Structure of phytoplankton (Continuous Plankton Recorder and SeaWiFS) and impact of climate in the Northwest Atlantic Shelves

International audienceAll marine organisms are affected to some extent by the movement and thermal properties of oceanic currents. However phytoplankton, because of its small size is most directly coupled to the physical environment. The intense hydrodynamic activity observed in the Northwest Atlantic Shelves Province makes this region especially intriguing from the point of view of physical-biological interactions. In the present work, remote sensed data of Sea Surface Height (SSH) anomalies, Sea-surface chlorophyll a concentrations (SeaWiFS), and Sea Surface Temperature (SST) are used to complement the Continuous Plankton Recorder (CPR) survey that continuously sampled a route between Norfolk (Virginia, USA; 39° N, 71° W) and Argentia (Newfoundland; 47° N, 54° W) over the period 1995?1998. Over this period, we examined physical structures (i.e. SST and SSH) and climatic forcing associated with space-time phytoplankton structure. Along this route, the phytoplankton structures were mainly impacted by the changes in surface flow along the Scotian Shelf rather than significantly influenced by the mesoscale features of the Gulf Stream. These changes in water mass circulation caused a drop in temperature and salinity along the Scotian Shelf that induced changes in phytoplankton and zooplankton abundance

The impact of turbulence and phytoplankton dynamics on foam formation, seawater viscosity and chlorophyll concentration in the eastern English Channel

The space-time dynamics of chlorophyll a concentration and seawater excess viscosity has been investigated in the hydrographically contrasting inshore and offshore water masses of the eastern English Channel. This was done during the phytoplankton spring bloom dominated by Phaeocystis globosa before and after the very large-scale formation of foam induced by an increase in wind-driven turbulence and the related wave breakings. The results suggest that the dynamics of chlorophyll a concentration and seawater excess viscosity are differentially controlled by the formation of foam through the intensity of the spring bloom and wind-generated turbulence

Anthropogenic shift of planktonic food web structure in a coastal lagoon by freshwater flow regulation

This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/Anthropogenic modification of aquatic systems has diverse impacts on food web interactions and ecosystem states. To reverse the adverse effects of modified freshwater flow, adequate management of discharge is required, especially due to higher water requirements and abstractions for human use. Here, we look at the effects of anthropogenically controlled freshwater flow regimes on the planktonic food web of a Ramsar listed coastal lagoon that is under recovery from degradation. Our results show shifts in water quality and plankton community interactions associated to changes in water flow. These shifts in food web interactions represent modifications in habitat complexity and water quality. At high flow, phytoplankton-zooplankton interactions dominate the food web. Conversely, at low flow, bacteria, viruses and nano/picoplankton interactions are more dominant, with a substantial switch of the food web towards heterotrophy. This switch can be associated with excess organic matter loading, decomposition of dead organisms, and synergistic and antagonistic interactions. We suggest that a lower variability in flow amplitude could be beneficial for the long-term sustaining of water quality and food web interactions, while improving the ecosystem health of systems facing similar stresses as the Coorong

Decadal fluctuations in North Atlantic water inflow in the North Sea between 1958-2003: impacts on temperature and phytoplankton populations

The circulation of Atlantic water along the European continental slope, in particular the inflow into the North Sea, influences North Sea water characteristics with consequent changes in the environment affecting plankton community dynamics. The long-term effect of fluctuating oceanographic conditions on the North Sea pelagic ecosystem is assessed. It is shown that (i) there are similar regime shifts in the inflow through the northern North Sea and in Sea Surface Temperature, (ii) long-term phytoplankton trends are influenced by the inflow only in some North Sea regions, and (iii) the spatial variability in chemicophysical and biological parameters highlight the influence of smaller scale processes

Bacterial production of transparent exopolymer particles during static and laboratory-based cross-flow experiments

Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Biofouling of seawater reverse osmosis (SWRO) membranes represents one of the leading causes of performance deterioration in the desalination industry. This work investigates the biofouling potential of microbial communities present in a reverse osmosis (RO) feed tank. As an example, water from the RO feed tank of the Penneshaw desalination plant (Kangaroo Island, South Australia) was used in a static biofilm formation experiment. Cultures of the indigenous biofilms formed during the static experiment showed that α-Proteobacteria and γ-Proteobacteria accounted for nearly 80% of the classes of bacteria present in the RO feed tank. Pseudomonas sp. was identified as the major species and isolated for testing in static and laboratory-based cross flow biofilm formation experiments. Results showed that the volume of TEPs generated by Pseudomonas sp. during the laboratory-based cross-flow experiment was 10 fold higher to that produced during the static experiment for the same time period, while both experiments were inoculated with cell concentrations of the same order of magnitude. The availability of nutrients was also shown to be a key driver in TEP production, particularly for the static experiments. This study provides insights into the phenomenon of biofouling by assessing the production of biofouling precursors from one of the main genera of biofilm-forming bacteria, namely Pseudomonas sp

Turbo thin film continuous flow production of biodiesel from fungal biomass

This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ which permits use, distribution and reproduction in any medium, provided the original work is properly cited. This author accepted manuscript is made available following 24 month embargo from date of publication (November 2018) in accordance with the publisher’s archiving policyDirect biodiesel production from wet fungal biomass may significantly reduce production costs, but there is a lack of fast and cost-effective processing technology. A novel thin film continuous flow process has been applied to study the effects of its operational parameters on fatty acid (FA) extraction and FA to fatty acid methyl ester (FAME) conversion efficiencies. Single factor experiments evaluated the effects of catalyst concentration and water content of biomass, while factorial experimental designs determined the interactions between catalyst concentration and biomass to methanol ratio, flow rate, and rotational speed. Direct transesterification (DT) of wet Mucor plumbeus biomass at ambient temperature and pressure achieved a FA to FAME conversion efficiency of >90% using 3 wt/v % NaOH concentration, if the water content was ≤50% (w/w). In comparison to existing DT methods, this continuous flow processing technology has an estimated 90–94% reduction in energy consumption, showing promise for up-scaling.Eko K. Sitepu gratefully acknowledges funding through the Australian Award Scholarship. The authors acknowledge funding of the project through the Australian Research Council and the Government of South Australia

Microscale patchiness in microphytobenthos distributions: evidence for a critical state

Netherland

Differential contribution of diatoms and dinoflagellates to phytoplankton biomass in the NE Atlantic Ocean and the North Sea

Sampling by the continuous plankton recorder (CPR) survey over the North Atlantic Ocean and the North Sea has enabled long-term studies of phytoplankton biomass. Analysis of an index of phytoplankton biomass, the phytoplankton colour index (PCI), has previously shown an increase in phytoplankton biomass in the NE Atlantic. In the current study, further investigations were conducted to determine the contribution of diatom and dinoflagellate cell counts to the PCI, their fluctuations over the last 45 yr and their geographical variations in the eastern North Atlantic and the North Sea. An increased contribution of dinoflagellates to the PCI was revealed over the south NE Atlantic and the northern North Sea. In contrast, the contribution of diatoms decreased in the north NE Atlantic and the northern North Sea. No discernible trends were found in the other regions of the North Sea. The relative contributions of diatoms and dinoflagellates to the PCI led to the identification of 3 geographically distinct dynamic regimes in the diatom/dinoflagellate dynamics in the NE Atlantic and the North Sea. Finally, it is stressed that the discrepancy observed in the patterns of PCI and diatom and dinoflagellate cell counts suggests that changes in PCI do not reflect changes in the community structure and that the exclusive use of PCI is not adequate to investigate the long-term trends in the trophic link between phytoplankton and herbivorous zooplankton