97 research outputs found
Diminution des ressources planctoniques et artificialisation de l'habitat : Quelles conséquences sur le fonctionnement des communautés aquatiques ?:Un aperçu via l’étude des niches écologiques des communautés de macroinvertébrés et de poissons de la Meuse belge et française
Phytoplankton pigment analysis as a tool for monitoring a tropical great lake, Lake Kivu (East Africa)
Lake Kivu, East Africa, is a deep oligotrophic and meromictic lake containing high amounts of
dissolved methane (∼55–60 km3) and carbon dioxide (∼300 km3) in its deep waters. Methane
harvesting for energy production began in 2015, and a monitoring programme was set up to
assess possible disturbance on the ecosystem. Phytoplankton biomass and composition was
assessed twice per month or monthly at 2 monitoring sites between June 2005 and December
2019, based on HPLC analysis of chlorophyll a (Chl-a) and marker pigments. This long-term
series shows that significant changes occurred around 2010 in the lake phytoplankton, with a
notable increase of Chl-a and changes in the assemblage toward an increase in non-motile
green algae and diatoms. To assess possible changes due to methane harvesting, we compared
2 periods, 2012–2014 and 2018–2019. Chl-a concentration decreased slightly in 2018–2019
compared to the reference period of 2012–2014, and significant changes occurred in
composition of the phytoplankton assemblage. In terms of relative contribution to Chl-a,
diatoms increased from 26% to 46%, whereas green algae decreased ∼2-fold, from 35% in
2012–2014 to 18% in 2018–2019. Multivariate analyses showed that phytoplankton composition
was influenced by seasonal and interannual variations of limnological variables related to
changes in meteorological factors. To assess possible future changes due to methane
exploitation, we recommend increasing sampling frequency and taxonomic resolution, as well
as improving environmental data acquisition
Long‐term change of phytoplankton in Lake Kivu: The rise of the greens
Phytoplankton time‐series enable the observation of recurrent seasonal patterns
on community composition, but drastic shifts in community structure are rarely
observed, unless linked to anthropogenic impacts (e.g. changes in nutrient inputs).
Here, we report a unique case of non‐seasonal, multiannual regime shift of phytoplankton
community structure in Lake Kivu, East Africa, and explore the possible causes for such changes.
2. We recorded phytoplankton biomass every 2 weeks over a period of 12 years (from 2002 to 2015). Phytoplankton community previously dominated by cyanobacteria and diatoms changed considerably from 2012, with a conspicuous rise in the biomass of green algae (from 3 to 33% lake‐wide), and a decline of cryptophytes and cyanobacteria along with an increase in total chlorophyll a concentration. Concomitantly, we observed significant differences in the mixed layer depth between the two periods, resulting from changes in the thermal gradient. The euphotic zone depth was also reduced in 2012–2015, probably from the higher
phytoplankton biomass. Moreover, mean particulate nitrogen and phosphorus increased
as well as the particulate N:P ratio.
3. Desmids (Cosmarium laeve) now dominate the mixolimnion, probably due to atelomixis,
observed in high‐frequency temperature measurements. We believe that decadal or multidecadal variability of climate on the Indian Ocean may be the reason for this regime shift in thermal stratification, with a strong impact in phytoplankton community structure.
4. In conclusion, our study demonstrates that tropical lakes may be subject to nonseasonal
fluctuations that generate multiannual regime shifts. These regime shifts have probably never been reported previously because of the lack of long phytoplankton time‐series in low latitudes.Peer reviewe
Synthesis and asymmetric hydrogenation of (3E)-1-benzyl-3-[(2-oxopyridin-1(2H)-yl)methylidene]piperidine-2,6-dione
The synthesis of (3E)-1-benzyl-3-[(2-oxopyridin-1(2H)-yl)methylidene]piperidine-2,6-dione 4 from N-benzylglutarimide was achieved in three steps. The asymmetric hydrogenation of 4 gave either the product of partial reduction (10) or full reduction (13), depending on the catalyst which was employed, in high ee in each case. Attempts at asymmetric transfer hydrogenation (ATH) of 4 resulted in formation of a racemic product
Corrigendum: Potent and selective inhibitors of 11β-hydroxysteroid dehydrogenase type 1 labeled with carbon-13 and carbon-14
Fish data of the French River Meuse from 1985 to 2010 at Han sur Meuse (S1), Sassey sur Meuse (S2) and Ham sur Meuse (S3)
French data used in the article "Long-term trends in trait structure of
riverine communities facing predation risk increase and trophic resource
decline" published by Latli A. and al., 2017 in Ecological
Applications.<br><br>Fish data of the French River Meuse from 1985 to 2010 at Han sur Meuse (S1), Sassey sur Meuse (S2) and Ham sur Meuse (S3)<br><br>Data were produced by the ONEMA Agency and require their authorization for use
Macro-invertebrate data of the French River Meuse from 1998 to 2011 at Sassey sur Meuse
French data used in the article "Long-term trends in trait structure of
riverine communities facing predation risk increase and trophic resource
decline" published by Latli A. and al., 2017 in Ecological
Applications.<br><br>Macroinvertebrate data of the French River Meuse from 1998 to 2011 at Sassey sur Meuse.<br><br>Data were produced by the French Water Agency Rhin Meuse and require their authorization for use.<br
Synthesis of highly potent lymphocyte function-associated antigen-1 antagonists labeled with carbon-14 and with stable isotopes, part 3
Radiosynthesis of tritium-labeled novel nitromethylene neonicotinoids compounds with NaB3H4
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