Bridging Food Webs, Ecosystem Metabolism, and Biogeochemistry Using Ecological Stoichiometry Theory

Abstract

Although aquatic ecologists and biogeochemists are well aware of the crucial importance of ecosystem functions, i.e., how biota drive biogeochemical processes and vice-versa, linking these fields in conceptual models is still uncommon. Attempts to explain the variability in elemental cycling consequently miss an important biological component and thereby impede a comprehensive understanding of the underlying processes governing energy and matter flow and transformation. The fate of multiple chemical elements in ecosystems is strongly linked by biotic demand and uptake; thus, considering elemental stoichiometry is important for both biogeochemical and ecological research. Nonetheless, assessments of ecological stoichiometry (ES) often focus on the elemental content of biota rather than taking a more holistic view by examining both elemental pools and fluxes (e.g., organismal stoichiometry and ecosystem process rates). ES theory holds the promise to be a unifying concept to link across hierarchical scales of patterns and processes in ecology, but this has not been fully achieved. Therefore, we propose connecting the expertise of aquatic ecologists and biogeochemists with ES theory as a common currency to connect food webs, ecosystem metabolism, and biogeochemistry, as they are inherently concatenated by the transfer of carbon, nitrogen, and phosphorous through biotic and abiotic nutrient transformation and fluxes. Several new studies exist that demonstrate the connections between food web ecology, biogeochemistry, and ecosystem metabolism. In addition to a general introduction into the topic, this paper presents examples of how these fields can be combined with a focus on ES. In this review, a series of concepts have guided the discussion: (1) changing biogeochemistry affects trophic interactions and ecosystem processes by altering the elemental ratios of key species and assemblages; (2) changing trophic dynamics influences the transformation and fluxes of matter across environmental boundaries; (3) changing ecosystem metabolism will alter the chemical diversity of the non-living environment. Finally, we propose that using ES to link nutrient cycling, trophic dynamics, and ecosystem metabolism would allow for a more holistic understanding of ecosystem functions in a changing environment.

Nutrient Dynamics in Decomposing Dead Wood in the Context of Wood Eater Requirements: The Ecological Stoichiometry of Saproxylophagous Insects

“…Our understanding of elemental limitations in heterotrophs in the sense of Liebig's law, by which only the most limiting nutrient shapes ecological interactions, is too simplistic. Rather, multielemental (or multi-resource if macronutrients are considered) co-limitation likely occurs and shapes these interactions (Marleau et al 2015;Kaspari and Powers 2016;Sperfeld et al 2016b;Wirtz and Kerimoglu 2016;Jeyasingh et al 2017;Kaspari et al 2017a, b;Welti et al 2017) (see also Meunier et al 2017 for context and discussion of the links between nutrient stoichiometry and organismal traits). However, only C:N:P ratios have been extensively studied to date within the framework of ecological stoichiometry and mainly in aquatic ecosystems (see Filipiak and Weiner 2017b for review).…”

“…Furthermore, a recent analysis of the literature related to ecological stoichiometry shows that data about elements other than C, N, and P are scarce, especially for terrestrial ecosystems (see Filipiak and Weiner 2017b for review). Currently, many researchers continue to focus on C:N:P stoichiometry (e.g., Sitters et al 2017;Meunier et al 2017;Welti et al 2017;Zhang and Elser 2017;Cherif et al 2017, but see Jeyasingh et al 2017, which discusses shifts from single-nutrient models to more complex, multiplenutrient models that predict co-limitation), so future studies should fill this gap. Considering a larger number of limiting elements may elucidate the mechanisms that shape ecological interactions and the functioning of food webs (Chen and Forschler 2016;Filipiak 2016;Filipiak and Weiner 2017b), thus illuminating the multielemental nutritional limitations imposed on the growth and development of saproxylophagous insects that include P, N, K, Na, Mg, Zn, and Cu (Filipiak and Weiner 2017a).…”

Krill vs salps: dominance shift from krill to salps is associated with higher dissolved N:P ratios

“…The relation between planktonic grazers and the dissolved nutrient pool in aquatic ecosystems is usually constrained by the stoichiometric demand of the consumer species involved and their species-specific excretion ratios. Several studies from other aquatic systems have pointed out the potentially severe effect of consumer driven changes in nutrient supply on food web dynamics 49,[57][58][59] , and more recent investigations of the WAP marine ecosystem have discussed similar effects 37 . Spatially or temporally heterogeneous aggregations of mobile organisms have the potential to generate biogeochemical hotspots that may modify patterns of nutrient remineralisation and ecosystem nutrient dynamics 60,61 .…”

Biogeographical distribution of microbial communities along the Rajang River–South China Sea continuum

“…Thus, it is essential to understand the dynamics and structure of microbial communities in them to assess their contribution towards biogeochemical fluxes such as carbon and nitrogen (Battin et al, 2008;Raymond et al, 2013), as well as phosphorus cycling (Hall et al, 2013). In addition, the fluxes as well as transformations of organic matter as well as nutrients in aquatic systems are environmentally driven by parameters such as temperature or the availability of nutrients in these ecosystems (Welti et al, 2017). In turn, various gradients (i.e physical, chemical, hydrological or even biological) contribute to the changes in the microbial diversity and distribution living within the lotic environments (Zeglin, 2015).…”