N-limited consumer growth and low nutrient regeneration N:P ratios in lakes with low N deposition
2015 (English)In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 6, no 1, 9Article in journal (Refereed) Published
Nutrient limitation of primary producers and their consumers can have a large influence on ecosystem productivity. The nature and strength of nutrient limitation is driven both by external factors (e.g., nutrient loading) and internal processes (e.g., consumer-driven nutrient regeneration). Here we present results from a field study in 10 low productive headwater lakes in northern subarctic Sweden, where nitrogen (N) deposition is low and phytoplankton is primarily N-limited. We assessed the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of seston and zooplankton and estimated the N:P ratio of consumer-driven nutrient regeneration. Based on stoichiometric models, the estimated elemental imbalances between seston and zooplankton suggest that zooplankton were mainly N-limited and regenerated nutrients with low N:P ratios (median 11.9, atomic ratio). The predicted N:P regeneration ratios were consistent with results from phytoplankton nutrient limitation bioassays in mid-summer, i.e., the N:P regeneration was predicted to be low when phytoplankton were N-limited, and high when phytoplankton were P-limited. During other seasons, when water discharge was high, nutrient loading from the surrounding catchments apparently had the strongest effect on phytoplankton nutrient limitation. We propose that lakes with higher N:P ratios than the open ocean is an effect of N deposition, that N-limitation of consumers and phytoplankton is further enhanced by low nutrient regeneration N:P ratios, and that in the absence of N deposition, lake and ocean N:P stoichiometry are similar.
Place, publisher, year, edition, pages
2015. Vol. 6, no 1, 9
consumer driven nutrient cycling, ecological stoichiometry, nitrogen, nutrient limitation, phosphorus, ytoplankton, zooplankton
IdentifiersURN: urn:nbn:se:umu:diva-102480DOI: 10.1890/ES14-00333.1ISI: 000350440400009OAI: oai:DiVA.org:umu-102480DiVA: diva2:808205