ABSTRACT Floating algae can be found in high abundances at mid and high latitudes, their prolonged positive buoyancy allowing long-distance dispersal. However, despite their importance to dispersal and ecological and evolutionary meta-population dynamics, little is known about the buoyancy responses of high latitude algae to the conditions at the sea surface. Indeed, even at 60°N environmental conditions during spring/summer can be challenging, and may cause the demise and sinking of floating algae. The bladderwrack Fucus vesiculosus from the Northern Baltic Sea floats on the sea surface when detached from the benthic substratum. We conducted a field experiment with tethered individuals during their reproductive period to measure variation in floating time and how that is related to morphological traits such as occurrence of vesicles and/or receptacles, and to measure growth and photosynthesis while afloat. Algal individuals with receptacles tended to sink quickly, whereas the longest floating time was evident for individuals carrying vesicles but lacking receptacles. While afloat, all individuals grew in size, showed photosynthetic acclimation to sea surface conditions and had a few invertebrates associated with them. Our results showed that rafts of F. vesiculosus were physiologically viable until their day of sinking and that morphological traits such as the occurrence of vesicles and receptacles modified their floating time. Accordingly, floating algae with a similar morphological set-up, and thus also reproductive phenology, to F. vesiculosus can have a high floating persistence, but, depending on their reproductive structures, they may mostly serve as long-range dispersal vehicles for associated organisms.

中文翻译：

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保持漂浮需要两个条件：形态学和生理适应的相互作用确保了水泡墨角藻（Phaeophyceae、Fucales）的长期漂浮扩散

摘要 在中高纬度地区可以发现大量漂浮的藻类，它们长期的正浮力允许远距离扩散。然而，尽管它们对扩散、生态和进化元种群动态很重要，但对高纬度藻类对海面条件的浮力响应知之甚少。事实上，即使在春季/夏季 60°N 的环境条件下也可能具有挑战性，并可能导致漂浮的藻类死亡和沉没。来自北波罗的海的膀胱海角藻在与底栖基质分离时漂浮在海面上。我们在繁殖期对拴系的个体进行了一项实地实验，以测量漂浮时间的变化及其与形态特征（如囊泡和/或容器的出现）的关系，并测量漂浮时的生长和光合作用。带有容器的藻类个体倾向于快速下沉，而最长的漂浮时间对于携带囊泡但没有容器的个体来说是显而易见的。在漂浮时，所有个体的体型都变大，表现出对海面条件的光合作用适应能力，并且有一些无脊椎动物与之相关。我们的结果表明，F. vesiculosus 的筏子在它们下沉的那一天之前都是生理上可行的，并且形态特征（例如囊泡和容器的出现）改变了它们的漂浮时间。因此，