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首页> 外文期刊>Aquatic Sciences >Effects of watershed land use on sources and nutritional value of particulate organic matter in temperate headwater streams
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Effects of watershed land use on sources and nutritional value of particulate organic matter in temperate headwater streams

机译：流域土地利用对温带源流中有机质颗粒物来源和营养价值的影响

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摘要

Suspended particulate organic matter (POM) in headwater streams is an important source of food and energy to stream food webs. In order to determine the effects of watershed land use on the sources and characteristics of POM, we compared the lipid composition of POM (fatty acid, aliphatic alcohol and sterol) from streams influenced by different types of watershed land use. Eight first-order streams discharging to the York River Estuary (Virginia, USA) were sampled during baseflow conditions bi-monthly from February to November 2009, including streams draining forest-dominated, pasture-dominated, cropland-dominated, and urban land-dominated watersheds. Allochthonous vs. autochthonous lipids showed that POM in most of these streams was dominated by allochthonous sources (59.5 ± 14.2 vs. 39.6 ± 14.5 % for aliphatic alcohols and 52.9 ± 11.5 vs. 34.1 ± 10.3 % for sterols). The relative abundance of allochthonous vs. autochthonous lipid inputs to POM varied as a function of land use type. POM in streams draining forest-dominated watersheds contained a higher proportion of allochthonous lipids and a lower proportion of autochthonous lipids than the streams influenced by human land use. The contribution of bacterial fatty acids differed significantly among sampling times (P = 0.003), but not among land use types (P = 0.547). Stepwise linear regression model selected nitrate and temperature as the best predictors of variation in bacterial inputs to POM. Proxies used to assess the nutritional value of POM potentially available to stream consumers included C:N ratios, and the concentrations of total long-chain polyunsaturated fatty acids, eicosapentae-noic acid, arachidonic acid, and cholesterol. None of these nutritional proxies differed among sampling months (P ≥ 0.171), but the proxies showed that the nutritional value of POM in forest streams was lower than in urban streams. Collectively, these findings suggest that human land use in upstream watersheds alters the source composition and nutritional value of stream POM, which not only impacts food quality for stream biota, but also potentially changes the characteristics of OM reaching downstream ecosystems.
机译：上游水流中的悬浮颗粒有机物（POM）是食物和能量流过食物网的重要来源。为了确定流域土地利用对POM来源和特性的影响，我们比较了受不同类型流域土地利用影响的溪流中POM的脂质组成（脂肪酸，脂肪醇和固醇）。从2009年2月至2009年11月，每两个月在底流条件下对八种排放到约克河河口（美国弗吉尼亚州）的一级河流进行了采样，包括排放以森林为主，牧场为主，农田为主和城市土地为主的河流分水岭。异源脂质和自生脂质显示，大多数此类物流中的POM均由异源来源控制（脂族醇为59.5±14.2 vs. 39.6±14.5％，固醇为52.9±11.5 vs. 34.1±10.3％）。异源性脂土与脂生性脂质体相对于POM的相对输入量随土地利用类型的变化而变化。与受人类土地利用影响的河流相比，排泄森林为主的流域的河流中的POM含有较高比例的异源脂质和较低比例的本地脂质。细菌脂肪酸的贡献在采样时间之间存在显着差异（P = 0.003），但在土地利用类型之间却没有显着差异（P = 0.547）。逐步线性回归模型选择硝酸盐和温度作为POM细菌输入变化的最佳预测指标。用于评估可能为消费者流产的POM的营养价值的代理包括C：N比，以及总长链多不饱和脂肪酸，二十碳五烯酸，花生四烯酸和胆固醇的浓度。这些营养指标在采样月份之间均无差异（P≥0.171），但这些指标表明，森林溪流中POM的营养价值低于城市溪流。总的来说，这些发现表明上游流域的人类土地利用改变了河流POM的来源组成和营养价值，这不仅影响河流生物群的食品质量，而且潜在地改变了进入下游生态系统的OM的特征。

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