Aquatic Sciences ( IF 2.4 ) Pub Date : 2021-02-06 , DOI: 10.1007/s00027-021-00780-0 Oscar E. Senar , Irena F. Creed , Charles G. Trick
Lake browning—the increase in catchment-derived (allochthonous) dissolved organic matter (DOM) to lakes—is altering lake physicochemical environments, with consequences for phytoplankton biomass and community composition. We hypothesized that as lakes brown, there will be an increase in phytoplankton biomass and a shift to cyanobacteria-dominated phytoplankton communities as a result of the reduced light availability and increased DOM-bound nutrients (e.g., nitrogen, phosphorus, iron). We tested this hypothesis by sampling temperate lakes in central Ontario (Canada) spanning DOM quantity and quality gradients. We found that lake browning results in larger concentrations of more refractory (i.e., aromatic, high molecular weight) DOM and greater concentrations of nutrients; however, internal nutrient loading was also an important nutrient source in these lakes. We also found that these changes were related to the predominant species in the phytoplankton community. Diatoms dominated in clear oligotrophic lakes. Low levels of lake browning, with concentrations of dissolved organic carbon (DOC) between 4 and 8 mg L− 1, resulted in a shift from diatoms to cyanobacteria. Higher levels of lake browning, with concentrations of DOC between 8 and 12 mg L− 1, resulted in a replacement of cyanobacteria with mixotrophic species. Lake browning appears to fuel phytoplankton chlorophyll-a concentrations while triggering shifts to phytoplankton able to survive if not thrive in progressively browner waters. Lake browning may therefore have consequences on energy transfer through the lower food web.
中文翻译:
湖泊褐变可能会增加浮游植物的生物量并触发温带湖泊中浮游植物群落的变化
湖泊褐变(流域衍生的(散乱的)溶解有机物(DOM)向湖泊的增加)正在改变湖泊的理化环境,对浮游植物的生物量和群落组成产生影响。我们假设随着湖泊的褐色化,由于光利用率的降低和DOM结合养分(例如氮,磷,铁)的增加,浮游植物的生物量将会增加,并且向蓝藻为主的浮游植物群落转移。我们通过采样横跨DOM数量和质量梯度的安大略省中部(加拿大)的温带湖泊来检验该假设。我们发现,湖水褐变会导致更高浓度的难熔(即芳香族,高分子量)DOM和更高浓度的营养素。然而,内部营养负荷也是这些湖泊中重要的营养来源。我们还发现,这些变化与浮游植物群落中的主要物种有关。硅藻在透明的贫营养湖中占主导地位。湖泊褐变程度低,溶解有机碳(DOC)浓度在4至8 mg L之间− 1,导致从硅藻转变为蓝细菌。DOC浓度在8至12 mg L -1之间时,湖水褐变程度更高,导致蓝细菌被混合营养菌替代。湖褐变似乎助长浮游植物叶绿素一个而触发转移到浮游植物能如果逐步棕色的水不兴旺生存浓度。因此,湖褐变可能会对通过下部食物网的能量传递产生影响。