Phytoplankton responses and associated carbon cycling during shipboard carbonate chemistry manipulation experiments conducted around Northwest European shelf seas

[摘要] The ongoing oceanic uptake of anthropogenic carbon dioxide (CO₂) issignificantly altering the carbonate chemistry of seawater, a phenomenonreferred to as ocean acidification. Experimental manipulations have beenincreasingly used to gauge how continued ocean acidification will potentiallyimpact marine ecosystems and their associated biogeochemical cycles in thefuture; however, results amongst studies, particularly when performed onnatural communities, are highly variable, which may reflectcommunity/environment-specific responses or inconsistencies in experimentalapproach. To investigate the potential for identification of more genericresponses and greater experimentally reproducibility, we devised andimplemented a series (n= 8) of short-term (2–4 days) multi-level (≥4 conditions) carbonate chemistry/nutrient manipulation experiments on arange of natural microbial communities sampled in Northwest European shelfseas. Carbonate chemistry manipulations and resulting biological responseswere found to be highly reproducible within individual experiments and to alesser extent between geographically separated experiments. Statisticallyrobust reproducible physiological responses of phytoplankton to increasingpCO₂, characterised by a suppression of net growth for small-sizedcells (<10 μm), were observed in the majority of theexperiments, irrespective of natural or manipulated nutrient status.Remaining between-experiment variability was potentially linked to initialcommunity structure and/or other site-specific environmental factors.Analysis of carbon cycling within the experiments revealed the expectedincreased sensitivity of carbonate chemistry to biological processes athigher pCO₂ and hence lower buffer capacity. The results thusemphasise how biogeochemical feedbacks may be altered in the futureocean.

[学科分类] 地球化学与岩石