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Abstract The limits on primary production vary in complex ways across space and time. Strong tests of clear conceptual models have been instrumental in understanding these patterns in both terrestrial and aquatic ecosystems. Here we present the first experimental test of a new model describing how shifts from nutrient to light limitation control primary productivity in lake ecosystems as hydrological inputs of nutrients and organic matter vary. We found support for two key predictions of the model: that gross primary production (GPP) follows a hump‐shaped relationship with increasing dissolved organic carbon (DOC) concentrations; and that the maximum GPP, and the critical DOC concentration at which the hump occurs, are determined by the stoichiometry and chromophoricity of the hydrological inputs. Our results advance fundamental understanding of the limits on aquatic primary production, and have important applications given ongoing anthropogenic alterations of the nutrient and organic matter inputs to surface waters.
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Exploring the mismatch between the theory and application of photosynthetic quotients in aquatic ecosystems
Abstract Estimates of primary productivity in aquatic ecosystems are commonly based on variation in , rather than . The photosynthetic quotient (PQ) is used to convert primary production estimates from units of to C. However, there is a mismatch between the theory and application of the PQ. Aquatic ecologists use PQ = 1–1.4. Meanwhile, PQ estimates from the literature support PQ = 0.1–4.2. Here, we describe the theory on why PQ may vary in aquatic ecosystems. We synthesize the current understanding of how processes such as assimilation and photorespiration can affect the PQ. We test these ideas with a case study of the Clark Fork River, Montana, where theory predicts that PQ could vary in space and time due to variation in environmental conditions. Finally, we highlight research needs to improve our understanding of the PQ. We suggest departing from fixed PQ values and instead use literature‐based sensitivity analyses to infer C dynamics from primary production estimated using .
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- PAR ID:
- 10418907
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography Letters
- Volume:
- 8
- Issue:
- 4
- ISSN:
- 2378-2242
- Page Range / eLocation ID:
- p. 565-579
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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