Nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance in the diatom Phaeodactylum tricornutum

[摘要] It has been proposed that ocean acidification (OA) will interact with otherenvironmental factors to influence the overall impact of global change onbiological systems. Accordingly we investigated the influence of nitrogenlimitation and OA on the physiology of diatoms by growing the diatomPhaeodactylum tricornutum Bohlin under elevated (1000 μatm; high CO₂ – HC) or ambient (390 μatm; low CO₂ – LC)levels of CO₂ with replete (110 μmol L⁻¹; high nitrate – HN) or reduced(10 μmol L⁻¹; low nitrate – LN) levels of NO₃^- and subjecting thecells to solar radiation with or without UV irradiance to determine theirsusceptibility to UV radiation (UVR, 280–400 nm). Our results indicate thatOA and UVB induced significantly higher inhibition of both thephotosynthetic rate and quantum yield under LN than under HN conditions. UVAor/and UVB increased the cells' non-photochemical quenching (NPQ) regardlessof the CO₂ levels. Under LN and OA conditions, activity of superoxidedismutase and catalase activities were enhanced, along with the highestsensitivity to UVB and the lowest ratio of repair to damage of PSII.HC-grown cells showed a faster recovery rate of yield under HN but not underLN conditions. We conclude therefore that nutrient limitation makes cellsmore prone to the deleterious effects of UV radiation and that HC conditions(ocean acidification) exacerbate this effect. The finding that nitratelimitation and ocean acidification interact with UV-B to reducephotosynthetic performance of the diatom P. tricornutum implies that ocean primaryproduction and the marine biological C pump will be affected by OA undermultiple stressors.

[学科分类] 地球化学与岩石