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Antti P. Eloranta

Bio: Antti P. Eloranta is an academic researcher from University of Jyväskylä. The author has contributed to research in topics: Salvelinus & Brown trout. The author has an hindex of 15, co-authored 40 publications receiving 650 citations.

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TL;DR: This study demonstrates that both interspecific niche segregation between and individual trophic specialisation within generalist fish species can constrain food-web coupling and alter energy mobilisation to top consumers in subarctic lakes.
Abstract: SUMMARY 1. Generalist fish species are recognised as important couplers of benthic and pelagic food-web compartments in lakes. However, interspecific niche segregation and individual specialisation may limit the potential for generalistic feeding behaviour. 2. We studied summer habitat use, stomach contents and stable isotopic compositions of the generalist feeder Arctic charr coexisting with its common resource competitor brown trout in five subarctic lakes in northern Norway to reveal population-level and individual-level niche plasticity. 3. Charr and trout showed partial niche segregation in all five lakes. Charr used all habitat types and a wide variety of invertebrate prey including zooplankton, whereas trout fed mainly on insects in the littoral zone. Hence, charr showed a higher potential to promote habitat and food-web coupling compared to littoral-dwelling trout. 4. The level of niche segregation between charr and trout and between pelagic-caught and littoralcaught charr depended on the prevailing patterns of interspecific and intraspecific resource competition. The two fish species had partially overlapping trophic niches in one lake where charr numerically dominated the fish community, whereas the most segregated niches occurred in lakes where trout were more abundant. 5. In general, pelagic-caught charr had substantially narrower dietary and isotopic niches and relied less on littoral carbon sources compared to littoral-caught conspecifics that included generalist as well as specialised benthivorous and planktivorous individuals. Despite the partially specialised planktivorous niche and thus reduced potential of pelagic-dwelling charr to promote benthic–pelagic coupling, the isotopic compositions of both charr subpopulations suggested a significant reliance on both littoral and pelagic carbon sources in all five study lakes. 6. Our study demonstrates that both interspecific niche segregation between and individual trophic specialisation within generalist fish species can constrain food-web coupling and alter energy mobilisation to top consumers in subarctic lakes. Nevertheless, pelagic and littoral habitats and food-web compartments may still be highly integrated due to the potentially plastic foraging behaviour of top consumers.

91 citations

Journal ArticleDOI
TL;DR: This study highlights that, because they determine the main energy source (littoral vs. pelagic) and the trophic position of generalist top predators, ecosystem size and fish diversity are particularly important factors influencing function and structure of food webs in high-latitude lakes.
Abstract: Prey preference of top predators and energy flow across habitat boundaries are of fundamental importance for structure and function of aquatic and terrestrial ecosystems, as they may have strong effects on production, species diversity, and food-web stability. In lakes, littoral and pelagic food-web compartments are typically coupled and controlled by generalist fish top predators. However, the extent and determinants of such coupling remains a topical area of ecological research and is largely unknown in oligotrophic high-latitude lakes. We analyzed food-web structure and resource use by a generalist top predator, the Arctic charr Salvelinus alpinus (L.), in 17 oligotrophic subarctic lakes covering a marked gradient in size (0.5–1084 km2) and fish species richness (2–13 species). We expected top predators to shift from littoral to pelagic energy sources with increasing lake size, as the availability of pelagic prey resources and the competition for littoral prey are both likely to be higher in large lakes with multispecies fish communities. We also expected top predators to occupy a higher trophic position in lakes with greater fish species richness due to potential substitution of intermediate consumers (prey fish) and increased piscivory by top predators. Based on stable carbon and nitrogen isotope analyses, the mean reliance of Arctic charr on littoral energy sources showed a significant negative relationship with lake surface area, whereas the mean trophic position of Arctic charr, reflecting the lake food-chain length, increased with fish species richness. These results were supported by stomach contents data demonstrating a shift of Arctic charr from an invertebrate-dominated diet to piscivory on pelagic fish. Our study highlights that, because they determine the main energy source (littoral vs. pelagic) and the trophic position of generalist top predators, ecosystem size and fish diversity are particularly important factors influencing function and structure of food webs in high-latitude lakes.

63 citations

Journal ArticleDOI
TL;DR: It is suggested that a strong littoral reliance of fishes can be a feature in subarctic lakes throughout the year and liver could be more commonly used in stable-isotope studies of fish trophic niche shifts instead of using only the less responsive muscle tissue.
Abstract: Seasonal and ontogenetic shifts in the diet of Arctic charr Salvelinus alpinus were studied in a deep, ultra-oligotrophic lake in subarctic Finland from both stomach contents and the stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope compositions of muscle and liver tissues. Both diet and isotope results indicated that the S. alpinus population relied mainly on littoral benthic energy sources. The strong littoral reliance appeared largely independent of season or fish size, although the data lacked small (total length, LT, <130 mm) and young (<3 years) S. alpinus. Liver isotope values of intermediate-sized S. alpinus (200-350 mm), however, suggested exploitation of the increase in the abundance of pelagic zooplankton in the late open-water season. The results suggest that, in general, a strong littoral reliance of fishes can be a feature in subarctic lakes throughout the year. Due to its faster isotopic turnover rate and thus higher resolution for temporal diet changes, liver could be more commonly used in stable-isotope studies of fish trophic niche shifts instead of using only the less responsive muscle tissue.

61 citations

Journal ArticleDOI
TL;DR: Changes along a gradient characteristic of the predicted future environment throughout the subarctic indicate that climate and land use driven eutrophication and browning are radically altering the function and fuelling of aquatic food webs in this biome.
Abstract: Climate change and the intensification of land use practices are causing widespread eutrophication of subarctic lakes. The implications of this rapid change for lake ecosystem function remain poorly understood. To assess how freshwater communities respond to such profound changes in their habitat and resource availability, we conducted a space-for-time analysis of food-web structure in 30 lakes situated across a temperature-productivity gradient equivalent to the predicted future climate of subarctic Europe (temperature +3°C, precipitation +30% and nutrient +45 μg L-1 total phosphorus). Along this gradient, we observed an increase in the assimilation of pelagic-derived carbon from 25 to 75% throughout primary, secondary and tertiary consumers. This shift was overwhelmingly driven by the consumption of pelagic detritus by benthic primary consumers and was not accompanied by increased pelagic foraging by higher trophic level consumers. Our data also revealed a convergence of the carbon isotope ratios of pelagic and benthic food web endmembers in the warmest, most productive lakes indicating that the incorporation of terrestrial derived carbon into aquatic food webs increases as land use intensifies. These results, reflecting changes along a gradient characteristic of the predicted future environment throughout the subarctic, indicate that climate and land use driven eutrophication and browning are radically altering the function and fuelling of aquatic food webs in this biome.

48 citations

Journal ArticleDOI
TL;DR: It is demonstrated that lipid-rich zooplankton can subsidise the predominantly benthivorous diet of top consumers (here Arctic charr) in subarctic lakes and that littoral and pelagic trophic pathways can be highly integrated in high-latitude lakes.
Abstract: Summary Generalist fish species commonly act as important links between littoral and pelagic habitats and food-web compartments in lakes. However, diet and habitat links may depend significantly on seasonal availability of, and qualitative differences between, littoral and pelagic prey and on fish size. Despite increasing interest in food-web dynamics, little is known about the seasonal changes in, or qualitative differences between, littoral and pelagic trophic pathways supporting generalist fish species in high-latitude lakes. We used stomach contents together with analyses of stable carbon and nitrogen isotopes and fatty acids to study the winter and summer diet of generalist Arctic charr and determine the qualitative differences between littoral and pelagic prey items. We were particularly interested to determine whether Arctic charr are able to utilise abundant and lipid-rich winter zooplankton resources in subarctic Lake Saanajarvi, northern Finland. Arctic charr fed actively on cladoceran zooplankton in both seasons, despite the higher abundance and higher lipid content of calanoid copepods. Although the stomach contents consisted mainly of zooplankton in summer, the isotopic compositions of muscle and liver suggest Arctic charr relied more on littoral carbon sources throughout the year. Fatty acid analysis indicated that Arctic charr had lower amounts of body fat and total and essential fatty acids in winter compared with summer. Observed seasonal feeding activity and dietary shifts were partly related to Arctic charr size. Small ( 200 mm) conspecifics that had more seasonally stable feeding activity and diet. Fatty acid analysis indicated that both littoral and pelagic food sources provided similar fatty acids to Arctic charr, but in general, zooplankton had higher percentages of essential fatty acids compared with zoobenthos. Pelagic Eudiaptomus graciloides calanoids and littoral Gammarus lacustris amphipods had the highest concentrations of total and essential fatty acids, but only the latter prey item was found in Arctic charr stomach contents. Our study demonstrates that lipid-rich zooplankton can subsidise the predominantly benthivorous diet of top consumers (here Arctic charr) in subarctic lakes. The results also demonstrate that littoral and pelagic trophic pathways can be highly integrated in high-latitude lakes, as a result of the flexible foraging behaviour of top consumers such as Arctic charr.

42 citations


Cited by
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Journal ArticleDOI
TL;DR: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols used xiii 1.
Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

14,171 citations

01 Jan 2016
TL;DR: People have search hundreds of times for their favorite books like this evolution in changing environments some theoretical explorations, but end up in malicious downloads instead of enjoying a good book with a cup of tea in the afternoon.
Abstract: Thank you very much for reading evolution in changing environments some theoretical explorations. As you may know, people have search hundreds times for their favorite books like this evolution in changing environments some theoretical explorations, but end up in malicious downloads. Rather than enjoying a good book with a cup of tea in the afternoon, instead they juggled with some harmful bugs inside their laptop.

621 citations

Journal ArticleDOI
14 Jul 2020
TL;DR: A review of physical lake variables and their responses to climate change is presented in this paper, where the authors discuss recent and expected lake responses and look towards future research opportunities in lake monitoring and modelling.
Abstract: Climate change is one of the most severe threats to global lake ecosystems. Lake surface conditions, such as ice cover, surface temperature, evaporation and water level, respond dramatically to this threat, as observed in recent decades. In this Review, we discuss physical lake variables and their responses to climate change. Decreases in winter ice cover and increases in lake surface temperature modify lake mixing regimes and accelerate lake evaporation. Where not balanced by increased mean precipitation or inflow, higher evaporation rates will favour a decrease in lake level and surface water extent. Together with increases in extreme-precipitation events, these lake responses will impact lake ecosystems, changing water quantity and quality, food provisioning, recreational opportunities and transportation. Future research opportunities, including enhanced observation of lake variables from space (particularly for small water bodies), improved in situ lake monitoring and the development of advanced modelling techniques to predict lake processes, will improve our global understanding of lake responses to a changing climate. Climate change affects lakes worldwide and is predicted to continue to alter lake ice cover, surface temperature, evaporation rates, water levels and mixing regimes. This Review discusses recent and expected lake responses to climate change and looks towards future research opportunities in lake monitoring and modelling.

412 citations

Journal ArticleDOI
TL;DR: It is found that liver and blood are more useful than muscle as shorter-term dietary indicators for summer flounder and other migratory fishes.
Abstract: Migratory and mobile fishes such as summer flounder (Paralichthys dentatus) often utilize dietary resources with stable isotope signatures that vary over time and space, potentially confounding die...

261 citations

Journal ArticleDOI
TL;DR: It is suggested that mandarin fish stocking can increase predation pressure on forage fish and subsequently optimize the food web structure and has the potential to improve water quality and may be a feasible strategy to alleviate eutrophication of shallow Yangtze lakes.
Abstract: Mandarin fish Siniperca chuatsi, a valuable piscivorous fish, have been stocked into many lakes in China since the 1990s. This study did the first attempt to evaluate the ecological effects of hatchery-reared mandarin fish stocking in the Yangtze River basin lakes. Our study demonstrated a significant change in fish community composition after mandarin fish stocking, but no fish extinction was observed. No significant difference was observed in the total density of 13 forage fish before and after mandarin fish stocking, but the total biomass showed a significant decline after mandarin fish stocking. Significant differences in length-frequency distributions were observed for Carassius auratus, Pseudorasbora parva and Toxabramis swinhonis captured before and after stocking mandarin fish. No significant change in habitat distribution was detected before and after mandarin fish stocking. A marked decline in total nitrogen and a slight decline in total phosphorus were observed while a slight increasing trend for Secchi depth was found after stocking. Our findings suggested that mandarin fish stocking can increase predation pressure on forage fish and subsequently optimize the food web structure. Also, mandarin fish stocking has the potential to improve water quality and may be a feasible strategy to alleviate eutrophication of shallow Yangtze lakes.

219 citations