Variability of chlorophyll-a in Maltese coastal waters

Abstract

Environmental monitoring of open and coastal waters has provided eminent advances, for researchers in areas such as ocean colour technology (Blondeau-Patissier, Gower, Dekker, Phinn and Brando, 2014). Phytoplankton blooms are monitored through satellite ocean colour data sensors which provide a synoptic view of the world oceans, hence, are indicators to the wellness of the marine environment. Thus, the monitoring of algal blooms is a fundamental action for the efficient management of coastal and oceanic resources (Blondeau-Patissier, Gower, Dekker, Phinn and Brando, 2014). The phytoplankton blooms of chlorophyll-a around Maltese coastal waters were monitored and assessed from datasets downloaded from satellite observations, mainly from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Visible Infrared Radiometer Suite (VIIRS) and numerical models, revealing extent from 1 st April 2016 to 30 th April, 2016 for a test case. Moreover, the fieldwork, which consisted of numerous water collection processes, from four locations around the Maltese Islands, led to the extraction of chlorophyll-a in order to compare the resulting data values to data gathered from satellite observations and numerical models. The two satellites have a strong positive relationship; however, a weaker one, when compared to numerical models. Furthermore, methods of analysis were conducted through reflectance spectra computed from a UV spectrophotometer in order to measure in-situ chlorophyll-a concentrations from sampling collections. The method used in this study, allows the ability for further study of phytoplankton ecology due to high spectral resolution. It is clearly shown that the increase in nutrients in the surface layer coming from human activity, wave action and other pollutants leads to the higher levels of chlorophyll-a concentrations in Maltese coastal waters.