NAT. NAT. HIST. BULL. SIAM Soc. 47:225-252 ，1999

LOTIC MACROINVERTEBRA TE ASSEMBLAGES IN NORTHERN THAILAND: ALTITUDINAL AND LONGITUD I1河 AL DISTRIBUTION AND THE EFFECTS OF POLLUTION

Stephen Stephen E. Mustow 1

ABSTRACT

distribution 百le distribution and composition of invertebrate faunas was studied in upland ，lowland and and urban sites in the north basin of the River Ping in Th ailand. Th e princip a1 physico ・ chemical chemical features of 23 sites were measu 問 d 佃 d the invertebrates in se ぉ onal net-sweeps ， bottom bottom kick and dredge samples identified to fam i1 y leve l. Canonic a1 correspondence an a1 ysis was was used to assess relationships between environmen ta1 and biological data. Taxon accretion was was studied at two sites in order to determine the sampling effo 民間:quired to ∞u巴ct representa ・ tive tive kick-samples. Accretion rates were within the range recorded in temperate rivers. Di 釘'er- ences ences in the fauna amongst 血e 23 sites were explained by temperaωre ，conductivity ，pH ，and

current current velocity. Reductions in diversity at severely pollu 旬 d sites were sm a1 ler 伽 n in simi ・ larly larly impacted sites in temperate regions.

INTRODUCTION

Th e ecology of aquatic invertebrates in Asia as a whole is poorly understood (RUNDLE ET AL. ， 1993; DUOGEON ，1995) ， not least in Th ailand for which few studies are reported in in the literature. Th e most detailed studies in Th ailand have been of a reservoir in 白e central central region (JUNK ，1975 ， 1977) and of a rice field in the Northeast (HECKMAN ， 1979). Work published on 血 e macroinvertebrate fauna of rivers includes a preliminary survey of the the Chao Phraya and Ri ver Kwai river systems (MIZUNO & Mo 阻， 1970); a study of the trichopteran trichopteran fauna of upland streams through collections of adults (MALICKY & CHANTARAMONGKOL ， 1993); an assessment of river water quality using macroinvertebrate data data gathered by standard colonisation units (THORNE & W 且 LIAMS ， 1997); and an investigation investigation of changes in 出e chironomid fauna in relation to water quality us 泊 g collections of of pupal exuviae (MUSTOW ET A ム， 1997). 官邸paper presents the results of an investigation of the basic 世田知re and composition of of macroinvertebrate assemblages in northern Thailand and relationships to key environmental environmental factors. The biological data set obtained for 血is purpose was produced by analysing analysing samples of macroinvertebrates collected from four main rivers and some smaller 凶butaries ， ranging in altitude from 280 m (all altitudes quoted are above mean sea level) to to 2， 100 m and in width from 3 m to greater than 100 m.

1 9 Kn ighton Road ，Sutton Coldfield ， West Midlands ， B74 4NY ，United Ki ngdom. Received Received 11 J叩 U紅 y 1999; accepted 23 September 1999.

225 226 STEPHEN E. MUSTOW

...... 19' 30'

98' 25' e • sampling site 20km ~ • land above 500 m AMSL .a. • · town (not all are shown)

Figure 1. Map of the study area showing the positions of study sites. insets show the location of the study area and the River Ping within Thailand and detailed locations of the Doi lnthanon Group sites. LOTIC LOTIC MACROINVERTEBRATE ASSEMBLAGES IN NORTHERN THAILAND 227

In In common with the present study ， recent investigations of the macroinvertebrate fauna fauna of Nepalese 柑 'eams (Rtrπ ET AL. ， 1990; RUNDLE ET AL. ， 1993; SUREN ， 1994) relied on family-level identification. The family-level approach has also been used success 白lly in 血e UK (Fu RSE ET AL. ， 1984; ARMITAGE ET AL ， 1987; WRIGHT ET Aム， 1988) ，No 巾 America (Co 郎 UM ，1989) ，temperate and tropical p紅 ts of Australia (WRIG 町 ETAL ，1995; FA 汀'H ET AL ， 1995; CHESSMAN ， 1995) and recently in Tha i1 and ，Ghana and Braz i1 (THORNE & WILLIAMS ， 1997). However ，some authors have questioned whether the environmental environmental requirements of particular groups of freshwater invertebrates can be generalized generalized at taxonomic levels above species (RESH & McELRAVY ， 1993). The results obtained obtained in 血 is investigation provide further evidence of the eぽectiveness of family-level identification identification when employing macroinvertebrates as indicators of the environmental quality of of rivers.

STUDY AREA

The study was carried out in northem 百lailand (Fig. 1) in the Northwest Highlands ， which which include several peaks above 2，000 m. Doi Inthanon (2 ，565 m) is the highest of these and the highest peak in 出e coun 住y， and lies to the west of the River Ping ， southwest of of Chiang Mai city. 百le study area was contained within an area bounded by latitude 18 0 15'N and 19 0 30 'N and longitude 98 0 25'E and 99 0 15'E (Fig. 1). Land within this 紅白 falls falls almost entirely within the Ri ver Ping catchment ， which inωm is p訂 t of the Chao Phraya Phraya catchmen t. Most land up to about 400 m altitude is within the Chiang Mai Basin. Twenty-three Twenty-three sampling sit ，回 were located on the Ri ver Ping and several of its 凶butary systems: systems: the Taeng ，Kh a，K1 ang and Chaem. The sites were divided into two groups: i) i) Th e “Pi ng Group" included sites on the Ping and two of its tributaries ， the Taeng and and the Kh a， between H 佃 g Dong District in the south and Chiang Dao Di s回ct in 白e north ， ranging in altitude from 280 m to 410 m (Fig. 1). ii) ii) The “Doi Inthanon Group" included sites on the River K1 ang and Ri ver Chaem systems systems at 290 -2 ， 100 m (Fig. 1). Table Table 1 gives details of locations ，altitudes ，mean widths and gradients. Land use in the the immediate 釘 'ea of the sampling sites is described in Table 2. The Ping Group of sites were chosen to provide data on am 吋or low-altitude river ， which was reputed to have been degraded as a result of pollution ， river regulation ， deforestation deforestation and intensive fi 紅 ming. Those in the Doi Inthanon Group were selected to provide provide data on high altitude streams. The stations on 血e Pi ng were located so 白紙 the first four were a considerable distance distance upstream of Chiang Mai city ， and could thus be considered to be relatively clean. However ， these sites were not entirely unaffected by human activities ， as much of the land in 血e valley floor had been deforested and intensive agriculture was taking place in the area area of Chiang Dao town. The remaining sites on the Ping were located so as to straddle ChiangM 国 city ， in order to detect any associated deterioration in water quality. A sampling site site was included on 血e Taeng ， as it is a major tributary of the Ping in the study area. Two sites sites were also included on the Kh a Canal ， which is 出e most polluted of the main Ping tributaries. tributaries. The Kh a Canal is an integral part of the wastewater drainage system in 出e Chiang Chiang Mai municipal area. 228 228 STEPHEN E. MUSTOW

Table Table 1. Location ，altitude ，slope and me 組 width of sampling sites.

Site Site Code Ri ver Dis 畑氏(km)1 Al ti 加de (m)2 Mean width (m)3 Slope (%0)4 Ping Ping Group Pl Pl Ping 。 410 22.3 (3.8) 2 P2 P2 Ping 31 360 18.7 (1. 5) 1. 5 P3 P3 Ping 37 340 17.7 (1. 2) 2.5 P4 P4 Ping 43 330 26.0 (11.1) 2.5 PT Taeng 3 330 11. 6 (5 .4) 1. 5 P5 P5 Ping 90 310 34.7 (5.9) 0.5 P6 P6 Ping 105 300 50.7 (7.8) 0.5 p7 Ping 107 300 77.0 (8.5) 0.5 P8 P8 Ping 108 300 110.5 (0.7) 0.5 p9 Ping 112 300 54.0 (4.2) 0.5 PKl Kh a 3 300 20.3 (2.5) 0.5 PK2 Kh a (arm 00 0.1 290 3.3 (2.5) 0.5 PI0 PI0 Ping 133 280 83.0 (6.9) 0.5

Doi Doi Inthanon Group Group KC Tributary of N/A 2100 3.5 (1. 0) 100 Chaem K t1 Tributary of 2 1360 4.3 (3.2) 50 Kl ang Kl Kl組 g 。 1270 7.5 (2.7) 40 K2 Kl ang 5 1010 7.8 (1. 0) 30 K t2 Tributary of 0.5 940 5.8 (1. 9) 60 Kl ang Kt3 Kt3 Tributary of 0.5 590 4.3 (0.5) 40 Kl ang K3 Kl ang 12 560 11. 8 (2.5) 20 K4 Kl ang 21 430 15.0 (2.8) 20 K5 Kl ang 24 310 8.0 (3.6) 20 K6 Kl ang 34 290 15.8 (2.6) 2

Distances I Distances of sites on the main rivers 訂官合om the highest on point 血.e river. Distances of sites on 凶butaries are are from the point of confluence with the main river. 2Alti 旬 de accurate to 土 10 m. 3S tan dard deviation of mean width shown 泊 paren 血eses. 4S1 0pe calcula 旬d 血 rough examination of contour pattems i目白 eimmediate vici 凶ty of sampling stations. LOTIC LOTIC MACRO 別 VERTEBRATE ASSEMBLAGES IN NORTHERN THAILAND 229

Table Table 2. Land use in the immediate 紅 'ea of sampling sites.

Site Site code Land use in the immediate 紅白 of sampling site Ping Ping Group Pl ，P2 cultivation of lowland crops P3 forest (elephant 住aining camp on one side in forest) P4 ，PT ，P5 cultivation of lowland crops P6 ，P7 ，P8 ，P9 urban area within Chiang Mai City PKl mainly unused scrubland on 血e edge of Chiang Mai city PK2 village on one side ， unused scrubland on the other PI0 cultivation of lowland crops

Doi lnthanon Group KC deforested area ，just downstream of primary evergreen hardwood forest forest t1， K t1， Kl cultivation of upland crops ，also some 紅 'eas of conifer pl 佃 tations K2 cultivation of upland crops (mainly rice) Kt2 ，Kt3 ，K3 ，K4 forest K5 cultivation of lowland crops K6 cultivation of lowland crops on one side ， edge of Chom Thong town on the other

Sites Sites on Doi In 白anon were located to cover ar 佃 ge of altitudes ，from the highest point point where a stre 創 n could be easily reached ， to the lowlands ，just before the confluence of of the Kl ang with the Ping. Much of the forest cover remained above 400 m ， although parts had been cleared for timber and farming. Below 400 m deforestation was complete and most of the land was cultivated. Sites on several tributaries of the Kl ang were included for comparison comparison with sites on the main stream. As the Kl ang itself originated below the summit of of Doi In th 佃 on ，a site was also included on a tributary of 血e Chaem Ri ver at 2， 100 m. Mean annual precipitation ranges from approximately 800 mm to slightly more 出m 1，800 mm in the catchment of the Chao Phraya Ri ver (ALFORD ，1992). In northem 百 ailand rainfall rainfall is heavier in the mountains 血an in the valleys (SMπ 町 AND El' A L.， 1978). 百lere are 白ree seasons: the rainy or wet season ， in which about 80% of the annual rainfall occurs ，lasts from June 白rough October; the cold season lasts from November through February; February; and the hot season from March through May.

MAτ 'E RIALS AND METHODS

Physico-chemical Physico-chemical Survey

Physico-chemical Physico-chemical s創 npling took place once in each of the 由ree seasons. Measurements were taken between 6:00 組 d 19:00 ， with sites commonly being visited in sequential order. order. Readings were taken over two years (September 1991 to April 1993) other 出釦 on 230 STEPHEN E. MUSTOW the the Kh a Canal ，where the sampling period covered one year (December 1992 to September 1993). 1993). Measurements of nitrate and phosphate concen 回 tion were taken once ， at a limited number of sites. Widths ， depths and current velocities were measured or estimated. Near- surface surface measurements of temperature were made using a thermometer ，conductivity ， dissolved dissolved oxygen (DO) and pH were measured using multi-probe kits (manufactured by Walden Precision Apparatus and Ciba ・Corning) ， and transparency was measured by Secchi disc. disc. Orthophosphate and nitrate nitrogen were analysed from samples taken in September 1993 ， using a Hach D Rl 2000 spectrophotometer. Data on calcium hardness were provided by Chiang Mai University's chemistry departmen t. Physico-chemical Physico-chemical data were produced from spot measurements and can therefore only provide provide a limited picture of conditions at the sampling sites ， which would have been highly variable. variable. Temperature and DO change over a daily cycle and most other p紅釘neters change with with discharge. However ， the data are considered adequate for the pu 中ose of classifying sites sites and for highlighting locations where the macroinvertebrate fauna may be affected by extreme extreme environmental conditions.

Macroinvertebrate Macroinvertebrate Survey

At Ping Group shallow sites (Pl ・P5 ，PT) samples were collected over two years ， once in in each of the three seasons. Elsewhere the sampling period lasted for one year. Kh a Canal sites sites were sampled only twice ， in the hot and rainy seasons of 1993. Sampling of shallow sites sites on the Ri ver Ping and the River Taeng began in December 1990 and continued ， at approximately approximately four-month intervals ，until August 1992. The same schedule was followed for for Doi Inthanon Group sites but sampling took place for one ye 紅 only ， ending in September 199 1. Sampling of the deep sites (P6-PI0) on the River Ping began in August 1991 and continued ， again at approximately four-month intervals ，until April 1992. Macroinvertebrate Macroinvertebrate assemblages at shallow sites (PI-P5 ，PT ，PK2 ，all Doi Inthanon Group sites) were sampled using a pond-net (400μm mesh ， 32 x 20 x 20 cm triangular frame ，50 cm bag depth) ，fitted to a 1. 4m handle. Th e 3-min kick-sampling technique described described by FuR. SE ET AL. (1981) was employed ， with some minor modifications. Between six six and eight 3-min kick samples were taken on each s創 npling occasion at each site 佃 d these these were combined to give an overall sample. In four cases the full level of sampling effort effort could not be employed ， due to high river flows. Numbers of individuals in each far 凶ly were estimated using counts of individuals in fractions of the overall sample. All abundance abundance data were converted to the format “ numbers per 3・min kick". To assess how many 3・min kick-samples would be required to produce an adequate overall overall sample ， a series of nine 3-min kick samples was taken at K2 on 8/12/90 and at Pl Pl on 9/1 2/90. The samples were analysed separately and taxon accretion cu 何回 were constructed constructed using ten random combinations of sample order (MUSTOW ， 1997). The calculated calculated values were based on the total 27 ・min catch representing 100% ， as a convenient way of comparing the two sites. Th e curves showed that on average six samples were required required to catch at least 90% of 出e taxa in the 27-min catch ， while eight s釘 nples were necess 紅 Y to catch 95% of the taxa ， at both sites. Thus ， as eight samples would give an almost almost comprehensive family list and could be collected in an acceptable amount of time by two operators ，this was subsequently adopted as the standard sampling effort. LOTIC LOTIC MACROINVERTEBRATE ASSEMBLAGES IN NORTHERN THAILAND 231

Macroinv 倒的rate assemblages at deep sites (PιPI0 ，PK l) were sampled using a hand-operated hand-operated dredge (mouth 9 .3 x 31 cm ，leng 血 50 cm ，mesh opening 500μm ， weight 6 kg) attached to a cable of length 10m. The dredge was thrown out from the bank and a combined sample was produced from five throws. Samples were taken from submerged marginal marginal vegetation ，when present ， using a pond-net of 出e type described above. Th is was swept swept through the submerged vegetation for a total of ten minutes. The taxa present in dredge dredge and net-sweep samples were recorded. Macroinvertebrate Macroinvertebrate samples were preserved in formalin and so 凶 ng and identification of of specimens took place in the laboratory. Family-level identification was used as standard because: because: i. i. Due to a lack of keys and the large number of undescribed species present in the study study rivers ，it would have been impossible to identify many specimens to generic or or species level with the resources available. ii. ii. In some cases where keys to Thai existed species ，more recent literature showed that that they required significant revision (WOODR 凹 F ET AL (1993) ， for example ， have have proposed that 20 nominal Corbicula (Corbiculidae ，Bivalvia) species from Th ailand are junior synonyms of the widespread and conchologically variable Corbicula Corbicula fluminea (Muller)). ii i.百 le majority of specimens could be identified without difficulty to far 凶ly level using using North Am erican ， European and Australian keys. Wi 血 some groups ，however ，identification to family level was impractical. Th us members of the Phylum Nematoda ，Classes Copepoda and Ostracoda ，Subclass Oligochaeta ， Orders Orders Cladocera and Collembola 加 d Suborder Hydracarina were identified no further 由加 these higher taxa. Th emo 中hological characters used in keys did not allow some specimens to be assigned to to a single family with confidence ， though frequently all but two or three families could

be excluded. Thi s difficulty only occurred with certain groups 佃 d 血ese were amalgamated to to form composite taxa ， as follows: ODONATA Amphipterygidae Amphipterygidae + Euphaeidae → Amp hA uph Coenagrionidae Coenagrionidae + Platycnemidae → Coe nIP lat Corduliidae Corduliidae + Li bellulidae → Cor dIL ib DIPTERA Empididae Empididae + Ephydridae → Emp iA phyd TRICHOPTERA Hydropsychidae Hydropsychidae + Arctopsychidae → Hydro/Arc (Arctopsychidae was most probably only only present in samples taken above 1000 m on Doi In 白anon) Odontoceridae Odontoceridae + Brachycentridae → Odo n/B rach Polycentropodidae Polycentropodidae + Stenopsychidae + Dipseudopsidae → Poly/Ste n/D ip EPHEMEROPTERA Baetidae Baetidae + Siphlonuridae → BaetlSiph

In In the following text ，when reference is made to the families recorded ， the term 232 S百 PHEN E. MUSTOW

“f創凶ly" is in c1 usive 'O f the arnalgarnated taxa and higher taxa n'O t identified t 'O far 凶ly leve l. 百leprim 紅 y 'O utput 企om 出e macr 'O invertebrate sarnpling prograrnme was a data ma 凶 x， 102 102 sarnples x 116 farnilies in size. Data fr 'O m all sarnples fr 'O m each site were subsequently c'O mbined t 'O reduce any effects related t'O白 .e seas 'O n in which samples were c 'O llected (n 'O te that that the results 'O f an analysis 'O f seas 'O nal differences in the c'O mmunities ， using the unc 'O mbined data set ，釘 e presented by MUSTOW ， 1997). An envir 'O nmental data set c'O rresp 'O nding t'O血 is m 'O dified bi 'O l 'O gical data set was pr 'O duced f'O r use in multivariate analysis. analysis. Th is c 'O nsisted 'O fc 'O mbined da 匂 f'O r each site and c 'O ntained mean values 'O f pH ， c'O nductivity ，tempera 旬re ，vel 'O city ， width and depth ，minimum values 'O f DO c'O ncentra- ti 'O n，and values 'O f altitude and sl 'O pe calculated 企'O m maps. It als 'O c 'O ntained n'O minal values values indicating whether sarnples were 合om River Ping shall 'O w sites ，Ri ver Ping deep sites sites 'O r 血 e Kh a Canal (blank values were rec 'O rded f'O rD 'O i In由加'O n Gr 'O up sites in 'O rder t 'O f'O ll 'O w the f'O rmat required in multivariate analysis). Di versity was measured using the Shann 'O n-Wiener diversity index (SHANNON & WEA VER ，1949) ， values 'O f which are calculated using the f'O ll 'O wing equati 'O n: Shann 'O n's H' = -I: Pj*ln(Pj) where Pi is 血 e rati 'O 'O f the i-th species abundance t'O血 e sum 'O f abundances 'O f all species in in the p紅 ticular s創 nple. Shann 'O n's H' c'O uld 'O nly be calculated f'O r semi-quantitative data sets which were 'O nly available available f'O r shall 'O w sites. Th is diversity index is derived fr 'O m inf 'O rmati 'O n 血 e'O ry and utilises utilises the distributi 'O n 'O f the numbers 'O f individuals per species in calculating values. Differences Differences in macroinvertebrate c'O mmunity s位ucture arn 'O ngst sarnple sites ， in relati 'O n t 'O envir 'O nmental variables ， were investigated using the macr 'O invertebra 飽 and envir 'O nmental data data sets. 百le c'O mputer progr 創 n CANOCO v.3.10 (τER BRAAK ，1987-1992 ， 1990) was used used t 'O c紅 ry 'O ut Can 'O nical C 'O rr 田 p'O ndence An alysis (CCA). Th e 'O pti 'O ns used in 白 is analysis analysis were: tax 'O n'O mic data 住ansf 'O rmed t 'O presence/absence f'O rmat ，n 'O specificati 'O n 'O f farnily-weights farnily-weights 'O r sarnple-weights ，n 'O d'O wnweighting 'O f rare farnilies ，and far 凶ly sc 'O res were weighted me 佃 sarnple sc 'O res. CANOCO aut 'O matically tested 血 e envir 'O nmental variables variables f'O rc 'O linearity (n 'O ne was detected). Environmental variables were f'O rwardly selected selected t 'O find a mi 凶mal set 'O f variables 由 at explained the farnily data virtually as well as 出 .e full se t. CANOCO 飽:sted at each step whether the variable t 'O be added was statistically significant significant (p < 0.05) ， using aM 'O nte Carl 'O permutati 'O n tes t. The 'O utput diagrarn displayed an an 'O rdinati 'O n 'O f bipl 'O t sc 'O res 'O ff 'O rwardly selected envir 'O nmental variables (represented byarr 'O ws) ，組 ds 創 nple sc 'O res ， which are linear c'O mbinati 'O ns 'O f envir 'O nmental variables and weighted averages 'O f farnily sc 'O res (n 'O te 白紙白ec 'O rresp 'O nding farnily bipl 'O t is presented presented by MUSTOW ， 1997).

RESULTS

Physico-chemical Physico-chemical Survey

The maximum and minimum sp 'O t values (unc 'O mbined data) 'O btained at different groups groups 'O f sites during the physic 'O -chemical surveillance pr 'O grarnme are sh 'O wn in Table LOTIC MACROINVERTEBRATE ASSEMBLAGES IN NORTHERN THAILAND 233

3. 3. At most sites substantial seasonal variation in river dep 曲 was observed ，although width remained remained relatively constant due to the presence of steep banks ，either natural or artificia l. On the Ri ver Ping below P5 and on 由e Kh a Canal ， a series of weirs had been installed which which artificially raised the depth at sites P6- 10 and PK 1. Th e substrates at the lowest five sites sites on the River Ping and at PKl were depositing. Those at the other sites were predominan t1 y eroding. Water tempera 加 res at Ping Group sites ranged between 19 and 34 0 C (Table 3). A wider wider range ，9 to 28 ・C ，was observed on Doi Inthanon (Table 3). A clear downstream increase increase in temperature was observed on Doi In thanon ， with me 加 temperature at the lowest lowest two sites being 11 oC greater 血an at the highest site. Mean conductivity values were higher higher for Ping sites P2-P4 ， than for other sites on the Ri ver Ping and Ri ver Taeng. Conductivity Conductivity levels on the Kh a were considerably higher than those recorded at all other sites sites (Table 3). There was a relatively steady downstream increase in mean conductivity values values on Doi Inthanon. Data on calcium hardness were in agreement with the conductivity data ， with elevated levels occu 凶 ng at ups 紅白m sites on the Ri ver Ping ， and sites on Doi In 出anon ， in particular those at high altitude ， being infertile (Table 3). At all Ri ver Ping sites sites mean DO concentrations were > 5 mg 1- 1 and 白ey were slightly higher at shallow sites 由加 at deep sites. Only at PI0 did the minimum r，配 orded DO concentration drop below below 4 mg 1" 1， to 1. 5 mg 1・1. DO levels on the Kh a Canal were considerably lower than those those on all other rivers (Table 3). At Doi Inthanon Group sites ，mean DO concentrations were were above 8.0 mg 1" 1，other 血an at K6 where the mean value was 6.5 mg 1" 1. Water at every every site was slightly alkaline ， with the mean pH 7. 0- 8.0 ， except for KC ， the highest site on Doi Inthanon (mean pH 6.5). Both ni 回 te nitrogen and orthophosphate concentrations were were considerably higher on 出e Kh a Canal 白an on the Ri ver Ping (Table 3).

Macroinvertebrate Macroinvertebrate Survey

Table Table 4 shows the macroinvertebrate data amalgamated for each site. The total number of of families recorded at sites ranged from 25 at PKl to 70 at P 1. More than 45 families were distinguished distinguished at all but four sites. Of the nine insect orders recorded ， seven contained more 也加 two families (Trichoptera ，Plecoptera ，Odonata ，Hemiptera ，Ephemeroptera ，Di ptera 組 d Coleoptera). Figures 2 and 3 show the percentage composition of families in these seven seven principal orders. On the Ri ver Ping there was a similar pattem of percentage family composition at all sites ， with the notable exception that no Plecoptera were recorded from deep sites (Fig. 2). Th e pattem at the Ri ver Taeng site was similar ・to that at shallow Ri ver Ping sites ， but the Kh a Canal sites differed from all others in that Trichoptera were not recorded at either site ， and at PKl Ephemeroptera were also absen t. The pattem of percentage far 凶ly composition composition at Doi Inthanon Group sites was similar to 由 at Ri ver Ping shallow sites ， although although trichopteran and plecopteran families made up a relatively greater proportion of the the insect fauna ， while Hemiptera were less well represented (Fig. 3). There were no obvious obvious downstream changes. Bar charts were also drawn for those non-insect groups from which more than three families families were recorded (Hirudinea ，Decapoda ， [Pulmonata Gastropoda and Prosobranchia shown separately] and Bivalvia) (Figs. 4 and 5). The percentage composition of insect 234 STEPHEN E. MUSTOW

Table Table 3. Summary of physico ・chemical data.

Ri ver Ping Ri ver Taeng 回la Canal Doi In thanon Site Site Codes Group Shallow Shallow Sites Deep Sites PI-P5 PI-P5 P6 ー.PI0 円 PKl &P 回 KC-K6 Period Period when readings tak: en Sep 91- Sep 91- Sep 91- Dec 92- Sep 91- Apr 93 Apr 93 Apr 93 Sep 93 Apr 93 Number of sites 5 5 1 2 10 Al titude (m) 310-410 280-300 330 290-300 290-2100

Wid 血 (m) 16-40 35-111 7-15 1-23 2-35

Maximum dep 血 (m) 0.2 ・2.0 1. 0-2.9 0.3- 1. 7 0.1- 1.1 0.1- 1. 5

Main subs 位atum p紅 ticles pebbles & silt & sand & silt ， sand pebbles ， cobbles cobbles sand gravel & gravel cobbles & boulders boulders Air Air temperature ("C) 15-37 16-38 25-37 26-36 8・35

Water Water temp 町 a仰向("C) 19 ・31 21-30 21-34 23 ・31 9・28 Secchi Secchi depth (m) 0.06-0.62 0.1 1- 1. 00 0.08-0.64 0.34-0.57 0.10 ・0.70

Current Current velocity (m S-I) 0.1- 1.1 0.0-0.6 0.2- 1. 0 0.0-0 .4 0.0 ・1.1 Conductivity Conductivity (μS) 150-430 160-260 100-180 250-640 5・170 Calcium Calcium hardness 61. 5-115 .3 59.5-75 .3 49 .5 -59.5 ND-58.5 (ppm (as CaC0 3 ))1 Di ssolved oxygen (mg 1・1) 5.8-12 .3 1. 5・8.5 6.5 ・10.1 0- 1. 8 4.7 ・13.9 Di ssolved oxygen 67-142 20-114 83 ・139 0-25 51 ・152 (percentage (percentage saturation) pH 6.7-8.8 6.6-7.9 6.7 ・8.3 6.9-8.1 5.1 ・8.5

Ni 住ate nitrogen (mg r1) 3.8 ・5.2 7.9-15.9 0 同 lophosphate (mg 1・1) 0.4 3- 1. 06 2.88-6 .4 8

Values Values are maximum and minimum values (uncombined d制) recorded during 肱 sampling programme. 'Readings 'Readings taken by Chiang Mai U 凶versity' s chemis 町 dep 釘 tment in August 1988 ，November 1988 and April 1989. 1989. ND = non detectable LOT IC MACR Of NVERTEBRATE ASSEMBLAGES IN NORTHERN THAILAND 235

100%

80% 回 Trichoptera

口P le ∞ptera

60% ~ Odonata

• Hemiptera

40% 冨 Ephemeroptera

~ Dipte 悶 20% 関 Coleoptera

0% Na門 オ仏 ト仏凶乱@仏h Faa 円仏a∞ oaFxaNxa OFa

FigUI 巴 2. Percentage cO l11 posit ion of fa l1l il i巴s in principal insect orders ，P in gG roup . Thel 巴 is as imil ar pattern of of percentage fam il y compo siti on at all River Ping sit es (P I-P IO ) and on th 巴 River Ta 巴ng (PT) ，wit h the the imp ort ant excep ti on that PI巴coptera were n ot record 巴d fro l11 d巴巴 p site s (P6-P IO ). K ha Cana l sites (PKI & PK2) differ from al l ot hersi n that Tr ichopte ra were n ot reco rd ed at 巴ith 巴r s ite and at PK 1 Ep h巴me roptera were al so absent

100%

回 Trichoptera 80% 口Plecoptera

60% ~ Odonata

• Hemiptera

40% 冨 E phemeroptera

~ Diptera 20% 盟 C oleoptera

0% OX FMVLFX NX 刊戸 門戸〉占円 守 町 cx X VL 一 V X 品

Figur 巴 3. P巴rcentage cO l1l pos iti on of fa l1l ilies in principal insect orde rs， Doi lnthano n Gro up . Th 巴r巴 is as imil ar pattern pattern of perc 巴ntage fami ly composit i on at all Doi lnthanon Group sites. The patt 巴rn iss il1l il ar to that obs 巴rved at River Ping shall ow sit 巴5 236 236 STEPHE N E. MUSTOW

100%

口Insecta 80% 冨 H irudin ea

60% ~ Decapoda

• Gastropoda (Pulmonata) (Pulmonata) 40% 凹 Gastropoda (Prosobranchia) (Prosobranchia) 20% 鴎 Bivalvia

0%

~ N c')寸ト町田トー∞CJ) ~ N 門 c.. c.. c.. c.. c.. i:l.. c.. a.. i:l.. C:: ii :i.:: s.2 ζ c.. c.. a:: c..

Fig llr e 4 . Percentages of in sec t fami li es and families in se lect 巴d non-insect grollps ， Ping Group. On the Rivel Pin g the ratio of the numb er of fallli li es in th 巴 non-insect groups to th 巴 nUlllb 巴r of insect families was gI巴 atest at th 巴 de 巴p downstream sit 巴s (P6-P l0 ). Th is was primarily due to an incr eas 巴 in th e re lati ve abllndance abllndance of fami li es of 1110 1l us cs and 1巴ec he s.The Kha Canal sites ，PKl and P K2， di 仔巴 r from a1 1 0 出巴rs in that bivalve s wer 巴 not 1巴cor ded at 創出巴r Slt 巴 Also ， at PKl d巴capods were not recorded ，

w hi ch were pl 巴sent at all other Pin g Group s it es. The River Taeng sit e (PT) is similar in composition to to the s hallow Ri ver Ping sites (Pl-P5)

100% 「ーー 一一 ーー--， r-i r-1 i 一 「ーー ーーー ーーー

口Insecta 80% 畠 H irudinea

60% ~ Decapoda

• Gastropoda (Pulmonata) (Pulmonata) 40% 凹 Gastropoda (Prosobranchia) (Prosobranchia) 20% 圏 Bivalvia

園周囲 障置 0% E 璽 望盟思 齢 屋露 :: ~ ~ ~円円、才師<0 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Fig llr e 5 P巴rce nt ages of insect farnil ies and fa m.ili es in s巴lected non-insect gro up s，Doi Inthanon Group. The ratio ratio of the nllmb 巴r of families in non-in sect groups to 出巴 number of in s巴ct fam ili es incr 巴ased wit h

decn 邑asing altitud e (i巴 between KC a nd K6). Biva l ves occ urr 巴d at all site s，w hil e gast :r opods were only only recorded below Kl ，d eca pods on ly below Kt2 and l eeches only at the l owest sit巴， K6 . Farni lie s in in th 巴 select 巴d non-in sect groups were poorly repr 巴S巴nted compared to Pin g Group sites ， other than at at the two l owest site s (K5 & K6) LOTIC MACRO 別 VERTEBRATE ASSEMBLAGES IN NORTHERN THAILAND 237

families families was included in these charts ， in order to indicate changes in the ratio of 由e number of insect families to the number of non-insect families. On the Ri ver Pi ng ， the ratio of the number of families in the selected non-insect groups groups to the number of insect 加国lies was greatest at 白e deep downstream sites ，P6 ーPI0 (Fig. (Fig. 4). 官邸 was primarily due to an increase in the relative abundance of families of molluscs molluscs and leeches.τ 'h e percentage composition of families at the Ri ver Taeng site was similar similar to that at the sh a1 10w Ri ver Ping sites ，PI-P5.τ 'h e Kh a Can a1 sites ，PKl and PK2 ， differed differed from all others in 白紙 bivalves were not recorded at either site. Also ， at PKl decapods decapods were not recorded. These were present at a1 1 other Ping Group sites. Perlidae 伊lecoptera) ，Simu 脳dae (D iptera) ，Ephemerellidae ，Pro sopistomatidae (b oth Ephemeroptera) ， Aphelocheiridae Aphelocheiridae (Hemiptera) and Psychomyudae (Trichoptera) appeared at every Ri ver Ping Ping shallow site ， but were absent from River Ping deep sites (Table 4). In contrast ， Cor a1 1anidae (Am phipoda) and Ampullariidae (Gas 住opoda) occurred at every Ri ver Ping deep deep site ， but were absent 企om Ri ver Ping shallow sites (Table 4). On Doi Inthanon ，other 出an at 白e two lowest sites ， the ratio of the number of families in in the selected non-insect groups to the number of insect families was lower 血an at Ping

Group sites (Fig. 5). 官 le ratio increased wi 血 decre 部 ing a1 titude and there were a1 titudin a1 differences differences in distribution. Bivalves occurred at a1 1 sites ， while gas 住opods were on1 y recorded recorded below Kl ， decapods only below Kt2 and leeches only at the lowest site ， K6. Al l bivalve bivalve molluscs were in 血e f: 創凶ly Pisidiidae ，other 由加 at the lowest two sites. Th e limited limited occu 町'ence of non-insect families at Doi Inthanon Group sites ，comp 紅 ed to Ping Group sites ， can addition a1 1y be appreciated 血rough observation of 血e upper qu 訂 tile of Table Table 4. Th e most abundant taxa at shallow sites (semi-quantitative data were not collected from from deep sites) were Elminthidae (Coleoptera) ，Chironomidae ， Simuludae (bo 白Di ptera) ， Baetidae/Siphlonuridae Baetidae/Siphlonuridae (Ephemeroptera) ， Corixidae (Hemiptera) and Ostracoda.τ 'h ese appeared appeared at more 血an 10 individu a1 s per 3・min kick sample at two or more sites (Table 4). 百le higher taxa which occurred at greatest abundance in samples were the Coleoptera ， Diptera ，Ephemeroptera ， Hemiptera and Trichoptera. Shannon diversity (H') ，ca1 culated for sites where semi-quantitative data were ob 凶 ned ， ranged ranged between 1. 2 and 1. 5 at Ri ver Ping shallow sites ， and between 1.1 and 1. 9 at Doi h 白血'O n Group sites (Table 4). At sites on the Ri ver Kl ang ，diversity increased from 1. 2 at at Kl to a maximum of 1. 6 at K2 and then decreased progressively downstream to a minimum of 1.1 at K6. Di versity at PK2 on 出e Kh a Can a1 (0.7) ，was considerably lower 出叩 at a1 1 other sites. τ'h e ftrst (horizon ta1)蹴 is (λ1 (frrst eigenvalue) = 0.273) of the CCA ordination diagram (Fig. (Fig. 6) clearly separates Doi Inthanon Group sites ， Ping Group de 叩 sites 佃 d Kh a Can a1 sites 加to three clusters ，白us indicating differences in faun a1 composition. Sh a1 10w Ri ver Ping Ping sites a1 so form a separate cluster. This is ordinated more closely to low a1 titude stations stations on Doi Inthanon and to the Ri ver Taeng site ，出血 to 血e deep River Ping sites. Th e four forwardly selected environmental variables which best explained the differences in in macroinvertebrate composition were conductivity ，temperature ，pH and velocity. The directions directions of the environment a1 arrows in the ordination diagram show that samples 合om the the following sites were associated with the fo l1 owing environment a1 variables: Ri ver Ping deep deep sites 佃 d Kh a Canal sites with higher conductivity; Doi Inthanon Group low a1 titude 238 STEPHEN E. MUSTOW

Table Table 4. Shannon diversity and families occurring in combined samples for each site.

Site 唱

Pl Pl p2 P3 P4 P5 P6 I円 P8 p9 PlO 円 PKl P K2 KC Ktl Kl K2 Kt2 Kt3 K3 K4 K5 K6 T悶CLADIDA Dugesiidae Dugesiidae 。。 。 。。 。 01 7 NEMATODA 。。 。。 。+ + 。。 。。 11 OLJGOCHAETA 21 2 41 3 21 + +1 + +1 + 。+ 31 1 21 0 21 0 11 0 01 1 8123 HIRUD 別EA Erpobdellidae Erpobdellidae 。 。 2 Glossiphoniidae Glossiphoniidae +1 + + + 01 5 Hirudidae Hirudidae + + 2 Piscicolidae Piscicolidae 。。 +1 + +1 + + + 8 BIVALVIA BIVALVIA Amblemidae Amblemidae 。+ +1 + +1 + 6 Corbiculidae Corbiculidae 41 3 21 3 31 + +1 + +1 + 。 。。 13 Pisidiidae Pisidiidae 。。 01 1 01 4 01 2 8 GASTROPODA (PROSOBRANC 阻A) pullariidae Am pullariidae +1 + +1 + + +1 0 7 Bithyniidae Bithyniidae 。+ +1 + +1 + 。 7 iaridae Th iaridae 61 7 7116 91 + +1 + +1 + 。。 01 7 。。 11 17 Viviparidae Viviparidae 。。 +1 + +1 + +1 0 。 0110 GASTROPODA (PULMONATA) (PULMONATA) Ancylidae Ancylidae 。。。 +1 + +1 + + 。 0110 Buccinidae Buccinidae 。 。 +1 + +1 + + 7 Lymnaeidae Lymnaeidae 。。 。。 。+ +1 + +1 + 。+ 。 0114 Planorbidae Planorbidae 。。 。。 11 + +1 + +1 + 。。 11 3 01 15 HYDRACA 悶NA 。。 。。 。+ +1 + +1 0 + 。。 。 01 15 CLADOCERA +1 + + + +116 。。 8 OSTRACODA 121 2 21 12 11 + +1 + +1 + 34 8 11 0 。。 。。 01 1 11121 COPEPODA +1 + 8 3 AMPHIPODA Co raJ lanidae +1 + +1 + + 5 Talitridae Talitridae +1 + +1 + +1 0 6 DECAPODA Atyidae Atyidae 。。 。+ +1 + +1 + 。。 10 Palaemonidae Palaemonidae 。。 。。 。+ +1 + +1 + 11 0 11 0 01 15 Parathelphusidae Parathelphusidae 。。 。。 。+ +1 + +1 0 。 41 0 13 Potan 泌総 。。 2 COLLEMBOLA 。。 。。+ +1 + +1 0 。。 。。 。。 。。 17 MEGALO 円'E RA Corydalidae Corydalidae 。。 。。 01 1 。。 。 9 Sialidae Sialidae + 。 2 EPHEMERO 阿'E RA BaetlSiph BaetlSiph 26 30136 20143 +1 + +1 + +1 7 3120 24 48 27 15117 23 28 46 7122 Behningiidae Behningiidae 。 。 2 Caenidae Caenidae 31 4 21 3 91 + +1 + +1 + 3 01 1 11 3 31 3 11 8 19 LOTIC MACRO 町 VERTEBRATE ASSEMBLAGES IN NORTHERN THAILAND 239

Sites Sites

PI PI n P3 P4 P5 尚 p7 問 1'9 1PIO I'f PKI IP K2 KC KtI KI K2 Kt2 Kt3 幻 K4 K5 K6 Ephemer 官Ui dae 31 8 31 1 。。 11 2 11 3 21 0 11 0 。 15 Ephemeridae Ephemeridae 。。 。。 。+ +1 + +1 + 。。 11 1 41 7 。。 19 Heptageniidae Heptageniidae 。。 11 1 11 + +1 + + 。 21 5 21 1 21 5 21 2 21 0 20 ptophlebiidae Le ptophlebiidae 31 3 21 1 。+ +1 + +1 0 01 1 11 1 31 4 21 2 01 2 20 Oligone 町iidae 。 。 2 Potamanthidae Potamanthidae 11 0 。 +1 0 11 0 。。 9 Pro sopistomati 血e 。。 。。 。 。 6 Tricorythi 血e 。。。。。。 。 7 ODONATA Aeshnidae Aeshnidae 。。 。。 01 1 。。 。 9 Amp hA uph 。。。 。。 。。 。 8 C刻op 旬rygidae 。。 。。 +1 0 01 1 11 0 。。 12 Chlorocyphidae Chlorocyphidae 。。 。。 +1 + +1 + +1 0 。。。 01 14 Coe nIP lat 。。 。。 +1 + +1 + +1 0 +1 0 。。 。。。 17 Co rdlL ib 。。 01 1 。+ +1 + +1 + 。。。。 。。 01 18 Cordulegastridae Cordulegastridae 。。 3 Gomphidae Gomphidae 。。 11 1 。+ +1 + +1 + 01 1 。。 11 1 01 2 11 1 11 22 Mac lO miidae 。。 + +1 + 。 01 1 。。 01 11 Pr otoneu ri<也 E 。。 01 1 。+ +1 + +1 + 。。 01 13 PLI 詑O何百RA Nemouridae Nemouridae 61 1 。。 。。 6 Peltoperlidae Peltoperlidae 。。 。。 4 Perlidae Perlidae 11 1 21 1 。 21 3 21 2 41 1 11 1 41 0 16 HEMlPTE RA Aphelocheiridae Aphelocheiridae 11 1 11 0 。。 01 1 11 1 11 0 11 0 11 0 16 Belostomatidae Belostomatidae 。 。 + + +1 1 6 Corixidae Corixidae 。。 01 1 121 + +1 + +1 + 28 +1 0 01 1 。。 71 1 71 6 21 Ge 凶dae 。。 01 1 。+ +1 + +1 + 01 1 11 0 。。 01 1 。 0121 Hebridae Hebridae 。。 + 。 。。 6 Hydrome 凶dae 。 + +1 + + 。 。。 8 Mesoveliidae Mesoveliidae 。。 。。 。+ +1 + +1 + 。+ 。 13 Naucoridae Naucoridae 。。 。。 。+ +1 + +1 + 。。。。 11 1 。。 。。 20 Nepidae Nepidae 。。 +1 + +1 + 。+ 。。 。 11 Notonecti 伽s 。。 。。 +1 + +1 + + + 。 。。 01 14 Pleidae Pleidae 。。 11 0 。+ +1 + +1 + 。+ 。。。 01 1 11 0 。 0121 Veliidae Veliidae 。。 。。 。+ +1 + +1 + 。 01 1 01 1 。。 17 LEPIDO P'回 RA 。 町凶}也 E 。。 01 1 +1 + +1 + +1 0 。。 。。 。。。 01 19 T悶αIO 円'E RA Calamoceratidae Calamoceratidae 01 2 。。 01 5 Ec no 凶 dae 。 + +1 + 4 Glossosomatidae Glossosomatidae 。 01 1 。。 。 6 Goeridae Goeridae 11 1 41 1 01 1 。 7 Helicopsychidae Helicopsychidae 。 Hy 伽仙t 41 3 21 0 11 + +1 + +1 0 11 4 21 1 11 1 11 1 21 0 20 Hydroptilidae Hydroptilidae 11 1 11 1 。 +1 2 。。 11 0 。。 14 pidostomatidae Le pidostomatidae 。 21 2 11 2 31 0 8 ptoceridae Le ptoceridae 。。 01 1 。+ +1 + +1 + 。。 01 3 11 6 61 2 。。 21 240 240 S百 PHEN E. MUSTOW

Sites Sites

PI PI n 問 P4 P5 尚 p1 P8 " PlO PT PKI P K2 KC Ktl KI K2 Kt2 Kt3 K3 K4 防 K6 Li mn 悶 ntropodidae Molannidae Molannidae 。。。 3 Odo nIB rach 11 0 01 1 。。 01 2 。。 。 0112 凶 。。 。。 。 Philopo nidae 。 11 0 01 1 9 P同E佃 eidae Poly/Ste nID ip 。。 。。 +t + +1 + + 11 1 01 1 11 0 。。 0118 Psychomyiidae Psychomyiidae 。。 。。 。 。。 11 1 11 1 。。 13 則lyacoph 出dae 11 0 2 Uenoidae Uenoidae COLEOPTERA Chrysomelidae Chrysomelidae 。 。 2 Curculionidae Curculionidae 。 + + 。。。 6 Dryopidae Dryopidae 。。 。。 + 。 11 1 01 1 31 0 。。 0115 Dytiscidae Dytiscidae 。。 111 。+ +1 + +1 + 。+ 。。 。 。。 。。 0120 EI 凶n血idae 16112 181 8 11 + +1 + +1 + 01 2 61 10 51 6 51 7 41 2 5122 Gyrinidae Gyrinidae 。。 。。 。 + 。 11 1 11 0 。。 13 Haliplidae Haliplidae 。 Helodidae Helodidae 。。 。。 +1 0 。 11 1 。。 11 0 。 14 Hy 世aem 白E 。 Hydrophilidae Hydrophilidae 。。 。。 。+ +1 + +1 + 。+ 11 0 11 1 01 2 21 1 。。 0123 L叩 p戸dae 。。 。。 + 。 6 P間phe 凶dae 11 0 。。 。+ +1 + 。。。 11 1 11 0 0116 Pti l叫 ctylidae 。。。 3 DIPTERA DIPTERA Athericidae Athericidae 。。 11 0 。。 7 Blephar 百ceridae 。 Cerato 卯Igonidae 01 1 01 1 。+ +1 + +1 + 。+ 01 1 11 0 11 1 11 1 。。 0123 aoboridae Ch aoboridae + Chironomidae Chironomidae 8114 11117 101 + +1 + +1 + 151 + 58128 18114 22 20118 24 30 19146 23 Culicidae Culicidae 。 。+ +1 + +1 + 。+ 。。 0112 Dixidae Dixidae 。。 。 4 Dolichopodidae Dolichopodidae 。 。。 。 4 Emp iA phyd 。。 01 1 。+ +1 + +1 0 +1 0 11 1 11 0 。。 。 19 Muscidae Muscidae 。 。 + + 。 5 Psychodi 伽e 。 + +1 0 +1 0 。。。 。。 11 Sciomyzidae Sciomyzidae + 。。 3 Simuliidae Simuliidae 01 1 。。 。 。 241 12 61 9 111 5 21 5 11 0 16 S甘'atiomyidae 。。。 +1 + +1 + +1 0 +1 1 。 12 Syrphidae Syrphidae +1 0 2 Tabanidae Tabanidae 。。 。 + 。。。 。。 。。 。 12 Tipulidae Tipulidae 11 1 11 0 11 + +1 + +1 0 11 1 11 1 11 1 11 0 41 0 20 Number Number of farnilies 70168 57 64155 61149 58 57165 56125 43 38152 54 56 57 66 60 50 40 47 Shannon Shannon H' 1. 4 1. 4 1. 3 1. 5 1. 2 1.1 0.7 1. 5 1. 8 1. 2 1. 6 1. 9 1. 7 1. 6 1. 5 1. 2 1.1

Numbers represent percentage abundance for semi-quantitative data ，to 血 e nearest whole number (hence numbers less 白an 0.5 are rounded to 0; note 曲 at diversity was c a1 culated using non-rounded data); + = present for qu a1 iぬ.t ive data. LOT!C MACROINVERTEBR ATE ASSEMBLAGES rN NORTH ERN THAILAND 241

0 KC ..... +

~Kl

•P K2

C nd -1.0 +1.0

Vel KEY Temp River Ping shallow sites \ • pH River Ping deep sites • River Taeng site T Kha Canal sites + 0 Doi lnthanon Group sites ...... I Environmental variables ~

Figure 6 CCA ordination diagram of sample and environmental biplot scores = 0.273 , A. = 0.127). C\ 2 242 STEPHEN E. MUSTOW

sites sites and River Ping shallow sites with higher velocity ，Ri ver Ping shallow sites and 出e Ri ver Taeng with higher pH ， and River Ping sites in general with higher temperature.

DISCUSSION

Physico-chemical Physico-chemical survey

The temperature range was similar to 出at of other tropical rivers and lakes. BISHOP (1 973) ， for example ， recorded temperatures in the range of 18. 0- 34SC along a stream in Malaysia Malaysia below 250 m in altitude ， using weekly maximum-minimum temperature readings over over a 60-week period. CROWTHER (1982) found 出at average temperaωres of rivers at midday in areas three of Malaysia ranged from 24.0 to 30 .4 0 C. BISHOP (1973) predicted 出at temperature in headwaters at >1000 m in Malaysia might be as low as 15 0 C ，from consideration consideration of the adiabatic lapse rate. 百le present study shows 出at minimum temperatures at at around 1000 m do reach this level and 白at at >2 ，000 m they fall as low as 9 0 C. Elevated Elevated levels of conductivity ， calcium hardness and pH at upstream Ri ver Ping sites were attributable to an input of calcium and bicarbonate ions from an area of limestone in the the vicinity of Chiang Dao. Low conductivity and calcium hardness of the water at Doi Inthanon Inthanon group sites suggest 白at 出e water is infertile ，particularly in the high altitude zone where levels were lowes t. The lowest pH was recorded at the highest site on Doi Inth 加 on ， where conductivity ，and hence buffering capacity ，was very low. Conductivity data only provide provide evidence of significant pollution on the Kh a Cana l. The high conductivity levels recorded recorded on the Kh a Canal were a result of inflows of domestic and industrial wastewater and and irrigation drainage water. Nutrient measurements ，albeit from a single occasion ，indicated an an enriched state of the Ri ver Ping and ， to an even greater extent ， the Kh a Cana l. There There was evidence of a sustained deficit in DO where mean values fell below 8.0 mg 1- 1. At the deep Ping sites and K6 ， the deficit was probably mainly due to the fact that water water velocity was lower and depth was greater than at other sites. This would result in decreased decreased turbulence and therefore decreased physical aeration of the water. However ， inputs inputs of organic pollution from the city of Chiang Mai and from Chom Th ong town may have depleted DO levels further ，by increasing levels of microbial respiration. The lowest DO concentrations on the Ri ver Ping were recorded at PI0 ， about 18 km downstream of the the organically polluted Kh a Canal inflow. On the Kh a Canal itself the DO deficit was severe ， as a result of the heavy organic pollution. Th e variation in DO concentration and conductivity conductivity observed at PK2 probably occurred because this site received water from the main canal and an irrigation outflow ， in variable ratios. Effects on the fauna are considered in in a later section. There There have been few studies on the effects of low oxygen concentration on the aquatic aquatic fauna of tropical rivers (examples include work by HASSAN ，1981 ，PEARSON & PEN 町 DGE ，1987 如 d REDDY & RAO ， 1991). Following a study on the effect of pollution by organic sug 紅 mill effluent on the macroinvertebrate fauna of a tropical Australian stream ，PEARSON & PENRIDGE (1987) proposed the following pollution categories: severe ， with sustained DO く 3.5 mg 1-1; moderate ，DO 3.5-5.0 mg 1-1; mild ，DO 5. 0- 6.5 mg 1- 1; and clean water with DO > 6.5 mg 1- 1. By these criteria the Ri ver Ping shallow LOTI C MACROINVERTEsRATE ASSEMsLAGES lN NORTHERN THALLAND 243

Fig Ul巴 7. S it 巴 P 1，River Pi ng，v i巴w clown- stream ，410 m above MSL ，m ea n iclth w iclth 22 m ，6 December 1 992. Rif- flecl flecl app 巴arance of wa t巴r incli ca t es

high high curr e nt v巴locit y ancl shall ow clepth clepth

F ig 山 e 8. Site PT ， River Taeng (tr i butary of the the Ri ver P in g) ，view up str ea m ，330 m above MSL ，m ea n wiclt h j 2 m ，6 Dec 巴mbe r j 992. Not 巴 gJan t gra sses on the ri ver ba n k. 244 STEPHEN E. MUSTOW

Figur e9 . S it e P8 ， River Ping ，v iew down- st.r ea m ，300 m above MSL ，m ea n

w id th 11 1 m ，7 Dec 巴mber 1992 No te urb an se ttin g.

Figur 巴 10 .Sit 巴 PK2 ，A nn of the Kha Cana l (tr ibutar y of th e R ive r Pin g) ，v iew do w nstre al11， 290 111 abo ve MSL ， l11 ean w iclth 3 111 ，7 Septe l11 ber 1993

Note ba l11 bo o SC I巴巴 ns ror trappin g fi sh. LOTIC MACRO INVERTEBRATE ASSEMBLAGES IN NORT HERN THAILAND 245

Figlll 巴 11. S it e PIO ，Ri ver Ping ，v iew lI P- str ea l1l tow a. rd s sit e，280 m above

MSL ，m e加 w idth 83 m ，7 De- cember 1992. At tim es of low f1 0w f1 0ating clllmp s of w ater hyac inth

so metlln 巴s cove r ed th 巴 water sur- fac e at thi ss it e

FA ー今ム 悶幻九児阻・坑戸別 obu ρ SHr--t岡 kmh--刊工rn mmukσ 引 巴wLH ωWnnH u 山 ' 出唱ゆ加 OIR Mmmmvna 引 6日 ，。Itrl 旧世沼崎 W d・- A 。 ・ 剖 e 町l 刷 246 STEPI -IE N E. MU STOW

Fi gur e 13. Sit 巴 Kt 2，tribut ary of lh e R ivel Kl ang，v iew ups tr ea l11 ，940 m abov e MSL ，m ea n w idlh 6 111 ，1 A pril 1993 ト

Fi gur 巴 14.Sit e K 6，Ri ver K lang，v iew down- str ea m ，29 0 111 above MS L ，m ea n w id th 1 6 111 ，26 July 1 992. Note

th 巴 turbidit yo f th e wate r at thi s

tim e of [巴lati v巴Iy hi gh flow LOTIC LOTIC MACROINVERTEBRATE ASSEMBLAGES IN NORTHERN THAILAND 247 sites ， the Ri ver Taeng and the Doi Inthanon Group of sites were clean ， although K6 was on the margin of being classified as mildly pollu 低 d. 百le Kh a Canal was severely polluted and and deep River Ping sites were mildly polluted ， with PI0 bordering on a moderate pollution classification. classification.

Macroinvertebrate Macroinvertebrate Survey

General General composition of the macroinvertebrate fauna

τ'h e general composition of macroinvertebrate assemblages recorded in 血is study was similar similar to 出at which would be expected in streams and rivers the world over (see DUDGEON ， 1995). Relatively few families have primarily tropical or subtropical distribu- tions. tions. The exceptions were: Corallanidae (Amphipoda) ， Corbiculidae (Bivalvia) ， Ampullariidae ，Thiaridae ， Buccinidae (all Gastropoda) ，Lampyridae (Coleoptera) ， Atyidae ，Palaemonidae ，Parathelphusidae ， Potamidae (all Decapoda) ，Pr osopistomatidae (Ephemeroptera) ，Amphipterygidae ，Euphaeidae ，Chlorocyphidae ，Macromiidae ， Protoneuridae Protoneuridae (all Odonata) ，Dipseudopsidae ，Li mnocentropodidae and Uenoidae (all Trichoptera) Trichoptera) (information on family distributions from BANARESCU (1 990 ，1991)). 百le main differences from temperate s甘'eams and rivers were similar to those recorded from tropical tropical Asian lotic systems in general (DUOGEON ，1995).τ 'h us ， there was relative under- representation representation of stoneflies (Plecoptera) and isopod and amphipod crustace 阻 s，佃da greater greater representation of f同shwater s胎imps ， prawns and crabs (Decapoda) in comparison with with temperate streams. Values Values of H' (range 0.7- 1. 9) were relatively low compared to values 血at have been recorded recorded by PINDER ET A ム(1 987) at a single site on a UK chalk stream. 百le range of values values of H' recorded on the chalk stream for different sample types ， using family level data ，was 0.63-3.76. However ，血 is does not n回 essarily indicate 白紙 diversity was lower on the Thai rivers as values of H' would have been artificially lowered because not all groups groups were identified to family leve l. P町 DER ET A L.' S (1987) study also demonstrated 血at values values of H' increased by approximately 15-110% when species level rather 血anfi 創国ly level level data were used.

Relation Relation to longitudinal and altitudinal gradients

Th ere were clear longitudinal changes in macroinvertebrate faunal composition along the the Ri ver Ping and the Ri ver Kl ang on Doi In thanon (Figs. 2-6). An abrupt transition took place place between the shallow ups 位eam sites and 血e deep downstream sites on the Ri ver Ping ， which was most clearly marked by the absence of Plecoptera and an increase in 血e number of families of molluscs and leeches at the deep sites. In con 紅ast longitudinal changes changes on the Ri ver Kl ang were gradual as i1l us 回.t ed by the res 凶 ction of gastropods to sites sites below Kl ， of decapods to sites below K t2 and of leeches to the lowest site ， K6. A large number of methods to classify river zones have been proposed (HELLA- WELL ，1986) ， based on physico-chemical features andlor on the distribution of faunal groups. groups. MALICKY & CHANTARAMONGKOL (1993) ， in their study of 白 e trichopteran fauna ofDoi In白血.o n， adopted an approach based on 且LIES' (1961) physico-chemical classification 248 S百 PHEN E. MUSTOW system. system. If the same approach is applied to the results obtained in 血e present study ，血 e highest highest eight sites on Doi Inthanon 訂 e cI assified as rhi 白ron (montane) and all others as potamon (foothill and plain). However ，there were no obvious changes in 血e composition of of the macroinvertebrate fauna associated with 血 is division. Indeed ，several of the rnid- altitude altitude sites on Doi Inthanon were found to have faunal compositions cI osely related to those those at 出e shallow Ri ver Ping sites. In contrast ，M 札 ICKY & CHANTARAMONGKOL (1993) deterrnined deterrnined changes in 白 e trichopteran fauna on Doi Inthanon at 血e species level ， based on the transition from rhithron to potamon. This suggests that 白e changes in faunal composition 紅 e subtle and may only be observed at the species leve l. However ， the usefulness usefulness of a rhi 出ron / potamon cI assification system is thus called into question ， if it does does not correlate with major changes in river faunas. Conductivity ， as related to dissolved calcium conc 泡n住ation ，would almost certainly be the the variable 白at deterrnined the downs 甘'eam increase in the numbers of farnilies of molluscs and crustaceans on Doi Inthanon. These animals require calcium to form shells and for many species the rninimum concentration required is around 20 mg 1・I (HYNEs ，1960) ，a level level which was only reached at the lowest sites on Doi In 出anon. At the highest three sites the the on1 y molluscs present were pea-mussels (Pisidiidae) ，one of the few types of molluscs to to occur in very soft waters (HY 阻 s， 1960). The actual pattems of altitudinal zonation observed on Doi Inthanon differed from those 血at have been recorded in the Hi malayas ， probably because in comparison to elevations elevations 白rther north ， the sumrnit of Doi Inthanon is at low altitude (Su 阻 N (1994) ， for example ， cI assified rivers at く 2，500 m as low altiωde). Thus in Nepal ，Li mnephilidae are characteristic characteristic of high altitude s仕e儲 ns ，whe 陀 as Caenidae ，Hydropsychidae ，Le pidostomatidae and Elminthidae are characteristic of low altitude streams (RUNDLE ET A L.， 1993; Su 阻 N ， 1994). On Doi Inthanon Li mnephilidae were not recorded in 出e present 蜘 dy (although (although adults have been captured (MALICKY & CHANTARAMONGKOL ， 1993)) and Caenidae ，Hydropsychidae ，Lepidostomatidae and Elrninthidae were present at 白e majority of of sites.

Taxonornic Taxonornic richness has also be 明 1 found to be negatively correlated to altitude in other p紅 ts of Asia (EGGLISHAW ， 1980; RUNDLE ET AL. ， 1993; SUREN ， 1994). Th is may be because ， as elsewhere in the world ， highland s住eams are generally smaller ， steeper and colder 出an those at lower altitudes (SUREN ，1994). Reduced taxonornic richness and diversity at at the lowest two sites (which were outside the national park) probably resulted from the effects effects of human disturbance of the catchmen t. Changes in land use were also found to influence influence faunal zonation in the Hi malayas (RUNDLE ET AL. ， 1993; SUREN ， 1994). On Doi In 也阻on ，al 由ough taxonornic richness changed with altitude ，relative abundance of 出e major major insect orders was sirnil 訂 at all stations ，a phenomenon also noted by SUREN (1994) 泊Hi malayan 紺 'eams. Th e abrupt downstream change in macroinvertebrate community composition observed on the Ri ver Ping (Figs. 2，4 & 6) could not be ascribed to a naωral progression ， as it was directly directly associated with the fact 白紙 the five sites furthest downs 位'eam on the Ri ver Ping were deep and slow flowing ， due to 出e presence of weirs. The principal effect was to shift the the fauna from one more characteristic of the rhithron to one more characteristic of the potamon. potamon. Th us several insect farnilies more typical of habitats with eroding substrates and high high water velocities (e.g. Perlidae ，Simuliidae and Prosopistomatidae) disappeared and LOTIC LOTIC MACROINVERTEBRA TE ASSEMBLAGES IN NORTHERN THAILAND 249

macroinvertebrates macroinvertebrates associated with depositing substrates and slow-flowing water ， in p副 icular molluscs ，became more abundan t.

旦酔 cts of pollution

The major dissirnilarity between the macroinvertebrate fauna of the two grossly polluted Kh a Canal sites ， and all other sites ，was lower family richness (particularly at PK1 ， the most polluted of the two sites). The following higher taxa were absent from the canal: Bivalvia ，Trichoptera ， Ephemeroptera (this order was pr 回 ent at PK2 ，however ， but was only only represented by Baetidae/Siphlonuridae) and Caridea. Also ，larvae of Syrphidae ， which are are aeropneustic and commonly associated with organically enriched water were only recorded recorded at the two Kh a Canal sites. These results are generally consistent with the well- known effects of organic effluents on temperate streams and thus agrl 田 with OUDGEON'S (1 992) statement that “ the effects of pollution in tropical Asian rivers 訂 e essentially the

same as those recorded in north 岨 temperate regions". However ， there are some differences between the detailed pattems observed in this study study and those which have been recorded elsewhere. Firstly ， there are zoogeographical differences differences in the taxa involved. For example ， the families Parathelphusidae and Protoneuridae ，which occurred on the Kh a Canal ， are not found in the north temperate zone. zone. Li kewise ， several of the taxa that were present elsewhere in the study area ， but were absent absent on the canal ， have a primarily tropical or subtropical distribution. Secondly ，a relatively relatively high number of taxa were recorded on the Kh a Canal ，despite the fact that 00 levels levels were extremely low. In Spain ， for example ， only five major macroinvertebrate groups groups were found at a site directly below a fish farm effluent (Oligochaeta ，Mollusca ， Hirudinea ， Oiptera and Megaloptera) (CAMARGO ，1992) ，compared to the 10 recorded at PKl and the 16 recorded at PK2. This was despite the fact that 00 levels were slightly higher higher on the Spanish river. Several tropical and subtropical studies have also revealed drastic drastic reductions in taxonomic richness associated with severe organic pollution. On a tropical tropical Australian river ， for example ，it was found that where 00 was sustained below 3.5 mg rl， the only taxa present were Oligochaeta ，Chironomus sp. and air-breathers (PEARSON & PENRIDGE ， 1987). In South Africa heavy organic pollution led to the replacement replacement of the normal fauna by a new association consisting mainly of larger Oligochaeta ，in cI uding Tub 俳'X spp. ， red Chironomus larvae and numerous ciliate protozoa (HARRISON ， 1959). In Nigeria the inflow of a sewage plant effluent led to the elimination of of all but five macroinvertebrate groups: Oligochaeta ，Oiptera ，Mollusca ，Odonata and Ephemeroptera ， with the former three dominant (HASSAN ， 1981). In an urban sewage canal in in tropical India ，however ， nine macroinvertebrate groups were recorded (Oligochaeta ， Ephemeropter 丸 Hemiptera ，Megaloptera ，Coleoptera ，Odonata ，Oiptera ， Hydracarina and Mollusca) Mollusca) (REDDY & RAo ，1991) ，a figure similar to that recorded at PK I. A simple explanation for the high number of taxa recorded from the Kha Canal may be 出at the submerged marginal vegetation was comprehensively sampled ， as well as the canal canal bottom. This led to the collection of neustonic dwe l1 ers (Collembola ，Mesove 1i idae ， Hydrometridae Hydrometridae and Gerridae) ，semi-aquatic forms (Ta 1i tridae ，Curculionidae ，Pyralidae ， E 中obdellidae ，Parathelphusidae) ，floaters with breathing tubes (most of the Di ptera) ，air- breathing breathing molluscs (Pulmonates and Ampu l1 ariidae) and swimmers with plastrons (many 250 STEPHEN E. MUSTOW

of of the Coleopteran adults). These could obtain oxygen directly from the atmosphere andl or or avoid critical conditions in the water. However ，it is possible that a greater number of taxa taxa actually do occur in heavily organically polluted rivers in Thailand than in other regions. regions. Further work on this subject is recommended. The results also demonstrate the importance importance of collecting samples from both the bottom substrate and the submerged marginal vegetation ， if a comprehensive survey is desired.

ACKNOWLEDGMENTS

The work reported in this paper was carried out while the author was based at Chiang Mai University (CMU) and contributed towards his extemal London University Ph.D. (MUSTOW ， 1997). He is grateful to the following for their invaluable assistance: Dr. R. G. Bailey Bailey (Ph.D. supervisor) ，Prof. W.P. Williams ， Dr. L.C. V. Pinder ，Ms Gotchagom Sannarm ， r. D r. R. S. Thome ， Dr. A. Rojanapaibul ， Dr. W. Wongkham ， D r. S. Brooks ， Dr. H. Malicky ， I.c. Dr. I.c. Campbell ， Dr. D. Dudgeon ， Dr. M.T. Gillies ，Mr. S. Butler ， Prof. P. Zwick and Dr. Dr. J. Weaver. Financial support was provided by Voluntary Service Overseas ， the Department Department ofTechnical and Economic Cooperation (Thailand) ，CMU ， the British Ecological Society Society (through a Small Ecological Projects Grant) and the British Embassy ，Bangkok.

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