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

target species and the rest of the benthic community to be detected without the need for a high number of replicates, and with the certainty that these differences are not due to the character- istic spatial heterogeneity of this kind of habitat. The simplicity and relatively low cost of the method allows the monitoring of the stations to be repeated in the short term, which is essen- tial in the detection of invasive species or other anthropogenic disturbances that require rapid action. The method is not intended to assess the biodiversity or ecological status of these com- munities, but to establish an early warning system that allows the detection of changes in the coverage of target species. Based on the detection of these changes, specific studies can be designed to assess the degree and origin of the disturbance. Objectives This study aims to assess the underwater environmental SBPQ alert method, which focuses on monitoring preselected sessile and sensitive benthic species associated with rocky coralligen- ous habitats using permanent quadrats in underwater sentinel stations. The selected target spe- cies have been well documented as bioindicators that disappear in the absence of environmental stability via acute impacts. However, it has not been verified if these species are good indicators of long-term stability. The purpose of the present study was to assess the por- tion of the method based on the hypothesis that, over a long temporal series (a ten-year period in this study) in a highly structured and biodiverse coralligenous assemblage, the cover of sen-

sitive sessile species (i.e., the target species) does not change over time if the environmental sta- bility of the habitat is not altered. Materials and methods Study zone This study was performed on the benthic community of two sentry stations on a rocky bottom. The station is situated within the Strait of Gibraltar Natural Park (southern Spain) inside the Grade A protection zone (i.e., the maximum protection area within the Natural Park) charac- terized by rocky bottoms with a moderate slope that host a high biodiversity and species rich- ness, dominated by species such as Eunicella sp., Paramunicea clavata, Astroides calycularis, Pentapora sp., Crambe crambe and Salmacina sp. in the Punta Carnero locality (Algeciras), but it is proximal to zones under strong anthropic pressure (Fig 1). Despite its enormous ecological wealth and high level of protection, the SBPQ sentry station is at notable risk of anthropogenic disturbance. This is due to both to its proximity to the par- ticularly industrialised Bay of Algeciras, where many different pollution sources can be found (thermal power plant, chemical industry, petrochemicals, bunkering activities, etc.) [76,77] and the high level of marine traffic through the area. Due to the second factor, the last decade has seen polluting events related to hydrocarbon spills of varying magnitudes including serious spills from the ships Sierra Nava and New Flame, both of which occurred in 2007 [78]. Data regarding the bottom water temperature in the study area were obtained from data

base of the regional environmental authorities [79]. The implementation of the study was noti- fied to the managers of the the Strait of Gibraltar Natural Park and to the competent environ- mental authority of Andalusia Government (Regional Ministry of Environment and Territory Planning, CMAYOT). In fact, the CMAYOT has funded the publication of the spanish verison book where the methodology SBPQ is included (43). In adition the first author of the current study is part of the governing board of the Strait of Gibraltar Natural Park. No permits were required for this work. PLOS ONE Detect coastal disturbances in coralligenous PLOS ONE | https://doi.org/10.1371/journal.pone.0231641 May 5, 2020 3 / 23