Globally, marine sandy beaches face increasing anthropogenic pressures. Long-term maintenance of their functional capacities depends strongly on robust autochthonous biotic community baseline data. However, fine-scale temporal patterns remain poorly understood in human-impacted sites, limiting our knowledge of beach response to stressors. Marine arenicolous fungi represent a neglected group of endopsamon microorganisms (living within sandy sediments) that fulfills key ecological roles mainly as saprobes. Preliminary data suggests that this fungal group is threatened by anthropogenic disturbances in tourist beaches, yet knowledge on their ecological plasticity and fine-scale patterns is lacking. To address this knowledge gap, we investigated marine fungal community composition changes over a fine temporal scale (biweekly, over a four-month period) at an impacted Pacific tourist sandy beach, and explored associations between community composition and key environmental variables. We identified 17 taxa, within four ecological groups: strict marine arenicolous fungi (Arenariomyces majusculus, Corollospora gracilis, Corollospora maritima, Corollospora sp. 1 and 2), non-arenicolous marine fungi (Nia sp.), terrestrial borne opportunistic pathogens (Arthrographis kalrae, Parengyodontium album, Neocosmospora solani, Scopulariopsis sp., and Exophiala sp.), and facultative marine species (Aspergillus terreus and Penicillium sp.). In agreement with our hypothesis, minor fine temporal scale changes in community structure suggest arenicolous fungi persist on the beach as inoculum. Nevertheless, we detected changes in the intertidal fungal community structure in response to environmental variables, shown by the increase of terrestrial borne pathogenic species in the rainy season. Lastly, our data warn against extensive beach grooming, which may lead to the direct reduction of strict marine arenicolous fungal groups.

在全球范围内，海洋沙滩面临着越来越大的人为压力。其功能能力的长期维持在很大程度上取决于强大的本地生物群落基线数据。但是，在受人类影响的地点，人们对精细的时间模式仍然知之甚少，这限制了我们对海滩对压力源的反应的了解。海洋蜡质真菌代表了被忽略的一组内生沙门微生物（生活在沙质沉积物中），主要担负着腐霉菌的角色，履行着重要的生态作用。初步数据表明，该真菌群受到旅游海滩人为干扰的威胁，但缺乏有关其生态可塑性和精细尺度模式的知识。为了解决这一知识鸿沟，我们调查了精细时间范围内（每两周一次，在四个月内）在受影响的太平洋旅游沙滩上进行了探索，并探讨了社区构成与关键环境变量之间的关联。我们在四个生态组中确定了17个分类单元：严格的海洋砂仁真菌（枣（Arenoriomyces majusculus），花冠（Carollospora gracilis），滨海花冠（Corollospora maritima），花冠（Corollospora sp。）1和2），非气浮性海洋真菌（Nia sp。），陆生传播机会病原体（Arthrographis kalrae，Parengyodontium album，Neocosmospora solani，Scopulariopsis sp。和Exophiala sp。）以及兼性海洋物种（Apergillus terreus和Penicillium）sp。）。与我们的假设相符，群落结构的细微时间尺度上的微小变化表明，有斑纹真菌作为接种物在海滩上持续存在。但是，我们检测到了潮间真菌群落结构对环境变量的响应，这在雨季时由陆地传播的致病菌种增加了。最后，我们的数据警告不要进行广泛的海滩修饰，这可能会导致直接减少严格的海洋类真菌种群。