Grazing behavior and winter phytoplankton accumulation

Recent observations have shown that phytoplankton biomass increases in the North Atlantic during winter, even when the mixed layer is deepening and light is limited. Current theories suggest that this is due to a release from grazing pressure. Here we demonstrate that the often-used grazing models that are linear at low phytoplankton concentration do not allow for a wintertime increase in phytoplankton biomass. However, mathematical formulations of grazing as a function of phytoplankton concentration that are quadratic at low concentrations (or more generally decrease faster than linearly as phytoplankton concentration decreases) can reproduce the fall to spring transition in phytoplankton, including wintertime biomass accumulation. We illustrate this point with a minimal model for the annual cycle of North Atlantic phytoplankton designed to simulate phytoplankton concentration as observed by BioGeoChemical-Argo (BGC-Argo) floats in the North Atlantic. This analysis provides a mathematical framework for assessing hypotheses of phytoplankton bloom formation.

Drivers of phytoplankton responses to summer storms in a stratified lake: a modelling study

Extreme wind events affect lake phytoplankton amongst others by deepening the mixed layer and increasing internal nutrient loading. Both increases and decreases of phytoplankton biomass after storms have been observed, but the precise mechanisms driving these responses remain poorly understood or quantified. In this study, we coupled a one-dimensional physical model to a biogeochemical model to investigate the factors regulating short-term phytoplankton responses to summer storms, now and under expected high-temperature conditions. We simulated physical, chemical and biological dynamics in Lake Erken, Sweden, to take advantage of a long-term time series that we used to calibrate our model. We found that wind storms could increase or decrease the phytoplankton concentration one week after the storm, depending on antecedent lake physical and chemical conditions. Storms had little effect on phytoplankton biomass if the mixed layer was deep prior to storm exposure. Higher incoming shortwave radiation and hypolimnetic nutrient concentration boosted growth, whereas higher surface water temperatures decreased phytoplankton concentration after storms. Medium-intensity wind speeds resulted in more phytoplankton biomass after storms than high-intensity wind. Simulations under a future climate scenario did not show marked differences in the way wind affects phytoplankton growth following storms. Our study shows that storm impacts on lake phytoplankton are complex and likely to vary as a function of local environmental conditions.

An investigation of grazing behaviors that result in winter phytoplankton biomass accumulation

Recent observations have shown that phytoplankton biomass increases in the North Atlantic during winter, even when the mixed layer is deepening and light is limited. Current theories suggest that this is due to a release from grazing pressure. Here we demonstrate that the often-used grazing models that are linear at low phytoplankton concentration do not allow for a wintertime increase in phytoplankton biomass. However, certain mathematical formulations of grazing that are quadratic (or more generally non-linear) in phytoplankton concentration at low concentrations can reproduce the fall to spring transition in phytoplankton, including wintertime biomass accumulation. We illustrate this point with a minimal model for the annual cycle of North Atlantic phytoplankton designed to simulate phytoplankton concentration as observed by BioGeoChemical-Argo (BGC-Argo) floats in the North Atlantic. This analysis provides a mathematical framework for assessing hypotheses of phytoplankton bloom formation.

Climate change in a conceptual atmosphere–phytoplankton model

We develop a conceptual coupled atmosphere–phytoplankton model by combining the Lorenz'84 general circulation model and the logistic population growth model under the condition of a climate change due to a linear time dependence of the strength of anthropogenic atmospheric forcing. The following types of couplings are taken into account: (a) the temperature modifies the total biomass of phytoplankton via the carrying capacity; (b) the extraction of carbon dioxide by phytoplankton slows down the speed of climate change; (c) the strength of mixing/turbulence in the oceanic mixing layer is in correlation with phytoplankton productivity. We carry out an ensemble approach (in the spirit of the theory of snapshot attractors) and concentrate on the trends of the average phytoplankton concentration and average temperature contrast between the pole and Equator, forcing the atmospheric dynamics. The effect of turbulence is found to have the strongest influence on these trends. Our results show that when mixing has sufficiently strong coupling to production, mixing is able to force the typical phytoplankton concentration to always decay globally in time and the temperature contrast to decrease faster than what follows from direct anthropogenic influences. Simple relations found for the trends without this coupling do, however, remain valid; just the coefficients become dependent on the strength of coupling with oceanic mixing. In particular, the phytoplankton concentration and its coupling to climate are found to modify the trend of global warming and are able to make it stronger than what it would be without biomass.

Climate change in a conceptual atmosphere–plankton model

We develop a conceptual coupled atmosphere–phytoplankton model by combining the Lorenz'84 general circulation model and the logistic population growth model under the condition of a climate change due to a linear time dependence of the strength of anthropogenic atmospheric forcing. The following types of couplings are taken into account: (a) the temperature modifies the total biomass of phytoplankton via the carrying capacity, (b) the extraction of carbon dioxide by phytoplankton slows down the speed of climate change, (c) the strength of mixing/turbulence in the oceanic mixing layer is in correlation with phytoplankton productivity. We carry out an ensemble approach (in the spirit of the theory of snapshot attractors) and concentrate on the trends of the average phytoplankton concentration and average temperature contrast between the pole and equator, forcing the atmospheric dynamics. The effect of turbulence is found to have the strongest influence on these trends. Our results show that (a) sufficiently strong mixing is able to force the typical phytoplankton concentration to always decay globally in time, and the temperature contrast to decrease faster than what follows from direct anthropogenic influences. Simple relations found for the trends without this coupling do, however, remain valid, just the coefficients become dependent on the strength of coupling with oceanic mixing. In particular, the phytoplankton concentration and its coupling to climate is found to modify the trend of global warming, and is able to make it stronger than what it would be without biomass.

TINGKAT KESUBURAN PERAIRAN KOLAM AGROWISATA UIR DITINJAU DARI KONSENTRASI KLOROFIL-a PHYTOPLANKTON DI KECAMATAN SIAK HULUKABUPATEN KAMPARPROVINSI RIAU

This study aims to determine the level of water fertility in the UIR Agro-tourism pond in the District of Siak Hulu, Kampar Regency, Riau Province based on the concentration of chlorophyll-a phytoplankton. The study was carried out for 6 months in the Agro-tourism pond in Riau Islamic University. Analysis of water fertility in situ and ex-situ. The parameters measured were chlorophyll-a phytoplankton concentration and water quality. The method used is a case study (survey). The treatment in this study was 3 replications in one week on the clock and the same pool sequence. The results showed that the pond fertility rate of UIR Agro-tourism was quite productive, namely chlorophyll-a concentration of 1-20 µg / l with an abundance of phytoplankton of 104 cells / l.

In situ long-term monitoring of cardiac activity of two bivalve species from the White Sea, the blue mussel Mytilus edulis and horse mussel Modiolus modiolus

Cardiac activity of two White Sea Bivalvia species – Mytilus edulis and Modiolus modiolus – was monitored in situ for one full calendar year every 4 days. During the year, we also assessed the temperature and salinity of the ambient seawater (at intervals of 1 min), measured phytoplankton concentration (every 4 days) and checked the reproductive status of the molluscs (every 2 weeks). Our field study showed a significant linear correlation between the molluscs’ heart rates and the temperature of the ambient seawater. However, during specific periods of the year, we observed that phytoplankton composition or reproductive status became the dominant influence over cardiac activity. Phytoplankton concentrations were generally found to be low throughout the entire year, but two peak periods of drastically elevated phytoplankton concentration were found (April and May), and during April the peak heart rates of the blue mussels significantly increased. Spawning time took place in the middle of June, and at this time the cardiac activity of the molluscs did not change in spite of a 4°C temperature increase in the ambient seawater. Monitoring of the heart rates of the real intertidal blue mussels (animals located at the middle part of intertidal) revealed periodic fluctuations in cardiac activity that correlated strongly with tidal fluctuations. Cardiac activity in M. modiolus was significantly lower than in M. edulis from 9 May to 25 November. On the basis of our data, we concluded that the molluscs’ cardiac activity can serve not only as an indicator of the animals’ physiological conditions, but also as an indicator of changes in ambient factors.

Phytoplankton Concentration Measurements Base On Arduino Microcontroller

In this research is designing and manufacture Phytoplankton concentration measurements in liquid medium based on arduino microcontroller. The design works with by exploiting fluorescence phenomenon, by using Purple Light Emitting Diode (λ = 405 nm, P = 10 mW, frequency modulation 625 Hz) as a light source absorbed by phytoplankton, mesuring vessel, optical filters, and photodiodes. Data obtained of the photodiode sensor is then conducted data acquisition by arduino, the quantitiy of phytoplankton concentration will be displayed on the lcd. From testing to Phytopathton for the concentration range it was found that for the concentration range 102 - 106 cells / ml obtained a consistent relationship the intensity of fluorescence with the increase in cell concentration. Gradients obtained for high range concentration with R2 = 0.9632 lower than the low range concentration with R2 = 0.9642.