A Typology for Reef Passages

Coral reefs host exceptionally diverse and abundant marine life. Connecting coasts and sheltered lagoons to the open ocean, reef passages are important yet poorly studied components of these ecosystems. Abiotic and biotic elements ‘pass’ through these reef passages, supporting critical ecological processes (e.g. fish spawning). Reef passages provide multiple social and ecological benefits for islands and their peoples, but are so far neither characterized nor recognized for their multifaceted significance. This study investigated 113 reef passages across nine Pacific islands (Fiji, New Caledonia, Vanuatu). GIS-based visual interpretations of satellite imagery were used to develop criteria to define three distinct types, mainly based on distance to coastline and presence/absence of an enclosed water body. The discussion identifies ways to refine and augment this preliminary typology as part of a research agenda for reef passages. With these next steps, this typology will be extendable to other regions to better document reef passages and their various roles, supporting biodiversity conservation and sustainable fisheries management

Typology approach from visual interpretation of satellite imagery for reef passages around 9 South Pacific islands

Data was collected as part of the SOCPacific project. Dealing with challenges of the pandemic and travel restrictions, project participants aimed to develop a typology of reef passages based on visual interpretation of freely available satellite imagery. Nine islands of different sizes and shapes surrounded by coral reef structures were selected based on previous field expertise. Reef passages were mapped in GoogleEarth and further processed in QGIS (version 3.16) and R (version 3.5.3). In addition, outlines for the selected islands were downloaded from the GADM database (gadm.org). Parameters distance to coast, minimal width of the passage and the assigned type were added to the dataset. Passages were assigned one of three types defined in Breckwoldt et al. (in review) - Coastal, Lagoon or Open Ocean - depending on the geomorphological appearance of the reef and distance to the coast

A Typology for Reef Passages

Coral reefs host exceptionally diverse and abundant marine life. Connecting coasts and sheltered lagoons to the open ocean, reef passages are important yet poorly studied components of these ecosystems. Abiotic and biotic elements ‘pass’ through these reef passages, supporting critical ecological processes (e.g. fish spawning). Reef passages provide multiple social and ecological benefits for islands and their peoples, but are so far neither characterized nor recognized for their multifaceted significance. This study investigated 113 reef passages across nine Pacific islands (Fiji, New Caledonia, Vanuatu). GIS-based visual interpretations of satellite imagery were used to develop criteria to define three distinct types, mainly based on distance to coastline and presence/ absence of an enclosed water body. The discussion identifies ways to refine and augment this preliminary typology as part of a research agenda for reef passages. With these next steps, this typology will be extendable to other regions to better document reef passages and their various roles, supporting biodiversity conservation and sustainable fisheries management