Aquatic ecosystems are varied and complex, and cannot be described in a single unified manner. However, each system, whether it is a pelagic, coastal marine or riverine, still follows certain patterns of energy and nutrient transfer. The field of Ecological Stoichiometry aims at understanding the balance of energy and chemical elements in ecological interactions. It examines the trophic relationships linking the elemental physiology of organisms with their food web interactions and ecosystem function. In particular, it explores nutrient dynamics with concepts such as stoichiometric food quality imposed by elemental co-limitation, consumer-driven nutrient recycling or the growth rate hypothesis. Ecological Stoichiometry has been applied on different levels of biological organization, from organelle biochemistry to ecosystems and across diverse organisms from bacteria to plants and animals. In this session, we welcome contributions from the broad community to show how Ecological Stoichiometry can improve our understanding in diverse fields, including studies on individuals, populations, communities, ecosystems, and even human alteration to the Earth system. This session also calls for contributions from across the range of approaches (theoretical, experimental, observational, and modelling) that can be used to investigate the effects of changing environments with the help of Ecological Stoichiometry on all aspects of aquatic ecosystems.
Lead Organizer: Cecilia Laspoumaderes, Univ. Nac. del Comahue - INIBIOMA- CONICET (claspoumaderes@comahue-conicet.gob.ar)
Co-organizers:
Cedric Meunier, Biologische Anstalt Helgoland, Alfred Wegener Institut, Germany (Cedric.Meunier@awi.de)
Maarten Boersma, Biologische Anstalt Helgoland, Alfred Wegener Institut, Germany (Maarten.Boersma@awi.de)
Erik Sperfeld, Universität Greifswald, Germany (erik.sperfeld@uni-greifswald.de)
Presentations
03:00 PM
Global patterns and drivers of C:N:P in marine ecosystems (6176)
Primary Presenter: Adam Martiny, University of California, Irvine (amartiny@uci.edu)
The stoichiometry coupling of carbon, nitrogen, and phosphorus cycles is a fundamental component of ecosystems and biogeochemical cycles. However, several competing hypotheses have been proposed invoking unique biochemical mechanism and associated environmental drivers to describe CNP variation. To test each biochemical mechanism, we used phytoplankton culture experiments, omics’, and the global Bio-GO-SHIP campaign measuring ecosystem CNP. First, we examined Synechococcus cell chemistry using laboratory chemostats and mass spectrometry proteomics. Here, we found that nutrient stress accounted for most CNP variability and induced tradeoffs between nutrient acquisition and ribosomes. There was a significant impact of temperature on ribosome and heat-shock proteins leading to minor stoichiometric changes. Ecosystem variation in CNP supported the culture experiments. Multiple dimensions of nutrient stress were important for CNP in low latitude ecosystems. Concurrent metagenomes separated each elemental stress type and revealed that interactions between nutrient supply rate and N vs. P stress is critical for hemispheric and regional CNP variability. In contrast, sea-surface temperature was important for CNP under nutrient replete and possibly high temperature conditions. Future climate projections suggest that CP and NP will increase at high latitudes but are uncertain at low latitudes due to unconstrained changes to nutrient stress. Our observations suggest a systematic biochemical regulation of elemental stoichiometry among ocean ecosystems, but future changes are uncertain.
03:15 PM
CONSTRAINING THE CELLULAR RESPONSE OF PHYTOPLANKTON TO TEMPERATURE AND RESOURCE AVAILABILITY (4636)
Primary Presenter: Zoe Aarons, MIT-WHOI Joint Program (zsaarons@mit.edu)
Understanding how phytoplankton respond to changes in temperature and nutrient supply rates is necessary for understanding carbon flow in changing climates. The magnitude of ocean carbon storage is partly modulated by the growth rate and elemental stoichiometry of autotroph biomass, so models relating the cellular composition of phytoplankton and environmental conditions will be a useful tool. Community-wide growth rate are expected to increase with temperature, but this response is dampened when nutrients are limiting. We will discuss an adaptation of a cellular allocation model (Inomura et al., 2020) which allocates carbon, nitrogen, and phosphorus to key macromolecular pools in autotrophs, such that growth rate and stoichiometry are related as a function of these pool sizes. We include temperature-dependent cellular processes based on theories of enzyme kinetics as well as explicit allocation to nutrient uptake to resolve the combined response to temperature and nutrient changes. We will employ the model to discuss how resource availability drives the response of phytoplankton to both spatial and temporal variability in these environmental parameters.
03:30 PM
Stoichiometric mismatch causes a warming-induced regime shift in an experimental plankton community (7419)
Primary Presenter: Sebastian Diehl, Umea University (sebastian.diehl@umu.se)
When consumers and their resources respond differently to warming, this can lead to seasonal mismatches between consumer demands and resource availability. A less acknowledged threat to the coherence of consumer-resource dynamics is mismatch in food quality. Many plant and algal communities respond to warming with shifts towards more carbon-rich species and growth forms, thus diluting essential elements in their biomass and enhancing the mismatch with herbivore nutrient requirements. We report on a mesocosm experiment with a spring plankton community where warming caused a dramatic regime shift that coincided with extreme stoichiometric mismatch. At ambient temperatures, a typical spring succession developed, where a moderate bloom of nutritionally adequate phytoplankton was grazed down to a clear-water phase by a developing Daphnia population. While warming accelerated initial Daphnia population growth, it speeded up algal growth rates even more, triggering a massive phytoplankton bloom of poor food quality. Consistent with a stoichiometric producer-grazer model, accelerated phytoplankton growth promoted the emergence of an alternative system attractor, where extremely low phosphorus content of abundant algal food drove Daphnia to extinction. The experiment is a demonstration of the ‘paradox of energy enrichment’ (= grazer starvation in abundant but nutritionally imbalanced food). It supports the notion that warming can exacerbate the stoichiometric mismatch at the plant-herbivore interface and limit energy transfer to higher trophic levels.
03:45 PM
A common temperature dependence of nutritional demands in ectotherms (6608)
Primary Presenter: Cecilia Laspoumaderes, AWI - CONICET (claspoumaderes@comahue-conicet.gob.ar)
In light of ongoing climate change, it is increasingly important to know how nutritional requirements of ectotherms are affected by changing temperatures. Here, we analyse the wide thermal response of phosphorus (P) requirements via elemental gross growth efficiencies of Carbon (C) and P, and the Threshold Elemental Ratios in different aquatic invertebrate ectotherms: the freshwater model species Daphnia magna, the marine copepod Acartia tonsa, the marine heterotrophic dinoflagellate Oxyrrhis marina, and larvae of two populations of the marine crab Carcinus maenas. We show that they all share a non-linear cubic thermal response of nutrient requirements. Phosphorus requirements decrease from low to intermediate temperatures, increase at higher temperatures and decrease again when temperature is excessive. This common thermal response of nutrient requirements is of great importance if we aim to understand or even predict how ectotherm communities will react to global warming and nutrient-driven eutrophication.
04:00 PM
Effects of increasing temperature and parasites on nutrient excretion by pumpkinseed (6751)
Primary Presenter: Carrie Sharitt, Miami University, OH (sharitca@miamioh.edu)
Consumers play an important role in nutrient cycling in many aquatic ecosystems by releasing nitrogen, phosphorus, and carbon. In some cases animal-mediated element cycling makes a significant contribution to whole ecosystem flux of these elements. Temperature and body size are known to impact nutrients excretion rates. However, little is known about how parasites impact excretion; yet some models suggest that parasites will increase due to climate change. Therefore, understanding the synergistic influence of climate warming and parasites on animal excretion remains an open question. In lakes of the southern boreal forest, where temperatures are rising, pumpkinseed sunfish (Lepomis gibbosus) are common and abundant fish, and in some lakes, are infected by trematodes (Uvulifer ambloplitis), (Clinostomum marginatum) and cestodes (Proecocephalus embloplites).Working at Station de Biologie des Laurentides, we exposed pumpkinseed to one of three temperatures(20°, 25, or 30°C) and variable parasite infections and measured their nutrient excretion rates. Phosphorus (P) excretion was negatively correlated with parasite load and positively correlated with temperature, while nitrogen (N) excretion was not correlated with either parasite load or temperature. Thus, the N:P ratio excreted also increased significantly with parasite load and decreased with temperature. Parasites may sequester some P ingested by fish, leading to lower P excretion. Analysis of fish body nutrient contents will be used to address how parasites (and warming temperatures) alter stoichiometric flux through fish.
04:15 PM
Zooplankton-phytoplankton interactions in a future world, what can ecological stoichiometry tell us? (7181)
Primary Presenter: Maarten Boersma, Alfred-Wegener-Institut (AWI) (maarten.boersma@awi.de)
Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Germany There has been considerable debate recently, how temperature affects nutritional demands and food selectivity in poikilotherms. Here, we will use the results of the studies published to date on the interactions between changing environmental conditions and grazer nutritional demands to assess the potential consequences of changes in environmental conditions on the interaction between zooplankton and their prey. Complex reactions to temperature change have been reported in the literature and by ourselves, and here we will assess the potential consequences of these reactions for seasonal and spatial distributions of zooplankton and their prey. Our analysis suggests that changes in phenology of zooplankton, which currently are largely attributed to changes in water temperature may need a more elaborate explanation.
SS040A Ecological Stoichiometry in a Dynamic World: Exploring the Ecology of Changing Environments Through Theory, Patterns, Processes and Experiments.
Description
Time: 3:00 PM
Date: 6/6/2023
Room: Auditorium Mallorca