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The macrophyte Gelidium corneum (Hudson) J. V. Lamouroux, 1813 plays an important role as an ecosystem engineer on temperate rocky shores on the northeastern Atlantic coast. However, its cover and population biomass have declined in recent decades within the southern Bay of Biscay. This study aimed to identify the environmental thresholds, with respect to seawater temperature and irradiance, that influence the development capacity of newly formed individuals of G. corneum through vegetative reproduction. Therefore, an in situ experiment was conducted at two depths within the range of distribution of this species (5 and 12 m) and at two coastal sites on the north coast of Spain (east and west coasts of the Cantabria region, Spain). Our results revealed that G. corneum apical fragments undergoing vegetative propagation developed many new shoots over a period of sixteen weeks. The temperature and irradiance seemed to contribute to the length reached by the new fronds, whereas the number of recruits remained constant throughout the duration of the experiment. Given the slow growth rate characteristic of this species, the total shoot length in this study reached 2.97 cm, which confirms the gradual and restrained developmental pattern during the early stages of its life. We also quantified bite marks at the tips of the new plants, and more than three-quarters of them presented these signs by the final month of the study. Our study provides valuable insights into the growth process of the endangered species G. corneum through vegetative propagation and elucidates the impact that abiotic and biotic factors can have on its growth., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The distribution of macroalgal species along the north and northwest coast of the Iberian Peninsula is in a period of change, during which mostly cold-temperate species have decreased in cover and others have disappeared. On the other hand, other species have increased in abundance. These shifts could be related with the modification of environmental factors that determine species distribution caused by climate change. A standardised sampling methodology was applied at 18 sites along the north coast of Spain in 2011 and 2017. The relationship between the coverage of intertidal macroalgal species and abiotic variables (sea surface temperature, air temperature and significant wave height) was analysed in order to detect possible changes in the historical data. Results suggest a modification in the communities in the inner part of the Bay of Biscay, mostly related to an increase in water and air temperature. Each seaweed group (warm-temperate, cold-temperate, opportunistic and exotic species) showed a different pattern of modification. Coralline algae, Bifurcaria bifurcata and Cystoseira baccata have increased, which may be related to the warming trend. The exotic species Asparagopsis armata has also increased, particularly in the Lower Rias. On the other hand, there was a drastic decrease of the cold-temperate species Himanthalia elongata. Data obtained support the relationship of macroalgae species communities and environment in the context of climate change in this particular area., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The Quality of Rocky Bottoms index (CFR by its Spanish acronym) is a multimetric method used for the assessment of macroalgae communities in accordance to the European Water Framework Directive. In order to improve the precision and accuracy of the assessments, the index was adjusted using a continuous scoring system. The index was tested at 184 intertidal and 57 subtidal stations located in the Atlantic coasts of Spain, Portugal and France. The anthropogenic pressure level of the stations was estimated according to a semiquantitative scale based on the type of discharge, distance to the contaminant source and its magnitude. 70.5% of the stations were correctly assigned to their expected quality and only 5.8% were critically misclassified. The linear regression and weighted kappa analyses between the pressure levels and the CFR results showed highly significant correlations and very good agreement levels both at intertidal and subtidal areas., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Phytoplankton monitoring has extended to practically all the regions of the European coast due to the implementation of the European Water Framework Directive. In this way, the study of phytoplankton taxonomic composition and dynamic is being performed in many areas poorly studied or not studied before. During the last years, a monitoring programme has been carried out at the coast of Cantabria region (SE Bay of Biscay); the presence of some potentially toxic and bloom forming species (>7.5 × 10⁵ cells per litre) has been observed. Diatoms and cryptophytes are the main blooming taxa in this region in the majority of the estuaries and in some of the coastal sites. All estuaries and coastal stations showed at least one potentially toxic species, being the dinoflagellates the group with the highest number of taxa observed. The potentially toxic species found in highest concentrations were the genera Pseudo-nitzschia and Chrysochromulina., (Copyright © 2012 Elsevier Ltd. All rights reserved.)