In recent decades, the freshwater alga Gonyostomum semen (Ehrenberg) Diesing has increased in abundance and distribution, which has created problems regarding the use of lakes for drinking water and recreation. Increases in lake dissolved organic carbon (DOC; browning) and climate warming are among current hypotheses that explain the phenomenon of in creased abundance of G. semen. A replicated, multifactorial laboratory experiment was performed in order to test the effects of DOC and light quality and irradiance on growth of G. semen in 96-well plates. Each well had a separate light source, creating a gradient of irradiance (10− 140 μmol photons m−2 s−1) and wavelength (white, red, green and blue), combined with a DOC gradient (0−50 mg C l−1), all within representative ranges for the summer epilimnion in boreal waters. The experiment showed that growth of G. semen was significantly enhanced by the addition of DOC. No growth response relating to wavelengths was found, but where irradiance was inhibitory, a shading effect from DOC was evident. A composed response to increases in DOC suggests a versatility of G. semen that gives it a competitive advantage over other phytoplankton in humic lake ecosystems. Hence, further increases in abundance and bloom frequency of G. semen as browning continues in boreal lakes are to be expected.

中文翻译：

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有害藻类 Gonyostomum semen ((Ehrenberg) Diesing, Raphidophyceae) 对 DOC 的生长反应以及相关的光质和数量改变

近几十年来，淡水藻类 Gonyostomum semen (Ehrenberg) Diesing 的数量和分布都在增加，这对利用湖泊进行饮用水和娱乐造成了问题。湖泊溶解有机碳（DOC；褐变）的增加和气候变暖是目前可以解释 G. 精液丰度增加现象的假设之一。进行了重复的多因素实验室实验，以测试 DOC 和光质量和辐照度对 96 孔板中 G. 精液生长的影响。每个孔都有一个单独的光源，产生一个梯度的辐照度（10-140 μmol 光子 m-2 s-1）和波长（白色、红色、绿色和蓝色），结合 DOC 梯度（0-50 mg C l −1)，均在北方水域夏季飞沫的代表性范围内。实验表明，加入DOC显着促进了G. semen的生长。没有发现与波长相关的生长响应，但在辐照度受到抑制的情况下，DOC 的遮蔽效果很明显。对 DOC 增加的综合反应表明 G. semen 的多功能性使其比腐殖质湖生态系统中的其他浮游植物更具竞争优势。因此，随着北方湖泊继续褐变，G. 精液的丰度和开花频率将进一步增加。使其比腐殖质湖生态系统中的其他浮游植物更具竞争优势的精液。因此，随着北方湖泊继续褐变，G. 精液的丰度和开花频率将进一步增加。使其比腐殖质湖生态系统中的其他浮游植物更具竞争优势的精液。因此，随着北方湖泊继续褐变，G. 精液的丰度和开花频率将进一步增加。