Baseline study of the distribution of marine debris on soft-bottom habitats associated with trawling grounds in the northern Mediterranean

Abstract

SUMMARY: The present study aims to analyse the local and regional variability in the density and typology of marine debris on fishing grounds on the northern Mediterranean continental shelf, and to test relationships between marine litter and trawl fishing activity. Moreover, the colonization of plastics was examined in order to study the importance of plastics as a source of impact on marine communities and their further environmental implications. This study surveyed 11 sites, associated with trawling grounds and subjected to different levels of fishing intensity, located in four areas of the Mediterranean: one in Italy, the Central Tyrrhenian coast, one in Greece, the eastern Ionian coast, and two in Spain, the Murcian and Catalan coasts. Samples were collected during an oceanographic cruise undertaken from the 21 May to the 24 June 2009. Results showed geographical variation in the density of marine debris which ranged from 0 to 405 pieces per hectare in the surveyed areas, plastics being the dominant components. Variability within sites was higher than between areas, indicating small-scale patchiness in the distribution of the debris over the seafloor. Though the study areas were within trawling grounds, the density of debris was not significantly correlated with fishing effort. More than 30% of plastics were between 10 and 20 cm width/ length, and more than 40% of the plastics were colonized by a biofilm of microorganisms, suggesting indirect effects on benthic communities.Keywords: marine debris, seabed plastic accumulation, colonized benthic plastics, northern Mediterranean Sea. RESUMEN: Estudio dE rEfErEncia sobrE la distribución dE basura marina En fondos blandos asociados a caladEros dE pEsca dE arrastrE En El mEditErránEo nortE. -Este estudio tiene como objetivo analizar la variabilidad local y regional de la basura marina en caladeros de pescas de la plataforma continental mediterránea septentrional y estudiar la relación entre ésta y la actividad pesquera. En este estudio se examinaron once estaciones de muestreo asociadas a caladeros de pesca, sujetas a distintos niveles de esfuerzo y situadas en 4 áreas en el Mediterráneo: una en Italia, en la costa central del Tirreno (TC), otra en Grecia, en la costa jónica occidental (IC) y otras dos en España, en las costas murciana y catalana (MC y CC). Las muestras se obtuvieron durante una campaña oceanográfica llevada a cabo entre el 21 de mayo y el 24 de junio de 2009. Los resultados mostraron una variación geográfica en la densidad de basura marina comprendida entre 0 y 405 piezas por hectárea en las áreas muestreadas, siendo los plásticos el componente principal. La variabilidad entre estaciones resultó más alta que la variabilidad entre áreas, lo que indica una heterogeneidad a pequeña escala en la distribución de la basura sobre el fondo. Aunque las áreas de estudio estaban situadas en caladeros pesqueros, la densidad de basura no mostró una correlación significativa con el esfuerzo de pesca. Más del 40% de los plásticos se encontraron colonizados po...

Microfouling communities from pelagic and benthic marine plastic debris sampled across Mediterranean coastal waters

“…The process of colonization causes density changes in MPD, which, in combination with the effect of currents, may cause their sinking to the seabed. Once on the seabed, the process of colonization continues (Fortuño et al 2010, Demestre and Masó 2012, Sánchez et al 2013. Not only macroplastics but also microplastics are subject to microfouling (Reisser et al, 2014).…”

“…In each study area, 18 dredge samples were randomly collected performing a 15-minute tow at 2.5 kn following the sampling strategy used in epibenthic studies (de Juan et al 2011). In a previous analysis conducted on these samples, Sánchez et al (2013) showed that only 8% of collected plastics showed no sign of colonization, while the rest were covered by fouling organisms. A subset of 16 benthic plastics, in the first phase of succession of colonization, was selected to be analysed.…”

“…1), where plastics were sampled during the COMSOM experimental cruise (Sánchez et al 2013). Results from the previous work by Sánchez et al (2013) showed high densities of plastics in each area surveyed (i.e.…”

“…Benthic MPD provides a new colonization substrate for organisms, so MPD has the potential to change the structure of benthic communities and benthic biodiversity in general (Katsanevakis et al 2007, Sánchez et al 2013. Floating MPD also provides new habitats, but especially it offers a long-lasting material that can substantially raise the dispersion capacity of organisms (Aliani and Moldcard 2003, Thiel and Gutow 2005, Barnes et al 2009).…”

“…1), where plastics were sampled during the COMSOM experimental cruise (Sánchez et al 2013). Results from the previous work by Sánchez et al (2013) showed high densities of plastics in each area surveyed (i.e. 60 pd/ha on the Catalan coast, northwestern Mediterranean, 59.5 pd/ha on the Central Tyrrhenian coast, 34 pd/ha on the Murcia coast, southern Spanish Mediterranean, and 23 pd/ha on the eastern Ionian coast), representing higher values than those recorded in other areas of the Mediterranean, such as the Adriatic Sea, the Gulf of Lions and eastern Corsica (Galgani et al 2000).…”