Ecotoxicidade de herbicidas para a macrófita aquática (Azolla caroliniana)

Abstract

RESUMO -Os objetivos deste estudo foram avaliar Azolla caroliniana como planta-teste em estudos ecotoxicológicos e estimar a CL50;7d dos herbicidas 2,4-D, glyphosate, clomazone e oxyfluorfen. As plantas foram aclimatadas em sala de bioensaio. Para isso, foram selecionadas cinco plantas em 50 mL de meio de cultivo Hoagland. Palavras-chave: bioindicador, toxicidade aguda, produtos fitossanitários, macrófita.ABSTRACT -The objectives of this study were to evaluate Azolla caroliniana as test plant in ecotoxicological studies and to estimate the LC50; 7d of the herbicides 2,4 D , glyphosate, and clomazone oxyfluorfen. The plants were acclimatized in the bioassay room. Five plants in 50 mL Hoagland culture medium were selected. After that, 50 mL of Hoagland and the herbicide were added, completing the volume to 100 mL. The 50% lethal concentration (LC50; 7d) for A. caroliniana exposed to the herbicide 2,4-D, was 708.35 mg L -1 ; to glyphosate (formulation Scout ® ), 23.66 mg L -1 ; to glyphosate (formulation Trop ® ), 38.91 mg L -1 ; to clomazone, 129.63 mg L -1 ; and to oxyflourfen, 80.50 mg L -1 . The herbicides glyphosate (Scout ® and Trop ® ) and oxyflourfen were classified as moderately toxic to A. caroliniana, while clomazone and 2,4-D were classified as practically nontoxic. It was concluded that A. caroliniana plants can be used as bio-indicators for glyphosate and oxyfluorfen-based herbicides.

Macrophyte Bioassay Applications for Monitoring Pesticides in the Aquatic Environment

“…For A. caroliniana, the mortality used was according to the grade scale (E and A) (SILVA et al, 2012). The mortality results were subjected to linear regression, and the lethal concentration of 50% (CL50;7d) was estimated by the Trimmed Spermam Karber software (Hamilton et al, 1977).…”

“…For A. caroliniana, the lethal concentration (CL50;7d) of atrazine, clomazone and bentazon+imazamox and of the alphacypermetrin + teflubenzuron insecticide was higher than 100.0 mg L (Silva et al, 2012), which shows the low sensitivity of this bioindicator; the correlation between concentration and mortality is shown on Table 1. Azolla filiculoide exposed to the mixture of herbicides atrazine, isoproturon and alachlor (50+35+15%) showed CE50;21d of 60.0 µg L -1 (Coutris et al, 2011), and for Azolla pinnata exposed at 0.001 and 0.002 mg L (Cruz et al, 2015), which indicates a higher sensitivity of A. caroliniana to these herbicides than to the ones tested on this study using the same plant (A. caroliniana).…”

“…Another macrophyte that may be used as a bioindicator is Azolla caroliniana, due to its easy management, short cycle of life, short height and since it is a cosmopolitan species; however, it still requires studies on its sensitivity as a bioindicator. This macrophyte has been used for the evaluation of pesticides glyphosate, clomazone, oxyfluorfen and 2.4-D (Silva et al, 2012), in addition to imazapyr (Cruz et al, 2015).…”

Imazapyr herbicide efficacy on floating macrophyte control and ecotoxicology for non-target organisms

“…L. minor was evaluated accordingly to changes in growth rate and fronds number (OECD, 2002). On A. caroliniana was used a grading scale (E to A) accordingly to Silva et al (2012). The acute toxicity (LC50; 7d) was calculated by Trimmed Spearman-Karber software (Hamilton et al, 1977).…”

<b>Sensitivity of aquatic organisms to ethanol and its potential use as bioindicators

“…The aquatic macrophyte L. minor, from the Lemnaceae family, is standardized for toxicity tests and is used by several authors (OECD, 2002;Coutries, Merlina, Silvestre, Pinelli, & Elger, 2011;Kielak, Sempruch, Mioduszewska, Klocek, & Leszczynski, 2011); the A. caroliniana is endemic to the tropical America, belongs to the Azollaceae family and can be used in toxicity tests (Guimarães, Aguiar, Oliveira, Silva, & Karam, 2012;Silva, Cruz, Neto, & Pitelli, 2012).…”