Global change impacts marine organisms and communities mainly through ocean warming, acidification, deoxygenation, and changes in nutrient inputs and water circulation. To assess the ecological impacts of global change, the effects of multiple interacting environmental drivers, including their fluctuations, should be tested at different levels of biological organization. In an outdoor mesocosm study, we investigated the differential effects of three simulated upwelling events coupled with ocean warming (1–5°C above ambient) on a temperate benthic community in the Western Baltic Sea. Ocean warming, especially in summer when temperatures are close to or above the physiological optimum of many species, is likely to impose thermal stress with species-specific impacts. As the properties of deep water vary seasonally, so will the effects of upwelling. Upwelling of cooler deep water in midsummer may alleviate thermal stress, although this mitigation may be modulated by upwelling-associated shifts in other water-quality parameters such as salinity, nutrients, or late-summer hypoxia. This investigation showed that in the Western Baltic Ocean warming was rather beneficial in early and late summer but detrimental when ambient temperatures were highest in midsummer. The effects of upwelling in the absence of ocean warming were generally weakly beneficial, while this effect tended to vanish with intensifying imposed ocean warming. Hypoxia associated with the late summer upwelling impacted some of the grazer species but did not impact the macroalgae. We conclude that in coastal temperate benthic communities, ocean warming is the predominant stressor that may partially and seasonally be buffered by upwelling.

中文翻译：

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脉冲压力：多因素环境变化对温带大型藻类群落的波动影响

全球变化主要通过海洋变暖、酸化、脱氧以及养分输入和水循环的变化影响海洋生物和群落。为了评估全球变化的生态影响，应该在不同的生物组织水平上测试多种相互作用的环境驱动因素的影响，包括它们的波动。在户外中宇宙研究中，我们调查了三个模拟上升流事件与海洋变暖（比环境温度高 1-5°C）对西波罗的海温带底栖群落的不同影响。海洋变暖，尤其是在夏季，当温度接近或高于许多物种的生理最佳状态时，可能会施加具有特定物种影响的热应力。由于深水的性质随季节变化，因此上升流的影响也会不同。仲夏较冷的深水上升流可能会减轻热应力，尽管这种缓解可能会受到上升流相关的其他水质参数（如盐度、营养物质或夏末缺氧）的变化的调节。这项调查表明，在西波罗的海，变暖在夏初和夏末相当有利，但在盛夏环境温度最高时则有害。在没有海洋变暖的情况下，上升流的影响通常是微弱的，而这种影响往往会随着海洋变暖的加剧而消失。与夏末上升流相关的缺氧影响了一些食草动物，但没有影响大型藻类。我们得出结论，在沿海温带底栖群落中，