*3.1.1 Drugs effects*

Four 17-β-estradiol concentrations (0.15, 0.31, 0.62, and 1.24 ppm) were tested in an experimental microcosm, and effects on the nematode community from the Ghar el Meleh lagoon were examined after 30 days. Significant differences were

*Marine Free-Living Nematodes as Tools for Environmental Pollution Assessment: A Special Focus… DOI: http://dx.doi.org/10.5772/intechopen.104721*

noted between the control nematode assemblages and those from 17-β-estradiol treatments. Total abundance, Shannon–Wiener index, and evenness were affected by 17-β-estradiol contamination, but species richness was unaffected. The species named; *Chromadorina metulata* and *Ascolaimus elongatus* were eliminated and seemed to be intolerant to estradiol. *Kraspedonema octogoniata* reduced at all doses could be categorized as estradiol sensitive. *Spirinia gerlachi* augmented at all doses seemed to be an opportunistic species [44]. Another experimental study was carried out to determine the effects of endocrine disruptors "Estradiol Benzoate (hereafter EB)" (0.43, 4.3, 8.6, and 12.9 ng l−1) for 30 days. A significant increase in nematode abundances was registered after the EB introduction. In contrast, a decrease in nematodes species diversity has been shown. A clear structural separation of the enriched replicates with EB from controls based on species lists using the nMDS ordination method. A predominance of non-selective deposit feeders and a decline of epistrate feeders were registered [45]. Meiobenthic nematodes were also exposed in experimental microcosms to a drug for COVID-19 treatment "ivermectin" (1.8 ng.g−1, 9 ng. g−1, and 18 ng.g−1) for 10 days. A great reduction in abundance and diversity indices was recorded. The functional types represented by—nonselective deposit feeders and nematodes with circular or indistinct amphids, were affected while these of epistrate feeders and nematodes with rounded or elongated loop amphids, took advantage of ivermectin doses [46].

#### *3.1.2 Polycyclic aromatic hydrocarbons (PAHs) effects*

The effects of two lubricating oils on nematode assemblages were examined. Sediment was treated with mineral oil (Mobil 20 W-50), a synthetic lubricant (Mobil 0 W 40), and the same two lubricants after usage in a vehicle, and effects were examined after 35 days. Total nematode abundance, species richness, and number of species diminished significantly. The evenness was affected only in used mineral lubricant compared to the control. *Daptonema trabeculosum* was removed in all treatments and seemed to be a sensitive species. *Spirinia gerlachi* augmented in mineral lubricant ("clean" and used), was reduced in all synthetic lubricant. *Terschellingia longicaudata* augmented only in synthetic lubricant treatments ("clean" and used) seemed to be a "resistant synthetic-oil species" [47]. A microcosm experiment was carried out to study the effect of diesel on a free-living nematode community. Sediments were polluted by diesel (0.5–20 mg kg−1 dry weight (dw)), and effects were inspected after 90 days. Community structure, diversity, and species richness were modified significantly. The responses of nematode species to the diesel treatments were varied: *Chaetonema* sp. was eliminated and seemed to be intolerant species to diesel contamination; *Pomponema* sp. and *Oncholaimus campylocercois* were significantly affected but they were not eliminated, these species were considered as "dieselsensitive"; *Hypodontolaimus colesi*, *Daptonema trabeculosum*, and *Daptonema fallax* that significantly augmented and appeared to be "opportunistic" species [48].

#### *3.1.3 Metals effects*

The lead and zinc influence, individually and in mixtures on marine nematodes were investigated after 1-month treatment. Results from the multiple comparison tests showed significant differences between nematode assemblages from controls and those from the treated microcosm. The diversity and species richness decreased significantly in the treated microcosms. Multivariate analyses showed that the

differential response occurred in all treatments but the communities from microcosms contaminated with lead and zinc separately were much more strongly affected. *Calomicrolaimus honestus* was eliminated and seemed to be intolerant species, whereas *Oncholaimus campylocercoides* increased significantly at low and medium lead contamination, and at all zinc doses seemed "opportunistic" [49].

The effects of mercury contamination (low, 0.084 ppm; medium, 0.167 ppm; and high, 0.334 ppm) on a free-living nematode community were examined after 60 days. The majority of univariate indices decreased significantly with increasing levels of mercury. The responses of nematode species were varied: *Araeolaimus bioculatus* was eliminated at all mercury doses; *Marylynnia stekhoveni* augmented at low and medium treatments was performed to be an "opportunistic species," whereas *Prochromadorella neapolitana*, which amplified at all concentrations, seemed to be a "mercury-resistant species" [50].

Nematodes were subjected to cobalt and/or zinc enrichment in a microcosm experiment for 30 days. Nematode abundance, diversity, and taxonomic structure were significantly altered. Using multivariate analyses, the data showed that nematodes assemblages from treated microcosms with zinc alone were much more negatively affected compared with those exposed to cobalt alone. The nematode species' responses to the cobalt and zinc treatments were different. *Oncholaimellus mediterraneus*, *Oncholaimus campylocercoides*, and *Neochromadora trichophora* were significantly affected by cobalt contamination. *Hypodontolaimus colesi* was eliminated and seemed to be an intolerant species versus zinc [51].

The ecotoxicity of a chromium-enriched superfood, *Spirulina platensis*, on the nematodes was investigated after 1 month of exposure. The abundance, taxonomic structure, and the nematode's functional diversity showed significant changes between the *Spirulina* and *Spirulina* + chromium groups. The lowest taxonomic


#### **Table 1.**

*Ghar ElMelh lagoon nematodes response to ECs. NS (not studied).*

*Marine Free-Living Nematodes as Tools for Environmental Pollution Assessment: A Special Focus… DOI: http://dx.doi.org/10.5772/intechopen.104721*

and morpho-functional diversity were observed in the highest concentration of *S. platensis* (50% DW). The nematode species' responses differed depending on their functional traits. *Spirulina* supplemented with chromium induced high toxicity for nematodes species, whereas, the *Spirulina*/chromium combinations toxicity was lower suggesting mutual neutralization between these two components [52].

### *3.1.4 Pesticides effects*

The nematode response to permethrin contamination [P1: low (5 mg kg−1), P2: medium (25 mg kg−1), and P3: high (250 mg kg−1)] was examined in a microcosm experiment and the effects were evaluated after 30 days. The univariate and multivariate analyses showed significant variances between nematode assemblages from control assemblage and those from permethrin treatments. Total nematode abundance (I), Shannon-Weaner index (H'), species richness (d), evenness (J'), and number of species (S) reduced significantly. The nematode community responses were varied: *Oncholaimus campylocercoides, Theristus pertenuis, Araeolaimus bioculatus,* and *Calomicrolaimus honestus* amplified in all doses, appeared to be "permethrin-resistant species." *Daptonema trabeculosum* was eliminated and appeared "permethrin-sensitive species" (**Table 1**) [53].
