GLOB Nitrogen gain and loss in changing coastal lagoon ecosystems of the Baltic Sea

Work plan

The 36-month project includes the following joint tasks: fieldwork (10 sampling campaigns covering winter, autumn, spring, and summer—both normal temperature and heat wave conditions), laboratory experiments using samples from the Curonian and Vistula lagoons, laboratory analyses, data processing and interpretation, and dissemination of results in scientific conferences and manuscript preparation. Moreover, an innovative feature of the GLOB project is that all investigators will take part in sampling and establishing the incubation experiments.

The planned research consists of several tasks that need to be performed:

WP1 Project coordination, synthesis and dissemination.This WP addresses activity and task planning, project management, capacity building for young scientists, and dissemination of the research findings.

Task 1.1 Project management, coordination, and organizing meetings and workshops.
Task 1.2 Synthesis of project outcomes.
Task 1.3 Project dissemination.

Milestones:
M1.1 Comparison, processing and statistical analysis of obtained and literature results within tasks 2.1–4.1 (month 30).
M1.2 Data obtained within tasks 2.1–5.1 processed and statistical analysis completed (month 30).
M1.3 Manuscript writing (at least four) completed (month 36).

WP2 The potential of the lagoon to gain N through internal processes.
This WP will address measurements of N₂ fixation in the water column (and possibly in sediments) and estimation of N fluxes across the sediment–water interface. A biogeochemical approach (rate and flux measurements) will be used to estimate the potential of the lagoon to gain N through internal processes across seasons and in response to summer heat waves. Briefly, samples will be incubated in microcosms to analyze ¹⁵N₂ accumulation into biomass and to measure fluxes during intact core incubations.

Task 2.1 Measurements of N₂ fixation and N release from sediments.
Task 2.2 Identification of driving factors.
Task 2.3 Data interpretation and manuscript preparation.

Milestones:
M2.1 Collection and analysis of samples and incubation experiments seasonally (winter, spring, summer and autumn) and during extreme heat events for evaluating N₂ fixation in the water column and sediments completed (month 24).
M2.2 Data interpretation and manuscript preparation (month 36).

WP3 Fate of fixed N through the different dissimilatory microbial pathways.
This WP will focus on fixed N transformations in the water column and sediments through dissimilatory pathways, including denitrification, DNRA and anammox. Samples will be incubated in microcosms to analyze dissimilatory nitrate (NO₃⁻) transformation based on ¹⁵N isotope probing. Additional experiments will assess the potential impact of increased temperature on dissimilatory processes.

Task 3.1 Seasonal measurements of dissimilatory NOx⁻ reduction in water column and sediments.
Task 3.2 Identification of driving factors.
Task 3.3 Data interpretation and manuscript preparation.

Milestones:
M3.1 Collection and analysis of samples seasonally (winter, spring, summer and autumn) and during extreme heat events for evaluation of fixed N reduction processes (denitrification, DNRA, anammox) in the sediment and water column completed (month 24).
M3.2 Data interpretation and manuscript preparation (month 36).

WP4 Taxonomic and functional diversity of microorganisms involved in the N cycle.
Taxonomic diversity and metabolic capabilities of microbiota in lagoons and its response to environmental stressors (temperature, salinity and nutrient availability) will be characterized through metabarcoding, metatranscriptomics and functional gene analyses.

Task 4.1 Profile taxonomic diversity of the microbial community in the water column and sediment environment in winter and summer.
Task 4.2 Assess the metabolic potential of microbial communities in the N cycle in each lagoon.
Task 4.3 Data interpretation and manuscript preparation.


Milestones:
M4.1 Collection and analysis of samples seasonally (winter, spring, summer and autumn) and during extreme heat events (June–September) completed (month 24).
M4.2 Metagenomic analyses completed (month 24).
M4.3 Interpretation and description of obtained data (month 36).

WP5 Reconstruction of N balance.
This WP will focus on monitoring riverine inputs, measured processes and fluxes to reconstruct the N budget in each system. Water samples will be collected from rivers entering the lagoons, from within the lagoons, and, if possible, from lagoon outlets. Combined results will be used to reconstruct the nitrogen cycle within the lagoon systems.

Task 5.1 Monitoring external inputs and integrating measured processes.
Task 5.2 Data interpretation and manuscript preparation.

Milestones:
M5.1 Calculation of measured process rates and mass balances completed (month 24).
M5.2 Reconstruction of N cycling pathways completed (month 36).