The key role of canyons in funnelling litter to the deep sea: A study of the Gioia Canyon (Southern Tyrrhenian Sea)

Abundance and Composition of Marine Litter on the Seafloor of the Gulf of Sant Jordi (Western Mediterranean Sea)

“…As expected, plastic material was the most common item removed from the seafloor in the Gulf of Sant Jordi (close to four of every five items). The predominance of plastic items concurs with results found in other Mediterranean areas [4,[37][38][39]44,48,49,53,57,62,64,65], but also in other waters including the Atlantic Ocean [49,66,67], the Black Sea [62,68], the North Sea [42,69], the Baltic Sea [42,43], and the Caribbean Sea [32].…”

“…We have no information about the abundance of marine litter in the shallowest waters close to the coast where the amount of marine litter tends to decline, as reported by Fortibuoni et al [44] and Mutlu et al [57]. Moreover, the hauls in the Gulf of Sant Jordi did not include deep canyons, where the amounts of marine litter tend to be higher than on the continental shelf [27,37].…”

“…In contrast, higher values than ours have been reported in the Eastern Mediterranean Sea by Stefatos et al [48] in the Gulf of Patras (240 items km −2 ), Ioakeimidis et al [62] in the Gulf of Saronikos (1211 items km −2 ), Cau et al [39] in the Tyrrhenian Sea (258 items km −2 ), Crocetta et al [53] in the Gulf of Naples (300 items km −2 ), Enrichetti et al [34] in the Ligurian Sea (maximum densities of 7900 items ha −1 ), Pierdomenico et al [37] in the Southern Tyrrhenian Sea (up to 56.3 items/100 m), and by Fortibuoni et al [44] in the southern area of the Gulf of Venice (983 items km −2 ), North Corfu (910 items km −2 ), and the Kerkiraikos Gulf (829 items km −2 ). These higher values are, in some cases, because of high population density including seasonal arrivals, or because the study area is located near the mouth of a river and/or aquaculture fishing activities.…”

“…Determining the abundance, spatial distribution and composition of marine litter requires its removal from beaches and seas or recording it using video or photography from autonomous underwater vehicles (AUVs), human-occupied vehicles (HOVs), towed underwater cameras (TUCs), or remotely operated vehicles (ROVs) [29]. Some of the most recent studies using ROVs include those by Consoli et al [30,31], Botero et al [32], Costanzo et al [33], Dominguez-Carrió et al [27], Enrichetti et al [34], Garofalo et al [35], Mecho et al [36], and Pierdomenico et al [37].…”

“…The concentration of marine litter depends on a number of factors including distance from the coastal area, population density of the coastal area, coastal physiography, presence of rivers, sea depth, and oceanographic conditions such as sea currents and topographic characteristics of the seafloor [29,46,[58][59][60]. Deep canyons, sometimes far from the coast, have been found to represent important sinks for marine litter [27,37]. The association of topographic (bathymetric profile and slope) and hydrodynamic components (surface and bottom currents) is also a pivotal factor that influences the dispersion or accumulation of marine macro-litter [61].…”