**Abstract**

Metal pollutants are widespread in air, soil and water causing a decline in invertebrates worldwide. The increase of environmental pollution by heavy metals has a negative impact to organisms and influence their diversity, distribution, physiology and behavior. Contrary to other pollutants, metals are non-degradable and can potentially bioaccumulate and be biomagnified in the trophic chain. Because soil invertebrates tend to be strongly affected by environmental disturbances, high concentrations of these metals can become hazardous to invertebrates. Noxious effects can affect all biological levels, and toxins affect all ecological interactions. In this brief chapter, we have tried to develop a comprehensive understanding of the influence of metal contamination on ecosystem disturbance. We give examples of studies on the effects of pollutants on invertebrates.

**Keywords:** impact, heavy metals, invertebrate decline, environmental pollution, bioindicators

### **1. Introduction**

Pollution is a mixture of contaminants in the environment that has serious consequences on the environment. It can originate from chemicals in any environmental medium, with deleterious consequences on living species. The damage expressed to living organisms can lead to damage to their health or interference with the ecological systems of which they are a part [1]. However, the ecological risk of heavy metals has become a major concern in developing countries. The multiple industrial, domestic, agricultural, medical and technological applications of heavy metals have led to their wide distribution in the environment, raising increasing concerns about their potential effects on human health and the balance of ecosystems. Heavy metals are also part of the contaminants that can be found in residential areas. Heavy metals present in the atmosphere, soil and water today come from various sources such as landfills, domestic and industrial waste, mineral and oil extraction sites as well as atmospheric pollution. These products are accumulated by the fauna and flora and magnified along the food chain, which multiplies the impact of this pollution. Each year the levels of pollutants, in particular metals, increase and cause environmental threats that lead to the imbalance of the natural system [2]. Toxic chemicals in the environment can enter ecosystems and end up throughout the biosphere. Ecosystems can be affected by chemical contamination, disturbing the activities of living organisms or changing the physical properties of ecosystems [3].

Disturbed environments and excessively loaded with metals, can lead to a decrease in the biological activity of invertebrates. Currently the regression of the diversity of invertebrates in the world is very remarkable. According to [4], the effects of toxic metal pollution on terrestrial invertebrate species appear to be extremely significant and widespread. Such a revision of regulatory thresholds to better protect terrestrial invertebrates, which seem more sensitive to metal pollution than vertebrates, is necessary and needs urgent attention from scientists and stakeholders [5]. The pollution of ecosystems exposes an astonishing danger to invertebrate's species through direct and/or indirect contact with contaminated soil [6, 7]. The contamination of ecosystems is the complication that strongly affects biodiversity, the environment and human health all over the world via soil and water pollution [8]. Bioindicators have been considered an essential tool for monitoring and discovering changes in the environment [9]. The choice of the most adequate indicator is linked to the objective of the survey and the characteristics of the indicator. In the invertebrate group, several species or groups of species have been used as indicators. Bioindicators species are sensitive to environmental changes, such as high levels of metals [10, 11], this sensitivity is expressed by the absence or presence of species, or by altered physiological and/or morphological changes [12]. The relationships between toxic chemical elements, the biotope and living organisms can cause the degradation of these compounds during their modification, leading to transformations of the environment and leading to harmful damage to living organisms [3]. The response of invertebrates to metal pollution is closely related to species as well as pH conditions, exposure time, and metal form and concentration, which are deeply tied to metal bioavailability [13, 14]. It should be noted that the use of certain species of invertebrates as better indicators than others is linked to their different ecological requirements. As part of biomonitoring programs, measurements of metal residues have been established on invertebrate species [15]. The utility of studies performed on invertebrates can be essential for such an assessment of the impact of toxic metal pollution on environmental behavior and the strategies adopted to anticipate such an effect [10]. They show an important role in terrestrial environments linked to their vast abundance, biomass, and diversity [16]. Invertebrates living in polluted environments have been regularly revealed to accumulate heavy metals [17–19]. Using sensitive species invertebrates lets for an improved valuation of the threats environmental and for more informative and efficient test systems [10].
