0000000001310475
AUTHOR
Chris Harrod
From clear lakes to murky waters – tracing the functional response of high-latitude lake communities to concurrent ‘greening’ and ‘browning’
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 degrees C, precipitation +30% and nutrient +45 mu g L-1 total phosphorus). Along this gradient, we observed an increase in the assimilation of pelagic-derived carbon from…
Adaptive radiation along a thermal gradient: preliminary results of habitat use and respiration rate divergence among whitefish morphs.
Adaptive radiation is considered an important mechanism for the development of new species, but very little is known about the role of thermal adaptation during this process. Such adaptation should be especially important in poikilothermic animals that are often subjected to pronounced seasonal temperature variation that directly affects metabolic function. We conducted a preliminary study of individual lifetime thermal habitat use and respiration rates of four whitefish (Coregonus lavaretus (L.)) morphs (two pelagic, one littoral and one profundal) using stable carbon and oxygen isotope values of otolith carbonate. These morphs, two of which utilized pelagic habitats, one littoral and one …
Lake size and fish diversity determine resource use and trophic position of a top predator in high-latitude lakes
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…
Reply to LoganDodge: 'stable isotopes challenge the perception of ocean sunfish Mola mola as obligate jellyfish predators'.
Syvaranta et al. (2012) recently provided stable-isotope data from eight small-bodied ocean sunfish Mola mola (L. 1758) captured from the Italian fishing port of Camogli on the Ligurian coast. Representative data were also given for members of pelagic and neritic–coastal food webs. The level of 13C and 15N enrichment shown by M. mola relative to their putative obligate diet of gelatinous zooplankton (gelata) (based on the locally dominant Pelagia noctiluca and literature data) was used to question their obligate consumption of such prey. Furthermore, the M. mola were isotopically more similar to neritic rather than pelagic fishes captured locally, prompting the suggestion that juvenile M. m…
A revised model for lipid-normalizing δ13C values from aquatic organisms, with implications for isotope mixing models
1. Stable isotope analyses coupled with mixing models are being used increasingly to evaluate ecological management issues and questions. Such applications of stable isotope analyses often require simultaneous carbon and nitrogen analyses from the same sample. Correction of the carbon isotope values to take account of the varying content of 13 C-depleted lipids is then frequently achieved by a lipid-normalization procedure using a model describing the relationship between change in δ 13 C following lipid removal and the original C:N ratio of a sample. 2. We evaluated the applicability of two widely used normalization models using empirical data for muscle tissue from a wide range of fish an…
Stable isotopes challenge the perception of ocean sunfish Mola mola as obligate jellyfish predators
Evidence is provided from stable isotope analysis that aggregations of small ocean sunfish Mola mola (total length <1 m) feed broadly within coastal food webs and their classification as obligate predators of gelatinous zooplankton requires revision.
Seasonal changes in European whitefish muscle and invertebrate prey fatty acid composition in a subarctic lake
Ambient light and temperature show extreme seasonal variation in subarctic lakes due to the midnight sun period in summer and cold polar night period in winter. These changes have clear impacts on fish feeding and reproduction cycles, potentially affecting the fatty acid (FA) composition of muscle. Despite extensive research into fish FA over recent decades, we know little about intra‐annual changes of fish FA profile and content. We studied intra‐annual changes in the FA profile (mol%) and content (mg g‐1 dry weight) of sexually mature European whitefish (Coregonus lavaretus) muscle in a large and deep subarctic lake located in northern Fennoscandia. We collected fish, zooplankton, and ben…
Data from: Lake size and fish diversity determine resource use and trophic position of a top predator in high-latitude lakes
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…