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The first symposium on ``The Ocean in a High-CO2 World'' in 2004 proved to be a landmark event in our understanding of the seriousness of ocean acidification, as reported in Oceanography (Cicerone et al., 2004). The scientific community reunited in 2008 for a second symposium on ``The Ocean in a High-CO2 World.'' During the four years between the two symposia, more scientific papers were published on the topic of ocean acidification than during the preceding 55 years. Ocean acidification is now widely cited in the press and is familiar to many nonscientists. Participants at the 2008 symposium identified new research priorities and stressed the importance of improving international coordination to facilitate agreements on protocols, methods, and data reporting in order to optimize limited resources by greater sharing of materials, facilities, expertise, and data. Despite major uncertainties, the research community must find ways to scale up understanding of individual organisms' responses to provide meaningful predictions of ocean acidification's effects on food webs, fisheries, marine ecosystems, coastal erosion, and tourism. Easy-to-understand information, such as simple indicators of change and of thresholds beyond which marine ecosystems will not recover, is also needed for management and policymaking.

Non-methane hydrocarbons (NMHCs) are produced naturally in the ocean and by terrestrial vegetation. Owing to its high reactivity and flux, isoprene (2-methyl-1,3-butadiene) is important in controlling the balance of atmospheric oxidants, and altering air quality on both local and global scales. Here we show, for the first time, that macroalgae (seaweeds) emit isoprene and a number of other non-methane hydrocarbons (NMHCs). We observed NMHC concentrations in rockpools containing macroalgae and estimated fluxes to the atmosphere over a full diurnal cycle. Emissions at our temperate coastal site (Mace Head, Ireland) in autumn are intermediate in magnitude between terrestrial and ocean fluxes (on a unit area basis), and may contribute significant concentrations to the local atmosphere. We also carried out a series of controlled laboratory experiments focusing on isoprene, in natural and artificial light, and under different temperature conditions involving red (Chondrus crispus, Asparagopsis armata), green (Ulva intestinalis, formerly known as Enteromorpha intestinalis) and brown (Laminaria digitata, Ascophyllum nodosum, Pelvetia canaliculata, Fucus vesiculosus, Fucus serratus, Halidrys siliquosa and Laminaria saccharina) macroalgae commonly found on the west coast of Ireland. We observed NMHC emissions from all the algae investigated and emissions were dominated by alkenes. Production is species-dependent, temperature-dependent and related to light availability. We discuss our observations in the context of what is known about the production of isoprene and ethene in higher plants.

A number of atmospherically important trace gases (dimethyl sulphide (DMS), methyl iodide (CH3I), and nonmethane hydrocarbons (NMHCs)) were measured simultaneously in the eastern Atlantic Ocean during May 1997. This investigation was part of the U.K. Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) Community Research Program and covered a 200 by 200 nautical mile (1 nautical mile is 1.852 km) area to the west of the Mace Head Atmospheric Research Station on the coast of Ireland. Different spatial and temporal patterns were observed for each of the gases, showing that distinct sources dominate their production in this region: specific species of phytoplankton (DMS), macroalgae (CH3I), total phytoplankton biomass (isoprene), and photochemistry (ethene). Sea-to-air fluxes of the gases are calculated for near and offshore domains, and their temporal variations are discussed. A simple photochemical box model has been used to assess the contributions of the gas fluxes to the levels of the gases observed at Mace Head, Results show that the area studied may constitute a substantial source of DMS, a weak source of CH 3 I, a small source of ethene at night, and an insignificant source of isoprene to atmospheric levels of these gases measured at Mace Head in western Ireland.

Dimethyl sulphide (DMS) and particulate and dissolved fractions of dimethylsulphoniopropionate (DMSPp and DMSPd) were measured on two simultaneous cruises through the Drake Passage to the Bellingshausen Sea, Antarctica, during October to December 1992. Overall, average surface water concentrations for DMS and DMSPp were 2 nM (0.15–27 nM) and 25.6 nM (2–69 nM), respectively. Higher concentrations (DMS 5.8 and DMSPp 41.2 nM) were observed in a phytoplankton bloom forming a band between 67.2° and 68.2°S, associated with the Southern Polar Front. Concentrations of DMS + DMSP in ice were very high (up to 546 nM) but in the underlying water were 20 to 500 times lower. Comparison of sulphur data, pigments and phytoplankton species counts showed correlation of DMSPp with 19'-hexanoyloxyfucoxanthin (Hex) and Phaeocystis sp. A seasonal cycle for DMS in Antarctic surface waters, based on all available literature data, is discussed in terms of the probable Antarctic Ocean contribution to the global ocean DMS flux.

Jickells, T.D. ... et. al.-- 34 pages, 6 tables, 10 figures We report the results of an experiment in the Northeast Atlantic in which sulphur hexafluoride (SF6) was released within an eddy and the behaviour of trace gases, nutrients and productivity followed within a Lagrangian framework over a period of 24 days. Measurements were also made in the air above the eddy in order to estimate air–sea exchange rates for some components. The physical, biological and biogeochemical properties of the eddy resemble those of other eddies studied in this area, suggesting that the results we report may be applicable beyond the specific eddy studied. During a period of low wind speed at the start of the experiment, we are able to quantitatively describe and balance the nutrient and carbon budgets for the eddy. We also report concentrations of various trace gases in the region which are similar to those observed in other studies and we estimate exchange rates for several trace gases. We show that the importance of gas exchange over other loss terms varies with time and also varies for the different gases. We show that the various trace gases considered (CO2, dimethyl sulphide (DMS), N2O, CH4, non-methane-hydrocarbons, methyl bromide, methyl iodide and volatile selenium species) are all influenced by physical and biological processes, but the overall distribution and temporal variability of individual gases are different to one another. A storm disrupted the stratification in the eddy during the experiment, resulting in enhanced nutrient supply to surface waters, enhanced gas exchange rates and a change in plankton community, which we quantify, although overall productivity was little changed. Emphasis is placed on the regularity of storms in the temperate ocean and the importance of these stochastic processes in such systems This is contribution no. ACP175 of the NERC ACSOE Thematic Programme. NERC grants GST/02/1276 supported the work of Jickells and Spokes, GST/02/1278 the work of Liss and Nightingale together with core funding to the Plymouth Marine Laboratory (PML) while the ACSOE core programme supported Broadgate and the shiptime costs, NERC grant GR9/3467 to G.S. supported Moncoiffé and Gilpin. Steinke was supported by NERC grant GR3/10956. The University of Newcastle upon Tyne Research Committee provided funding to support T. Frost. The work of Simó and Pedrós-Alió was supported by the Spanish McyT grant MAR97-1885-E