Impact de la mytiliculture sur les communautés planctoniques dans la lagune de Grande-Entrée aux Îles de la Madeleine (Québec, Canada)

RÉSUMÉ : L'aquaculture connaît une croissance continue depuis les 30 dernières années pour répondre aux besoins de la population mondiale. La conchyliculture, contrairement à la pisciculture, est une activité extractive, les mollusques se nourrissant de ce qu ' ils trouvent directement dans le milieu naturel sans apport extérieur. Cette culture repose donc sur la disponibilité de nourriture, celle-ci devant être de qualité et de quantité suffisante pour garantir une bonne productivité sans pour autant nuire à l'intégrité de l'écosystème. Dans ce contexte un programme de recherche a été mis en place afin de déterminer la capacité de support de la lagune de Grande-Entrée aux Îles de la Madeleine. Faisant partie intégrante de ce projet, cette thèse a pour but de déterminer l'impact de la mytiliculture sur les communautés planctoniques dans la lagune de Grande-Entrée. Pour ce faire, trois objectifs ont été élaborés: (i) documenter la composition, l'abondance et la dynamique saisonnière (estivale et automnale) des communautés planctoniques autotrophes et hétérotrophes dans la lagune, (ii) déterminer en mésocosme quelle est l'influence de l'activité de filtration des moules sur les communautés planctoniques et (iii) déterminer in situ l' impact de la ferme aquacole sur les communautés planctoniques de la lagune. Les résultats obtenus montrent que la lagune de Grande-Entrée est caractérisée par des faibles concentrations en sels nutritifs, une dominance de phytoplancton de petite taille, et une importante biomasse de protistes hétérotrophes, mettant en évidence l'importance du réseau microbien dans cet environnement. Des expériences en mésocosmes réalisées afin de déterminer et de quantifier l'impact de la filtration des filières de moules sur ces communautés planctoniques sans influence des courants, ont permis de mettre en évidence le rôle potentiel des hétérotrophes ciliés dans la nutrition des moules, ceux-là représentant la biomasse la plus retenue par les filières de moules (69-88 % de la biomasse totale) suivi par les dinoflagellés et les diatomées. L'influence des filières de moules sur la colonne d' eau estimée par comparaison des données de la ferme aquacole avec l'extérieur, montre une absence d'influence des filières sur les sels nutritifs, la matière organique ainsi que sur les communautés planctoniques, mais active cependant la productivité phytoplanctonique journalière. Les comparaisons avec les données historiques confirment l'absence de changement de l'abondance ou de la composition du plancton. La production actuelle de moules n'est probablement pas assez importante pour exercer une influence significative sur la composition et la biomasse planctonique à l'échelle spatio-temporelle de cette étude, bien qu'elle puisse augmenter la production phytoplanctonique. La diminution occasionnelle des ciliés observée dans la ferme de moules par rapport à l'extérieur suggère que de futures augmentations de la production mytilicole pourraient affecter ces organismes. Des perspectives de recherches sont proposées pour approfondir les recherches d'étude d'impact en cas d'augmentation de la production de moules et également au niveau du métabolisme des moules. -- ABSTRACT : Global aquaculture has steadily increased in the last 30 years to supplement the food requirements of the world population. Contrary to finfish culture, shellfish culture is an extractive process, molluscs requiring no exogenous feeding for their cultivation. Thus, shellfish culture depends on food availability, which should be adequate in terms of quantity but also in quality to guarantee a good productivity of the cultured shellfish without disturbing the integrity of the ecosystem. In this context, a research program was set up to determine the carrying capacity of the Grande-Entrée (GE) lagoon in Magdalen Islands. An integral part of this program, this thesis aims to determine the impact of mussel culture on planktonic communities in this lagoon. The three main objectives are: (i) to document the composition, abundance and the seasonal (spring to faIl) dynamics of autotrophic and heterotrophic planktonic communities in the lagoon, (ii) to determine the influence of mussel socks on planktonic communities using controlled mesocosm experiments, and (iii) to de termine in situ the impact of the mussel farm on planktonic communities in the lagoon, by following stations inside and outside of the farm. The dominance of small-sized phytoplankton cells, low nutrient concentrations and high biomass of heterotrophic protists (mostly ciliates) aU point to the importance of the microbial food web in this environment. Sustained cultivation of suspended mussels in the lagoon suggests that these heterotrophic protists could be an important source of food for the mussels, supplementing the small amount of phytoplankton present. Mesocosm experiments determined and quantified the impact of the filtration of the organisms on the longlines on planktonic communities without the influence of water currents. These experiments demonstrated the importance of ciliated heterotrophs as a major food source for mussels in this environment, contributing 69 to 88 %, followed by dinoflagellates and diatoms. In the lagoon, the influence of the mussellonglines was estimated by comparing observations between the inside and the outside of the mussel farm. Results showed no differences for nutrients, organic matter and planktonic communities but the mussel farm significantly increased phytoplankton daily productivity. The absence of a significant reduction in plankton abundance or composition changes is consistent with historical records in GE lagoon, even though mussel production has increased. Present mussel production is probably not high enough to exert a significant control on plankton composition and biomass at the spatial and time scales studied here, although it can enhance the production rate of phytoplankton. The occasional decrease in ciliates observed at the mussel farm relative to the outside suggests that future increases in mussel production could affect these organisms. Recommendations are provided for future impact studies in this environment, in the case of increased mus sel production, as weIl as for future studies of mus sel metabolism

Aquaculture in coastal urbanized areas : a comparative review of the challenges posed by Harmful Algal Blooms

Increasing global population has resulted in increased urbanization of coastal areas across the globe. Such an increase generates many challenges for sustainable food production and food security. The development of aquaculture has proven to be an extremely good option to ensure food security (uninterrupted supply and good quality of food) by many countries, especially those with urban areas affected by space limitations such as Singapore. However, the implementation of aquaculture is not without its challenges and impacts to the environment, with Harmful Algal Blooms (HABs) being one of the major concerns in coastal waters. In this review we analyze the development of the aquaculture industry with respect to HABs in Singapore and compare it to similar urban areas such as Hong Kong (SAR China), Salalah (Oman), Cape Town (South Africa), Valencia (Spain), Rotterdam (The Netherlands), Tampa bay (USA), Vancouver (Canada), and Sydney (Australia). Along with HABs, the abovementioned urban areas face different challenges in sustainably increasing their aquaculture production with respect to the economy and geography. This review further assesses the different production and monitoring strategies that have been implemented to counter these challenges while sustainably increasing production. The ongoing COVID-19 pandemic has affected the world with lockdowns and border closures resulting in logistical difficulties in seafood trade which has further accentuated the dependencies on food import. We conclude that the challenges faced by urban areas for sustainable achievement of food security through development of the aquaculture industry can be effectively managed through proper planning, management and collaboration of knowledge/skills on an international level.National Research Foundation (NRF)Published versionThis study was supported by the National Research Foundation, Prime’s Minister’s Office, Singapore under its Marine Science Research and Development Programme (Award No. MSRDP-P13) and NRF-NERC-SEAP-2020 grant call, “Understanding the Impact of Plastic Pollution on Marine Ecosystems in South East Asia (South East Asia Plastics (SEAP)” (Award No. SEAP-2020-0003)

Non-proportional bioaccumulation of trace metals and metalloids in the planktonic food web of two Singapore coastal marine inlets with contrasting water residence times

11 pages, 5 figures, 5 tables, 1 appendix supplementary data https://dx.doi.org/10.1016/j.scitotenv.2016.03.234.-- This work is a contribution to the consolidated research group 2014 SGR 498 of the Generalitat de CatalunyaWe analyzed the concentrations of trace metals/metalloids (TMs) in the water, sediment and plankton of two semi-enclosed marine coastal inlets located north of Jurong Island and separated by a causeway (SW Singapore; May 2012-April 2013). The west side of the causeway (west station) has residence times of approximately one year, and the east side of the causeway (east station) has residence times of one month. The concentrations of most of the TMs in water and sediment were higher in the west than in the east station. In the water column, most of the TMs were homogeneously distributed or had higher concentrations at the surface. Preliminary evidence suggests that the TMs are primarily derived from aerosol depositions from oil combustion and industry. Analyses of TMs in seston (>. 0.7 μm; mostly phytoplankton) and zooplankton (>. 100 μm) revealed that the seston from the west station had higher concentrations of most TMs; however, the concentrations of TMs in zooplankton were similar at the two stations. Despite the high levels of TMs in water, sediment and seston, the bioaccumulation detected in zooplankton was moderate, suggesting either the presence of effective detoxification mechanisms or/and the inefficient transfer of TMs from primary producers to higher trophic levels as a result of the complexity of marine planktonic food webs. In summary, the TM concentrations in water and seston are not reliable indicators of the bioaccumulation at higher trophic levels of the food webThis work was funded through grant MadeInPlankton from Singapore National Parks Board - Singapore (NParks) and DHI-NTU Research Centre and Education Hub, Ung EliteForsk grants 10-093759 and 10-094773 from the Danish Ministry for Independent Research to GD, and Projects PROTOS (CTM2009-08783), TOPCOP (CTM2011-23480) and FERMI (CGL2014-59227-R) from the Spanish Ministry of Economy and Competitiveness to ACPeer Reviewe

Impact of a river flash flood on microbial carbon and nitrogen production in a Mediterranean Lagoon (Thau Lagoon, France)

Over half of the total nitrogen, phosphorus, silicate and dissolved organic carbon (DOC) loading was discharged from the Wile River into the Thau Lagoon waters within the first five days of what was considered to be the autumn flash flood period. Such loads represented about 8% and 3% of the yearly averaged total nitrogen and phosphorus load in Thau Lagoon, respectively. Although this event affected >20% of the total lagoon volume, river trace metal loads contributed apparently only weakly to the increase in labile trace metal concentrations in the lagoon surface waters. Differences between theoretical dilution values and observed values were also noticed for phosphate, silicate and dissolved organic carbon (DOC) concentrations. DOC losses (10-50%) mainly through flocculation, together with the substantial increases in some metallic contaminants such as Zn (from 6 to >30 mu g L-1) observed during the flash flood in saline lagoon waters, may have limited the carbon production of bacterial communities. The potential osmotic shock and the increase in turbidity may mainly explain the low phytoplankton C turnover rates (average of 0.02 h(-1)) measured in brackish waters (<30) during periods of heavy flood discharge. The dissolved inorganic nitrogen (DIN: NO3 + NH4) enrichment measured 12 days after the flash flood event in saline lagoon surface waters (from 22 to 143 mu g N L-1) led to a substantial increase in phytoplanktonic C production and associated DIN uptake rates (from 2.6 to 7.0 mu g C L-1 h(-1) and from 0.5 to 1.1 mu g N L-1 h(-1), respectively). Subsequent accumulation in particulate organic carbon and nitrogen was not observed in the area studied during and after the flash flood period, averaging 549 +/- 50 mu g C L-1 and 168 +/- 9 mu g N L-1, respectively. This suggests that most of locally produced microbial production was rapidly filtered by oysters contributing to about 13% of the yearly exploited production in the lagoon and/or exported through sedimentation