One-off swim surveys recording total macroalgal cover in the Great Barrier Reef, and their spatial and environmental predictors

Macroalgae are an important component of coral reef ecosystems. We identified the spatial patterns, environmental drivers and long-term trends of total cover of upright fleshy and calcareous coral reef inhabiting macroalgae in the Great Barrier Reef. The spatial study comprised of one-off surveys of 1257 transects at 324 sites on 163 reefs between latitude 11.0° to 23.6°S, coastal to offshore, at 0-18 m depth. The surveys were conducted between 1997 and 2008. Although not recent, the data are ecologically valuable due to their large spatial coverage along complex environmental gradients.Environmental predictors were obtained for each transect from in situ data, and from eReefs, a coupled hydrodynamic-biochemical model.The study found that macroalgae dominated the benthos (≥50% cover) on at least one sites onf 40.4% of surveyed inshore reefs. Spatially, macroalgal cover increased steeply towards the coast, with latitude away from the equator, and towards shallow (≤3 m) depth. Environmental conditions associated with macroalgal dominance were: high tidal range, wave exposure and irradiance, and low aragonite saturation state, Secchi depth, total alkalinity and temperature. Evidence of space competition between macroalgal cover and hard coral cover was restricted to shallow inshore sites. Our extensive empirical data and relationships may serve to parameterize ecosystem models, and to optimize refine reef condition indices based on macroalgal data for Pacific coral reefs.This dataset underpins the study: Fabricius KE, Crossman K, Jonker M, Mongin M, Thompson A . (2023) Macroalgal cover on coral reefs: spatial and environmental predictors, and decadal trends in the Great Barrier Reef. PLOS One.We acknowledge the Traditional Owners of the Sea Country of the Great Barrier Reef, and pay our respects to their Elders past, present and emerging. We acknowledge their continuing spiritual connection to their Sea Country.

大型藻类（Macroalgae）是珊瑚礁生态系统的重要组成部分。本研究明确了大堡礁（Great Barrier Reef）内栖息于珊瑚礁的直立肉质型与钙质型大型藻类总盖度的空间分布格局、环境驱动因子及长期变化趋势。本次空间研究涵盖1997年至2008年间，在南纬11.0°至23.6°、覆盖近岸至远岸海域、水深0至18米的163个礁体的324个站点开展的1257条样带一次性调查。尽管该数据集并非近年采集，但其沿复杂环境梯度的大范围空间覆盖范围，使其具备极高的生态学研究价值。每条样带的环境预测因子均取自原位观测数据，以及耦合水动力-生化模型eReefs。研究结果显示，40.4%的近岸调查礁体中，至少存在一个站点的大型藻类盖度占底栖生物群落的50%以上（即占据优势地位）。空间分布上，大型藻类盖度随向岸距离缩减、远离赤道的纬度升高以及水深变浅（≤3米）而显著升高。与大型藻类占优势相关的环境条件包括：高潮差、波浪暴露度与辐照度，以及低文石饱和度（aragonite saturation state）、赛氏盘透明度（Secchi depth）、总碱度与海水温度。大型藻类盖度与硬珊瑚盖度之间的空间竞争证据，仅局限于近岸浅水区站点。本研究的大量实证数据与相关关系，可用于参数化生态系统模型，并优化并完善基于太平洋珊瑚礁大型藻类数据的珊瑚礁健康状况指数。本数据集支撑的学术研究为：Fabricius KE, Crossman K, Jonker M, Mongin M, Thompson A. (2023) 珊瑚礁大型藻类盖度：大堡礁的空间与环境预测因子及十年变化趋势. PLOS One。我们向大堡礁海域的原住民传统所有者致以敬意，并缅怀、致敬与感谢历代、当代及未来的原住民长者。我们认可他们与这片海域持续存在的精神联结。