NITROGEN LIMITATION INCREASES BREVETOXINS IN KARENIA BREVIS (DINOPHYCEAE): IMPLICATIONS FOR BLOOM TOXICITY
NITROGEN LIMITATION INCREASES BREVETOXINS IN KARENIA BREVIS (DINOPHYCEAE): IMPLICATIONS FOR BLOOM TOXICITY
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DOI：
10.1111/j.1529-8817.2012.01186.x
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发表时间：
2012-08-01
影响因子：
2.9
通讯作者：
Tester, Patricia A.
中科院分区：
文献类型：
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作者：
Hardison, D. Ransom;Sunda, William G.;Tester, Patricia A.
在实验室和现场测量短凯伦藻细胞中的毒素含量相差>4倍。这些差异在很大程度上归因于菌株间毒素产生的基因型变异。我们推测，生长速率的营养限制在控制钾的毒性方面同样重要或更重要。brevis，正如其他有毒藻类所记录的那样。为了验证这一假设，我们测量了四个菌株的细胞生长速率，叶绿素a，细胞碳和氮，细胞体积和短毒素。在营养充足和氮（N）有限的半连续培养中生长。氮限制导致叶绿素a、生长速率、每个细胞的体积和氮：碳（N：C）比的降低以及以短毒素形式存在的细胞碳的百分比的两倍增加（1%4%至5%9%）。在遗传上不同的菌株中，细胞短尾孢毒素浓度的增加是一致的。将短杆菌毒素标准化为细胞体积而不是每个细胞消除了菌株之间通常报告的毒素变异性。这些结果表明，遗传连锁的细胞体积的差异可能会影响毒素含量的K。短细胞一样多或更多的先天基因型差异的细胞毒素含量每单位生物量。我们的数据表明，田间研究报告的每个细胞毒性的>4倍差异中的至少一些可以通过氮或其他营养素的限制以及细胞大小的差异来解释。在氮限制细胞中观察到的短毒素的增加与碳：营养平衡假说的毒素和营养限制下的其他植物防御的增加是一致的。
Laboratory and field measurements of the toxin content in Karenia brevis cells vary by >4-fold. These differences have been largely attributed to genotypic variations in toxin production among strains. We hypothesized that nutrient limitation of growth rate is equally or more important in controlling the toxicity of K. brevis, as has been documented for other toxic algae. To test this hypothesis, we measured cellular growth rate, chlorophyll a, cellular carbon and nitrogen, cell volume, and brevetoxins in four strains of K. brevis grown in nutrient-replete and nitrogen (N)-limited semi-continuous cultures. N-limitation resulted in reductions of chlorophyll a, growth rate, volume per cell and nirtogen:carbon (N:C) ratios as well as a two-fold increase (1%4% to 5%9%) in the percentage of cellular carbon present as brevetoxins. The increase in cellular brevetoxin concentrations was consistent among genetically distinct strains. Normalizing brevetoxins to cellular volume instead of per cell eliminated much of the commonly reported toxin variability among strains. These results suggest that genetically linked differences in cellular volume may affect the toxin content of K. brevis cells as much or more than innate genotypic differences in cellular toxin content per unit of biomass. Our data suggest at least some of the >4-fold difference in toxicity per cell reported from field studies can be explained by limitation by nitrogen or other nutrients and by differences in cell size. The observed increase in brevetoxins in nitrogen limited cells is consistent with the carbon:nutrient balance hypothesis for increases in toxins and other plant defenses under nutrient limitation.