OBSERVER: May 2021 Product and Ocean Monitoring Indicators release improve water quality monitoring

The May 2021 catalogue update of the Copernicus Marine Service features products of Sentinel 2 and 3 that improve water quality monitoring. Moreover the Ocean Monitoring Indicators (OMI) were updated with three indicators, one of which covers chlorophyll concentrations in the Atlantic using satellite and in situ observations. 

Monitoring of ocean colour is important for understanding the ecology and health of the ocean, as well as for creating informed policy and management systems. Ocean colour is a proxy for chlorophyll-a concentration and particularly in coastal areas, high levels of chlorophyll-a can be an indicator of harmful algal blooms. The detection of such conditions is important for a variety of actors, that are in charge of monitoring and controlling environmental regulations, implementing directives and water management, as well as for blue economy activities such as, tourism, aquaculture or fisheries.

Until recently, Copernicus Marine’s ocean colour products were based on multi-sensor and Sentinel-3A data at a resolution of 1 km × 1 km. The latest release offers higher resolution, an important tool for those working in coastal areas and industries. There are now ocean colour products at regional scales for the Arctic Ocean, Atlantic Ocean, Mediterranean Sea, Black Sea and Global Sea based on high resolution (300 m × 300 m) Sentinel-3A and -3B data. 

In addition, the Atlantic Eutrophication Ocean Monitoring Indicator was released. This indicator is extracted from observations and monitors eutrophication for the North Atlantic. . Eutrophication is the over-enrichment of water by nutrients, such as nitrogen and phosphorus, and it has become one of the major concerns in terms of water quality as it includes harmful algal blooms and oxygen depletion. 

Process of Eutrophication and the impacts. Source: Copernicus Marine Service / Mercator Ocean International

Eutrophication is one of the more long-lasting water quality problems in Europe and is at the forefront of most European Directives on water-protection. Efforts to reduce anthropogenically-induced pollution resulted in the implementation of the Water Framework Directive (WFD) in 2000. Eutrophication leads to increased growth of plant material in an aquatic body. Anthropogenic activities, such as farming, agriculture, aquaculture and industry, are the main source of nutrient input in problem areas.

Eutrophication is an issue particularly in coastal regions and areas with restricted water flow, such as lakes and rivers. The impact of eutrophication on aquatic ecosystems is well known: nutrient availability boosts plant growth – particularly algal blooms (invasive algae that are potentially toxic)– resulting in a decrease in water quality. This can, in turn, cause death by hypoxia of aquatic organisms, ultimately driving changes in community composition. Eutrophication has also been linked to changes in the pH and depletion of inorganic carbon in the aquatic environment. 

Algae blooms in the Baltic Sea - contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO

Oligotrophication, a lesser known phenomenon that can also be destructive, is the opposite of eutrophication. Reduction in some limiting resource leads to a decrease in photosynthesis by aquatic plants, reducing the capacity of the ecosystem to sustain the higher organisms in it. 

To detect eutrophication, information on nutrients and chlorophyll-a concentrations are needed. Data from Sentinel-3A and -3B data are now being used to update the nutrient distribution information for the Atlantic Ocean and, combined with the updated phytoplankton information, an accurate eutrophication indicator for the Atlantic is now available.

This article focuses on ocean data products that support the monitoring of water quality. However, the May 2021 updates include a variety of other products and indicators across the blue (physical), white (sea ice), and green (biogeochemical) ocean.

Find out more:
-    May 2021 Product Release
-    May 2021 OMI Release