Browsing by Author "Pardal, M. A."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Beach morphodynamic impact on a macrobenthic community along a subtidal depth gradientPublication . Dolbeth, M.; Ferreira, Oscar; Teixeira, H.; Marques, J. C.; Dias, J.A.; Pardal, M. A.The subtidal macrobenthic community of a temperate beach in southern Portugal was studied along a depth gradient (1.3 to 32 m deep), which was long enough to comprise both highly hydrodynamic and calmer areas, to assess the influence of the spatial and temporal differences in hydrodynamic impact at the seafloor on the organization of a macrobenthic community. These differences were assessed by studying the variations in wave climate, depth of closure and extension of the mixed profile. A spatial zonation was detected from highly hydrodynamic shallow depths, 7.2 m deep shorewards, to the calmer deeper areas, from 8.4 m seawards. Accordingly, in the shallowest depths, species richness and densities were lower, with the inhabiting species, mainly crustaceans and surf clams, adapted to the environmental severity. Both species richness and densities increased along the depth gradient, and the community became dominated by polychaetes, nematodes and nemerteans. Seawards, within the relict sediments (deeper than 25 m), species richness and abundance decreased again. The community patterns also changed in response to the occurrence of strongly hydrodynamic episodes (such as storms), which had a higher impact than the seasonality. It was concluded that harsh physical environmental conditions reduce species richness, both spatially and temporally. With respect to density, other parameters related to life cycle characteristics, recruitment success and biotic interactions may also have some impact.
- Influence of oceanic and climate conditions on the early life history of European seabass Dicentrarchus labraxPublication . Pinto, Miguel; N. Monteiro, J.; Crespo, D.; Costa, F.; Rosa, J.; Primo, A. L.; Pardal, M. A.; Martinho, F.Understanding how marine fish early-life history is affected in the long-term by environmental and oceanographic factors is fundamental given its importance to population dynamics and connectivity. This work aimed at determining the influence of these processes on the interannual variability in hatch day and early-life growth patterns of European seabass, over a seven-year period (2011-2017) in the Atlantic Iberian coast. To accomplish this, otolith microstructure analysis was used to determine seabass hatch day and to develop early-growth correlations. In most years, hatching occurred from February to April, with two exceptions: in 2012, hatching started in early-January, and in 2016 an exceptionally long hatching period was registered. Using generalized additive models (GAM), we observed that sea surface temperature (SST), the North Atlantic Oscillation index (NAOi) and Chlorophyll-a (Chla) were the main drivers behind the inter-annual variability in seabass hatch day. Analysis of correlations between growth increments allowed assessing important periods of seabass growth and how future growth is affected. Since seawater temperature is among the main drivers for seabass recruitment and growth, its life cycle may be hampered due to ocean warming and an increasingly unstable climate, with consequences for the natural marine stocks and their harvest.