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。
本空间研究依托单次调查完成：共在163个礁体的324个点位布设1257条样带，覆盖南纬11.0°至23.6°的近岸至远岸海域，调查水深范围为0至18米，调查工作于1997年至2008年间开展。
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。每条样带对应的环境预测变量分别通过原位实测数据与耦合水动力-生物地球化学模型eReefs获取。
研究发现，在40.4%的近岸调查礁体中，至少有一个点位的大型藻类盖度≥50%，成为底栖生境的优势类群。空间分布上，大型藻类盖度随向岸距离缩短、远离赤道的纬度升高以及水深变浅（≤3米）而显著上升。与大型藻类占据优势相关的环境条件包括：高潮差、强波浪暴露度与高辐照度，以及低文石饱和状态、低塞氏深度（Secchi depth）、总碱度与水温。大型藻类盖度与造礁石珊瑚盖度间的空间竞争证据，仅见于近岸浅水区点位。本研究获取的大量实测数据及其建立的关联关系，可为生态系统模型的参数化提供支撑，并可用于优化并完善基于大型藻类数据的太平洋珊瑚礁礁体健康指数。
本数据集支撑的研究文献为：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》，发表于《PLOS ONE》。
我们向大堡礁海域领地的传统原住民致以敬意，缅怀并致敬其已逝、在世与新晋的长老。我们认可他们与自身海域领地持续存续的精神联结。