Physical and Biological Characteristics of Seagrass Bed Off Porto Novo (Santo Antao, Cabo Verde

Abstract

Seagrass meadows are known for their ecosystem services and functions, including biodiversity. Four species have recently been documented in the West African Marine Eco Region (WAMER): Cymodocea nodosa, Halodule wrightii, Ruppia maritima and Zostera noltei. Cabo Verde seagrass now has a new record on Santo Antão Island since the first record on Santiago Island in 2016. Therefore, there is a need to document the meadow off Porto Novo (Santo Antão), including physical and biological parameters, as well as the fish. To describe the physical and biological properties of the seagrass bed we: 1) used underwater imaging tools (Oktopus inspection camera device and the PlasPi standing camera) for mapping; physical descriptions, and biodiversity observation, with a focus on macro and megafauna, 2) a multiparameter probe EXO2 to measure physicochemical conditions of the water column on the seagrass bed and 3) a questionary addressed to stakeholders involved in seagrass monitoring, to investigate the conservation status of seagrass in Cabo Verde. The seagrass Halodule wrightii was found at an average depth of 7 meters, on the sandy bottom, covering 164.994 m2 along the east coast of the island between 17°0196264N, 25°0427160W and 17°027341N, 25°028557W. The average temperature in the seagrass habitat was 24°C, and the average salinity was 35.5 PSU; the average dissolved oxygen was 7.4mg/l and chlorophyll-a average concentration was 0.4μg/l. Four different species of fish (Sphoeroides marmoratus, Stephanolepis hispidus, Gymnothorax vicinus, Pegusa cadenati) were present in the grass meadow, a species of green algae (Avrainvellea sp) and red algae (Asparagopsis taxiformis spp) are recorded on the seagrass. Regarding the seagrass conservation and state in the country, no concrete measures have been taken since then, and all achievements on seagrass have been knowledge and awareness at different levels and platforms. Santo Antão’s seagrass needs more attention to study their habitat regarding the biology and nekton diversity. Seagrasses of Cabo Verde in general, and Santo Antão especially, need deep documentation and concrete conservation measures.