Persistence of plastic debris and its colonization by bacterial communities after two decades on the abyssal seafloor

The fate of plastic debris entering the oceans is largely unconstrained. Currently, intensified research is devoted to the abiotic and microbial degradation of plastic floating near the ocean surface for an extended period of time. In contrast, the impacts of environmental conditions in the deep sea on polymer properties and rigidity are virtually unknown. Here, we present unique results of plastic items identified to have been introduced into deep-sea sediments at a water depth of 4150 m in the eastern equatorial Pacific Ocean more than two decades ago. The results, including optical, spectroscopic, physical and microbial analyses, clearly demonstrate that the bulk polymer materials show no apparent sign of physical or chemical degradation. Solely the polymer surface layers showed reduced hydrophobicity, presumably caused by microbial colonization. The bacterial community present on the plastic items differed significantly (p < 0.1%) from those of the adjacent natural environment by a dominant presence of groups requiring steep redox gradients (Mesorhizobium, Sulfurimonas) and a remarkable decrease in diversity. The establishment of chemical gradients across the polymer surfaces presumably caused these conditions. Our findings suggest that plastic is stable over extended times under deep-sea conditions and that prolonged deposition of polymer items at the seafloor may induce local oxygen depletion at the sediment-water interface.

Effects of a deep-sea mining experiment on seafloor microbial communities and functions after 26 years

Future supplies of rare minerals for global industries with high-tech products may depend on deep-sea mining. However, environmental standards for seafloor integrity and recovery from environmental impacts are missing. We revisited the only midsize deep-sea disturbance and recolonization experiment carried out in 1989 in the Peru Basin nodule field to compare habitat integrity, remineralization rates, and carbon flow with undisturbed sites. Plough tracks were still visible, indicating sites where sediment was either removed or compacted. Locally, microbial activity was reduced up to fourfold in the affected areas. Microbial cell numbers were reduced by ~50% in fresh "tracks" and by <30% in the old tracks. Growth estimates suggest that microbially mediated biogeochemical functions need over 50 years to return to undisturbed levels. This study contributes to developing environmental standards for deep-sea mining while addressing limits to maintaining and recovering ecological integrity during large-scale nodule mining.

The Microwave Spectrum and Molecular Structure of the Hydrogen-Bonded Aniline-Methanol Complex

The rotational spectrum of aniline-methanol was investigated in the frequency region 3-19 GHz using a pulsed molecular beam Fourier transform microwave spectrometer. Sixty-three measured a- and b-type transitions show a fine structure due to internal rotation of the methyl group. The resulting A and E lines are additionally split into hyperfine components arising from quadrupole coupling of the (14)N nucleus. The torsional motion of the methyl group is hindered by an effective barrier V(3) of nearly 215 cm(-1), which is almost one-half of the methanol barrier height. The structure of the complex was calculated assuming a common symmetry plane for the monomers. These form a linear N vertical ellipsis H-O hydrogen bond. Its distance was found to be 3.03 Å, which is identical with that of aniline-water. Copyright 1999 Academic Press.