Browsing by Author "Silva, A. C. F."
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- Impact of freshwater inputs on the spatial structure of benthic macroinvertebrate communities in two landlocked coastal lagoonsPublication . Félix, Pedro; Correia, Maria; Chainho, Paula; Costa, José Lino; Chaves, Maria Luisa; Cruz, Teresa; Castro, João J.; Mirra, C.; Domingos, Isabel; Silva, A. C. F.; Cancela Da Fonseca, LuísLandlocked lagoons are naturally stressed environments. They are strongly influenced by freshwater input which not only varies naturally, but which is also impacted by anthropogenic activities. This study investigated the direct influence of freshwater discharges on the distribution patterns and abundance of benthic communities in two neighbouring landlocked coastal lagoons, assessing the whole system and the confluence area of each tributary. Sampling occurred in the wet and dry seasons of 2011 at two distances from freshwater discharge locations. Both lagoons were colonized by species from two different pools, freshwater and marine. Freshwater flow rates had a direct influence on the spatial structure of the benthic communities of brackish-water/freshwater interface areas, where also specific taxa can act as early indicators of freshwater input variations. The intensity of this influence is highly dependent on lagoon size, creating spatial heterogeneity or affecting the entire system. The benthic fauna at the confluence of the tributary that depends almost exclusively on groundwater showed the lowest variability, suggesting that the biogeochemical nature of the groundwater may be a central cause for setting specific ecotones. The results suggest that benthic communities of landlocked coastal lagoons can be highly impacted by flow reduction from freshwater aquifers under drought conditions or water abstraction activities.
- Site fidelity of intertidal fish to rockpoolsPublication . Roma, J.; Dias, Marta; Vinagre, Catarina; Silva, A. C. F.Gobius paganellus, Lipophrys pholis and Coryphoblennius galerita are wide‐spread intertidal fish that spend their earlier life stages in rock pools, and yet very little is known about their site fidelity behaviour. For these species, fidelity to rockpools may result in increased fitness costs in a predicted scenario of warmer sea water, due to the low thermal inertia of these water bodies. In this context, it is relevant to investigate these species' site fidelity. We made a mark‐recapture study to assess the mentioned species' movements within and between rockpools. We tagged a total of 530 individuals of the aforementioned species with the Visible Implant Elastomer and tracked their movement for a 7‐month period. We found that site fidelity and specific rockpools conditions are important factors in distribution of intertidal blennies and gobies. We also examined the relations between rockpool volume, depth and site fidelity. We found that G. paganellus tends to remain in its original marking pool, with an average recapture rate of 20.5%, but showed no evidence of inter‐pool movement. Rockpool depth, however, proved to be important in the blennies' movements. Our findings are among the first to prove that a mark‐recapture method can be successfully used to track intertidal fish movements. In particular, we showed that G. paganellus presents site fidelity in intertidal rockpools during its early ontogeny for a period of two to three months.