Spearheaded by Researcher Brita Sundelin, and receiving extensive support from Researcher Gastón Alurralde, and Professor Elena Gorokhova, all from the Department of Environmental Science at Stockholm University, this initiative stands as a testament of strong dedication to understand and protect marine ecosystems.

The beginning of the Baltic Sea monitoring program dates back to the aftermath of environmental crises, leading to an international consensus on the necessity of continuous marine observations. Sundelin, whose academic journey began amidst the echoes of the Tsesis oil spill in 1977, reminisced about the early days, “When I started my PhD, our first fieldwork coincided with the aftermath of the Tsesis oil spill. Following this, there emerged an international realization that different methodologies had to be included in the national marine national monitoring program." This need for diverse comprehensive methods laid the groundwork for a program to monitor biological effects that would span decades, the longest running marine monitoring program of this kind in Europe to date. 

The sentinel species

At the core of these monitoring efforts are the amphipods Monoporeia affinis and Pontoporeia femorata, which are shrimp-like crustaceans that are vital for assessing ecosystem status. Alurralde, who joined the program in 2021, explains this choice as a focal point, "The choice of these species was deliberate. Their reproductive malformations serve as a direct signal of chemical pollution and other environmental stressors, such as hypoxia. We monitor these species in the winter, as it's when embryo development takes place." Sundelin further elaborates on their importance, "They're not just indicators of pollution; they're a critical component of the food web. Their high lipid content makes them an excellent food source for fish and other invertebrates."

Brita Sundelin. Photo: Karin Bergman

The program's methodology, involving sleds for sediment sample collection and detailed laboratory analysis of amphipod embryos, have illuminated trends in embryo malformations linked to pollutants and climate change, providing key insights into the adaptability of wild populations in the Baltic Sea to anthropogenic pressures. This methodological approach, standardized and replicated across the Baltic region, underscores a commitment to consistency in environmental monitoring. 

Photo: Karin Bergman

The amphipods are isolated from the sediment and examined in the lab. Photo: Karin Bergman

Their diligent efforts have paid off. “Adopting embryo aberrations as indicators for environmental status assessment within the Marine Strategy Framework Directive marked a pivotal moment. It underscores the acknowledgment of biological effects as integral components of environmental and human health protection policies,”Gorokhova remarks.

Advancements in molecular biomarkers

The introduction of molecular biomarker analysis in recent years has further enriched the program, allowing for a more detailed examination of the biological impacts of environmental stressors. This approach draws a direct parallel to a medical check-up as Gorokhova explains," Just as a doctor orders blood tests or X-rays to gain insights into a patient's health, we conduct diagnostic assessments of marine animals using biochemical and molecular markers, such as enzymes, DNA, and metabolites. By examining the health status of these organisms, we can assess population prospects and overall environmental quality."

Giulia Martela, Gastón Alurralde and Hoishing Lo on their way to Askö Laboratory to begin sediment collection in winter 2023. Photo: Gastón Alurralde

Among notable biomarkers are DNA adducts, which are modifications of DNA molecules signaling the presence of harmful chemicals. These modifications can lead to mutations in marine organisms, potentially altering their health and reproductive potential. Other biomarkers serve as indicators for assessing organism exposure to different contaminant groups. For example, the enzyme acetylcholinesterase indicates neurological damage from organophosphate, carbamate pesticides, and certain nerve agents (both in amphipods and in humans). This link aids in understanding the impact of environmental toxins on organisms.

Professor Elena Gorokhova. Photo:Private

Molecular biomarkers in marine organisms can reveal the subtlest signs of environmental stress, analogous to detecting early symptoms of disease in humans. "Thanks to advancements in technology, such as mass spectrometry, image analysis, and exposomics, we're able to assess a wide array of health indicators. The real intellectual challenge is interpreting this data to ascertain whether an organism is healthy or under stress," Gorokhova notes. Her work on molecular biomarkers has been instrumental in enabling a more targeted approach to marine conservation. 

The future of Baltic Sea monitoring is bright 

As Sundelin is at the twilight of her career, she maintains a hopeful outlook on the future of   the program, buoyed by the promise of technological advances and ongoing research to enhance our understanding of the Baltic Sea's health. Alurralde agrees, "The integration of artificial intelligence for image analysis and further exploration into molecular biomarkers, contaminant distribution, and climate factors could significantly enhance our understanding of the Baltic's health and its response to environmental stressors."

The expansion of the Baltic Sea biomonitoring program, with more Baltic countries coming on board in tracking biological effects using the same methods, epitomizes the power of diligent inquiry and collective effort in confronting environmental challenges.