Department of Plant and Environmental Sciences, Edmond J. Safra Campus, Givat Ram, Hebrew University of Jerusalem, Jerusalem 91904, Israel Yigal Allon Kinneret Limnological Laboratory, Israel Oceanographic and Limnological Research, PO Box 447, Migdal 14950, Israel.
Environ Microbiol Rep. 2012 Oct;4(5):498-503. doi: 10.1111/j.1758-2229.2012.00351.x. Epub 2012 May 7.
The reasons for large multiannual fluctuations in phytoplankton biomass and composition in freshwater lakes are complex and involve many biotic and abiotic parameters. Here we studied the 2009 and 2010 summer-autumn blooms of the toxic, cylindrospermopsin producer, Aphanizomenon ovalisporum (hereafter Aphanizomenon) in Lake Kinneret (Sea of Galilee), Israel. During the summer the total dissolved phosphate concentration in the lake is very low, close to the detection level, limiting the development of phytoplankton. Earlier we showed that Aphanizomenon blooms are associated with a large rise in alkaline phosphatase (Apase) activity in the water body and that cylindrospermopsin produced by Aphanizomenon induces the PHO regulon, including secretion of Apase, in other alga thereby improving its own phosphate supply. Aphanizomenon transcripts of PHO and AOA (involved in cylindrospermopsin biosynthesis) genes in Lake Kinneret appeared much earlier in 2010 than in 2009 suggesting that the phytoplankton became phosphate-limited already at the beginning of its summer bloom in 2010 but much later in 2009. Water inflow and lake water temperatures were significantly higher in 2010 but the incoming nutrients were consumed by the much larger phytoplankton biomass early in 2010 before the beginning of the Aphanizomenon bloom. An analysis of abiotic and biological parameters provides an explanation for the very different development of Aphanizomenon populations during 2009 and 2010.
淡水湖中浮游植物生物量和组成的大多年际波动的原因很复杂，涉及许多生物和非生物参数。在这里，我们研究了 2009 年和 2010 年夏季-秋季以色列加利利海（Kinneret 湖）有毒、产环脒藻毒素的鱼腥藻（Aphanizomenon ovalisporum）的水华。在夏季，湖中总溶解磷酸盐浓度非常低，接近检测水平，限制了浮游植物的发展。我们之前曾表明，鱼腥藻水华与水体中碱性磷酸酶（Apase）活性的大幅上升有关，鱼腥藻产生的环脒藻毒素诱导 PHO 调控子，包括 Apase 的分泌，从而改善其自身的磷供应。与鱼腥藻生物合成有关的 PHO 和 AOA（碱性磷酸酶）基因的转录物在 2010 年比 2009 年更早出现在 Kinneret 湖中，这表明浮游植物在 2010 年夏季水华开始时已经受到磷限制，但在 2009 年时受到磷限制的时间要晚得多。2010 年的入流水和湖水温度明显升高，但在鱼腥藻水华开始之前，更多的浮游植物生物量在 2010 年初就消耗了进入的养分。对非生物和生物参数的分析为 2009 年和 2010 年鱼腥藻种群的发展提供了一个解释。
