In aquatic ecosystems, the hidden world beneath the water’s surface plays a crucial role in maintaining balance. Sediments at the bottom of rivers, lakes, and lagoons are far more than just static deposits; they are vital zones of activity where nutrients like nitrogen and phosphorus are recycled. These processes, which involve the breakdown of organic matter and other chemical exchanges, can dramatically affect water quality and the health of entire ecosystems. Understanding how these nutrients move between the sediment and the water above, especially in shallow ecosystems, is key to managing the environment effectively.
Professor José Lopes from the University of Aveiro has set up a biogeochemistry model for the Ria de Aveiro ecosystem that takes into account biogeochemistry interations at the interface between the water column and the upper layer of the bottom sediment. He carried out a modelling study aimed to better understand the importance of these interactions, particularly in relation to nitrogen and phosphorus. The study, published in the Journal of Marine Science and Engineering, fills an important gap in understanding how the nutrient exchanges influence the overall water quality and ecosystem health in shallow water environments.
The model works by simulating how nutrients move between the sediment and the water, while considering the input of natural factors like river flow, temperature, and salt levels, affect nitrogen and phosphorus levels of the water column. The study points to the importance of treating sediments as an active layer from a biogeochemical point of view. This new approach sees the upper layer of sediments as a key player that can either release or absorb nutrients through processes like the breakdown of organic matter. It advocates for the need for integrated monitoring programs to track environmental parameters and improve understanding of the interactions between the water column and and the upper layer sediments of coastal and marine areas. It calls as well for a multidisciplinary approach to quantify processes like sedimentation and bioturbation, which are influenced by water column activities. Ultimately, this comprehensive framework is vital for effective ecosystem modeling, management, and conservation.
Professor Lopes explained, “The results show that the interactions between the sediment and water play a major role in controlling the levels of nitrogen and phosphorus in the water, causing noticeable changes in their concentrations.” The research team tested the model using real-world data collected from various sites around the lagoon. They discovered that nitrogen levels were especially sensitive to oxygen and how nitrate moves, while phosphorus levels were more influenced by how it interacts with iron and other minerals. These findings offer new insights into how natural forces shape nutrient levels in ecosystems like this one.
River flow and temperature were found to be particularly important in driving changes in nutrient levels. Strong river flow, for instance, increased phosphorus levels in some parts of the lagoon because of the release of nutrients from the sediment. Warmer temperatures also led to more phosphorus being released from the sediment, though nitrogen levels remained mostly stable. The effect of changes in salt levels was smaller, but the overall importance of the interactions between sediment and water was clear, especially when rivers brought in high levels of nutrients.
Overall, the study highlights the vital role that these sediment-water interactions play in managing nutrient levels in coastal ecosystems. These findings are particularly important for those managing water quality and the overall health of ecosystems like the Ria de Aveiro lagoon.
Journal Reference
Lopes, J. F. “Assessing the Influence of the Benthic: Pelagic Exchange on the Nitrogen and Phosphorus Status of the Water Column, under Physical Forcings: A Modeling Study.” Journal of Marine Science and Engineering, 2024. DOI: https://doi.org/10.3390/jmse12081310
About the Author
Professor José Fortes Lopes is a distinguished scholar in the Department of Physics of the University of Aveiro, Portugal, where she has been a faculty member since 1992. He earned his Ph.D. in physics from the University of Provence, France, specializing in fluid mechanics and energetic related issues.
Since 1992, he is working in the ocean and climate meteorology group of the Department of Physics, and he was one of the founding members of the modeling group of the Center for Environmental and Marine Studies (CESAM) of the University of Aveiro. His primary studies focused on the numerical modeling of the hydrodynamic circulation of the Portuguese coastal and lagoon area of the Ria de Aveiro. Then, he addressed several studies on the water quality of coastal waters, as well as on the impact of climate change on coastal and lagoon ecosystems. Lately, he is interested in issues related the physical and biogeochemical interaction between the interfaces of the water column and the benthos.
Throughout her career, Professor Lopes has published over 30 peer-reviewed articles in leading scientific journals and has contributed to various international conferences. He has participated in several funded research projects.
Besides his research, Professor Lopes is now the head of BSc course in Meteorology Oceanography and Climate at the University of Aveiro Portugal, and is very committed to educational and mentorship related to environmental and climate issues. He teaches undergraduate and graduate courses on general physics, mechanics, fluid mechanics, as well as several topics related to meteorology, oceanography and climate sciences, inspiring students to engage their university careers with the pressing issues of climate and ecology.
Outside of academia, Professor Lopes is an advocate for conservation preservation of nature, often collaborating with non-profits organizations to promote awareness about societal issues. He also enjoys writing opinion articles on various topics related to societal issues.
