Combined effects of food concentration and the herbicide 2,4-dichlorophenoxyacetic acid on the population dynamics of Brachionus patulus (Rotifera).
Herbicides are important in crop protection and management. A number of them including 2,4-D (2,4-dichlorophenoxyacetic acid), however, may reach water bodies and eventually affect the non-target organisms such as rotifers. In the present work, we studied the influence of 6 concentrations viz. 0 (control), 100, 200, 300, 400 and 500 mg l-1 of 2,4-D on the population growth of the rotifer Brachionus patulus under two algal (Chlorella) food levels (0.5 x 10(6) and 1.5 x 10(6) cells ml-1). Regardless of herbicide concentration, the population growth of B. patulus was dependent on the algal food levels, in that an increase in algal food level supported a better population growth. Similarly at any Chlorella density, the herbicide had a negative influence on the population growth of B. patulus. Herbicide level of 500 mg l-1 inhibited population growth of B. patulus beyond 5 days. Rotifers grown under low food density and high herbicide concentration (300 mg l-1 or above) were completely eliminated after day 15. The rate of population increase (r) (mean +/- standard error) in the controls varied from 0.46 +/- 0.002 and 0.55 +/- 0.004 under 0.5 x 10(6) and 1.5 x 10(6) cells ml-1 of Chlorella, respectively. The r values became negative under both, low and high food levels, at or beyond 300 mg l-1 of 2,4-D. The maximal population abundance (ind. ml-1) in controls varied from 294 +/- 9 to 503 +/- 21 under low and high food levels of Chlorella, respectively. The role of algae in mitigating adverse effects of high herbicide concentrations to rotifers has been discussed.
Division of Biology, National Autonomous University of Mexico, Campus Iztacala, AP 314, CP 54090, Tlalnepantla, State of Mexico, Mexico. sarma@servidor.unam.mx
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Ramírez-Pérez
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Nandini
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Peñalosa-Castro
D015084:2,4-Dichlorophenoxyacetic Acid / Q000009:adverse effects*; D000818:Animals; D004032:Diet; D004305:Dose-Response Relationship, Drug; D005508:Food Deprivation; D006540:Herbicides / Q000009:adverse effects*; D011157:Population Dynamics; D012403:Rotifera; D014874:Water Pollutants, Chemical / Q000009:adverse effects*
D006540:Herbicides; D014874:Water Pollutants, Chemical; D015084:2,4-Dichlorophenoxyacetic Acid