| 1. |
- Cherif, Mehdi, 1978-, et al.
(författare)
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An operational framework for the advancement of a molecule-to-biosphere stoichiometry theory
- 2017
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Ingår i: Frontiers in Marine Science. - Lausanne : Frontiers Media S.A.. - 2296-7745. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Biological stoichiometry is an approach that focuses on the balance of elements in biological interactions. It is a theory that has the potential to causally link material processes at all biological levels—from molecules to the biosphere. But the lack of a coherent operational framework has so far restricted progress in this direction. Here, we provide a framework to help infer how a stoichiometric imbalance observed at one level impacts all other biological levels. Our framework enables us to highlight the areas of the theory in need of completion, development and integration at all biological levels. Our hope is that this framework will contribute to the building of a more predictive theory of elemental transfers within the biosphere, and thus, to a better understanding of human-induced perturbations to the global biogeochemical cycles.
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| 2. |
- Deininger, Anne, 1987-
(författare)
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Effects of inorganic nitrogen and organic carbon on pelagic food webs in boreal lakes
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Anthropogenic activities are increasing inorganic nitrogen (N) loadings to lakes in the northern hemisphere. In many boreal lakes phytoplankton are N limited, wherefore enhanced N input may affect the productivity of pelagic food webs. Simultaneously, global change causes increased inflows of terrestrial dissolved organic carbon (DOC) to boreal lakes. Between clear and humic lakes, whole lake primary and consumer production naturally differs. However, research is inconclusive as to what controls pelagic production in these lakes. Further, it is unclear how DOC affects the response of the pelagic food web to enhanced inorganic N availability. The overarching goal of this thesis was to study the effects of inorganic N and organic C for pelagic food webs in boreal lakes. In the thesis, I first identified the main drivers of pelagic production during summer in eight non-manipulated Swedish boreal lakes with naturally low or high DOC. Then I investigated how increased N availability affects the pelagic food chain, and how the response differs with DOC. Therefore, whole lake inorganic N fertilization experiments were conducted in six Swedish boreal lakes across a DOC gradient (low, medium, high) divided into three lake pairs (control, N enriched) with one reference and two impact years. In each lake, I also investigated the response of zooplankton growth using in situ mesocosm experiments excluding planktivores. I found that humic boreal lakes had lower phytoplankton production and biomass than clear water lakes. Further, phytoplankton community composition and food quality differed with DOC. However, high DOC did not reduce pelagic energy mobilization or zooplankton biomass, but promoted a higher dominance of cladoceran relative to copepod species. N addition clearly enhanced phytoplankton biomass and production in the experimental lakes. However, this stimulating N effect decreased with DOC as caused by light limitation. Further, the newly available phytoplankton energy derived from N addition was not efficiently transferred to zooplankton, which indicates a mismatch between producer energy supply and consumer energy use. Indeed, the mesocosm experiment revealed that decreased food quality of phytoplankton in response to N addition resulted in reduced food web performance, especially in clearer lakes. In humic lakes, zooplankton production and food web efficiency were clearly more resilient to N addition. In summary, my thesis suggests that any change in the landscape that enhances inorganic N availability will especially affect pelagic food webs in clear water lakes. In contrast, brownification will result in more lakes being resilient to eutrophication caused by enhanced N deposition.
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| 3. |
- Deininger, Anne, et al.
(författare)
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Nitrogen effects on aquatic food web efficiency in the pelagic zone of unproductive lakes along a gradient of dissolved organic carbon
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Atmospheric nitrogen (N) deposition and terrestrial dissolved organic carbon (DOC) loadings are increasing in northern boreal lakes. However, consequences of increased N availability on food web efficiency (FWE) and consumer growth in N limited unproductive boreal lakes are unclear. Here, we performed in situ mesocosm experiments in late summer (2011; 2013) in six unproductive boreal Swedish lakes, paired across a DOC gradient, with one lake in each pair fertilized with N (2011: reference year; 2012, 2013: impact years). We assessed how zooplankton growth and FWE were affected by changes in pelagic energy mobilization (PEM), food chain length (PP:BP, i.e. phytoplankton: bacterial production ratio), and food quality (seston stoichiometry) in response to N fertilization. Although PP, PEM and PP:BP increased in low and medium DOC lakes after N fertilization, consumer growth and FWE in the low DOC lake were reduced, potentially due to a reduction in phytoplankton food quality (increased C:P; N:P). At high DOC, N fertilization caused modest increases in PP and PEM, with marginal changes in PP:BP and phytoplankton food quality, which combined led to a slight increase in zooplankton growth and FWE. We conclude that the background lake DOC level is critical in order to infer effects of enhanced inorganic N availability on pelagic productivity and FWE. In clear lakes increased N deposition will decrease FWE due to mismatches in food quality demand and supply. In humic lakes this mismatch will not occur, wherefore and zooplankton production and FWE will increase slightly following enhanced N deposition.
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| 4. |
- Deininger, Anne, et al.
(författare)
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Pelagic food web response to whole lake N fertilization
- 2017
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 62:4, s. 1498-1511
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic activities are increasing inorganic nitrogen (N) loadings to unproductive boreal lakes. In many of these lakes phytoplankton are N limited, consequently N fertilization may affect ecosystem productivity and consumer resource use. Here, we conducted whole lake inorganic N fertilization experiments with six small N limited unproductive boreal lakes (three control and three N enriched) in an area receiving low N deposition with one reference and two impact years. Our aim was to assess the effects of N fertilization on pelagic biomass production and consumer resource use. We found that phytoplankton primary production (PP) and biomass, and the PP: bacterioplankton production ratio increased after fertilization. As expected, the relative contribution of phytoplankton derived resources (autochthony) that supported the crustacean zooplankton community increased. Yet, the response in the consumer community was modest with autochthony only increasing in one of the three major zooplankton groups and with no effect on zooplankton biomass. In conclusion, our findings imply that newly available phytoplankton energy derived from N fertilization was not efficiently transferred up to zooplankton, indicating a mismatch between producer energy supply and consumer energy use with potential accumulation of phytoplankton biomass as the result.
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| 5. |
- Deininger, Anne, et al.
(författare)
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Phytoplankton response to whole lake inorganic N fertilization along a gradient in dissolved organic carbon
- 2017
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 98:4, s. 982-994
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Tidskriftsartikel (refereegranskat)abstract
- Global change has increased inorganic nitrogen (N) and dissolved organic carbon (DOC; i.e. ‘browning’) inputs to northern hemisphere boreal lakes. However, we do not know how phytoplankton in nutrient poor lake ecosystems of different DOC concentration respond to increased N availability. Here, we monitored changes in phytoplankton production, biomass and community composition in response to whole lake inorganic N fertilization in six boreal unproductive Swedish lakes divided into three lake pairs (control, N enriched) at three DOC levels (low, medium, high), with one reference year (2011) and two impact years (2012, 2013). We found that phytoplankton biomass and production decreased with DOC concentration before N fertilization. Further, phytoplankton community composition also differed with respect to DOC, with a dominance of non-flagellated autotrophs at low DOC towards an increasing dominance of flagellated autotrophs with increased lake DOC concentration. The N fertilization increased phytoplankton biomass and production in all lakes, but did not affect phytoplankton community composition. However, the net response in biomass and production to N fertilization declined with increasing DOC, implying that the lake DOC concentration is critical in order to infer phytoplankton responses to N fertilization, and that the system switches from being primarily nutrient limited to becoming increasingly light limited with increased DOC concentration. In conclusion, our results show that browning will reduce phytoplankton production and biomass and influence phytoplankton community composition, whereas increased inorganic N loadings from deposition, forestry or other land use will primarily enhance phytoplankton biomass and production. Together, any change in the landscape that enhances inorganic N availability will increase phytoplankton production and biomass, but the positive effects of N will be much weaker or even neutralized in browner lakes as caused by light limitation.
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| 6. |
- Deininger, Anne, et al.
(författare)
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Simulated terrestrial runoff triggered a phytoplankton succession and changed seston stoichiometry in coastal lagoon mesocosms
- 2016
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Ingår i: Marine Environmental Research. - : Elsevier BV. - 0141-1136 .- 1879-0291. ; 119, s. 40-50
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Tidskriftsartikel (refereegranskat)abstract
- Climate change scenarios predict intensified terrestrial storm runoff, providing coastal ecosystems with large nutrient pulses and increased turbidity, with unknown consequences for the phytoplankton community. We conducted a 12-day mesocosm experiment in the Mediterranean Thau Lagoon (France), adding soil (simulated runoff) and fish (different food webs) in a 2 x 2 full factorial design and monitored phytoplankton composition, shade adaptation and stoichiometry. Diatoms (Chaetoceros) increased fourfold immediately after soil addition, prymnesiophytes and dinoflagellates peaked after six- and 12 days, respectively. Soil induced no phytoplanlcton shade adaptation. Fish reduced the positive soil effect on dinoflagellates (Scripsiella, Glenodinium), and diatom abundance in general. Phytoplankton community composition drove seston stoichiometry. In conclusion, pulsed terrestrial runoff can cause rapid, low quality (high carbon: nutrient) diatom blooms. However, bloom duration may be short and reduced in magnitude by fish. Thus, climate change may shift shallow coastal ecosystems towards famine or feast dynamics.
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| 7. |
- Faithfull, Carolyn L., 1982-, et al.
(författare)
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Copepod nauplii use phosphorus from bacteria, creating a short circuit in the microbial loop
- 2019
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Ingår i: Ecology Letters. - : John Wiley & Sons. - 1461-023X .- 1461-0248. ; 22:9, s. 1462-1471
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Tidskriftsartikel (refereegranskat)abstract
- In subtropical oceans phytoplankton carbon: phosphorus (C : P) ratios are high, and these ratios are predicted to increase further with rising ocean temperatures and stratification. Prey stoichiometry may pose a problem for copepod zooplankton nauplii, which have high phosphorus demands due to rapid growth. We hypothesised that nauplii meet this demand by consuming bacteria. Naupliar bacterial and phytoplankton carbon and phosphorus ingestion, assimilation and incorporation were traced using P-33 and C-14 radioisotopes. Bacterial carbon was incorporated four times less efficiently into biomass than phytoplankton carbon. In contrast, bacterial and phytoplankton phosphorus were incorporated at similar efficiencies, and bacteria could meet a substantial amount of naupliar phosphorus requirements. As parts of the ocean become more oligotrophic, bacteria could help sustain naupliar growth and survival under suboptimal stoichiometric conditions. Thus, nauplii may be a shortcut for phosphorus from the microbial loop to the classical food web.
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| 8. |
- Faithfull, Carolyn L., et al.
(författare)
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Food quantity and quality in unproductive clear water and humic lakes and consequences for pelagic mesozooplankton
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 1. Small oligotrophic humic lakes are the most common type of lake in the boreal zone and are predicted to become more abundant with climate change. Humic lakes generally have lower whole lake primary and consumer production than clear water lakes, but research is inconclusive as to what controls pelagic production in these lakes.2. We compared food quantity (primary production (PP) and phytoplankton biomass, pelagic energy mobilization, seston carbon (C)) and food quality (phytoplankton edibility, seston stoichiometry) for crustacean mesozooplankton in four humic (> 15 mg L-1 DOC) and four clear water lakes.3. We found that PP was over three times higher in clear water lakes, and was controlled by nutrient concentrations and temperature, whereas in humic lakes PP was dependant on light availability. Nevertheless, total food quantity (i.e. pelagic energy mobilization, seston C concentrations) was similar between lake types, even though food composition differed. In humic lakes bacterial production based on allochthonous C contributed three times more to total pelagic energy mobilization and seston C consisted of 20% less phytoplankton biomass.4. Food composition did not have any effect on total zooplankton biomass, however, cladoceran: copepod biomass ratios increased with DOC concentration, both in our lakes and in a subset of northern lakes from the Swedish lake monitoring program.5. Our results imply that increased DOC concentrations in boreal lakes will reduce PP and phytoplankton biomass and can alter food composition. However, browning of boreal lakes is unlikely to reduce pelagic energy mobilization or total zooplankton biomass, but can promote a higher dominance of cladocerans relative to copepods, which may have consequences for pelagic planktivorous predators.
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| 9. |
- Faithfull, Carolyn L., et al.
(författare)
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Food web efficiency differs between humic and clear water lake communities in response to nutrients and light
- 2015
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 177:3, s. 823-835
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Tidskriftsartikel (refereegranskat)abstract
- This study demonstrates that clear and humic freshwater pelagic communities respond differently to the same environmental stressors, i.e. nutrient and light availability. Thus, effects on humic communities cannot be generalized from existing knowledge about these environmental stressors on clear water communities. Small humic lakes are the most numerous type of lake in the boreal zone, but little is known about how these lakes will respond to increased inflows of nutrients and terrestrial dissolved organic C (t-DOC) due to climate change and increased human impacts. Therefore, we compared the effects of nutrient addition and light availability on pelagic humic and clear water lake communities in a mesocosm experiment. When nutrients were added, phytoplankton production (PPr) increased in both communities, but pelagic energy mobilization (PEM) and bacterial production (BP) only increased in the humic community. At low light conditions, the addition of nutrients led to increased PPr only in the humic community, suggesting that, in contrast to the clear water community, humic phytoplankton were already adapted to lower ambient light levels. Low light significantly reduced PPr and PEM in the clear water community, but without reducing total zooplankton production, which resulted in a doubling of food web efficiency (FWE = total zooplankton production/PEM). However, total zooplankton production was not correlated with PEM, PPr, BP, PPr:BP or C:nutrient stoichiometry for either community type. Therefore, other factors such as food chain length, food quality, ultra-violet radiation or duration of the experiment, must have determined total zooplankton production and ultimately FWE.
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| 10. |
- Liess, Antonia, et al.
(författare)
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Terrestrial runoff boosts phytoplankton in a Mediterranean coastal lagoon, but these effects do not propagate to higher trophic levels
- 2016
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 766:1, s. 275-291
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Tidskriftsartikel (refereegranskat)abstract
- Heavy rainfall events causing significant terrestrial runoff into coastal marine ecosystems are predicted to become more frequent with climate change in the Mediterranean. To simulate the effects of soil runoff on the pelagic food web of an oligotrophic Mediterranean coastal lagoon, we crossed soil extract addition (increasing nutrient availability and turbidity) and fish presence in a full factorial design to coastal mesocosms containing a natural pelagic community. Soil extract addition increased both bacteria and phytoplankton biomass. Diatoms however profited most from soil extract addition, especially in the absence of fish. In contrast zooplankton and fish did not profit from soil extract addition. Furthermore, our data indicate that nutrients (instead of light or carbon) limited basal production. Presumed changes in carbon availability are relatively unimportant to primary and secondary production in strongly nutrient limited systems like the Thau Lagoon. We conclude that in shallow Mediterranean coastal ecosystems, heavy rainfall events causing soil runoff will (1) increase the relative abundance of phytoplankton in relation to bacteria and zooplankton, especially in the absence of fish (2) not lead to higher biomass of zooplankton and fish, possibly due to the brevity of the phytoplankton bloom and the slow biomass response of higher trophic levels.
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