Publications

Abstract The bathypelagic ocean (1000-4000 m depth) is the largest aquatic biome on Earth but it is still largely unexplored. Due to its prevalent low dissolved organic carbon concentrations, most of the prokaryotic metabolic activity is assumed to be associated to particles. The role of free-living prokaryotes has thus been mostly ignored, except that of some chemolithoautotrophic lineages. Here we used a global bathypelagic survey of size-fractionated metagenomic and 16S (genes and transcripts) data and performed a differential abundance analysis to explore the functional traits of the different prokaryotic life-strategies, their contribution to the active microbiome, and the role that the quality of the dissolved organic matter (DOM) plays in driving this contribution. We found that free-living prokaryotes have limited capacity to uplift their metabolism in response to environmental changes and display comparatively lower growth rates than particle associated prokaryotes, but are responsible for the synthesis of vitamins in the bathypelagic. Furthermore, their contribution to the active prokaryotic microbiome increased towards waters depleted of labile DOM, which represented a large fraction of the tropical and subtropical ocean sampled stations. This points to a relevant yet overlooked role of free-living prokaryotes in DOM cycling in the vast bathypelagic desert.

Introduction The Red Sea is a narrow rift basin characterized by latitudinal environmental gradients which shape the diversity and distribution of reef-dwelling organisms. Studies on Symbiodiniaceae associated with select hard coral taxa present species- specific assemblages and concordant variation patterns from the North to southeast Red Sea coast at depths shallower than 30 m. At mesophotic depths, however, algal diversity studies are rare. Here, we characterize for the first-time host-associated algal communities of a mesophotic specialist coral species, Leptoseris cf. striatus , along the Saudi Arabian Red Sea coast. Methods We sampled 56 coral colonies spanning the eastern Red Sea coastline from the Northern Red Sea to the Farasan Banks in the South, and across two sampling periods, Fall 2020 and Spring 2022. We used Next Generation Sequencing of the ITS2 marker region in conjunction with SymPortal to denote algal assemblages. Results and discussion Our results show a relatively stable coral species-specific interaction with algae from the genus Cladocopium along the examined latitudinal gradient, with the appearance, in a smaller proportion, of presumed thermally tolerant algal taxa in the genera Symbiodinium and Durusdinium during the warmer season (Fall 2020). Contrary to shallow water corals, our results do not show a change in Symbiodiniaceae community composition from North to South in this mesophotic specialist species. However, our study highlights for the first time that symbiont communities are subject to change over time at mesophotic depth, which could represent an important phenomenon to address in future studies.

Significance We report the results of a 10,106-person pan-European survey of public awareness, concerns, and priorities about marine anthropogenic impacts as a way to inform both science and policy initiatives in achieving marine sustainability. Results enable scientists and policymakers to understand how the public relates to the marine environment and how they frame impacts and can help make managerial, scientific, and policy priorities more responsive to public values.

1. INTRODUCTION <em>MalaMix </em>is a compiled metabarcoding dataset composed of 451 marine samples collected from a range of depths - from the surface (3m) to deep waters (as far down as 4800m). This dataset covers three ocean layers: the epi- (0-200m – including DCM), meso- (200-1000m) and bathypelagic (1000-4000m). <em>MalaMix</em> combines samples obtained during two oceanographic expeditions with similar sampling strategies: i) the Malaspina-2010 global expedition that produced 263 samples collected between December 2010 and July 2011 from 120 stations distributed along the tropical and subtropical portions (latitudes between 35° N and 40° S) of the Pacific, Atlantic and Indian oceans; and ii) the <em>HotMix</em> trans-Mediterranean cruise that produced 188 samples collected between April and May 2014 in 29 stations distributed along the whole Mediterranean Sea (from -5° W to 33° E) and the adjacent Northeast Atlantic Ocean. <em>MalaMix</em> comprises: a 16S-V4V5 rRNA gene ASV table (MalaMix_16S.csv); an 18S-V4 rRNA gene ASV table (MalaMix_18S.csv); two tables of contextual metadata (MalaMix_EnvData_16S and MalaMix_EnvData_18S) including 6 standardized environmental parameters (temperature [°C], salinity, fluorescence, PO₄³⁻[µmol L^-1], NO₃⁻[µmol L^-1], and SiO₂[µmol L^-1]) as well as species taxonomic and phylogenetic diversity metrics a table (MalaMix_FCdata.csv) with flow cytometry microbial counts [cell mL^-1] and bacterial activity measurements [pmol Leu L^-1 h^-1]; a README file (README_Metadata.csv) describing the meaning and units of each variable column in the metadata tables. The raw DNA sequences are publicly available at the European Nucleotide Archive (https://www.ebi.ac.uk/ena) under accession numbers PRJEB23913 [18S rRNA genes] &amp; PRJEB25224 [16S rRNA genes] for the Malaspina surface dataset; PRJEB23771 [18S rRNA genes] &amp; PRJEB45015 [16S rRNA genes] for the Malaspina vertical profiles; PRJEB45011 [16S rRNA genes] &amp; PRJEB45014 [18S rRNA genes] for the Malaspina deep sea dataset; and PRJEB44683 [18S rRNA genes] &amp; PRJEB44474 [16S rRNA genes] for the HotMix expedition. Further methodological details are available here: https://www.biorxiv.org/content/10.1101/2023.01.13.523743v1 2. FUTURE FORMAT CHANGES No major changes are expected for the main general format of the database. 3. ACKNOWLEDGMENTS The current dataset was generated with funds from the projects INTERACTOMICS (CTM2015-69936-P, MINECO, Spain), MicroEcoSystems (240904, RCN, Norway), MINIME (PID2019-105775RB-I00, AEI, Spain), and PID2021-125469NB-C31 (AEI, Spain), as well as DOREMI (CTM2012-34294) and HOTMIX (CTM2011-30010-C02-01 and CTM2011-30010-C02-02) of the Spanish Ministry of Economy and Innovation, co-financed with FEDER funds. 4. COPYRIGHT NOTICE<br> <br> This database is provided “as is” and without any warranty of any kind, of openly available for non-commerical purposes (CC BY-NC). <strong>CC BY-NC</strong> means that users can make use of the work (including copying, distributing, adapting and building upon the work), but only for noncommercial purposes and as long as attribution is given to the creator: https://oabooks-toolkit.org/lifecycle/article/4012101-choosing-a-license

The increasing use of molecular tools to study populations of clonal organisms leads us to question whether the low polymorphism found in many studies reflects limited genetic diversity in populations or the limitations of the markers used. Here we used microsatellite datasets for two sea grass species to provide a combinatory statistic, combined with a likelihood approach to estimate the probability of identical multilocus genotypes (MLGs) to be shared by distinct individuals, in order to ascertain the efficiency of the markers used and to optimize cost-efficiently the choice of markers to use for deriving unbiased estimates of genetic diversity. These results strongly indicate that conclusions from studies on clonal organisms derived using markers showing low polymorphism, including microsatellites, should be reassessed using appropriate polymorphic markers.

Ocean deoxygenation, driven by warming and eutrophication, poses an escalating threat to marine biodiversity. In tropical coastal ecosystems, diel cycles naturally produce substantial oxygen variability, with nighttime deoxygenation driven by community respiration and daytime oxygenation from intense photosynthesis, regularly reaching levels of supersaturation (&gt;100% air saturation). Critically, these supersaturation peaks coincide with peak daily temperatures, raising the question of whether elevated oxygen levels can buffer organisms against acute thermal stress. To test this, we exposed newly hatched Amphiprion bicinctus larvae to three oxygen regimes—deoxygenation (approx. 4 mg l⁻¹), air saturation (approx. 6 mg l⁻¹) and supersaturation (approx. 12 mg l⁻¹)—under ramping temperatures (+0.5°C h⁻¹, 30–34°C). Larvae under deoxygenation exhibited the lowest lethal temperature for 50% mortality (LT₅₀= 30.2°C), while both air-saturated (31.3°C) and supersaturated (31.54°C) treatments improved thermal resistance. Mortality remained lower under supersaturation up to 31.5°C, with slower declines than in other treatments. Additionally, parental care increased daytime oxygen in egg masses by approximately 51%, enhancing oxygenation. These results show that oxygen supersaturation—naturally occurring during thermal peaks—can mitigate physiological stress during development. This highlights an underrecognized role of diel oxygen dynamics in climate resilience, with implications for the management of marine nurseries, fisheries and aquaculture under warming conditions.

Seaweed aquaculture is a rapidly growing component of marine food production, but the capacity to control seaweed growth lacks behind that of land agriculture. Seaweed growth requires nutrients, acquired from dissolved pools through their fronds, and light, and, as may also be density-dependent, but general relationships between seaweed growth, nutrient concentration and incident irradiance are not yet available. We used a dataset of 1729 experimental assessments of seaweed specific growth rates and density under various nutrient and irradiance levels retrieved from the published literature to examine the relationship between seaweed growth, density, irradiance and nutrient concentration. This analysis confirmed strong density-dependence of seaweed specific growth rates, and further confirmed that nutrient and irradiance limitation strongly impose density-dependent seaweed growth. These findings demonstrate that nutrient and irradiance limitation modulate density-dependent seaweed growth, and can help maximize growth rates in seaweed aquaculture, a rapidly growing component of global aquaculture production, by manipulating stocking density where nutrients are scarce and/or underwater light penetration poor.

No abstract is provided for this article.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 172:239-251 (1998) - doi:10.3354/meps172239 Larval abundance, recruitment and early mortality in Paracentrotus lividus (Echinoidea). Interannual variability and plankton-benthos coupling Salvador López1, Xavier Turon1,*, Elena Montero1, Cruz Palacín1, Carlos M. Duarte2, Isabel Tarjuelo1 1Dept of Animal Biology (Invertebrates), Faculty of Biology, Univ. of Barcelona, 645, Diagonal Ave, E-08028 Barcelona, Spain 2Centre d'Estudis Avançats (CSIC), Camí de Sta. Bàrbara, s/n, E-17300 Blanes (Girona), Spain *Addressee for correspondence. E-mail: xaviert@porthos.bio.ub.es ABSTRACT: The temporal patterns of larval abundance, recruitment and early mortality in the sea urchin Paracentrotus lividus (Lamarck) in the northwestern Mediterranean were studied by combining planktonic and benthic surveys. The abundance of planktonic stages was monitored by weekly plankton hauls from 1992 to 1996. The presence of juveniles was studied by collecting epibenthic samples at monthly intervals from 1992 to 1995. The size distribution of the same population was studied in 1993. A main recruitment episode in late spring-summer occurred every year, although small recruitment events had been observed in autumn and winter. Interannual variability in larval abundance and recruitment was high, both being most intense in 1992, when up to 33.47 larvae m-3 were recorded in plankton samples, and up to 23000 recruits (sea urchins <2 mm) m-2 were found in the benthic samples. We estimated that only about 12.7% of larvae (from the 8-armed stage onwards) survived the planktonic life, and that 0.5 to 0.7% of the settlers survived until they reached a diameter of 2 mm, while 0.040% of settlers survived the first year of benthic life and only 0.028% of settlers may attain reproductive size. The main bottlenecks in the dynamics of this species occurred, therefore, during the planktonic phase and the first year of benthic existence, particularly during the early post-settlement phase. The benthic samples provided a more robust depiction of events than planktonic data, which featured a higher variability. There was a significant relationship between the interannual variation in the late winter phytoplankton bloom and the spring peak of larvae of this species, indicating that changes in larval abundance are coherent with changes in planktonic primary production. There was also an exponential negative relationship between the abundance of larvae and abundance of recruits relative to larvae over the years studied, indicating density-dependent mortality rates in the planktonic and early benthic stages. Successful cohorts of this species can be traced to years with high larval abundance, which in turn are related to episodes of high planktonic primary production. KEY WORDS: Plankton-benthos coupling · Larval abundance · Recruitment · Early mortality · Echinoidea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 172. Publication date: October 22, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.