The scaling of parasite biomass with host biomass in lake ecosystems: are parasites limited by host resources?

Only very few recent studies have quantified the biomass of parasites across an entire ecosystem and compared it to that of free-living species. For example, Kuris et al. (2008) found that in three estuaries on the Pacific coast of North America, trematodes, the most common parasite taxon in these systems, achieved biomasses in the order of 0.8 to 2 g m2; other parasite taxa occurred at much lower biomasses. Remarkably, the biomass of trematodes exceeded that of birds by at least three-fold, and was only slightly lower than that of fish and polychaetes in all three estuaries (Kuris et al. 2008). In three fishless Californian ponds, trematodes had total biomass values around 0.1 g m2, an order of magnitude lower than that of frogs and snails, but equal to or superior to that of any order of insects or crustaceans (Preston et al. 2013). Most of the trematode biomass in these ecosystems is localized within the intermediate hosts, i.e. juvenile stages of the parasites account for more biomass than adult worms inside their definitive vertebrate hosts (see also Sukhdeo 2012). It remains to be seen whether the findings summarized above are generally applicable to other types of ecosystems. Another issue regarding parasite biomass is the extent to which it is resource limited. There is insufficient empirical evidence to determine whether parasites are subject to the Ecography 39: 507–514, 2016 doi: 10.1111/ecog.01720 © 2015 The Authors. Ecography © 2015 Nordic Society Oikos Subject Editor: Miguel Matias. Editor-in-Chief: Miguel Araújo. Accepted 12 June 2015