Marine rocky intertidal organisms are amongst those most affected by climate change with regional distributional changes observed for many species. Although often ascribed to increased sea surface temperatures, precise assessment of the local habitat conditions underpinning observed and predicted changes in community assembly is lacking. Here we examine how aspect (i.e. north-south orientation) affects intertidal community composition and how rock surface temperatures and stress responses of two dominant grazer species (Patella spp.) elucidate emergent differences. We quantified year-round temperature variation and surveyed intertidal community composition on paired natural rock gullies with Equator- (EF) and Pole-facing (PF) surfaces. We also investigated variation in limpet (Patella spp.) reproductive phenology and osmotic stress. Average annual temperatures were 0.8 °C (1.6 °C at low tide) higher, with six-fold more frequent extremes (i.e. > 30 °C) on EF than PF surfaces. Intertidal community composition varied with aspect across trophic levels with greater overall species richness, abundance of primary producers and grazers on PF-surfaces, and greater barnacle abundance on EF-surfaces. Although species richness of organisms from different biogeographical origins (‘Boreal’ or ‘Lusitanian’) did not vary, the Lusitanian limpet Patella depressa exhibited earlier reproductive development on EF-surfaces and both limpet species exhibited greater thermal stress on EF-surfaces. We argue that our study system provides a good model for understanding how temperature variation at local scales can affect community composition, as well as ecophysiological and ecological responses to climate change and so better inform and predict regional range shifts over coming decades.

海洋岩石潮间带生物是受气候变化影响最大的生物之一，观察到许多物种的区域分布变化。尽管通常归因于海面温度升高，但缺乏对当地栖息地条件的精确评估，以支持观察到和预测的群落组装变化。在这里，我们研究了方位（即南北方向）如何影响潮间带群落组成以及岩石表面温度和两种主要食草动物物种 ( Patella spp.) 的应力响应如何阐明紧急差异。我们量化了全年温度变化，并调查了具有赤道 (EF) 和面向极地 (PF) 表面的成对天然岩石沟壑上的潮间带群落组成。我们还研究了帽贝（Patellaspp.) 生殖物候和渗透压力。年平均温度比 PF 表面高 0.8 °C（低潮时为 1.6 °C），EF 上的极端温度（即 > 30 °C）高出六倍。潮间带群落组成随营养水平的不同而不同，PF 表面上的总体物种丰富度更高，初级生产者和食草动物的丰度更高，EF 表面上藤壶的丰度更高。尽管来自不同生物地理起源（“北方”或“卢西塔尼亚”）的生物物种丰富度没有变化，但卢西塔尼亚帽贝 Patella depressa在 EF 表面上表现出较早的生殖发育，并且两种帽贝物种在 EF 表面上表现出更大的热应力。我们认为，我们的研究系统提供了一个很好的模型，用于理解局部尺度的温度变化如何影响群落组成，以及对气候变化的生态生理和生态响应，从而更好地告知和预测未来几十年的区域范围变化。