NETHERLANDSJOURNALOFAQUATICECOLOGY30(4) 327-330 (1997)
IMPACT OF A DIAZINON CALAMITY IN 1996 ON THE AQUATIC MACROINVERTEBRATESIN THE RIVER MEUSE, THE NETHERLANDS H.G. VAN DER GEEST, S.C. STUiJFZAND, M.H.S. KRAAK and W. ADMIRAAL
KEYWORDS:diazinon, pesticide, River Meuse, ecotoxicology, aquatic invertebrates.
ABSTRACT
A more or less continuous load of pesticides has been noted in the River Meuse in recent years. In April 1996, when high concentrations (up to ca. 1 pg 1-1) of the insecticide diazinon were measured in the River Meuse at the Belgian-Dutch border, the maximum concentration for drinking water production was exceeded. This was alerted after activity changes of fish and daphnids in the biological monitoring systems (RIZA). These observations were compared with literature toxicity data of diazinon, in order to determine the ecological impact of this diazinon discharge on the aquatic macroinvertebrates. LCsovalues of several aquatic macroinvertebrate species were exceeded. In addition, a high mortality was observed in bioassays with the midge Chironomus riparius and the caddisfly Hydropsyche angustipennis. It is inferred that the species composition of the macrofauna community in the River Meuse is likely to be reduced by such an accident. Recolonization of the River Meuse by sensitive macrofauna species may therefore be prevented by incidental pesticide discharges.
POLLUTION OF THE RIVER MEUSE
During the last century, the biodiversity of aquatic macroinvertebrates in the River Meuse in The Netherlands has decreased dramatically. This was caused by deterioration of the water quality due to discharges of industrial and municipal wastewater and/or habitat loss due to the construction of weirs and dams and the regulation of stream bed and river ba~ks. Especially aquatic insects belonging to the orders Ephemeroptera, Diptera, Plecoptera and Trichoptera, which are characteristic for undisturbed river ecosystems (WARD, 1992), are nowadays virtually absent (BU BE vAATE,1995; KETELAARSand FRANTZEN,1995). A growing interest in environmental issues during the last decades resulted in several action programmes for ecological rehabilitation of disturbed ecosystems. The 'Natuurbeleidsplan' (Nature Management Plan; presented by the Dutch government in 1990) and the 'Meuse Treaty' (signed 327
by France, Belgium and The Netherlands in 1994) provide a framework for restoration of natural habitats and water quality improvement in the River Meuse. This raised the expectation that previously extinct, sensitive insect taxa could return to the river. Bioassays with the midge Chironomus riparius and the mussel Dreissena polymorpha showed indeed an improvement of the basic water quality in the River Meuse during the past few years (STU}JF7_AN~3et aL, 1996). However, a persisting load of pesticides has been noted in the River Meuse. The source of this river is in France and it flows through Belgium and The Netherlands into the North Sea. In April 1996, high concentrations of the pesticide diazinon were measured in the water of the river at the Belgian-Dutch border (Eijsden). Diazinon (Fig.l)is a non-systematic organophosphor pesticide used to control a broad variety of leaf eating and sucking insects in agriculture (GIDDINGS, 1996). The maximum concentrations measured in the spring of 1996 (ca. 1 pg 1-1
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on April 14, 0.8 pg 1-1 on April 21 and ca. 1 pg 1-1 on April 28; Institute for Inland Water Management and Waste Water Treatment, RIZA; unpublished data) exceeded the Dutch standard for drinking water quality (RIWA-A limit; 0.02 pg I-1). The actual maximum concentrations of diazinon and the fluctuations in time are unknown, since water samples were not taken continuously, but only at certain time intervals. In biological warning systems at the RIZA monitoring station at Eijsden, a change in activity of the fish Leuciscus idus and the waterflea Oaphnia magna was observed, and consequently an alarm was sent out by RIZA. Despite the high concentrations and the bio-
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Diazinon calamity in the river Meuse logical alert, little attention was paid to this diazinon accident. The aim of this study is, therefore, to determine the ecological impact of this diazinon calamity on the aquatic macroinvertebrate community, that was supposed to recover, in the River Meuse.
TOXIC EFFECTSOF DIAZINON
Toxic effects of diazinon are the result of acetylcholine esterase inhibition by its metabolic product diazoxon. To determine the effects of diazinon on the aquatic macroinvertebrate community in the River Meuse, results of both single and multi species toxicity tests are taken into consideration and discussed below. Fig. 2 gives an overview of the available lethal concentrations (LCso) of diazinon found in literature (AQUNINFO, 1994) plotted against exposure time. A total of 31 different aquatic macroinvertebrate species have been tested. Large differences in sensitivity of different species to diazinon are apparent. The 48h LC5o of diazinon for the most tolerant species, the snail Indoplanorbis exustus, and for the most sensitive species, the midge Chironomus tentans, are respectively 20,000 and 0.1 pg 1-1 (NISHIUCRIand YOSHIOA, 1972; MORGAN, 1976). In general, molluscs and oligochaetes are the taxa least sensitive to this insecticide. However, differences within taxonomic groups make it difficult to classify sensitive and tolerant macrofauna orders. For example, Gammarus pseudolimnaeus is 100 times more sensitive than Gammarus lacustris (MORGAN,1976). The shaded area in Fig. 2 indicates the maximum concentration measured in the River Meuse in 1996. LCso values of Ceriodaphnia dubia, Daphnia magna, Daphnia pulex (ANKLEYet aL, 1991), Gammarus fasciatus (JOHNSONand FINLEY,1980) and Chironomus tentans (MORGAN,1976) were exceeded. In addition, a high mortality was observed in two experiments in which the midge Chironomus riparius and the caddisfly Hydropsyche angustipennis were exposed to Meuse water at the time of the diazinon discharge (STUIJFZANBet al., 1996). Since sublethal effects of diazinon often occur at much lower concentrations than LC5o values (FERNANBEZ-CASALBERRYet al., 1994), it can be expected that sublethal effects of diazinon have occurred in more species than mentioned above. Two studies on community level have been performed. ARTHUR et al. (1983) assessed effects of diazinon on macroinvertebrate communities in
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experimental outdoor channels exposed to different pulsed doses, ranging from 0.3 to 30 pg 1-1. Adverse effects were already observed in the channel with the lowest treatment. Elevated drift and effects on insect emergence were observed in all treated channels, but no effects on species diversity or total macroinvertebrate abundance were found. From these results, the following classification was obtained: flatworms, physid snails, isopods and chironomids were most tolerant; leeches and the amphipod Crangonyx were less tolerant; the amphipod Hyalella, mayflies, caddisflies and damselflies were sensitive. GIDDINGS et al. (1996) conducted a microcosm study, in which lentic aquatic communities were exposed to diazinon. Effects on many zooplankton and macroinvertebrate taxa occurred after 70 days exposure to an average diazinon concentration of 9.2 pg 1-1. Cladocera, Pentaneuri, Ceratopogonidae and Trichoptera were the most sensitive groups and even showed significant effects at the lowest exposure level (nominal 2 pg I-1), with zooplankton being more sensitive than macroinvertebrates and fish. The results of these multispecies toxicity tests are for most taxa not directly comparable with the single species laboratory toxicity tests, caused by differences in test species, exposure time, bioavailability, life stages of the test organisms and, as stated above, differences in sensitivity between taxonomically closely related taxa. For the same reasons, extrapolation of the results of both types of tests to the ecosystem of the river Meuse is speculative.
ECOLOGICAL IMPACT OF THE DIAZINON CALAMITY
Although there are many uncertainties to take into account when determining the ecological impact of the diazinon discharge and no monitoring of natural invertebrate communities was carried out after the accidient, it is most likely that the macrofauna community in the River Meuse was severely damaged. LCso values for several aquatic species were exceeded, a high mortality in bioassays with C. riparius and H. angustipennis occurred and changes in activity in the biological warning systems were observed. It is likely that the ecological impact was even more severe than can be expected from the results of laboratory toxicity tests, since the diazinon peak coincided with low oxygen concentrations. Moreover, the diazinon calamity oc-
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curred in the spring, when many species are present as sensitive first instars (HYNES, 1970). An inventory of the structure of the aquatic invertebrate community in the River Meuse before the accident took place (BU BE VAATE, 1995; KETELAARS and FRANTZEN, 1995) showed a poor community in which opportunistic species dominated, despite the recent recovery of the average water quality. Recovery of such a community after an accident is expected to take place within one generation, as happened after the Sandoz ac-
cident in 1986 in the River Rhine (VAN URK et aL, 1993). Frequent accidental discharges, a poor average water quality and the absence of suitable habitats hamper the rehabilitation of other species that require stable conditions. But even when the basic water quality and the habitats improve as results of action programmes initiated under the Meuse Treaty, accidents like the diazinon discharge in spring 1996 may still prevent the recolonization of sensitive invertebrate species in the River Meuse.
REFERENCES ANKLEY, G.T., J.R. DIERKES,D.A. JENSENand G.S. PETERSON,1991. Piperonyl butoxide as a tool in aquatic toxicological research with organophospbateinsecticides. Ecotoxicol. Environ. Saf. 21: 266-274. AQUNINFO, 1994. A PC-basedacquire lor aquatic toxycity data on chemicals. AScl Corporation. McLean, Virginia. ARTHUR, J.W., J.A. ZISCHKE, K.N. ALLEN and R.O. HERMANUTZ,1983. Effects of diazinon on macroinvertebrateand insect emergencein outdoor experimentalchannels. Aquat. Toxicol. 4: 283-302. BIJ DE VAATE, A., 1995. Macroinvertebrate communities in the Grensmaas Stretch of the River Meuse: 1981-1990. J. Freshwat. Eco[. 10: 75-82. FERNANDEZ-CASALDERRY,A., M.D, FERRANDOand E. ANDREU-MOLINER,1994. Effect of sublethal concentrations of pesticides on the feeding behavior of Daphniamagna.Ecotoxicol. Environ. Saf. 27: 82-89, GIDDINGS, J.M., R.C. BIEVER,M.F. ANNUNZIATOand J. HOSMER, 1996. Effects of diazinon on large outdoor pond microcosms. Environ. Toxicol. Chem. 15: 618-629. HYNES, H.B.N.,1970. The ecology of running waters. Liverpool University Press. Liverpool, UK. JOHNSON, W.W. and M.T, FINLEY, 1980. Handbookof acute toxicity of chemicals to fish and aquatic invertebrates. Resour. Publ. 137, Fish Wildl. Serv., U.S.O.I., Washington, D.C. KETELAARS, H.A.M. and NM.LH.F. FRANTZEN, 1995. One decade of benthic macroinvertebrate biomonitoring in the River Meuse. & Aquat. Toxicol. 29: 121-133. MORGAN, H.G., 1976. Sublethal effects of diazinon on stream invertebrates.Ph.D. Thesis, University of Guelph, Guelph Ontario, Canada. NISHIUCHI, Y and K. YOSHIDA, 1972. Toxicities of pesticidesto some freshwater snails. Bull. Agric. Chem. Insp. Stn. 12: 86-92. STUIJFZAND, S.C., M.H.S. KRAAKand W. ADMIRAAL, 1996. Oecotoxicologischeeffecten van microverontreinigingen op de bodemfaunain de Maas. University of Amsterdam, ARISE, Departmentof Aquatic Ecotoxicotogy,The Netherlands (unpubl. report). VAN URK, G., F. KERKUMand C.J. VAN LEEUWEN, 1993. Insects and insecticides in the Lower Rhine. Wat. Res. 27: 205-213. WARD, J.V., 1992. Aquatic Insect Ecology, 1. Biology and Habitat.John Wiley & Sons, Inc. New York.
Address of the authors:
Department of Aquatic Ecotoxicology,ARISE, University of Amsterdam, Kruisiaan 320, 1098 SM Amsterdam, The Netherlands
