Browsing by Author "Pedersen, Morten F."
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- Kelp carbon sink potential decreases with warming due to accelerating decompositionPublication . Filbee-Dexter, Karen; Feehan, Colette J.; Smale, Dan A.; Krumhansi, Kira A.; Augustine, Skye; De Bettignies, Florian; Burrows, Michael T.; Byrnes, Jarrett E.K.; Campbell, Jillian; Davoult, Dominique; Dunton, Kenneth H.; Franco, Joao N.; Garrido, Ignacio; Grace, Sean P.; Hancke, Kasper; Johnson, Ladd E.; Konar, Brenda; Moore, Pippa J.; Norderhaug, Kjell Magnus; O'Dell, Alasdair; Pedersen, Morten F.; Salomon, Anne K.; Sousa-Pinto, Isabel; Tiegs, Scott; Yiu, Dara; Wernberg, ThomasCycling of organic carbon in the ocean has the potential to mitigate or exacerbate global climate change, but major questions remain about the environmental controls on organic carbon flux in the coastal zone. Here, we used a field experiment distributed across 28° of latitude, and the entire range of 2 dominant kelp species in the northern hemisphere, to measure decomposition rates of kelp detritus on the seafloor in relation to local environmental factors. Detritus decomposition in both species were strongly related to ocean temperature and initial carbon content, with higher rates of biomass loss at lower latitudes with warmer temperatures. Our experiment showed slow overall decomposition and turnover of kelp detritus and modeling of coastal residence times at our study sites revealed that a significant portion of this production can remain intact long enough to reach deep marine sinks. The results suggest that decomposition of these kelp species could accelerate with ocean warming and that low-latitude kelp forests could experience the greatest increase in remineralization with a 9% to 42% reduced potential for transport to long-term ocean sinks under short-term (RCP4.5) and long-term (RCP8.5) warming scenarios. However, slow decomposition at high latitudes, where kelp abundance is predicted to expand, indicates potential for increasing kelp-carbon sinks in cooler (northern) regions. Our findings reveal an important latitudinal gradient in coastal ecosystem function that provides an improved capacity to predict the implications of ocean warming on carbon cycling. Broad-scale patterns in organic carbon decomposition revealed here can be used to identify hotspots of carbon sequestration potential and resolve relationships between carbon cycling processes and ocean climate at a global scale.
- Local flexibility in feeding behaviour and contrasting microhabitat use of an omnivore across latitudesPublication . Leclerc, Jean-Charles; Bettignies, Thibaut de; Bettignies, Florian de; Christie, Hartvig; Franco, João N.; Leroux, Cédric; Davoult, Dominique; Pedersen, Morten F.; Filbee‑Dexter, Karen; Wernberg, ThomasAs the environment is getting warmer and species are redistributed, consumers can be forced to adjust their interactions with available prey, and this could have cascading effects within food webs. To better understand the capacity for foraging flexibility, our study aimed to determine the diet variability of an ectotherm omnivore inhabiting kelp forests, the sea urchin Echinus esculentus, along its entire latitudinal distribution in the northeast Atlantic. Using a combination of gut content and stable isotope analyses, we determined the diet and trophic position of sea urchins at sites in Portugal (42° N), France (49° N), southern Norway (63° N), and northern Norway (70° N), and related these results to the local abundance and distribution of putative food items. With mean estimated trophic levels ranging from 2.4 to 4.6, omnivory and diet varied substantially within and between sites but not across latitudes. Diet composition generally reflected prey availability within epiphyte or understorey assemblages, with local affinities demonstrating that the sea urchin adjusts its foraging to match the small-scale distribution of food items. A net “preference” for epiphytic food sources was found in northern Norway, where understorey food was limited compared to other regions. We conclude that diet change may occur in response to food source redistribution at multiple spatial scales (microhabitats, sites, regions). Across these scales, the way that key consumers alter their foraging in response to food availability can have important implication for food web dynamics and ecosystem functions along current and future environmental gradients.