Problematic of the Pelagia noctiluca outbreaks in the Bay of Calvi (Corsica)

peer reviewedThe interannual variations of the Schyphozoan jellyfish Pelagia noctiluca is estimated by weekly measurements in the Bay of Calvi (Corsica) from 2003. The mean annual abundance reaches a dramatic maximum in 2006. The medusae appear by migration of active swarms on the shelf and at the external limit of the Bay. Degraded individuals drift as passive swarms, throughout inner side of the Bay and embayments

La fumure azotée

Bilan de l'année écoulée et recommandations pratique

Plankton ecosystem response to the decadal variation of winter intensity in the Mediterranean Sea : a long-term study (1979-2014)

In the Mediterranean Sea, several studies with distinct data sets indicate that the pelagic ecosystem underwent periods of change in the late 1980s and in the early 2000s. Here we used a unique long-term time series of data collected in the well-preserved Bay of Calvi (Corsica island, Ligurian Sea, NW Mediterranean) from 1979 and 2014 to explore the synchrony between changes in environmental conditions and phyto- and zooplankton dynamics. We identified an almost decadal, long-term variability in winter intensity, with three distinct periods: the 1980s (1979-1988), the 1990s (1989-1998) and the 2000s (1999-2014), which were characterized by moderate, mild and highly variable winters, respectively. We pointed out how the decadal changes in winter intensity affected (i) the duration and intensity of phyto- and zooplankton blooms, (ii) the mean yearly biomasses, and (iii) the nature of the assemblages. High phyto- and zooplankton biomasses were observed in years characterized by moderate and severe winters, and low phyto- and zooplankton abundances were recorded in years with mild winters. Moderate/severe and mild winters were favorable for diatoms and gelatinous zooplankton, respectively. Focusing on meroplanktonic species, we explored ecological consequences of decadal variations observed in the Bay of Calvi for resource management. We highlighted parallelisms with other European seas

Automatic activies of the spinal cord concerned with the respiratory movements

1. After spinal transection at the medulla-spinal junction the thoracic respiratory movements no longer appear in the adult animals, nevertheless the sporadic spike discharges can be recorded from the intercostal muscles. 2. Both in the acute and chronic experiments the spinal cord is transected at the two levels of Th7 and Thl1 respectively and all the dorsal rootlets coming into that part of the cord lying between the transections are severed. The sporadic spike discharges with irregular intervals varying about 0.5 to 3.0 sec. can be recorded from intercostal muscles in the 8th to 10th segments of the spinal cord isolated. There can never be found any reflex influence of the skin stimulation upon the discharges, which also disappear provided the intercostal nerves innervating the muscles are severed. 3. From these results it may be concluded that the spinal cord is endowed with an ability to initiate the impulses autochthonously to excite the intercostal muscles, even though it is only poorly developed in the adult animals.</p

AquaCrop and the Belgian collaborative agriculture monitoring (BELCAM) platform

peer reviewe

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea

Neustonic microplastic and zooplankton abundance was determined in the North Western Mediterranean Sea during a summer cruise between July 9th and August 6th 2010, with a break between July 22th and 25th due to a strong wind event. Ninety percent of the 40 stations contained microplastic particles (size 0.3-5 mm) of various compositions: e.g., filaments, polystyrene, thin plastic films. An average concentration of 0.116 particles/m² was observed. The highest abundances (> 0.36 particles/m²) were observed in the shelf stations. The neustonic plastic particles concentrations were 5 times higher before than after the strong wind event which increased the mixing and the vertical repartition of plastic particles in the upper layers of the water column. The values rise in the same order of magnitude than in the North Pacific Gyre. The average ratio between microplastics and mesozooplankton weights was 0.5 for the whole survey and might induce a potential confusion for zooplankton feeders.Peer reviewe

Crop Phenology Modelling Using Proximal and Satellite Sensor Data

peer reviewedUnderstanding crop phenology is crucial for predicting crop yields and identifying potential risks to food security. The objective was to investigate the effectiveness of satellite sensor data, compared to field observations and proximal sensing, in detecting crop phenological stages. Time series data from 122 winter wheat, 99 silage maize, and 77 late potato fields were analyzed during 2015–2017. The spectral signals derived from Digital Hemispherical Photographs (DHP), Disaster Monitoring Constellation (DMC), and Sentinel-2 (S2) were crop-specific and sensor-independent. Models fitted to sensor-derived fAPAR (fraction of absorbed photosynthetically active radiation) demonstrated a higher goodness of fit as compared to fCover (fraction of vegetation cover), with the best model fits obtained for maize, followed by wheat and potato. S2-derived fAPAR showed decreasing variability as the growing season progressed. The use of a double sigmoid model fit allowed defining inflection points corresponding to stem elongation (upward sigmoid) and senescence (downward sigmoid), while the upward endpoint corresponded to canopy closure and the maximum values to flowering and fruit development. Furthermore, increasing the frequency of sensor revisits is beneficial for detecting short-duration crop phenological stages. The results have implications for data assimilation to improve crop yield forecasting and agri-environmental modeling

Sol, phytotechnie et climat : leur influence sur Polymyxa betae Keskin

Doctorat en Sciences agronomiques -- UCL, 199

Impact des mouillages forains sur la qualité de l’eau et du phytoplancton : résultats d’une étude préliminaire menée en Baie de Calvi (Corse)

Le plus souvent, l’étude de l’impact des mouillages forains sur l’environnement aquatique concerne l’analyse des dégradations subies par la faune et la flore benthiques. Cependant, dans nos régions, la grande majorité des bateaux de plaisance construits avant 2008 et de longueur inférieure à 24 mètres ne sont pas équipés d'installations de stockage des eaux résiduaires (eaux ménagères, douches, eaux noires des toilettes) et encore moins de traitement à bord des effluents. Une partie des eaux usées de la plaisance est donc rejetée en mer sans que leur charge polluante et leur impact sur les eaux de surface ne soient connus. De mai à septembre 2011, une étude pilote a été menée dans une zone de mouillage forain de taille moyenne de la Baie de Calvi (site de l’Alga) dans le double but d’analyser la qualité du phytoplancton (biomasse et composition) et la charge en Escherichia coli des eaux de surface. Les données obtenues à l’Alga sont comparées à celles du point de référence DCE pour l’étude du phytoplancton, situé à proximité de STARESO. Les résultats obtenus à l’Alga mettent en évidence les éléments suivants : 1. Biomasse phytoplanctonique totale : la biomasse phytoplanctonique totale de l’Alga est proche de celle mesurée à la station de référence; 2. Composition phytoplanctonique : alors que la composition du phytoplancton du site de référence est constante au cours de la saison estivale, le phytoplancton de l’Alga se caractérise par une augmentation progressive de la concentration en Cyanobactéries, un groupe dont la croissance est favorisée par la présence d’ammonium; 3. Charge en E. coli : des concentrations de 100 à 300 E. coli par 100 ml d’eau sont mesurées de juillet à septembre dans tous les échantillons de surface de la zone de mouillage alors qu’elles sont toujours absentes de la station de référence. Les apports diffus liés aux rejets des eaux usées de la plaisance paraissent donc suffisants pour affecter la composition du phytoplancton et la charge bactérienne des eaux de surface d’une zone de mouillage forain de taille moyenne. Les implications en termes d’impact sur la qualité de l’eau et de l’écosystème seront discutées. Depuis mars 2012, un suivi complet de l’influence de la zone de mouillage forain de l’Alga sur l’écosystème côtier est réalisé dans le cadre du projet STARECAPMED

Field-scale assessment of Belgian winter cover crops biomass based on Sentinel-2 data

Winter cover crops, used as green manure, can supply up to 45 units of nitrogen per hectare to the following summer crops. In order to contribute to the establishment of the nitrogen balance sheet for fertilisation recommendation of subsequent main crop at field scale, this supply is currently derived from the biomass production, classically estimated visually using 3 classes: 0–1, 1–3, 3+ tons of dry matter per hectare (Mg DM ha 1). The capabilities of Sentinel-2 satellite data to retrieve an operator-independent winter cover crop biomass have been assessed. Biomass samples were collected in 1 m quadrats for various types of winter cover fields classically used in Belgium (mustard, phacelia, oat and a range of mixed cover), in 2016 and 2017 (yield between 0.1 to 5 tons of dry matter per hectare). Empirical relationships between the winter cover crop biomass and a wide range of vegetation indices (VIs) derived from Sentinel-2 have been defined, and the most performant VI identified. For pure stands of winter cover crops, the cross-validation RMSE (CVRMSE) of the best model is 0.36 Mg DM ha 1 for mustard and 0.3 Mg DM ha 1 for phacelia. The CVRMSE observed for mixed stands, around 0.61 Mg DM ha 1, is roughly two times higher than the CVRMSE observed for pure stands. The added-value of objective satellitebased estimation of winter cover biomass was also assessed by comparing respective estimations with regards to an independent reference dataset made of sample measurements on the ground. Models based on Earth observation showed better results than farmer visual assessment for mustard crops, and were as good as farmers for phacelia crops