Graduate School of Environmental Science, Hokkaido University, N10 W5, Sapporo, Hokkaido, 060-0810, Japan.
Faculty of Environmental Earth Science, Hokkaido University, N10 W5, Sapporo, Hokkaido, 060-0810, Japan.
Environ Pollut. 2024 Dec 15;363(Pt 1):125101. doi: 10.1016/j.envpol.2024.125101. Epub 2024 Oct 10.
This study reports the effect of spatial variation in hyporheic water, partially influenced by urban-polluted groundwater, on the early life stage of chum salmon (Oncorhynchus keta) in the Toyohira River, Northern Japan. We hypothesized that increased groundwater influence would reduce the survival rate and body size of O. keta due to the combined effects (i.e., growth retardation effects) of chemical toxicants, low dissolved oxygen (DO), and high winter temperatures. Experimental tests were conducted in field and laboratory conditions to address the difficulties associated with field observations of fry emergence during snowmelt floods in spring and to examine the independent effects of water pollution in groundwater in relation to temperature and DO. Artificially fertilized eyed eggs, alevins, and fry of O. keta were monitored for several months with varying exposure to groundwater from winter to early spring. We noted that groundwater affected the fish by reducing their size and weight by >10% and by increasing their mortality in both tests. Moreover, independent effects of water pollution were identified in the swim-up fry stage in laboratory experiments, along with growth-retarding effects from warmer groundwater temperatures. Not all factorial combinations of potentially confounding factors were tested rigorously, and the specific toxicants are unidentified, leaving questions about how groundwater pollution affects Salmonidae fish. Immediate concerns regarding the current water quality (including DO) of hyporheic water associated with groundwater influence are low because no detrimental effects on survival were detected in the field. Nevertheless, spawning grounds formed in areas with high exposures to polluted groundwater require continuous management attention due to potential risks associated with low DO levels. Additionally, pollution-induced growth patterns could pose a risk of size- or weight-dependent mortality at the swim-up fry stage and in early juveniles.
本研究报告了受城市污染地下水部分影响的渗流区水的空间变化对日本北部豊平河樱鳟（Oncorhynchus keta）早期生命阶段的影响。我们假设，由于化学毒物、低溶解氧 (DO) 和冬季高温的综合影响（即生长迟缓效应），地下水影响的增加会降低 O. keta 的存活率和体型。实验测试在野外和实验室条件下进行，以解决春季融雪洪水期间幼鱼孵化的野外观察困难，并研究与温度和 DO 相关的地下水污染的独立影响。O. keta 的人工受精卵、仔鱼和幼鱼在冬季到早春期间受到不同程度的地下水暴露，进行了数月的监测。我们注意到，地下水通过降低鱼的大小和体重超过 10%，并增加其在两个测试中的死亡率，从而影响鱼类。此外，在实验室实验的游泳幼鱼阶段还确定了水污染的独立影响，以及来自较暖地下水温度的生长迟缓效应。并非所有潜在混杂因素的组合都进行了严格测试，并且特定的毒物尚未确定，这使得地下水污染如何影响鲑科鱼类的问题仍然存在疑问。由于在野外没有检测到对生存有不利影响，因此当前与地下水影响相关的渗流区水的水质（包括 DO）的直接担忧较低。然而，由于与低 DO 水平相关的潜在风险，需要对暴露于高污染地下水中形成的产卵场进行持续管理。此外，污染诱导的生长模式可能会在游泳幼鱼阶段和早期幼鱼阶段造成大小或体重依赖的死亡率风险。
