The Responses of Plankton Communities in Experimental Ponds to Atrazine, the Most Heavily Used Pesticide in the United States

Abstract

Abstract. Experimental ponds received single additions of the herbicide atrazine in concentrations of 20 and 500 gg/L, and were compared to control ponds for 136 d. Atrazine is an inhibitor of photosynthesis, and both concentrations depressed phytoplankton growth in the ponds within a few days. This was followed by successional changes leading to the establishment of species of phytoplankton more resistant to inhibition by atrazine. Laboratory studies verified this resistance and verified effects on other species at concentrations of atrazine as low as 1-5 Jig/L. When and to what extent resistant species appeared in the phytoplankton communities differed with treatment. At the atrazine concentration of 500 gg/L, there was a delayed appearance but eventually a greater biomass and persistence of these species. The grazing zooplankton influenced these differences and were in turn affected by them. Natural interactions such as competition and predation among the species of the communities greatly affected their responses to the toxic chemical. The importance of atrazine as an environmental pollutant is suggested by these responses to concentrations of 1-5 gg/L, which are common downstream in many agricultural watersheds, 20 /Ig/L, which is the high level found in these waters, and 500 gg/L, which is the high level found in waters directly adjacent to treated fields.

Atrazine induction of a family 4 cytochrome P450 gene in Chironomus tentans (Diptera: Chironomidae)

“…It is one of the most extensively used herbicides in North America, and has been detected in both surface water and groundwater (Gruessner and Watzin, 1996). Studies of its occurrence and behavior in streams and rivers draining agricultural lands have shown that the highest atrazine concentrations usually occur in relatively brief pulses following rain events, especially those that occur soon after herbicide application (DeNoyelles et al, 1982). However, significant effects of atrazine at ecologically relevant concentrations have been reported to cause hermaphroditism and demasculinization in male frogs exposed to 0.1 and 1.0 μg/l of atrazine (Hayes et al, 2002).…”

Comparative Sensitivity of Freshwater Algae to Atrazine

“…A number of laboratory, microcosm and fi eld studies have examined atrazine toxicity in freshwater algae (DeNoyelles et al 1982;Herman et al 1986;Solomon et al 1996;Tang et al 1997;Fairchild et al 1998). From these studies, it is generally recognized that certain algal species are more sensitive to atrazine (DeNoyelles et al 1982;Tang et al 1997;Fairchild et al 1998).…”

“…From these studies, it is generally recognized that certain algal species are more sensitive to atrazine (DeNoyelles et al 1982;Tang et al 1997;Fairchild et al 1998). Green algae generally are more susceptible to atrazine than diatoms (Tang et al 1997).…”

Les herbicides inhibateurs du photosystème II, effets sur les communautés algales et leur dynamique

“…(1995) en étangs expérimentaux, constatent une baisse des concentrations en oxygène dissous, révélatrice de l'inhibition de la photosynthèse par l'herbicide, à des concentrations supérieures à 22 \ig/L. DE NOYELLES et al (1982) en étangs expérimentaux, mettent en évidence des déstructurations spécifiques de communautés phytoplanctoniques contaminées par 20ug/L, et constatent significativement des augmentations de fluorescence maximale induite sur des échantillons de ces communautés mis en présence de 1 |o.g/L. NYSTRÔM (1997) en microcosmes, met en évidence des déstructurations spécifiques de communautés périphytoniques contaminées par 12 ng/L.…”

“…Dans le cadre d'études portant sur la sensibilité d'une seule espèce à un herbicide, les auteurs observent une diminution du taux de croissance des algues : STRATTON (1984) Mais dans certains cas la présence d'herbicides entraîne une augmentation de la biomasse algale globale : DE NOYELLES et al (1982) après 15 jours de culture avec 500 ug/L d'atrazine ; LAMPERT étal. (1989) après une douzaine de jours dans des enceintes contaminées par 0,1 ug/L d'atrazine (cette augmentation de la concentration en pigments est par ailleurs associée à une augmentation de la production primaire) ; PELTE (1995) avec 10 ug/L d'atrazine ; PRATT et al (1988) avec 3,2-10 ug/L d'atrazine ; BRYFOGLE et MCDIFFETT (1979) après 30 jours avec 400 ug/L de simazine ; SHEHATA et al (1993) avec 10 ug/L de gardoprim.…”