Environmental+Toxicology+Tox+2000+notes (2)

Similarly the zooplankton dependent on these primary

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Unformatted text preview: appear to respond to a t oxicant that is selective for phytop lankton. INDIRECT DIRECT Effects may be a decrease in numbers or an increase in numbers + + - - A TEMPORAL DIFFERENCES BETWEEN PRIMARY AND SECONDARY EFFECTS + - - Mortality (effect) + Concentration B CONCENTRATION-RESPONSE USING EFFECTS AT A CERTAIN TIME OR AREA UNDER THE CURVE Figure 3-221 Use of temporal response (A) and functional data (area under the curve) (B) for interpretation of primary and secondary effect dose-responses In the final analysis, i t is a question of defining what is meant by a significant change in an ecosystem. When is the system so different from the norm (if this itself can indeed be defined) that regulatory or preventative measures need be taken? 3.2.9 Classification of effects in microcosms Responses in microcosms can be categorized in a number of ways. Effect classes for responses in microcosms have been proposed (Brock et al. 2006). In Europe, these effect classes (Table 32) are used to evaluate semi -field tests submitted for the registration of pesticides. Table 30. Classes of effects observed in microcosm studies Class 1 Effect Effect could not be demonstrated (NOEC micro/mes ocosm) 2 Slight effect Description No (statistically significant) effects observed as result of the treatment, and observed differences between treatment and controls show no clear causal relationship. Causality in this context is judged throu gh the use of guidelines similar to those developed for identifying causative agents of disease (Koch 1942, Hill 1965, IPCS 2002) . Effects reported in terms of ―slight‖ or ―transient‖ and/or other similar descriptions. Short-term and/or quantitatively restricted response of sensitive Table 30. Classes of effects observed in microcosm studies Class 3 4 5 3.3 Effect Description endpoints. Effects only observed at individual sample times. Pronounced Clear response of sensitive endpoints, but full recovery of short-term affected endpoints within 8 weeks after the 1st (effect class 3A) effect (A or B) or last (effect class 3B) application (from recovery in treated test systems). Effects reported as ―temporary effects on several sensitive species‖, ―temporary elimination of sensitive species‖, ―temporary effects on less sensitive species/endpoints‖ and/or other similar descriptions. Effects observed at some subsequent sampling instances Pronounced Clear effects (such as large reductions in populations of effect in short - sensitive species) observed, but the study is too short to term study demonstrate complete recovery within 8 weeks after the (last) application. Pronounced Clear response of sensitive endpoints and recovery time longer long-term than 8 weeks after the last a pplication, but full recovery is effect (A or B) demonstrated to occur in the year of application (effect class 5A) or cannot be demonstrated before termination of the experiment or before the start of the winter period (effect class 5B). Effects reported as ‗‗long -term effects followed by recovery on several sensitive and less sensitive species/endpoints‘‘ o...
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