Galloway Aaron W E, Winder Monika
John Muir Institute of the Environment, Watershed Science Center, University of California Davis, Davis, California, United States of America.
John Muir Institute of the Environment, Watershed Science Center, University of California Davis, Davis, California, United States of America; Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
PLoS One. 2015 Jun 15;10(6):e0130053. doi: 10.1371/journal.pone.0130053. eCollection 2015.
Essential fatty acids (EFA), which are primarily generated by phytoplankton, limit growth and reproduction in diverse heterotrophs. The biochemical composition of phytoplankton is well-known to be governed both by phylogeny and environmental conditions. Nutrients, light, salinity, and temperature all affect both phytoplankton growth and fatty acid composition. However, the relative importance of taxonomy and environment on algal fatty acid content has yet to be comparatively quantified, thus inhibiting predictions of changes to phytoplankton food quality in response to global environmental change. We compiled 1145 published marine and freshwater phytoplankton fatty acid profiles, consisting of 208 species from six major taxonomic groups, cultured in a wide range of environmental conditions, and used a multivariate distance-based linear model to quantify the total variation explained by each variable. Our results show that taxonomic group accounts for 3-4 times more variation in phytoplankton fatty acids than the most important growth condition variables. The results underscore that environmental conditions clearly affect phytoplankton fatty acid profiles, but also show that conditions account for relatively low variation compared to phylogeny. This suggests that the underlying mechanism determining basal food quality in aquatic habitats is primarily phytoplankton community composition, and allows for prediction of environmental-scale EFA dynamics based on phytoplankton community data. We used the compiled dataset to calculate seasonal dynamics of long-chain EFA (LCEFA; ≥C20 ɷ-3 and ɷ-6 polyunsaturated fatty acid) concentrations and ɷ-3:ɷ-6 EFA ratios in Lake Washington using a multi-decadal phytoplankton community time series. These analyses quantify temporal dynamics of algal-derived LCEFA and food quality in a freshwater ecosystem that has undergone large community changes as a result of shifting resource management practices, highlighting diatoms, cryptophytes and dinoflagellates as key sources of LCEFA. Moreover, the analyses indicate that future shifts towards cyanobacteria-dominated communities will result in lower LCEFA content in aquatic ecosystems.
必需脂肪酸（EFA）主要由浮游植物产生，会限制多种异养生物的生长和繁殖。众所周知，浮游植物的生化组成受系统发育和环境条件的共同影响。营养物质、光照、盐度和温度都会影响浮游植物的生长以及脂肪酸组成。然而，分类学和环境对藻类脂肪酸含量的相对重要性尚未得到比较量化，因此阻碍了对浮游植物食物质量因全球环境变化而产生的变化的预测。我们汇编了1145个已发表的海洋和淡水浮游植物脂肪酸谱，这些谱来自六个主要分类组的208个物种，在广泛的环境条件下培养，并使用基于多变量距离的线性模型来量化每个变量所解释的总变异。我们的结果表明，分类组对浮游植物脂肪酸变异的解释比最重要的生长条件变量多3至4倍。结果强调环境条件显然会影响浮游植物脂肪酸谱，但也表明与系统发育相比，环境条件所导致的变异相对较低。这表明决定水生栖息地基础食物质量的潜在机制主要是浮游植物群落组成，并允许根据浮游植物群落数据预测环境尺度上的必需脂肪酸动态。我们使用汇编的数据集，通过一个多年代的浮游植物群落时间序列，计算了华盛顿湖长链必需脂肪酸（LCEFA；≥C20 ω-3和ω-6多不饱和脂肪酸）浓度和ω-3:ω-6必需脂肪酸比率的季节动态。这些分析量化了一个淡水生态系统中藻类衍生的长链必需脂肪酸和食物质量的时间动态，该生态系统由于资源管理实践的转变而经历了巨大的群落变化，突出了硅藻、隐藻和甲藻是长链必需脂肪酸的关键来源。此外，分析表明未来向以蓝藻为主的群落的转变将导致水生生态系统中长链必需脂肪酸含量降低。
