A multitude of anthropogenic pressures deteriorate the Baltic Sea, resulting in the need to protect and restore its marine ecosystem. For an efficient conservation, comprehensive monitoring and assessment of all ecosystem elements is of fundamental importance. However, the holistic assessment of the Baltic Sea is hindered by gaps within the current monitoring schemes. These monitoring gaps need prioritization and they need to be closed by applying novel methods.

As an international consortium of researcher from Sweden, Germany and Finland we have (1) identified and prioritized these gaps, and (2) identified novel methods and matched these with the identified gaps.

To identity and prioritize gaps, we used three sources of information; scientific articles, project reports and a stakeholder survey in order to identify gaps in relation to requirements set by the HELCOM's Baltic Sea Action Plan, the Marine Strategy Framework Directive and the Water Framework Directive.

In addition, twenty-two novel methods with the potential to fill some of these gaps and improve the monitoring of the Baltic marine environment were examined. We asked key stakeholders to point out methods likely to improve current Baltic Sea monitoring. We then described these methods in a comparable way and evaluated them based on their costs and applicability potential (i.e., possibility to make them operational), i.e. we rated novel methods regarding their ability to improve the Baltic Sea monitoring. Methods were assessed with respect to their costs and applicability.

Published articles

Mack, L., Attila J., Aylagas E., Beermann A., Borja A., Hering D., Kahlert M., Leese F., Lenz R., Lehtiniemi M., Liess A., Lips U., Mattila O.P., Meissner K., Pyhälahti T., Setälä O., Strehse J. S., Uusitalo L., Willstand Wranne A. and Birk S. (2020) A synthesis of marine monitoring methods with the potential to enhance the status assessment of the Baltic Sea. Frontiers in Marine Science in press doi: 10.3389/fmars.2020.552047

Kahlert M., Eilola K., Mack L., Meissner K., Sandin L., Strömberg H., Uusitalo L., Viktorsson L. and Liess A. (2020) Gaps in current Baltic Sea environmental monitoring – Science versus management perspectives. Marine Pollution Bulletin in press

Our study shows that the most frequently mentioned gap was that key parameters are not sufficiently monitored in space and time. Biodiversity monitoring was the category containing most gaps. However, whereas more than half of the gaps in reports related to biodiversity, scientific articles pointed out many gaps in the monitoring of pollution and water quality. An important finding was that the three sources differed notably with respect to which gaps were mentioned most often.

Of the methods identified to fill the gaps, twelve methods require low to very low costs, while five require moderate and two high costs. Seventeen methods were rated with a high to very high applicability, whereas four methods had moderate and one low applicability for Baltic Sea monitoring. All methods can potentially increase data resolution or

monitor novel ecosystem elements. We recommend the following novel methods for the Baltic status assessment as methods with both low costs and a high applicability: These include the Manta Trawl, Rocket Sediment Corer, Argo Float, Artificial Substrates, Citizen Observation, Earth Observation, the HydroFIARpH system, DNA Metabarcoding and Stable Isotope Analysis.

In conclusion, gap prioritization for management should be conducted in a careful manner and after carefully considering the different viewpoints of scientists and stakeholders.

There are also many novel methods with the potential to fill current gaps at a range of implementation costs.