DRIFT OF AQUATIC INSECTS FOLLOWING METHOXYCHLOR TREATMENT OF THE SASKATCHEWAN RIVER SYSTEM

Abstract Drift of aquatic insects was compared at three sites downstream (21, 38, and 107 km) from methoxychlor treatment (0.3 mg. L−1 for 15 min) of the North Saskatchewan River, relative to an upstream untreated site. Species of Diptera (Simuliidae), Ephemeroptera (Baetidae, Heptageniidae, Ephemerellidae, Ametropodidae, Metretopodidae, and Tricorythidae), Plecoptera (Perlodidae and Chloroperlidae), Trichoptera (Hydropsychidae and Hydroptilidae), and Hemiptera (Corixidae) were studied. Drift responses differed depending on species, distance from the injection site, and time after methoxychlor injection. Exposure to methoxychlor initiated catastrophic drift of aquatic insects at all downstream sites. Of 22 species compared before treatment and following methoxychlor injection, post-treatment drift of 17, 21, and 13 species significantly exceeded pre-treatment drift at the km 21, 38, and 107 sites, respectively. Methoxychlor treatment initiated or increased drift of several normally non-drifting species. Similar drift patterns were observed among closely related taxa during the catastrophic phase. For all species studied, comparisons of 24-h drift densities between days preceding and following the catastrophic phase of treatment indicated significant post-treatment drift density increases or decreases at one or more of the downstream sites, but not at the untreated site. Species were classified according to their drift responses to methoxychlor treatment. Factors that may have caused different drift responses among species are discussed. Résumé On a comparé la dérive d’insectes aquatiques à trois sites en aval du site d’application (21, 38 et 107 km) d’un traitement au methoxychlor (0,3 mg. L−1 pendant 15 min) dans la rivière North Saskatchewan, à celle d’un site témoin situé en amont. On a étudié des espèces de Diptera (Simuliidae), d’Ephemeroptera (Baetidae, Heptageniidae, Ephemerellidae, Ametropodidae, Metretopodidae et Tricorythidae), de Plecoptera (Perlodidae et Chloroperlidae), de Trichoptera (Hydropsychidae et Hydroptilidae) et d’Hemiptera (Corixidae). La dérive a varié dépendant de l’espèce, de la distance par rapport au site traité et du temps après le traitement. Le traitement au méthoxychlor a provoqué une dérive catastrophique des insectes aquatiques à tous les sites situés en aval. Parmi 22 espèces suivies avant et après le traitement, la dérive post-traitement excédait la dérive pré-traitement pour 17, 21 et 13 espèces, aux km 21, 38 et 107, respectivement. Le traitement a déclenché ou augmenté la dérive de plusieurs espèces qui, normalement, ne dérivent que peu ou pas. Dans patrons de dérive similaires ont été observés chez des taxons étroitement apparentés durant la phase catastrophique. Pour toutes les espèces étudiées, la comparaison de la densité de dérive pendant 24 h entre des jours précédant et suivant la phase catastrophique a indiqué une augmentation ou une diminution significative de la densité de dérive à un ou plusieurs des sites situés en aval, mais pas au site témoin. Les espèces ont pu être classifiées selon leur réaction de dérive au traitement. On discute des facteurs pouvant expliquer la réaction différentielle de dérive des espèces.

[1]  D. M. Rosenberg,et al.  Impact of Methoxychlor on Selected Nontarget Organisms in a Riffle of the Souris River, Manitoba , 1989 .

[2]  L. Dosdall,et al.  The impact of methoxychlor treatment of the saskatchewan river system on artificial substrate populations of aquatic insects. , 1989, Environmental pollution.

[3]  E. Russek,et al.  The Quantification of Stream Drift , 1985 .

[4]  J. Webster,et al.  Pesticide Manipulation of a Headwater Stream: Invertebrate Responses and Their Significance for Ecosystem Processes , 1984, Freshwater Invertebrate Biology.

[5]  J. Culp,et al.  Macroinvertebrate Subsampling: A Simplified Apparatus and Approach , 1982 .

[6]  Richard L. Anderson,et al.  Toxicity and bioaccumulation of endrin and methoxychlor in aquatic invertebrates and fish , 1980 .

[7]  D. Barton,et al.  OBSERVATIONS ON THE BIOLOGY OF AMETROPUS NEAVEI (EPHEMEROPTERA: AMETROPODIDAE) FROM A LARGE RIVER IN NORTHERN ALBERTA, CANADA , 1979, The Canadian Entomologist.

[8]  B. E. Townsend,et al.  THE EFFECTS OF AN EXPERIMENTAL INJECTION OF METHOXYCHLOR ON AQUATIC INVERTEBRATES: ACCUMULATION, STANDING CROP, AND DRIFT , 1979, The Canadian Entomologist.

[9]  W. F. Merritt,et al.  Laboratory and field experiments with methoxychlor as a larvicide for simuliidae (diptera) , 1976 .

[10]  F. J. Fredeen.  EFFECTS OF A SINGLE INJECTION OF METHOXYCHLOR BLACK-FLY LARVICIDE ON INSECT LARVAE IN A 161-KM (100-MILE) SECTION OF THE NORTH SASKATCHEWAN RIVER , 1975, The Canadian Entomologist.

[11]  H. Hynes,et al.  The catastrophic drift of stream insects after treatments with methoxychlor (1,1,1-trichloro-2,2-bis(p-methoxyphenyl) ethane) , 1975 .

[12]  W. F. Merritt,et al.  Dispersion and transport of Rhodamine B dye and methoxychlor in running water: A preliminary study , 1973 .

[13]  T. F. Waters.  The Drift of Stream Insects , 1972 .

[14]  R. C. Muirhead-Thomson,et al.  Pesticides and Freshwater Fauna. , 1972 .

[15]  F. J. Fredeen.  A NEW PROCEDURE ALLOWING REPLICATED MINIATURE LARVICIDE TESTS IN A LARGE RIVER , 1969, The Canadian Entomologist.

[16]  H. Sanders,et al.  The relative toxicities of several pesticides to naiads of three species of stoneflies , 1968 .

[17]  J. Dimond.  Evidence that Drift of Stream Benthos is Density Related. , 1967, Ecology.

[18]  Thomas F. Waters,et al.  Interpretation of Invertebrate Drift in Streams , 1965 .

[19]  B. Berck,et al.  Further Experiments With DDT in the Control of Simulium Arcticum Mall. In the North and South Saskatchewan Rivers1 , 1953 .