Exploring functional interfaces: extreme biogenic fluctuations may amplify or buffer environmental stress on organisms associated with marine macrophytes

该项目的总体目标是通过在与生物体有关的尺度上评估环境的强烈生物起伏对压力的调节能力，完善我们对沿海生态系统对预测的全球变化情景的反应的理解。由于季节性或日间事件(例如，水混合、潮汐、初级生产)，沿海社区经常受到强烈的环境波动的影响。这种波动的强度随着空间尺度的减小而增大，并且在覆盖植物表面的亚毫米扩散边界层(DBL)中强度极高。例如，温度、pH、二氧化碳和O2的这些波动往往比在全球变化过程中预测的变化要大得多。它们可能提供暂时的避难所，躲避环境压力，或者它们可能使有机体对环境变化变得更加坚强。沿海底栖生物应对这种环境波动的机制几乎没有人研究过。栖息在DBL中的附生生物包括钙化的苔藓虫、管虫和珊瑚藻类，根据大型植物的代谢活动(光合作用和呼吸速率)和环境条件(初步研究)，O2、CO2和H(PH)浓度的梯度很强，但在时间上不稳定。这些生物起伏有可能掩盖、放大或缓冲包括全球变化压力在内的环境压力。考虑到大型植物(如海草、海带、膀胱残骸)作为生物工程的重要性，以及它们所支持的各种和生态上重要的附生生物，在全球变化下研究它们之间的相互作用是非常重要的。因此，该项目的具体目标是：(I)描述不同全球变化情景(变暖、海洋酸化、缺氧)下大型植物DBL的动态；(Ii)调查其对钙化附生生物的影响及其适应或适应强烈波动的能力；(Iii)确定附生生物对不同微生境(大型植物与惰性表面DBL)的潜在预适应；以及(Iv)评估大型植物为海洋酸化和缺氧提供临时避难所的潜力。预计结果将阐明生物应对波动的机制及其对全球变化的容忍度，而后者可能与传统的稳态开放海洋全球变化实验的结果有很大不同。

The overarching aim of the project is to refine our understanding of coastal ecosystem responses to predicted Global Change scenarios by evaluating the capacity of stress-modulation by strong biogenic fluctuations of the environment at an organism-relevant scale. Coastal communities are often exposed to strong environmental fluctuations due to seasonal or diurnal events (e.g. water mixing, tides, primary production). The intensity of such fluctuations tends to increase with decreasing spatial scale and is extremely high in the sub-mm diffusive boundary layer (DBL) covering macrophyte surfaces. These fluctuations, in, for example, temperature, pH, CO2 and O2, are often of much greater magnitude than predicted changes in the course of Global Change. They may either offer temporal refuges from environmental stress or they may harden organisms to environmental changes. The mechanism of coastal benthic organisms to cope with such environmental fluctuations is virtually unstudied. Epibionts inhabiting the DBL including calcifying bryozoans, tube worms and coralline algae experience strong but temporally instable gradients in and extremes of O2, CO2 and H+ (pH) concentrations depending on the macrophytes metabolic activity (photosynthesis and respiration rates) and ambient conditions (pilot study). These biogenic fluctuations have the potential to mask, amplify or buffer environmental stress including Global Change pressures. Considering the importance of macrophytes (e.g. seagrass, kelp, bladder wreck) as bioengineers of diverse and productive coastal ecosystems and the diverse and ecologically important epibionts they support, it is of primordial importance to investigate their interaction under Global Change. Therefore, the specific aims of this project are (i) to characterize the dynamics of the DBL of macrophytes under different Global Change scenarios (warming, ocean acidification, hypoxia), (ii) to investigate its effect on calcifying epibionts and their ability to acclimatize or adapt to a strongly fluctuating regime, (iii) to identify potential pre-adaptation of epibionts to different micro-habitats (macrophyte vs. inert surface DBL) and (iv) to assess the potential of macrophytes to provide temporal refuge from ocean acidification and hypoxia. Results are expected to shed light on mechanisms of organisms to cope with fluctuations and their tolerance towards Global Change, while latter may differ significantly from results based on traditional steady-state open-ocean Global Change experiments.