To clarify horizontal variability and regulation of bacterial production (BP), we investigated BP and environmental variables along three east–west transects (lines 12, 15, and 17) covering inshore/offshore stations in Lake Biwa, Japan, during four seasons using ¹⁵N-labeled deoxyadenosine for measuring BP. In winter, surface BP along Line 12 (southern transect) was higher than Lines 15 and 17 (central and northern transects) and reflected the water-temperature distribution. Additionally, any nutrients and dissolved organic carbon did not correlate to BP, suggesting water temperature primarily regulated BP in winter. In spring, surface BP was higher at eastern inshore stations, near large agricultural fields, and was correlated with nutrient concentrations rather than water temperature, suggesting that the limitation shifted to nutrient availability. In summer, surface BP at offshore stations along Lines 15 and 17 was notably lower than the other stations, and the horizontal heterogeneity became largest (maximum to minimum BP ratio = 9.5, compared to 2.8 ~ 4.1 in the other seasons). The BP was also positively correlated to nutrient concentrations, especially phosphorus. Surface BP in autumn also showed higher values at eastern stations as well as spring and positively correlated to phosphorus concentration. Additionally, there was a negative relationship between BP and water temperature, suggesting that bacterial growth was enhanced by groundwater seepage at the eastern stations. The results suggest that the horizontal distribution is characterized by a north–south distribution with a temperature gradient in winter, and allochthonous nutrient loading determines horizontal BP variations in the other seasons in this lake.

为了阐明细菌生产 (BP) 的水平变化和调控，我们使用¹⁵用于测量血压的 N 标记脱氧腺苷。冬季，沿12线（南部样线）的地表BP高于15线和17线（中部和北部样线），反映了水温分布。此外，任何营养物质和溶解的有机碳与 BP 无关，表明水温在冬季主要调节 BP。在春季，靠近大农田的东部近海站的地表 BP 较高，并且与养分浓度而非水温相关，这表明限制转移到养分可用性上。夏季，15、17号线近海站地表BP明显低于其他站，水平非均质性最大（最大最小BP=9.5，其他季节为2.8~4.1）。BP 也与养分浓度呈正相关，尤其是磷。秋季地面BP在东部站点和春季也显示出较高的值，并且与磷浓度呈正相关。此外，BP与水温之间存在负相关关系，表明东部站点地下水渗漏促进了细菌生长。结果表明，该湖的水平分布以冬季温度梯度的南北分布为特征，外来养分负荷决定了该湖其他季节的水平BP变化。此外，BP与水温之间存在负相关关系，表明东部站点地下水渗漏促进了细菌生长。结果表明，该湖的水平分布以冬季温度梯度的南北分布为特征，外来养分负荷决定了该湖其他季节的水平BP变化。此外，BP与水温之间存在负相关关系，表明东部站点地下水渗漏促进了细菌生长。结果表明，该湖的水平分布以冬季温度梯度的南北分布为特征，外来养分负荷决定了该湖其他季节的水平BP变化。