Shifting Seas - a gene landscape approach to understanding saltmarsh vulnerability and resilience to sea-level rise

盐沼是所谓的基于自然的海岸防御解决方案(NBS)的重要组成部分，这是制定英国政府政策的核心角色，旨在未来25年更好地管理、保护和恢复这一栖息地。为了落实这一政策以及由此产生的更广泛的生态系统和社会利益，我们必须了解海平面上升(SLR)以及相关的沿海洪水和侵蚀给沿海生境带来的风险和机遇。“漂流海洋”采用基因到景观尺度的方法来阐明盐沼对SLR的响应，融合了最先进的跨学科方法，包括潮汐流体动力学、地貌学和沉积学、植物遗传学、盐沼生态学、田间实验和生态模型。我们探讨了以下四个目标。目标1-盐沼地带是由不同但重叠的个体物种范围产生的，反映了它们对与潮汐淹没相关的因素的容忍能力。由于海拔和淹没频率对物种的“基本”和“实现”生态位具有主要控制作用，因此通过SLR对潮差的改变可能会对盐沼群落的结构和功能产生影响。将对盐沼进行调查，以确定组成物种的范围，但特别关注典型的高、中、低沼泽物种，以及关键物理变量如何同步变化。这提供了一个基线，可以根据通过结合无人机调查、水位测量和潮汐模型确定的潮汐框架中当前的位置(即淹没频率、淹没持续时间、涌现持续时间)来确定每个物种的海拔生态位。这些数据将建立一个生态位模型来预测盐沼植物可能发生或入侵一个地区的程度，以及在不同ACC和管理情景下控制种群和群落结构的过程。目的2-沼泽海拔高度可以影响组成物种的遗传多样性，从而影响其对持续的SLR和相关环境因素的适应能力。此外，植物对模拟海水淹没反应的基因差异表明，洪水可能是一种潜在的选择性过滤器，可能会消除关键物种，降低功能可持续性、生态系统对SLR的复原力，以及对海岸防御的贡献。从目标1中，我们选择了两个地点来代表典型的“高弹性”(泥沙淤积与SLR匹配)和“高脆弱性”(泥沙淤积滞后于SLR)情景。我们将使用基因测序的方法在多倍体中发现SNP，以确定跨越沼泽高地选定的高韧性和高脆弱性地点的选定物种的种群结构、遗传多样性和分化。目标3-阐明在高韧性/脆弱地点运行的水动力特性，以及了解关键植物物种的本地分布、它们的遗传多样性以及对海水浸泡和沉积物沉积的响应，可能揭示更多关于盐沼对SLR的适应。使用‘沼泽器官’技术，我们将在海拔梯度上种植不同基因类型的目标植物物种，结果将提供一个模型，预测物种和遗传如何可变地影响沼泽对SLR的恢复能力/脆弱性。目标4-我们将提供一个空间上明确的‘机会图谱工具’，为支持盐沼生态系统保护、恢复和保护的适应途径提供必要的管理干预措施。通过阐明SLR适应的一些(遗传、水动力、生态)障碍，我们提供了预测盐沼生态系统和物种的变化和风险所需的关键证据，并反过来瞄准了对海平面长期变化具有弹性的解决方案。

Saltmarsh is a vital component of so-called Nature based Solutions (NbS) to coastal defence, a role central to developing UK Government policy, that aims to better manage, protect and restore this habitat over the next 25 years. In order to deliver this policy, and the wider ecosystem and societal benefits that accrue, we must understand the risks and opportunities to coastal habitats from sea level rise (SLR) and associated coastal flooding and erosion. 'Shifting Seas' takes a gene to landscape scale approach to elucidate saltmarsh response to SLR, incorporating state of the art, interdisciplinary approaches including tidal hydrodynamics, geomorphology and sedimentology, plant genetics, saltmarsh ecology, field experiments and ecological modelling. We explore the following four objectivesObjective 1 - Saltmarsh zonation is generated by the different, but overlapping, ranges of individual species, reflecting their ability to tolerate factors associated with tidal submergence. Because elevation and inundation frequency exerts primary controls on a species 'fundamental' and 'realised' niche, changes to tidal range through SLR could have consequences for saltmarsh community structure and function. Saltmarshes will be surveyed to determine the range of component species, but with a particular focus on typical high- , mid-, and low- marsh species, and how key physical variables vary in tandem. This provides a baseline from which the elevation niche of each species can be set against present day position in the tidal frame (i.e. inundation frequencies, inundation duration, emergence duration) determined through a combination of UAV survey, water level measurements and tidal modelling. These data will build a niche model to predict the extent to which saltmarsh plants may occur or invade an area and the processes controlling population and community structure under different ACC and management scenarios.Objective 2 - Marsh elevation can influence the genetic diversity of component species and with it resilience to continued SLR and associated environmental factors. Moreover, genotypic variation in plant response to simulated seawater inundation signpost flooding as a potential selective filter that could eliminate key species and reduce functional sustainability, ecosystem resilience to SLR, and contribution to coastal defence. From Objective 1, we select two sites to represent typical 'high resilience' (sediment accretion matches SLR) and 'high vulnerability' (sediment accretion lags SLR) scenarios. We will use a genotype by sequencing approach for SNP discovery in polyploids to determine the population structure, genetic diversity and differentiation of selected species across the marsh elevation at the selected 'high resilience' and 'high vulnerability' sites.Objective 3 - Elucidation of the hydrodynamic properties operating at 'high resilience/vulnerability' sites, coupled with an understanding of the local distribution of key component plant species, their genetic diversity, and response to seawater immersion and sediment deposition, may reveal much about saltmarsh adaptation to SLR. 'Using the 'marsh organ' technique, we will plant different genotypes of the target plant species across an elevational gradient, the results informing a model forecasting how species- and genetic-variably influences marsh resilience / vulnerability to SLR.Objective 4 - We will deliver a spatially explicit 'opportunity mapping tool' informing management interventions necessary to support adaptation pathways for the conservation, restoration and protection of saltmarsh ecosystems. By elucidating the some of the (genetic, hydrodynamic, ecological) barriers to SLR adaptation, we provide crucial evidence needed to predict changes and risks to saltmarsh ecosystems and species, and in turn target solutions resilient to long-term sea-level change.