scholarly journals Possible mixotrophy of pigmented nanoflagellates: Microbial plankton biomass, primary production and phytoplankton growth in the NW Iberian upwelling in spring

2011 ◽  
Vol 94 (2) ◽  
pp. 172-181 ◽  
Author(s):  
B.G. Crespo ◽  
O. Espinoza-González ◽  
I.G. Teixeira ◽  
C.G. Castro ◽  
F.G. Figueiras
Keyword(s):  
Primary Production ◽  
Phytoplankton Growth ◽  
Plankton Biomass ◽  
Pigmented Nanoflagellates ◽  
Microbial Plankton

scholarly journals Response of heterotrophic and autotrophic microbial plankton to inorganic and organic inputs along a latitudinal transect in the Atlantic Ocean

2010 ◽  
Vol 7 (5) ◽  
pp. 1701-1713 ◽  
Author(s):  
S. Martínez-García ◽  
E. Fernández ◽  
A. Calvo-Díaz ◽  
E. Marañón ◽  
X. A. G. Morán ◽  
...  
Keyword(s):  
Organic Matter ◽  
Atlantic Ocean ◽  
Bacterial Growth ◽  
Heterotrophic Bacteria ◽  
Growth Efficiency ◽  
Bacterial Growth Efficiency ◽  
Organic Nutrient ◽  
Plankton Biomass ◽  
Latitudinal Transect ◽  
Microbial Plankton

Abstract. The effects of inorganic and/or organic nutrient inputs on phytoplankton and heterotrophic bacteria have never been concurrently assessed in open ocean oligotrophic communities over a wide spatial gradient. We studied the effects of potentially limiting inorganic (nitrate, ammonium, phosphate, silica) and organic nutrient (glucose, aminoacids) inputs added separately as well as jointly, on microbial plankton biomass, community structure and metabolism in five microcosm experiments conducted along a latitudinal transect in the Atlantic Ocean (from 26° N to 29° S). Primary production rates increased up to 1.8-fold. Bacterial respiration and microbial community respiration increased up to 14.3 and 12.7-fold respectively. Bacterial production and bacterial growth efficiency increased up to 58.8-fold and 2.5-fold respectively. The largest increases were measured after mixed inorganic-organic nutrients additions. Changes in microbial plankton biomass were small as compared with those in metabolic rates. A north to south increase in the response of heterotrophic bacteria was observed, which could be related to a latitudinal gradient in phosphorus availability. Our results suggest that organic matter inputs will result in a predominantly heterotrophic versus autotrophic response and in increases in bacterial growth efficiency, particularly in the southern hemisphere. Subtle differences in the initial environmental and biological conditions are likely to result in differential microbial responses to inorganic and organic matter inputs.

scholarly journals Drivers and uncertainties of future global marine primary production in marine ecosystem models

2015 ◽  
Vol 12 (23) ◽  
pp. 6955-6984 ◽  
Author(s):  
C. Laufkötter ◽  
M. Vogt ◽  
N. Gruber ◽  
M. Aita-Noguchi ◽  
O. Aumont ◽  
...  
Keyword(s):  
Primary Production ◽  
Nutrient Limitation ◽  
21St Century ◽  
Net Primary Production ◽  
Marine Ecosystem ◽  
Phytoplankton Growth ◽  
Strong Increase ◽  
Ecosystem Models ◽  
Low Latitudes ◽  
Marine Ecosystem Models

Abstract. Past model studies have projected a global decrease in marine net primary production (NPP) over the 21st century, but these studies focused on the multi-model mean rather than on the large inter-model differences. Here, we analyze model-simulated changes in NPP for the 21st century under IPCC's high-emission scenario RCP8.5. We use a suite of nine coupled carbon–climate Earth system models with embedded marine ecosystem models and focus on the spread between the different models and the underlying reasons. Globally, NPP decreases in five out of the nine models over the course of the 21st century, while three show no significant trend and one even simulates an increase. The largest model spread occurs in the low latitudes (between 30° S and 30° N), with individual models simulating relative changes between −25 and +40 %. Of the seven models diagnosing a net decrease in NPP in the low latitudes, only three simulate this to be a consequence of the classical interpretation, i.e., a stronger nutrient limitation due to increased stratification leading to reduced phytoplankton growth. In the other four, warming-induced increases in phytoplankton growth outbalance the stronger nutrient limitation. However, temperature-driven increases in grazing and other loss processes cause a net decrease in phytoplankton biomass and reduce NPP despite higher growth rates. One model projects a strong increase in NPP in the low latitudes, caused by an intensification of the microbial loop, while NPP in the remaining model changes by less than 0.5 %. While models consistently project increases NPP in the Southern Ocean, the regional inter-model range is also very substantial. In most models, this increase in NPP is driven by temperature, but it is also modulated by changes in light, macronutrients and iron as well as grazing. Overall, current projections of future changes in global marine NPP are subject to large uncertainties and necessitate a dedicated and sustained effort to improve the models and the concepts and data that guide their development.

Modelling sub-daily phytoplankton dynamics and analysing primary production controls in the lower Thames catchment, UK

2020 ◽  
Author(s):  
Devanshi Pathak ◽  
Michael Hutchins ◽  
François Edwards
Keyword(s):  
Water Quality ◽  
Primary Production ◽  
Water Temperature ◽  
High Frequency ◽  
Phytoplankton Growth ◽  
Quality Data ◽  
Phytoplankton Dynamics ◽  
Water Quality Data ◽  
River Thames ◽  
The Impact

<p>River phytoplankton provide food for primary consumers, and are a major source of oxygen in many rivers. However, high phytoplankton concentrations can hamper river water quality and ecosystem functioning, making it crucial to predict and prevent harmful phytoplankton growth in rivers. In this study, we modify an existing mechanistic water quality model to simulate sub-daily changes in water quality, and present its application in the River Thames catchment. So far, the modelling studies in the River Thames have focused on daily to weekly time-steps, and have shown limited predictive ability in modelling phytoplankton concentrations. With the availability of high-frequency water quality data, modelling tools can be improved to better understand process interactions for phytoplankton growth in dynamic rivers. The modified model in this study uses high-frequency water quality data along a 62 km stretch in the lower Thames to simulate river flows, water temperature, nutrients, and phytoplankton concentrations at sub-daily time-steps for 2013-14. Model performance is judged by percentage error in mean and Nash-Sutcliffe Efficiency (NSE) statistics. The model satisfactorily simulates the observed diurnal variability and transport of phytoplankton concentrations within the river stretch, with NSE values greater than 0.7 at all calibration sites. Phytoplankton blooms develop within an optimum range of flows (16-81 m<sup>3</sup>/s) and temperature (11-18° C), and are largely influenced by phytoplankton growth and death rate parameters. We find that phytoplankton growth in the lower Thames is mainly limited by physical controls such as residence time, light, and water temperature, and show some nutrient limitation arising from phosphorus depletion in summer. The model is tested under different future scenarios to evaluate the impact of changes in climate and management conditions on primary production and its controls. Our findings provide support for the argument that the sub-daily modelling of phytoplankton is a step forward in better prediction and management of phytoplankton dynamics in river systems.</p>

scholarly journals A coupled physical-biological model of the Northern Gulf of Mexico shelf: model description, validation and analysis of phytoplankton variability

2011 ◽  
Vol 8 (7) ◽  
pp. 1881-1899 ◽  
Author(s):  
K. Fennel ◽  
R. Hetland ◽  
Y. Feng ◽  
S. DiMarco
Keyword(s):  
Organic Matter ◽  
Gulf Of Mexico ◽  
Primary Production ◽  
River System ◽  
Phytoplankton Growth ◽  
Biological Model ◽  
Model Description ◽  
Ecological Gradient ◽  
Northern Gulf Of Mexico ◽  
Plume Region

Abstract. The Texas-Louisiana shelf in the Northern Gulf of Mexico receives large inputs of nutrients and freshwater from the Mississippi/Atchafalaya River system. The nutrients stimulate high rates of primary production in the river plume, which contributes to the development of a large and recurring hypoxic area in summer, but the mechanistic links between hypoxia and river discharge of freshwater and nutrients are complex as the accumulation and vertical export of organic matter, the establishment and maintenance of vertical stratification, and the microbial degradation of organic matter are controlled by a non-linear interplay of factors. Unraveling these interactions will have to rely on a combination of observations and models. Here we present results from a realistic, 3-dimensional, physical-biological model with focus on a quantification of nutrient-stimulated phytoplankton growth, its variability and the fate of this organic matter. We demonstrate that the model realistically reproduces many features of observed nitrate and phytoplankton dynamics including observed property distributions and rates. We then contrast the environmental factors and phytoplankton source and sink terms characteristic of three model subregions that represent an ecological gradient from eutrophic to oligotrophic conditions. We analyze specifically the reasons behind the counterintuitive observation that primary production in the light-limited plume region near the Mississippi River delta is positively correlated with river nutrient input, and find that, while primary production and phytoplankton biomass are positively correlated with nutrient load, phytoplankton growth rate is not. This suggests that accumulation of biomass in this region is not primarily controlled bottom up by nutrient-stimulation, but top down by systematic differences in the loss processes.

An early spring bloom of large diatoms in the ice-covered Saroma-ko Lagoon, Hokkaido, Japan

2011 ◽  
Vol 92 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Akihiro Shiomoto ◽  
Koji Asakuma ◽  
Han-Dong Hoon ◽  
Koichi Sakaguchi ◽  
Kimihiko Maekawa
Keyword(s):  
Growth Rate ◽  
Global Warming ◽  
Primary Production ◽  
Spring Bloom ◽  
Early Spring ◽  
Phytoplankton Growth ◽  
Bloom Period ◽  
Ice Coverage ◽  
Phytoplankton Growth Rate ◽  
Free Area

Saroma-ko Lagoon, the largest body of water that has complete ice coverage during winter in Japan, was not completely covered by ice in the winter of 2009. This condition is considered to be a result of the progression of global warming. A bloom of large diatoms was observed in the ice-free area between February and April. This early spring bloom seemed to have started in the latter part of January, and lasted for about three months. The maximum chlorophyll-a (Chl a) concentration of about 10 mg m−3 was observed in March, and was similar to the level of 5–20 mg m−3 previously reported for the ordinary spring bloom in Saroma-ko Lagoon. The maximum primary production of 786 mgC m−2 day−1 and the maximum Chl a-specific primary production, an index of the phytoplankton growth rate, were also found in March. Species changes from Thalassiosira spp. to Chaetoceros spp. were observed during the bloom. This early spring bloom could extend into the ordinary spring bloom period. Its duration was obviously longer than that of the spring bloom, which is typically about one month. These results show the phytoplankton condition that could be expected during winter and spring as global warming progresses.

Photosynthesis, primary production and phytoplankton growth rates in Gerlache and Bransfield Straits during Austral summer: cruise FRUELA 95

2002 ◽  
Vol 49 (4-5) ◽  
pp. 707-721 ◽  
Author(s):  
Luisa M Lorenzo ◽  
Belén Arbones ◽  
Francisco G Figueiras ◽  
Gavin H Tilstone ◽  
Félix L Figueroa
Keyword(s):  
Primary Production ◽  
Growth Rates ◽  
Austral Summer ◽  
Phytoplankton Growth
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