Joumal of the American Mosquito Contol Association, 15(2):92-97, 1999 Copyright A 1999 by the American Mosquito Control Association, Inc. MOSQUITO AND AQUATIC PREDATOR COMMUNITIES IN GROUND POOLS ON LANDS DEFORESTED FOR RICE FIELD DEVELOPMENT IN CENTRAL SULAWESI. INDONESIA M. MOGI,' T, SUNAHARA'AND MAKMUR SELOMO, ABSTRACT, Aquatic habitats, mosquitoes, and larvivorous predators were studied on deforested lands in Central Sulawesi, Indonesia. Open ground pools, mainly in depressions made by the treads of bulldozers and other heavy equipment, were numerous but because of their small size, comprised ca. lEo or less of the total area of the deforested lands studied. The dominant mosquitoes in these pools were Anopheles vagus, Culex vishnui, Culex tritaeniorhynchus, and Culex gelidus. The lst 2 species were dominant in clear pools, whereas the latter 2 species were dominant in turbid pools. The dominant metazoans other than mosquitoes were Crus- tacea, Ephemeroptera, and Chironomidae. Both aquatic and surface predators were abundant. Dominant among aquatic predators were Anisoptera and Zygoptera nymphs, Dytiscidae, and Notonectidae. These results are discussed in relation to mosquito control on deforested lands that transitionally but inevitably appear during the course of rice field development projects in Indonesia. KEY WORDS Deforestation, mosquito, Anopheles, Culex, aquatic predator, Indonesia INTRODUCTION immediately follows deforestation, malaria epidem- ics may occur within a few months after settlement Development of irrigated rice field systems on (Partono et al. L973). Mosquito control should be deforested lands brings about drastic changes in the started at the early phase of development projects. environment. Closed forest ecosystems are even- The Government of Indonesia has promoted tually replaced by open rice agroecosystems inter- health programs in settlement areas to overcome spersed with farm villages. The transition phase be- disease problems that may hamper development tween these 2 sharply contrasting landscapes may projects (Binol 1983). However, in the case of mos- last for months or even years once a project is be- quito-borne diseases, basic information on mosqui- gun. The present study focuses on mosquito and toes and their ecology in project areas in eastern aquatic predator communities occurring during one Indonesia is virtually nonexistent. One reason for of the subphases of this transition between prede- this gap is that remoteness of such project areas velopment forests and postdevelopment rice lands. impedes surveys. Mosquitoes in forest and rice ecosystems are The aim of this repbn is to describe aquatic hab- well investigated. Howeve! mosquitoes in the tran- itats and associated mosquito larvae and larvivo- sition phase have not been well investigated. An rous predator communities on lands deforested for exception is the record of mosquito fauna and abun- rice field development in Central Sulawesi, eastern dance during the course of the Mahaweli irrigation Indonesia. Such information could be a basis to es- development project in Sri Lanka (Amerasinghe tablish ecologically sound and comprehensive strat- and Ariyasena 1990, 1991). These authors also not- egies for control of mosquitoes and mosquito-borne ed sparsity of aquatic predators (fish and insect diseases in development project areas. predators as a whole, without speciflcation) in open rainwater pools on the recently deforested land. On Indonesia's outer islands, rice field develop- MATERIALS AND METHODS ment projects are being implemented extensively to Study area: The study was conducted in Septem- fill the increasing demand for staple food due to ber 1996 in Toili, Kabupatan Luwuk-Banggai, on human population increases. Many of these projects the eastern peninsula of Central Sulawesi. The set- involve settlement of humans from Java and Bali tlement of this area began in the 1970s' and irri- where malaria has successfully been controlled and gated rice fields already e-xisl around the older vil- people are not immune to malaria. Consequently, lages. However, in the surrounding areas, epidemics of malaria have been reported in the set- deforestation, settlement, and development of new tlement areas including those on Central Sulawesi are still progressing. (Abisudjak and Kotanegara 1989). The occurrence rice fields The area has a slightly seasonal tropical (ca. of filariasis also has been reported in the settlement 1"30'5) climate with a index (100 X number of areas (Partono et al. 1973). As human settlement Q dry months with <60 mm precipitation/number of wet months with >100 mm precipitation) of 14.3- ' Department of Microbiology' Division of Parasitology, 33.3 (Whitten et al. 1988). The mean annual pre- Saga Medical School, Nabeshima 5-1-1, Saga 849-8501' cipitation is 1,500-2,000 mm. The wettest months Japan. are usually June and July but may vary from year 2 Faculty of Public Health, Hasanuddin University' Jl. the wet season was extended and P. Kemerdekaan, Tamalanrea, Ujung Pandang 90245' ln' to year. In 1996, donesia. considerable rains preceded the census. 92 JuNr 1999 MoseumoEs AND PREDAToRCouwuNtttps Il.t INooNsste The study was done at 2 sites where deforesta- tion, which started 3 months before, had almost Moilong W n=668 been completed. Large trees and their roots had Median=1.1m 4 been removed and the lands had been bulldozed. One site, Moilong Atas (Moilong hereafter), was 70 ha of dry land with light and heavy forests be- fore deforestation. The other site, Topo Delapan (Topo hereafter), was I29 laa. Before deforestation, I'o two thirds of Topo was dry with light forests but (J one third was wet with semiaquatic grass, bushes, (2O 6uo and some taller trees. Moilong and Topo are f Topo n=1250 m above sea level, and ca. 15 km apart. o *W o Median=o.6m z Census: The entire area of each study site was ri 20 inspected on foot. The sizes of all pools were re- corded, with approximation to rectangles (length x width) or circles (diameter). Water depths were 10 (10 cm, except for a few large pools in the wet area of Topo. Fifty-five sampling pools were arbitrarily selected y' from sites where presence of mosquito larvae was z' zoz' 2' z' f t t f z' t z" z9 visually conflrmed. Mosquitoes and predators were Poolsize (m )' collected by a dipper, with 1-30 dips per pool, de- Fig. 1. Frequency distributions of pool size on 2 de- pending on pool size. The dip contents from a sin- forested sites (Moilong and Topo), Central Sulawesi, In- gle pool were combined and sieved through a 1OO- donesia.Size was expressedas exponentsof 2. mesh net. Mosquitoes were sorted out in situ. Mosquitoes and the remaining contents were pre- served separately in lOVo formalin solution for later identification under microscopes. This procedure depressions made by the treads of vehicles engaged was adopted to determine the main mosquito spe- in deforestation and leveling. Total areas ofthe sur- cies most efficiently under the limitations of labor face water in Moilong and Topo were 1,934 m2 and and time available for sampling. 15,119 m2, respectively. The surface water occu- Identification' Mosquito larvae and pupae were pied O.3Vo (Moilong) and l.2Vo (Topo) of the total identified to species with keys of Reid (1968) and deforested area. Sirivanakarn (1976, 1977). Other aquatic metzrzo- All pools were fully exposed to sunlight, without ans were identifled to family or higher levels with emergent and floating macrophytes. However, wa- keys of Ueno (1973) and Kawai (1985). ter quality differed between dry and wet areas. In Analysis: Degree of similarity between faunas dry areas, either in Moilong or Topo, the land sur- was examined with Spearman's coefficient of rank face was largely bare due to loss of or inversion of correlation. Differences in frequencies of occur- the surface soil. Consequently, pools there were rence were tested with Fisher's exact probability generally clear except some muddy pools recently test, because frequencies less than 5 are included in disturbed by working vehicles. A few clear pools most taxa. The calculations follow Sokal and Rohlf had submerged clumps of filamentous green algae. n98l). Pools in the wet area (one third of Topo) were generally turbid with rich infusions from tall grass patially buried in the soil at the time of leveling RESULTS or occasionally from grass piled up and left by bull- dozers. This incomplete work apparently Pool conditions was the result of difficulty of manipulating heavy vehicles Most pools were small (Fig. 1). At Topo, more on the wet land. Below, data for pools in the dry than TOVo of pools had areas less than or equal to areas of both Moilong and Topo were combined 1 m', with a peak frequency at the range of 0.5 and compared with those in the wet area of ToDo. (exclusive)-1 (inclusive) m2. A few pools (1Zo) in the wet area were larger than 25O fi:,., with a max- Mosquitoes imum of 4,00O m,. At Moilong, more than i5Vo of pools had areas less than or equal to 2 m2, with a Fourteen mosquito species were collected (Table peak frequency at the range of l-2 m2. The maxi- 1). Specimens belonging to tlnefraudalrlx subgroup mum pool size at Moilong was 50O mr. This pool of subgenus Ittphoceraomyia of the genus Culex was formed by the flooding of a tributary bloiked were not identified to species because of loss ofkey by downed trees that had been thrown into this trib- setae. The same mosquito species occurred in dry utary. This was the only pool exceeding 250 m, in and wet areas, with a few minor exceptions. How- Moilong. Almost all pools less than 2 m2 were in ever, for the order of dominance, no correlation was 94 JounNal op rsr AvenrceN Mosqurro CoNrnol Assocr.lrroN VoL. 15,No.2 Table 1.