Revisiting ecological carrying capacity indices for bivalve culture

Ecological carrying capacity (ECC) indices for bivalve culture rely on key ecosystem turnover rates: 1. clearance time (CT), the time needed for the cultured bivalves to filter the entire bay volume; 2. renewal time (RT), the time required to replace the entire bay volume with external water; and 3. production time (PT), the time needed for phytoplankton biomass renewal via local primary production. These turnover rates are conceptually straightforward but lack measurement standardizations in the context of ECC assessments. This study compares simple turnover rate methods with more complex approaches designed to address key assumptions and improve accuracy. Method comparisons were performed across multiple embayments (systems) in Prince Edward Island, Canada. When crop aggregation and system-scale refiltration effects were considered, CT increased by a factor of 14 to 22 depending on the system and species under cultivation. Seasonal temperature considerations further impacted CT by a factor of 38 to 142. Regarding RT, validated hydrodynamic models and tidal prism models produced remarkably different outcomes; the tidal prism approach underestimated RT by 77–94% across the studied systems. Conversely, PT was unaffected by contrasting phytoplankton parameterization; pre-aquaculture (1969–1970) and contemporary (2011−2012) datasets led to similar PT outcomes. However, other metrics revealed a contemporary shift towards low phytoplankton biomass and smaller phytoplankton cells (picophytoplankton); these observations suggest that PT provides insufficient granularity regarding microalgae biomass replacement. Overall, the study rejects a common assumption that the bay-scale turnover rates serving the conventional CT/RT and CT/PT indices can be easily and accurately parameterized; these indices should be used cautiously in assessing the sustainability of farming activities.publishedVersio

Arduino controlled valvometry equipment for laboratory monitoring

High-Frequency Non-Invasive (HFNI) instruments are currently used in bivalve mollusks in order to use them as bioindicators of the local conditions of the environment. Under the STRAUSS project an Arduino controlled equipment has been developed to log the valve movements activity of clams (Polititapes rhomboides) using Hall-efect sensors. The equipment is able to record at 10Hz the signals of 16 Hall-sensors, to store the records in internal microSD cards and to send the stream of data to a personal computer for storing and plotting them in real-time.Peer Reviewe

Arduino controlled valvometry equipment for mussel raft monitoring

High-Frequency Non-Invasive (HFNI) instruments are currently used in bivalve mollusks in order to use them as bio-indicators of the local conditions of the environment. Under the STRAUSS project an Arduino controlled equipment has been developed to log the valve movements activity of mussels (Mytilus galloprovincialis) using Hall-effect sensors. The equipment is able to record at 10Hz the signals of 27 Hall-sensors, temperature, fluorescence and , to store the records in internal microSD cards and to send the stream of data to in premisses data servers for storing and plotting them.Peer Reviewe

The killer within: Endogenous bacteria accelerate oyster mortality during sustained anoxia

16 pages, 5 figures, 2 tablesSustained periods of anoxia, driven by eutrophication, threaten coastal marine systems and can lead to mass mortalities of even resilient animals such as bivalves. While mortality rates under anoxia are well-studied, the specific mechanism(s) of mortality are less clear. We used a suite of complementary techniques (LT50, histology, 16S rRNA amplicon sequencing, and valvometry) to show that the proliferation of anaerobic bacteria within eastern oysters (Crassostrea virginica) accelerates mortality rate under anoxic conditions. Manipulative laboratory experiments revealed that oyster survival under anoxic conditions was halved when bacteria were present compared to when they were excluded by the broad-spectrum antibiotic chloramphenicol. Histological assessments supported this mechanism and showed infiltration of bacteria in oysters that were not treated with antibiotics compared to a general lack of bacteria when oysters were treated with antibiotics. 16S rRNA amplicon sequencing failed to identify any particular genera of bacteria responsible for mortality, rather a diversity of endogenous anaerobic and/or sulfate-reducing bacteria were common among oysters. In addition, monitoring of oyster valve gaping behavior in the field revealed that oysters showed remarkable valve closure synchrony when first exposed to anoxia. However, oysters periodically opened throughout anoxia/hypoxia in both the lab and field, suggesting that the infiltration of exogenous bacteria from the environment may also influence mortality rates under natural settings. Coupled with previous studies, we posit that mass mortality events in a wide range of coastal bivalves are likely the result of co-morbidity from asphyxiation and bacterial processesThis study was funded by L'Étang Ruisseau Bar Ltd. in partnership with the Department of Fisheries and Oceans of Canada (Aquaculture Collaborative Research and Development Program, project 17-G-02 led by M.R.S.C.), a NSERC Discovery Grant to R.F. (RGPIN-2017-04294), and a Total Development Fund from the New Brunswick Department of Agriculture, Aquaculture and Fisheries to R.F.Peer reviewe

Sediment mobilization and seawater warming affect ecophysiology of the clam polititapes rhomboides

Poster.-- Poster.-- VIII International Symposium on Marine Science, Las Palmas de Gran Canaria, 6-8 July 2022High-energy hydrodynamic events associated to currents and waves may disturb bivalve mollusks´ ecophysiology, especially those buried in the the sea bed due to sediment mobilization. Evidences of massive mortality for the clam Polititapes rhomboides (banded carpet shell clam) in Galicia (NW Spain) have been associated to warm water temperatures and high wave magnitudes above climatic averages and the presence of rickettsias (intracellular prokaryotic colonies) in gills (Villalba et al. 1999; Darriba et al. 2019; Villacieros-Robineau et al. 2021)Project PID2019-106008RB-C21 financed by MCIN/AEI/10.13039/501100011033N

Immune and physiological responses of clams (Polititapes rhomboides) under sediment mobilization and seawater warming conditions

Poster.-- 4th Congress of the International Society of Fish & Shellfish Immunology, December 12-15, 2022, Bode, NorwayHigh-energy hydrodynamic events associated with currents and waves may disturb bivalve mollusks' ecophysiology, especially those buried in the sea bed where the bottom boundary layer dynamics may mobilize and resuspend the surface sediments. Evidence of massive mortality for the clam Polititapes rhomboides (banded carpet shell clam) in 2010 in Galicia (NW Spain) has been associated to warm water temperatures and high wave magnitudes above climatic averages and the presence of rickettsias (intracellular prokaryotic colonies) in gills. To monitor in the laboratory the environmental conditions observed in 2010, clams were subjected to intense sediment mobilization (four cycles of sediment remobilization, each followed by a calm period) and seawater warming (from 15°C to 18°C). Immune system, behavioral, and ecophysiological clams' responses were then evaluated. Nitric oxide (NO) production increased synergistically with seawater warming and sediment remobilization. Taking into account the four cycles of sediment remobilization, clams responded by increasing NO production as early as the first cycle in what we could call an acute effect. However, the most striking effect was the increased NO response after a second stimulation (the following sediment remobilization cycles), suggesting that clams achieve a kind of alertness the first time they are exposed to a stimulus through a mechanism possibly related to "trained immunity". Seawater warming and sediment mobilization presented also synergistic effects causing the lowest valve opening amplitude. Besides, sediment remobilization caused abrupt decrease in clearance rates of clams suggesting that reduced valve opening during this stage may have altered filtration processes of phytoplankton uptake. Metabolic rate as oxygen consumption showed a synergistic increase with both abiotic stressors. Considering the NO response and the ecophysiology data we could suggest that clams respond to stress increasing metabolism to obtain energy (ATP) and oxygen consumption by aerobic respiration. ATP production involves the generation of reactive oxygen species (ROS) including NO as by-products. The anti-oxidant system can balance the ROS production but this could be drastically altered (disruption of cytoskeleton and apoptotic cell death) if ROS production is greater and faster than the antioxidant system can regulate, which seems not to be the case for this particular experimentProject PID2019-106008RB-C21 financed by MCIN/AEl/10.13039/501100011033N

Automatic Tumor-Stroma Separation in Fluorescence TMAs Enables the Quantitative High-Throughput Analysis of Multiple Cancer Biomarkers

The upcoming quantification and automation in biomarker based histological tumor evaluation will require computational methods capable of automatically identifying tumor areas and differentiating them from the stroma. As no single generally applicable tumor biomarker is available, pathology routinely uses morphological criteria as a spatial reference system. We here present and evaluate a method capable of performing the classification in immunofluorescence histological slides solely using a DAPI background stain. Due to the restriction to a single color channel this is inherently challenging. We formed cell graphs based on the topological distribution of the tissue cell nuclei and extracted the corresponding graph features. By using topological, morphological and intensity based features we could systematically quantify and compare the discrimination capability individual features contribute to the overall algorithm. We here show that when classifying fluorescence tissue slides in the DAPI channel, morphological and intensity based features clearly outpace topological ones which have been used exclusively in related previous approaches. We assembled the 15 best features to train a support vector machine based on Keratin stained tumor areas. On a test set of TMAs with 210 cores of triple negative breast cancers our classifier was able to distinguish between tumor and stroma tissue with a total overall accuracy of 88%. Our method yields first results on the discrimination capability of features groups which is essential for an automated tumor diagnostics. Also, it provides an objective spatial reference system for the multiplex analysis of biomarkers in fluorescence immunohistochemistry

Narrow valve gaping in the invasive mussel Limnoperna securis: implications for competition with the indigenous mussel Mytilus galloprovincialis in NW Spain

13 páginas, 3 figuras, 1 tablaThe black pygmy mussel Limnoperna securis (Lamarck 1819) is endemic to the brackish waters of New Zealand and Australia, but over the past decade, it has successfully invaded the inner Galician Rias of NW Spain. There is growing concern that L. securis will expand its range to the outer zones of the Rias, where it would pose a threat to the intensive raft culture of the indigenous mussel Mytilus galloprovincialis (Lamarck 1819). In this paper, we compare the valve-opening behaviour of the two mytilids under simulated raft conditions, i.e. full-strength seawater (35 g l−1) and a low current flow regime (2–5 cm s−1). Modes of valve-opening amplitudes that were most frequently observed in both species were in the range of 60–90 %, indicating a tendency towards full valve openness. Both species displayed circadian periodicity (τ = 24 h): maximal gaping was generally observed during periods of darkness and minimum gaping during daylight hours. The only prominent difference in behaviour between the two species was related to the degree of valve opening. The maximum recorded gape angle was 8.2° (SE = 0.9) for L. securis versus 14.8° (SE = 1.4) for M. galloprovincialis. This difference may place L. securis at a competitive disadvantage on substrates, where the two species coexist, such as over rocky shores or potentially mussel culture ropesThis study was funded by the project AGL2010-16464 (Ministerio de Ciencia e Innovación, Spanish Government).Peer reviewe

Byssus attachment strength of two mytilids in mono-specific and mixed-species mussel beds

Póster presentado en el ICES Anuual Science Conference, A Coruña, Spain, 15-19 September 2014There is a growing interest to understand co-existence processes between marine species in the bio-invasion scenario. Xenostrobus securis is a small mussel endemic to the brackish waters of New Zealand and Australia and has been listed among the “100 Worst Invasive Species”. The mussel Mytilus galloprovincialis is successfully cultivated in Galician Rías. Mussel byssus secretion and its functional strength when subjected to distinct substrate and salinity values were evaluated as the basis to understand dominance patterns within mixed-species beds.This study was funded by the project AGL2010-16464 (Ministerio de Ciencia e Innovación, Spanish Government).Peer reviewe