Distribution of algae in the San Joaquin River, California, in relation to nutrient supply, salinity and other environmental factors
Distribution of algae in the San Joaquin River, California, in relation to nutrient supply, salinity and other environmental factors
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DOI：
10.1046/j.1365-2427.2001.00740.x
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发表时间：
2001-09
影响因子：
2.7
通讯作者：
H. V. Leland;L. Brown;D. K. Mueller
中科院分区：
文献类型：
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作者：
H. V. Leland;L. Brown;D. K. Mueller
1.研究了圣华金河及其主要支流浮游植物的分类组成和生物量以及底栖植物的分类组成与水化学、生境和水流状况的关系。农业排水和地下水流有助于在这个富营养化的“低地型”河流的盐度和营养物的复杂梯度。2.由于生长的光限制条件，在圣华金河没有支流流入的夏季和秋季，藻类的维持需求超过了生产。与正常流量年份夏季无机氮和可溶性活性磷浓度的大幅增加相反，藻类生物量的净损失（2-4 μg L−1 day−1叶绿素a）发生在没有显著支流流入的中游河段。然而，在内华达州的一条大型支流下游，藻类生物量的净增加（6-11 μg L−1天−1）发生在夏季，但不是在春季（损失1-6 μg L−1天−1）或秋季（损失2-5 μg L−1天−1）。3.浮游植物占主导地位，在夏季由'R-选择'为中心的硅藻（海链藻目），物种都耐受可变的盐度和广泛分布在圣华金河。羽状硅藻的比例更丰富（生物量）在冬季，春季和秋季。丰富的类群包括硅藻小环藻Meneghiniana，双丝藻cf。potamos、Cyclostephanos invisitatus、海链藻Thalassiosira weissflocculus、针状菱形藻Nitzschia acicularis、N. palea和N.和四尾栅藻（Scenesdesmus quadricauda）。丰富的物种的模式表明，组装的浮游植物是有限的光和流动制度比营养供应。4.底栖植物主要是较大的、繁殖速度较慢的羽纹硅藻。在数量众多的物种中，很少有广盐性的。硅藻Navicula recens和Nitzschia inscarcua和蓝藻，颤藻属，是主要的夏末底栖物种上游的mainstem和排水的圣华金河谷。其它种类丰富的硅藻（双眉藻（Amphora veneta）、拟杆硅藻（Bacillaria paxillifera）、舟形藻（Navicula acrylica）、两栖菱形藻（Nitzschia amphila）、N. fonticola，N. palea，Pleurosigma salinarum）也是运动种。虽然这些物种中的许多也丰富的下游段与河流排水的内华达州，相对丰富的匍匐（Cocconeis胎盘变种。euglypta、微小舟形藻（Navicula minima））和直立或具柄的曲壳藻（Achnanthidium deflexum）、披针曲壳藻（Achnanthes lanceolata）、小林异极藻（Gomphonema kobayasii）、小舟形藻（G.小变种lagenula）硅藻和Stigeoclonium sp.在这些较低的圣华金河段。5.一个加权平均回归模型，在圣华金河和圣华金河谷内的主要支流段的盐度和底栖藻类丰度的基础上，产生了一个非常显着的系数的决定（r2=0.84）和低预测误差之间的盐度推断物种和观察到的，表明耐盐性是一个主要的限制生长和组装的植物底栖生物。同样的可预测性措施表明，基于无机氮的模型性能不佳。然而，与更大的代表性的支流（包括段内的塞拉利昂内华达州山麓）的样本集，无机氮模型也产生了非常显着的系数的决定（r2=0.87）和低预测误差之间的物种推断和观察到的浓度。与盐度模型（r2=0.94）的扩大的数据集，系统的差异（残差的偏差增加）存在于高无机氮浓度。这些结果表明，盐度和无机氮之间的相互作用，对圣华金河流域的底栖藻类群落结构的限制。
1. The taxonomic composition and biomass of the phytoplankton and the taxonomic composition of the phytobenthos of the San Joaquin River and its major tributaries were examined in relation to water chemistry, habitat and flow regime. Agricultural drainage and subsurface flow contribute to a complex gradient of salinity and nutrients in this eutrophic, ‘lowland type’ river. 2. Because of light-limiting conditions for growth, maintenance demands of the algae exceed production during summer and autumn in the San Joaquin River where there is no inflow from tributaries. In contrast to substantial gains in concentration of inorganic nitrogen and soluble reactive phosphorus during the summer of normal-flow years, net losses of algal biomass (2–4 μg L−1 day−1 chlorophyll a) occurred in a mid-river segment with no significant tributary inflow. However, downstream of a large tributary draining the Sierra Nevada, a substantial net gain in algal biomass (6–11 μg L−1 day−1) occurred in the summer, but not in the spring (loss of 1–6 μg L−1 day−1) or autumn (loss of 2–5 μg L−1 day−1). 3. The phytoplankton was dominated in summer by ‘r-selected’ centric diatoms (Thalassiosirales), species both tolerant of variable salinity and widely distributed in the San Joaquin River. Pennate diatoms were proportionally more abundant (in biomass) in the winter, spring and autumn. Abundant taxa included the diatoms Cyclotella meneghiniana, Skeletonema cf. potamos, Cyclostephanos invisitatus, Thalassiosira weissflogii, Nitzschia acicularis, N. palea and N. reversa, and the chlorophytes Chlamydomonas sp. and Scenesdesmus quadricauda. Patterns in the abundance of species indicated that assembly of the phytoplankton is limited more by light and flow regime than by nutrient supply. 4. The phytobenthos was dominated by larger, more slowly reproducing pennate diatoms. Few of the abundant species are euryhaline. The diatoms Navicula recens and Nitzschia inconspicua and cyanophytes, Oscillatoria spp., were the principal late-summer benthic species upstream in the mainstem and in drainages of the San Joaquin Valley. Many of the other abundant diatoms (Amphora veneta, Bacillaria paxillifer, Navicula symmetrica, Nitzschia amphibia, N. fonticola, N. palea, Pleurosigma salinarum) of late-summer assemblages in these segments also are motile species. While many of these species also were abundant in segments downstream of confluences with rivers draining the Sierra Nevada, the relative abundance of prostrate (Cocconeis placentula var. euglypta, Navicula minima) and erect or stalked (Achnanthidium deflexum, Achnanthes lanceolata, Gomphonema kobayasii, G. parvulum var. lagenula) diatoms and Stigeoclonium sp. was greater in these lower San Joaquin River segments. 5. A weighted-averaging regression model, based on salinity and benthic-algal abundance in the San Joaquin River and segments of its major tributaries within the San Joaquin Valley, yielded a highly significant coefficient-of-determination (r2=0.84) and low prediction error between salinity inferred from the species and that observed, indicating that salinity tolerance is a primary constraint on growth and assembly of the phytobenthos. The same measures of predictability indicated poor performance of a model based on inorganic nitrogen. However, with a greater representation of tributaries (including segments within the Sierra Nevada foothills) in the sample set, an inorganic nitrogen model also yielded a highly significant coefficient-of-determination (r2=0.87) and low prediction error between the species-inferred and the observed concentration. As with the salinity model (r2=0.94) for the enlarged data set, a systematic difference (increased deviation of residuals) existed at high inorganic nitrogen concentrations. These results indicate substantial interaction between salinity and inorganic nitrogen as constraints on the structure of benthic-algal communities of the San Joaquin River basin.