NUTRIENT LIMITATION OF NITROGEN FIXATION AND DENITRIFICATION RATES DETERMINED USING NUTRIENT DIFFUSING SUBSTRATES
Denitrifiers are commonly limited by nitrogen (N) and organic carbon (C), whereas N fixers can be limited by phosphorus (P) and suppressed by N. To test how nutrient limitation of these processes differed between adjacent stream and wetland habitats, nutrient diffusing substrates (NDS) were deployed for 28 days on the Pilgrim River in Michigan. NDS were enriched with C, N and P with fritted glass disks for autotrophs and cellulose sponges for heterotrophs (4-way full factorial design). At the stream, denitrification measured using acetylene block was higher on NDS enriched with C but were modulated by N and P (C*N*P interaction F1,22 = 4.7, p = 0.04). N fixation measured using acetylene reduction was not influenced by nutrients but was 2.4 times higher on glass versus sponge (F1,30 = 8.13, p = 0.008). At the wetland, N alone increased denitrification (F1,31 = 41.7, p < 0.001), and N fixation increased with P and decreased with N and C additions (N*P, F1,22 = 6.4, p < 0.02; N*C, F1,22 = 5.8, p < 0.025). Nutrient limitation of processes may vary in close proximity, leading to spatial heterogeneity in biogeochemical cycling.
Erin Eberhard (Co-Presenter/Co-Author), Michigan Technological University , firstname.lastname@example.org;
Kevin Nevorski (Co-Presenter/Co-Author), Michigan Technological University, email@example.com;
Amy Marcarelli (Co-Presenter/Co-Author), Michigan Technological University, firstname.lastname@example.org;
Katie Mazanec (Primary Presenter/Author), Missouri University of Science and Technology, email@example.com;