Influence of heavy metals on nematode community structure in deteriorated soil by gold mining activities in Sibutad, southern Philippines

Abstract

Ore mining is among the most environmentally destructive anthropogenic practices, particularly in developing countries. Correct assessment of its impacts on soil ecosystems requires an understanding of the response of soil food webs. Nematodes, often the most abundant invertebrates in soils, occupy various positions in food webs, and their assemblages are commonly used to reflect soil health. In October 2014, we collected soil samples from five sites of a small-scale mining area in Sibutad, southern Philippines, to assess the influence of mining activities on nematode assemblages. Two sites were considered undisturbed as there were no visible signs of mining, while the other three sites were disturbed. Nematodes were extracted live and identified to genus level using morphology-based identification. We analysed genus composition, genus and trophic diversity, and the life-history based maturity index. We measured soil environmental variables (pH, organic matter, granulometry and several heavy metals), and correlated variation in nematode genus composition to variation in these environmental factors. Small-scale mining activities had variable but generally nonsignificant impacts on soil properties, altered vegetation and caused increases in concentrations of Hg and Pb, but not consistently so in all impacted sites. The high patchiness in vegetation and heavy metal content were reflected in a high within-site variability of nematode assemblages. Total nematode abundance was significantly lower in two mainly physically disturbed sites, but not so in the most metal-polluted one, suggesting that abundance is not a good indicator of pollution status. Nematode genus composition significantly differed between disturbed and undisturbed sites. By contrast, only few differences between sites were found for diversity or maturity indices, demonstrating that genus composition was a better indicator of mining-related effects than many common indicator indices and highlighting that detailed assemblage analysis is required for a correct interpretation of moderate pollution effects on soil 2 nematodes. Measured environmental variables together explained 60% of the variation in nematode assemblages in the area; the three 'single best' explanatory variables were the concentrations of Pb, Hg and N, but none of these by itself explained more than 8% of the variation in nematode data, while their combination explained 24%. Some genera of predacious and omnivorous nematodes, which are generally expected to be sensitive to both chemical pollution and physical disturbance (e.g., Ironus and Eudorylaimus), were most abundant in sites with elevated heavy metal concentrations, which can have repercussions for the interpretation of nematode-based indices such as the MI.

The Influence of Illegal Gold Mining (IGM) on Environmental, Economic, and Educational Sectors of Muara Mensao Village, Jambi

“…This result was in convinient with previous study that the Batang Limun River has been experiencing physical and Whilst, the highest concentration of mercury was 153 ppb [5]. The heavy metal content was very dangerous for living things [28,29].…”

Species coexistence of marine nematodes

“…In contrast with nematode species composition, structural diversity (species richness, Shannon diversity and evenness) of both assemblages was not significantly affected by temperature or time. Hence, biodiversity indices did not reflect the changes in assemblage composition, in accordance with other recent studies on meiofauna and/or nematodes (Meadows et al, 2015;Martinez et al, 2018). However, it is possible that the incubation period was too short to translate observed shifts in species composition to measurable changes in diversity.…”

Short-term effects of cadmium and mercury on soil nematode communities in a pot experiment

“…Soil nematode as an indicator for heavy metal pollution has been widely studied in recent years. (Zhang et al, 2011;Šalamún, 2011;Martinez et al, 2018). Most of previous studies took place in an open environment such as mining area, however, under laboratory condition, the characteristics of rhizosphere nematode communities affected by specific concentrations of single and mixed heavy metals are not well studied.…”