In aquatic ecosystems, the hidden world beneath the surface plays a vital role in maintaining balance. The sediments at the bottom of rivers, lakes, and lagoons are not just static deposits; They are important activity areas where nutrients such as nitrogen and phosphorus are recycled. These processes involve the breakdown of organic matter and other chemical exchanges and can greatly affect water quality and the health of the entire ecosystem. Understanding how these nutrients move between sediments and overlying water, especially in shallow ecosystems, is key to effectively managing the environment.
Professor José Lopes from the University of Aveiro developed a biogeochemical model for the Ria de Aveiro ecosystem that takes into account biogeochemical interactions at the interface between the water body and the upper layer of bottom sediments. He conducted a modeling study aimed at better understanding the importance of these interactions, particularly those related to nitrogen and phosphorus. The study, published in the Journal of Marine Science and Engineering, fills an important gap in understanding how nutrient exchange affects overall water quality and ecosystem health in shallow water environments.
The model works by simulating how nutrients move between sediment and water, taking into account inputs from natural factors such as river flow, temperature and salt content, which influence nitrogen and phosphorus levels in the water column. This study points out the importance of considering sediments as active layers from a biogeochemical perspective. The new approach considers the upper layers of sediments as key players, releasing or absorbing nutrients through processes such as the breakdown of organic matter. It advocates the need for comprehensive monitoring programs to track environmental parameters and improve understanding of the interactions between the water column and overlying sediments in coastal and marine areas. It also requires a multidisciplinary approach to quantify processes such as sedimentation and bioturbation that are affected by water column activity. Ultimately, this comprehensive framework is critical for effective ecosystem modeling, management, and conservation.
“The results show that the interaction between sediment and water plays an important role in controlling the amount of nitrogen and phosphorus in the water, leading to significant changes in their concentrations,” Professor Lopez explained. The research team used water collected from various sites around the lagoon. The model was tested on real data. They found that nitrogen levels were particularly sensitive to how oxygen and nitrates moved around, while phosphorus levels were more affected by their interactions with iron and other minerals. The findings provide 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. For example, strong river flows increase phosphorus levels in some parts of the lagoon due to the release of nutrients from sediments. Rising temperatures also caused more phosphorus to be released from sediments, but nitrogen levels remained largely stable. The impact of changes in salt content is smaller, but the overall importance of the interaction between sediment and water is evident, especially when rivers bring high levels of nutrients.
Overall, the study highlights the important role these sediment-water interactions play in managing nutrient levels in coastal ecosystems. The findings are particularly important for those who manage water quality and the overall health of ecosystems such as Aveiro Lagoon.
Journal reference
Lopes, JF “Assessing benthic impacts: Effects of pelagic exchange on water column nitrogen and phosphorus status under physical forcing: a simulation study.” Journal of Marine Science and Engineering, 2024.
About the author
Professor Jose Fortes Lopez is a distinguished scholar at the Department of Physics at the University of Aveiro, Portugal, where he has been a faculty member since 1992. PhD in physics from the University of Provence in France, specializing in fluid mechanics and energy-related issues.
Since 1992 he has worked in the Oceanography and Climatology Group of the Department of Physics and is one of the founding members of the modeling group of the Center for Environmental and Marine Studies (CESAM) of the University of Aveiro. His main research focus is on the numerical simulation of hydrodynamic circulation in the coastal and lagoon areas of Aveiro, Portugal. He then talked about several studies on water quality in coastal waters and the impact of climate change on coastal and lagoon ecosystems. Recently, he has been interested in issues related to physical and biogeochemical interactions between the water column and the benthic interface.
Throughout her career, Professor Lopes has published more than 30 peer-reviewed articles in leading scientific journals and contributed to various international conferences. He is involved in several funded research projects.
In addition to his research, Professor Lopes is currently the Director of the BSc Meteoroceanography and Climatology program at the University of Aveiro in Portugal and is very committed to education and guidance related to environmental and climate issues. He teaches undergraduate and graduate courses in general physics, mechanics, fluid mechanics, and multiple topics related to meteorology, oceanography, and climate science, inspiring students to devote their college careers to pressing issues of climate and ecology.
Outside of academia, Professor Lopez is an advocate for nature conservation and often works with non-profit organizations to raise awareness of social issues. He also enjoys writing opinion pieces on a variety of topics related to social issues.
