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[en] The analysis was carried out in the geographical area for the ERFEN understood among the 2 degrade at the 6 degrade of latitude N and 82 degrade of longitude W, specifically in the areas to the north of the Colombian Pacific (Cabo Corrientes) Profile Buenaventura-Malpelo and Profile Tumaco, being studied the superficial phytoplankton in the two characteristic times of the Pacific and taking like reference the existent historical data. The Incidence of the environmental parameter is presented, as it is the temperature on the distribution of a marine ecosystem as it is the superficial marine phytoplankton. It was observed that the identified species as the biological Indicators of the southeastern oscillation, coincided equally with the beginning of the indicative thermal anomalies of the evolution of a warm event with the obtained data it was visualized that the composition of the opposing phytoplankton during the period of study, reflective a mixture of elements with very diverse ecological width, reflecting waters of different provenience: Coastal and oceanic. Bigger information is contributed with the end to supplement the knowledge on the indicative organisms that detect in early form the environmental changes taken place by the phenomenon El Nino, and of this form, to complete the physical-chemical and fishing studies allowing to give approaches in the political orientation in the activities that could be affected, such as fishing strategy, measures on aquiculture, marketing decision, handling of hydrobiologic resources, etc
[en] An oil from Pacific krill (Euphausia pacifica) has a high content of PUFAs and phospholipids. The sediment was formed with homogenization of krill oil and maltodextrin (MD; dextrose equivalent (DE) = 19) solution using sodium caseinate, gum arabic, hydrolyzed whey protein or modified starch as a surfactant. Quillaja saponin could form the emulsion without the sediment. MD (28.5 wt%) was solubilized with distiller water (50 wt%) and mixed with krill oil (20wt%) and Quillaja saponin (1.5 wt%). The homogenized solution was spray-dried using Okawara-L8 spray dryer with a centrifugal atomizer. Spray-dried powder was evaluated in the oil-droplet size and surface-oil content. (Author)
[en] A simple phytoplankton-zooplankton nonlinear dynamical model was proposed to study the coexistence of all the species and a Hopf bifurcation was observed. In order to study the effect of environmental robustness on this system, we have stochastically perturbed the system with respect to white noise around its positive interior equilibrium. We have observed that the system remains stochastically stable around the positive equilibrium for same parametric values in the deterministic situation
[en] Phytoplankton are key components of ecosystems. Their growth is deeply influenced by temperature. In a context of global change, it is important to precisely estimate the impact of temperature on these organisms at different spatial and temporal scales. Here, we review the existing deterministic models used to represent the effect of temperature on microbial growth that can be applied to phytoplankton. We first describe and provide a brief mathematical analysis of the models used in constant conditions to reproduce the thermal growth curve. We present the mechanistic assumptions concerning the effect of temperature on the cell growth and mortality, and discuss their limits. The coupling effect of temperature and other environmental factors such as light are then shown. Finally, we introduce the models taking into account the acclimation needed to thrive with temperature variations. The need for new thermal models, coupled with experimental validation, is argued.
[en] Haloacetic acids (HAAs) are environmental contaminants found in aquatic ecosystems throughout the world as a result of both anthropogenic and natural production. The ecological risk posed by these compounds to organisms in freshwater environments, with a specific focus on aquatic macrophytes, was characterized. The plants evaluated were Lemna gibba, Myriophyllum spicatum and M. sibiricum and the HAAs screened were monochloroacetic acid (MCA), dichloroacetic acid (DCA), trichloroacetic acid (TCA), trifluoroacetic acid (TFA) and chlorodifluoroacetic acid (CDFA). Laboratory toxicity data formed the basis of the risk assessment, but field studies were also utilized. The estimated risk was calculated using hazard quotients (HQ), as well as effect measure distributions (EMD) in a modified probabilistic ecological risk assessment. EMDs were used to estimate HAA thresholds of toxicity for use in HQ assessments. This threshold was found to be a more sensitive measure of low toxicity than the no observed effect concentrations (NOEC) or the effective concentration (EC10). Using both deterministic and probabilistic methods, it was found that HAAs do not pose a significant risk to freshwater macrophytes at current environmental concentrations in Canada, Europe or Africa for both single compound and mixture exposures. Still, HAAs are generally found as mixtures and their potential interactions are not fully understood, rendering this phase of the assessment uncertain and justifying further effects characterization. TCA in some environments poses a slight risk to phytoplankton and future concentrations of TFA and CDFA are likely to increase due to their recalcitrant nature, warranting continued environmental surveillance of HAAs. - Current environmental concentrations of haloacetic acids do not pose a risk to aquatic macrophytes, but could impact plankton
[en] In this paper, a mathematical model consisting of two harmful phytoplankton and zooplankton with discrete time delays is considered. We prove that a sequence of Hopf bifurcations occur at the interior equilibrium as the delay increases. Meanwhile, the phenomenon of stability switches is found under certain conditions. The direction of the Hopf bifurcations and the stability of the bifurcating periodic solutions are determined by using the theory of normal form and center manifold. Numerical simulations are given to support the theoretical results.
[en] It has been reported that the minimal spatially extended phytoplankton–zooplankton system exhibits both temporal regular/chaotic behaviour, and spatiotemporal chaos in a patchy environment. As a further investigation by means of computer simulations and theoretical analysis, in this paper we observe that the spiral waves may exist and the spatiotemporal chaos emerge when the parameters are within the mixed Turing–Hopf bifurcation region, which arises from the far-field breakup of the spiral waves over a large range of diffusion coefficients of phytoplankton and zooplankton. Moreover, the spatiotemporal chaos arising from the far-field breakup of spiral waves does not gradually invade the whole space of that region. Our results are confirmed by nonlinear bifurcation of wave trains. We also discuss ecological implications of these spatially structured patterns. (general)
[en] Coastal phytoplankton is affected by natural and anthropic processes. To analyze the influence of some of these processes, the spatial and temporal distribution of phytoplankton in the Gulf of Cariaco, Sucre state, was evaluated. Samples (0-10 m) were collected with Niskin bottles (5 L) in seven stations between February 2014 and January 2015. Transparency (m), salinity (UPS), temperature (Celsius degrade), chlorophyll concentration a (mg m-3), and phytoplankton abundance (org mL-1) were measured. A nonparametric analysis of variance and multivariate methods (PCA, CCA, and nMDS) were used to analyze the results. The 0 - 10 m stratum was homogeneous with respect to all variables except temperature which ranged from 20.1 to 29.1 Celsius degrade (March and October, respectively). Temporally, the variables were heterogeneous. Biomass fluctuated between undetectable (ND) and 17.5 mg m-3 (December and March). While microalgal abundance oscillated between 0.24 and 1.85 x 103 org mL-1 (April and February). Diatoms, nanoflagellates, and coccolithophorids dominated the community. The first two groups were associated with turbulent, nutrient-rich waters. The nMDS separated the community into the three periods previously described for the region. Likewise, the CCA detected that wind speed and temperature were the most influential variables on the phytoplankton community during upwelling and relaxation period, respectively. In the transition period, none of the variables studied affected the community. This is the first time that coccolithophores are reported as part of the dominant flora in the Gulf of Cariaco. This change suggests modifications in the oceanographic conditions of the study area.
[en] It is known that natural systems are undeniably subject to random fluctuations, arising from either environmental variability or internal effects. In this paper, we present a spatial version of the phytoplankton–zooplankton model that includes some important factors such as external periodic forces, noise, and diffusion processes. The spatially extended phytoplankton–zooplankton system is from the original study by Scheffer (Scheffer 1991 Oikos 62 271). Our results show that the spatially extended system exhibits a resonant pattern and frequency-locking phenomena. The system also shows that the noise and the external periodic forces play a constructive role in the Scheffer's model: (i) the noise can enhance the oscillation of phytoplankton species' density and form large clusters in space when the noise intensity is within a certain interval; (ii) the external periodic forces can induce 4:1 and 1:1 frequency-locking and spatially homogeneous oscillation phenomena to appear; and (iii) resonant patterns are observed in the system when the spatial noises and external periodic forces are both turned on. Moreover, we find that the 4:1 frequency locking transforms into 1:1 frequency locking when the noise intensity is increased. In addition to elucidating our results outside the domain of Turing instability, we provide further analysis of linear stability with the help of numerical calculation using the Maple software. Significantly, oscillations are enhanced in the system when the noise term is present. These results indicate that the oceanic plankton bloom may be partly due to interplay between the stochastic factors and external forces instead of deterministic factors. These results also may help us to understand the effects arising from the undeniable susceptibility to random fluctuations in oceanic plankton bloom