Ants and their nests as indicators for industrial heavy metal contamination

Pollutants and Their Interaction with Diseases of Social Hymenoptera

“…Among the pollutants, pesticides used in agriculture have gained the most attention because pollinators visit crop plants or wild flowers growing near arable fields and are confronted with those chemicals when collecting food ( Figure 1) [59][60][61][62]. Heavy metals are a second group of pollutants that may threaten social insects in agricultural regions, but also in more urbanized or industrial areas [31,35,[63][64][65][66][67][68][69][70][71]. Heavy metals are present in soils (either naturally or due to pollution) and can potentially lead to contamination of the nests of social insects, or they may move up the food chain ( Figure 2).…”

“…Plants may take up heavy metals which, in turn, are ingested by social bees collecting pollen and nectar. Also, other herbivorous insects serving as prey for social wasps may accumulate these pollutants, which may result in the increased exposure of these predatory wasps to heavy metals [35,36,47,63,65,[68][69][70][71][72][73][74][75][76][77][78][79][80]. Pesticides (or their residues) and heavy metals, as well as other pollutants from combustion, traffic, agriculture, and coal mining, can also form or bind to fine particulate matter [66,[81][82][83][84][85][86][87][88][89][90][91] that pollutes the air.…”

“…In comparison to pesticide effects, the health effects of heavy metals have received much less attention (Figure 2). Of the existing studies, many have established that heavy metals are often present in the nest matrices in ants and the wax combs or honey in bees in polluted areas [31,35,63,65,67,[69][70][71]75,78,102,[121][122][123][124][125][126][127][128][129][130]. While many social Hymenoptera may be confronted with heavy metal pollution in strongly human-influenced environments, relatively little data exists on the potential detrimental health effects in comparison to pesticide effects.…”

“…The accumulation of heavy metals during foraging has been documented along pollution gradients. Pollution levels in pollen stores of bees were positively correlated with heavy metal pollution as well as the heavy metal content in the bodies of bees [46,71], ant workers or nest material [35,133], and wasps [36,80]. Correlative studies have shown that with increasing heavy metal pollution, the mortality of solitary [46,47] as well as social bees [64,210] increased, and that body size [35] and colony size decreased in ants [133].…”

“…However, these subtle individual-level effects may be amplified over time, resulting in long-term negative effects on colony fitness [19,29,30]. For example, pollutants incorporated into stored foods or nest materials, including beeswax, may accumulate over time [31][32][33][34][35][36][37][38][39][40], leading to a constant exposure to pollutants of larva and adults of new generations of workers, as well as sexuals [37,41,42]. In this way, even subtle effects on individuals can have quite extreme negative consequences for social insect colonies, threatening their existence [21,29,30,43].…”