Climate-Change Refugia for the Bubblegum Coral Paragorgia arborea in the Northwest Atlantic

The large, habitat-forming bubblegum coral, Paragorgia arborea, is a vulnerable marine ecosystem indicator with an antitropical distribution. Dense aggregations of the species have been protected from bottom-contact fishing in the Scotian Shelf bioregion off Nova Scotia, Canada in the northwest Atlantic Ocean. Recently, basin-scale habitat suitability ensemble modeling has projected an alarming loss of 99% of suitable habitat for this species across the North Atlantic by 2100. Here, a regional reassessment of the predicted distribution of this species in the bioregion, using both machine learning (random forest) and generalized additive model (GAM) frameworks, including projection to 2046−2065, was undertaken. Extrapolation diagnostics were applied to determine the degree to which the models projected into novel covariate space (i.e., extrapolation) in order to avoid erroneous inferences. The best predictors of the species’ distribution were a suite of temporally-invariant terrain variables that identified suitable habitat along the upper continental slope. Additional predictors, projected to vary with future ocean climatologies, identified areas of the upper slope in the eastern portion of the study area that will remain within suitable ranges for P. arborea at least through to the mid-century. Additionally, 3-D Lagrangian particle tracking simulations indicated potential for both connectivity among known occurrence sites and existing protected areas, and for colonization of unsurveyed areas predicted to have suitable habitat, from locations of known occurrence. These results showed that extirpation of this iconic species from the Scotian Shelf bioregion is unlikely over the next decades. Potential climate refugia were identified and results presented in the context of protected area network design properties of representativity, connectivity, adequacy, viability and resilience. Here we provide the locations for presence and absence records for P. arborea (response data) and the interpolated environmental predictor variables used in present day and future species distribution models. Predicted surfaces from random forest (RF) and generalized additive models (GAM) are provided for present day and projected (RCP4.5 and RCP8.5 2045-2065) time frames. Outputs after applying extrapolation diagnostic tools (calculated using the R package dsmextra) are provided for each model. Climate change refugia for this species under the RCP4.5 2045-2065 projections are found in the Fig8 folder showing analogue conditions. Explanations for the surfaces can be found in Wang, Murillo & Kenchington (2022) and in the associated supplementary files. Links to both are provided (see related links). Reference: Wang S, Murillo FJ and Kenchington E (2022) Climate-Change Refugia for the Bubblegum Coral Paragorgia Arborea in the Northwest Atlantic. Front. Mar. Sci. 9:863693. doi: 10.3389/fmars.2022.863693作为大型造栖的泡泡糖珊瑚（bubblegum coral），树状共柱柳珊瑚（Paragorgia arborea）是脆弱海洋生态系统指示种（vulnerable marine ecosystem indicator），具有反热带分布（antitropical distribution）格局。该物种的密集群落在加拿大新斯科舍省周边西北大西洋海域的斯科舍陆架生物区（Scotian Shelf bioregion）已被纳入底拖捕捞禁捕范围。近期，基于流域尺度生境适宜性集合模型（basin-scale habitat suitability ensemble modeling）的预测结果显示，到2100年，北大西洋全域该物种的适宜生境或将损失99%，形势令人担忧。本研究针对该生物区内该物种的预测分布开展区域重评估，采用机器学习（machine learning）、随机森林（random forest）与广义加性模型（generalized additive model，GAM）两种建模框架，并将物种分布预测至2046−2065年。研究引入外推诊断（extrapolation diagnostics）工具，以判定模型向新协变量空间（covariate space）外推的程度，进而避免得出错误推断。该物种分布的最优预测因子为一组时间不变地形变量（temporally-invariant terrain variables），可精准识别大陆坡上段（upper continental slope）的适宜生境。其余随未来海洋气候动态变化的预测因子则识别出研究区东部大陆坡上段的区域，这些区域至少在本世纪中叶前仍将处于树状共柱柳珊瑚的适宜生境范围内。此外，三维拉格朗日粒子追踪模拟（3-D Lagrangian particle tracking simulations）结果表明，已知分布位点与现有保护区之间存在种群连通潜力，同时已知分布位点的种群可定植到经预测拥有适宜生境的未调查区域。本研究结果显示，未来数十年内，斯科舍陆架生物区中的这一标志性物种不太可能发生局部灭绝。本研究识别了潜在的气候避难所（climate refugia），并从保护区网络设计的代表性、连通性、充足性、可持续性与恢复力维度对研究结果进行阐释。 本数据集提供了树状共柱柳珊瑚的存在与缺失记录点位（响应数据），以及用于当前及未来物种分布模型的插值环境预测因子。本数据集提供了随机森林（RF）与广义加性模型（GAM）在当前时段及典型浓度路径（Representative Concentration Pathway，RCP）4.5、8.5情景下2045−2065年的预测生境表面。每个模型的外推诊断工具输出结果（通过R包dsmextra（R package dsmextra）计算得到）均已一并提供。RCP4.5情景2045−2065年下该物种的气候变化避难所结果存放在Fig8文件夹中，展示了相似气候条件的区域。生境表面的详细说明可参见Wang、Murillo与Kenchington（2022）的研究论文及相关补充材料，二者的链接均已提供（详见相关链接）。 参考文献：Wang S、Murillo FJ与Kenchington E（2022）《西北大西洋泡泡糖珊瑚树状共柱柳珊瑚（Paragorgia arborea）的气候变化避难所》，《海洋科学前沿》（Frontiers in Marine Science）第9卷：863693。DOI: 10.3389/fmars.2022.863693