Browsing by Author "Schaedig, Eric"

The Baltic Sea is a unique and delicate brackish water ecosystem with high primary productivity driven by oceanic biogeochemical cycles of oxygen, iron, silicon, nitrogen and phosphorus. Elevated anthropogenic nutrient loading into the Baltic ecosystem has resulted in a large-scale increase in destructive cyanobacterial blooms in the open Baltic Sea over the past century. The toxic cyanobacterium Nodularia spumigena is a major component of surface blooms in the open Baltic Sea and continues to bloom even after the depletion of phosphate from the surrounding waters. This phenomenon has been attributed to an ability to scavenge phosphorus from recalcitrant sources. However, the exact phosphorus species that sustain N. spumigena growth in the Baltic Sea remain largely unknown. Here, I employ a comparative genomics approach to determine the evolutionary dynamics of phosphorus scavenging in eight strains of N. spumigena and predict the range of phosphorus sources that may support their growth. Then, I test these predictions by growing six strains of N. spumigena on a number of potentially bioavailable phosphorus sources. Among the phosphorus scavenging genes identified by the genomic analysis, putative pathways for the enzymatic degradation of phytic acid, phosphite, and phosphonates were present and highly conserved in the species. Subsequent growth experiments demonstrated that the organism may grow using phytic acid and phosphite, as well as the phosphonates methylphosphonic acid, ethylphosphonic acid, and nitrilotris(methylenephosphonic acid), as sole phosphorus sources. These results indicate that N. spumigena blooms may be supported by several phosphorus sources previously not known to contribute to eutrophication in the Baltic Sea. While additional growth experiments and further research on the environmental prevalence of these compounds are necessary, the findings presented in this study expand our knowledge of how N. spumigena dominates phytoplankton blooms in a phosphorus-scarce environment and may help to inform future eutrophication mitigation efforts in the Baltic Sea region.