Browsing by Author "Tavares, Ana Mafalda"
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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.
- Functional traits of ecosystem engineers as predictors of associated faunaPublication . Jiménez Herrero, Javier; Desiderato, Andrea; Vieira, Pedro Emanuel; Tavares, Ana Mafalda; Queiroga, Henrique; Santos, RuiThe ongoing combination of global warming and increased anthropogenic pressure is causing latitudinal shifts in marine species, potentially impacting community composition, local richness, and marine trophic webs. This study investigates the factors influencing the distribution and diversity of intertidal seaweed and associated peracarid communities, including their functional traits, and explores various facets of beta diversity (taxonomic and functional). We hypothesize that: 1) abiotic factors such as temperature and anthropogenic pressure significantly influence seaweed distribution and diversity shifts, and 2) changes in seaweed functional diversity have an impact on the diversity and functioning of its associated peracarid communities. The sampling was conducted along a wide latitudinal gradient in the NE Atlantic (27(degrees)N - 65(degrees)N), encompassing three distinct ecoregions: Northern European coasts, the Iberian Peninsula, and Macaronesia. The identified seaweed and peracarid species were classified functionally, and taxonomic and functional diversity were analysed on a large geographic scale. The northern region exhibited large brown canopy seaweeds and epibiotic isopods, while Macaronesia featured small red, highly branched, and calcareous crust seaweeds with burrower and tubebuilding tanaids. The Iberian Peninsula acted as a transitional zone, showcasing a mix of green, red, and brown seaweeds, along with Amphipoda peracarids found across all ecoregions. Our findings underscore the impact of geographic distance on total beta diversity, revealing distinct seaweed and peracarid communities across spatial gradients. Environmental variables, particularly pH and maximum sea surface temperature, emerged as significant factors influencing beta diversity patterns of seaweeds, indicating the potential impact of acidification and heat waves on community composition. In addition, seaweed functional traits were shown to be significant in shaping the diversity and abundance of associated peracarid assemblages, impacting both taxonomic and functional beta diversity. These findings provide crucial insights into the factors influencing the biogeography and biodiversity dynamics of intertidal seaweeds and associated peracarids, offering essential implications for conservation and management strategies amid ongoing environmental changes.
- Integrated assessment of bioerosion, biocover and downwearing rates of carbonate rock shore platforms in southern PortugalPublication . Moura, Delminda; Gabriel, Selma; Gamito, Sofia; Santos, Rui; Zugasti, Estibaliz; Gomes, A.I.; Tavares, Ana Mafalda; Martins, Ana LuísaBioerosion on rocky shores has been frequently reported as an important mechanism in coastal evolution, with less attention focussed on determining the bioprotective role organisms may have in mediating coastal erosion. This work aims, for the first time, to provide an integrated assessment of both traversing microerosion meter (TMEM) downwearing rates and activity of intertidal organisms on two carbonate shore platforms in southern Portugal. Paired substations positioned on the same substrate but differing in biological cover (one with bare rock and the other with algal cover colonised between the first and final readings) were monitored for eighteen months using a TMEM. At each station, the volume of burrows produced by macro borers was measured. Downwearing rates were lower in the surfaces protected by algal turf except in the station that experienced the longest time of exposure to subaerial conditions. In contrast, TMEM downwearing rates were higher in the areas containing the higher volume of burrows. Both downwearing rates and burrow volumes were negatively correlated with the mechanical strength of the substrate as measured by Schmidt Hammer rebound.