Department of Biology, Saint Louis University, 3507 Laclede Avenue, St. Louis, MO 63103, USA; Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA 94720, USA.
Department of Biology, Saint Louis University, 3507 Laclede Avenue, St. Louis, MO 63103, USA.
Sci Total Environ. 2020 Jun 25;723:138084. doi: 10.1016/j.scitotenv.2020.138084. Epub 2020 Mar 20.
A lack of understanding exists regarding how freshwater species will respond to increases in temperature associated with ongoing changes in climate. Non-urban to urban thermal gradients generated by urban heat islands can serve as models to characterize the effects of relatively consistent increases in temperature on freshwater ecosystems over several decades. This study investigates the apparent responses of two freshwater fish species, Campostoma anomalum (Central Stoneroller) and Lepomis macrochirus (Bluegill), to directional changes in temperature over the past century across the non-urban to urban gradient in the Saint Louis, Missouri region in the central United States. Differences in air temperature across this gradient have increased by approximately 3 °C since 1920. Critical thermal maximum (CTMax) assays were conducted on individuals from fish populations across this gradient from either streams (C. anomalum) or ponds (L. macrochirus) to assess whether thermal tolerance is associated with water temperature among sites. According to expectations based on the effect of an urban heat island, maximum water temperature at stream sites was positively correlated with percent urban landcover around the sites. Moreover, CTMax among populations of C. anomalum was positively correlated with maximum water temperature at each site, suggesting that this species has likely responded to increases in temperature over the past several decades. There was no relationship between percent urban landcover and maximum water temperature in the pond systems. There was also no relationship between CTMax and maximum water temperature among L. macrochirus populations. The pond systems and populations of L. macrochirus are highly managed, which may limit local physical and biological responses to increases in air temperature. Results suggest that freshwater habitats in urban environments and the species inhabiting these areas are responding differently to recent increases in air temperature, highlighting the complexity of the physical and biological components of these systems.
人们对于淡水物种将如何应对与气候变化相关的温度升高知之甚少。城市热岛产生的从非城市到城市的温度梯度可以作为模型，用于描述在几十年内相对稳定的温度升高对淡水生态系统的影响。本研究调查了在美国中部密苏里州圣路易斯地区，从非城市到城市梯度上，两个淡水鱼类物种——安大略中央石首鱼（Campostoma anomalum）和蓝鳃太阳鱼（Lepomis macrochirus）——在过去一个世纪中对温度变化的明显反应。自 1920 年以来，该梯度上的空气温差增加了约 3°C。对来自该梯度上溪流（C. anomalum）或池塘（L. macrochirus）鱼类种群的个体进行了临界热最大值（CTMax）测定，以评估在不同地点，热耐受性是否与水温有关。根据城市热岛效应的影响，溪流地点的最高水温与周围地点的城市土地覆被百分比呈正相关。此外，C. anomalum 种群的 CTMax 与每个地点的最高水温呈正相关，表明该物种可能在过去几十年中对温度升高做出了反应。池塘系统中城市土地覆被百分比与最高水温之间没有关系。L. macrochirus 种群的 CTMax 与最高水温之间也没有关系。池塘系统和 L. macrochirus 种群受到高度管理，这可能限制了它们对空气温度升高的局部物理和生物反应。结果表明，城市环境中的淡水栖息地以及栖息在这些地区的物种对最近的空气温度升高有不同的反应，突出了这些系统物理和生物成分的复杂性。
