Methodological limitations and conceptual implications of nutritional estimations

Trophic interactions play a critical role in regulating ecosystem functioning. Advances in trophic ecology have shifted the focus from characterizing resources based on a single ‘currency' such as energy or biomass to more complex multidimensional approaches that consider the resource quality, hence require detailed estimation of different nutrients. For this purpose, ecologists use a wide plethora of extraction and quantification methods that differ substantially in precision and accuracy and vary in efficiency across sample types and taxa. Yet, ecologists seem largely oblivious to these methodological drawbacks and their severe theoretical implications. Focusing on the three main macro-nutrients groups; proteins, lipids and carbohydrates, we provided an overview of the main extraction and quantification methods and their inherent limitations, and discussed possible consequences for ecology research and theory development. We urge ecologists to adopt a standard method for estimating each macronutrient group or to use multiple methods when feasible, until more accurate and precise chromatographic methods become accessible. We hope that our study will raise awareness to the many shortcomings of macro-nutrient estimations to assist in strengthening and further developing the important field of trophic ecology.