Floating plastic accumulation and distribution around Kuroshio Current, western North Pacific

Nanoplastics impair growth and nitrogen fixation of marine nitrogen-fixing cyanobacteria

Nanoplastics pollution is a growing environmental problem worldwide. Recent research has demonstrated the toxic effects of nanoplastics on various marine organisms. However, the influences of nanoplastics on marine nitrogen-fixing cyanobacteria, a critical nitrogen source in the ocean, remained unknown. Here, we report that nanoplastics exposure significantly reduced growth, photosynthetic, and nitrogen fixation rates of Crocosphaera watsonii (a major marine nitrogen-fixing cyanobacterium). Transcriptomic analysis revealed that nanoplastics might harm C. watsonii via downregulation of photosynthetic pathways and DNA damage repair genes, while genes for respiration, cell damage, nitrogen limitation, and iron (and phosphorus) scavenging were upregulated. The number and size of starch grains and electron-dense vacuoles increased significantly after nanoplastics exposure, suggesting that C. watsonii allocated more resources to storage instead of growth under stress. We propose that nanoplastics can damage the cell (e.g., DNA, cell membrane, and membrane-bound transporters), inhibit nitrogen and carbon fixation, and hence lead to nutrient limitation and impaired growth. Our findings suggest the possibility that nanoplastics pollution could reduce the new nitrogen input and hence affect the productivity in the ocean. The impact of nanoplastics on marine nitrogen fixation and productivity should be considered when predicting the ecosystem response and biogeochemical cycling in the changing ocean.

Abundance and distribution of marine litter on the beaches of Okinawa Island, Japan

This study evaluated the distribution and abundance of marine litter on 30 beaches around Okinawa Island, Japan. Beach quality indices and multivariate statistical analyses were used to assess the quality of the beaches and their pollution patterns. A total of 11,626 items weighing 513.49 kg with an average density of 0.13 ± 0.10 items/m2 were collected. Litter was dominated by plastics (81.72 %), broken glass (8.38 %), and cigarette butts (7.44 %), and 74.05 % of total litter was from land-based sources. Single-use plastics (SUPs) were present in all surveyed beaches and made up 30.54 % of the total litter. The clean coast index (CCI), plastic abundance index (PAI), and hazardous index (HI) were between 0.1 and 7.6, 0.1-4.0 and 0.01-1.42, respectively, indicating low to moderate levels of pollution of Okinawan beaches. This study should aid in the formation of strategies to deal with marine litter in Okinawa, other areas of Japan and the Asia-Pacific region.

Surface dispersion of coastal discharges in North America towards the Great Pacific Garbage Patch

This research addresses the surface dispersion of coastal discharges in North America that end up at the Great Pacific Garbage Patch. The evolution of the discharged concentration is calculated through statistical simulations using transition matrices and dispersion ellipses, both based on historical records of surface drifter trajectories. The discharge points are adjacent to urban areas distributed along the coast. The preferential routes, times of arrival, and relative contributions of each site to the accumulation area are quantified. A new statistical delimitation of the position, area and orientation of the garbage patch is proposed. Additional experiments suggest that the tracer retention during the summer is influenced by the low-level atmospheric anticyclone in the Northeastern Pacific, which enhances the Ekman drift and hence favours debris convergence. This effect is reduced when the anticyclone weakens in winter, thus decreasing the debris retention and promoting its westward dispersal by the trade winds.