Macroalgal assemblages on rock substrata
Macroalgal assemblages are iconic on rocky substrata around the world’s coasts (seen here at Maria Island, Tasmania, Australia) in both the intertidal and subtidal zones. Credit: Patricia Miloslavich

Macroalgal assemblages are highly productive and biodiverse ecosystems providing important functions and services, including provision of nursery areas, human food resources, and protection from coastal erosion. Macroalgal assemblages are vulnerable to global threats such as ocean warming and acidification and to other anthropogenically mediated stressors, including habitat degradation, eutrophication, pollution, overfishing, and invasive species. Macroalgal cover and composition were identified as an “essential ocean variable” in recognizing that the condition of macroalgal assemblages provides an important indicator of coastal ecosystem health. Proper baseline data and sustained monitoring are essential to detecting changes in these communities at global scales.

To develop a global, coordinated strategy for macroalgal monitoring, 30 international, multidisciplinary experts met in Hobart, Australia, (1) to identify existing data sets at all geographical scales, (2) to review technological monitoring approaches and define standard operating procedures (SOPs), (3) to recommend approaches to consolidate existing data and associated metadata in a data system under the principles of Findable, Accessible, Interoperable, and Reusable data, and (4) to plan the implementation of an international, standardized, innovative, and cost-effective system for monitoring macroalgae.

Metadata on nearly 80 networks revealed that spatial and temporal sampling heterogeneity, methodological variability, data availability and format, and sustainability of data collection are critical challenges. The most spatiotemporally extensive time series for rocky intertidal systems is from the United Kingdom and France, extending back to 1950, and is known as the Marine Biodiversity and Climate Change Project. In North America and Europe, a wide variety of monitoring occurs but without a consistent methodology. A few individual programs are underway in South America, with one regional but intermittent effort (South American Research Group on Coastal Ecosystems) spanning from the Caribbean to Patagonia. In China, there is no national monitoring program, and knowledge of macroalgal ecosystems derives from short-term projects targeted to investigate biodiversity. With the exception of South Africa, the African continent has little to no monitoring. The most comprehensive database for macroalgae is the global kelp data held in the Kelp Ecosystem Ecology Network, which covers around 1,400 sites, but these data are also heterogeneous in temporal extent and have significant sampling gaps. Some data are also available through the Ocean Biogeographic Information System (OBIS).

Macroalgal species in Tasmania, Australia
The high diversity of species that form fascinating macroalgal communities is manifested in highly variable shapes, sizes, and growth forms, making standardization of methods and data comparability a challenge. Pictured is a variety of macroalgal species on the intertidal rocky shore on Maria Island, Tasmania, Australia. Credit: Patricia Miloslavich

The capabilities, strengths, and weaknesses of different methods, including visual census, acoustics, laser imaging, remote sensing from satellites, molecular tools (including environmental DNA), and imagery (stills, automated/remote vehicles, drones), were evaluated considering data availability, level of expertise required, feasibility of implementation, training requirements, spatial scale, and taxonomic resolution. A flexible, fit-to-purpose SOP was drafted for many of these approaches to be made available through the OceanBestPractices platform. To integrate existing and future data, a data management architecture was proposed. This architecture will allow standards-based data and metadata from multiple sources to be harvested in a centralized global data repository linked with OBIS through Web services. New data templates for each of the monitoring methods, along with vocabularies for each variable recorded, nontaxonomic categories, methods, instruments, and units, will need to be developed and registered.

The participant list, presentations, and workshop report acknowledging the sponsors are available on the website. We thank the participants and sponsors for their contributions.

—Patricia Miloslavich (, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia; also at Departamento de Estudios Ambientales, Universidad Simón Bolívar, Caracas, Venezuela; Craig Johnson, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia; and Lisandro Benedetti-Cecchi, University of Pisa, Italy


Miloslavich, P.,Johnson, C., and Benedetti-Cecchi, L. (2019), Keeping a watch on seaweeds: The forests of the world’s coasts, Eos, 100, Published on 09 January 2019.

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