I. Meruma¹*, M. Erberveld² , L. Enserink²

¹ Utrecht University, Netherlands; ² Rijkswaterstaat, Netherlands

^* Corresponding author: Isis.meruma@rws.nl

Introduction

Eutrophication in coastal areas of the North Sea occurs due to excessive growth of phytoplankton, which is caused by an increase in nutrient inflow. It leads to deterioration of water quality, diminishes light permeability, and causes anoxia. Chlorophyll-a is used as proxy for determining phytoplankton mass and is therefore important for the monitoring and assessment of Eutrophication within European frameworks such as Water Framework Directive (WFD) and Marine Strategy Framework Directive (MSFD). (Prins & Enserink, 2023) The EU working group ECOSTAT focusses on the ecological status of water bodies and is working on new monitoring strategies such as the use of satellites for Chlorophyll-a measurements. Traditionally, these concentrations have been determined by in-situ measurements. Although, by using Remote sensing as monitoring strategy, the temporal and spatial scale increases significantly. (Steltzer & Van Der Zande, 2023) 

Studies in 2012 already showed that Remote sensing could also be used in coastal areas, which has been confirmed by WaterInsight and RBINS Brockman Consult. (Steltzer & Van Der Zande, 2023) They used data from sentinel-2 (100m resolution) and sentinel-3 (1km resolution). Even so, in situ measurements are needed to validate this satellite data.  

Objective and Methods

The aim of this research is to evaluate how in situ measurements and satellite data can be combined to monitor the chlorophyll-a concentrations in coastal zones, especially in the Dutch coastal areas. Firstly, an examination will be done on past and current developments within Rijkswaterstaat concerning the monitoring of eutrophication in Dutch coastal zones. With that, the possibilities of using satellites Sentinel-2 and Sentinel-3 in the coastal areas will be explored. Furthermore, existing in-situ measuring methods are examined, such as sampling with ships, ferryboxes or drones whereafter chlorophyll-a will be analyzed with HPLC. Then, to obtain valid match up data for the satellites, logistics of in-situ measurements are determined by examining factors such as season variability, optical water types, water flows, and weather conditions.   

Results

(Expected results) 

An overview of existing methods for in-situ measurements of chlorophyll-a in coastal areas will be presented.  Furthermore, the current development of satellite data determining chlorophyll-a concentrations in coastal areas within Europe and the Netherlands will be presented.  

References

Prins, T., & Enserink, L. (2023). Concentrations of Chlorophyll-a in the Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast. The 2023 Quality Status Report for the Northeast Atlantic. 

Steltzer, K. & Van Der Zande, D. (2023). EODATABEE Service RWS. Brockmann Consult, Royal Belgian Institute of Natural Sciences