Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea

[摘要] Deep-sea ecosystems are in general adapted to a limited variability ofphysical conditions, resulting in high vulnerability and slow recovery ratesfrom anthropogenic perturbations such as bottom trawling. Commercial trawlingis the most recurrent and pervasive of human impacts on the deep-sea floor,but studies on its consequences on the biogeochemistry of deep-sea sedimentsare still scarce. Pigments, fatty acids, amino acids and carbohydrates wereanalysed in sediments from the flanks of the La Fonera (Palamós)submarine canyon (NW Mediterranean Sea), where a commercial bottom trawlingfishery has been active for more than 70 yr. More specifically, weinvestigated how trawling-induced sediment reworking affects the quality ofsedimentary organic matter which reaches the seafloor and accumulates in thesediment column, which is fundamental for the development of benthiccommunities. Sediment samples were collected during two oceanographic cruisesin spring and autumn 2011. The sampled sites included trawl fishing groundsas well as pristine (control) areas. We report that bottom trawling in theflanks of the La Fonera Canyon has caused an alteration of the quality of theorganic matter accumulated in the upper 5 cm of the seafloor. The use of awide pool of biochemical tracers characterized by different reactivity todegradation allowed for us to discriminate the long-term effects oftrawl-induced sediment reworking from the natural variability caused by theseasonal cycle of production and sinking of biogenic particles. Differencesbetween untrawled and trawled areas were evidenced by labile amino acids,while differences between spring and autumn samples were detected only by themore labile indicators chlorophyll a and monounsaturated fatty acids.These results suggest that changes in the biochemical composition of thesedimentary organic matter caused by bottom trawling can be more relevantthan those associated with natural seasonality and pose serious concernsabout the ecological sustainability of deep-sea trawling activities.

[学科分类] 地球化学与岩石