Energy Flow Through Marine Ecosystems: Confronting Transfer Efficiency

Transfer efficiency is a key parameter describing ecosystem structure and function used to estimate fisheries production; however, it also one of the most uncertain parameters. Questions remain about how habitats, food resources, fishing pressure, spatiotemporal scales, as well temperature, primary production, other climate drivers impact transfer efficiency. Direct measurements are difficult, but observations marine population abundances, diets, productivity, stable isotope analysis, models integrating these constraints can provide estimates. Recent estimates suggest that more variable than previously thought, compounding uncertainties in predictions projections. Increased understanding factors contributing variation will improve projections change impacts on ecosystems. proportion energy passed between nodes webs. It an emergent, unitless property difficult measure, responds dynamically environmental changes. Because consequences changes compound through ecosystems, slight variations have large effects availability for top predators. Here, we review processes controlling efficiency, approaches it, known across ocean biomes. Both process-level analysis observed macroscale ecosystem-scale highly variable, impacted by fishing, decline with change. important fully resolve effectively anticipate ecosystems resources. ingested material broken down digestive enzymes fuel organism’s metabolic processes. Unassimilated egested. model quantifies relationships biodiversity flow system interconnected feeding or chains. Illustrations depict resources consumers linked lines symbolize relationship (e.g., Figure 1D). Nodes represent predator prey, species, trophic levels, functional groups size classes. mathematical representation biomass flows from producers then secondary higher ratio average mass individual its prey. generation energy. Primary production refers synthesis organic compounds carbon dioxide often via photosynthesis. Secondary involves consumption another organism. rate production. ability recover original state following disturbance. web individuals their sizes. naturally occurring, non-radioactive atoms same element different numbers neutrons. The fewer neutrons lighter mass, which results faster chemical reaction rates, may lead preference uptake organisms. Comparing ratios nitrogen isotopes organismal tissues prey elucidate formed level. resource converted into consumer calculated node web. position within based number links producer. such phytoplankton plants level 1, herbivores 2, carnivores at least 3. Non-integer levels result mixed diets. Detritus assigned 1. chain.