Search results for "mixing model"
showing 9 items of 9 documents
Inferring phytoplankton community composition with a fatty acid mixing model
2015
Abstract. The taxon specificity of fatty acid composition in algal classes suggests that fatty acids could be used as chemotaxonomic markers for phytoplankton composition. The applicability of phospholipid-derived fatty acids as chemotaxonomic markers for phytoplankton composition was evaluated by using a Bayesian fatty acid-based mixing model. Fatty acid profiles from monocultures of chlorophytes, cyanobacteria, diatoms, euglenoids, dinoflagellates, raphidophyte, cryptophytes and chrysophytes were used as a reference library to infer phytoplankton community composition in five moderately humic, large boreal lakes in three different seasons (spring, summer and fall). The phytoplankton commu…
Stable isotope analysis reveals trophic segregation between the invasive zebra mussel Dreissena polymorpha and the native duck mussel Anodonta anatin…
2022
AbstractNon-indigenous freshwater bivalves negatively affect invaded ecosystems through different mechanisms, including inter-specific competition for trophic resources. Here, we investigated in Lake Trasimeno (Central Italy) the diet of the invasive Dreissena polymorpha and the native Anodonta anatina. δ15N and δ13C stable isotopes were measured in winter and summer in bivalves, phytoplankton, and sedimentary organic matter (SOM); the relative dietary contributions of the two resources were determined using Bayesian mixing models. To elucidate the different carbon and nitrogen pools characterizing the study site, isotopic analyses were extended to zooplankton and to representatives of the …
A Bayesian stable isotope mixing model for coping with multiple isotopes, multiple trophic steps and small sample sizes
2022
We introduce a Bayesian stable isotope mixing model for estimating the relative contributions of different dietary components to the tissues of consumers within food webs. The model is implemented with the probabilistic programming language Stan. The model incorporates isotopes of multiple elements (e.g. C, N, H) for two trophic levels, when the structure of the food web is known. In addition, the model allows inclusion of latent trophic levels (i.e. for which no empirical data are available) intermediate between sources and measured consumers. Running the model in simulations driven by a real dataset from Finnish lakes, we tested the sensitivity of the posterior distributions by altering c…
Origin of atmospheric lead in Johannesburg, South Africa
2006
International audience; The origin of lead in the atmosphere of Johannesburg, South Africa was investigated on the basis of elemental and lead isotopic analyses of coals, mine dumps, gasoline, and about 30 epiphytic lichen samples. Lead predominantly comes from automotive exhausts in urban and suburban areas, as leaded antiknock additives were still in use in South Africa at the time of the study. Although dust emissions from the numerous mine-tailing dumps were expected to contribute significantly to the heavy metal budget, the southern townships that are surrounded by the dumps (such as Soweto and other historically Black residential areas) do not appear to be more than partially influenc…
Trophic structure of vermetid reef community: High trophic diversity at small spatial scales
2013
Stable isotopes were used to investigate contributions of autochthonous (i.e. benthic: epilithon and macroalgae) and allochthonous (i.e. pelagic: phytoplankton) organic matter sources to the diet of suspension-feeders, grazers and predators associated to small reef-pools (cuvettes) created by the reef-building species Dendropoma petraeum in the north-western coast of Sicily (Italy). Contributions of potential food sources were calculated using Bayesian mixing-models and integrated to a multivariate approach to highlight the diversity of C and N pathways within Dendropoma cuvettes. Both pelagic and benthic organic matter sources were exploited by benthic consumers, although clear differences…
Suitability of Phytosterols Alongside Fatty Acids as Chemotaxonomic Biomarkers for Phytoplankton
2016
The composition and abundance of phytoplankton is an important factor defining ecological status of marine and freshwater ecosystems. Chemotaxonomic markers (e.g., pigments and fatty acids) are needed for monitoring changes in a phytoplankton community and to know the nutritional quality of seston for herbivorous zooplankton. Here we investigated the suitability of sterols along with fatty acids as chemotaxonomic markers using multivariate statistics, by analyzing the sterol and fatty acid composition of 10 different phytoplankton classes including altogether 37 strains isolated from freshwater lakes. We were able to detect a total of 47 fatty acids and 29 sterols in our phytoplankton sampl…
Guano-Derived Nutrient Subsidies Drive Food Web Structure in Coastal Ponds.
2016
A stable isotope study was carried out seasonally in three coastal ponds (Marinello system, Italy) affected by different gull guano input to investigate the effect of nutrient subsidies on food web structure and dynamics. A marked 15N enrichment occurred in the pond receiving the highest guano input, indicating that gull-derived fertilization (guanotrophication) had a strong localised effect and flowed across trophic levels. The main food web response to guanotrophication was an overall erosion of the benthic pathway in favour of the planktonic. Subsidized primary consumers, mostly deposit feeders, switched their diet according to organic matter source availability. Secondary consumers and,…
Contribution of planktonic and benthic food sources to the diet of the reef-forming vermetid gastropod Dendropoma petraeum in the western Mediterrane…
2012
Abstract In the Mediterranean Sea, the vermetid Dendropoma petraeum (Monterosato, 1884) forms highly biodiverse reefs that have received increasing attention in recent years although very little is known about the food habit of this species. The main goal of this study was to describe the trophic role of planktonic and benthic food sources for D. petraeum . Specimens from three morphological zones of the reef (inner edge, cuvette and outer edge) at two sites with different wave exposure along the north-western coast of Sicily (Italy; western Mediterranean) were compared for δ 13 C and δ 15 N. Isotopic determinations were also carried out on potential food sources identified in epilithon, re…
Complementary approaches for assessing protein sources in fish feed
2018
Fluctuating fishmeal (FM) prices and declining marine fish stocks have led to the current trend of replacing dietary FM with plant proteins (PP) in fish feed. PPs offer challenges both with respect to nutritional quality and the occurrence of antinutrients. The assessment of utilisation efficiency of PPs for growth is important for the sustainable production of fish feed. The overall aim of this thesis was to investigate the applicability of stable isotope analysis in combination with respirometry in the evaluation of dietary PPs for juvenile rainbow trout (Oncorhynchus mykiss). The dietary PPs were corn gluten meal (CGM), rapeseed protein concentrate (RPC) and potato protein (PoP). Complet…