FOOD WEB STRUCTURE BUT NOT ROBUSTNESS DIFFER BETWEEN RIVERS, LAKES AND ESTUARIES

The pervading physical habitat differences between lakes, rivers, and estuaries should result in structural and thus stability differences in food webs in these three different aquatic habitats. We compared 24 metrics of food web structure and the robustness to loss of both well-connected and random species of 18 well-resolved food webs from six lakes, six rivers, and six estuaries. Robustness measures the proportion of species that need to be removed for 50% of all species to be lost/disconnected. Riverine food webs had lower neighborhood clustering and greater variability in prey vulnerability than estuaries and lakes. Typically, rivers experience physical disturbance relatively more frequently and with greater severity than estuaries and lakes. Disturbance may drive rivers to have lower clustering and have greater proportions of early successional taxa that are mobile and have little armor, and hence greater variability in their vulnerability to predation. Despite the observed differences in food web structure, these did not drive differences in modelled food web robustness between the three habitats. Similarities in robustness may be a result of freshwater organisms having similar body-size ratios between predator and prey/resource taxa thereby driving similar link distributions