| 1. |
- Bertrand, Philip, et al.
(författare)
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Feeding at the front line : interannual variation in the use of glacier fronts by foraging black-legged kittiwakes
- 2021
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 677, s. 197-208
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Tidskriftsartikel (refereegranskat)abstract
- Tidewater glacier fronts can represent important foraging areas for Arctic predators. Their ecological importance is likely to change in a warmer Arctic. Their profitability and use by consumers are expected to vary in time, but the underlying mechanisms driving such variation remain poorly known. The subglacial plume, originating from meltwater discharge, is responsible for the entrainment and transport of zooplankton to the surface, making them more readily available for surface-feeding seabirds. Both discharge and zooplankton abundance are known to fluctuate in time and are thus expected to modulate the foraging profitability of glacier fronts. This study tested the predictions that annual use of glacier fronts by black-legged kittiwakes Rissa tridactyla is positively related to the average glacier discharge and prey biomass in the fjord. To do this, we combined a multiyear dataset of environmental drivers and GPS tracks of birds in Kongsfjorden, Svalbard. Our results confirmed the interannual variation in the use of glacier fronts by kittiwakes; however, contrary to our predictions, these variations were negatively correlated to both glacier discharge and zooplankton abundance. These apparent negative relationships likely reflect non-linear effects and complex interactions between local and regional environmental factors that affect the relative profitability of glacier fronts as foraging areas. Despite their high spatial predictability, glacier fronts may not offer consistent foraging opportunities for marine predators over time.
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| 2. |
- Vihtakari, Mikko, et al.
(författare)
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Combined effects of ocean acidification and warming on prefertilization and early life stages of the Mediterranean mussel Mytilus galloprovincialis.
- 2013
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 5:4, s. 1890-1915
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Tidskriftsartikel (refereegranskat)abstract
- Larval stages are among those most vulnerable to ocean acidification (OA). Projected atmospheric CO2 levels for the end of this century may lead to negative impacts on communities dominated by calcifying taxa with planktonic life stages. We exposed Mediterranean mussel (Mytilus galloprovincialis) sperm and early life stages to pHT levels of 8.0 (current pH) and 7.6 (2100 level) by manipulating pCO2 level (380 and 1000 ppm). Sperm activity was examined at ambient temperatures (16–17 °C) using individual males as replicates. We also assessed the effects of temperature (ambient and ≈20 °C) and pH on larval size, survival, respiration and calcification of late trochophore/early D-veliger stages using a cross-factorial design. Increased pCO2 had a negative effect on the percentage of motile sperm (mean response ratio R= 71%) and sperm swimming speed (R= 74%), possibly indicating reduced fertilization capacity of sperm in low concentrations. Increased temperature had a more prominent effect on larval stages than pCO2, reducing performance (RSize = 90% and RSurvival = 70%) and increasing energy demand (RRespiration = 429%). We observed no significant interactions between pCO2 and temperature. Our results suggest that increasing temperature might have a larger impact on very early larval stages of M. galloprovincialis than OA at levels predicted for the end of the century.
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| 3. |
- Vihtakari, Mikko, et al.
(författare)
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Variable Individual- and Population- Level Responses to Ocean Acidification
- 2016
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Ingår i: "Frontiers in Marine Science". - : Frontiers Media SA. - 2296-7745. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Population responses to marine climate change are determined by the strength of the selection pressure imposed by changing climate, the genetic variability within the population (i.e., among individuals), and phenotypic plasticity within individuals. Marine climate change research has focused primarily on population-level responses, yet it is at the level of the individual that natural selection operates. We studied individual-level responses of two bivalve species to ocean acidification (OA) at the earliest stage of the life-cycle. We measured sperm activity (swimming speed and percent motility) in the Boreal/Arctic Macoma calcarea and the temperate Mytilus galloprovincialis in response to two pCO2 levels (380 and 1000 ppm) at the ambient temperature at the collection site, i.e., 2 and 16°C, respectively. We also assessed sperm longevity under control conditions. Treatment effects on fertilization success were estimated using fertilization models. At the population level, simulated OA reduced M. galloprovincialis sperm swimming speed by 30%, percent motility by 44%, and fertilization success by 43%, whereas only sperm swimming speed was significantly affected in M. calcarea. Both species showed substantial variability among individuals in response to increased pCO2. This variability was greatest in M. galloprovincialis ranging from non-significant effect to more than 73% reduction in fertilization success in response to OA, whereas M. calcarea responses varied from 8% increase in percent sperm motility to 26% reduction in swimming speed. Further, modeled fertilization success was negatively affected by simulated OA in 10 of 13 studied M. galloprovincialis males and in three of 10 M. calcarea males. We observed sperm longevities (82 h for M. calcarea and 25 h for M. galloprovincialis on average) far longer than the expected time-frame for efficient fertilization accounting for dilution of gametes. Assuming sperm activity is a heritable trait, natural selection might be a possible way for the studied populations to adapt to near-future OA.
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