Multiple environmental descriptors to assess ecological status of sensitive habitats in the area affected by the Costa Concordia shipwreck (Giglio Island, Italy)

Abstract

The aim of the study was to evaluate the effectiveness of the application of multiple environmental descriptors through an asymmetrical sampling design to detect possible impacts related to the Costa Concordia event on the coastal marine environment. The Costa Concordia shipwreck occurred on a submerged rocky reef in the north-western Mediterranean Sea and the wreck was removed 2 years later. To achieve the proposed objective two main coastal ecosystems, the seagrass Posidonia oceanica and coralligenous assemblages were studied using two ecological indices, PREI and ESCA, respectively. Both indices show a lower ecological quality in the disturbed sites compared with the control ones. Differences between the disturbed and control sites observed in both studied ecosystems would seem to indicate an increase of turbidity around the shipwreck as the most plausible cause of impact. The concurrent use of different ecological indices and asymmetrical sampling designs allowed detection of differences in ecological quality of the disturbed sites compared with the controls. This approach may represent an interesting tool to be employed in impact evaluation studies.

STAR: An integrated and standardized procedure to evaluate the ecological status of coralligenous reefs

“…The level of human pressure was defined following the method proposed by Piazzi, Bianchi, et al () and Piazzi, Gennaro, et al (), which considered proximity to commercial harbours and/or urbanized areas, levels of eutrophication and sedimentation rates, and mechanical disturbance by fishing activities. In the former group, two sites were located near Livorno harbour (Livorno‐1, Livorno‐2), three near Civitavecchia harbour (Sant'Agostino, Civitavecchia, Santa Marinella) and one on the east side of Giglio Island, close to the harbour and the Costa Concordia shipwreck (Casoli et al, ; Penna et al, ). Three sites with low human pressure were chosen in the Tuscan Archipelago National Park (Elba Island North, Elba Island East, Giglio Island North), two in the Capo Carbonara Marine Protected Area (Capo Carbonara–Cavoli, Capo Carbonara–Serpentara) and one in the Tavolara–Capo Coda Cavallo Marine Protected Area.…”

Impact assessment of fish cages on coralligenous reefs through the use of the STAR sampling procedure

“…The STAR procedure can be a profitable solution for obtaining the data needed to calculate different ecological indices in a single sampling effort. Overall, although each descriptor is reliable to different human impacts (Gatti et al, 2015a;Montefalcone et al, 2017;Penna et al, 2017;Piazzi et al, 2018a), the challenge to identify early signals of stress and effects due to low-magnitude disturbance would be the most useful goal of conservation efforts. In this context, the fact that the three indices did not give homogeneous responses to moderate disturbances emphasises the need for a multi-descriptor approach to evaluate human pressure on natural systems, as already investigated for other marine systems (Borja et al, 2009a(Borja et al, , 2009bMartinez-Crego et al, 2010;Bedini & Piazzi, 2012).…”

“…The effects of the presence of a fish farm on coralligenous reefs were evaluated using the STAR sampling procedure. An asymmetrical sampling design (ACI, After-Control/Impact, Underwood 1997), similar to Chapman et al (1995), Guidetti et al (2002), and Penna et al (2017), was used to compare the aquaculture site with two reference sites in areas unaffected by human pressure. The hypothesis was that at the disturbed site the structure of the assemblage would change, with a decrease in abundance of sensitive taxa and an increase of opportunistic taxa, as compared to the undisturbed sites.…”

“…Evidently, mechanisms of impact cannot be highlighted without appropriate manipulative experiments and thus any speculative insights about them have been purposefully avoided. Aiming to identify the best tool to use in fish farm impact evaluation on coralligenous reefs, results obtained by different ecological indices and descriptors (Gatti et al, 2015a;Piazzi et al, 2016Piazzi et al, , 2017b2018a;Penna et al, 2017) were compared.…”

High spatial resolution photo mosaicking for the monitoring of coralligenous reefs

“…All the pictures used in this study were acquired along the northern vertical wall of the Gabbianara ridge, between 19 and 25 m depth, where thick coralligenous reefs are present (50 m long 9 15 m height approximately). The bioconstruction was impacted by the presence of the wreck and its salvaging operations that caused fine sediment dispersion and the partial loss of benthic organisms (Casoli et al 2017(Casoli et al , 2020Penna et al 2018). We decided to test here this new sampling technique in virtue of applying in future to assess the recolonization and the resilience processes on the aforementioned coralligenous reefs.…”