Functional Stability of Microbial Communities in Contaminated Soils Near a Zinc Smelter (Budel, The Netherlands)

Abstract

Abstract. Environmental pollution causes adverse effects on many levels of ecosystem organization; it might affect the use efficiency of available resources which will make the system more sensitive to subsequent stress. Alternatively the development of community tolerance may make the system more resistant to additional stresses.In this study we investigate the functional stability, measured in the terms of resistance and resilience, of microbial populations inhabiting contaminated soils near a zinc smelter. With functional stability we mean that we look at processes rather than at population dynamics. We measure changes in respiration and bacterial growth rate in response to addition of stress (lead, salt) or disturbance (heat). We used soils that differ in the level of pollution with zinc and cadmium originating from an adjacent smelter.Our results showed, with regard to respiration, that the most polluted soils have the lowest stability to salt (stress) and heat (disturbance). This confirms the hypothesis that more stressed systems have less energy to cope with additional stress or disturbance.However, bacterial growth rates were affected in a different way than respiration. There was no difference between the soils in resistance and resilience to addition of lead. In case of salt treatment, the least polluted soils showed highest stability. In contrast, the least polluted soils were the least stable to increased temperature, which supports the hypothesis that more stressed soils are more stable to additional stress/ disturbance due to properties they gained when exposed to the first stress (pollution by the smelter).Thus, the responses of microbial processes to stress, their nature and size, depend on the kinds of stress factors, especially whether a subsequent stress is similar to the first stress, in terms of the mechanism with which the organisms deal with the stress.

Copper pollution decreases the resistance of soil microbial community to subsequent dry–rewetting disturbance

“…As for the red soil, the resistance of SIR in the high copper-stressed soils was also significantly lower than that in the zero and medium copper-stressed soils. This result was in line with previous studies, that previously stressed soils were more affected by a subsequent disturbance than unstressed soils (Tobor-Kaplon et al, 2006). We speculated that organisms in the metal-contaminated soils might allocate more energy to detoxification and damage repair; therefore, it was harder for stressed soils to cope with additional disturbance (Kuperman and Carreiro, 1997).…”

“…There has been some debate about the impacts of initial stress on the soil microorganisms in response to subsequent stress (Tobor-Kaplon et al, 2006;Li et al, 2014). In this study, our results demonstrated that the SIR in the copper-stressed soils (medium and high) were less resistant to subsequent DW disturbance than in the non-copper-stressed soil (zero) in the fluvo-aquic soil.…”

Soil nematode responses to heavy metal stress

“…All extracted nematodes in each sample were counted and identified to genus level using an inverted compound microscope. The classification of trophic groups was assigned to: (1) bacterivores; (2) fungivores; (3) plant-parasites; and (4) omnivores-predators, based on known feeding habitats or stoma and esophageal morphology (Yeates et al, 1993;Renčo, 2004;Hua et al, 2006;Liu et al, 2006;Meng et al, 2006;Liang et al, 2007). Four ecological indices of nematode communities were calculated: (1) nematode taxon richness (S), S is the total number of genera ; (2) Maturity index (MI25), MI25 = Σv(i)·f(i), where v(i) is the c -p value of taxon i (excluding c-p 1 group), f (i) is the frequency of taxon i in a sample (Bongers, 1990;Korthals et al, 1996;Nagy et al, 2004).…”

Initial Copper Stress Strengthens the Resistance of Soil Microorganisms to a Subsequent Copper Stress

“…The influence of initial stress on resistance and resilience of soil microbial community to a subsequent stress was less studied and is still being debated [18]. Compared with the uncontaminated soils, soil microorganisms in the heavy metal-contaminated soils were more affected by a subsequent heat or salt stress due to the less energy of stressed system to cope with additional stress [19]. However, ammonia oxidizers in long-term zinc-contaminated soil were less sensitive to a secondary zinc stress than that in the uncontaminated soil because of the zinc tolerance of longterm zinc-contaminated soil [20].…”