Blomqvist, S. Department of Systems Ecology, sven.blomqvist@system.ecology.su.se

 
BIOGEOCHEMICAL DISTRIBUTION PATTERNS OF IRON AND PHOSPHATE IN FRESHWATER AND MARINE SYSTEMS ARE RELATED TO NUTRIENT LIMITATION
 
Both phosphate and iron tend to accumulate in anoxic bottom waters, due to release from sediments and sinking particles. In these waters, during the subsequent shift to oxic conditions, the Fe/P ratio is crucial, as it will determine the efficiency of the iron mediated scavenging of phosphorus. Chemical data reveal that it takes at least two irons to bind each phosphorus into the solid phase and, consequently, systems with a relative iron deficiency (Fe/P < 2) are characterized by high levels of dissolved phosphate remaining mobile in solution. Anthropogenic as well as natural factors might affect the development of different Fe/P ratios in anoxic waters. Our findings from studies in freshwater and marine environments, in combination with data from the literature, demonstrate fundamental cross-system trends in the distribution of iron and phosphate. Marine systems are typically characterized by a relative low supply of iron and Fe/P ratios below 2, whereas, freshwater commonly have ratios above 2. Also, there is a gradient of increasing Fe/P ratios from eutrophic to oligotrophic systems. Hence, the Fe/P ratio is a key concept for better understanding of biological productivity and eutrophication processes induced by human activity. This applies to freshwater as well as brackish marine systems. Also, the Fe/P ratio is a forcing function explaining reported differences in nutrient limitation of phytoplankton in these systems.
 
Day: Tuesday, Feb. 2
Time: 12:00 - 12:15pm
Location: Sweeney Center
 
Code: SS07TU1200S