Assessment of risks associated with extreme climate events in small-scale bivalve fisheries: conceptual maps for decision-making based on a review of recent studies

Extreme climate events, such as heatwaves and torrential rain, affect the physiology and functioning of marine species, especially in estuarine habitats, producing severe ecological and socioeconomic impacts when the affected species support important fisheries, such as artisanal shellfisheries. Studies of the impact of sudden decreases in salinity and increases in temperature were reviewed with the aim of producing comprehensive conceptual maps to aid the management of fisheries of the native clams Ruditapes decussatus and Venerupis corrugata, the introduced Ruditapes philippinarum, and the cockle Cerastoderma edule in Galicia (NW Spain). The maps show the effects on mortality, scope for growth, ability to burrow, changes in gonad development or predation risk. While V. corrugata will generally be more affected by low salinity (5 to 15) or high temperature (30 °C) during only two tidal cycles, C. edule populations may recover. Both species are also expected to become more vulnerable to predators. The clams R. philippinarum and R. decussatus will be more resistant, unless extreme events occur after massive spawning episodes; however, the presence of the intertidal seagrass Zostera noltei may buffer the negative effects of high sediment temperature on the growth of some species, such as R. decussatus. Finally, recommendations for assessing climate risk and designing management actions for shellfisheries are given.Ministerio de Economía y Competitividad | Ref. CTM2014-51935-RXunta de Galicia-FEDER | Ref. GRC2013 004Xunta de Galicia-FEDER | Ref. ED431C 2021/4

Population structure and habitat assessment for two commercial clam species exploited in small-scale fisheries

Small-scale fisheries play a crucial role in providing food and jobs in local communities worldwide. Nonetheless, their environmental impact remains poorly understood. To assess the effect of different levels of harvesting pressure on clam population dynamics, we selected three areas for study within each of three intertidal shellfish beds (in NW Spain) on the basis of historical harvesting pressure. The abundance (up to 149 ind m −2 ) of the introduced clam Ruditapes philippinarum of marketable size was much greater than that of the native R. decussatus (up to 20 ind m −2 ) in all three beds, which is consistent with the low level of recruitment of the native species. Our results suggest that the harvesting pressure did not significantly affect reproduction, which was asynchronous across beds, and that the reproductive period was longer in R. philippinarum than in R. decussatus . Nonetheless, the intertidal system was strongly affected by harvesting, as bare sediment was typical in frequently harvested areas, while sparse or dense patches of the seagrass Zostera noltei occurred in areas where harvesting pressure was scarce or null. The abundance and diversity of non-commercial infaunal species were greatest in unharvested areas. However, commercial clams were not abundant in these areas, possibly due to natural habitat preferences or artificial seeding and movement of clams along the beds. Management plans based on local knowledge of ecosystems are needed to maintain sustainable stocks of R. decussatus and also to limit the effects of harvesting on the systems.Ministerio de Ciencia e Innovación | Ref. RTI2018-095583-B-I00CRUE-CSICXunta de Galicia | Ref. ED481A-2020/199Xunta de Galicia | Ref. ED431C 2021/42NASA | Ref. 80NSSC20K007

Effects of short-term hyposalinity stress on four commercially important bivalves: A proteomic perspective

Increased heavy rainfall can reduce salinity to values close to 0 in estuaries. Lethal and sublethal physiological and behavioural effects of decreases in salinity below ten have already been found to occur in the commercially important clam species Venerupis corrugata, Ruditapes decussatus and R. philippinarum and the cockle Cerastoderma edule, which generate an income of ∼74 million euros annually in Galicia (NW Spain). However, studies of the molecular response to hyposaline stress in bivalves are scarce. This ‘shotgun’ proteomics study evaluates changes in mantle-edge proteins subjected to short-term hyposaline episodes in two different months (March and May) during the gametogenic cycle. We found evidence that the mantle-edge proteome was more responsive to sampling time than to hyposalinity, strongly suggesting that reproductive stages condition the stress response. However, hyposalinity modulated proteome profiles in V. corrugata and C. edule in both months and R. philippinarum in May, involving proteins implicated in protein folding, redox homeostasis, detoxification, cytoskeleton modulation and the regulation of apoptotic, autophagic and lipid degradation pathways. However, proteins that are essential for an optimal osmotic stress response but which are highly energy demanding, such as chaperones, osmoprotectants and DNA repair factors, were found in small relative abundances. In both months in R. decussatus and in March in R. philippinarum, almost no differences between treatments were detected. Concordant trends in the relative abundance of stress response candidate proteins were also obtained in V. corrugata and C. edule in the different months, but not in Ruditapes spp., strongly suggesting that the osmotic stress response in bivalves is complex and possibly influenced by a combination of controlled (sampling time) and uncontrolled variables. In this paper, we report potential molecular targets for studying the response to osmotic stress, especially in the most osmosensitive native species C. edule and V. corrugata, and suggest factors to consider when searching for biomarkers of hyposaline stress in bivalves.Ministerio de Economía y Competitividad | Ref. CTM2014-51935-RXunta de Galicia | Ref. GRC2013-004Xunta de Galicia | Ref. ED431C 2017/46Xunta de Galicia | Ref. ED431C 2020/05Financiado para publicación en acceso aberto: Universidade de Vigo/CISU

Are clam-seagrass interactions affected by heatwaves during emersion?

The increased frequency of heatwaves expected in the context of global warming will affect socio-ecological systems such as shellfish beds at intertidal seagrass meadows. A mesocosm experiment was performed to assess the effects of a simulated atmospheric heatwave during low tide on the bioturbation indicators and growth of the commercial juvenile native Ruditapes decussatus and the introduced clam R. philippinarum, and on their interactions with the seagrass Zostera noltei. Under the heatwave, heat dissipation at 5 cm depth was significantly greater in the sediments below Z. noltei than below bare sand, the photosynthetic efficiency (Fv/Fm) of Z. noltei decreased and the clams tended to grow less. Furthermore, after the heatwave clams below bare sand tended to burrow deeper than those below Z. noltei, indicating that seagrass provided a refuge for clams. Ruditapes philippinarum grew less, and did not burrow as deeply as R. decussatus, which may imply greater vulnerability to desiccation and heat at low tide. The particle displacement coefficient (PDC) of R. philippinarum indicated lower bioturbation values in Z. noltei than in bare sand and was a suitable bioturbation indicator for juvenile Ruditapes spp. clams. In Z. noltei coexisting with R. philippinarum, the Fv/Fm values were higher than without clams after a recovery period, which may be linked to the assimilation of phosphate excreted by the clams and suggests a facilitative interaction. No such interaction was observed with R. deccusatus, probably because of its deeper burrowing depth. The findings suggest reciprocal facilitative interactions between R. philippinarum and Z. noltei and the potential contribution of Z. noltei to the sustainability of clams under global warming scenarios, which may support management actions aimed at enhancing the coexistence between shellfishing activities and seagrass conservation.Agencia Estatal de Investigación | Ref. RTI2018-095583-B-I00Xunta de Galicia | Ref. ED431C 2021/42Xunta de Galicia | Ref. ED481A-2020/199Universidade de Vigo/CISU

The role of biofilms developed under different anthropogenic pressure on recruitment of macro-invertebrates

Microbial biofilms can be key mediators for settlement of macrofoulers. The present study examines the coupled effects of microbial biofilms and local environmental conditions on the composition, structure and functioning of macrofouling assemblages. Settlement of invertebrates over a gradient of human-impacted sites was investigated on local biofilms and on biofilms developed in marine protected areas (MPAs). Special attention was given to the presence of non-indigenous species (NIS), a global problem that can cause important impacts on local assemblages. In general, the formation of macrofouling assemblages was influenced by the identity of the biofilm. However, these relationships varied across levels of anthropogenic pressure, possibly influenced by environmental conditions and the propagule pressure locally available. While the NIS Watersipora subatra seemed to be inhibited by the biofilm developed in the MPA, Diplosoma cf. listerianum seemed to be attracted by biofilm developed in the MPA only under mid anthropogenic pressure. The obtained information is critical for marine environmental management, urgently needed for the establishment of prevention and control mechanisms to minimize the settlement of NIS and mitigate their threats.Xunta de Galicia | Ref. I2C-BXunta de Galicia | Ref. FEDER ED431D 2017/20Xunta de Galicia | Ref. ED431C 2017/46Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação (ARDITI) | Ref. M1420-09-5369-FSE-000001European Regional Development Fund | Ref. M1420-01-0145-FEDER-000001Fundação para a Ciência e Tecnologia | Ref. UIDB/04292/2020Fundação para a Ciência e a Tecnologia | Ref. CEECINST/00098/201

Resilience and Social Adaptation to Climate Change Impacts in Small-Scale Fisheries

[Abstract] Small-cale fisheries are important for livelihoods, food security, jobs and income worldwide. However, they face major challenges, including the increasing effects of climate change that pose serious risks to coastal ecosystems and fishing communities. Although scientific research on climate change impacts has increased in recent years, few studies have explored the social impacts on small-scale fisheries. Using Galicia (Spain) as a case study, we investigated individual and household-level adaptive responses to climate change among fishers in three fishing guilds (Cambados, Campelo, and Redondela). Specifically, we estimated the economic vulnerability of shellfishers and assessed the diversity of social adaptive responses used to deal with climate change. Although fishers’ income strongly depends on shellfishing in all studied areas, our findings show that less fishing experience and lower engagement in fisher associations tend to increase the economic vulnerability of the fishers. The fishers’ vulnerability decreases as the size of households increases, while fishers who pay a mortgage and who live in households with fewer active members tend to be more vulnerable. The findings also show that Galician shellfishers have developed a wide range of adaptation strategies to anticipate and respond to climate change impacts, namely harvesting pricier and more abundant species, reducing household expenses and increasing social involvement in shellfishery associations. Although the adaptive strategies have helped Galician fishers to deal with climate change impacts, several threats to the sustainability of shellfisheries remain, such as a decrease in the abundance of key native shellfish species, and a high dependence on public and private aid to ensure reasonable incomes for shellfisheries. These findings are of interest and relevance to other similar small-scale fisheries around the world facing similar climate change challenges.This research was supported by grants CTM2014- 51935-R from the Spanish Ministerio de Economía y Competitividad to the project MARISCO and the Autonomous government Xunta de Galicia-FEDER (projects GRC2013-004, ED431C 2017/46). SV and PP acknowledge funding from the Xunta de Galicia (RECREGES II project under Grant 1400 ED481B2018/017, and Grupo de Referencia Competitiva GI-2060 AEMI, under Grant 1401 ED431C2019/11), the H2020–European Commission project Atlantic ECOsystems assessment, forecasting & sustainability (AtlantECO, ref. 2019-PI022). SV thanks the financial support for the EQUALSEA project ERC Consolidator, under Grant Agreement n°101002784 funded by the European Research Council. GM was supported by post-doctoral contracts from projects MARISCO and PERCEBES (BiodivERsA COFUND & Spanish Agencia Estatal de Investigación; PCIN-2016-063)Xunta de Galicia; GRC2013-004Xunta de Galicia; ED431C 2017/46Xunta de Galicia; ED481B2018/017Xunta de Galicia; ED431C2019/1

Responses to salinity stress in bivalves: Evidence of ontogenetic changes in energetic physiology on Cerastoderma edule

Estuarine bivalves are especially susceptible to salinity fluctuations. Stage-specific sensibilities may influence the structure and spatial distribution of the populations. Here we investigate differences on the energetic strategy of thread drifters (3–4 mm) and sedentary settlers (9–10 mm) of Cerastoderma edule over a wide range of salinities. Several physiological indicators (clearance, respiration and excretion rates, O:N) were measured during acute (2 days) and acclimated responses (7 days of exposure) for both size classes. Our results revealed a common lethal limit for both developmental stages (Salinity 15) but a larger physiological plasticity of thread drifters than sedentary settlers. Acclimation processes in drifters were initiated after 2 days of exposure and they achieved complete acclimation by day 7. Sedentary settlers delay acclimation and at day 7 feeding activity had not resumed and energetic losses through respiration and excretion were higher at the lowest salinity treatment. Different responses facing salinity stress might be related to differences in habitat of each stage. For sedentary settlers which occupy relatively stable niches, energy optimisation include delaying the initiation of the energetically expensive acclimation processes while drifters which occupy less stable environments require a more flexible process which allow them to optimize energy acquisition as fast as possible.Ministerio de Economía y Competitividad | Ref. CTM2014–51935-RXunta de Galicia | Ref. POS-B/2016/032Xunta de Galicia | Ref. GRC2013–00

Predation risk increases in estuarine bivalves stressed by low salinity

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGSalinity drops in estuaries after heavy rains are expected to increase in frequency and intensity over the next decades, with physiological and ecological consequences for the inhabitant organisms. It was investigated whether low salinity stress increases predation risk on three relevant commercial bivalves in Europe. In laboratory, juveniles of Venerupis corrugata, Cerastoderma edule, and the introduced Ruditapes philippinarum were subjected to low salinities (5, 10 and control 35) during two consecutive days and, afterwards, exposed to one of two common predators in the shellfish beds: the shore crab Carcinus maenas and the gastropod Bolinus brandaris, a non-indigenous species present in some Galician shellfish beds. Two types of choice experiment were done: one offering each predator one prey species previously exposed to one of the three salinities, and the other offering each predator the three prey species at the same time, previously exposed to one of the three salinities. Consumption of both predators and predatory behaviour of C. maenas (handling time, rejections, consumption rate) were measured. Predation rates and foraging behaviour differed, with B. brandaris being more generalist than C. maenas. Still, both predators consumed significantly more stressed (salinity 5 and 10) than non-stressed prey. The overall consumption of the native species C. edule and V. corrugata was greater than that of R. philippinarum, likely due to their vulnerability to low salinity and physical traits (e.g., thinner shell, valve gape). Increasing precipitations can alter salinity gradients in shellfish beds, and thus affect the population dynamics of harvested bivalves via predator–prey interactions.Ministerio de Economía y Competitividad | Ref. CTM2014-51935-RMinisterio de Economía y Competitividad | Ref. BES-2015-074211Xunta de Galicia | Ref. GRC2013-00

Does global warming threaten small-scale bivalve fisheries in NW Spain?

Shellfisheries of the intertidal and shallow subtidal infaunal bivalves Ruditapes decussatus, Ruditapes philippinarum, Venerupis corrugata and Cerastoderma edule are of great socio-economic importance (in terms of landings) in Europe, specifically in the Galician Rías Baixas (NW Spain). However, ocean warming may threaten these fisheries by modifying the geographic distribution of the species and thus affecting productive areas. The present study analysed the impact of rising ocean temperature on the geographical distribution of the thermal comfort areas of these bivalves throughout the 21st century. The Delft3D model was used to downscale climate data from CORDEX and CMIP5 and was run for July and August in three future periods (2025–2049, 2050–2074 and 2075–2099) under the RCP8.5 scenario. The areas with optimal temperature conditions for shellfish harvesting located in the middle and outer parts of the rias may increase in the near future for R. decussatus, V. corrugata and C. edule and decrease in the far future for R. philippinarum. Moreover, shellfish beds located in the shallower areas of the inner parts of the Rías Baixas could be affected by increased water temperature, reducing the productive areas of the four species by the end of the century. The projected changes in thermal condition will probably lead to changes in shellfish harvesting modality (on foot or aboard vessels) with further socio-economic consequences.Xunta de Galicia | Ref. ED481B-2021-103Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED431C 2021/42Ministerio de Economía y Competitividad | Ref. CTM2014-51935-RFundação para a Ciência e a Tecnologia | Ref. UIDP/50017/2020Fundação para a Ciência e a Tecnologia | Ref. UIDB/50017/2020Fundação para a Ciência e a Tecnologia | Ref. LA/P/0094/2020Financiado para publicación en acceso aberto: Universidade de Vigo/CISU

Effects of warming on biological interactions between clams and the seagrass Zostera noltei: A case study using open top chambers

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGBivalves and seagrasses can interact through diverse environmentally-modulated mechanisms. To assess the effects of climate warming on bivalve-seagrass interactions, we carried out a pioneering field experiment in which open top chambers (OTCs) were used to increase air and sediment temperature in a shellfish bed in NW Spain during two consecutive spring tides (16 days of exposure to OTCs). The temperature increase produced by OTCs was significant, as observed in the daily maximum and mean temperature and in degree hours, although the difference was greater in air and at the sediment surface (up to 8 ◦C and 3 ◦C, respectively) than at 5 cm depth (up to 1 ◦C). Warming was less acute in boxes with the seagrass Zostera noltei, which acted as a thermal buffer, reducing the mean temperature by 1 ◦C at the sediment surface in OTC boxes and control boxes (without OTCs). Although the short-term increase in temperature did not greatly affect physiological responses of Z. noltei, the carbohydrate reserves and nutrient content increased in the presence of clams. Growth of the native clam Ruditapes decussatus was significantly slower in OTC boxes with bare sediment, and the seagrass thus buffered the negative effect of warming on growth. The presence of Z. noltei may save clams from having to spend energy to burrow deeper to encounter cooler conditions, leaving more energy available for growth. Conversely, growth of the introduced clam R. philippinarum did not differ between habitats or treatments. Our findings confirm a twoway facilitative interaction that may be particularly important in relation to the resilience of both species in the current context of global warming.Ministerio de Ciencia e Innovación | Ref. RTI2018-095583-B-I00Xunta de Galicia-FEDER | Ref. ED431C 2021/42Xunta de Galicia | Ref. ED481A- 2020/199NASA | Ref. 80NSSC20K007