Browsing by Author "Vizzini, Salvatrice"
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- Altered epiphyte community and sea urchin diet in Posidonia oceanica meadows in the vicinity of volcanic CO2 ventsPublication . Nogueira, Patrícia; Gambi, Maria Cristina; Vizzini, Salvatrice; Califano, Gianmaria; Tavares, Ana Mafalda; Santos, Rui; Martinez-Cruz, BegonaOcean acidification (OA) predicted for 2100 is expected to shift seagrass epiphyte communities towards the dominance of more tolerant non-calcifying taxa. However, little is known about the indirect effects of such changes on food provision to key seagrass consumers. We found that epiphyte communities of the seagrass Posidonia oceanica in two naturally acidified sites (i.e. north and south sides of a volcanic CO2 vent) and in a control site away from the vent at the Ischia Island (NW Mediterranean Sea) significantly differed in composition and abundance. Such differences involved a higher abundance of non-calcareous crustose brown algae and a decline of calcifying polychaetes in both acidified sites. A lower epiphytic abundance of crustose coralline algae occurred only in the south side of the vents, thus suggesting that OA may alter epiphyte assemblages in different ways due to interaction with local factors such as differential fish herbivory or hydrodynamics. The OA effects on food items (seagrass, epiphytes, and algae) indirectly propagated into food provision to the sea urchin Paracentrotus lividus, as reflected by a reduced P. oceanica exploitation (i.e. less seagrass and calcareous epiphytes in the diet) in favour of non-calcareous green algae in both vent sites. In contrast, we detected no difference close and outside the vents neither in the composition of sea urchin diet nor in the total abundance of calcareous versus non-calcareous taxa. More research, under realistic scenarios of predicted pH reduction (i.e. <= 0.32 units of pH by 2100), is still necessary to better understand cascading effects of this altered urchin exploitation of food resources under acidified conditions on ecosystem diversity and function. (C) 2017 Elsevier Ltd. All rights reserved.
- Resistance of seagrass habitats to ocean acidification via altered interactions in a tri-trophic chainPublication . Martínez-Crego, Begoña; Vizzini, Salvatrice; Califano, Gianmaria; Massa-Gallucci, Alexia; Andolina, Cristina; Gambi, Maria Cristina; Santos, RuiDespite the wide knowledge about prevalent effects of ocean acidification on single species, the consequences on species interactions that may promote or prevent habitat shifts are still poorly understood. Using natural CO2 vents, we investigated changes in a key tri-trophic chain embedded within all its natural complexity in seagrass systems. We found that seagrass habitats remain stable at vents despite the changes in their tri-trophic components. Under high pCO2, the feeding of a key herbivore (sea urchin) on a less palatable seagrass and its associated epiphytes decreased, whereas the feeding on higher-palatable green algae increased. We also observed a doubled density of a predatory wrasse under acidified conditions. Bottom-up CO2 effects interact with top-down control by predators to maintain the abundance of sea urchin populations under ambient and acidified conditions. The weakened urchin herbivory on a seagrass that was subjected to an intense fish herbivory at vents compensates the overall herbivory pressure on the habitat-forming seagrass. Overall plasticity of the studied system components may contribute to prevent habitat loss and to stabilize the system under acidified conditions. Thus, preserving the network of species interactions in seagrass ecosystems may help to minimize the impacts of ocean acidification in near-future oceans.
- Seagrass photo-physiological responses in natural high-CO2 environmentPublication . Costa, Monya; Olivé, Irene; Barrote, Isabel; Procaccini, G.; Mazzuca, S.; Vizzini, Salvatrice; Santos, RuiThe atmospheric concentration of CO2 has been steeply increasing over the last 200 years, with an associated increase of total dissolved inorganic carbon (Ci) and a decrease of the oceans’ pH. Seagrasses are among the most productive marine ecosystems, but yet little is known on the effects of high-CO2/low pH on their photosynthetic physiology and the ecological consequences. Marine CO2 seepage areas have been used as natural laboratories to investigate the performance of marine organisms under long-term exposure to high-CO2 levels that mimic the future ocean. In this work we conducted a series of experiments comparing the photophysiology of the seagrasses Posidonia oceanica and Cymodocea nodosa, growing in the vicinity of submarine CO2 vents around the islands of Vulcano and Panarea (Aeolian Archipelago, Southern Tyrrhenian Sea, Italy). Plants growing close to CO2-seepage sites were compared with plants from control sites. Automated chlorophyll fluorometers were deployed for 24-hour periods to examine the changes in photosynthetic efficiency and energy quenching mechanisms. Samples were collected at predawn and noon and analyzed for pigment composition, antioxidant capacity, and soluble carbohydrates. Differences in gene and protein expression were evaluated as a function of Ci levels. Stable carbon isotopes (δ13C) were also analysed to investigate the contribution of volcanic CO2 to seagrass productivity. Both P. oceanica and C. nodosa plants growing in CO2-seepage sites showed lower allocation of PSII-absorbed energy to photochemistry (φII), while presenting higher proportions of energy dissipation by non-photochemical pathways (down-regulation, φNPQ and other energy losses, φNO). As well, diel photosynthesis-irradiance curves (ETRI), built with data acquired over the 24-hour deployments, showed lower photosynthetic rates in plants from CO2 seepage sites. This unexpected pattern of photosynthetic activity will be discussed in light of the complementary data.