Positive effects of two decades of passive ecological restoration in a historically polluted marine site

Abstract

The Mediterranean Sea is one of the most exploited regions of the world’s oceans. Here industrial activities have determined either acute or long-term impacts on coastal marine ecosystems. In this study, we investigated macrofauna distribution and diversity, and food-web functioning in a coastal area of the Mediterranean Sea facing an industrial chemical plant abandoned in the ‘90s to assess benthic ecosystem health. This area has been identified as a Site of National Interest (SNI) since 2002 and has been closed to any human activity awaiting to be remediated according to national laws. Our results indicate that, two decades after the SNI declaration (a decade after the plant decommissioning), there is no longer any sign of the impact of historical contaminations on macrofauna and benthic food web functioning. Overall, all the thirty-six sites showed high/good ecological quality according to the score assigned by AMBI and M-AMBI indexes, reflecting the absence of chronic impacts. Our findings reveal, for the first time, the positive effects of passive restoration (i.e., unassisted, or spontaneous recovery following cessation of anthropogenic impacts) on historically impacted coastal ecosystems since their health conditions, in terms of both abiotic (environmental variables and contaminant concentration) and biotic (macrofauna diversity and community composition, and benthic food-web structure) factors, were indistinguishable from surrounding non-impacted areas. These findings also suggest that other effective area-based conservation measures (OECMs) could be useful not only for biodiversity conservation of vulnerable and priority habitats in larger ocean sectors but also to promote the passive recovery of historically contaminated ecosystems.

Combining passive and active restoration to rehabilitate a historically polluted marine site

“…Being interdicted to human activities for decades due to historical pollution and presenting nowadays characteristics indistinguishable from the surrounding non-interdicted areas, this SNI represents an optimal candidate as restoration site to TABLE 1 Output of PERMANOVA analyses testing for the effect of factors Site and Time on meiofaunal abundance, taxonomic and rare taxa composition (A), macrofaunal abundance and taxonomic composition (B), and the effect of time on the algal heights during the grazing experiment (ns = not significant, * = p < 0.05; *** = p < 0.001). implement combined passive and active restoration interventions (Corinaldesi et al, 2022;Fanelli et al, Coastal infrastructures, such as breakwater barriers, ports, and offshore installations, are an ideal harsh substrate for the conservation of threatened marine species and can represent suitable substrates for "active restoration" interventions (Perkol-Finkel et al, 2012). In this regard, very few attempts were carried out in the Northern Adriatic Sea, where breakwater barriers represent a hard substrate different from the surrounding sandy habitats, using G. barbata on coastal defence structures, with encouraging results (Perkol-Finkel et al, 2012).…”

“…Previous investigations in marine ecosystems suggested that to reduce and reverse biodiversity loss, the "passive" restoration (e.g., obtained through the institution of marine protected areas, MPAs) should be complemented by "active" restoration (e.g., transplants, translocations; van Tatenhove et al, 2021). However, also "Other Effective Area-based Conservation Measures" (OECMs: locally managed no-take areas, fishing restricted areas, ecological corridors, and trawling bans established through long-term management plans; Diz et al, 2018) or areas interdicted to human activities for decades due to historical pollution can be optimal candidates as restoration sites, particularly those that no longer present signals of environmental damage and have characteristics indistinguishable from the surrounding noninterdicted areas (Corinaldesi et al, 2022;Fanelli et al, 2023).…”

“…Meio-and macrobenthic communities are characterized by high structural and trophic-functional diversity and have key roles in benthic food webs and in maintaining their functionality, thus providing information on the ecosystem' health status (Bianchelli and Danovaro, 2020;Fanelli et al, 2023). Therefore, their abundance, biomass, and diversity can be investigated in restoration interventions of different macroalgae species and used as indicators of success (Semprucci et al, 2013;Bianchelli et al, 2016a;Bianchelli et al, 2016b;Corinaldesi et al, 2022;Bianchelli et al, submitted).…”

“…The SNI is a historically polluted and degraded environment, enclosed among the "problem areas" of the European seas (Andersen et al, 2022). The interdiction of the marine area to any human use for about 20 years has been reported to have positive effects on the benthic ecosystems, which currently show no sign of alteration (Corinaldesi et al, 2022;Fanelli et al, 2023). Therefore, this area putatively represents an optimal site for restoration.…”

Challenges in Restoring Mediterranean Seagrass Ecosystems in the Anthropocene

“…The global challenge of seagrass loss over the past century raises significant concerns, reflecting issues such as poor water quality, increased sedimentation and nutrient runoff due to coastal development, direct habitat destruction, physical damages from illegal fishing practices, and the impacts of climate change, including thermal anomalies and a rising sea level [2,3]. The Mediterranean Sea stands out as one of the most exploited regions in the world's oceans [4]. Meadows of the endemic seagrass Posidonia oceanica, which holds paramount importance in the Mediterranean, have experienced a substantial decline over the last century, with more than half of their original extent lost [5].…”