Statistical study of bivalve high frequency microclosing behavior: scaling properties and shot noise analysis
We consider bivalve (oyster) behavior using high frequency valvometry data. These data are obtained in the field in the Arcachon bay, with light-weight electrodes of millimeters size, attached to the molluscs, and linked by flexible wires to an electronic control unit which mea- sures valve activity. The latter are able to move freely and open their valve with an amplitude which is linked to environmental and physiological conditions, in order to filter surrounding waters. We consider here daily data recorded every 0.1 sec for 16 different animals, correspond- ing to a total of 1728000 data points. Valvometry data show important intermittent activity at high frequency, with frequent and sudden "microclosing" events (meaning partial closures), at apparently random times and with random amplitudes. The overall frequency spectrum of valve opening time series show power-law behavior with a slope $\beta = 1.6 \pm 0.1$. The random succession of closing events with random amplitudes suggests to consider a shot-noise analysis, with two independent stochastic processes representing respectively the times of these discrete shot noise events and their amplitudes. This shows that methods and approaches devoted to extreme values, chaotic dynamics, recurrence time statistics in geosciences and climate studies can also be used to study living organisms and their interactions with complex environments such as their local ecosystem.
(International journal of bifurcation and chaos in applied sciences and engineering. vol. 21, n° 0218-1274, pp. 3565-3576, 10/02/2011)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], LMBA, UBS, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean and Black Seas
(Mémoire de la Société Géologique n.s.. vol. t. 179, pp. 1-72, 01/02/2011)
UAG, INSU - CNRS, UM, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS, UEB, CEFREM, UPVD, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, iSTeP, UPMC, CNRS, BRGM, IMAGES, UPVD, LMTG, UT3, Comue de Toulouse, CNRS, GEOAZUR 6526, IRD, UPMC, UNS, INSU - CNRS, UniCA, CNRS
Detection of DNA damage in yolk-sac larvae of the Japanese Medaka, Oryzias latipes, by the comet assay
(Analytical and Bioanalytical Chemistry. vol. 399, n° 1618-2642, pp. 2235-2242, 01/02/2011)
UB, LEMA, ULH, NU, SEBIO, INERIS, URCA, ULH, NU, URCA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Water quality assessment by means of HFNI valvometry and high-frequency data modeling
The high-frequency measurements of valve activity in bivalves (e.g., valvometry) over a long period of time and in various environmental conditions allow a very accurate study of their behaviors as well as a global analysis of possible perturbations due to the environment. Valvom- etry uses the bivalve's ability to close its shell when exposed to a contaminant or other abnormal environmental conditions as an alarm to indicate possible perturbations in the environment. The modeling of such high-frequency serial valvom- etry data is statistically challenging, and here, a nonparametric approach based on kernel estima- tion is proposed. This method has the advantage of summarizing complex data into a simple den- sity profile obtained from each animal at every 24-h period to ultimately make inference about time effect and external conditions on this profile. The statistical properties of the estimator are pre- sented. Through an application to a sample of 16 oysters living in the Bay of Arcachon (France), we demonstrate that this method can be used to first estimate the normal biological rhythms of permanently immersed oysters and second to de- tect perturbations of these rhythms due to changes in their environment. We anticipate that this ap- proach could have an important contribution to the survey of aquatic systems.
(Environmental Monitoring and Assessment. vol. 182, n° 0167-6369, pp. 155-170, 13/01/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MSH, LMBA, UBS, UBO EPE, CNRS
New Arabian Sea records help decipher orbital timing of Indo-Asian monsoon
A recent study suggested that Indian monsoonal proxies commonly used in the Arabian Sea, in general productivity proxies, could be impacted by changes in the Atlantic overturning rate (AMOC) throughout a control on the nutrient delivery into the euphotic zone. This oceanic mechanism could lead to a misunderstanding between the Indian summer monsoon (SM) and orbital forcing and could confuse a direct comparison with other archives derived from other monsoonal sub-systems (such as East-Asian or African records). Here we analyze three independent proxies (bromine, foraminifera assemblages and grain size) extracted from a marine sediment core (MD04-2861) covering the last 310 ka, and retrieved in the northern Arabian Sea near the Makran margin, an area influenced by summer and winter Indian monsoon. The grain size proxy deals with the regional continental climate through fluvial and eolian processes. It cannot be linked to changes in nutrient content of AMOC and present the same phase relationship (timing) than the other SM proxies. This demonstrates that the productivity signals (Bromine) in the northern Arabian Sea are mainly controlled by SM dynamics and not AMOC modulated nutrients at orbital scale changes. We thus build a multi-proxy record of SM variability (i.e. SM stack) using statistical tools (principal component analysis) further compiled on an age model constructed independently from orbital tuning. We find that strong SM lag by 9 ± 1 ka the NH summer insolation maximum (minimum of precession, June 21 perihelion and obliquity maximum) in the precession band, and by 6 ± 1.3 ka in the Obliquity band. These results are consistent with previous studies based on marine and terrestrial records in both Indian and Asian regions, except Asian speleothems. Our study supports the hypothesis that internal climate forcing (decreased ice volume together with the increase of latent heat export from the southern Indian Ocean) set the timing of strong Indo-Asian summer monsoons within both the precession and obliquity cycle. The external forcing (direct sensible heating) initiate monsoonal circulation. Strong Indian winter monsoon (WM) occurs between ice maxima and northern hemisphere sensible heat minima, indicating that both act to strengthen WM circulation. The summer and winter monsoons are in antiphase in the precession band suggesting that the two systems are dynamically linked.
(Earth and Planetary Science Letters. vol. 308, n° 0012-821X, pp. 433-444, 01/01/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
On a Teratological Specimen of Athanas nitescens (Decapoda, Caridea, Alpheidae)
(Crustaceana. vol. 84, n° 0011-216X, pp. 1649-1652, 01/01/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Biodiversity change after climate-induced ice-shelf collapse in the Antarctic.
The marine ecosystem on the eastern shelf of the Antarctic Peninsula was surveyed 5 and 12 years after the climate-induced collapse of the Larsen A and B ice shelves. An impoverished benthic fauna was discovered, that included deep-sea species presumed to be remnants from ice-covered conditions. The current structure of various ecosystem components appears to result from extremely different response rates to the change from an oligotrophic sub-ice-shelf ecosystem to a productive shelf ecosystem. Meiobenthic communities remained impoverished only inside the embayments. On local scales, macro- and mega-epibenthic diversity was generally low, with pioneer species and typical Antarctic megabenthic shelf species interspersed. Antarctic Minke whales and seals utilised the Larsen A/B area to feed on presumably newly established krill and pelagic fish biomass. Ecosystem impacts also extended well beyond the zone of ice-shelf collapse, with areas of high benthic disturbance resulting from scour by icebergs discharged from the Larsen embayments.
(Deep Sea Research Part II: Topical Studies in Oceanography. vol. 58, n° 0967-0645, pp. 74-83, 01/01/2011)
AWI, QUB, IRSNB / RBINS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ICM, CSIC, LG / WGL, CAU, BAS, NERC, UGent, DZMB, UB, CNRS, UHM
Évolution du trait de côte à l’Holocène supérieur dans la Sebkha El-Guettiate de Skhira (Golfe de Gabès, Tunisie) à travers sa faune d’ostracodes et de foraminifères
(Geobios. vol. 44, n° 0016-6995, pp. 101-115, 01/01/2011)
FSS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion, NW Mediterranean): Environmental controls on a river-dominated shelf
(Journal of Sea Research (JSR). vol. 65, n° 1385-1101, pp. 58-75, 01/01/2011)
BIAF, UA, UA, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CEFREM, UPVD, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OCEANIS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Rotating disk electrodes to assess river biofilm thickness and elasticity
The present study examined the relevance of an electrochemical method based on a rotating disk electrode (RDE) to assess river biofilm thickness and elasticity. An in situ colonisation experiment in the River Garonne (France) in August 2009 sought to obtain natural river biofilms exhibiting differentiated architecture. A constricted pipe providing two contrasted flow conditions (about 0.1 and 0.45 m s−1 in inflow and constricted sections respectively) and containing 24 RDE was immersed in the river for 21 days. Biofilm thickness and elasticity were quantified using an electrochemical assay on 7 and 21 days old RDE-grown biofilms (t7 and t21, respectively). Biofilm thickness was affected by colonisation length and flow conditions and ranged from 36 ± 15 μm (mean ± standard deviation, n = 6) in the fast flow section at t7 to 340 ± 140 μm (n = 3) in the slow flow section at t21. Comparing the electrochemical signal to stereomicroscopic estimates of biofilms thickness indicated that the method consistently allowed (i) to detect early biofilm colonisation in the river and (ii) to measure biofilm thickness of up to a few hundred μm. Biofilm elasticity, i.e. biofilm squeeze by hydrodynamic constraint, was significantly higher in the slow (1300 ± 480 μm rpm1/2, n = 8) than in the fast flow sections (790 ± 350 μm rpm1/2, n = 11). Diatom and bacterial density, and biofilm-covered RDE surface analyses (i) confirmed that microbial accrual resulted in biofilm formation on the RDE surface, and (ii) indicated that thickness and elasticity represent useful integrative parameters of biofilm architecture that could be measured on natural river assemblages using the proposed electrochemical method.
(Water Research. vol. 45, n° 0043-1354, pp. 1347-1357, 01/01/2011)
LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, LISE, UPMC, INC-CNRS, CNRS, IMFT, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS