This research addresses the following questions:

• What are the patterns and thresholds by which basal resources in freshwater and marine ecosystems change in response to increased nutrient availability?
•  Can resulting changes in ecosystem functions be predicted based on threshold elemental ratio requirements of consumers?
• How does the resupply of nutrients from consumers contribute to functioning aquatic ecosystems?

Project overview

Many of the mechanistic pathways by which nutrients affect aquatic ecosystem functions occur through the supply, uptake and storage of nutrients in specific ratios, or their stoichiometry. Our lab is investigating how the threshold elemental ratio needs of consumers can predict their response to excess nutrients in streams and their effects on ecosystem functions (Tant et al. 2013). We have also determined how the stoichiometric change in detrital resources due to nutrient pollution is an important indicator of carbon loss (Manning et al. 2015, Manning et al. 2016).

Most systems without significant human influence are naturally low in nutrients and depend on consumers to feed on material and excrete or egest the associated nutrients to make them available to other consumers. This consumer-driven nutrient recycling (CNR) is important in many systems where consumer biomass has been lost, such as overfished nearshore marine systems (Allgeier et al. 2014). Restoration of fish populations (through e.g., artificial reef development) can help bring back this important and naturally derived source of nutrients (Allgeier et al. 2018).