Recovery of fishery-stressed seagrass meadows is driven by improvements in wastewater management

As ecosystem engineers, seagrasses provide major benefits to coastal habitats worldwide. Nonetheless, their dynamics remain poorly understood in local areas. Three seagrass (Zostera noltei) meadows located within shellfish beds in Galicia (NW Spain) were selected to assess the intra and inter-annual changes in the habitats by considering the effects of harvesting, temperature and sewage pollution. Seagrass cover increased between April and October, when the sediment temperature ranged from 15 to 20 °C, while in terms of long-term dynamics there was a mean gain of 3 % year−1 between 2004 and 2023. Shellfishing caused mechanical disturbance within the meadows, but the seasonal changes in cover depended on temperature. However, we pointed out the built of new wastewater treatment plants since 1990 that improved water quality as the main driver of the long-term increase in seagrass cover. Environmental policies that enhance seawater quality and limit harvesting pressure are essential to maintain this positive trendAgencia Estatal de Investigación | Ref. RTI2018-095583-B-I00Xunta de Galicia | Ref. ED481A-2020/199Xunta de Galicia | Ref. ED431C 2021/4

Rapid diagnosis of the geospatial distribution of intertidal macroalgae using large-scale UAVs

Macroalgae have been used as indicators of the health of coastal ecosystems, they function as sinks of CO2 and are essential contributors to primary production. With the increase in anthropogenic activities, it is crucial to assess the impact of such activities on these ecosystems. As traditional surveying techniques, although accurate, are time-consuming and their area coverage is limited, novel techniques are required to monitor the coverage and diversity of intertidal macroalgae. We propose a methodology using the free-source Semi-Automatic Classification Plugin from QGIS to use UAV and multispectral cameras for the spatiotemporal monitoring of intertidal macroalgae. We also compared the performance of six classifiers: Minimum Distance (MD), Maximum Likelihood (ML), Spectral Angle Mapping (SAM), Multi-Layer Perceptron (MLP), Random Forest (RF) and Support Vector Machine (SVM), for three types of macroalgae classification: general, taxonomical groups and species. As proof of concept, an intertidal rocky shore in a marine protected area (NW Spain) was studied for four months. RF and SVM achieved similar results, with both being recommended for the general (OASVM = 97.4±1.7 and OARF = 98.3±1.7) and taxonomical groups (OASVM = 91.6±1.9 and OARF = 89.2±4.5). SVM and ML were found to be more suitable for species classification (OASVM = 77.4±11.4 and OAML = 74.2±9.7). SAM and MLP provided the least performant species classifiers because of the overlap in the macroalgae spectral signatures. The plugin showed limitations when tuning the input parameters of the MLP classifier and did not let to add a validation dataset. Additionally, we present an open-access GIS web application, Alganat 2000 GIS web, to facilitate the monitoring and management of coastal areas. We conclude that the proposed methodology using the SVM or ML classifiers is an effective tool for assessing intertidal macroalgal assemblages. Its easy and rapid implementation is beneficial for researchers who are not very familiar with coding and machine learning frameworks and reduces the time and cost of fieldwork. As future work, we propose the combination of the multispectral bands with topographic and spectral indices and to research the application of deep learning models to the classification of intertidal macroalgaeAgencia Estatal de Investigación | Ref. PRTR-C17.I1Universidade de Vigo/CISU

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

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

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

The stress response of the seagrass Zostera noltei and three commercial clam species to low salinity associated with heavy rainfall

Abstract The maintenance of stocks of estuarine species strongly depends on the ability of the species to cope with environmental stress. In NW Spain, commercial clam beds, which are usually co-occupied by the seagrass Zostera noltei, are often exposed to reduced salinity caused by intense rainfalls. Our goals were to evaluate the effects of low salinity events on both juvenile clams and Z. noltei, including their interactions. A mesocosm experiment was performed to simulate three salinity decreases (35–35, 25–10, and 20–5), and several indicators of clam and seagrass performance were measured after 3 and 6 days of exposure and again after a recovery period of 4 days. No differences were observed in the non-native clam Ruditapes philippinarum, while oxygen consumption, clearance rate and growth decreased significantly in the native clams R. decussatus and Venerupis corrugata in response to low salinity stress. Zostera noltei indicators did not vary in response to low salinity exposure, except the sucrose content, which decreased. Moreover, the seagrass buffered juvenile clams from salinity fluctuations in the short term, although the interactions were weak. The species-specific sensitivity to low salinity should be a major concern in future management plans for the shellfish beds in the context of climate change.Agencia Estatal de Investigación | Ref. RTI2018-095583-B-I00Xunta de Galicia | Ref. ED481A-2020/199Xunta de Galicia | Ref. ED431C 2021/4

Modelling Pinus pinea forest management to attain natural regeneration under present and future climatic scenarios

Natural regeneration-based silviculture has been increasingly regarded as a reliable option in sustainable forest management. However, successful natural regeneration is not always easy to achieve. Recently, new concerns have arisen because of changing future climate. To date, regeneration models have proved helpful in decision-making concerning natural regeneration. The implementation of such models into optimization routines is a promising approach in providing forest managers with accurate tools for forest planning. In the present study, we present a stochastic multistage regeneration model for Pinus pinea L. managed woodlands in Central Spain, where regeneration has been historically unsuccessful. The model is able to quantify recruitment under different silviculture alternatives and varying climatic scenarios, with further application to optimize management scheduling. The regeneration process in the species showed high between-year variation, with all subprocesses (seed production, dispersal, germination, predation, and seedling survival) having the potential to become bottlenecks. However, model simulations demonstrate that current intensive management is responsible for regeneration failure in the long term. Specifically, stand densities at rotation age are too low to guarantee adequate dispersal, the optimal density of seed-producing trees being around 150 stems·ha−1. In addition, rotation length needs to be extended up to 120 years to benefit from the higher seed production of older trees. Stochastic optimization confirms these results. Regeneration does not appear to worsen under climate change conditions; the species exhibiting resilience worthy of broader consideration in Mediterranean silviculture

Study protocol for the evaluation of the health effects of superblocks in barcelona : The "salut als carrers" (health in the streets) project

Superblocks are currently being introduced in Barcelona to respond to the city's scarcity of green spaces and high levels of air pollution, traffic injuries, and sedentariness. The aim is to calm the streets by reducing the number of square meters dedicated to private vehicles and to reclaim part of this public space for people. Salut als Carrers (Health in the Streets) is a project to evaluate the potential environmental and health effects of the superblock model with an equity perspective in Barcelona. This study aims to explain the various interventions implemented in different neighborhoods in Barcelona and the methods that will be used to evaluate them in a quasi-experimental and health impact assessment (HIA) approaches. Given the complexity of the intervention evaluated, the project employs mixed methodologies. Quantitative methods include: (a) a pre-post health survey of 1200 people randomly selected from the municipal register asked about self-perceived health and quality of life, social support, mental health, mobility, physical activity, neighborhood characteristics, and housing; (b) pre-post environmental measurements, mainly of nitrogen dioxide (NO), particulate matter of less than 10 µm (PM), and particulate matter of less than 2.5 µm (PM) and black carbon; (c) pre-post environmental walkability measures using the Microscale Audit of Pedestrian Streetscapes (MAPS) tool; (d) use of public space and physical activity levels using the System for Observing Play and Recreation in Communities (SOPARC), a validated observation tool; (e) pre-post traffic injury measures with a comparison group; and (f) the comparison and integration of pre-post assessment with previous HIAs and the improvement of future HIAs. Qualitative studies will be performed to analyze residents' perception of these effects by using: (a) various focus groups according to different participant characteristics who are more or less likely to use the superblocks; and (b) a guerrilla ethnography, which is a method that combines ethnographic observation and semi-structured interviews. This study, which evaluates the impact of an ambitious urban-renewal program on health, will help to assess the effectiveness of public policy in terms of health and health inequalities

Heatwaves during low tide are critical for the physiological performance of intertidal macroalgae under global warming scenarios

The abundance and distribution of intertidal canopy-forming macroalgae are threatened by the increase in sea surface temperature and in the frequency and intensity of heatwaves caused by global warming. This study evaluated the physiological response of predominant intertidal macroalgae in the NW Iberian Peninsula (Bifurcaria bifurcata, Cystoseira tamariscifolia and Codium tomentosum) to increased seawater temperature during immersion and increased air temperatures during consecutive emersion cycles. We combined field mensuration and laboratory experiments in which we measured mortality, growth, maximum quantum yield and C:N content of the macroalgae. Air temperature was a critical factor in determining physiological responses and survivorship of all species, whereas high seawater temperature had sublethal effects. Cystoseira tamariscifolia suffered the greatest decreases in Fv/Fm, growth and the highest mortality under higher air temperatures, whereas C. tomentosum was the most resistant and resilient species. Two consecutive cycles of emersion under atmospheric heatwaves caused cumulative stress in all three macroalgae, affecting the physiological performance and increasing the mortality. The potential expansion of the warm-temperate species B. bifurcata, C. tamariscifolia and C. tomentosum in the NW Iberian Peninsula in response to increasing seawater temperature may be affected by the impact of increased air temperature, especially in a region where the incidence of atmospheric heatwaves is expected to increase.European Maritime and Fisheries FundMinisterio para la Transición Ecológica y el Reto Demográfico (España