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Infaunal organisms living within marine sediments can provide valuable information about the effect of key environmental factors, acting as ecological indicators e.g. species composition and diversity, tolerance to pollution, or resilience degree facing abiotic stressors such as wave storm events. These organisms may modify their environment through burrowing behavior, enhancing mixing, and nutrient and oxygen cycling, which are crucial for ecosystem health. Simultaneously, such high-energy events (wave storms) may impair the ecophysiology of organisms, altering trophic interactions in this particular food web. A set of behavioral, ecophysiological, and stress/immune responses were monitored for the infaunal clam Polititapes rhomboides exposed to key abiotic stressors identified in our coasts (Rías Baixas, NW Iberian Peninsula) as drivers of massive mortality events in the past: sediment mobilization disturbance (SM) in the bottom seafloor, and seawater warming (SW). Valve opening was clearly reduced during physical disturbance while minor effects were observed for temperature increase (+3 °C, from 15 °C to 18 °C). Nevertheless, a highly resilient behavior was noted for the shell opening of clams (crucial for vital physiological functions) after each physical disturbance cycle, with similar profiles to organisms kept under control calm scenarios. The physiology of clams was also altered by sediment mobilization, resulting in a decline of clearance rates (feeding activity) but only with regard to short-term periods after disturbance (e.g. hours). In contrast, temperature increase caused clearance rates to also increase significantly, linked to the optimal diet supplemented during the experiment. The combination of both stressors (sediment mobilization and temperature increase simultaneously) resulted in elevated oxygen consumption rates and nitric oxide production by the clams as activated responses to stress. Again, the ability of the clams to recover from physical

IntroductionNoise pollution is a major stressor in the marine environment; however, responses of economically and ecologically important invertebrates, such as oysters, are largely unknown. MethodsUnder laboratory conditions, we measured acute behavioral and physiological responses of eastern oysters (Crassostrea virginica) to sound treatments mimicking human activity in the environment. ResultsOysters immediately reduced their valve gape under simulated pile driving sound, but not drilling or boating sound. Pile-driving sound also reduced adductor muscle glycogen, but not triglyceride. None of the sound treatments affected longer-term (12 hours) valve activity levels after the administration of sounds. Interestingly, neither acute nor longer-term valve gaping responses were correlated with glycogen content on the individual level, suggesting that the observed behavioral responses to sound were not mechanistically driven by energetic physiology. DiscussionOur results suggest that C. virginica responds to some, but not all, anthropogenic sounds. Future studies assessing downstream effects on growth, reproduction, and survival in the wild are needed to better understand the effects of anthropogenic sounds on oyster populations and the biological communities they support.

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

A major problem in mussel farming is mussel fall-off from mussel socks due to weakened byssal threads. This weakening is particularly prevalent following spawning events. During the last decades, significant work has been devoted to the production of triploid bivalves, which have a lower reproductive investment. In this study, we compared the byssal properties and energetic rates of triploid and diploid 1-year-old mussels (˂30-mm). To determine the effect of triploidy on byssal threads, diploid and triploid mussels were placed in a recirculating flume to induce the production of byssal filaments. Our results showed that triploid mussels produced up to 65% more threads than the diploids. Furthermore, tensile measurements showed that byssal threads from triploid mussels had higher Young's modulus values (45% increase) and had multiple yield points. Energetic rates and metabolic investments were measured through food assimilation and oxygen consumption. The results showed that triploid mussels had a higher clearance rate (40% increase) and scope for growth (260% increase) when compared to diploids. Morphological comparisons showed variations between the two groups, with triploid mussels having a larger shell height than diploids of the same length

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 Reviewed

Shellfish aquaculture farms, due to their coastal position, face the threat of exposure to harmful algal blooms. Such blooms can release, among others, paralytic shellfish toxins (PST) produced by the dinoflagellate Alexandrium catenella and are known to cause the restriction of bivalve harvesting sites. Shellfish can accumulate PSTs in levels that are poisonous for humans, therefore making them unfit for consumption. Thus, the ability to detect PSTs before they reach the critical threshold is crucial for minimizing losses in the industry. Previous studies have demonstrated that toxic algae detection is possible with the use of an early warning system based on the valve-gaping behaviour of blue mussel Mytilus edulis. However, some studies observed the presence of toxin resistance in other species of bivalves when they are regularly exposed to PSTs. If no resistance is observed whatever the past history of the populations would be with regard to PST exposure, this species could be appropriate as a sentinel candidate. In this study, we compare the valve-gaping behaviour of two blue mussel populations with contrasting long-term histories of PSTs events (i.e., regularly vs. not previously exposed to the PSTs producer) were compared using experimental exposure of A. catenella to M. edulis. It was found that mussels from both populations exhibited similar gaping behaviour patterns when exposed to A. catenella. For both populations, the number of valve closures and closure duration tended to increase in the presence of A. catenella, which suggested an avoidance response to the toxic dinoflagellate. In conclusion, our results support the use of M. edulis without origin discrimination

High-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)

High-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

Mussel farming is an important economic resource for Canada, producing 26101 tonnes of mussels in 2019 worth more than 43 million Canadian dollars. A major cause of loss of production for mussel farmers originates from the fall-off of mussels during their growth. This phenomenon is particularly important during the reproduction season, as mussels invest most of their energy in the reproduction and have less energy for byssogenesis. This leads to byssal weakening, which can ultimately end with the fall-off of the mussels. Recently, there has been an increasing interest in the development of mussel hatcheries and more specifcally on the production of triploid mussels. Indeed, it is known that triploidy often reduces the fertility of bivalves and can even produce sterile bivalves that have more energy to invest in their growth and other vital tissues (e.g. byssus). In this study, we compared the production and mechanical properties of byssal threads of diploid and triploid mussels in relation to their energy budget and reproductive investment. To determine the effect of triploidy on byssal threads, diploid and triploid mussels were placed in a recirculating fume to induce production of byssal threads, then their scope for growth were estimated. The threads were counted and collected for tensile testing. Results show that triploid mussels produced up to 40% more threads than diploidfmussels, with triploid threads eliciting better mechanical properties. From May to September, during the reproductive season, diploid and triploid mussels were harvested in Georgetown Harbour, Prince Edward Island. Gonadosomatic index (GSI), gonad volume, gonad maturation, and sex ratio were determined for both groups. Results showed that while triploid mussels do invest a part of their energy in reproduction, they had lower GSI and gonad volume than the diploids. Also, for all tested groups, triploid gonads were less mature than those of diploids, and their sex ratio was signifcantly altere