Effects of physical fragmentation on remineralization of marine snow
Effects of physical fragmentation on remineralization of marine snow
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DOI：
10.3354/meps305059
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发表时间：
2005-01-01
影响因子：
2.5
通讯作者：
Alldredge, AL
中科院分区：
文献类型：
--
作者：
Goldthwait, SA;Carlson, CA;Alldredge, AL
海洋表面水域损失的绝大多数碳以相对稀有的大块海洋雪和粪便颗粒的形式下沉。先前已提出将这些颗粒破碎成更缓慢下沉的子颗粒，以部分解释混合层下方下沉碳的快速损失。在这项研究中，我们研究了聚集体破坏的其他 2 个不太明显的潜在后果，即破碎时溶解的间隙化合物的释放以及由于颗粒表面积增加而加速降解。我们发现，直径为 3 至 6 毫米的天然海洋聚集体破碎后，会向周围海水中释放溶解的有机碳 (DOC)（平均 0.12 μ mol 聚集体 (-1)）和硝酸盐（平均 0.013 μ mol 聚集体 (-1)），使这些营养物质可供自由生活的生物群利用。整个骨料的过滤未能产生同等的释放量，这表明由于骨料孔隙率较高，海洋雪可能不会像预期的那样渗漏。对于0.6至0.9μmol POC聚集体(-1) d(-1)的整个聚集体和碎片聚集体，聚集体颗粒有机碳(POC)向DOC的分解相似，计算得出的聚集体POC周转时间为2至11天。两种聚集体处理中 DOC 的再矿化也相似，表明溶解和附着细菌吸收之间存在紧密耦合。我们的结果表明，预测混合层中较小聚集体的较长停留时间，而不是分解速率的变化，可能是聚集体破碎对深度颗粒通量减少的最有影响力的影响。
The vast majority of carbon lost from ocean surface waters sinks as large, relatively rare, marine snow and fecal pellets. Fragmentation of these particles into more slowly sinking daughter particles has been proposed previously to partly explain the rapid loss of sinking carbon below the mixed layer. In this study we investigated 2 other less obvious potential consequences of aggregate disruption, namely the release of dissolved interstitial compounds upon fragmentation and accelerated degradation due to increased particle surface area. We found that upon fragmentation natural marine aggregates, ranging in size from 3 to 6 mm diameter, released dissolved organic carbon (DOC) (mean 0.12 mu mol aggregate(-1)) and nitrate (mean of 0.013 mu mol aggregate(-1)) into surrounding seawater, making these nutrients available to free-living biota. Filtration of whole aggregates failed to result in an equivalent release, suggesting that marine snow may not be as leaky as expected based on high aggregate porosity. Decomposition of aggregate particulate organic carbon (POC) to DOC was similar for whole and fragmented aggregates ranging from 0.6 to 0.9 mu mol POC aggregate(-1) d(-1), resulting in calculated aggregate POC turnover times of 2 to 11 d. Remineralization of DOC was also similar for both aggregate treatments and suggested a tight coupling between solubilization and uptake by attached bacteria. Our results indicate that the longer residence times predicted for smaller aggregates in the mixed layer, rather than changes in decomposition rate, may be the most influential impact of aggregate fragmentation on reduction of particle flux to depth.