Edinburgh Napier University

  Parasites have been excluded from most food web constructions, partly because of their assumed negligible contribution to the flow and stock of energy in ecosystems. These assumptions have been disputed. Parasites also present practical and conceptual problems in knowing how best to represent them in trophic networks that use simple graphical descriptions of species as producers, consumers, and prey without ontological changes. Parasites have been erroneously labelled as top predators and have resulted in ecologically unrealistic inflations of trophic levels. A range of methods were assessed here in order to explore how parasites might suitably be included in a food web describing the Tellina fabula-community characteristic of Fine Sands (FSd) in the German Bight, North Sea. Parasites were identified through dissection of prominent teleost hosts from the web and an extensive literature search and included as discrete species-specific nodes and as disaggregated, ontogenetic nodes. Parasites in the FSd were relatively less complex than those in other food webs. This is likely a result of the networks small size, relating to network scale variance, and highly connected free-living species. A novel method for calculating flow-based trophic levels in the absence of information on interaction strengths was successful in mitigating unrealistic trophic level inflations and a speculative food web, including parasites in combined nodes with their hosts suggests a useful future method for accurately representing parasites place in and their effects on food webs, without being labelled as top predators or inflating trophic levels. Food webs remain important heuristic tools for teaching and understanding ecology but represent gross simplifications of the dynamic energy flows in ecosystems. Excluding parasites from them exacerbates this distortion. This work shows a range of methods by which parasites can be included and demonstrates the advantages of doing so. It also highlights significant gaps in knowledge that remain.