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Coralline algae play foundational roles in coastal ecosystems and are globally significant components of benthic habitats down to the limits of the photic zone. Despite their vulnerability to ocean acidification (OA) and importance in low light environments, there is a limited understanding of how the interplay between irradiance and OA influences coralline reproduction and recruitment. To better understand this interaction, a 212 d experiment was run exposing coralline communities to 2 pH levels (present-day pH 8.03, OA pH 7.65) and a gradient of daily light dose (0.35, 0.17 and 0.1 mol m−2 d−1), based on in situ measurements. In the highest light dose treatment, lowered seawater pH projected for 2100 (pH(T) 7.65) reduced recruitment by 56%. This OA-driven reduction in recruitment was amplified under reduced light, with recruitment near zero in the lowest light treatment. This study shows, for the first time, the increased vulnerability of coralline community recruitment to OA under low light. Coralline algae are known to be the deepest growing macroalgae and thus, in these low light zones, OA may have the potential to reduce coralline depth distribution.

Elevated atmospheric CO 2 concentrations are contributing to ocean acidification (reduced seawater pH and carbonate concentrations), with potentially major ramifications for marine ecosystems and their functioning. Using a novel in situ experiment we examined impacts of reduced seawater pH on Antarctic sea ice-associated microalgal communities, key primary producers and contributors to food webs. pH levels projected for the following decades-to-end of century (7.86, 7.75, 7.61), and ambient levels (7.99), were maintained for 15 d in under-ice incubation chambers. Light, temperature and dissolved oxygen within the chambers were logged to track diurnal variation, with pH, O 2 , salinity and nutrients assessed daily. Uptake of CO 2 occurred in all treatments, with pH levels significantly elevated in the two extreme treatments. At the lowest pH, despite the utilisation of CO 2 by the productive microalgae, pH did not return to ambient levels and carbonate saturation states remained low; a potential concern for organisms utilising this under-ice habitat. However, microalgal community biomass and composition were not significantly affected and only modest productivity increases were noted, suggesting subtle or slightly positive effects on under-ice algae. This in situ information enables assessment of the influence of future ocean acidification on under-ice community characteristics in a key coastal Antarctic habitat.

Nitrogen metabolism in Enteromorpha intestinalis from 3 contrasting populations in the Auckland region, New Zealand, was investigated. The sites (intertidal flats at Laingholm in the Manukau Harbour and Mangemangeroa and rockpools at Waterfall Reef) were chosen as they provided a range of ammonium enrichment. Seawater at Laingholm had higher levels of ammonium and total inorganic nitrogen compared with the other 2 sites. However, mean nitrate levels in Mangemangeroa seawater were similar to those measured at Laingholm. Seawater at Waterfall Reef had the lowest concentrations of ammonium and nitrate. At all 3 sites, E. intestinalis was found high in the intertidal. At Laingholm, the ammonium-enriched site, plants were immersed for 90 min at high tide; during this period the plants look up sufficient ammonium to increase their nitrogen content by 10%. The higher levels of inorganic nitrogen in the seawater at Laingholm resulted in higher levels of tissue nitrogen, chl a and b, glutamine and asparagine, and lower nitrogen-specific rates of ammonium assimilation (measured in the laboratory in the presence of saturating concentrations of ammonium) in E. intestinalis at this site. There were strong positive correlations between seawater concentrations of ammonium and the level of glutamine and between levels of chl a and b and tissue nitrogen in E. intestinalis. The nitrogen-specific rate of ammonium assimilation decreased as the nitrogen content of the plant increased and reached a minimum value above a nitrogen content of 1 to 2% or a glutamine level of 5 mu mol per g dry weight (DW). This glutamine level corresponded to a seawater ammonium concentration of 6 mu M. The nitrogen-specific rate of ammonium assimilation provides a novel and important bioindicator of the link between the concentration of inorganic nitrogen in the environment and the nitrogen status of the plant.

M.W. Taylor, N.G. Barr, C.M. Grant and T.A.V. Rees. 2006. Changes in amino acid composition of Ulva intestinalis (Chlorophyceae) following addition of ammonium or nitrate. Phycologia 45: 270-276. DOI: 10.2216/05-15.1 Nitrogen assimilation was investigated in the marine macroalga Ulva intestinalis. Following incubation of the alga in the presence of ammonium or nitrate, resulting changes in free amino acid content were determined. After 10 h, the largest changes by far occurred in the levels of glutamine and asparagine, which both increased more than 10-fold regardless of nitrogen source. Other amino acids increased slightly, but these two - together with their precursors glutamate and aspartate - comprised 83 and 76% of the total free protein amino acid-N pool upon addition of ammonium or nitrate, respectively. In subsequent time-course experiments, with ammonium as nitrogen source, glutamate initially decreased (with a concomitant increase in glutamine) before recovering to at least its original level. Asparagine levels began to increase after 1 h. Saturation of the glutamine and glutamate pools occurred after approximately 6 h, and coincided with the transition from the surge phase of ammonium uptake to the internally controlled uptake phase. This study represents the first investigation into how levels of specific amino acids change during ammonium assimilation in macroalgae, and as such extends our current knowledge of this poorly understood process.

Nitrogen metabolism inEnteromorpha intestinalisfrom 3 contrasting populations in the Auckland region, New Zealand, was investigated. The sites (intertidal flats at Laingholm in the Manukau Harbour and Mangemangeroa and rockpools at Waterfall Reef) were chosen as they provided a range of ammonium enrichment. Seawater at Laingholm had higher levels of ammonium and total inorganic nitrogen compared with the other 2 sites. However, mean nitrate levels in Mangemangeroa seawater were similar to those measured at Laingholm. Seawater at Waterfall Reef had the lowest concentrations of ammonium and nitrate. At all 3 sites,E. intestinaliswas found high in the intertidal. At Laingholm, the ammonium-enriched site, plants were immersed for 90 min at high tide; during this period the plants took up sufficient ammonium to increase their nitrogen content by 10%. The higher levels of inorganic nitrogen in the seawater at Laingholm resulted in higher levels of tissue nitrogen, chlaandb, glutamine and asparagine, and lower nitrogen-specific rates of ammonium assimilation (measured in the laboratory in the presence of saturating concentrations of ammonium) inE. intestinalisat this site. There were strong positive correlations between seawater concentrations of ammonium and the level of glutamine and between levels of chlaandband tissue nitrogen inE. intestinalis. The nitrogen-specific rate of ammonium assimilation decreased as the nitrogen content of the plant increased and reached a minimum value above a nitrogen content of 1 to 2% or a glutamine level of 5 μmol per g dry weight (DW). This glutamine level corresponded to a seawater ammonium concentration of 6 μM. The nitrogen-specific rate of ammonium assimilation provides a novel and important bioindicator of the link between the concentration of inorganic nitrogen in the environment and the nitrogen status of the plant.

Objective To perform a systematic review of studies that assessed the potential of patient decision support interventions (decision aids) to generate savings. Design Systematic review. Data sources After registration with PROSPERO, we searched 12 databases, from inception to 15 March 2013, using relevant MeSH terms and text words. Included studies were assessed with Cochrane’s risk of bias method and Drummond’s quality checklist for economic studies. Per patient costs and projected savings associated with introducing patient decision support interventions were calculated, as well as absolute changes in treatment rates after implementation. Eligibility criteria Studies were included if they contained quantitative economic data, including savings, spending, costs, cost effectiveness analysis, cost benefit analysis, or resource utilization. We excluded studies that lacked quantitative data on savings, costs, monetary value, and/or resource utilization. Results After reviewing 1508 citations, we included seven studies with eight analyses. Of these seven studies, four analyses predicted system-wide savings, with two analyses from the same study. The predicted savings range from $8 (£5, €6) to $3068 (£1868, €2243) per patient. Larger savings accompanied reductions in treatment utilization rates. The impact on utilization rates was mixed. Authors used heterogeneous methods to allocate costs and calculate savings. Quality scores were low to moderate (median 4.5, range 0-8 out of 10), and risk of bias across the studies was moderate to high (3.5, range 3-6 out of 6), with studies predicting the most savings having the highest risk of bias. The range of issues identified in the studies included the relative absence of sensitivity analyses, the absence of incremental cost effectiveness ratios, and short time periods. Conclusion Although there is evidence to show that patients choose more conservative approaches when they become better informed, there is insufficient evidence, as yet, to be confident that the implementation of patient decision support interventions leads to system-wide savings. Further work—with sensitivity analyses, longer time horizons, and more contexts—is required to avoid premature or unrealistic expectations that could jeopardize implementation and lead to the loss of already proved benefits. Registration PROSPERO registration CRD42012003421.