Detect coastal disturbances and climate change effects in coralligenous community through sentinel stations

monitoring, management, and conservation of coastal zones and their associated marine pro- tected areas. Historically, methodological difficulties related to the monitoring and study of subtidal communities have led to their neglect in many environmental monitoring programs [3], par- ticularly in relation to rocky habitats because of their wide heterogeneities, the fixed nature of the resident sessile organisms, the frequent difficulty of achieving access, and the fact that the sampling must be undertaken through indirect methods from boats. Warwick [4] indicated that the study of these communities on wide spatial scales involves a series of technical and implementation difficulties that are not present for work on soft bottoms, the water column, or the intertidal zone. For these reasons, studies related to the environmental monitoring, sur- veillance, and impacts of various factors on the sublittoral benthic environment have focused on endofauna (macroinvertebrates) associated with soft substrates [5–12]. Many biotic indices based on these animals have been proposed [13–15], and many of these indices have been used for or adapted to the requirements of the European Community Water Framework Directive [16–18]. Indeed, regarding monitoring methods based on indicators in the scope of the European Community Directives [19–20], the research has centred on macroalgae on hard substrates [21–28] and seagrasses [29–32], whereas macroinvertebrates associated with high-diversity rocky subtidal habitats (which have greater abundances of sensitive indicator species) have

been less well studied. However, some studies have sought to establish the ecological statuses of coralligenous assemblages [33–39]. The environmental information that can be provided by these assemblages is very powerful and reliable [40–43]; therefore, this faunal approach to rocky habitats could help to fill an important knowledge gap within the European Community Directives [19–20]. Of particular importance is the information that can be provided by pre-coralligenous and coralligenous rocky bottoms because of their high biodiversities and the abundances of sensi- tive colonial species with long life cycles. Although there are some long-term studies of species that are representative of coralligenous communities [44–49] short- and medium-term studies are more common [50,51]. In contrast, growing concern about the effects of climate change has led to more studies of epibenthic (rocky bottom) species in relation to coral bleaching [52–54], seagrass meadows [55], invasive alien species [56,57], and even the role of the marine reserve biota in climate change monitoring [58–60]. These studies have also highlighted the severe environmental impacts on benthic organisms that have arisen from abnormal temperature increase events in the western Mediterranean [61–63]. The great fragility of highly structured and mature benthic communities associated with hard substrates, such as those of pre-coralligenous and coralligenous areas, has encouraged non-invasive study methods based on video footage or photos of species that are fixed to the

substrate in random quadrats [36,51,64–75]. However, the absence of long-term series that have empirically validated these methodologies as systems for detecting changes in communi- ties has been limiting. Additionally, previous studies have focused on characterising and/or monitoring benthic communities, which implies greater complexity with respect to implementation mainly due to the high diversity of species present in these enclaves, which, in turn, entails greater effort and difficulty associated with the identification of the taxa. However, the Sessile Bioindicators in Permanent Quadrats (SBPQ) methodology, which was proposed by one of the authors of the present paper [43], differs from other methodologies, mainly in that the quadrats are perma- nently fixed to the rocky bottom and that the coverage of a previously selected target species must be at least 10% within each quadrat. Fixed quadrats allow changes in the coverage of PLOS ONE Detect coastal disturbances in coralligenous PLOS ONE | https://doi.org/10.1371/journal.pone.0231641 May 5, 2020 2 / 23 Funding: This research supported by the Regional Activity Centre for Special Protected Areas (RAC/ SPA) and the Mediterranean Protected Areas Network (MedPAN) projects, Consejerı´a de Medio Ambiente de la Junta de Andalucı´a, and co- financed by Autoridad Portuaria de Sevilla, Compañı´a Española de Petro´leos S.A.U. (CEPSA) Foundation and Red Ele´ctrica de España (REE). Also, research was partially supported by the University of Seville providing salaries to the authors JCG-G and, FE, and Research Foundation

of University of Seville (different projects) providing salaries to ARG and MJM. The specific roles of these authors are articulated in the ‘author contributions’ section. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: This study was partly supported by Autoridad Portuaria de Sevilla, Compañı´a Española de Petro´leos S.A.U. (CEPSA) Foundation and Red Ele´ctrica de España (REE). There are no patents, products in development or marketed products to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials.