Browsing by Author "Sousa-Pinto, Isabel"
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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.
- Modulation of different kelp life stages by herbivory: compensatory growth versus population decimationPublication . Franco, Joao N; Wernberg, Thomas; Bertocci, Iacopo; Jacinto, David; Maranhão, Paulo; Pereira, Tânia; Martinez, Brezo; Arenas; Francisco; Sousa-Pinto, Isabel; Tuya, FernandoPartitioning the efects of herbivory on diferent life stages of primary producers is key to understanding the population-wide consequences of herbivory. We assessed the performance of microscopic (MiS <1 mm) juveniles, macroscopic (MaS) juveniles and adult kelp (Laminaria ochroleuca) under contrasting herbivory regimes through a herbivore exclusion feld experiment. The abundance of MiS and the survival of MaS decreased by 67 and 63%, respec tively, when herbivorous fshes and sea urchins were present. Blade growth (linear and area) of adult kelp displayed con trasting patterns under herbivore pressure: a 60% increase and a 46% decrease, respectively. These results indicate that while herbivory severely reduces juvenile survival, it may also induce compensatory growth (measured as linear growth) in adult kelp. In summary, we here demonstrate how herbivory afects all sporophyte life stages of the kelp L. ochroleuca. This is likely to have important implications for situations where historical patterns of herbivore presence and herbivory are changing, such as is increasingly the case in many temperate regions due to warming around the world.
- Sea urchin grazing preferences on native and non-native macroalgaePublication . Cardoso, André C.; Arenas, Francisco; Sousa-Pinto, Isabel; Barreiro, Aldo; Franco, Joao NHerbivory plays a major role in shaping community dynamics across freshwater, marine and terrestrial habitats, by controlling patterns of abundance and distribution of primary producers, including seaweeds. In the context of biological invasions, the proliferation of non-native seaweeds has been often attributed to limited grazing by native herbivores on introduced species (“Enemy Release Hypothesis”, ERH). In our study, we aimed to explore the potential of an abundant generalist herbivore (the sea urchin Paracentrotus lividus) to graze on non-native in comparison to native macroalgae species. For this purpose, we used manipulative experiments to assess sea urchin preference on native and non-native seaweed species present in the northwest coast of Portugal. Specifically, we determined the preferences of P. lividus on brown seaweeds i.e. Laminaria ochroleuca, Saccorhiza polyschides and the non-native Undaria pinnatifida, and red seaweeds i.e. Chondrus crispus, Mastocarpus stellatus and the non-native Grateloupia turuturu. For each group of seaweed species, sea urchin preference and biomass consumption were examined. The nutritional (organic carbon and nitrogen) and chemical (phenolic content) features were also analysed, in order to assess their effect on sea urchin feeding. According to the results, P. lividus did not show a specific preference for any of the different seaweeds of each phylum. These results suggest that P. lividus is a generalist herbivore, not exerting a differential grazing pressure on non-native seaweeds when compared to native ones.
- Snapshot of macroalgae and fish assemblages in temperate reefs in the Southern European Atlantic ecoregionPublication . Franco, Joao N.; Arenas, Francisco; Sousa-Pinto, Isabel; Santos, Carmen B. de losMost of the biodiversity studies in the South European Atlantic Shelf ecoregion are limited to shallow subtidal or intertidal habitats, while deeper reef habitats, also of relevant ecological importance, are particularly understudied. Macroalgal communities, associated fauna, and sea surface temperature were studied in deep reefs (25–30 m) at two locations in this ecoregion: Parcel, North of Portugal (41º N), and Tarifa, Southern Spain (35º N). Specifically, algal assemblages were assessed using biomass collection and associated ichthyofauna was assessed using visual census techniques using scuba. Seawater surface temperature was higher (>3º C) in the southern region—Tarifa, compared to the northern region—Parcel. Our survey revealed 18 fish species and 23 algae species. The highest abundance of cold-water species (both macroalgae and fish species) was recorded in Parcel and warm-water species were dominant in Tarifa. In light of climate global trends, both regions might experience biodiversity shifts towards tropicalization. Current knowledge on their biodiversity is imperative to further evaluate potential shifts.