Search

Abstract The near-term progression of ocean acidification (OA) is projected to bring about sharp changes in the chemistry of coastal upwelling ecosystems. The distribution of OA exposure across these early-impact systems, however, is highly uncertain and limits our understanding of whether and how spatial management actions can be deployed to ameliorate future impacts. Through a novel coastal OA observing network, we have uncovered a remarkably persistent spatial mosaic in the penetration of acidified waters into ecologically-important nearshore habitats across 1,000 km of the California Current Large Marine Ecosystem. In the most severe exposure hotspots, suboptimal conditions for calcifying organisms encompassed up to 56% of the summer season, and were accompanied by some of the lowest and most variable pH environments known for the surface ocean. Persistent refuge areas were also found, highlighting new opportunities for local adaptation to address the global challenge of OA in productive coastal systems.

A buoy based instrument platform (the "O-buoy") was designed, constructed, and field tested for year-round measurement of ozone, bromine monoxide, carbon dioxide, and meteorological variables over Arctic sea ice. The O-buoy operated in an autonomous manner with daily, bi-directional data transmissions using Iridium satellite communication. The O-buoy was equipped with three power sources: primary lithium-ion battery packs, rechargeable lead acid packs, and solar panels that recharge the lead acid packs, and can fully power the O-buoy during summer operation. This system was designed to operate under the harsh conditions present in the Arctic, with minimal direct human interaction, to aid in our understanding of the atmospheric chemistry that occurs in this remote region of the world. The current design requires approximately yearly maintenance limited by the lifetime of the primary power supply. The O-buoy system was field tested in Elson Lagoon, Barrow, Alaska from February to May 2009, and deployed in the Beaufort Sea in October 2009. Here, we describe the design and present preliminary data.

High-resolution time series measurements of temperature, salinity, pH and pCO 2 were made during the period October 2014-September 2015 at the midpoint of Shark River, a 15km tidal river that originates in the freshwater Everglades of south Florida (USA) and discharges into the Gulf of Mexico. Dissolved inorganic carbon dynamics in this system vary over time, and during this study could be classified into three distinct regimes corresponding to October 2014-February 2015 (a wet to dry season transition period), March-May 2015 (dry period) and July-September 2015 (wet period). Average net longitudinal dissolved inorganic carbon (DIC) fluxes and air-water CO 2 fluxes from the Shark River estuary were determined for the three periods. Net DIC fluxes to the coast were estimated to vary between 23.2 and 25.4×10 5 mold -1 with an average daily DIC flux of 24.3×10 5 mold -1 during the year of study. CO 2 emissions ranged between 5.5 and 7.8×10 5 mold -1 with an average daily value of 6.4×10 5 mold -1 during the year. The differences in estuarine carbon fluxes during the study period are attributed to differences in the relative importance of hydro-climatological drivers. Results suggest that, during months characterized by reduced rainfall, carbon fluxes are affected by water management via control structures in the upstream Everglades marshes. During months with high rainfall, when culverts are closed and rainfall events are more frequent, carbon fluxes depend more on other forcings, such as rainfall and groundwater discharge., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The near-term progression of ocean acidification (OA) is projected to bring about sharp changes in the chemistry of coastal upwelling ecosystems. The distribution of OA exposure across these early-impact systems, however, is highly uncertain and limits our understanding of whether and how spatial management actions can be deployed to ameliorate future impacts. Through a novel coastal OA observing network, we have uncovered a remarkably persistent spatial mosaic in the penetration of acidified waters into ecologically-important nearshore habitats across 1,000 km of the California Current Large Marine Ecosystem. In the most severe exposure hotspots, suboptimal conditions for calcifying organisms encompassed up to 56% of the summer season, and were accompanied by some of the lowest and most variable pH environments known for the surface ocean. Persistent refuge areas were also found, highlighting new opportunities for local adaptation to address the global challenge of OA in productive coastal systems.

Oceanic iron (Fe) fertilization experiments have advanced the understanding of how Fe regulates biological productivity and air-sea carbon dioxide (CO(2)) exchange. However, little is known about the production and consumption of halocarbons and other gases as a result of Fe addition. Besides metabolizing inorganic carbon, marine microorganisms produce and consume many other trace gases. Several of these gases, which individually impact global climate, stratospheric ozone concentration, or local photochemistry, have not been previously quantified during an Fe-enrichment experiment. We describe results for selected dissolved trace gases including methane (CH(4)), isoprene (C(5)H(8)), methyl bromide (CH(3)Br), dimethyl sulfide, and oxygen (O(2)), which increased subsequent to Fe fertilization, and the associated decreases in concentrations of carbon monoxide (CO), methyl iodide (CH(3)I), and CO(2) observed during the Southern Ocean Iron Enrichment Experiments.

Direct oceanic disposal of fossil fuel CO2 is being considered as a possible means to moderate the growth rate of CO2 in the atmosphere. We have measured the rise rate and dissolution rate of freely released CO2 droplets in the open ocean to provide fundamental data for carbon sequestration options. A small amount of liquid CO2 was released at 800 m, at 4.4 degrees C, and the rising droplet stream was imaged with a HDTV camera carried on a remotely operated vehicle. The initial rise rate for 0.9-cm diameter droplets was 10 cm/s at 800 m, and the dissolution rate was 3.0 micromol cm(-2) s(-1). While visual contact was maintained for 1 h and over a 400 m ascent, 90% of the mass loss occurred within 30 min over a 200 m ascent above the release point. Images of droplets crossing the liquid-gas-phase boundary showed formation of a gas head, pinching off of a liquid tail, and rapid gas bubble separation and dissolution.

Field experiments were conducted to test ideas for fossil fuel carbon dioxide ocean disposal as a solid hydrate at depths ranging from 349 to 3627 meters and from 8 degrees to 1.6 degrees C. Hydrate formed instantly from the gas phase at 349 meters but then decomposed rapidly in ambient seawater. At 3627 meters, the seawater-carbon dioxide interface rose rapidly because of massive hydrate formation, forcing spillover of the liquid carbon dioxide from the container. A strong barrier between the liquid carbon dioxide and interaction with the sediments was observed. A pool of liquid carbon dioxide on the sea floor would expand in volume more than four times, forming hydrate, which will dissolve.

We show, from recent data obtained at specimen North Pacific stations, that the fossil fuel CO2 signal is strongly present in the upper 400 m, and that we may consider areal extrapolations from geochemical surveys to determine the magnitude of ocean fossil fuel CO2 uptake. The debate surrounding this topic is illustrated by contrasting reports which suggest, based upon atmospheric observations and models, that the oceanic CO2 sink is small at these latitudes; or that the oceanic CO2 sink, based upon oceanic data and models, is large. The difference between these two estimates is at least a factor of two. There are contradictions arising from estimates based on surface partial pressures of CO2 alone, where the signal sought is small compared with regional and seasonal variability; and estimates of the accumulated subsurface burden, which correlates well other oceanic tracers. Ocean surface waters today contain about 45 micromol.kg-1 excess CO2 compared with those of the preindustrial era, and the signal is rising rapidly. What limits should we place on such calculations? The answer lies in the scientific questions to be asked. Recovery of the fossil fuel CO2 contamination signal from analysis of ocean water masses is robust enough to permit reasonable budget estimates. However, because we do not have sufficient data from the preindustrial ocean, the estimation of the required Redfield oxidation ratio in the upper several hundred meters is already blurred by the very fossil fuel CO2 signal we seek to resolve.