Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou 510632, China.
Water Res. 2013 Jul 1;47(11):3610-23. doi: 10.1016/j.watres.2013.04.014. Epub 2013 Apr 22.
We studied seasonal variations in the carbon and nitrogen stable isotopes (δ(13)C and δ(15)N) of particulate organic matter (POM) in the surface water of 20 man-made reservoirs in southern China during March, August and December 2010. These reservoirs are located from subtropical to tropical region, varied in trophic states and were influenced by several types of human activities. The geomorphometric and biogeochemical gradients in tropical/subtropical regions are complicated and poorly understood because of low variation in temperature and high variation in hydrological processes. The POM samples were collected from all the reservoirs to assess the seasonal variation patterns of δ(13)CPOM and δ(15)NPOM. Variation in δ(13)CPOM followed seasonal thermal and hydrological cycles. By contrast, δ(15)NPOM did not seasonally differ, which may have been complicated by phytoplankton assimilation of N originating in agricultural waste entering the reservoirs and of atmospheric nitrogen during the wet season as well as an increased relative contribution of animal waste in the reservoirs in the dry season. Within each sampling period, nutrient availability is more important than thermal and solar radiation inputs in the summer, and these physical drivers are more important during the dry and cold winter month in controlling δ(13)CPOM and δ(15)NPOM. On an annual basis, trophic states (total P, total N and chlorophyll a) are the primary drivers for the changes in both δ(13)CPOM and δ(15)NPOM across reservoirs. When the seasonal effect is removed using annual averages from each reservoir, we found that latitude, trophic states, pH, rainfall, water temperature, reservoir age, catchment area to reservoir area (CA:RA) ratio and together explained about 80% of the variance in both δ(13)CPOM and δ(15)NPOM. Our findings also suggest that the trend of δ(15)NPOM is less predictable than δ(13)CPOM. The consistent (15)N depletion and enrichment of POM in different reservoirs point to the importance of different anthropogenic sources of nitrogen in the reservoirs.
我们研究了 2010 年 3 月、8 月和 12 月期间中国南方 20 个人造水库表层水中颗粒有机物质（POM）的碳和氮稳定同位素（δ（13）C 和 δ（15）N）的季节性变化。这些水库位于亚热带到热带地区，营养状态不同，受到多种类型的人类活动影响。由于温度变化较小而水文过程变化较大，热带/亚热带地区的地貌和生物地球化学梯度复杂且了解甚少。我们从所有水库采集 POM 样本，以评估 δ（13）CPOM 和 δ（15）NPOM 的季节性变化模式。δ（13）CPOM 的变化遵循季节性热和水文循环。相比之下，δ（15）NPOM 没有季节性差异，这可能是由于进入水库的农业废物中氮的生源同化以及雨季大气氮以及旱季水库中动物废物相对贡献增加而变得复杂。在每个采样期内，养分供应比夏季的热和太阳辐射输入更为重要，而在旱冷的冬季月份，这些物理驱动因素对控制 δ（13）CPOM 和 δ（15）NPOM 更为重要。在年度基础上，营养状态（总磷、总氮和叶绿素 a）是控制水库中 δ（13）CPOM 和 δ（15）NPOM 变化的主要驱动因素。从每个水库的年度平均值中去除季节性影响后，我们发现纬度、营养状态、pH 值、降雨量、水温、水库年龄、集水区与水库面积比（CA：RA）以及一起解释了 δ（13）CPOM 和 δ（15）NPOM 变化的 80%左右。我们的研究结果还表明，δ（15）NPOM 的趋势比 δ（13）CPOM 更难预测。不同水库中 POM 的一致（15）N 消耗和富集表明，水库中氮的不同人为来源非常重要。
