Decrease in molecular weight of photosynthetic products of marine phytoplankton during early diagenesis
Decrease in molecular weight of photosynthetic products of marine phytoplankton during early diagenesis
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DOI：
10.4319/lo.2004.49.2.0471
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发表时间：
2004-03
影响因子：
4.5
通讯作者：
T. Hama;K. Yanagi;J. Hama
中科院分区：
文献类型：
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作者：
T. Hama;K. Yanagi;J. Hama
利用~（13）C作为示踪剂，研究了成岩早期浮游植物光合产物的大小和中性醛糖（NAld）组成的变化。大部分（94.7%）的光合作用产生的（P-）有机碳（OC）被发现是颗粒有机碳（POC）后，12小时的光温育。转移至黑暗孵育后，发现P-溶解有机碳（DOC）浓度增加，可能是由于细胞成分泄漏。P-DOC浓度的增加主要是由于高分子量（HMW：≤ 10 kDa）组分的增加，其在第3天达到最大浓度，然后以相对较高的速率下降。低分子量（LMW：≤ 10 kDa）DOC组分的浓度变化不如HMW组分显著，且降低速率慢得多，表明P-LMW DOC的生物抗性更强。光照孵育12小时后，P-溶解碳水化合物（DCHO）分别占P-HMW DOC和P-LMW DOC的38%和50%。P-LMW DCHO的浓度在黑暗孵育的早期阶段迅速降低，而同时观察到P-LMW溶解非碳水化合物（DnonCHO）的浓度增加。在P-POC和P-HMW DOC组分中均观察到CHO贡献的降低，但下降速率慢于P-LMW DOC组分。在第60天，剩余的P-OC占最初产生的光合物质的4.6%。第60天剩余P-OC的粒度分布（POC，14%; HMW DOC，22%; LMW DOC，64%）表明，在早期成岩作用期间，浮游植物光合产物迅速降解为生物活性较低的LMW DOM。目前的研究结果表明，全球海洋中半不稳定DOC的年生产率为1.91 PgC yr-1，寿命超过2个月。
Changes in the size and neutral aldose (NAld) composition of phytoplankton photosynthetic products during the early diagenetic process were experimentally examined using 13C as a tracer. Most (94.7%) of the photosynthetically produced (P−) organic carbon (OC) was found to be particulate organic carbon (POC) after a 12‐h light incubation. An increase in the concentration of P‐dissolved organic carbon (DOC) was found after the shift to the dark incubation, probably due to a leakage of cellular constituents. An increase in the concentration of P‐DOC was mainly due to an increase in the high molecular weight (HMW: ≫10 kDa) fraction that reached its maximum concentration on day 3 and then declined at a relatively high rate. The change in the concentration of the low molecular weight (LMW: ≪10 kDa) DOC fraction was less marked than that in the HMW fraction, and the rate of decrease was much slower, indicating a more biorefractory nature of P‐LMW DOC. P‐dissolved carbohydrates (DCHO) accounted for 38% and 50% in P‐HMW DOC and P‐LMW DOC, respectively, after a 12‐h light incubation. The concentration of P‐LMW DCHO showed a rapid decrease in the early stage of the dark incubation, whereas the concomitant increase in the concentration of P‐LMW dissolved noncarbohydrate (DnonCHO) was noticed. The decrease in the contribution of CHO was noticed both in P‐POC and P‐HMW DOC fractions, but the decline rates were slower than that in P‐LMW DOC fraction. On day 60, the remaining P‐OC accounted for 4.6% of photosynthetic material originally produced. The distribution of the size fractions of the remaining P‐OC on day 60 (POC, 14%; HMW DOC, 22%; LMW DOC, 64%) indicates that phytoplankton photosynthetic products were rapidly degraded to the less bioreactive LMW DOM during early diagenesis. The present results indicate that the annual global ocean production rate of semilabile DOC with lifetimes exceeding 2 months is 1.91 PgC yr−1.