Publications

Observations are essential to explore and discover the ocean. The rapid advancements in technology have revolutionized our capacity to document the ocean and its diverse array of species, pushing the boundaries of our understanding further than ever before. The central Red Sea was exposed as part of the Red Sea Decade Expedition , which took place from 04 February to 18 June 2022 aboard the R/V OceanXplorer, using underwater submersibles. Here, for the first time in the Red Sea, we reported three observations of living Firoloida desmarestia specimens, one female and two male specimens, a heteropod from the Pterotracheidae family. This shell-less mollusk has been observed in the epipelagic zone of the world’s oceans, with the exception of polar regions, suggesting a global distribution for these observations. The two males were observed swimming in the water column, while the female was close to the seabed. All three observations were detected during the morning, raising the question if these organisms use vertical migrations to reach deep-sea waters during the daytime. However, no ROV or submersible dives were conducted at night. Our results show a depth range expansion for observations of this species in the Red Sea. Furthermore, as far as we know, no adults of F. desmarestia have been reported until now in the Red Sea. During the expedition, all three specimens were found at similar depths (350, 400, and 464.5 m depth), with the female being the deepest, thus confirming the eurybathic distribution of this species. The emerging technology is progressively enhancing our understanding of these enigmatic creatures and expanding our knowledge of their fascinating adaptations and ecological roles. In addition to our fieldwork, a literature search was performed to uncover any pre-existing observational records of this species to understand its global distribution and ecological significance.

Abstract Our knowledge of the factors that can influence the stock of organic carbon (OC) that is stored in the soil of seagrass meadows is evolving, and several causal effects have been used to explain the variation of stocks observed at local to national scales. To gain a global‐scale appreciation of the drivers that cause variation in soil OC stocks, we compiled data on published species‐specific traits and OC stocks from monospecific and mixed meadows at multiple geomorphological settings. Species identity was recognized as an influential driver of soil OC stocks, despite their large intraspecific variation. The most important seagrass species traits associated with OC stocks were the number of leaves per seagrass shoot, belowground biomass, leaf lifespan, aboveground biomass, leaf lignin, leaf breaking force and leaf OC plus the coastal geomorphology of the area, particularly for lagoon environments. A revised estimate of the global average soil OC stock to 20 cm depth of 15.4 Mg C ha −1 is lower than previously reported. The largest stocks were still recorded in Mediterranean seagrass meadows. Our results specifically identify Posidonia oceanica from the Mediterranean and, more generally, large and persistent species as key in providing climate regulation services, and as priority species for conservation for this specific ecosystem service.

Abstract Background Isolation of marine microorganisms is fundamental to gather information about their physiology, ecology and genomic content. To date, most of the bacterial isolation efforts have focused on the photic ocean leaving the deep ocean less explored. We have created a marine culture collection of heterotrophic bacteria (MARINHET) using a standard marine medium comprising a total of 1561 bacterial strains, and covering a variety of oceanographic regions from different seasons and years, from 2009 to 2015. Specifically, our marine collection contains isolates from both photic (817) and aphotic layers (744), including the mesopelagic (362) and the bathypelagic (382), from the North Western Mediterranean Sea, the North and South Atlantic Ocean, the Indian, the Pacific, and the Arctic Oceans. We described the taxonomy, the phylogenetic diversity and the biogeography of a fraction of the marine culturable microorganisms to enhance our knowledge about which heterotrophic marine isolates are recurrently retrieved across oceans and along different depths. Results The partial sequencing of the 16S rRNA gene of all isolates revealed that they mainly affiliate with the classes Alphaproteobacteria (35.9%), Gammaproteobacteria (38.6%), and phylum Bacteroidetes (16.5%). In addition, Alteromonas and Erythrobacter genera were found the most common heterotrophic bacteria in the ocean growing in solid agar medium. When comparing all photic, mesopelagic, and bathypelagic isolates sequences retrieved from different stations, 37% of them were 100% identical. This percentage increased up to 59% when mesopelagic and bathypelagic strains were grouped as the aphotic dataset and compared to the photic dataset of isolates, indicating the ubiquity of some bacterial isolates along different ocean depths. Finally, we isolated three strains that represent a new species, and the genome comparison and phenotypic characterization of two of these strains (ISS653 and ISS1889) concluded that they belong to a new species within the genus Mesonia . Conclusions Overall, this study highlights the relevance of culture-dependent studies, with focus on marine isolated bacteria from different oceanographic regions and depths, to provide a more comprehensive view of the culturable marine bacteria as part of the total marine microbial diversity.

Abstract Cavity ring‐down spectroscopy (CRDS) is a highly sensitive laser technique that allows the analysis of isotopic signals and absolute concentration of individual molecular species in small‐volume samples. Here, we describe a protocol to quantify photosynthetic 13 C‐uptake rates of marine phytoplankton by using the CRDS technique ( 13 C‐CRDS‐PP). We validated our method by comparing the 13 C‐PP rates measured between CRDS and isotope ratio mass spectrometry (IRMS) in samples with different carbon content (30–160 μ gC). The comparison revealed that 13 C‐CRDS‐PP rates were highly correlated with those obtained by IRMS (Spearman correlation coefficient, ρ = 0.95, p < 0.0001, n = 15), with a mean difference between the two estimates of ± 0.08 mgC m −3 h −1 . Moreover, the slope of the relationship between CRDS and IRMS results was not significantly different from 1 ( F = 0.03, p = 0.86), and the intercept did not differ from 0 ( F = 1.4, p = 0.24), indicating that there was no bias in the CRDS relative to the IRMS‐based measurements. A separate analysis also showed that despite the difference in volume and carbon content between samples (40 ± 10 μ gC and 160 ± 40 μ gC, respectively), the 13 C‐CRDS‐PP technique provides similar results (Mann–Whitney test, U = 30.5, p = 0.90, n = 8). In addition, 13 C‐CRDS‐PP rates measured along the Red Sea (∼ 176 mgC m −2 d −1 ) agreed with 14 C‐based PP rates previously reported for similar locations. Thus, this study evidenced that the 13 C‐CRDS‐PP method is sensitive enough to quantify carbon fixation rates in oligotrophic regions.

Abstract Animal-attached devices have transformed our understanding of vertebrate ecology. To minimize tag-related harm for these studies, researchers have long advocated that tag masses should not exceed 3% of the animal’s body mass. However, this proposition ignores tag forces generated as a result of animal movement. Using data from collar-attached accelerometers on diverse free-ranging terrestrial animals, we detail a tag-based acceleration method (TbAM) in which we quantify animal athleticism in terms of fractions of animal movement time devoted to different collar-recorded accelerations. The varying accelerations are converted to forces imposed on the animals based on the acceleration and tag mass and allow derivation of defined force limits, including those amounting to 3% of the animal’s mass, for specified fractions of any animal’s active time. We demonstrate how species athleticism is the principal determinant of tag forces, whereas body mass is of little importance. Forces exerted by ‘3%’ tags were mostly equivalent to 4-19% of the animals’ masses during moving, with a maximum of 54% in a hunting cheetah. Cumulative frequency curves of tag acceleration for periods when animals were active, all showed a characteristic sigmoid pattern, which was displaced further to the right as higher acceleration activities accounted for an increasing proportion of any animal’s time. Specifying that tags should exert forces that are less than 3% of the animal’s body mass for 95% of the time led to corrected tag masses constituting between 1.6% and 2.98% of our study animals’ masses, with values depending on animal athleticism. Recognition that animal athleticism affects tag forces of their carriers fundamentally changes how acceptable tag mass limits should be determined by ethics bodies. In order to have a scientifically robust acceptable threshold to limit the forces experienced by an animal carrier, we suggest practitioners derive a similar cumulative acceleration profile for their study species and use a minimum of the 95% limits on the plot (although higher limits may be more appropriate).

We discuss Al, Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn contents in seagrass Posidonia oceanica rhizomes from the Balearic Archipelago for the last 3 decades. Time series of metal concentration in P. oceanica were measured by dating rhizomes using retrospective procedures. The highest concentrations of Al (174.73 μ g g −1 ), Cd (3.56 μ g g −1 ), Cr (1.34 μ g g −1 ), Cu (32.15 μ g g −1 ), Pb (8.51 μ g g −1 ), and Zn (107.14 μ g g −1 ) were measured in meadows located around the largest and most densely populated island (Mallorca Island). There was a general tendency for Ag concentration to decrease with time (up to 80% from 1990 to 2005 in sample from Mallorca Island), which could be attributed to a reduction of the anthropogenic sources. Nickel and Zn concentrations were the unique elements that showed a consistent temporal trend in all samples, increasing their concentrations since year 1996 at all studied stations; this trend matched with the time series of UV‐absorbing aerosols particles in the air (i.e., aerosols index) over the Mediterranean region (r 2 : 0.78, p < 0.001 for Cabrera Island), suggesting that P. oceanica could be an efficient recorder of dust events. A comparison of enrichment factors in rhizomes relative to average crustal material indicates that suspended aerosol is also the most likely source for Cr and Fe to P. oceanica .