Chlorophyll measurements are commonly used to estimate phytoplankton biomass. However, phytoplankton readily acclimate to variations in light through a range of phenotypic responses, including major adjustments in chlorophyll pigmentation at the cellular level. The ratio of pigment chlorophyll to carbon concentration (Chl:C) is a commonly used metric in the oceanographic community to explore photoacclimation responses to varied light levels, yet is relatively rare in freshwater studies. Here we explore how nutrient variability impacted summertime Chl:C ratios of a natural phytoplankton community throughout the water column of a stratified oligotrophic lake. We utilized both long-term (18–24 years) and high-frequency (daily) data from Crater Lake, Oregon, a deep mountain lake with little anthropogenic disturbance. As expected, fluctuation in nutrients had a strong impact on phytoplankton particle density, primary productivity, light penetration, and water clarity. However, chlorophyll concentration did not register predictable changes even though the vertical location of the deep chlorophyll maximum was responsive to the overlying algal density. The impact of elevated nutrients on the Chl:C ratio was further complicated by upward shifts in chlorophyll distribution. The muted response of chlorophyll concentration to nutrients may be partially explained by variations in phytoplankton community composition or iron stress.

中文翻译：

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用长期和高频数据测量的营养物对贫营养湖泊中浮游植物光驯化的影响：对叶绿素作为浮游植物生物量估计的影响

叶绿素测量通常用于估计浮游植物生物量。然而，浮游植物很容易通过一系列表型反应来适应光线的变化，包括细胞水平上叶绿素色素沉着的主要调整。色素叶绿素与碳浓度的比率 (Chl:C) 是海洋学界常用的指标，用于探索对不同光照水平的光适应反应，但在淡水研究中相对较少。在这里，我们探讨了营养变异如何影响整个分层贫营养湖水柱中天然浮游植物群落的夏季 Chl:C 比率。我们利用了来自俄勒冈州火山口湖的长期（18-24 年）和高频（每日）数据，这是一个几乎没有人为干扰的深山湖泊。正如预期的那样，营养物质的波动对浮游植物颗粒密度、初级生产力、透光率和水透明度有很大影响。然而，即使深叶绿素最大值的垂直位置对上覆藻类密度有反应，叶绿素浓度也没有出现可预测的变化。叶绿素分布的向上变化使营养物质升高对 Chl:C 比率的影响进一步复杂化。叶绿素浓度对营养物质的反应平缓，部分原因可能是浮游植物群落组成或铁胁迫的变化。即使深层叶绿素最大值的垂直位置对上覆藻类密度有反应，叶绿素浓度也没有出现可预测的变化。叶绿素分布的向上变化使营养物质升高对 Chl:C 比率的影响进一步复杂化。叶绿素浓度对营养物质的反应平缓，部分原因可能是浮游植物群落组成或铁胁迫的变化。即使深层叶绿素最大值的垂直位置对上覆藻类密度有反应，叶绿素浓度也没有出现可预测的变化。叶绿素分布的向上变化使营养物质升高对 Chl:C 比率的影响进一步复杂化。叶绿素浓度对营养物质的反应平缓，部分原因可能是浮游植物群落组成或铁胁迫的变化。