Developing novel molecular tools for characterising food web responses to climate change

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The aim of this project is to quantify the effects of global warming on food web structure of freshwater ecosystems. I will be studying the strength of the links, and the direction of energy flows of several different food webs across a temperature gradient. To address these key ecological questions I will test novel molecular techniques such as next generation sequencing (NGS) which will be used to match more traditional food web approaches. In particular, it is possible to identify species by sequencing part of their genetic code, and comparing it to a database without referring to their morphological traits. The use of such techniques gives us extremely valuable information, in fact: we can detect the presence of cryptic species (I) which are morphologically identical, but have distinct genetic traits, also, identify early instar larvae (II) which are impossible to distinguish at such stage, but it can be useful also in terms of damaged specimens (III). Moreover, I will take advantage of new mesocosm facilities at Silwood park in order to predict the effects of warming on the stability and structure of freshwater ecosystems, in particular we are aiming to heat mesocosms by 4C and 7C which is the degree of heat that we expect to encounter at our latitudes, and high latitudes, respectively, in the following century. The principle is the same adopted in a long-term mesocosm study in Dorset (UK) where we already have an exceptionally detailed data of the community composition and size-spectra of both the pelagic and benthic food webs, but with a higher replicability (96 mesocosms in Silwood park) of treatments. This project will also have a consistent fieldwork component which will take place in five different geothermal sites along the ring of fire in the Northern hemisphere; these will include: Iceland, Greenland, Alaska, Kamchatka, and Svalbard. These arctic sentinel systems will act as a refuge for species migrating polewards due to increase global warming. Moreover, it will be particularly interesting to study these systems as high latitudes surface temperatures are predicted to increase up to 7.5C in the following century (IPCC, 2014). Understanding structure and dynamics of these food webs will be fundamental to address future issues which will appear at our latitudes. The beauty of such geothermal systems is that they almost act as outdoor laboratories, in fact, streams have similar chemical composition, and only differ by water temperature. The Icelandic site (Hengill) has been studied for several years, and we now have a detailed description of its food web. This will allow us to apply NGS techniques into a well described food web, where we expect to match data collected from traditional food web analysis, particularly in terms of species richness and abundances. In addition to this, I will try to describe some of the links yet poorly understood in food web analysis, such as the diet of some groups (e.g. suctorial predators) which represent a missing link within the food web. In order to explore these "missing links", I will apply NGS techniques to analyse the diet of predators not visible from gut content analysis, this will allow us to add valuable information in terms of food web structure. The Icelandic site will act as a platform where we will be testing methods, and experiments which will be then applied to all the other geothermal sites. Keeping these methods consistent will be crucial, in order to investigate and disentangle differences and potential generalities which will emerge across the different sites. In particular, we expect warming to produce similar patterns in ecosystems with a wide difference of species. Finally, I will investigate generalities between natural systems and mesocosms, as previous studies already support a consistent thermal response in relation to ecosystem respiration between the Icelandic streams and the UK mesocosms.