Using Remote Sensing Data to Monitor Primary Production in Cabo Verde: A Step Towards Smarter Ocean Management

Abstract

More than 70% of the Earth's surface is covered by the ocean, making it the largest expanse (Costanza, 1999). The relationship between ocean ecosystems and global climate change is attracting much attention in recent years (Spring, 2019; Siswanto et al., 2020). As the base of the marine food web, phytoplankton plays a fundamental role in the biogeochemical cycling of elements by con-verting inorganic elements into organic compo-nents. Phytoplankton are advected microalgae and therefore dependent on marine currents. They can photosynthesize using light and nutrients such as NO3 (Nitrate), PO4 (Phosphate), Si (Silicate), Fe (Iron) and carbon dioxide (CO2) available in the water to produce oxygen and organic matter. As primary producers, many marine organisms, including fish, depend on them for their nutrition. They also contribute also to roughly half of the fixed carbon on the planet by absorbing atmospher-ic CO2 and producing 50% of dioxygen (O2) essen-tial for life on the earth’s surface (Martin, 2014). In the current scenario of climate change, a noticeable decrease in primary production on a larger scale has been observed. (Boyce et al., 2010). Chlorophyll-a (Chl-a) is a pigment found in algae and other photosynthetic organisms. Of all the types of chlorophyll, it is Chl-a that serves as a key indicator of phytoplankton biomass in the ocean (Behrenfeld & Falkowski, 1997). While estimating microscopic phytoplankton numbers and associated primary productivity is a significant challenge for ships (Dierssen & Randolph, 2012), satellite remote sensing of ocean color has become a reliable tool to study phytoplankton dynamics over various timescales (Vantrepotte & Mélin, 2009; Krasnopolsky et al., 2016).