Abstract
Abstract. The Primeiras and Segundas Archipelago Reserve is a recently established marine protected area, the largest in Africa, located in the waters of Northern Mozambique. This protected area is of significant local economic importance and global ecological relevance, containing the southernmost coral reefs in Eastern Africa. However, information related to the marine ecosystem, notably benthic habitat is very scarce. Twelve atolls were mapped in the region using object-based image classification of very-high resolution satellite imagery (IKONOS, Quickbird, and WorldView-2). Geographically referenced data on benthic cover and depth were gathered in the course of three fieldwork expeditions covering a total of four atolls and two shallow reef structures in the Segundas Archipelago. The resulting map allows the estimation of three distinct types of coral cover (field, patches, spurs and grooves); the differentiation of sand, rubble and rock substrate; and the detection of seagrass and brown macroalgae, identifying up to 24 benthic habitats. Average overall accuracy was above 50%. The high variability of the optical properties on the reef systems, in large due to the connectivity with the mainland via plumes, while interesting from an ecological perspective increases the challenges for remote sensing of bottom cover. New information indicates the presence of deep benthic cover extending from the atolls, suggesting the need for further research on Coastal Eastern African corals, namely on their resilience and connectivity, and supporting current knowledge of the existence of an almost continuous coral reef from Kenya to Mozambique. Coral and fish biodiversity data have been analysed together with the satellite-derived maps. Results support the local perception that ecosystems are in decline and uncover new information about biodiversity’s spatial patterns. Our work provides a detailed depiction of marine habitats that may aid the management of the protected area, namely in the definition of fishing zones and coral cover monitoring.
Highlights
The Primeiras and Segundas Archipelagos, Mozambique, together with part of the coastline, were declared Environmental Protected Area in November 2012
At the geomorphological level (L1), each location is classified into lagoon, reef crest, fore reef, deep reef and shallow water
All islands present a very similar geomorphological structure – a flat lagoon with shallow water on the northern side, surrounded by reef crest, fore reef and deep reef, the last usually extending towards southeast
Summary
The Primeiras and Segundas Archipelagos, Mozambique, together with part of the coastline, were declared Environmental Protected Area in November 2012. In the 2012 UNEP report of the Southern Indian Ocean Regional Workshop to Facilitate the Description of Ecologically or Biologically Significant Marine Areas, the Primeiras and Segundas are said to belong to “the largest and [to be] among the most productive fisheries areas in Mozambique, attaining close to 50% of the entire industrial catches”, “with probably the most pristine coral reefs in Mozambique”, being “important for connectivity between northern and southern reefs” (CBD 2013). The project to create benthic habitat maps for the region, initiated by WWF-Germany and supported by ESA’s G-ECOMON initiative, aimed to increase knowledge of the spatial distribution of reef ecosystems, and support improved management and planning. By integrating existing biodiversity data with the newly created maps, further knowledge can be acquired, and unknown spatial patterns uncovered, contributing to a more complete and comprehensive portrait of local ecosystem
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