Towards a better assessment of the ecological status of coastal waters using satellite-derived chlorophyll-a concentrations

Abstract

The application of the new Water Framework Directive (WFD) of the European Union will require a dense and frequent monitoring of chlorophyll-a near the coast. Not counting the transitional water bodies located in the vicinity of estuaries, not less than seventy four coastal water bodies have to be monitored along the coast of the French Atlantic continental shelf and the English Channel. All the available data have to be gathered to implement a comprehensive monitoring scheme. To this purpose, we evaluate the capacity of ocean colour imagery to complete the conventional in situ data set collected in coastal networks. Satellite-derived chlorophyll-a concentration is obtained by the application of a coastal Look-Up-Table to water-leaving radiance of the Sea-viewing Wide Field Instrument Sensor (SeaWiFS) for the 1998-2004 period. Seven years of satellite-derived and in situ chlorophyll-a concentrations are compared at seven representative stations of different water bodies. These comparisons show that the satellite products are reliable in most of the situations studied and throughout the seasons. Then the satellite imagery is used to classify the coastal waters following the eutrophication risk criterion of the WFD. This classification is made according to the percentile-90 of chlorophyll-a calculated during the productive season, from March to October. Despite a lack of sensor coverage over a small fraction of the near shore waters, this work shows that the satellite monitoring can considerably ease the application of the WFD.

Implementing and Innovating Marine Monitoring Approaches for Assessing Marine Environmental Status

“…This is supported by studies in the Baltic Sea (Harvey et al, 2015), also showing the advantages of using satellite remote sensing for monitoring and eutrophication assessment and for the status classifications of water basins. These studies show that this tool can be applied for both national, European and Regional Seas monitoring plans as well as the implementation of the MSFD and the Water Framework Directive (Gohin et al, 2008;Novoa et al, 2012). In summary, the use of remote sensing can be an efficient tool providing a synoptic view of the products (e.g., phytoplankton biomass), showing their distribution over an extended period, identifying seasonal patterns and showing the effect of changes in marine ecosystems promoted by human pressures and by environmental changes.…”

Using MERIS data to assess the spatial and temporal variability of phytoplankton in coastal areas

“…Traditionally, monitoring has been achieved through conventional in situ measurements (Moore et al 2009). During the past three decades (McKinna 2015), the use of other methods, such as satellites, mostly used in open sea areas, has increased also in coastal areas as the methods to account for optical parameters, such as chl-a, SPM and coloured dissolved organic matter (CDOM) have largely been improved (IOCCG 2000;Gohin et al 2008;Blondeau-Patissier et al 2014a). In this study we have used chl-a as an example to illustrate the spatiotemporal variability of dynamical processes in a coastal area using the satellite data from the MERIS archive and how it can be used as a complement to traditional in situ monitoring and vice versa.…”

“…Therefore, in situ data is a fundamental requirement for ocean colour products validation and for confirming the reliability of the satellite products. However, through the coordinated use of both types of data, an effective monitoring system of coastal water quality can be achieved (Gohin et al 2008).…”

Validation of Cochlodinium Polykrikoides Red Tide Detection Using Seawifs-Derived Chlorophyll-a Data With Nfrdi Red Tide Map in South East Korean Waters

“…SeaWiFS standard algorithm has good performance for clear waters (Case 1) and it is well known that this algorithm generated overestimation at coastal turbid water (Gohin et al 2005). The suspended material concentration can be deduced from the reflectance at 555 nm, R[555], as reported for the Bay of Biscay seawaters (Froidefond et al 2002).…”