Ben Hamadou R

Ben Hamadou R., Ibanez F., Picheral M., G. Gorsky. 2005. Identification of step pattern in ordered data stes using the Walsh transform algorithm. Ecological Modelling 182: 11-24

ABSTRACT : Thiswork is an attempt to recognize discontinuities within ordered data series by the use of theWalsh functions.Walsh functions are a system of orthogonal functions used in showing howthe energy in a given signal is distributed among these rectangulaire components revealing the existent boundaries. This paper presents the capacity ofWalsh transform on determining the statistical significance of discontinuities within ordered marine ecological data. Marine ecosystems present high vertical patterns; dataseries on particulate matter concentrations (measured by the Underwater Video Profiler (UVP)) were used to recognize homogeneity limits in water columns. Firstly, Walsh functions are generated in a compact form. Then, a spectral decomposition is performed on the ecological signal to obtain a stepped Walsh version; the step width at this stage is unvarying, picking constant vertical sections. To avoid this limitation, the estimated series is then smoothed to recognize changing step widths by merging successive blocks presenting statistical non-significant difference; here the nonparametric Kolmogorov–Smirnov test is used. This Walsh transform algorithm provides a fast, simple yet accurate means of separating ordered ecological data into groups of observations corresponding to different marine water masses. This method is applied to four profiles measured at the same site during 2 days. The temporal evolution of depth transitions are first discussed and then used for the validation of the transform model.

KEY WORDS: Ordered data discontinuities; Boundary detection;Walsh function; Spectral decomposition; UnderwaterVideo Profiler;Water masses;Nonparametric; Classification; POMME cruise

Beaugrand G. & F. Ibanez. 2004. Monitoring marine plankton ecosystems (2): long-term changes in North Sea calanoid copepods in relation to hydro-climatic variability. Mar. Ecol., Prog., Series, 284: 35-47

ABSTRACT : Recently, a framework has been proposed to monitor plankton ecosystems in the North Atlantic and adjacent seas using calanoid copepod species. In this study, we use this framework to investigate, at the community structure (calanoid copepod) level, the long-term changes in plankton ecosystems related to hydro-climatic variability in the North Sea during the period 1958–1999. A chronology of ecological events that occurred in the North Sea is outlined. In addition to the longterm and year-to-year variability, this study reveals that North Sea plankton ecosystems had 2 dynamic regimes during the period 1958–1999: a cold-biological (1962–1982) and a warm-biological dynamic regime (1984–1999). The impact of the regime shift on the community structure of calanoid copepods and total diversity (as mean number of calanoid copepod species per continuous plankton recorder sample) is detectable in the stratified regions of the North Sea after ca. 1983. This study reveals that the regime shift resulted from the conjunction of both local and regional hydro-climatic forcing and a change in the location of an oceanic biogeographical boundary in the north-east Atlantic Ocean . Results indicate a strong dependence of ecological processes in the North Sea to both hydro-climatic and biological variability in the north-east Atlantic Ocean . If the current climate warming persists, results suggest that this may continue to alter the structure of North Sea ecosystems and lead to other regime shifts, thus making it very challenging to predict future responses of North Sea pelagic ecosystems to climate change.

KEY WORDS: Plankton monitoring · Calanoid copepods · Hydro-climatic forcing · Continuous plankton recorder survey

Beaugrand G., F. Ibanez & J.A. Lindley. 2003. An overview of statistical methods applied to CPR data. Progress in Oceanography, 58, 235-262.

Since the beginning of the Continuous Plankton Recorder (CPR) survey in 1931, information on the abundance of a large number of plankton species or taxa has been obtained on a monthly basis in the northern North Atlantic. The many different ecological issues in which the survey has been involved have led to the application of a range of statistical methods. In this paper, we review some of these methods applied to the CPR data by presenting new and up-to-date analyses. Special attention is devoted to multivariate analysis, which has been used extensively to extract information from the CPR database. Results obtained from recently applied geostatistical methods on CPR data are then considered. An example of a time series decomposition by the use of Eigenvector filtering is presented to illustrate time-series analysis.

Ducrotoy, J.-P. & Ibanez, F. 2002. Ecological groups of estuarine macrobenthic invertebrates in the Baie de Somme (France); changes in time and space. J.Mar.Biol.Ass.UK., 82:749-769

This work is an attempt to interpret a chronological data set on abundances of estuarine soft substrate invertebrates through an ecological approach. The data was collected in the framework of the European programme COST 647 (Coopération Scientifique et Technique) on coastal benthic ecology which terminated in 1992. Species numbers and selected environmental factors were recorded at two stations in the baie de Somme (France) from 1981-1992. Firstly, inter-annual and seasonal variations in benthos numbers were analysed using a plotting procedure based on a non-probabilistic approach, proposed by Andrews in 1972. Ecological groups of species were identified and succession in time described, coinciding with alterations in the landings of cockles Cerastoderma edule. Secondly, the chronological data set was processed through the application of the cumulated function, giving directly intensity and duration of any changes in relation to the climate and water quality, especially possible eutrophication manifestations.

KEY WORDS : Benthos, population dynamiques, eutrophication, distribution free procedure, cumulated sums

Anneville O, S. Souissi, F. Ibanez, V. Ginot , Druart J-C & N. Angeli. 2002. Temporal mapping of phytoplankton assemblages in Lake Geneva: annual and interannual changes in their patterns of succession. Limnol. Oceanogr ., 47 : 1355-1366

Since the early 80´s, Lake Geneva ´s conservation program has led to the decrease in phosphorus concentration. However, in the 90´s, phytoplankton biomass increased and reach now values of the same order than during the period of maximum phosphorus concentration. In order to clarify this paradox and the changes in phytoplankton composition, a statistical method developed recently for mapping spatial assemblages is used. This method, based on hierarchical clustering and bayesian probabilities, allows to determine phytoplankton assemblages and to make up a temporal map showing simultaneously their annual and inter-annual patterns of successions. Six distinct phytoplankton assemblages are identified. Even if the rules that constrain how species are assembled into communities are still subject to debate, a pattern of seasonal assemblage successions, consistent with the C-S-R adaptive strategies and peculiar to the temperate lakes, is observed. The seasonal pattern of successions repeats broadly over years but it is strongly influenced by regional climatic and men-induced changes: 1) The warmer winters and springs recorded in Europe clear since 1988 are responsible for the precocity of the clear water phase 2) in the 90's, because of an earlier and deeper dissolved inorganic phosphorus depletion, the summers are marked by the colonization of phytoplankton assemblage whose species share a common tolerance to low irradiance and thus are able to develop deeper in the water column, where phosphorus is still abundant. Furthermore, since these species are large and no grazed by zooplankton they accumulate and lead to the unexpected high biomass observed last years.

KEY WORDS: Phytoplankton, lake Leman, multivariate time series analysis

Beaugrand G, P.C. Reid, F. Ibanez, J.A. Lindley & M. Edwards. 2002. Reorganisation of North Atlantic marine copepod biodiversity and climate. Science 296 : 1692-1694

We provide evidence of large-scale changes in the biogeography of calanoid copepod crustaceans in the eastern North Atlantic Ocean and European shelf seas.We demonstrate that strong biogeographical shifts in all copepod assemblages have occurred with northward extension of more than 10 °latitude of warm-water species associated with decrease in the number of colder water species.These biogeographical shifts are in agreement with recent changes in the spatial distribution and phenology detected for many taxonomic groups in terrestrial European ecosystems and are related to both the increasing trend in Northern Hemisphere temperature and the North Atlantic Oscillation.

Ibanez F. & A. Conversi. Prediction of missing values and detection of 'exceptional events': a single algorithm. 2002. Ecol. Model., 154:9-23

The detection of extreme events is of primary importance because they often change the initial conditions of a dynamic system. However, the definition of what constitutes an extreme or exceptional event is unclear: what threshold or which rate of occurrence delineates an anomaly? An alternate and precisely specified type of definition might be an event which cannot be predicted by a particular model at a chosen probability. Missing values are unfortunately characteristic of biological oceanographic time series. This characteristic precludes a great deal of numerical treatments. Consequently, several interpolation techniques have been proposed to predict missing values. Most of them are not adequate for planktonic data which are characterized by high heterogeneity. An iterative approach based on the principles of the Eigenvectors Filtering method (EVF) is examined. The limits of the technique are determined through simulation. The same method is then applied for the detection and definition of extreme events. We first apply a crude method to select some maximal or minimal values in a data series (the extreme events), then the selected values are coded as missing values, and finally we evaluate how well the Eigenvector Filtering method is able to reproduce the original "extreme" values. These simulations provide insight into why large peaks (or holes) can be identified as extremes events or not, based on the degree of their prediction.

KEY WORDS : Times series, outliers, missing values, extreme events, plankton

Beaugrand G, F. Ibanez, J.A. Lindley & P.C. Reid. 2002. Diversity of calanoid copepods in the North Atlantic and adjacent seas: species associations. Mar. Ecol . Prog. Series 232: 179-195

Present-day patterns in pelagic biodiversity are the result of the interaction of many factors acting at different scales. Developing an understanding of the processes that regulate the diversity of oceanic ecosystems is thus difficult. In this study, diversity of calanoid copepods was decomposed into species associations by means of the recent method indicator value (Dufrêne & Legendre 1997) and multivariate analyses. For the first time, at an oceanic basin-scale and with a spatial resolution approaching the mesoscale, species associations of calanoid copepods have been identified. Nine species associations were determined and has enabled us to (1) improve the partition of this region recently proposed by Beaugrand et al. (in press) and (2) identify the main factors that regulate pelagic biodiversity in this area. It is shown that the factors (1) temperature, (2) hydrodynamics, (3) stratification and (4) seasonal variability of the environment are likely to be the main factors contributing to the ecological regulation of diversity of calanoid copepods. The similar geographical pattern evident between currents / water masses and the species associations suggest that they can be used as environmental indicator to evaluate long-term changes in pelagic ecosystems and currents related to global warming and other increasing human-induced influences.

KEY WORDS: Pelagic diversity , species associations, Calanoid copépodes, Continuous Plankton Recorder (CPR) survey, Multivariate analyses

Beaugrand G. & F. Ibanez. 2002. Spatial dépendance of pelagic diversity in the North Atlantic Ocean. Mar. Ecol . Prog. Series 232: 197-211

Ecosystems are fundamentally structured in space and time and the identification and the quantification of scales of variability has occupied a central importance in ecology for a few decades. This present study examines spatial changes in the diversity of calanoid copepods and its regional dependence in the North Atlantic Ocean at diel, seasonal and year-to-year scales. Cumulative semi-variograms, proposed by Sen (1989) for geological purposes, are described and extensively used to understand the relationship between diversity and its spatial scales of variability. An average map of the regional dependence in the calanoid diversity is then proposed and diel and seasonal changes examined. This showed that diversity changes at small spatial scales over the European shelf seas. In oceanic areas, diversity changes at large
spatial scale in the subarctic gyre and the northern boundary of the subtropical gyre. Low spatial scales of variability are detected in the Gulf Stream extension, in the path of the North Atlantic Current and west of Europe. A negative relationship betterave diversity and its regional dependence is found in almost all the oceanic regions. This relationship is constant at diel, seasonal and year-to-year scales. At a year-to-year scale, relationships between diversity, regional dependence and climatic indices have been investigated. Some links have been detected but both the intensity and sign of this relationships greatly vary in space. The North Sea regime shift has involved a sharp change in the diversity of calanoid copepods from 1988. A significant strengthening in the contrast between the neritic and oceanic regional dependence has also taken place after the regime shift.

KEY WORDS: Spatial scale of variability , cumulative semi-variograms, Calanoid copépodes, Pelagic diversity, Continuous Plankton Recorder (CPR) survey

Ben Hamadou R., F. Ibanez , S. Souissi & A-C. Cathelineau. 2001. Spatial Analysis of hydrological and phytoplanktonic data of the bay of Tunis. Multivariate Cartography. Mediterranean Marine Science, 2 : 67-85

A method of cartography originally used in geology was adapted to generate regionalization and to obtain 2-D maps of multivariate marine data. The ecological purpose of the method is to divide the studied area through homogeneous regions presenting common multivariate characteristics. Firstly, transformation was applied to the original matrix of hydrological parameters in order to satisfy the condition of multinormality. Then, associative analysis was used in order to produce a partition of sites easy to interpret. The level of heterogeneity between each station and the properties of each group was assessed by measuring the Bayesian probabilities. These conditional probabilities measure the chance that each site has in belonging to a predefined group of sites. Based on the geographical positions of the stations, the probability values for each group of stations were mapped using kriging interpolation algorithm. The obtained maps of iso-probabilities for the different groups of stations were used to define homogenous zones on a single map. Including afterwards the phytoplanktonic dataset, the indicator species were identified for each zone.
This multivariate analysis was applied to a hydrological and phytoplanktonic dataset of the bay of Tunis. Measures at surface were made at 17 stations, monthly sampled during 2 years. The results illustrated a partition of the bay considering four groups, two coastal and two central groups of stations. The importance of the inshore influence was demonstrated in the setting up of such a regionalization through the incoming of alluvium and other products of the seaside activities. The significant presence of the toxic phytoplanktonic community in the bay suggests the need to institute a monitoring program.

KEY WORDS: Mediterranean Sea, bay of Tunis, multivariate classification, multivariate mapping, regionalization, probability, kriging.

Licandro P., A. Conversi, F. Ibanez & J. Jossi. 2001. Time series analysis of interrupted long-term data set (1961-1991) of zooplankton abundance in Gulf of Maine (northern Atlantic, USA).
Oceanologica Acta 24 : 453-466

The main interannual and seasonal signals have been extracted from a multi decadal data set of zooplankton collected with the Continuous Plankton Recorder in the Gulf of Maine, from January 1961 to December 1991. The monthly abundances of seven species or genera of copepods representing the dominant biomass in the area were considered. The presence of a large consecutive gap (35 months) prevented the use of statistical methods for the prediction of missing data. The eigen-vector filtering (EVF) method was then used on the original time series, while retaining the missing values. For each zooplankton taxon, two principal modes of variability (F 1 and F 2 ) were extracted, representing the interannual and seasonal variations, respectively. Results of EVF allowed the classification of the different genera or species, according to their main type of variability, into taxa 'interannually dominated' (C. finmarchicus, Metridia lucens, Oithona spp.), 'seasonally dominated'(Centropages typicus), and taxa characterized by both 'interannual and seasonal variation' (Pseudocalanus spp., Temora longicornis, Acartia spp.). A comparison betterave the interannual trends of 'interannually dominated species' and sea surface temperature (SST) indicated that all the species were more or less correlated with this important environmental factor. In particular, a strong negative correlation was found between C. finmarchicus and SST at a lag of about 0 months, showing that lower values of SST correspond to higher abundances of Calanus finmarchicus at this latitude.

KEY WORDS: Calanus finmarchicus / Gulf of Maine / missing data / time series analysis / zooplankton

Souissi S., F. Ibanez, R. Ben Hamadou J. Boucher, A-C Cathelineau F. Blanchar & J-C Poulard. 2001. New method for multivariate cartography: application to study species assemblages and their habitats by using bottom trawl surveys in the Bay of Biscay (France) . Sarsia 86 : 527-542

This new numerical approach proposes a solution to a fundamental and difficult question in ecology, consisting of the correct geographical representation of multidimensional structures. Firstly, transformation was applied to the original matrix (n sites x q variables) in order to satisfy the condition of multinormality. Then, a hierarchical cluster analysis was used and each hierarchical level was studied and characterised by a certain probability level. For each cut off level an algorithm based on the computation of the Bayesian probabilities produced a smaller matrix (n sites x c groups). These conditional probabilities measure the chance that each site has in belonging to a predefined group of sites. Spatial distributions of these probability values for each group of sites were mapped using kriging interpolation. Finally, the maps were used to define homogenous zones on a single map by superimposing one map on the other. The maximal value of interpolated probability was used as criterion to assign each point of the map to the zones predefined by this classification. This method was applied to map demersal fish habitats by using a dataset from bottom trawl surveys in the Bay of Biscay (France) during October 1990. The boundaries between habitats were identified objectively. Then, the indicator species and species assemblages characterising the different habitats were identified by using an indicator value index. This index integrates the specificity and the fidelity quantities calculated for each species in each habitat. The obtained results showed that this method presented a robust tool to describe the habitat of exploited species. The obtained habitats were validated by their correspondence with depth strata, sediment type and also by the biological characteristics of the indicator species. The proposed method is useful in the study of temporal variations of habitats with regards to species assemblages and can also be generalised to other multivariate databases of different descriptors (physical, chemical, biological, etc.).

KEY WORDS: Multivariate lapping, Cluster analysis, Bayesian probability, Fish habitat, Assemblages, Bay of Biscay.

Beaugrand G, F. Ibanez, J.A. Lindley. 2001 Geographical distribution and seasonal and diel changes in the diversity of calanoid copépodes in the North Atlantic and NorthSea.
Mar. Ecol . Prog. Series 219 : 189_203

This paper examines spatial distribution of the pelagic diversity of calanoid copepods in the North Atlantic and the North Sea, taking into account changes at seasonal and diel scales. Based on 40 years of sampling by the Continuous Plankton Recorder (CPR) survey, the diversity (as the number of taxa) was estimated on a regular grid for each month and time of day. Then, properties of the Principal Component Analysis (PCA) allowed a spatial decomposition of the diversity, detection of major seasonal and diel patterns, the location of regions where they occur and finally, the modelling of temporal changes at seasonal and diel scales. Results underline the importance of hydrography and topography in the regulation of pelagic diversity. By considering these abiotic factors and the characteristics of seasonal and diel changes of the diversity, a partition of the North Atlantic and the North Sea is proposed. This demonstrates the importance of the warm North Atlantic Current and the continental slope currents and undercurrents along the European continental Shelf. It is suggested here that modification in the path or intensity of these currents could imply marked changes in structure and functioning of ecosystems west and north of the British Isles.

KEY WORDS: Pelagic diversity, Calanoid copépodes, Spatial distribution, Seasonal variations, Diel changes
Continuous Plankton Recorder (CPR) survey

Beaugrand G., F. Ibanez & C. Read. 2000. Spatial, seasonal and long-term fluctuations of plankton in relation to hydroclimatic features in the English Channel, Celtic Sea and Biscay bay.
Mar. Ecol. Prog. Series 200 : 93-102

Spatial, seasonal variations and long-term changes of plankton collected by the Continuous Plankton Recorder (CPR) survey were investigated in the English Channel, Celtic Sea and Bay of Biscay from 1979 to 1995. In order to take account of the spatial and temporal structure of biological data, a three-mode Principal Component Analysis (PCA) was developed. The analyses were identified five zones characterised by a similar biological composition, seasonal and inter-annual evolution of the plankton. The planktonic species have stronger year-to-year abundance fluctuations in the English Channel and Celtic Sea than the species offshore in the Bay of Biscay. The changes in abundance of plankton in the English Channel are negatively related to inter-annual changes of climatic conditions from December to March (North Atlantic Oscillation (NAO) index and air temperature). Thus, the negative relationship found by Fromentin & Planque (1996) between year-to-year changes of Calanus finmarchicus abundance in the northern North Atlantic and North Sea and NAO is also found for the most abundant copepods in the Channel. However, the hypothesis proposed to explain the plankton / NAO relationship is different for this region and a new hypothesis is proposed. In the Celtic Sea, relationship between the climatic parameters and the air temperature was found but it is weaker than the English Channel. No relationship was found in the Bay of Biscay.

KEY WORDS: Long-term changes, Spatial variation, Seasonal fluctuation, Three-mode Principal Component Analysis (PCA) , Winter climatic condition

Beaugrand G. , P.C. Reid P.C, Ibanez F. & B. Planque. 2000. Biodiversity of North Atlantic and North Sea calanoid copepods. Mar. Ecol. Prog. Series 204 : 299-303

Spatial patterns in pelagic biodiversity are the result of factors acting from a global to a local scale. The global patterns have been studied intensively using taxa such as foraminifera and euphausiids. However, these studies do not allow direct comparisons of neritic and oceanic régions or examination of relationships between local and régional patterns of pelagic diversity. Here we present a map of the diversity of calanoid copepods, a key planktonic group, sum-marising 40 yr of continuous monthly investigations in the North Atlantic and North Sea. The high number of samples (168 162) allowed mesoscale patterns in diversity to be de-tected for the first time at an ocean-basin level. Our results demonstrate pronounced local spatial variability in plank-tonic diversity and refine previous global studies at a lower resolution. They form a baseline at which long-term changes in planktonic diversity can be better assessed and ecosystem management plans implemented.

KEY WORDS: Pelagic diversity, Calanoid copépodes, North Atlantic, North Sea , Continuous Plankton Recorder (CPR) survey

Licandro P, Ibanez F. 2000. Changes of zooplankton communities in the gulf of Tigullio (Ligurian Sea, Western Mediterranean) from 1985 to 1995. Influence of hydroclimatic factors. J Plank Res 22 : 2225-2253

Year-to-year variations in abundance and composition of zooplankton were studied in the Ligurian Sea at a station sampled two times a month between 1985 and 1995. As a 2 years break (April 1989-December 1990) occurred in the time series, the STATIS method was chosen instead of time series analysis. Each of the nine sampled years was a single table of monthly or seasonal average densities of 26 plankton taxa. STATIS allowed: (1) estimation of similarity between each yearly table, (2) visualisation of the trajectories of both species and observations (seasons) from one year to another, and finally, (3) associations of particular species, which showed similar temporal variations. A strong seasonal variation was evident for most of species and years 1987, 1992 and 1994 were different from the others. Trajectories indicated which species were stable and which ones were characterized by small or large fluctuations during the nine years. Five different taxa associations were detected. For each association the most representative period was identified, where each period was a group of months obtained by clustering on species abundances. Taking into account hydro-climatic factors in the representative periods, a contingency discriminant analysis allowed to identify and characterize the most discriminant environmental parameters associated to each group of species. Environmental factors that best discriminated the different representative periods were atmospheric pressure, current speed and direction and water temperature.

KEY WORDS: Time series, Zooplankton communities, Ligurian Sea, Climate, Hydrology

Nogueira E., F. Ibanez & F.G. Figueiras. 2000. Effect of meteorological and hydrographic disturbances on the microplankton community structure in the Ría de Vigo (NW Spain).
Mar. Ecol. Prog. Series 203 : 23-45

The relationships between meteorological and hydrographic disturbances and micro-plankton community structure and organisation were investigated in the Ría de Vigo, an estuarineecosystem affected by coastal upwelling. The frequency and duration of sampling (ca twice per week from September 1990 to May 1992) are appropriate to reveal the impact of disturbances in the con-text of the seasonal cycle. Perturbations were identified statistically and related to recognisable mete-orological and hydrographic processes that are expected to influence microplankton dynamics. According to the frequency of disturbances (between 8 and 14 yr -1 ) the ecosystem could be classified as intermediate-frequency disturbed in relation to the microplankton community organisation time-scales. Meteorological and thermohaline disturbances promoted changes in microplankton commu-nity structure (disjunctions). The time-series of thermohaline properties, a proxy for allogenic pro-cesses
related with mixing regimes and estuarine circulation, was the best indicator of changes in community structure: 15 out of the 21 disjunctions (ca 70%) coincided with thermohaline distur-bances. Disturbances of the nutrient fields were related to allogenic forcing but also, markedly dur-ing the productive season, to re-structuring of the microplankton community. They pointed out auto-genic community-driven processes. Microplankton assemblages revealed by the species-oriented ordination technique were interpreted in terms of the replication strategies: well-defined groups of competitor (C), disturbance-tolerant ruderal (R) and stress-tolerant (S) species were discerned. At aseasonal time-scale, succession progressed according to the sequence from r- to K-selection strate-gies. C-species dominated spring assemblages, during the period of transient thermoclines, while S-species
contributed more to summer assemblages, when the thermocline was fully developed and the ecosystem was under nutrient stress. R-species showed an intermittent pattern and their relative abundance increased when environmental variability was more acute, during the winter and spring to summer (clear-water phase) transition. The regime of allogenic disturbances operating at interme-diate frequency during the productive season allowed the maintenance of relatively high micro-plankton diversity at the functional (assemblage) level: all types of replication strategies were present during summer and early autumn. The results support the applicability of the intermediate distur-bance hypothesis (IDH) to microplankton community structure in the Ría de Vigo.

KEY WORDS: Disturbances · Microplankton community structure · Replication strategies · Inter-mediate
disturbance hypothesis (IDH) · Ría de Vigo

Ibanez F. 1999. Diversité et ordination. Oceanis 25 : 481-496
(Ibanez. F. Diversity and ordination)

Attention is drawn to some properties of principal component analysis (PCA). Noncentered PCA of proportion data gives an ordination where alfa and beta diversity (within and between sites) are clearly displayed. Centered PCA leads to better representation with little changes and almost identical properties. In order to estimate the contribution of the species to diversity, PCA biplot is proposed: species and sites are projected in the same factorial space. The distances between species and sites can inform about the relative contribution of a species to the diversity into a site. Two examples with planktonic data are treated: a cruise in the Ambar's bay (data from S. Frontier) and a transect crossing the Ligurian front (data from J. Boucher).

KEY WORDS: Principal Component, diversity

Ibanez F & P. Licandro 1998. Stratégie d'analyse de tableaux multiples irrégulièrement espacés dans le temps. Oceanis 24 :
(Ibanez F & P. Licandro 1998. Contingency discrimination analysis of multiple tables irregularly through time.)

With interrupted ecological records, temporal process analysis is not possible. A sampling of plankton in the Ligurian Sea from 1985 to 1995, with a break of almost two years, had been treated by the STATIS method. Each sampled year corresponded to a single table of 26 species at four seasons. STATIS allowed to estimate the similarity between each table-year, and to visualise the trajectories of the species and of the seasons from one year to another. Given a classification of the species, representative periods of the founded groups of species have been detected. A contingency discriminant analysis with monthly data, highligthed the characteristics of each period. Each ones had been associated to some combination of states of hydroclimatic parameters.

KEY WORDS: factorial analysis, discriminant analysis, Information

Ibanez F. & J-C. Dauvin. 1998. Shape analysis of temporal ecological processes : long-term changes in English Channel macrobenthic communities. Coenoses 13 : 115-130

Benthic long term times series reflect the impact of anthropogenic or hydroclimatic factors as well as biological behaviour strategies. To clear up this complexity the TSS method (typology of shapes of series) had been performed using macrobenthic data set from the western part of the English Channel (48 species regularly sampled from 1977 to 1992). TSS (Ibanez & Fromentin 1997) is based on the concept that the shape of temporal variation of a species gives precise information on its response to environmental variables at different scales and on its reproduction strategy. The shape can be characterised by four indices describing the intensity of year to year and seasonal variations, and the degree of intermittence of the series. From the 48 species, 12 groups of similar shapes were detected. Separate analyses were made on groups of species with strong long term trend, others with regular seasonal variation and also species with sporadic occurrence. The effects of the 'Amoco Cadiz' oil spill (spring 1978), and the continuous variation of hydro-climatic parameters on the kinetics of the species were indicated. The method was compared with other techniques used in the analyse of spatial or temporal data.

KEY WORDS: Times series . Multivariate Analysis. Macrobenthic communities. English Channel

Fromentin J.M., Ibanez F., Dauvin J.C, Dewarumez J.M. & B. Elkaïm. 1997. Long-term changes of four macrobenthic assemblages from 1978 to 1992. J.mar.biol.Ass.U.K, 77: 287-310

This study examines whether meso-scale meteorological events, in particular the alternation of cold and mild periods, influenced the structure of four Abra alba communities, sampled from 1977 to 1992 on the northwest French coast. We propose a new numerical procedure to de scribe temporal variations in the structure of each assemblage, using some niche-oriented models recently developed by Tokeshi (1993). The description of the temporal changes in the structure of each community was summarized into a 2D-plot of an ordination, performed on observed and simulated patterns. Results showed that important changes occurred in these four assemblages, which were not directly related to the meso-scale climatic events, but mainly to the local environmental factors and biotic interactions. Furthermore, it appears that stable environnemental conditions would favour more stable structures, but do not determine the precise type of the structure.

KEY WORDS:: marine mollusks, zoo benthos community composition, temperature effects, long-term changes, mathematical models, temporal variations, environmental fac tors, biotic fac tors, abundance

Fromentin J.M., J.C. Dauvin, F. Ibanez, J.M. Dewarumez & B. Elkaïm. 1997. Long-term variations of four community structures. Oceanologica Acta 20 : 43-53

KEY WORDS: marine mollusks, zoobenthos community composition, temperature effects, long-term changes, mathematical models, temporal variations

Ibanez F & J.M. Fromentin. 1997. Une typologie à partir de la forme des séries chronologiques (TFS). Oceanologica Acta 20: 11-25

(Ibanez F & J.M. Fromentin. 1997. A typologie based on the shape of chronological series (TSS) )

The typology of the shapes of series (TSS) aims to gather together species having similar temporal patterns corresponding to different ecological behaviour. Each type of changes, referred to as the ecological shape, is considered to reflect a particular demographic strategy (sudden pullulation of opportunistic species, fluctuations with environmental changes etc.). This méthode, which consists in the definition of four shape parameters and a classification among the series, taking into account these shape parameters, does not replace the usual statistical analysis, mainly multivariate ones, but precedes them. Such preliminary information is usefull for the choice of the susequent treatments, avoiding the need to analyse simultaneously species presenting distinct types of ecological responses. The TSS method was applied on four macrobenthic communities of the English Channel and the south of North Sea, sampled from 1977 to 1992. Clustering among the ecological shapes revealed six different groups. Analysis on the species lacking abundance (very scarce or absent during at least five years) and of species presenting high anomalies (higher than three standard deviatiations) showed that ecological responses on this type can be related to environmental factors such as temperature, atmospheric pressure or the "Amoco Cadiz" oil spill in 1978.

KEY WORDS:: pattern recognition, time series, zoobenthos communities composition;

Planque B., G.C. Hays, F. Ibanez & J.C. Gamble. 1997. Large scale spatial variations in the seasonal abundance of Calanus finmarchicus . Deep Sea Res. ,44 : 315-326

Data collected by the Continuous Plankton Recorder (CPR) survey between 1962-1974 in the North Atlantic and adjacent seas were used to examine large scale spatial variations in the seasonal cycle of near-surface abundance of the copepod Calanus finmarchicus. Through most of this region the dominant seasonal pattern was minimum abundance between November and February followed by an increase to maximum abundance in May. Two large (> 600,000 km2) areas had seasonal cycles that differed markedly from this dominant pattern. South of Newfoundland maximum abundance occurred between February and May, while south of Greenland, maximum abundance occurred between April and October. This delayed seasonal cycle south of Greenland has not been identified previously and it is speculated that régional changes in seasonal patterns may result from régional temperature and/or timing of food variabilité différences.

KEY WORDS:: Calanus finmarchicus, North Atlantic Ocean, Seasonal changes Continuous Plankton Recorder, plankton, zooplankton, copepod

Planque B. & F. Ibanez. 1997. Long-term time series in Calanus finmarchicus abundance - a question of space ? Oceanologica Acta 20 : 159-164

Year-to-year changes in abundance of the copepod Calanus finmarchicus in the North Atlantic is studied by mean of the Continuous Plankton Recorder (CPR). Using data collected during the years 1962 to 1974, the spatial heterogeneity of long-term trends is studied by numéral analysis: Mantel test, Mantel correlogram, and spatio-temporal clustering. Results reveal that (i) interannual changes of C. finmarchicus abundance are spatially autocorrelated, (ii) sizes of the spatial structures vary between 400 and 1100 kms and (iii) there is a high variability in the annual changes observed between the different zones detected by clustering. These results show that observation made in the Northeast Atlantic can not be extrapolated to the whole North Atlantic basin and suggest that identification of size and location of 'homogeneous zone for long-term changes' should be taken into account when determining fac tors responsible for year-to-year fluctuations in abundance of C.finmarchicus.

KEY WORDS:: North Atlantic, Calanus finmarchicus, Long-term changes,
space-time interactions, Continuous Plankton Recorder.

Lehoërff G., Ibanez F., Poniz P. & J.M. Fromentin. 1995. Hydroclimatic relationships with planktonik time series from 1975 to 1992, in the North Sea off Gravelines site, France Mar. Ecol. Prog. Ser 129: 269-281.

Planktonic time series collected since 1975 off Gravelines, France, were analyse in the context of climatic changes. Principal component analysis and the cumulative sums méthod were applied to 30 data sets which included meteorological and hydrological parameters and planktonic descriptors. Eight groups of biological descriptors were linked to external parameters. The study of winds highlighted the importance of cyclonic and anticyclonic influences. Seven years cycles appeared clearly in air temperature and in species abundance with different trophic levels for species such as Temora longicornis, Oikopleura dioica and Sagitta setosa, whereas an 11 yr cycle appeared for Pseudocalanus minutus. A 3 to 4 yr cycle was détected for atmosphéric pressure, precipitation and some species. This cycle may or may not be surimposed on another (for exemple, on an 11 yr cycle).

KEY WORDS: time series, zoo plankton, meteorology, hydrology, Southern North Sea

Fromentin J.M. & F. Ibanez 1994. Year to year changes in meteorological factors of the french coasts during the half century. Exemples of two biological responses. Oceanologica Acta 17: 285-296.

Chronological series (1949 to 1992) of air temperature, precipitation, atmospheric pressure and wind in different parts of the French coast show evidence of important year-to-year changes, trends and cycles: seven-eight years for temperature, and around three years for precipitation and atmospheric pressure. On the scale of France, it appears that spatial heterogeneity of meteorological factors is aller than temporal heterogeneity. New methods, such as the cumulative sums method or the envelopes of a variable reveal the interest for ectoblastes of assaying different numerical approaches. A comparison betterave climatic series and biological series of a benthic and a pelagic species is described for this purpose.

KEY WORDS: environmental effects, climatology, meteorological data, aquatic communities, meteorology, annual variations

Baussant T., F. Ibanez & M. Etienne. 1993. Numeric analysis of planktonic spatial patterns revealed by echograms. Aquat. Living Resour., 6: 175-184

Observations of acoustic images made along a transect perpendicular to the coast, off Villefranche-sur-mer, allow one to recognize the hydrological zone corresponding to a surface density gradient characterizing the Ligurian Sea front (Mediterranean Sea). Combinations of statistical and geometrical parameters from the digitized echoes enable discrimination between different classes of patches in relation to the frontal structure during one transect record on December 20, 1990. Patch recognition is based on the extraction of the general trend of each column and each row of the digitized data matrix by Eigenvector filtering. Multivariate analysis (principal component analysis and discriminant analysis) run on a 650 patches x 19 variables matrix shows a high negative relation between statistic and geometric parameters of the patches. The two main discriminant parameters are shape and echo strength of patches. From the convergence of our results in the Ligurian front with those of previous works made in other frontal region, it is suggested that this method could be generalized for quantifying and standardizing studies of the pat chines of plankton.

KEY WORDS: echosounding, filtering, plankton, Ligurian front, Mediterranean Sea

Ibanez F, J.M. Fromentin & J. Castel. 1993. Application de la méthode des somes cumulées à l'analyse des séries chronologiques océanographiques. C.R Acad.Sci.Paris, Sciences de la vie/Life sciences, 316: 745-748

(Ibanez F, J.M. Fromentin & J. Castel. 1993. Application of the cumulated sum method for the analysis of chronological oceanographic series.)

Study of long-term oceanographical series implies to identify sequences corresponding to different states of biological variables. A simple method, transposed from industrial control technique, was already used in order to test the fit of ecological modelling (Radford & West, 1986). But this method can be also adapted to recognize the location of local trends. A reference value (mean of the series or any meaningfull value) is first substracted from the data, then these residuals are successively added forming a cumulative function. With this function even a small change in the mean of the series causes a strong deviation of its representative curve. Looking at this graph gives directly date and duration of any change. Also the slope of the line joining to points limiting an homogeneous interval allows to estimate the exact local mean of the original series. After a simulation, to test the power of the method, we considered the series of abundance of the copepod Acartia bifilosa , from 1978 to 1991 in the Gironde estuary. Considering the cumulative diagrams allowed to explain the population changes related to variations of salinity and suspended matter concentration. Such simple method could be very useful in a short time, in order to compare several oceanographic series recorded in different laboratories as is the fundamental aim of the national program PNOC (Programe National d'Océanographie Côtière, thème "Séries à long-terme").

KEY WORDS: time series, detection of changes, marine ecological data

Ibanez F. , JC. Dauvin & M. Etienne 1993. Comparaison des évolutions à long-terme (1977-1990) de deux peuplements macrobenthiques de la Baie de Morlaix (Manche Occidentale): relations avec les facteurs hydroclimatiques. J.Exp.Mar.Biol.Ecol., 169: 181-214

(Ibanez F. , JC. Dauvin & M. Etienne 1993. Comparison of long-term variations (1977-1990) between two macrobienne communities of the Bay of Morlaix (English Channel). Relations with hydroclimatic fac tors. )

The quantitative changes of two benthic community from the bay of Morlaix in the western part of the English Channel were sampled since 1977. General trends of the main species were extracted by the Eigen-Filtering method. Principal component analysis and hierarchical classifications were used to identify the successive periods of the series. A comparative analysis of the trend of both series were provided in relation to the hydroclimatic changes observed during the sampling. The patterns were in phase in both communities. Five main periods were identified. The long term temporal changes of both communities were affected by the Amoco Cadiz oil spill: high mortality in 1978 and reconstitution of the populations destroyed by the hydrocarbons, but also by the climatic changes with a 3-4 years period and the warming of the sea water along the last decade in relation to the sun spots.

KEY WORDS: long-term, benthic communities, hydroclimatic fac tors, English Channel

Fromentin J.M., F. Ibanez & P. Legendre 1993. A Phytosociological Method for interpreting Plankton data . Mar.Ecol.Progr.Series 93: 285-306.

Multivariate techniques allow to summarise data sets but are not designed to causally model ecological phenomena. The ambiguity of the interpretation results from the ambiguity of the scaling space. The phytosociological method proposed by Grandjouan (1982) is a general interpretation framework allowing to separately consider three distinct reference spaces: a geographical space to visualise the spatio-temporal distribution of the descriptors, an ecological space showing the effects of the environmental variables on the biological descriptors, and a bio-ethological space showing the statistically meaningful species communities. It is thus possible to define the position of each biological category and each observation along the scale of variation of each environmental variable (hydrological position HP) or each geographic coordinate (geographical position GP), as well as its density relative to these scales (indicative value IV). Using continuous zooplankton data collected as a transect across the Ligurian Sea front (data also used in a previous paper: Boucher et al., 1987), principal component analysis and correspondence analysis were compared to this technique. The phytosociological method produced the most meaningful ecological results about the structure of this frontal ecosystem.

KEY WORDS: multivariate analysis, indicative species, plankton, Ligurian front, Mediterranean Sea