Intertidal Rockweed Distribution

The distribution of rockweed macroalgae was determined through a combination of remote sensing and field work in the Summer – Fall 2024. Preliminary rockweed distribution was calculated in Google Earth Engine with 2015 Leaf-off aerial imagery of New Hampshire (4-band) and National Agriculture Imagery Program (2012 – 2016, 4 – band). Manual thresholds of the non-difference brown algae index, non-difference water index, ratio of Red – Blue bands, and elevation (NAVD88 m) were used to differentiate rockweed from open water, bare mud, salt marsh, and overhanging tree canopy in the intertidal zone. Field inspections of the preliminary classification were conducted by boat along all tidal rivers in the estuary to remove erroneous classification of salt marsh and overhang tree canopy. See McKown et al., 2025 for detailed project description.本研究于2024年夏秋季结合遥感技术与野外调查，明确了墨角藻（rockweed）大型藻类的空间分布特征。初步的墨角藻分布范围通过谷歌地球引擎（Google Earth Engine）计算得到，所用数据包括新罕布什尔州2015年落叶期4波段航空影像，以及2012-2016年的美国国家农业影像计划（National Agriculture Imagery Program, NAIP）4波段影像。研究通过人工阈值法，结合非差值褐藻指数、非差值水体指数、红-蓝波段比值以及采用北美垂直基准面1988（North American Vertical Datum of 1988, NAVD88）的高程数据，将潮间带内的墨角藻与开阔水体、裸露底泥、盐沼及悬垂树冠加以区分。针对上述初步分类结果，研究团队沿河口湾内所有潮汐河流乘船开展野外核查，以剔除盐沼与悬垂树冠被误分类为墨角藻的情况。项目详细研究内容参见McKown等（2025）的相关文献。