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Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer waters, acidification rates in these areas are faster than those in sub-tropical regions. The present study investigates the effects of ocean acidification on sediment composition, processes and sediment-water fluxes in an Arctic coastal system. Undisturbed sediment cores, exempt of large dwelling organisms, were collected, incubated for a period of 14 days, and subject to a gradient of pCO2 covering the range of values projected for the end of the century. On five occasions during the experimental period, the sediment cores were isolated for flux measurements (oxygen, alkalinity, dissolved inorganic carbon, ammonium, nitrate, nitrite, phosphate and silicate). At the end of the experimental period, denitrification rates were measured and sediment samples were taken at several depth intervals for solid-phase analyses. Most of the parameters and processes (i.e. mineralization, denitrification) investigated showed no relationship with the overlying seawater pH, suggesting that ocean acidification will have limited impacts on the microbial activity and associated sediment-water fluxes on Arctic shelves, in the absence of active bio-irrigating organisms. Only following a pH decrease of 1 pH unit, not foreseen in the coming 300 years, significant enhancements of calcium carbonate dissolution and anammox rates were observed. Longer-term experiments on different sediment types are still required to confirm the limited impact of ocean acidification on shallow Arctic sediment processes as observed in this study.

The carbon metabolism of two marine sponges, Haliclona oculata and Dysidea avara , has been studied using a 13 C isotope pulse-chase approach. The sponges were fed 13 C-labeled diatoms ( Skeletonema costatum ) for 8 h and they took up between 75 and 85%. At different times, sponges were sampled for total 13 C enrichment, and fatty acid (FA) composition and 13 C enrichment. Algal biomarkers present in the sponges were highly labeled after feeding but their labeling levels decreased until none was left 10 days after enrichment. The sponge-specific FAs incorporated 13 C label already during the first day and the amount of 13 C label inside these FAs kept increasing until 3 weeks after labeling. The algal-derived carbon captured by the sponges during the 8-h feeding period was thus partly respired and partly metabolized during the weeks following. Apparently, sponges are able to capture enough food during short periods to sustain longer-term metabolism. The change of carbon metabolic rate of fatty acid synthesis due to mechanical damage of sponge tissue was studied by feeding sponges with 13 C isotope-labeled diatom ( Pheaodactylum tricornutum ) either after or before damaging and tracing back the 13 C content in the damaged and healthy tissue. The filtration and respiration in both sponges responded quickly to damage. The rate of respiration in H. oculata reduced immediately after damage, but returned to its initial level after 6 h. The 13 C data revealed that H. oculata has a higher metabolic rate in the tips where growth occurs compared to the rest of the tissue and that the metabolic rate is increased after damage of the tissue. For D. avara , no differences were found between damaged and non-damaged tissue. However, the filtration rate decreased directly after damage.

Objective: To determine in a rural black population the incidence of common forms of respiratory distress (RD) and low birth weight (LBW), the mortality from RD and the perinatal mortality rate (PMR)., Design: A prospective study in a context in which about 90% of the community's births take place within the health service and unwell neonates are transferred to hospital., Setting: The Donald Fraser health ward, Northern Province (then Venda), which serves a population of about 180,000 through 21 clinics and health centres and a 450-bed hospital., Subjects: 7,539 infants born alive between 1 February 1992 and 31 January 1993, of whom 48 developed RD., Outcome Measures: Hjalmarson's classification of RD, modified for local conditions. Criteria depended on clinical signs, chest radiography, neutrophil count in blood and gastric aspirate, blood cultures and postmortem examination., Results: RD 6.4/1,000 livebirths (95% CI 4.6-8.2); infection 2.6/1,000 livebirths (95% CI 1.4-3.7); hyaline membrane disease (HMD) 0.9/1,000 livebirths (95% CI 0.2-1.6); pulmonary maladaptation (transient tachypnoea) 0.8/1,000 livebirths (95% CI 0.2-1.4); mortality from RD 2.1/1,000 livebirths (95% CI 1.1-3.2); incidence of LBW 7.9% (95% CI 7.3-8.5); PMR 19.8/1,000 livebirths (95% CI 17-23)., Conclusion: A strikingly low incidence of neonatal RD in general and of HMD in particular was found in a rural black population, probably related to a low LBW incidence. Infection was the commonest cause of RD.