The research group is working with questions concerning the turnover of nutrients in marine systems, focusing primarily on the Baltic Sea. This also includes the loading of nutrients from land and air and its relation to human activities. Methods used include budget calculations, mechanistic models, empirical models and empirical correlation analysis.

BNI participates continuously in national and international projects aiming to understand the environmental problems in the Baltic Sea and show the consequences of different courses of action using marine modelling, for example through Nordic co-operation, the Banos consortium (formerly Bonus) and The Baltic Marine Environment Protection Commission, Helcom.

The Nest system

The Baltic Nest Institute is responsible for maintaining and developing the Nest system, that was first developed in the eight year (1999-2006) program MARE (Marine Research on Eutrophication – a scientific base for cost-effective measures for the Baltic Sea). Baltic Nest provides data and information from the entire Baltic drainage basin and the entire Baltic Sea, and links measures on land with effects to the sea. The system consists of several models, for example Baltsem and Sanbalts, the large Baltic Environmental Database (BED and the Data Assimilation System (DAS) that together generate support for decision-making.

Baltic Nest can be used to calculate required actions needed to attain politically agreed targets for the Baltic Sea ecosystem. The main focus of the model is on eutrophication and the flows of nutrients from land to sea. The system has played an instrumental role in the development of HELCOM Baltic Sea Action Plan, by identifying the nutrient reductions necessary to achieve the goal of a Baltic Sea unaffected by eutrophication.

The Nest system is freely available online at nest.su.se and can be used in an expert mode and a management mode.

Baltsem model

The Baltsem model (BAltic sea Long-Term large Scale Eutrophication Model) is a key component of the Nest system and also frequently used independently in different types of research projects. Baltsem simulates seasonal ecosystem dynamics driven by all the major transport mechanisms and nutrient biogeochemical fluxes in the Baltic Sea, which is presented as a chain of 13 highly vertically resolved but horizontally averaged water columns and underlying sediments. 

Implementation of Baltsem include the simulation of  the long-term development of the Baltic eutrophication since 1850 and participation in ensemble modelling of the climate change projections. The model is also used as generator of the input data for various kinds of benthic and food-web modelling.

An expansion of Baltsem, Baltsem-C, broadens the use to include not only nutrient cycling, but also the inorganic carbon system and several classes of organic carbon. This development enables several new model applications, such as possibilities to estimate how pH in the Baltic Sea responds to future land loads, changing climate, and increasing atmospheric CO2 levels as well the opportunity to trace terrestrial organic carbon in the system and determine land-ocean-atmosphere connections in terms of carbon cycling.

Another expansion, Baltsem-POP includes the transport and fate of organic contaminants and enables model simulations of the future distribution of such chemicals. The model allows for short- and long-term variation in important factors such as carbon cycling, water flows, wind speed, water and air temperature.

PLC water hosting

BNI is also hosting the HELCOM PLC-water database and maintains and develops user interfaces to up- and download data to this data base.

Compilations of pollution load data, provided by the contracting parties, have been an integral part of HELCOM assessment system since 1987, focusing on annual and periodic assessments of inputs of nutrients and selected hazardous substances.

The PLC datasets forms the basis of Pollution Load Compilation reports, that are produced every sixth year. Currently the work is underway to compile the PLC-8 – an assessment of the water- and airborne inputs of nutrients and selected hazardous substances and their sources to the Baltic Sea during the period 1995-2022.

The PLC database can be accessed at nest.su.se/helcom_plc

Technical reports and scientific publications from BNI are found below.