MEPS prepress abstract  -  DOI:

Short food chains, high connectance and high cannibalism in food web networks of small intermittent estuaries

Vanessa Mendonça, Catarina Vinagre*


ABSTRACT: Small intermittent estuaries are a common feature in some parts of the world. They are recognized as important refuge and nursery areas for several marine species. However, their biological dynamics are still poorly known. In fact, the network structure of their food webs remains undescribed. Highly resolved food webs were compiled for 23 small intermittent estuaries in the Northeast Atlantic, Mediterranean, SW Indian Ocean and South Pacific. The structural network properties of these food webs were compared to that of larger open estuaries, lakes, and rivers, as well as marine and terrestrial ecosystems. The most important conclusion is that the network properties of these systems are different from those of larger open estuaries and more like other non-estuarine ecosystems. They also stand out from all other ecosystems, including larger open estuaries, in terms of omnivory, which was found to be remarkably high (83-92%), probably due to prevalence of opportunistic feeding. Nevertheless, all other properties were well within the ranges reported for other ecosystems, thus, the general organization rules of food web networks also apply to small intermittent estuaries. It was concluded that general rules applied to the management of estuaries should be looked at carefully when managing these smaller intermittent systems, since they have shorter chain lengths, higher connectance and higher cannibalism. Shorter chain length implies that disturbance is more likely to rapidly affect many food web components through predator-prey links, which may be counter-balanced by the effect of high connectance. These systems should thus, not be looked at simply as smaller versions of larger open systems.