Regulating Services of Bivalve Molluscs in the Context of the Carbon Cycle and Implications for Ecosystem Valuation

The role of marine bivalves in the CO2 cycle has been commonly evaluated as the balance between respiration, shell calcium carbonate sequestration, and CO2 release during biogenic calcification; however, this individual-based approach neglects important ecosystem interactions that occur at the population level, e.g. the interaction with phytoplankton populations and benthic-pelagic coupling, which in turn can significantly alter the CO2 cycle. Therefore, an ecosystem approach that accounts for the trophic interactions of bivalves, including the role of dissolved and particulate organic and inorganic carbon cycling, is needed to provide a rigorous assessment of the role of bivalves as a potential sink of CO2. Conversely, the discussion about this potential role needs to be framed in the context of non-harvested vs. harvested populations, given that harvesting represents a net extraction of matter from the ocean. Accordingly, this chapter describes the main processes that affect CO2 cycling and discuss the role of non-harvested and harvested bivalves in the context of sequestering carbon. A budget for deep-fjord waters is presented as a case study.publishedVersio

Translating tools and indicators in territorial RRI

Introduction: By a series of calls within the Horizon 2020 framework programme, the EU funded projects intended to deploy Responsible Research and Innovation (RRI) at a territorial level, in regional research and innovation ecosystems. This paper presents efforts to document and evaluate the achievements in TRANSFORM, one of these projects. Methods: Evaluative inquiry and theoretical reasoning. Results: Noting the need for a general principle to be interpreted, adapted and translated in order to be rendered meaningful at a local level, we studied precisely these multiple territorial translations of RRI, the organizational and institutional orderings with which they co-emerge and the challenges that come with these translations. An important shared feature is that RRI work does not start from zero, but rather builds on pre-existing relationships and repertoires of collaboration. The RRI project is hence a way to continue ongoing work and follow pre-set purposes, aims and objectives, as a form of “maintenance work”. In this very human sense, RRI is deployed with a logic of care in the regional context, while the Horizon 2020 calls and proposals above all are formulated in a logic of choice, to be assessed by indicators. Discussion: We warn against undue standardization of RRI by toolification and use of quantitative indicators, and recommend that RRI performance is monitored by methods of evaluative inquiry.publishedVersio

Potential methodological influences on the determination of particle retention efficiency by suspension feeders: Mytilus edulis and ciona intestinalis

The retention efficiency (RE) of suspension-feeding bivalve molluscs depends on particle size and is generally assumed to decline below a maximum retention of particles larger than 3 to 7 µm. Previous suggestions that the RE spectrum of mussels Mytilus edulis can exhibit variability, possibly as a result of physiological regulation, have been attributed to artifacts associated with the indirect method. The possibility that variable physical properties of seston particles and/or miscalculations can result in inaccurate RE measurements was examined using 3 methodologies (static, flow-through and a new approach based on the static method) and 3 particle sources (natural seston, algal cell monocultures and clay). Measurements obtained with the static method varied depending on the selected sampling interval. However, this artifact can be removed using frequent sampling and a regression analysis approach. Accurate RE measurements can be obtained with the flow-through method when feeding behaviour is flow independent. For all particle suspensions and methods, mussels from the study site in Lysefjord, Norway, had a maximum RE for particles >8–11 µm (1 to 5 September 2015). The RE for smaller particles declined gradually, with 50–60% retention of 4 µm particles and 30–40% retention of 2 µm particles. Differences in the RE size spectra of mussels and tunicates Ciona intestinalis, collected and measured at the same site, further indicated that RE was not influenced by potentially confounding methodological factors. Assumptions regarding the RE spectrum of bivalves have contributed to many conclusions on their ecosystem interactions. The reliability of clearance rate measurements obtained using the indirect method can only be assured if the effective retention of tracer particles is confirmed and not assumed.publishedVersio

High frequency monitoring of feeding activity in benthic suspension feeders

Suspension feeders ecosystem role and services are mainly driven by their efficiency in clearing particles from the water column. As such there is an interest on suspension feeders feeding activity and how they interact with the ecosystem. Advancing research on feeding response requires experimental designs where individuals can be exposed to continuously changing environments and where feeding activity can be monitored at a high frequency and at different time scales. However, interindividual variability or temporal dynamics in feeding behaviors cannot be investigated properly by the methods commonly used. There are several methods to monitor feeding activity of suspension feeders. Among them, the flow-through method allows individuals to be exposed to changing conditions. As with the other existing methods, the flow-through method is labor intensive limiting both the number of individuals that could be observed simultaneously and the time resolution of observations. The flow-through method is constrained by the need to measure the flow rate through the chambers and to take samples to determine particle concentration in the water. In this work, we automated the standard flow-through method using microcontroller based prototyping. The result is a methodological approach that continuously monitor feeding at high frequency and on a larger number of individuals while reducing handling and measurement errors. As such, this method brings a solution to the current limitations when studying suspension feeders feeding behaviors. This work provides the description and assessment of the automated set-up, which is an end to end solution that can readily assembled and configured.publishedVersio

High-Frequency Responses of the Blue Mussel (Mytilus edulis) Feeding and Ingestion Rates to Natural Diets

The feeding activity of bivalves is understood to change in response to a suite of environmental conditions, including food quantity and quality. It has been hypothesized that, by varying feeding rates in response to the available diet, bivalves may be able to maintain relatively stable ingestion rates, allowing them to have constant energy uptake despite changes in food availability. The purpose of this study was to determine if the blue mussel Mytilus edulis responds to fluctuations in natural diets by changing feeding rates to maintain constant ingestion rates. Three four-day experiments were conducted to measure pumping and ingestion rates in response to natural fluctuations in food concentration (chlorophyll a). Experiments were conducted in a flow-through system over the spring season in south-western Norway. Pumping and ingestion rates were measured with high temporal resolution (every 20 min), which permitted the observation of the intra- and interindividual variability of feeding rates. Results show pumping rates varying within individuals over 4 days, and some individuals pumping on average at high rates (~5 Lh−1), and some at low (~1 Lh−1), despite being held in similar conditions. The pumping rate was generally not related to changes in food availability, and population-level ingestion rates increased with increasing food availability. These results suggest that, for this population of M. edulis, feeding rates may not vary with the available diet to produce constant ingestion over time.publishedVersio

Mussel farming production capacity and food web interactions in a mesotrophic environment

Low trophic aquaculture (LTA), such as bivalve farming, offers promising avenues to supply sustainable seafood and aquafeed. While bivalve farming usually occurs in highly productive coastal areas which already support numerous human activities and suffer from environmental pressures, numerical tools offer a promising avenue to explore and assess biomass production potential and associated ecosystemic impacts for further development of the industry and prospection of new exploitation sites. In this study, we coupled an ecophysiological model, the dynamic energy budget theory (DEB), with an ecosystem model (NORWECOM.E2E) to simulate blue mussel Mytilus spp. farming production and effects based on the food web in the mesotrophic Hardangerfjord in western Norway. We tested several levels of fjord-scale farming intensity and assessed 2 production purposes: aquafeed and human consumption. Results suggested the Hardangerfjord could host large-scale mussel farming for both purposes. However, large exploitation schemes displayed detrimental effects on individual mussel growth (39% less wet mass after 2 yr) and especially on secondary production (decrease of 33% after 1 yr) due to acute trophic competition. Simulations showed short production cycles for aquafeed were more efficient to exploit primary production, since young and small mussels have lower maintenance and reproduction costs. Dissolved nutrient inputs from salmonid farms had marginal effects on primary production (<2%). However, salmonid and mussel farming activities could compete for the sites with the highest production potential.publishedVersio

Overvåking av blåskjellbestanden – grunnundersøkelse 2021 og 2022

Blåskjell (Mytilus sp.) er utbredt langs hele kysten av Norge. I de siste 15 årene har Havforskningsinstituttet (HI) mottatt meldinger om at blåskjell er blitt borte fra steder hvor det vanligvis sankes skjell. HI utviklet i 2020 en metode for å overvåke regionale bestander av blåskjell. Overvåkningen har et overordnet mål om å klargjøre om blåskjellbestandene endres over tid. Dersom bestanden er i endring skal overvåkingen også fremskaffe datagrunnlag for å avdekke mulige årsaker til endringer. Overvåkningen ble startet i 2021 og er gjennomført for fire regioner (Øst, Sør, Vest og Nord). Innenfor hver region undersøkes 50 – 100 stasjoner langs tidevannsonen. Hver stasjon dekker vel 100 meter kystlinje. Alle stasjoner er tilfeldig trukket og forekomst av blåskjell bestemmes etter følgende kategorier: i. sammenhengende dekke, ii. flekkvis fordeling eller iii. få eller ingen blåskjell.publishedVersio

Feeding plasticity more than metabolic rate drives the productivity of economically important filter feeders in response to elevated CO2 and reduced salinity

AbstractClimate change driven alterations in salinity and carbonate chemistry are predicted to have significant implications particularly for northern costal organisms, including the economically important filter feeders Mytilus edulis and Ciona intestinalis. However, despite a growing number of studies investigating the biological effects of multiple environmental stressors, the combined effects of elevated pCO2 and reduced salinity remain comparatively understudied. Changes in metabolic costs associated with homeostasis and feeding/digestion in response to environmental stressors may reallocate energy from growth and reproduction, affecting performance. Although these energetic trade-offs in response to changes in routine metabolic rates have been well demonstrated fewer studies have investigated how these are affected by changes in feeding plasticity. Consequently, the present study investigated the combined effects of 26 days’ exposure to elevated pCO2 (500 µatm and 1000 µatm) and reduced salinity (30, 23, and 16) on the energy available for growth and performance (Scope for Growth) in M. edulis and C. intestinalis, and the role of metabolic rate (oxygen uptake) and feeding plasticity [clearance rate (CR) and absorption efficiency] in this process. In M. edulis exposure to elevated pCO2 resulted in a 50% reduction in Scope for Growth. However, elevated pCO2 had a much greater effect on C. intestinalis, with more than a 70% reduction in Scope for Growth. In M. edulis negative responses to elevated pCO2 are also unlikely be further affected by changes in salinity between 16 and 30. Whereas, under future predicted levels of pCO2C. intestinalis showed 100% mortality at a salinity of 16, and a &amp;gt;90% decrease in Scope for Growth with reduced biomass at a salinity of 23. Importantly, this work demonstrates energy available for production is more dependent on feeding plasticity, i.e. the ability to regulate CR and absorption efficiency, in response to multiple stressors than on more commonly studied changes in metabolic rates.</jats:p