Change search
ReferencesLink to record
Permanent link

Direct link
Effects of nutrients and physical lake characteristics on bacterial and phytoplankton production: a meta-analysis
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We performed a meta-analysis compromising of field (300 studies) and experimental data (249 studies) from a wide range of lake trophic states and locations. We examined the effects of nitrogen (N), phosphorus (P), carbon (dissolved organic matter) (C (DOM)), temperature, latitude, and lake morphometry on the absolute and relative rates of primary production (PPr) and bacterial production (BP). We compared areal and volumetric rates of PPr, BP and BP:PPr, and differences between experimental and natural systems. Both field studies and experimental results showed tight agreement with regard to N and P as predictors of volumetric PPr and BP respectively. This was despite the large variation in study length, size and nutrient addition rates in experimental systems, and indicates that bacteria and phytoplankton do not seem to be competing for the same nutrients. Areal production measurements were more difficult to model and were more dependent on physical lake characteristics than nutrients. Temperature was positively correlated with PPr, but not with BP. BP:PPr was stable across experiments regardless of N, P, DOM, or glucose additions. In contrast, BP:PPr ratios varied greatly in the field data set and were highest in systems with low total N and at high latitudes. This pattern was driven by reduced PPr, not increased BP, therefore experimenters may need to manipulate PPr to change BP:PPr. Collectively, our results indicate that increased temperatures and N availability due to climate change will lead to higher PPr and lower BP:PPr, potentially decreasing the importance of energy mobilized through the microbial food web on a global scale.

URN: urn:nbn:se:umu:diva-43462OAI: diva2:414048
Available from: 2011-05-02 Created: 2011-05-02 Last updated: 2011-05-02Bibliographically approved
In thesis
1. Productivity and carbon transfer in pelagic food webs in response to carbon, nutrients and light
Open this publication in new window or tab >>Productivity and carbon transfer in pelagic food webs in response to carbon, nutrients and light
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Some of the major problems we face today are human induced changes to the nitrogen (N), phosphorus (P) and carbon (C) cycles. Predicted increases in rainfall and temperature due to climate change, may also increase dissolved organic matter (DOM) inflows to freshwater ecosystems in the boreal zone. N, P, C and light, are essential resources that most often limit phytoplankton (PPr) and bacterial production (BP) in the pelagic zone of lakes. PPr and BP not only constitute the total basal C resource for the pelagic aquatic food web, but also influence ecosystem function and biogeochemical cycles.

In this thesis I studied how N, P, C and light affect the relative and absolute rates of PPr and BP, along a wide latitudinal and trophic gradient using published data, and in two in situ mesocosm experiments in a clear water oligotrophic lake. In the experiments I manipulated bottom-up drivers of production and top-down predation to examine how these factors interact to affect pelagic food web structure and function.

The most important predictors of PPr globally (Paper I) were latitude, TN, and lake shape. Latitude alone explained the most variation in areal (50%) and volumetric (40%) PPr. In terms of nutrients PPr was primarily N-limited and BP was P-limited. Therefore bacteria and phytoplankton were not directly competing for nutrients. BP:PPr was mostly driven by PPr, therefore light, N, temperature and other factors affecting PPr controlled this ratio. PPr was positively correlated with temperature, but not BP, consequently, higher temperatures may reduce BP:PPr and hence the amount of energy mobilised through the microbial food web on a global scale.

In papers II and III interaction effects were found between C-additions and top-down predation by young-of-the-year (YOY) perch. Selective predation by fish on copepods influenced the fate of labile C-addition, as rotifer biomass increased with C-addition, but only when fish were absent. Interaction effects between these top-down and bottom-up drivers were evident in middle of the food web, which is seldom examined in this type of study. Although the energy pathway from bacteria to higher consumers is generally longer than from phytoplankton to higher trophic levels, increased BP still stimulated the biomass of rotifers, calanoid copepods and YOY fish. However, this appeared to be mediated by intermediate bacterial grazers such as flagellates and ciliates.

Light was an important driver of crustacean zooplankton biomass (paper IV), but the light:nutrient hypothesis was inadequate to predict the mechanisms behind the decrease in zooplankton biomass at low light. Instead, it appeared that reduced edibility of the phytoplankton community under low light conditions and reduced BP most strongly affected zooplankton biomass. Thus, the LNH may not apply in oligotrophic lakes where PPr is primarily N-limited, Daphnia is rare or absent and mixotrophic phytoplankton are abundant.

N, P, C and light manipulations have very different effects on different parts of the pelagic food web. They influence the relative rates of PPr and BP, affect phytoplankton community composition, alter the biomass of higher trophic levels and change pathways of energy transfer through the pelagic food web. This thesis adds valuable information as to how major changes in these resources will affect food web structure and function under different environmental conditions and future climate scenarios.

Place, publisher, year, edition, pages
Umeå: Institutionen för ekologi, miljö och geovetenskap, Umeå universitet, 2011. 33 p.
bacterial production, phytoplankton production, mesocosms, food webs, carbon, nutrients, light
National Category
Research subject
urn:nbn:se:umu:diva-43467 (URN)978-91-7459-191-0 (ISBN)
Public defence
2011-05-26, KBC-huset, Stora Hörsalen, Umeå Universitet, Umeå, 10:00 (English)
Lake ecosystem response to environmental change
Available from: 2011-05-05 Created: 2011-05-02 Last updated: 2011-05-02Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Faithfull, CarolynBergström, Ann-Kristin
By organisation
Department of Ecology and Environmental Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 151 hits
ReferencesLink to record
Permanent link

Direct link