Exploring a Mediterranean mesozooplankton 13 year time-series.

Zooplankton plays diverse crucial roles within the marine ecosystem and can also be used as bio- indicator of climate changes since it is very sensitive to environmental changes. Therefore it is essential to consider long-term plankton series. Given the analysis of plankton samples is time- consuming, it requires an effective and rapid analytical method. We have used in this work a supervised learning approach adapted for the semi-automatic classification of digital images of the mesozooplankton of the Bay of Calvi (Corsica, France) by using the Zoo/PhytoImage software. Together with a 11-years long zooplankton time-series, a set of nine environmental variables were monitored in order to identify controlling factors and determine whether the communities were sensitive to global environmental changes. The main components of the mesozooplankton community were characterized by both seasonal and inter-annual variability. Additionally, variation of holoplankton and meroplankton differentiated one from each other. The holoplanktonic community could be split into two subgroups according to its variation in function of the environment: cladocerans and appendicularians, and to a lesser extent, copepods on one hand, and cnidarians, chaetognathes and thaliaceans, on the other hand. Regarding inter-annual variation, one year (2007) showed particularly low production of total zooplankton which was also the case for all the different holoplanktonic taxa. Accounting for that phenomenon were identified some potentially underlying environmental factors. Finally, although water temperature increased significantly over the last years along with the frequency of marine heat wave events, no evident change in the global zooplankton composition was observed yet.STARECAPME

Copper toxicity on coral holobiont photosynthetic processes

Copper (Cu), an essential micronutrient to organisms, may become toxic when present at too high environmental concentrations. This metal remains an aquatic contaminant of concern, notably because of its recent re-use as biocide in metal-based antifouling paints. The aim of this study was to monitor the physiological alterations in a zooxanthellate coral species and its endosymbionts (i.e. the coral holobiont) exposed to increasing Cu concentrations. Nubbins of Seriatopora hystrix were exposed for 8 days in 1 L intermittent respirometers to 5 nominal Cu concentrations: 0-2-5-15-50 ppb. Respirometers were maintained at 25.0±0.2°C with successive open/close cycles of 30 min. A 12/12 hours day-night light regime was applied with constant daylight intensity of 200 μmol photons m-2 s-1. Water renewal rate during the 30 min open cycles was 15 mL.min-1. The photosynthetic performances of coral endosymbionts were assessed daily with a fluorescence imaging system (imaging-PAM). At the end of the 8-days experiment, the maximal photochemical quantum yield (FV/FM) of coral nubbins had decreased by 12% and 38%, respectively, in the 15 ppb and 50 ppb treatments. This decrease was even greater for the effective photochemical quantum yield (ɸPSII) with values dropping by 41% and 54%, respectively. Cu exposure also affected the symbiosis between the coral host and its endosymbionts. Nubbins of the 15 ppb treatment slightly lightened from day 6, whilst nubbins exposed to the 50 ppb treatment lightened from day 3, and started to bleach from day 6. The analysis of nubbins’ primary productivity did not coincide with the above observations, the oxygen production within each respirometer remaining relatively constant during the overall experiment for all treatments. This unexpected observation may be the sign of a compensation mechanism. In conclusion, Cu affected the photosynthetic processes of S. histrix within 8 days from relevant environmental concentrations of 15 ppb. The exposure of corals to toxic chemicals thus has to be considered as an additional stressor to, e.g., ocean acidification or elevated temperature, which may disturb their ecophysiology and lead to bleaching

Technical Note: Artificial coral reef mesocosms for ocean acidification investigations.

info:eu-repo/semantics/publishe

Effects of ocean acidification on the bioerosion by the sea urchin Echinometra mathaei in coral reefs

info:eu-repo/semantics/nonPublishe

Improvement of live coral shipping conditions using an illuminated box

The transportation of live coral nubbins is a major constraint of the coral trade. Corals must be transported within a timeframe of <20 hours using concentrated oxygen to avoid high post-transportation mortality. To understand the effects of transportation water quality on coral nubbin growth and post-transportation mortality, a series of transportation simulations were performed on Seriatopora hystrix. Different water volumes (dry method, 125 ml, 190 ml, and 325 ml) and oxygen concentrations in the gas phase (21 %, 40 %, and 85 %) were tested, and a 24 LED Handy Lamp was added to provide light irradiance of >100 µmol m-2 s-1 in the transportation box. During transportation nubbins extracted calcium carbonate for growth reducing water alkalinity and consequently pH to 6.67. Dissolved oxygen concentration also rapidly decreased to 0.19 mg L-1. The concentration of inorganic nitrogen, particularly ammonium ions, increased after 24 hours and reached very high concentrations after 48 hours. Before 48 hours, the larger the water volume and oxygen concentration, the faster the nubbin growth after transportation. Beyond 48 hours, in all cases, reduction in water quality became critical for nubbins and resulted in partial mortality. Illuminating the transportation box improved water quality for 72 hours using normal air

Impact of elevated pCO2 on acid-base regulation of the sea urchin Echinometra mathaei and its relation to resistance to ocean acidification: A study in mesocosms

Due to their low metabolism and apparent poor ion regulation ability, sea urchins could be particularly sensitive to ocean acidification resulting from increased dissolution of atmospheric carbon dioxide. Therefore, we evaluated the acid-base regulation ability of the coral reef sea urchin Echinometra mathaei and the impact of decreased pH on its growth and respiration activity. The study was conducted in two identical artificial reef mesocosms during seven weeks. Experimental tanks were maintained respectively at mean pHT 7.7 and 8.05 (with field-like night and day variations). The major physico-chemical parameters were identical, only pCO2 and pHT differed. Results indicate that E. mathaei can regulate the pH of its coelomic fluid in the considered range of pH, allowing a sustainable growth and ensuring an unaffected respiratory metabolism, at least at short term

Long-term mesocosms study of the effects of ocean acidification on growth and physiology of the sea urchin Echinometra mathaei

Recent research on the impact of ocean acidification (OA) has highlighted that it is important to conduct long-term experiments including ecosystem interactions in order to better predict the possible effects of elevated pCO2. The goal of the present study was to assess the long-term impact of OA on a suite of physiological parameters of the sea urchin Echinometra mathaei in more realistic food conditions. A long-term experiment was conducted in mesocosms provided with an artificial reef in which the urchins principally fed on algae attached to the reef calcareous substrate. Contrasted pH conditions (pH 7.7 vs control) were established gradually over six months and then maintained for seven more months. Acid-base parameters of the coelomic fluid, growth and respiration rate were monitored throughout the experiment. Results indicate that E.mathaei should be able to regulate its extracellular pH at long-term, through bicarbonate compensation. We suggest that, within sea urchins species, the ability to accumulate bicarbonates is related to their phylogeny but also on the quantity and quality of available food. Growth, respiration rate and mechanical properties of the test were not affected. This ability to resist OA levels expected for 2100at long-term could determine the future of coral reefs, particularly reefs where E.mathaei is the major bioeroder.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

EcoNum, a research unit devoted to marine environment monitoring

The monitoring of coastal environments remains a research domain of great interest and concern. Coastal ecosystems are threatened by natural and human-induced stressors and are, as transitional environments, particularly sensitive to disturbances. EcoNum first research thematic revolves around hermatypic corals, calcifying organisms, and their adaptation potentials to environmental changes including by using original and patented chemostats. The studied organisms are grown and maintained in artificial mesocosms that simulate environmental conditions of a natural system. This infrastructure allows to perform long-term experiments, giving time to organisms to adapt to the tested conditions (e.g., increased temperature or lowered pH). Longer-term studies have demonstrated that many organisms are more resistant to environmental stressors than previously observed on the short-term. EcoNum also studies coastal plankton abundance and diversity. Plankton is particularly sensitive to physicochemical changes of water bodies. The classification and the enumeration of planktonic organisms require specialized tools in order to analyse time series of multiple samples. EcoNum has developed a software for the semi-automatic classification of planktonic organisms called Zoo/PhytoImage. This software has been used to study a 10-year time series of coastal Mediterranean zooplankton samples. The concomitant analysis of environmental parameters registered at high frequency with specific statistical tools such as the R package pastecs allows to understand the processes governing the changes observed in plankton assemblages. The use and the development of statistical tools in R (e.g., Zoo/Phytoimage, pastecs) is a priority of EcoNum to favour open access knowledge and reproductive sciences. EcoNum research topics also focus on coastal ecotoxicology. Chemicals, including trace elements, remain contaminants of concern, mainly in coastal environments that are the final sink of inland pollution sources. The chemical integrity of coastal ecosystems thus has to be accurately monitored. The partitioning of chemicals between their dissolved, particulate and sedimentary phases does not provide information on their bioavailability. EcoNum thus monitors coastal waters using bioindicator species such as seagrasses, mussels or sand worms. A global map of the contamination of the Mediterranean by trace elements has been drawn using seagrasses has bioindicator species. EcoNum also studies trace element ecology and toxicology. For instance, it has demonstrated the toxicity of copper on the coral Seriatopora hystrix and it's symbiont's photosynthetic processes, or its bioaccumulation and basipetal translocation towards rhizomes in the seagrass Posidonia oceanica as reserve nutrient for subsequent leaf growth. Finally, coastal vegetated systems are potential carbon thinks (or sources) in the global carbon cycle. Therefore, EcoNum studies the primary productivity of seagrass meadows, from the individual to the community, with measuring techniques as diverse as PAM-fluorometry or biomass production determination. To conclude, EcoNum is a research unit devoted to marine environment monitoring. It develops research thematics on major coastal communities such as coral reefs, seagrass beds or plankton assemblages and studies their natural dynamics and the effects of stressors on their global functioning