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- Laminaria ochroleuca Bachelot de la Pylaie canopy effect on intertidal understorey benthic assemblages in northern PortugalPublication . Barradas, Ana; Alberto, F.; Serrão, Maria Ester Tavares ÁlvaresThe canopy effect of the kelp Laminaria ochroleuca on the associated species assemblages was studied at a northern Portugal intertidal kelp bed, by doing a removal experiment of kelp individuals inside plots of 0.25 m2. The understorey assemblages in undisturbed plots with the same area were sampled for comparison as well as the assemblages inside the holdfasts from the removed kelps. A total of 238 taxa was identified, from which 77 belonged to macroalgae and 161 to invertebrate fauna. The holdfasts showed an average number of 35 epibiont species per holdfast, and several exclusive species when compared to the bottom samples. The understorey assemblage was composed essentially by highly branched red algae and Annelids, Nematods and Arthropods. There was a temporal variability in the assemblages from April to August and an interaction effect between factors time and canopy for algal biomass, but there was no significant interaction for these factors for invertebrate fauna. There was a significant effect of the factor canopy on algal total species, as well as for faunal biomass, faunal species richness and fauna total species. The removal of the canopy did not seem to produce an effect on the recruitment density of its gametophytes. The results seem to respond to changes in light availability and space, with an increase in coarsely and finely branched macroalgae, that represent an increase in habitable space for invertebrate fauna. There was an increase in the number of invertebrate fauna taxa after canopy removal, with an increase in filter and deposit feeding species. The removal of the dominant species in this ecosystem seems to influence the physical structure of the environment, with consequences on the composition of the associated community.
- Fast sporophyte replacement after removal suggests banks of latent microscopic stages of Laminaria Ochroleuca (phaeophyceae) in tide pools in northern PortugalPublication . Barradas, Ana; Alberto, F.; Engelen, Aschwin; Serrão, EsterThis study investigated the effects of a physical disturbance consisting of the removal of adult kelps (Laminaria ochroleuca Bachelot de la Pylaie)and their corresponding understorey turf assemblage in tide pools in northern Portugal.
- Rearing larvae of dusky grouper, Epinephelus marginatus (Lowe, 1834), (Pisces: Serranidae) in a semi-extensive mesocosm | La cría de larvas de mero, Epinephelus marginatus (Lowe, 1834), (Pisces: Serranidae), en un mesocosmos de tecnología semiextensivaPublication . Cunha, M. E.; Quental, H.; Barradas, Ana; Pousão-Ferreira, P.; Cabrita, Elsa; Engrola, S.One of the major obstacles to propagating dusky grouper, Epinephelus marginatus, is the difficulty of rearing the early larvae. We have successfully raised dusky grouper larvae in mesocosms using a mixed diet of endogenous plankton grown in the rearing tank and an exogenous supply of Brachionus plicatilis and Artemia sp. Newly hatched larvae at an initial density of 1.3 ind.l-1 were stocked in partially shaded 3 m3 circular outdoor tanks during the summers of 2007 and 2008. Before introducing newly hatched larvae, the water was left for six days to promote plankton growth. Larval growth occurred at two different rates: i) a faster rate from first feeding to the beginning of metamorphosis, and ii) a slower rate at transformation. Survival at the beginning of metamorphosis was less than 10% (33 DPH) in 2007 and between 25 and 50% (25 DPH) in 2008. High mortalities were observed during larval transformation. The estimated minimum food requirement per grouper larvae increased more than 300% from the beginning of the notochord flexion to the beginning of metamorphosis. To meet such a high feeding requirement the number of larger prey organisms/copepods in the mesocosm should be eight times higher during this time period.