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De Senerpont Domis L.N.,Netherlands Institute of Ecology | Elser J.J.,Arizona State University | Gsell A.S.,Netherlands Institute of Ecology | Huszar V.L.M.,Federal University of Rio de Janeiro | And 17 more authors.
Freshwater Biology | Year: 2013

1.Different components of the climate system have been shown to affect temporal dynamics in natural plankton communities on scales varying from days to years. The seasonal dynamics in temperate lake plankton communities, with emphasis on both physical and biological forcing factors, were captured in the 1980s in a conceptual framework, the Plankton Ecology Group (PEG) model. 2.Taking the PEG model as our starting point, we discuss anticipated changes in seasonal and long-term plankton dynamics and extend this model to other climate regions, particularly polar and tropical latitudes. Based on our improved post-PEG understanding of plankton dynamics, we also evaluate the role of microbial plankton, parasites and fish in governing plankton dynamics and distribution. 3.In polar lakes, there is usually just a single peak in plankton biomass in summer. Lengthening of the growing season under warmer conditions may lead to higher and more prolonged phytoplankton productivity. Climate-induced increases in nutrient loading in these oligotrophic waters may contribute to higher phytoplankton biomass and subsequent higher zooplankton and fish productivity. 4.In temperate lakes, a seasonal pattern with two plankton biomass peaks - in spring and summer - can shift to one with a single but longer and larger biomass peak as nutrient loading increases, with associated higher populations of zooplanktivorous fish. Climate change will exacerbate these trends by increasing nutrient loading through increased internal nutrient inputs (due to warming) and increased catchment inputs (in the case of more precipitation). 5.In tropical systems, temporal variability in precipitation can be an important driver of the seasonal development of plankton. Increases in precipitation intensity may reset the seasonal dynamics of plankton communities and favour species adapted to highly variable environments. The existing intense predation by fish on larger zooplankters may increase further, resulting in a perennially low zooplankton biomass. 6.Bacteria were not included in the original PEG model. Seasonally, bacteria vary less than the phytoplankton but often follow its patterns, particularly in colder lakes. In warmer lakes, and with future warming, a greater influx of allochthonous carbon may obscure this pattern. 7.Our analyses indicate that the consequences of climate change for plankton dynamics are, to a large extent, system specific, depending on characteristics such as food-web structure and nutrient loading. Indirect effects through nutrient loading may be more important than direct effects of temperature increase, especially for phytoplankton. However, with warming a general picture emerges of increases in bacterivory, greater cyanobacterial dominance and smaller-bodied zooplankton that are more heavily impacted by fish predation. © 2012 Blackwell Publishing Ltd. Source

Boll T.,University of Aarhus | Boll T.,University of Southern Denmark | Balayla D.,University of Aarhus | Andersen F.O.,University of Southern Denmark | And 3 more authors.
Hydrobiologia | Year: 2012

Restoration of shallow lakes to a clear-water state, often characterized by high submerged macrophyte cover and a high proportion of piscivores such as perch, Perca fluviatilis L., frequently involves removal of a large proportion of the zoobenthivorous fish, such as bream, Abramis brama L., and roach, Rutilus rutilus L. (i. e. biomanipulation). However, establishment of submerged macrophytes is often delayed following fish removal. This is unfortunate because plant beds typically host high densities of the macroinvertebrates constituting the diet of small perch and thus help perch to go through the bottleneck from feeding on macroinvertebrates to feeding on fish. Establishment of artificial plant beds may be a useful tool to enhance macroinvertebrate population growth and thus food resources for small perch until the natural plants have established. To investigate this restoration option, we studied during two growing seasons (June-October) the composition and abundance of the macroinvertebrate community in artificial plant beds installed in shallow Lake Væng (Denmark) comprising the initial phase of a biomanipulation effort by fish removal. Lake areas with artificial plant beds exhibited substantially higher macroinvertebrate densities than the lake bottom. This suggests that artificial plant beds may be used as feeding grounds for small perch, similarly to the well-known refuge effect for zooplankton against fish predation. In this way, artificial plant beds could help maintain a clear-water state during the transient period when natural submerged vegetation is not yet established in the lake. © 2011 Springer Science+Business Media B.V. Source

Boll T.,University of Aarhus | Boll T.,University of Southern Denmark | Johansson L.S.,University of Aarhus | Lauridsen T.L.,University of Aarhus | And 7 more authors.
Hydrobiologia | Year: 2012

Change in the abundance of benthic macroinvertebrates and the stable isotope composition (C, N) of benthic invertebrates and zooplankton in Lake Vaeng, Denmark, was investigated over an 18-year period following biomanipulation (removal of cyprinids). During the first nine years after biomanipulation, the lake was clear and submerged macrophytes were abundant; after this period, a shift occurred to low plant abundance and high turbidity. Two years after the biomanipulation, total density of benthic macroinvertebrates reached a maximum of 17042 (±2335 SE) individuals m -2 and the density was overall higher when the lake was in a clear state. Redundancy analysis (RDA) suggested macrophyte abundance and total nitrogen (TN) concentration were the dominant structuring forces on the benthic macroinvertebrate assemblage. Stable isotope analysis revealed that δ 13C of macroinvertebrates and zooplankton was markedly higher in years with high submerged macrophyte abundance than in years without macrophytes, most likely reflecting elevated δ 13C of phytoplankton and periphyton mediated by a macrophyte-induced lowering of lake water CO 2 concentrations. We conclude that the strong relationship between macrophyte coverage and δ 13C of macroinvertebrates and cladocerans may be useful in paleoecological studies of past changes in the dynamics of shallow lakes, as change in macrophyte abundance may be tracked by the δ 13C of invertebrate remains in the sediment. © 2012 Springer Science+Business Media B.V. Source

Trochine C.,University of Aarhus | Trochine C.,CONICET | Guerrieri M.E.,University of Aarhus | Liboriussen L.,University of Aarhus | And 4 more authors.
Freshwater Biology | Year: 2014

We studied nutrient limitation of periphytic algae (henceforth periphyton) in 24 mesocosms simulating shallow lakes with two nutrient levels, enriched (with added nitrogen, N, and phosphorus, P) and unenriched (control), and three temperature scenarios, ambient, A2 from the Intergovernmental Panel on Climate Change (IPCC) and A2 + 50%. Periphyton growth (measured as chlorophyll a) was investigated four times in situ using nutrient-diffusing substrata. The effect of grazing was also manipulated using exclusion cages. We found that periphyton responded differently to nutrient addition bioassays (N and P) depending on the background nutrient concentration and warming scenario. Our results indicate that single-nutrient limitation prevailed for periphyton in our experimental temperate shallow lakes. The responses were season sensitive. Periphyton in the unenriched mesocosms were P-limited in early summer in the ambient and A2 scenarios, N-limited in late summer in these two climate scenarios, not nutrient-limited in autumn and P-limited in spring in all climate scenarios. Periphyton in the A2 + 50% scenario showed a positive response to N and P added together in early summer. In contrast, periphyton in the enriched mesocosms showed no clear nutrient limitation, except for short-term periods of P limitation in the warmer systems. Grazers did not affect the quantitative response of periphyton to nutrient addition, and the concentrations of P and N as well as mean monthly temperature were the main environmental factors driving P or N limitation. We conclude that warming in low-productivity lakes affects the seasonality of N limitation and changes the single-nutrient limitation of periphyton into NP co-limitation. This last observation suggests that warming reduces the sensitivity of temperate shallow lakes to bottom-up perturbations. © 2014 John Wiley & Sons Ltd. Source

Iglesias C.,University of the Republic of Uruguay | Iglesias C.,University of Aarhus | Meerhoff M.,University of the Republic of Uruguay | Meerhoff M.,University of Aarhus | And 14 more authors.
Hydrobiologia | Year: 2016

Differences in trophic web structure in otherwise similar ecosystems as a consequence of direct or indirect effects of ambient temperature differences can lead to changes in ecosystem functioning. Based on nitrogen and carbon stable isotope analysis, we compared the food-web structure in a series of subtropical (Uruguay, 30–35°S) and temperate (Denmark, 55–57°N) shallow lakes. The food-web length was on average one trophic position shorter in the subtropical shallow lakes compared with their temperate counterparts. This may reflect the fact that the large majority of subtropical fish species are omnivores (i.e., feed on more than one trophic level) and have a strong degree of feeding niche overlap. The shapes of the food webs of the subtropical lakes (truncated and trapezoidal) suggest that they are fuelled by a combination of different energy pathways. In contrast, temperate lake food webs tended to be more triangular, likely as a result of more simple pathways with a top predator integrating different carbon sources. The effects of such differences on ecosystem functioning and stability, and the connection with ambient temperature as a major underlying factor, are, however, still incipiently known. © 2016 Springer International Publishing Switzerland Source

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