An integrated approach to coastal and biological observations

Maritime economy, ecosystem-based management and climate change adaptation and mitigation raise emerging needs on coastal ocean and biological observations. Integrated ocean observing aims at optimizing sampling strategies and cost-efficiency, sharing data and best practices, and maximizing the value of the observations for multiple purposes. Recently developed cost-effective, near real time technology such as gliders, radars, ferrybox, and shallow water Argo floats, should be used operationally to generate operational coastal sea observations and analysis. Furthermore, value of disparate coastal ocean observations can be unlocked with multi-dimensional integration on fitness-for-the-purpose, parameter and instrumental. Integration of operational monitoring with offline monitoring programs, such as those for research, ecosystem-based management and commercial purposes, is necessary to fill the gaps. Such integration should lead to a system of networks which can deliver data for all kinds of purposes. Detailed integration activities are identified which should enhance the coastal ocean and biological observing capacity. Ultimately a program is required which integrates physical, biogeochemical and biological observation of the ocean, from coastal to deep-sea environments, bringing together global, regional, and local observation efforts

Comparaison de méthodes d'évaluation de la production secondaire d'une population de l'annélide polychète Ditrupa arietina (O.F. Muller)

We compared the ability of three direct methods (increment summation, loss summation and instantaneous growth rate coefficient), the size-frequency method, and eight indirect methods (Banse and Mosher, Benke, Brey, Edgar, Morin and Bourassa, Plante and Downing, Robertson and Schwinghamer et al.) to measure or to predict the secondary production of a Mediterranean population of the polychaete Ditrupa arietina. This comparison was carried out both on the 1994 cohort during its two-year lifespan and on the entire population during the two years of the study (1994-1996). Our results showed that all three direct methods are more or less equivalent. Results referring to the year 1994-1995 showed a strong overestimation of the actual production by the size frequency method. This is attributed to the existence of an average individual maximal size below which the actual production equals zero. During the same year, the results obtained using indirect methods were highly variable, partly, but not solely, due to the type of environment for which the regression models were built. The incorporation of temperature as an independent variable within the most recent regression models did not contribute to improving the quality of the predictions. Results referring to the year 1995-1996 confirm the incapacity of both the size frequency and the indirect methods to predict changes in the P/B ratio in relation with age structure and recruitment irregularities. These results are discussed in the context of inferring productivities both at the population and the community level.Nous avons comparé les aptitudes de trois méthodes directes (sommation des incréments, sommation des pertes et coefficient de croissance instantanée), de la méthode de fréquence de taille et de huit méthodes indirectes (Banse et Mosher, Benke, Brey, Edgar, Morin et Bourassa, Plante et Downing, Robertson et Schwinghamer et al.) à mesurer ou à prédire le niveau de production secondaire d'une population méditerranéenne de l'annélide polychète Ditrupa arietina. Cette comparaison a porté à la fois sur la seule cohorte ayant recruté au printemps 1994 pendant ses deux années d'existence et sur l'ensemble de la population pendant les deux années d'étude (1994–1996). Dans l'ensemble, les résultats obtenus montrent la quasi-équivalence de toutes les méthodes directes. Une forte surestimation de la production réelle par la méthode de la fréquence de taille est observée avec les résultats de l'année 1994–1995, où l'existence d'une taille moyenne maximale au-delà de laquelle la production est nulle n'est pas prise en compte. Pour cette même année, les résultats obtenus par les méthodes indirectes sont très variables avec, entre autres, le type de milieu pour lesquels les modèles ont été établis. L'introduction de la température dans les modèles les plus récents ne semble pas améliorer la qualité des prédictions. Les résultats de l'année 1995–1996 confirment l'inaptitude de la méthode de fréquence de taille et des méthodes indirectes à rendre compte de l'évolution du rapport P/B en fonction de la structure d'âge et des irrégularités du recrutement. Ces résultats sont discutés en fonction de l'utilisation possible de ces méthodes pour inférer des productivités tant à l'échelle de populations monospécifiques qu'à celle de communautés benthiques dans leur ensemble

Food source of intertidal nematodes in the Bay of Marennes-Oleron (France), as determined by dual stable isotope analysis

Nematodes living on an intertidal mudflat of the Marennes-Oleron Bay (France) were assayed for delta(13)C and delta(15)N ratios together with their potential food resources between July 1992 and May 1993. Results suggest that nematodes do not exploit all the components of the sedimented organic matter (SOM) pool at the same rate. Furthermore, based on coefficients of average trophic enrichment found in the literature for both C and N, the enrichment of nematodes in C-13 and their depletion in N-15 relative to SOM suggest that microphytobenthos constitutes their main food source in this particular environment

Importance of functional biodiversity and species-specific traits of benthic fauna for ecosystem functions in marine sediment

Fauna have been found to regulate important biogeochemical properties and ecosystem functions in benthic environments. In this study, we focused on how functional biodiversity and species-specific traits of benthic macrofauna affect key ecosystem functions related to organic matter mineralization and cycling of nutrients in surface sediments. Dominant benthic invertebrates from the Baltic Sea and the Skagerrak were classified into functional groups in accordance with their behaviour, feeding and sediment reworking activities. Macrofauna species were added in different combinations to defaunated Baltic sediments in 2 parallel microcosm systems fuelled with brackish and marine water. In total, there were 12 treatments that differed in terms of functional diversity of benthic fauna. The experiments demonstrated that faunal activities directly affected benthic oxygen and nutrient fluxes, sediment reactivity and pore-water distribution under both Baltic and Skagerrak conditions. Benthic fluxes, sediment reactivity and pore-water distribution were similar in Baltic and Skagerrak treatments, in which the same functional biodiversity and species-specific traits of benthic macrofauna were observed. Although no significant effects of functional biodiversity could be detected under Baltic or Skagerrak conditions, treatments with bioturbating fauna from the Skagerrak enhanced oxygen consumption and nutrient fluxes compared to treatments with Baltic fauna and Skagerrak fauna with functional groups similar (parallel) to the Baltic fauna. Moreover, speciesspecific traits related to the Skagerrak fauna (e.g. the thalassinid shrimp Calocarls macandreae) exceeded the effects of all other faunal treatments. This suggests that species-specific traits of macrofauna may override species richness and functional biodiversity of macrofauna when regulating important ecosystem properties and functions in benthic environments

Visualization and quantification of marine benthic biogenic structures and particle transport utilizing computer-aided tomography

Computer-aided tomography was used to visualize and quantify biogenic structures (e.g. burrows, shells) in 3 dimensions (3D) by scanning 9 replicate cores obtained from a 41 m deep station in the Gullmarsfjord (Skagerrak, western Sweden). The main objective was to visualize and quantify the biogenic structures and their volumes in the sediment. In addition, the particle transport was studied by adding an aluminum oxide tracer to the sediment-water interface (SWI), which was analysed after 57, 80 and 128 h, in 3 replicate cores each time. A new software programme was developed for rapid and accurate analysis. The fauna in the cores, analysed after scanning, were dominated by the brittle stars Amphiura filiformis and A. chiajei. The volumes of 'active' biogenic structures, defined as connecting to the SWI, were generally greatest close to the interface with some secondary peaks, probably related to the position of the disc chamber of the brittle stars. A mean volume of 560 cm(3) of biogenic structures per m(2) of sediment surface was recorded within the sediment (down to a mean depth of 137 mm, where the biogenic structures ceased to be 'active'). Ejection of particles to the SWI (mounding) was calculated to be between 4 and 40 mm(3) h(-1)

Effects of demersal trawling on marine sedimentary habitats analysed by sediment profile imagery

Demersal trawling causes one of the most widespread physical and biological changes in marine shallow and shelf sedimentary habitats: trawl otter boards may create furrows in the sediment surface, while trawl nets and attached weights scrape the sediment surface. As a consequence, benthic animals are disturbed or killed, and resuspension of particles increase. The impact of trawling on benthic animals has traditionally been analysed by changes in species composition and abundance, whereas frequency and distribution of trawl tracks are frequently analysed by side-scan sonar. We have used sediment profile images (SPIs) (30 x 22 cm) and observed furrows and other physical disturbances on the sediment surface that we attribute to trawling. In a manipulative experimental trawl study in Sweden (BACI design), significant impacts were found in trawled benthic habitats (73-93 m deep) compared with pre-trawling conditions and with reference areas. In particular, furrows from trawl boards had a severe ecological impact. In the Gulf of Lions (northwest Mediterranean), similar patterns were observed in the vast majority of 76 images taken at random at depths between 35 and 88 m in four different areas. Epifauna and polychaete tubes were generally either rare or not observed at all on trawled sediment surfaces. Burrows and feeding voids were, however, frequently present in some trawled areas and seemed to be comparatively less affected. Such biogenic structures in the sediment were generally associated with rather deep (3-4 cm) mean apparent redox profile discontinuities (aRPDs), which were measured digitally as the visible division zone between oxidised (sub-oxic) and reduced sediments. Increased roughness caused by the trawl boards acting on the sediment surface, e.g. depressions and protrusions, could have effects on sediment solute fluxes. (C) 2002 Elsevier Science B.V. All rights reserved

Development and validation of a video analysis software for marine benthic applications

Our aim in the EU funded JERICO project was to develop a flexible and scalable imaging platform that could be used in the widest possible set of ecological situations. Depending on research objectives, both image acquisition and analysis procedures may indeed differ. Up to now the attempts for automating image analysis procedures have consisted of the development of pieces of software specifically designed for a given objective. This led to the conception of a new software: AVIExplore. Its general architecture and its three constitutive modules: AVIExplore – Mobile, AVIExplore – Fixed and AVIExplore – ScriptEdit are presented. AVIExplore provides a unique environment for video analysis. Its main features include: (1) image selection tools allowing for the division of videos in homogeneous sections, (2) automatic extraction of targeted information, (3) solutions for long-term time-series as well as large scale image acquisition, (4) real time acquisition and in some cases real time analysis, (5) a large range of customized image-analysis possibilities through a script editor. The flexibility of use of AVIExplore is illustrated and validated by three case studies: (1) Coral identification and mapping, (2) Identification and quantification of different types of behaviors in a mud shrimp, and (3) Quantification of filtering activity in a passive suspension-feeder. The accuracy of the software is measured comparing with visual assessment. It is: 90.2%, 82.7%, and 98.3% for the three case studies, respectively. Some of the advantages and current limitations of the software as well as some of its foreseen advancements are then briefly discussed

Impact of natural (storm) and anthropogenic (trawling) sediment resuspension on particulate organic matter in coastal environments

In order to assess the impact of natural and anthropogenic sediment resuspension on quantity, biochemical composition and bioavailability of particulate organic matter (POM), two field investigations were carried out in two shallow coastal areas of the Mediterranean Sea. In the Gulf of Lions, we investigated the impact of a storm resuspension of sediment, whereas in the Thermaikos Gulf we investigated the impact of bottom trawling. Resuspension in the Gulf of Lions determined the increase of sedimentation rates, modified the composition of the organic fraction of settling particles and decreased the labile fraction of POM, as indicated by a drop in the enzymatically hydrolysable amino acid fraction. The increase in the refractory fraction, following short-term storm-induced resuspension, increased also the contribution of glycine and decreased the contribution of aspartic acid contents to the total amino acid pools. Trawling activities in Thermaikos Gulf determined a significant increase in suspended POM concentrations and important changes in its biochemical composition. After trawling, the protein to carbohydrate ratio decreased (as a result of a major input of sedimentary carbohydrates at the water-sediment interface) and the fraction of enzymatically hydrolysable biopolymeric C decreased by ≈30%, thus reducing the bioavailability of resuspended organic particles. Results of the present study indicate that changes in suspended POM, induced by storms and trawling activities, can have similar consequences on benthic systems and on food webs. In fact, the potential benefit of increased organic particle concentration for suspension feeders, is depressed by the shift of suspended food particles towards a more refractory composition

Quantification of sediment reworking rates in bioturbation research: a review

This review lists and discusses the different methods currently available to assess sediment reworking by benthic infauna. Direct methods are used to estimate the amount of sediment transported by infauna at the sediment-water interface during a given period of time. Particle-tracer methods are used to quantify the vertical distribution of particle tracers within the sediment column. Tracers are classified based on their mode of introduction at the sediment-water interface (i.e. whether they occur naturally or are deliberately introduced at the onset of the experiment). The main characteristics of each method, including modelling aspects, are presented, and their respective advantages and drawbacks are outlined with a particular emphasis on their accuracy, spatial (i.e. both horizontal and vertical) and temporal resolutions. Direct and particle-tracer methods assess different components of sediment reworking. Selection of the most appropriate approach depends on the specific question(s) to be answered, as well as other factors, including the behaviour of the organisms studied, the spatial and temporal scales considered, and whether the experiments are carried out in situ or under controlled laboratory conditions