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Description
The main aim of BUFFER project is to investigate the impact of the interaction between climatic anomalies and eutrophication on the capacity of the sediments to process and retain nutrients and contrast their regeneration to the water column (the buffer capacity). BUFFER will analyze if and how the capacity of sediments to control eutrophication consequences is menaced by climate change and will disentangle underlying mechanisms. The main study site of BUFFER is the Gulf of Gdańsk (southern Baltic Sea), as it has been threatened by the combined effects of climate change and eutrophication. BUFFER project will investigate the buffer capacity of specific areas in the Gulf along multiple gradients of oxygen availability, freshwater input, depth and light. The buffer capacity will be also analyzed with respect to the presence of different organisms, including primary producers as aquatic plants and algae and different functional groups of macrofauna, including filter-feeding bivalves and burrowing worms, to understand whether living macroorganisms also represent a natural buffer. Sampling campaigns will be carried out in two additional sites: the Sacca di Goro lagoon in Italy and the Kongsfjorden and Porsangerfjorden in Norway. Both sites are affected by high freshwater discharge, the former from the Po River and the latter from the ice melt from land, and both sites can encounter bottom water anoxia. The comparison among study areas will allow to understand whether the climate-eutrophication effects produce larger impacts in the northern latitudes.Results from BUFFER will allow to outline the impacts of climatic anomalies and eutrophication along a wide latitudinal gradient and the quantification of how local biogeochemical buffers are affected by such anomalies. Furthermore, BUFFER will identify the critical zones in the Gulf of Gdańsk in terms of limited or null buffer capacity of the benthic system.
Summary of project results
In recent decades, human activities such as aquaculture, agriculture, and farming have exerted significant adverse impacts on aquatic ecosystems spanning from river networks to coastal areas. One prominent consequence of these anthropogenic pressures is the occurrence of eutrophication, characterized by an overabundance of nutrients, particularly nitrogen and phosphorus, in water bodies. Coastal regions receive substantial nutrient inputs from terrestrial sources, but they also exhibit mechanisms, known as coastal filters, which either permanently remove or temporarily retain nutrients and organic matter. The efficiency of these coastal filters depends on various factors including nutrients and organic matter transport timing, water residence time, temperature, dissolved oxygen levels, as well as the diversity and abundance of primary producers and fauna. Eutrophication is notably severe in certain coastal areas of the Baltic Sea and Mediterranean Sea regions, and its severity is compounded by ongoing climate change. Climate anomalies such as intense precipitation events can augment nutrients transport to coastal zones, while prolonged heatwaves can foster water stratification and warming. The combined impacts of eutrophication and climate change present a global challenge affecting coastal environments'' biodiversity, functionality, and recreational and economic significance.
The primary objective of the "Benthic coastal buffers against climatic and eutrophication extremes (BUFFER)" project was to examine how the interplay between climate change and eutrophication influences the capacity of sediment to process and retain nutrients, thereby regulating their release into the water column (referred to as buffer capacity). The study focused on two specific regions: the Gulf of Gdańsk in the southern Baltic Sea, Poland, and the Goro Lagoon in the North Adriatic Sea, Italy. These areas are both susceptible to the combined impacts of climate change and eutrophication. Flash flood events are possible throughout various seasons in these regions, while summers often bring prolonged drought periods. The Gulf of Gdańsk experiences the influence of a variable and wind-driven plume from the Vistula River, while the Goro Lagoon, connected to the Adriatic Sea through a 3 km wide mouth, exhibits significant salinity variations due to freshwater inputs from the Po River.
BUFFER’s research was carried out in different sedimentary environments in Gulf of Gdańsk (Poland) and Goro Lagoon (Italy). Several cruises (8) and coast sampling campaigns (4) were conducted in the Gulf of Gdańsk and 4 sampling campaigns took place in Goro Lagoon. Each sampling consisted of the collection of water, intact sediment cores and fauna samples. The analyses included investigation of hydrological conditions, bottom water oxygen concentration and dissolved nutrients concentration in bottom and pore waters, as well as sediment and benthic macrofauna characteristics. We compared two seasons the spring and the summer, with high and low nitrate levels, respectively. We carried out incubations of intact sediment along physico-chemical (e.g., depth and oxygen or organic matter availability), biological (e.g., benthic fauna traits, primary producers’ growth forms) gradients to understand if these sediments have the capacity to buffer the regeneration of nutrients to the water column. BUFFER project applied a multielement (nitrogen, silicon and phosphorus) approach and analysed how sedimentary biogeochemical buffers guarantee a balanced regeneration of the three macronutrients.
Findings from BUFFER project demonstrated that both coastal areas, Gulf of Gdańsk and Goro Lagoon, are affected by eutrophication and ongoing climate change. The exhaustion of the phosphorus buffer capacity in summer may be enhanced by climate-dependent heat accumulation in the water mass, leading to water stratification. The higher temperatures could intensify nutrient regeneration, fueling algal growth with consequences for the entire ecosystem. Such effect interacts with that produced by eutrophication due to increased sedimentary organic matter content and mineralization. On the other hand, spring river discharge can be affected by climate change due to different precipitation timing and intensity, interacting with runoff and nitrate delivery to the coastal zones. Our results demonstrated that both coastal systems have a great capacity to dissipate nitrogen even under high river discharge and nutrient loads. On the contrary, in summer, climate-driven drought and low river discharge act on riverine eutrophication and estuarine water renewal, with cascade effects on oxygen availability. These results demonstrated the negative effects of climate change on coastal zones and the importance of controlling the source of nutrients from the watershed before they reach the open sea.
Findings from BUFFER project provide insights into sustainable strategies for the management of coastal ecosystems. These insights are particularly relevant for addressing the challenge of nutrient enrichment in coastal zones, which is crucial for maintaining their ecological integrity. Our research has significant implications for coastal management on a global scale, especially for similar aquatic environments facing similar threats. By conducting sampling across diverse areas within both study regions, we gained insights into the multitude of factors that contribute to the deterioration of the aquatic system''s health. This comprehensive approach allowed us to discern specific stressors and their spatial variations, providing a deeper understanding of the complex dynamics influencing aquatic ecosystem health. Adopting effective ecosystem-based management approaches is essential for preserving biodiversity, supporting fisheries, and maintaining the equilibrium of coastal ecosystems. Human-induced nutrient enrichment, resulting from activities like agricultural runoff, presents significant risks such as algal blooms, oxygen depletion, and habitat degradation. Furthermore, BUFFER project''s outcomes provide actionable insights for policymakers, environmental agencies, researchers, and stakeholders involved in coastal resource management and conservation efforts. By integrating these findings into policy frameworks and management strategies, we can effectively mitigate the adverse impacts of nutrient enrichment and enhance the resilience of coastal ecosystems in the face of ongoing environmental challenges. Indeed, to enhance the ecological condition of these ecosystems and render them less vulnerable to the impacts of climate change, an action at the watershed level is imperative. This involves implementing changes and improvements in agricultural and farming practices aimed at reducing nutrient loads originating from terrestrial environments, ultimately reaching coastal zones. Additionally, promoting the conservation and restoration of coastal zones, especially macrophytes meadows, that act as natural filters, effectively trapping and removing excess nutrients before they reach open sea. By addressing nutrient pollution at its source and implementing holistic watershed management approaches, we can mitigate the exacerbation of eutrophication and other adverse impacts on coastal ecosystems, fostering their resilience in the face of climate change.