Riebesell U, Schulz K G, Bellerby R G J, Botros M, Fritsche P, Meyerhöfer M, Neill C, Nondal G, Oschlies A, Wohlers J, Zöllner E
Leibniz Institute of Marine Sciences, IFM-GEOMAR, 24105 Kiel, Germany.
Nature. 2007 Nov 22;450(7169):545-8. doi: 10.1038/nature06267. Epub 2007 Nov 11.
The oceans have absorbed nearly half of the fossil-fuel carbon dioxide (CO2) emitted into the atmosphere since pre-industrial times, causing a measurable reduction in seawater pH and carbonate saturation. If CO2 emissions continue to rise at current rates, upper-ocean pH will decrease to levels lower than have existed for tens of millions of years and, critically, at a rate of change 100 times greater than at any time over this period. Recent studies have shown effects of ocean acidification on a variety of marine life forms, in particular calcifying organisms. Consequences at the community to ecosystem level, in contrast, are largely unknown. Here we show that dissolved inorganic carbon consumption of a natural plankton community maintained in mesocosm enclosures at initial CO2 partial pressures of 350, 700 and 1,050 microatm increases with rising CO2. The community consumed up to 39% more dissolved inorganic carbon at increased CO2 partial pressures compared to present levels, whereas nutrient uptake remained the same. The stoichiometry of carbon to nitrogen drawdown increased from 6.0 at low CO2 to 8.0 at high CO2, thus exceeding the Redfield carbon:nitrogen ratio of 6.6 in today's ocean. This excess carbon consumption was associated with higher loss of organic carbon from the upper layer of the stratified mesocosms. If applicable to the natural environment, the observed responses have implications for a variety of marine biological and biogeochemical processes, and underscore the importance of biologically driven feedbacks in the ocean to global change.
自工业化前时代以来，海洋吸收了近一半排放到大气中的化石燃料二氧化碳（CO₂），导致海水pH值和碳酸盐饱和度出现可测量的下降。如果CO₂排放量继续以当前速度上升，上层海洋的pH值将降至数千万年以来未曾出现过的水平，关键的是，其变化速率比这一时期的任何时候都要快100倍。最近的研究表明，海洋酸化对多种海洋生物形式，特别是钙化生物产生了影响。相比之下，群落至生态系统层面的后果在很大程度上仍不为人知。在此，我们表明，在中宇宙围隔中维持的自然浮游生物群落，在初始CO₂分压分别为350、700和1050微大气压的情况下，其溶解无机碳的消耗量会随着CO₂浓度的升高而增加。与当前水平相比，在升高的CO₂分压下，该群落消耗的溶解无机碳多出39%，而营养物质的吸收量保持不变。碳与氮的吸收化学计量比从低CO₂时的6.0增加到高CO₂时的8.0，从而超过了当今海洋中6.6的雷德菲尔德碳氮比。这种额外的碳消耗与分层中宇宙上层有机碳的更高损失有关。如果这些观察到的反应适用于自然环境，那么它们对各种海洋生物和生物地球化学过程都具有影响，并强调了海洋中生物驱动的反馈对全球变化的重要性。
