Common sea urchin (Paracentrotus lividus) and sea cucumber of the genus Holothuria as bioindicators of pollution in the study of chemical contaminants in aquatic media. A revision

•Many pollutants enter the seas and oceans as a result of anthropogenic activities.•Chemical compounds cause serious damage to marine and terrestrial ecosystems.•Contaminants accumulate in the environment once their useful cycle has ended.•The presence and harmful effects they cause to the marine biota are investigated.•Holothuria spp. and Paracentrotus lividus are proposed as bioindicators. Currently many pollutants enter the seas and oceans as a result of anthropogenic activities such as agriculture, fishing, shipping, etc. Many of these chemical compounds cause serious damage to marine and terrestrial ecosystems because they tend to accumulate and begin their activity as pollutants once their useful cycle has ended. Therefore, there is growing concern about how to act to stop the increase in environmental pollution. Some of these compounds that began to accumulate in the environment since the last century are well known by the scientific community and are widely called persistent pollutants. This group includes polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and heavy metals, among others. However, other compounds that have not been considered as contaminants have appeared recently. These are the so-called emerging pollutants, which involve a long list of compounds including drugs, hormones, antimicrobials, plasticizers, UV filters, etc. Through the study of different organisms, the presence of these pollutants in natural environments as well as the harmful effects they cause to the biota present in said media are being deeply investigated. Two of the aquatic model organisms used as bioindicators in the different studies for this purpose are reviewed here: the sea cucumber of the genus Holothuria and the common sea urchin Paracentrotus lividus that share the fact of being, both, edible echinoderms. This review could be used to make people aware of the damage it is causing through the irresponsible management of natural resources, so that they serve to launch a series of measures that allow recovering the original conditions of the different ecosystems.