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Main project your organisation is involved with, in relation to (sub)tropical biodiversity:
Metabolismo planctónico: regulación bioquímica e impacto oceanográfico sobre la bomba biológica By producing CO2, plankton metabolism acidifies the ambient seawater. It leads to the release of particulate and dissolved organic carbon and nitrogen which, in turn, augments carbon and nitrogen fluxes in the ocean. This process modulates the CO2 buildup in the atmosphere. This proposal is concerned with respiratory CO2 production, O2 consumption, and ammonium excretion, three major facets of plankton metabolism. In the respiration part of the project we aim to introduce a new oceanographic proxy: the measurement of isocitrate dehydrogenase (IDH) to detect the CO2 production rate in zooplankton, phytoplankton, and bacteria. In addition, we plan to revolutionize the assessment of the respiratory O2 consumption proxy by introducing the fluorescent electron acceptor, resazurin. This modernization of the respiratory electron transport system (ETS) assay will greatly facilitate studies of mesopelagic and abyssopelagic metabolism. Using this new assay we will investigate the relationships between ETS and IDH activities and the physiological rate of respiration and then use the results to challenge the Metabolic Theory of Ecology. In these investigations we will use gradients of starvation to force respiration and the respiratory enzyme activities (IDH and ETS) to diverge in time-course experiments. The resulting data will be used to strengthen and to challenge our mathematical model of respiration. In a similar fashion we will use our glutamate dehydrogenase (GDH) assay to investigate ammonium excretion. For the experimental work we will use cultures of a hetero trophic dinoflagellate,and mysids isolated from Canary Island waters.
Campaña de Validación para el Estudio de un Modelo Mecanístico para el Metabolismo del Zooplancton (Camvalex) This proposal outlines of 2 cruises, called land-cruises. We sample the sea daily, quickly return to the coastal laboratory, analyse the samples, and conduct experiments with fresh plankton. The aim is to verify, experimentally, our new enzyme-kinetic mechanistic-models of respiration and ammonium excretion (Packard and Gomez, 2008) with fresh zooplankton samples taken from the natural environment. Sampling took place twice for 10 days each. The first in the spring maximum (February-March 2011). The second during the time of the maximum stratification in Canary Island coastal waters (September-October 2011).
EXZOME project Zooplankton metabolism strongly impacts pH changes as well as carbon and nitrogen fluxes in the ocean and these impacts influence the role of the ocean in modulating CO2 buildup in the atmosphere and climate change. Zooplankton metabolism has many components, both anabolic and catabolic; this proposal is concerned with the components of respiration and ammonium excretion. Its objective is to test a new mechanistic model of zooplankton metabolism (Packard and Gomez, 2008) by using it to predict respiration and ammonium excretion in both well-fed and starved zooplankton. The model is based on the understanding that respiratory oxygen utilization in zooplankton is caused by enzyme-catalyzed redox reactions in the respiratory electron transport system (ETS) and that the physiological rate of ammonium excretion is caused by the NH4+ producing reaction catalyzed by glutamate dehydrogenase. Here we argue that this ETS-based model can be used to predict zooplankton respiratory oxygen consumption. An important aspect of this model is its use of Michaelis-Menten kinetics to express the substrate dependence of the enzyme activities between their maximal and minimal velocities. By testing this model we will be testing all the algorithms and assumptions upon which it is based. In this proposal, the investigation is performed by a multidisciplinary research team.