Zooplankton oxygen consumption and nutrient release in relation to species composition, animals size and enviromental conditions in the Baltic Sea during May and August

[EN] Zooplankton metabolism in terms of oxygen consumption and ñutrient reléase (ammonia, phosphate) were measiu'ed in the Baltic Sea, a températe área with high envirormiental changes both in space and in time. Plankton of the surface layer were analysed with balance measurements in 4 size classes between 50 and 1000 nm during spring in 1988, 1990 and 1991, in summer 19^8 and 1990 as well. The use of electrón transport system (ETS), and the Glutamate Dehydrogenase (GDH) activity as indicators for respiration and ammonia reléase respectively, enlarged the data density and made a three dimensional resolution available (May 1990, 1991). Data are in the range of the latitudinal dependend magnitude. They reflect slight interannual, more seasonal and regional aspects. Animáis size, temperature, food concentration, and species composition influence the specific rates

The use of image analysis systems for the assesment of zooplankton physiological rates and carbon fluxes

Trabajo realizado por: Garijo, J. C., Hernández León, S.

The use of AARS activity as a proxy for zooplankton and ichthyoplankton growth rates

Programa de doctorado en Oceanografía

Understanding the zooplankton ammonium excretion: from biogeochemical implications to intracellular regulatory mechanisms

[EN] This thesis focuses on the zooplankton NH4+ regeneration that supports about the 80% of the phytoplankton requirements. In its more oceanographic facet, it elucidates the control that the mesozooplankton community exerts on the primary productivity in the northern Benguela, and models the N-fluxes from zooplankton NH4+ excretion. At the physiological level, it examines the relationship between the NH4+ excretion and its associated biochemistry. Assuming the substrate availability as the critical factor in regulating the velocity of NH4+ production, a bisubstrate model was developed to predict its actual rate in zooplankton. Overall, this research provides knowledge about the implications of zooplankton NH4+ excretion on the biogeochemical cycles, and introduces new insights into the study of this process from enzymatic measurements.

Testing zooplankton secondary production against growth in the marine mysid, "Leptomysis lingvura" (G.O. Sars, 1866)

[EN]Zooplankton growth and secondary production are key input parameters in marine ecosystem modelling, but their direct measurement is difficult to make. Accordingly, zooplanktologists have developed several statistical-based secondary production models. Here, three of these secondary production models are tested in Leptomysis lingvura (Mysidacea, Crustacea). Mysid length was measured in two cultures grown on two different food concentrations. The relationship between length and dry-mass was determined in a pilot study and used to calculate dry-mass from the experimental length data. Growth rates ranged from 0.11 to 0.64 , while secondary production rates ranged from 1.77 to 12.23 mg dry-mass . None of the three selected models were good predictors of growth and secondary production in this species of mysid.

Understanding the zooplankton ammonium excretion : from biogeochemical implications to intracellular regulatory mechanisms

[EN]Zooplankton play a key role in marine ecosystems and their biogeochemical cycles. They exert control over the primary productivity through the consumption of organic matter and, at the same time, the release of nutrients that sustains the phytoplankton growth. This thesis focuses on the NH+ 4 excretion processes related to these heterotrophic organisms that support, at a global scale, about the 80% of the phytoplankton requirements. However, thereisno clear constant pattern in the zooplankton contribution to theNH+ 4 regeneration throughout thedifferent pelagic ecosystems, so continuousmonitoring of thismetabolic processisessential at widetemporal and spatial scales...