Community response to IRONEX
Community response to IRONEX
复制标题
社区对 IRONEX 的回应
作者：
K. Banse
SIR-1993年10月中旬在加拉帕戈斯群岛附近海域进行的铁施肥试验（IRONEX）1表明，未封闭的浮游植物的细胞分裂率最初很高，但由于加入铁而迅速提高，这与在其他高营养（硝酸盐）低叶绿素地区进行的瓶内试验中发现的情况一样。然而，在IRONEX实验后的几天里，浮游植物浓度的增加不仅仅是细胞生理学的问题，而是一种系统反应，导致细胞分裂率与放牧和物理因素造成的损失之间的新平衡。我认为，即使在受精后的前3天（第299-301天），食草动物继续保持这种近海浮游植物的控制，尽管光合作用和细胞分裂的速率增加。此外，在此期间食物网对碳的矿化有助于解释铁富集对CO2系统的小影响。在IRONEX期间没有测量放牧损失，在这里计算施肥后前3天的20米以上的放牧损失，使用光合作用的估计（从当地中午1小时内开始的24小时内的14 C吸收;参考文献1的图3）和浮游植物生物量的变化（从显微镜：K. Buck，KJ Coale和SJ坦纳）。添加到富铁水中的惰性示踪剂SF6'的浓度接近恒定（表中第6栏;数值由AJ沃森提供），表明浮游植物因物理稀释而损失的量可以忽略不计。此外，占主导地位的小小区1的下沉可以被忽略。
SIR-The iron fertilization experiment in the sea near the Galapagos Islands in mid-October 1993 (IRONEX) 1 showed that the cell division rate of unenclosed phytoplankton, initially high, was quickly enhanced by Fe addition, as had been found in bottle experiments in other high nutrient (nitrate)-low chlorophyll regions. However, the increase of phytoplankton concentration during the days after the IRONEX experiment was not merely an issue of cell physiology2, but was a system response resulting in a new balance between cell division rate and losses from grazing and physical factors. I suggest that even for the first 3 days after fertilization (days 299-301) the grazers continued to keep this offshore phytoplankton in check despite the increase in the rates of photosynthesis and cell division. In addition, the remineralization of carbon by the food web during this time helps to explain the small effect of the iron enrichment on the CO2 system3. The grazing loss, not measured during IRONEX, is calculated here for the upper-20 m during the first 3 days after fertilization, using estimates of photosynthesis (from 14C uptake over 24 h starting within 1 h of local noon; Fig. 3 of ref. 1) and change of phytoplankton biomass (from microscopy: C values kindly supplied by K. Buck, KJ Coale and SJ Tanner). The near-constant concentrations of the inert tracer SF6'added to the Fe-enriched water (column 6 of table; values kindly provided by AJ Watson), show that losses of phytoplankton from physical dilution were negligible. Also, sinking of the dominant small cells1 can be discounted.