Publications

The increase of the temperature in the Red Sea basin due to global warming could have a large negative effect on its marine ecosystem. Consequently, there is a growing interest, from the scientific community and public organizations, in obtaining reliable projections of the Red Sea temperatures throughout the 21 st century. However, the main tool used to do climate projections, the global climate models (GCM), may not be well suited for that relatively small region. In this work we assess the skills of the CMIP5 ensemble of GCMs in reproducing different aspects of the Red Sea 3D temperature variability. The results suggest that some of the GCMs are able to reproduce the present variability at large spatial scales with accuracy comparable to medium and high-resolution hindcasts. In general, the skills of the GCMs are better inside the Red Sea than outside, in the Gulf of Aden. Based on their performance, 8 of the original ensemble of 43 GCMs have been selected to project the temperature evolution of the basin. Bearing in mind the GCM limitations, this can be an useful benchmark once the high resolution projections are available. Those models project an averaged warming at the end of the century (2080–2100) of 3.3 ±> 0.6°C and 1.6 ±> 0.4°C at the surface under the scenarios RCP8.5 and RCP4.5, respectively. In the deeper layers the warming is projected to be smaller, reaching 2.2 ±> 0.5°C and 1.5 ±> 0.3°C at 300 m. The projected warming will largely overcome the natural multidecadal variability, which could induce temporary and moderate decrease of the temperatures but not enough to fully counteract it. We have also estimated how the rise of the mean temperature could modify the characteristics of the marine heatwaves in the region. The results show that the average length of the heatwaves would increase ~15 times and the intensity of the heatwaves ~4 times with respect to the present conditions under the scenario RCP8.5 (10 time and 3.6 times, respectively, under scenario RCP4.5).

Novel aerobic, Gram-negative bacteria with DNA G+C contents below 50 mol% were isolated from the culturable microbiota associated with the Mediterranean seagrass Posidonia oceanica. 16S rRNA gene sequence analyses revealed that they belong to the genus Marinomonas. Strain IVIA-Po-186 is a strain of the species Marinomonas mediterranea, showing 99.77 % 16S rRNA gene sequence similarity with the type strain, MMB-1(T), and sharing all phenotypic characteristics studied. This is the first description of this species forming part of the microbiota of a marine plant. A second strain, designated IVIA-Po-101(T), was closely related to M. mediterranea based on phylogenetic studies. However, it differed in characteristics such as melanin synthesis and tyrosinase, laccase and antimicrobial activities. In addition, strain IVIA-Po-101(T) was auxotrophic and unable to use acetate. IVIA-Po-101(T) shared 97.86 % 16S rRNA gene sequence similarity with M. mediterranea MMB-1(T), but the level of DNA-DNA relatedness between the two strains was only 10.3 %. On the basis of these data, strain IVIA-Po-101(T) is considered to represent a novel species of the genus Marinomonas, for which the name Marinomonas balearica sp. nov. is proposed. The type strain is IVIA-Po-101(T) (=CECT 7378(T) =NCIMB 14432(T)). A third novel strain, IVIA-Po-185(T), was phylogenetically distant from all recognized Marinomonas species. It shared the highest 16S rRNA gene sequence similarity (97.4 %) with the type strain of Marinomonas pontica, but the level of DNA-DNA relatedness between the two strains was only 14.5 %. A differential chemotaxonomic marker of this strain in the genus Marinomonas is the presence of the fatty acid C(17 : 0) cyclo. Strain IVIA-Po-185(T) is thus considered to represent a second novel species of the genus, for which the name Marinomonas pollencensis sp. nov. is proposed. The type strain is IVIA-Po-185(T) (=CECT 7375(T) =NCIMB 14435(T)). An emended description of the genus Marinomonas is given based on the description of these two novel species, as well as other Marinomonas species described after the original description of the genus.

Abstract Seagrass meadows store significant amounts of carbonate (CaCO 3 ) in sediment, contributing to coastal protection but potentially offsetting their effectiveness as carbon sinks. Understanding the accumulation of CaCO 3 and its balance with organic carbon (C org ) in seagrass ecosystems is crucial for developing seagrass-based blue carbon strategies for climate change mitigation. However, CaCO 3 accumulation in seagrass meadows varies significantly across geographic regions, with notable data gaps in the Caribbean and Central America. Here, we sampled 10 seagrass meadows across an extensive island chain in The Bahamas, part of the largest seagrass ecosystem and one of the largest CaCO 3 banks globally, to evaluate CaCO 3 stock, accumulation rate, and its balance with C org sequestration. Seagrass meadows in The Bahamas store 6405–8847 Tg of inorganic carbon (C inorg ) in the upper meter sediment, with an annual accumulation rate of 38.3–52.9 Tg of C inorg , highlighting these meadows as hotspots for CaCO 3 burial. CaCO 3 contributes 67 ± 8% (mean ± standard error) of the sediment accumulation, indicating its important role in seabed elevation. Sediment C inorg showed no significant relationship with C org , with an average C org : C inorg ratio of 0.069 ± 0.002, ∼ 10 times lower than the threshold (C org : C inorg ratio of about 0.63) at which seagrass ecosystem transition from CO 2 sources to sinks. However, the available air–sea gas flux measurement was only 1/5 of the calculated CO 2 emission expected from calcification, suggesting that part of the accumulated CaCO 3 is supported by allochthonous inputs. Furthermore, no perceivable relationship between seagrass density and either CaCO 3 stock or accumulation rate was observed, indicating that seagrass may play a limited role in supporting CaCO 3 production. Further studies on water chemistry, calcification rate, air–sea CO 2 flux, and comparison between seagrass and unvegetated habitats are required to elucidate the carbon budget of this globally significant ecosystem.

DATA REPORT article Front. Mar. Sci., 15 April 2024Sec. Discoveries Volume 11 - 2024 | https://doi.org/10.3389/fmars.2024.1305487

Abstract The role of the ocean as a sink for CO 2 is partially dependent on the downward transport of phytoplankton cells packaged within fast-sinking particles. However, whether such fast-sinking mechanisms deliver fresh organic carbon down to the deep bathypelagic sea and whether this mechanism is prevalent across the ocean requires confirmation. Here we report the ubiquitous presence of healthy photosynthetic cells, dominated by diatoms, down to 4,000 m in the deep dark ocean. Decay experiments with surface phytoplankton suggested that the large proportion (18%) of healthy photosynthetic cells observed, on average, in the dark ocean, requires transport times from a few days to a few weeks, corresponding to sinking rates (124–732 m d −1 ) comparable to those of fast-sinking aggregates and faecal pellets. These results confirm the expectation that fast-sinking mechanisms inject fresh organic carbon into the deep sea and that this is a prevalent process operating across the global oligotrophic ocean.

Pinna nobilis is an endemic bivalve of the Mediterranean Sea whose populations have decreased in the last decades due to human pressure; as consequence, it was declared a protected species in 1992. Despite its conservation status, few genetic studies using mitochondrial markers have been published. We report on the isolation and development of 10 microsatellite loci for the fan mussel, Pinna nobilis. All loci (2 di-nucleotide, 5 tri-nucleotide, 2 tetra-nucleotide and 1 penta-nucleotide) are characterized by high polymorphism levels in 76 individuals tested from two populations in Balearic Islands (Spain, Western Mediterranean Sea). Number of alleles ranged from 4 to 24 and expected heterozygosity ranged from 0.4269 to 0.9400. These microsatellites could be very useful to assess the genetic diversity and connectivity patterns of P. nobilis and to establish new conservation strategies.

[This corrects the article on p. 557 in vol. 5, PMID: 25400625.].

Future ocean acidification (OA) will affect physiological traits of marine species, with calcifying species being particularly vulnerable. As OA entails high energy demands, particularly during the rapid juvenile growth phase, food supply may play a key role in the response of marine organisms to OA. We experimentally evaluated the role of food supply in modulating physiological responses and biomineralization processes in juveniles of the Chilean scallop, Argopecten purpuratus, that were exposed to control (pH ~ 8.0) and low pH (pH ~ 7.6) conditions using three food supply treatments (high, intermediate, and low). We found that pH and food levels had additive effects on the physiological response of the juvenile scallops. Metabolic rates, shell growth, net calcification, and ingestion rates increased significantly at low pH conditions, independent of food. These physiological responses increased significantly in organisms exposed to intermediate and high levels of food supply. Hence, food supply seems to play a major role modulating organismal response by providing the energetic means to bolster the physiological response of OA stress. On the contrary, the relative expression of chitin synthase, a functional molecule for biomineralization, increased significantly in scallops exposed to low food supply and low pH, which resulted in a thicker periostracum enriched with chitin polysaccharides. Under reduced food and low pH conditions, the adaptive organismal response was to trade-off growth for the expression of biomineralization molecules and altering of the organic composition of shell periostracum, suggesting that the future performance of these calcifiers will depend on the trajectories of both OA and food supply. Thus, incorporating a suite of traits and multiple stressors in future studies of the adaptive organismal response may provide key insights on OA impacts on marine calcifiers.