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Description
The productivity of marine ecosystems is an important factor conditioning element and organic matter cycling on Earth. It also influences the composition of the atmosphere and thus to shape our climate. The world’s oceans are a great source of O2 and sink for atmospheric CO2. They absorb about 22% of anthropogenic CO2 emissions and therefore limit global warming. The Arctic Ocean, due to its relatively high productivity and low water temperatures enhances CO2 solubility, is responsible for as much as 5-14% of the global CO2 uptake by marine regions. This makes the Arctic marine ecosystems important components in the global carbon cycle. Recent findings show that Arctic fjords are especially effective in absorbing atmospheric CO2. The biogeochemistry of the fjord systems is, however, very complex and not yet fully understood. The great unknowns that remain include the effect of glacial retreat on the CO2 budget of coastal waters. This research project is truly interdisciplinary and wide-ranging, with marine sedimentology, hydrography, biogeochemistry, ecology, land hydrology with glaciology fields providing a much-needed holistic approach to the whole system. Simultaneous marine measurements are planned in closely located catchments having similar bedrock but different stages of the glacial recession (tidewater, land-based and lack of glacier). A comprehensive approach to the investigation of nutrient cycling, beginning from delivery from land to the marine environment, to the marine production and utilization, will be performed. Finally, because the goal of the project is aiming at studying the real, on-going process that is expected to affect the whole Arctic coastal ecosystems, the planned research is a kind of natural experiment of the crucial problem that the Earth system is now facing.
Summary of project results
The productivity of marine ecosystems plays a crucial role in the Earth''s matter circulation. Through photosynthesis, oxygen (O2) is produced, while oceans absorb significant amounts of carbon dioxide (CO2), particularly during periods of high productivity when surface waters are supersaturated with O2 and unsaturated with CO2. This exchange influences atmospheric composition and climate. The Arctic Ocean absorbs approximately 5-14% of marine CO2 due to its productivity and cold temperatures, with Arctic fjords being particularly effective in CO2 absorption. Glacial retreat from climate warming alters biogeochemical processes as glaciers supply freshwater, minerals, organic matter, and nutrients to fjord waters, though exchanges with the open sea may decrease due to complex coastlines. Tidewater glaciers are vital for nutrient supply, enhancing marine primary and secondary production, while land-based glaciers provide less favorable conditions for growth. Further glacier recession will significantly impact oceanographic, sedimentological, and biogeochemical conditions.
The RAW project highlighted differences in physical and biogeochemical properties among bays influenced by glaciers at different recession stages. A critical factor was the underwater sill that restricts water exchange; more primary production was noted in bays with land glaciers due to suspended sediment limiting light for photosynthesis. The project suggested that increased fjord area from glacial retreat could positively impact primary production. Knowledge from the project was shared with the public through a webinar, a dedicated website, and a popular science film.
The RAW project is currently in progress despite the shortened duration of 28 months and ongoing laboratory analyses. We anticipate that the outcomes will significantly influence both scientific and related disciplines through six main objectives:
1. **Hydrochemistry and Sedimentation Assessment:** We are analyzing sedimentation processes in the fjord and their biogeochemical implications using CTD with Turbidity sensors and advanced optical methods (LISST and UVP) during fieldwork in 2023. This research aims to enhance our understanding of estuary processes in polar fjord environments.
2. **Nutrient Distribution Analysis:** Sediment and water samples collected during cruises will help determine nutrient flux from land, glaciers, and seas, crucial for estimating nutrient budgets and their burial in fjords.
3. **Bioavailability of Nutrients:** We are evaluating the bioavailability of nutrients in seawater through sediment and seawater samples collected across a salinity gradient from source to sea, focusing on transport and bioavailability.
4. **Sedimentation Rates and Nutrient Recycling:** Monitoring in Hornsund will estimate sediment burial near glaciers versus open fjord transport, along with sedimentation rates of nutrients and organic carbon influenced by wave action.
5. **Plankton Community Comparison:** Samples of photo- and heterotrophic protists were collected to compare structures and primary productivity between tidewater and land-based glacier areas across different seasons, assessing the impact of environmental gradients.
6. **Nutrient Transfer in Food Webs:** By analyzing protist and zooplankton samples in relation to sediment and nutrient data, we will evaluate the plankton community''s role in nutrient cycling and its response to glacier and river influences.
These objectives collectively aim to enhance our understanding of marine ecosystems affected by glacial and river inputs.
Our findings reveal significant variations in hydrography across the different bays in Hornsund Fjord, driven by distinct water circulation patterns and the morphology of the seabed. This underscores the unique ecological complexity of the fjord. The underwater sill plays a crucial role in managing the transport of sediments and micronutrients into the open fjord, which effectively influences nutrient distribution and enhances the ecological balance of this vital marine environment.
Notably, we discovered that the distribution of micronutrients is primarily influenced by geological factors rather than the type of glacier (whether it is tidewater or land-based). This highlights the importance of understanding regional geology in marine studies.
We characterized the dynamics of organic matter and identified both seasonal and regional variability, which is essential for understanding nutrient cycles within the fjord. Our analysis of marine snow aggregates has shown significant variation over time, suggesting a dynamic food base for higher trophic levels. Furthermore, our evaluation of marine plankton community structures indicates that diversity is mainly influenced by temporal factors rather than geographical ones, emphasizing the need for continuous monitoring of these communities.
Interestingly, primary production in Hornsund Fjord exceeds that of other fjords in West Spitsbergen, presenting opportunities for enhanced fishery resources. We observed greater primary production associated with the Gasbreen land-based glacier compared to the Hansbreen tidewater glacier, as evidenced by both chlorophyll-a levels and direct 14C measurements, which could impact local biodiversity.
It is crucial to address the potential decline in primary production due to increasing concentrations of suspended sediments, as this could affect the entire marine food web. Conversely, the ongoing recession of tidewater glaciers may expand the fjord’s areas, potentially promoting increased primary production and benefiting the overall marine ecosystem.
These findings not only deepen our understanding of the Hornsund Fjord ecosystem but also highlight the urgent need for continued monitoring and research to protect and manage this vital resource.
Summary of bilateral results
Two world-leading experts from Norwegian institutions were invited to carry out the RAW project - Western Norway University of Applied Sciences. The RAW project established a new long-term cooperation between Polish and Norwegian research groups. There are several application submitted to ensure future cooperation.