ORCID Profile
0000-0002-2338-0013
Current Organisation
University of Aveiro
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Publisher: MDPI AG
Date: 05-01-2018
Publisher: Oxford University Press (OUP)
Date: 19-05-2010
Publisher: Cambridge University Press (CUP)
Date: 22-07-2011
DOI: 10.1017/S0025315411000853
Abstract: Hydrobia ulvae displays an endogenous rhythm of crawling behaviour of circatidal periodicity, with higher levels of activity during high water. In the present study we address the effect of repeated cycles of immersion and emersion at tidal periodicity on the level and synchronism of the behaviour, by contrasting these with the effects of continuous immersion and continuous emersion. Snails were recorded in dark conditions under the different immersion regimes for 3 days. The results show that continuously emersed snails displayed very low levels of activity. Average activity levels of continuously immersed snails and of those subjected to tidal cycles of immersion and emersion were similar, had identical periods related to the period of the tidal cycle, and had similar phase relationships to the expected tidal cycle. However, form-estimates for these two categories of snails differed, the snails subjected to cyclic conditions showing a larger litude and greater synchronism of activity. Therefore, it is concluded that recurrent cycles of immersion and emersion should contribute to well defined cycles of activity in the intertidal environment, with greater activity levels during high water.
Publisher: Frontiers Media SA
Date: 25-01-2021
DOI: 10.3389/FMARS.2020.606088
Abstract: The marine neuston, organisms living in the vicinity of the ocean surface, is one of the least studied zooplankton groups. Neuston occupies a restricted ecological niche and is affected by a wide range of endogenous and exogenous processes while also being a food source to zooplankton fish migrating from the deep layers and seabirds. In this study, the neustonic communities were characterized along the Malaspina global expedition s ling tropical and subtropical oceanic provinces using stable carbon and nitrogen isotopes to explore their trophic structure and relationships with environmental variables. The differences in stable isotopes mirrored the patterns in environmental characteristics of each province. High δ 13 C values were associated with atmospheric carbon inputs, while the presence of dinoflagellates, coccolithophorids, and upwelling influence is related to low δ 13 C values. Similarly, provinces presenting high δ 15 N values were associated with denitrification and nitrate diffusive fluxes, whereas the presence of low δ 15 N is attributable to nitrogen supplied through N 2 fixation by diazotrophs. Neuston showed a large overlap among the isotopic niches of four functional groups, with chaetognaths and detritivores generally exhibiting a smaller degree of overlap compared to carnivores and omnivores/herbivores. These results support the hypothesis of a common trophic structure in the neuston community across the ocean. However, the size of the niche, small in coastal areas and those influenced by upwelling and large in oligotrophic regions, and their overlap, low in more productive provinces and high in oligotrophic provinces, may be associated with food availability. Small trophic niches are associated with a dominance of specialized over-opportunistic feeding in productive environments.
Publisher: Inter-Research Science Center
Date: 14-03-2011
DOI: 10.3354/MEPS08992
No related grants have been discovered for Henrique Queiroga.