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- Changing webs—Variation of complex networks over a tidal cycle in an intertidal rocky reefPublication . Vinagre, Catarina; Mendonça, VanessaIncorporating temporal variation in models is one of the most important challenges in food web research. One of the environments where time causes profound changes is the intertidal zone, where the immersion-emersion cycle drastically changes the abiotic and biotic conditions. Intertidal rocky shores have been intensively studied, however the variation in the complex food web network that occurs during a tidal cycle remains undescribed. Highly resolved food web networks were assembled for an intertidal reef depicting the food web during low and high tide, and with and without tide pools. It was concluded that high tide adds new species to the web, but it does not add complexity since network connectance was not changed. This occurs because incoming species are mostly highly generalist fish, which add many new links to the web. Tide pools, however, add not only diversity but also complexity. Webs were dominated by intermediate species, with the proportion of top consumers fluctuating throughout the tidal cycle, being lowest during low tide and highest at high tide, due to the incoming larger vertebrate predators. Consumer taxa outnumbered resource taxa, except at low tide when pools are present. Mean trophic level was lowest at low tide (2.3) and highest at high tide with pools (2.6). Omnivory was high and showed little change. "Chain", the number of links connecting top to basal species, was stable but low. This implies that disturbance can rapidly travel bottom-up or top-down through predator-prey links. The increased connectance given by the addition of tide pools likely increases robustness to disturbances, an important feature in coastal areas so often impacted by human action.
- Network analysis reveals humans as top predators and the key role of cuttlefish in the food web structure of a marine protected area (Arrábida Natural Park)Publication . Vinagre, Catarina; Almeida, Luis Pedro; Ronquillo, Pilar; Alegria Mendonça, Vanessa Sofia; Frade, Duarte Gonçalves; Gonçalves, Emanuel J.; Erzini, Karim; Serrao, Ester A.The marine protected area (MPA) of the Arrábida Natural Park is a mid-latitude hotspot for biodiversity. To understand its trophic structure, a highly defined food web network was assembled for this ecosystem, consisting of 884 taxa. Network analysis showed that humans are the top predators, as well as various seabirds, dolphins and sharks. This web is dominated by intermediate species, and its general organization follows previously reported patterns for other marine and coastal ecosystems. Two swimming crabs, Polybius navigator and Polybius henslowii, assume important roles as mid-trophic level consumers and prey, due to their high connectivity in the network. The cuttlefish, Sepia officinalis, a cephalopod of high commercial value, assumes the most pivotal role in the network, as it is the species with the highest number of prey and is among the top 10 most highly connected species (with more links to other species). Additionally, the cuttlefish is among the species with shortest path length, that is the lowest number of links connecting it to any other species. Since, this cephalopod is highly mobile and extends its territory outside the MPA, into the Sado estuary, where it is the main target of local fisheries, and is exposed to various pollution sources, close monitoring the local population of cuttlefish is of the utmost importance, not only in the Arrabida ´ MPA but also in the adjacent Sado estuary.