A mesocosm system was developed to simulate estuarine conditions characteristic of short water-residence time ecosystems of the Pacific Coast of North America, and used to evaluate the response of multiple macrophyte metrics to gradients of NO3 loading and temperature. Replicated experiments found that few responses could be directly attributed to NO3 loading up to 6 x ambient. Some response metrics exhibited weak relationships with nutrient loading but could not be resolved with available statistical power. While direct nutrient responses were found for some species-specific metrics (e.g. green macroalgal growth and biomass, tissue N%, etc.), many patterns were confounded with temperature. Temperature generally had a larger effect on response metrics than did nutrient load. Experimental macrophyte communities exhibited community shifts consistent with the predicted effects of nutrient loading at 20 °C, but there was no evidence of other eutrophication symptoms (phytoplankton blooms or hypoxia) due to the short system-residence time. The Z. marina Nutrient Pollution Index (NPI) tracked the NO3 gradient at 10 °C, but exhibited no response at 20 °C, which may limit the utility of this metric in areas with marked thermal seasonality. Results suggest that teasing apart the influence of temperature and nutrients on the expression of eutrophication symptoms will require complex multi-stressor experiments and the use of indicators that are sensitive across a broad range of conditions.

中文翻译：

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大型植物群落对快速冲洗的中层系统中氮负荷和热应激源的反应

开发了一个中观系统来模拟北美太平洋沿岸短水停留时间生态系统的河口条件特征，并用于评估多个大型植物指标对 NO3 负载和温度梯度的响应。重复实验发现，几乎没有反应可以直接归因于 NO3 负载高达 6 x 环境。一些响应指标与营养负荷的关系较弱，但无法用可用的统计能力解决。虽然发现了某些物种特定指标（例如绿色大型藻类生长和生物量、组织 N% 等）的直接营养反应，但许多模式与温度混淆。与养分负荷相比，温度对反应指标的影响通常更大。实验性大型植物群落表现出的群落变化与 20 °C 养分负荷的预测效果一致，但由于系统停留时间短，没有其他富营养化症状（浮游植物大量繁殖或缺氧）的证据。Z. marina 营养污染指数 (NPI) 在 10 °C 时跟踪 NO3 梯度，但在 20 °C 时没有响应，这可能会限制该指标在具有明显热季节性的地区的实用性。结果表明，要区分温度和营养物质对富营养化症状表达的影响，需要复杂的多压力源实验和使用在广泛条件下敏感的指标。但由于系统停留时间短，没有其他富营养化症状（浮游植物大量繁殖或缺氧）的证据。Z. marina 营养污染指数 (NPI) 在 10 °C 时跟踪 NO3 梯度，但在 20 °C 时没有表现出响应，这可能会限制该指标在具有明显热季节性的地区的实用性。结果表明，要区分温度和营养物质对富营养化症状表达的影响，需要复杂的多压力源实验和使用在广泛条件下敏感的指标。但由于系统停留时间短，没有其他富营养化症状（浮游植物大量繁殖或缺氧）的证据。Z. marina 营养污染指数 (NPI) 在 10 °C 时跟踪 NO3 梯度，但在 20 °C 时没有响应，这可能会限制该指标在具有明显热季节性的地区的实用性。结果表明，要区分温度和营养物质对富营养化症状表达的影响，需要复杂的多压力源实验和使用在广泛条件下敏感的指标。