and habitation” [28]. This capacity is achieved by an exquisite interplay between
inherent physicochemical and biological properties and processes, which are originally defined during soil formation or pedogenesis [29]. Many exogenous factors
such as land use, agrochemical inputs, global warming and introduction of exotic
species, among others, alter soil quality with the risk of causing its degradation
(i.e. the loss of actual or potential productivity or utility of soil as a result of natural
and anthropogenic factors [30]). Current knowledge on soil biology indicates that
biodiversity is a pivotal property in soil quality [31–33], and conventional agriculture (defined as the agricultural practices that use synthetic pesticides and fertilisers
in short rotation crops [34]) seriously threats it [35]. Therefore, promotion and
maintenance of soil biodiversity is determinant to boost sustainable agriculture that
ensures reasonably high crop yields and food security.
Earthworms are annelids belonging to soil macrofauna (i.e. organisms of >2 mm
in size [36]) and exert a profound impact on soil quality. In general, these organisms
alter soil microbial and mesofauna (0.1–2 mm, body size [36]) communities with
indirect effects on nutrient cycling and soil biodiversity [37]. The continuous
burrowing and feeding activities of earthworms create a complex network of permanent (anecic species) and temporary (endogeic species) galleries [38], which have
led these organisms to be considered as “soil engineers” [39]. In fact, earthworms
have a significant contribution in soil bioturbation, i.e. “the biological reworking of
soils and sediments by all kinds of organisms, including microbes, rooting plants,
and burrowing animals” [40], whereby they largely affect microbial population
dynamics [41] and facilitate microorganism dispersion in soil [42]. These functional
capacities have led earthworms to have a particular interest in agronomy and
environmental sciences because of their beneficial effects on plant growth and
development [43, 44], control of soil-borne pathogens [45, 46], indirect degradation
of organic pollutants [47] and buffering effect in polluted soils [48]. However, the
agronomic and ecological benefits depend on feeding habits of earthworms. Soil
ecologists classify earthworms into three categories according to preferred soil
habitats, feeding habits and morphological traits [36, 49–51]: epigeic, anecic and
endogeic (Table 1).
Epigeic earthworms are small-medium sized, inhabit soil surface and feeding on
decomposing organic residues accumulated on the soil surface (Fig. 2). Epigeic
earthworms rarely burrow into the soil and ingest it, so they are little or no exposed to
organic pollutants occurring in the mineral soil. Some species of this ecological
group such as Eisenia fetida, E. andrei or Lumbricus rubellus are used in the
composting of municipal and industrial organic wastes (vermicomposting)
[52]. Anecic earthworms are large sized and create long, permanent vertical burrows
and feeding on decomposing litter that collect from the soil surface and drag into the
burrow or accumulate at the entrance of the burrow, forming a deposit of litter mixed
with cast named “midden” [53]. They also ingest mineral soil to obtain particulate
organic matter [49]. The middens are considered hotspots of organic matter decomposition and faunal diversity [54, 55].
Endogeic species are medium sized soil-dwellers and ingest large amounts of soil
to obtain nutrients. Earthworms of this ecological group intensively built temporary
Vermiremediation of Pharmaceutical-Contaminated Soils and Organic Amendments
343
inherent physicochemical and biological properties and processes, which are originally defined during soil formation or pedogenesis [29]. Many exogenous factors
such as land use, agrochemical inputs, global warming and introduction of exotic
species, among others, alter soil quality with the risk of causing its degradation
(i.e. the loss of actual or potential productivity or utility of soil as a result of natural
and anthropogenic factors [30]). Current knowledge on soil biology indicates that
biodiversity is a pivotal property in soil quality [31–33], and conventional agriculture (defined as the agricultural practices that use synthetic pesticides and fertilisers
in short rotation crops [34]) seriously threats it [35]. Therefore, promotion and
maintenance of soil biodiversity is determinant to boost sustainable agriculture that
ensures reasonably high crop yields and food security.
Earthworms are annelids belonging to soil macrofauna (i.e. organisms of >2 mm
in size [36]) and exert a profound impact on soil quality. In general, these organisms
alter soil microbial and mesofauna (0.1–2 mm, body size [36]) communities with
indirect effects on nutrient cycling and soil biodiversity [37]. The continuous
burrowing and feeding activities of earthworms create a complex network of permanent (anecic species) and temporary (endogeic species) galleries [38], which have
led these organisms to be considered as “soil engineers” [39]. In fact, earthworms
have a significant contribution in soil bioturbation, i.e. “the biological reworking of
soils and sediments by all kinds of organisms, including microbes, rooting plants,
and burrowing animals” [40], whereby they largely affect microbial population
dynamics [41] and facilitate microorganism dispersion in soil [42]. These functional
capacities have led earthworms to have a particular interest in agronomy and
environmental sciences because of their beneficial effects on plant growth and
development [43, 44], control of soil-borne pathogens [45, 46], indirect degradation
of organic pollutants [47] and buffering effect in polluted soils [48]. However, the
agronomic and ecological benefits depend on feeding habits of earthworms. Soil
ecologists classify earthworms into three categories according to preferred soil
habitats, feeding habits and morphological traits [36, 49–51]: epigeic, anecic and
endogeic (Table 1).
Epigeic earthworms are small-medium sized, inhabit soil surface and feeding on
decomposing organic residues accumulated on the soil surface (Fig. 2). Epigeic
earthworms rarely burrow into the soil and ingest it, so they are little or no exposed to
organic pollutants occurring in the mineral soil. Some species of this ecological
group such as Eisenia fetida, E. andrei or Lumbricus rubellus are used in the
composting of municipal and industrial organic wastes (vermicomposting)
[52]. Anecic earthworms are large sized and create long, permanent vertical burrows
and feeding on decomposing litter that collect from the soil surface and drag into the
burrow or accumulate at the entrance of the burrow, forming a deposit of litter mixed
with cast named “midden” [53]. They also ingest mineral soil to obtain particulate
organic matter [49]. The middens are considered hotspots of organic matter decomposition and faunal diversity [54, 55].
Endogeic species are medium sized soil-dwellers and ingest large amounts of soil
to obtain nutrients. Earthworms of this ecological group intensively built temporary
Vermiremediation of Pharmaceutical-Contaminated Soils and Organic Amendments
343