Project description:Global warming has driven a loss of dissolved oxygen in the ocean in recent decades. We demonstrate the potential for an additional anthropogenic driver of deoxygenation, in which zooplankton consumption of microplastic reduces the grazing on primary producers. In regions where primary production is not limited by macronutrient availability, the reduction of grazing pressure on primary producers causes export production to increase. Consequently, organic particle remineralisation in these regions increases. Employing a comprehensive Earth system model of intermediate complexity, we estimate this additional remineralisation could decrease water column oxygen inventory by as much as 10% in the North Pacific and accelerate global oxygen inventory loss by an extra 0.2-0.5% relative to 1960 values by the year 2020. Although significant uncertainty accompanies these estimates, the potential for physical pollution to have a globally significant biogeochemical signal that exacerbates the consequences of climate warming is a novel feedback not yet considered in climate research.
Project description:Marine microplastic is pervasive, polluting the remotest ecosystems including the Southern Ocean. Since this region is already undergoing climatic changes, the additional stress of microplastic pollution on the ecosystem should not be considered in isolation. We identify potential hotspot areas of ecological impact from a spatial overlap analysis of multiple data sets to understand where marine biota are likely to interact with local microplastic emissions (from ship traffic and human populations associated with scientific research and tourism). Then we account for cumulative effects by identifying which areas with potential elevated microplastic-biota interaction are already subject to climate change related stresses (ocean warming and acidification). Our analysis indicates that biologically productive coastal areas in proximity to populated facilities are where microplastics pose most risk to the ecosystem, and that the northern Antarctic Peninsula is likely to be the main risk hotspot. This study is the first to map the threat of microplastics to the Southern Ocean ecosystem in a multi-stressor context, locating where microplastic monitoring programmes and mitigation measures may be considered a matter of urgency.
Project description:Litter and plastic pollution in the marine environment is of major concern when considering the health of ocean ecosystems, and have become an important focus of ocean research during recent years. There is still significant uncertainty surrounding the distribution and impact of marine plastic litter on ocean ecosystems, and in particular on the nano- and microplastic fractions that are difficult to observe and may be harmful to marine organisms. Current estimates of ocean plastic concentrations only account for a small fraction of the approximated 8 million tons of plastic litter entering the oceans on an annual basis. Here, we present the distribution of 100-500 μm microplastic particles within the ocean mixed layer, covering a significant fraction of the ocean, in a near-synoptic survey. During The Ocean Race 2017/2018 edition (formerly known as Volvo Ocean Race), two yachts served as ships of opportunity that regularly took samples of microplastics on a regular schedule during their circumnavigation. This effort resulted in information on microplastic distribution along the race track in the ocean's upper, well-mixed, layer. We found concentrations ranging from 0-349 particles per cubic meter, but with large spatial variability. There was a tendency toward higher concentrations off south-western Europe and in the southwest Pacific, and indications of long-range transport of microplastic with major ocean currents.
Project description:To better understand unexpectedly low plastic loads at the ocean's surface compared with inputs, unidentified sinks must be located. Here, we present the microplastic (MP) budget for multi-compartments in the western Arctic Ocean (WAO) and demonstrate that Arctic sediments serve as important current and future sinks for MPs missing from the global budget. We identified an increase of 3% year-1 in MP deposition from sediment core observations. Relatively elevated MP abundances were found in seawater and surface sediments around the summer sea ice retreat region, implying enhanced MP accumulation and deposition facilitated by the ice barrier. We estimate 15.7 ± 2.30 × 1016 N and 0.21 ± 0.14 MT as total MP loads in the WAO with 90% (by mass) buried in the post-1930 sediments, which exceeds the global average of the current marine MP load. The slower increase in plastic burial versus production implies a lag in plastic delivery to the Arctic, indicating more pollution in the future.
Project description:It is widely understood that microplastics (MPs) are ubiquitous in the marine environment yet less is known about MP abundance in freshwater rivers, particularly those of the western United States. This study documents MP pollution along the Snake River (∼1735 km) and from its confluence with the Columbia River to the Pacific Ocean. Grab and plankton net samples (mesh size 100 μm) were collected from the top 25 cm of surface water every 80.5 river km. MPs were identified if they met visual criteria and were verified with the hot needle test. A small representative subset of MPs from the net samples (16.7%) were selected based on appearance for micro-Raman spectroscopy in effort to provide examples of polymer types found in this study. Seventy-five percent of grab samples and 92.8% of net samples contained MPs, with concentrations ranging from 0 to 5.405 MP L-1 and 0 to 0.014 MP L-1 (0 to 13.7 MP m-3), respectively. The majority of fragments, films and beads were between 100 μm and 333 μm. This study identifies potential hotspots of MP pollution along the Snake and Lower Columbia rivers and prioritizes areas where more intensive sampling is needed. Sites with low flow or those further down river had higher numbers and the top two hotspots were located in areas with low population density but high agricultural use. Monitoring MP abundance in freshwater systems is important for establishing baseline levels of MP pollution and can direct laboratory toxicology studies in using more environmentally relevant concentrations for a better indication of how MP pollution affects ecosystems.
Project description:Microplastic pollution, global warming, and invasive species are known threats to marine biota, but the impact of their simultaneous exposure is still not well understood. This study investigated whether the toxic effects posed by the invasive red seaweed Asparagopsis armata exudate (2%) to the mussel Mytilus galloprovincialis are amplified by a 96 h exposure to increased temperature (24 °C) and polyethylene microplastics (PE-MPs, 1 mg/L). Biochemical (neurotoxicity, energy metabolism, oxidative stress, and damage) and physiological (byssal thread production) responses were evaluated. The number of produced byssus greatly decreased under concomitant exposure to all stressors. The antioxidant defences were depleted in the gills of mussels exposed to temperature rises and PE-MPs, regardless of exudate exposure, preventing oxidative damage. Moreover, the heat shock protein content tended to decrease in all treatments relative to the control. The increased total glutathione in the mussels' digestive gland exposed to 24 °C, exudate, and PE-MPs avoided oxidative damage. Neurotoxicity was observed in the same treatment. In contrast, the energy metabolism remained unaltered. In conclusion, depending on the endpoint, simultaneous exposure to A. armata exudate, PE-MPs, and warming does not necessarily mean an amplification of their single effects. Studies focusing on the impact of multiple stressors are imperative to better understand the underlying mechanisms of this chronic exposure.