Dilution of the water chemistry caused by reduced acidification has lately received increased attention, both in Europe and North America. There has also been a declining trend in the supply of sea salts. Several studies have predicted detrimental effects on aquatic life due to dilution. A population of brook trout living in River Hunnedal in southwestern Norway was studied for 14 years (2006–2019). Despite acceptable water chemistry with respect to pH and inorganic Al, limited reproduction was found. With median conductivity, Ca and Na of 7.1–8.6 μScm⁻¹, and 0.17–0.19 and 0.9–1.0 mgL⁻¹, respectively, the water at the study sites was found to be extremely dilute. We detected a significant positive effect of Na on the densities of brook trout fry, while a less distinct effect of Ca was found. However, due to the correlation between Ca and Na we cannot conclude that Ca is unimportant. For all samplings without catch of fry (n = 13), Na was 0.86 ± 0.15 mgL⁻¹, suggesting a critical limit for Na slightly below 1 mgL⁻¹. We suggest that the reproduction of brook trout was restricted by the highly dilute water and the subsequent scarcity of essential ions.

近年来，在欧洲和北美，由于酸化减少而引起的水化学稀释受到越来越多的关注。海盐的供应也有下降的趋势。几项研究预测了由于稀释而对水生生物的有害影响。研究了居住在挪威西南部洪内达尔河上的河鳟的种群，为期14年（2006-2019年）。尽管就pH和无机Al而言，水化学可接受，但发现复制有限。在电导率中值下，Ca和Na为7.1–8.6μScm- ¹，分别为0.17–0.19和0.9–1.0 mgL ^-1分别发现研究地点的水非常稀。我们发现Na对鳟鱼鱼苗的密度具有显着的正作用，而Ca的作用却不太明显。但是，由于Ca和Na之间的相关性，我们不能得出Ca不重要的结论。对于所有没有捕获到鱼苗的采样（n  = 13），Na为0.86±0.15 mgL ^-1，这表明Na的临界限值略低于1 mgL ^-1。我们认为，河鳟的繁殖受到高度稀释的水和随后必需离子缺乏的限制。