Influence of pesticides and herbicides presence on phosphatase activity and selected bacterial microbiota of a natural lake system

Abstract

Phosphatase activities (cell-bounded phosphatases ''BP'' and freely dissolved phosphatases ''DP'') in water samples from a natural lake ''Laguna Grande'' (Antequera, Má laga, Spain) amended with 50 lg/ml of selected insecticides, herbicides and fungicide captan were studied under laboratory controlled conditions (temperature and agitation). Our data show that dissolved alkaline phosphatase was the enzymatic activity that contributed in higher proportion to total lake water samples phosphatase status. The presence of organochlorinated insecticides (aldrin and lindane), organophosphorous insecticides (dimetoate, methidation and methyl-parathion), herbicide atrazine and fungicide captan significantly increased phosphatase activities after 28 days of incubation. However, these activities were not affected as a consequence of the addition of the herbicide simazine to the water samples. Heterotrophic mesophilic and psychrophilic aquatic bacteria counts as well as culturable phosphate solubilizing microorganisms, increased when the pesticides were added to lake water samples with herbicide simazine exception.

A synthesis of the effects of pesticides on microbial persistence in aquatic ecosystems

“…In mesocosms designed to simulate a tidal creek, chlorpyrifos applied at 10 µg L −1 increased heterotrophic bacterial abundance, while decreasing heterotrophic ciliate and flagellate (protozoan) abundance (DeLorenzo, Scott, and Ross, 1999). Similarly, parathion at 50 000 µg L −1 tended to increase abundance of heterotrophic bacteria in water samples collected from a natural lake (Lopez et al, 2006). However, another study revealed no significant effects of the pesticide on natural protozoan, bacterial, or fungal species in microcosms, even when concentrations exceeded water quality criteria three-fold (~12 000 µg L −1 ) (Pratt, Bowers, and Balczon, 1993).…”

“…In another study of community level effects, endosulfan (at 1 µg L −1 ) increased phototrophic carbon assimilation, although diatom, dinoflagellate, algal species were significantly reduced (Downing et al, 2004). Aldin and lindane, at concentrations of 50 000 µg L −1 , resulted in increased heterotrophic bacterial abundance in samples taken from a natural lake (Lopez et al, 2006). In samples isolated from a tropical estuary system, bacterial abundance was reduced by endosulfan, DDT, and lindane at concentrations ranging from 2 to 2000 µg L −1 , with bacteria in the water column experiencing greater detrimental effects than those in the sediment (Rajendran, Rajendran, and Venugopalan, 1990).…”

“…In water samples collected from a natural lake, an increase in heterotrophic bacterial abundance with an atrazine concentration of 50 000 µg L −1 was observed (Lopez et al, 2006). Similarly, Hamala and Kolliq (1985) found that a concentration of 100 µg L −1 increased heterotrophic activity (Hamala and Kolliq, 1985).…”

“…However, in a study by Downing, DeLorenzo et al ., 20 µg L −1 of chlorothalonil was found to stimulate heterotrophic bacterial activity, increase diatoms and chlorophytes, and reduce golden algae and heterotrophic protozoa (Downing et al, 2004). Similarly, captan, applied at 50 000 µg L −1 , increased heterotrophic bacterial abundance in a lake ecosystem (Lopez et al, 2006). In freshwater microcosms, 170 µg L −1 chlorothalonil reduced autochthonous protozoan densities as effectively as cycloheximide (a known inhibitor of protein synthesis in eukaryotes), providing an indirect positive effect on bacterial densities (Staley et al, 2014).…”

“…In many cases, a direct negative effect on a target species has been found to be offset at the community level, suggesting that indirect effects have a strong influence on the net effect (direct + indirect effects) of a pesticide. However, despite the importance of indirect effects, few studies have examined indirect and/or net effects of pesticides at the community level (DeLorenzo et al, 1999; DeLorenzo, Scott, and Ross, 1999; Downing et al, 2008; Downing et al, 2004; Lopez et al, 2006; Staley, Rohr, and Harwood, 2010; Staley, Rohr, and Harwood, 2011; Staley et al, 2014). Nevertheless, the handful of studies that have examined the effects of pesticides on microbial communities suggest that there is trophic downgrading, a pattern that seems to be occurring globally as a result of various stressors(Estes et al, 2011).…”