Mapping of temperate subtidal seagrass beds in Tayaritja Sea Country (Furneaux Group of Islands), Lutruwita (Tasmania) (NESP MaC 3.6)

Seagrass beds are a dominant marine ecosystem of Tayaritja (the Furneaux Group of Islands) in the north-eastern waters off Tasmania. Historical coarse mapping has indicated extensive beds of Posidonia, Amphibolis, Heterozostera, and Zostera species, potentially comprising some of the largest and deepest seagrass extents found in temperate Australian waters. However, limited data on the distribution and ecological value of these seagrass habitats represents a significant knowledge gap in understanding Australia's wetland natural assets.This project mapped the extent, ecological composition, population structure, and blue carbon value of seagrass beds around Tayaritja, in partnership with the Tasmanian Aboriginal Centre. The study area focused on the coastal waters surrounding Flinders Island in the western Furneaux Group, with mapping extending from the high tide line to the depth limit of reliable optical detection (approximately 30 m), based on analysis of field data and satellite imagery capabilities in the region.This record specifically describes the benthic mapping component of the study. See https://doi.org/10.25959/WRXK-KV06 for imagery annotation data from the field validation campaigns.A combination of close-range remote sensing methods was used to map the extent and ecological values of seagrass beds. The approach developed through this study contributed to the creation of the NESP Standard Operating Procedure (SOP) for Seagrass Mapping using Optical Remote Sensing (https://sustainabledevelopmentreform.github.io/nesp-sop-seagrass-mapping)..High-resolution satellite imagery from Sentinel-2 (10 m) sensors, combined with bathymetric LiDAR data and oceanographic variables, was used to map baseline seagrass extent and composition. A field campaign deployed a Benthic Observation Survey System (BOSS) and unBaited Remote Underwater stereo-Video system (stereo-uBRUV) at approximately 400 locations to validate remote sensing outputs. From these data, maps were produced showing the extent and coverage of seagrass, sand, and macroalgae, and where possible, seagrass species composition, subject to water depth and clarity constraints.See the "Lineage" section of this record for full methodology.Three key types of mapping products were developed:---Occurrence probability maps---Continuous probability surfaces (0-100%), modelled from presence/absence data, indicating the likelihood of habitat presence at each pixel for:• Seagrass (all morphologies; > 5% cover observed in underwater field imagery)• Macroalgae species/assemblages• Sand---Habitat percentage cover maps---Quantitative estimates of percent cover for each habitat category:• Seagrass (all morphologies)• Macroalgae species/assemblages• Sand---Derived products---• Baseline binary presence/extent maps derived from optimised probability thresholds:    ○ Seagrass:     sgprob > 0.5 & sgprob > macroprob & sandcover < 0.9    ○ Macroalgae: macroprob > 0.5 & macroprob > sgprob & sandcover < 0.9    ○ Sand:           sandprob > 0.5 & sandcover < 0.2• Predicted seagrass species composition of binary extent map.• Fractional cover visualisation: combining cover percentages of multiple habitats into a single composite product• Composite habitat maps: combining binary habitat extents and delineating mixed habitat classesThese complementary products serve different purposes: probability maps provide confidence measures, extent maps delineate habitat boundaries, percent cover maps support quantitative analysis of habitat density patterns, and composite habitat maps represent the diversity of mixed habitat classes. Together, they provide a comprehensive understanding of seagrass and associated habitat distribution across the study area.

海草床（seagrass beds）是塔斯马尼亚东北部海域塔亚里贾（弗诺群岛群，the Furneaux Group of Islands）的典型海洋生态系统。历史粗分辨率制图已识别出分布广泛的波喜荡属（Posidonia）、安波藻属（Amphibolis）、异叶藻属（Heterozostera）以及大叶藻属（Zostera）海草床，其覆盖范围或为澳大利亚温带海域已发现的最大、最深的海草分布区之一。然而，此类海草栖息地的分布与生态价值数据极为匮乏，成为认知澳大利亚湿地自然资产的重大知识空白。

本项目与塔斯马尼亚原住民中心合作，对塔亚里贾周边海草床的分布范围、生态组成、种群结构及蓝碳价值开展制图工作。研究区域聚焦于弗诺群岛群西部的弗林德斯岛周边近岸海域，制图范围从高潮线延伸至可靠光学探测的深度极限（约30米），该范围基于区域实地数据与卫星影像成像能力的分析确定。

本记录专门描述该研究中的底栖制图（benthic mapping）部分。野外验证作业的影像注释数据可参见https://doi.org/10.25959/WRXK-KV06。

研究采用近程遥感相结合的方法，对海草床的分布范围与生态价值进行制图。本研究开发的方法支撑了《国家环境科学项目（National Environmental Science Program, NESP）光学遥感海草制图标准作业流程（Standard Operating Procedure, SOP）》的编制（https://sustainabledevelopmentreform.github.io/nesp-sop-seagrass-mapping）。

研究使用哨兵-2号（Sentinel-2）10米分辨率卫星影像，结合测深激光雷达（bathymetric LiDAR）数据与海洋学变量，绘制海草基础分布范围与组成图。野外调查在约400个点位部署了底栖观测调查系统（Benthic Observation Survey System, BOSS）与无诱饵水下立体视频系统（unBaited Remote Underwater stereo-Video system, stereo-uBRUV），以验证遥感反演结果。基于上述数据，研究生成了海草、泥沙与大型藻类的分布范围与盖度图，并在水深与水体透明度允许的前提下，生成海草物种组成图。完整方法学说明参见本记录的"Lineage"章节。

本研究共生成三类核心制图产品：
1. **出现概率图**
基于存在/不存在数据建模得到的连续概率表面（0-100%），用于指示每个像元处栖息地存在的可能性，涵盖以下类型：
• 海草（所有形态；实地水下影像中盖度>5%）
• 大型藻类物种类群/组合
• 泥沙
2. **栖息地盖度百分比图**
各栖息地类别的定量盖度百分比估算结果，涵盖：
• 海草（所有形态）
• 大型藻类物种类群/组合
• 泥沙
3. **衍生产品**
• 基于优化概率阈值得到的二元存在/范围图：
○ 海草：sgprob > 0.5 且 sgprob > macroprob 且 sandcover < 0.9
○ 大型藻类：macroprob > 0.5 且 macroprob > sgprob 且 sandcover < 0.9
○ 泥沙：sandprob > 0.5 且 sandcover < 0.2
• 二元范围图对应的预测海草物种组成
• 盖度分数可视化：将多栖息地的盖度百分比整合为单一复合产品
• 复合栖息地图：整合二元栖息地范围并划分混合栖息地类群

这些互补产品各有其应用场景：出现概率图提供置信度度量，范围图标注栖息地边界，盖度百分比图支持栖息地密度格局的定量分析，复合栖息地图则展现混合栖息地类群的多样性。综合来看，这些产品可全面揭示研究区域内海草及相关栖息地的分布特征。