Decrease in bacterial production over the past three decades in the north basin of Lake Biwa, Japan
Decrease in bacterial production over the past three decades in the north basin of Lake Biwa, Japan
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过去三十年日本琵琶湖北部盆地细菌产量减少
DOI：
10.1007/s10201-019-00582-2
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发表时间：
2019
期刊：
影响因子：
1.6
通讯作者：
Hirose Yoshinori
中科院分区：
文献类型：
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作者：
Tsuchiya Kenji;Tomioka Noriko;Sano Tomoharu;Kohzu Ayato;Komatsu Kazuhiro;Imai Akio;Hayakawa Kazuhide;Nagata Takamaru;Okamoto Takahiro;Hirose Yoshinori
在日本最大的湖泊琵琶湖，自20世纪80年代以来，外部污染物负荷减少，导致水质改善，如生化需氧量(BOD)和PO43−浓度下降。我们研究了2016-2017年间琵琶湖北部盆地在这些环境变化下细菌产量(BP)的长期变化。BP是通过测量2016年6月和2017年12月稳定同位素15N标记的脱氧腺苷(15N-da)的掺入量，并与1986年和1997-1998年的测量结果进行比较来估计的。1986年用~3H标记胸腺嘧啶核苷(~3H-TdR)掺入法测定血压，1997年~1998年通过跟踪培养细菌丰度和计算比生长率(μ)来测量血压。为了能够直接比较15N-da和~3H-TdR参入率，我们确定了一个转换因子。为了估计2016-2017年的μ，我们确定了一个将15N-da掺入转化为细胞数量增加的因子。2016年~2017年，~(15)N-da参入率为0.13~30.7pmoL L−1h−~1，μ为0.016~0.70d−~1。1986年~1997年~1998年~1998年~1997年~1998年的~3H-TdR参入率的BP分别是2016年~2017年BP的4.6倍和2.1倍，证实了琵琶湖30年来BP的下降趋势。水质数据显示，自20世纪80年代以来，BOD和总磷浓度的降幅很低，而PO43−浓度的降幅与BP的降幅相当。琵琶湖BP和有机质的分解受磷的强烈限制。我们的结果表明，血压的下降可以通过生物可利用型PO43−的减少来解释。在PO43−浓度(NM)很低的条件下，有机磷也是BP的重要磷源，有机磷生物有效性的变化也可能调节BP的动态变化。
In Lake Biwa, the largest lake in Japan, external pollutant loads have decreased since the 1980s, leading to improved water quality, such as reduction in biochemical oxygen demand (BOD) and PO43−concentrations. We examined long-term variation of bacterial production (BP) under these environmental changes from 2016–2017 in the north basin of Lake Biwa. BP was estimated by measuring the incorporation of stable isotope15N-labeled deoxyadenosine (15N-dA) from June 2016 and December 2017 and compared with measurements from 1986 and 1997–1998. In 1986, BP was measured by following3H-labeled thymidine (3H-TdR) incorporation and in 1997–1998 by tracking bacterial abundance in incubations and calculating specific growth rates (μ). To allow direct comparison of15N-dA and3H-TdR incorporation rates, we determined a conversion factor. To estimateμin 2016–2017, we determined a factor for converting15N-dA incorporation to cell number increase. In 2016–2017, the15N-dA incorporation rate ranged from 0.13 to 30.7 pmol l−1h−1andμranged from 0.016 to 0.70 day−1. BP values from3H-TdR incorporation rates in 1986 andμin 1997–1998 were 4.6 and 2.1 times BP values in 2016–2017, respectively, confirming the decrease in BP over the past 3 decades in Lake Biwa. Water quality data showed only low decrease rates for BOD and total phosphorus concentration from the 1980s, whereas the rate of decrease for PO43−concentrations was equivalent to that of BP. BP and decomposition of organic matter are known to be strongly P-limited in Lake Biwa. Our results suggest that the decrease in BP can be explained by a reduction in readily bioavailable PO43−. Organic phosphorus can also be an important P-source for BP under conditions with very low PO43−concentrations (nM), and changes in the bioavailability of organic phosphorus might have also regulated BP dynamics.