuap generally corresponds to lower levels of ammonium. While the lower levels of ammonium in Sg. Kuap give a much greater species diversity. Conversely Sg. Maong and Sg. Bintangor have some of the highest ammonium levels and correspondingly lowest abundance. Figures 11a and 12a have been added to illustrate that the average annual ammonium level calculated from water samples are very similar to those found in the sediment with the same results. This is illustrated to give confidence in the comparison between oxygen levels and abundance and diversity illustrated in Figure 13. Figure 13 strengthens the overall findings from both LOI and ammonium levels. Showing that oxygen depletion has occurred throughout the sediments of Sg. Sarawak and that this results in lower numbers of macrobenthic invertebrates. This is clearest in the Sg. Maong Kiri and Kanan and Sg. Bintangor stations (SM1, SM2 and SM3 respectively).

15 Abundance (indiv/m2) NH4 (mg/kg) 12 Figure 11: Abundance (number of individuals of benthos compared to the content of ammonium (NH 4 -N) in the sediment (recorded from sediment collected at the same time as the macrobenthos) S1 S2 S3 S4 S5 S6 S7 S8 SD1 SM1SM2 SB1 S Abundance NH4 sed Figure 11a: Abundance (number of individuals) compared to the content of ammonium (NH 4 -N) in the sediment (taken from an average from water samples collected throughout the year)

16 Number of species NH4 (mg/kg) 13 Figure 12: Number of species of benthos compared to the content of ammonium (NH 4 -N) in the sediment (recorded from sediment collected at the same time as the macrobenthos) S1 S2 S3 S4 S5 S6 S7 S8 SD1 SM1 SM2 SB1 S No species NH4 sed Figure 12a: Number of species of benthos compared to the content of ammonium (NH 4 -N) in the sediment (taken from an average from water samples collected throughout the year)

17 14 Figure 13: Abundance (number of individuals) compared to the content of oxygen in the sediment (taken from an average from water samples collected throughout the year). 4 Conclusion The benthic fauna and environmental data was also analysed by multivariate statistics in order to assess if, and to what extent, the fauna was affected by discharge of pollutants from Kuching. The results of this analysis are reported in a separate note: UEMS_TEC_03_49.Statistical analysis of 2003 Benthic fauna data. From this benthic fauna study it can be concluded that: The high load of organic matter from Kuching clearly affects the benthic fauna. The Statistical Analysis of the 2003 benthos data from Sg. Sarawak, Sg. Maong, Sg. Bintangor and Sg. Kuap report confirms the finding here that the fauna in Sg Maong/Sg Bintangor is the most affected by pollution, followed by the fauna in Sg Sarawak. The fauna in Sg Kuap is the least affected. The Statistical Analysis of the 2003 benthos data from Sg. Sarawak, Sg. Maong, Sg. Bintangor and Sg. Kuap report confirms that it is the pollution load from Kuching city (measured as concentrations of BOD, oxygen and NH 4 -N in water and concentrations of Total N and NH 4 -N as well as loss of ignition of sediments on the sampling sites) as well as differences in salinity that causes these differences in fauna composition between the three river systems. The absence of burrowing organisms, increase in LOI and ammonium and the overall reduction in benthic fauna diversity in Sg. Sarawak clearly indicated that the sediment conditions have deteriorated since the November 2000 study.