Posidonia oceanica , the dominant seagrass species in the Mediterranean, appears to be experiencing widespread loss. Efforts to conserve Posidonia oceanica are increasing, as reflected in the increase in the number of marine protected areas in the Mediterranean. However, the effectiveness of these measures to conserve seagrass meadows is unknown. In this study, the present status of the Posidonia oceanica meadows in the Cabrera National Park (Mediterranean), the only marine national park in Spain, was assessed, and the effectiveness of the conservation measures adopted was tested. This was done by reconstruction of past and present growth, quantification of the demographic status of the established meadows, and quantification of patch formation and growth rates in areas where recolonization is occurring. The meadows extended from 1–43 m deep at Santa Maria bay and from 1–33 m at Es Port. Leaf production rate of the stands examined ranged between 6.5 and 7.8 leaves shoot −1 yr −1 , with higher rates in Santa Maria than in Es Port. Vertical rhizomes elongated at rates ranging from 5.39–10.12 mm yr −1 , annual vertical growth in Santa Maria stands being larger than that in the stands developing at Es Port. Horizontal rhizomes elongated slowly (from 2.6–6.1 cm yr −1 ), and branching was sparse (<0.25 branches yr −1 axis −1 ), with maximum elongation and branching rates in areas where patches were actively colonizing. Flowering was a rare event in all the stands (<0.015 flowers shoot −1 yr −1 ). Patch formation and patch growth rates in active colonizing areas were slow, but they increased after implementation of mooring regulations in the Park. Similarly, the leaf production tended to increase, and vertical rhizome growth to decrease, in both bays following the onset of regulation measures. However, the decrease in vertical growth detected was greater at Santa Maria, where access is prohibited to visitors, than at Es Port, where boats are allowed to moor, attached to permanent weights. Shoot mortality rate was generally low (mean 0.10 ± 0.02 ln units yr −1 ) but exceeded the recruitment rate (<0.009 and 0.17 ln units yr −1 ) in 55% of the meadows examined, indicative of negative net population growth rates. Regulation of mooring activities has improved the status of the P. oceanica meadows at Cabrera National Park. The demographic analysis, however, indicated that while P. oceanica meadows at Santa Maria are in good shape, those at Es Port seem to be compromised. The observed differences in meadow status reflect the large differences in circulation inside the bays (water residence time at Santa Maria = 4 days, water residence time at Es Port = 11 days) and the anthropogenic pressure both bays support.
CRISPR-Cas systems have revolutionized modern biology. Most CRISPR-Cas systems in use for biotechnological applications derive from cultivated bacteria, but evidence suggests that environmental microbiomes harbor a large untapped diversity of these systems. Yet, our understanding of which environmental and biological factors drive the prevalence of CRISPR-Cas systems in the oceans remains limited. A search for CRISPR-Cas systems was conducted among 176 globally-distributed marine microbial metagenomes from the Malaspina expedition, which sampled both free-living and particle-attached microbiomes with emphasis on the deep ocean. We show that CRISPR-Cas systems are proportionally more abundant among microbiomes from the deep ocean than in the photic layers and among free-living microbes compared to those attached to particles, reflecting the higher concentrations of archaea and their viruses in these habitats. We identified 1,146 CRISPR-cas loci, some of which displayed unique loci architectures. From these loci, a total of 48 Cas9 proteins were identified, many of which are potentially novel. These discoveries expand the scope of CRISPR-Cas diversity and point at the deep-sea as a rich reservoir of these resources, which helps guide future bioprospecting efforts.
The effectiveness, feasibility, duration of effects, co-benefits, disbenefits, cost effectiveness and governability of four ocean-based negative emissions technologies (NETs) are assessed in comparison to eight other ocean-based measures. Their role in revising UNFCCC Parties' future Nationally Determined Contributions is discussed in the broad context of ocean-based actions for both mitigation and ecological adaptation. All measures are clustered in three policy-relevant categories (Decisive, Low Regret, Concept Stage). None of the ocean-based NETs assessed are identified as Decisive at this stage. One is Low Regret ( Restoring and increasing coastal vegetation ), and three are at Concept Stage, one with low to moderate potential disbenefits ( Marine bioenergy with carbon capture and storage ) and two with potentially high disbenefits ( Enhancing open-ocean productivity and Enhancing weathering and alkalinization ). Ocean-based NETs are uncertain but potentially highly effective. They have high priority for research and development.
The association between corals and photosynthetic dinoflagellates (Symbiodinium spp.) is the key to the success of reef ecosystems in highly oligotrophic environments, but it is also their Achilles' heel due to its vulnerability to local stressors and the effects of climate change. Research during the last two decades has shaped a view that coral host-Symbiodinium pairings are diverse, but largely exclusive. Deep sequencing has now revealed the existence of a rare diversity of cryptic Symbiodinium assemblages within the coral holobiont, in addition to one or a few abundant algal members. While the contribution of the most abundant resident Symbiodinium species to coral physiology is widely recognized, the significance of the rare and low abundant background Symbiodinium remains a matter of debate. In this study, we assessed how coral-Symbiodinium communities assemble and how rare and abundant components together constitute the Symbiodinium community by analyzing 892 coral samples comprising >110 000 unique Symbiodinium ITS2 marker gene sequences. Using network modeling, we show that host-Symbiodinium communities assemble in non-random 'clusters' of abundant and rare symbionts. Symbiodinium community structure follows the same principles as bacterial communities, for which the functional significance of rare members (the 'rare bacterial biosphere') has long been recognized. Importantly, the inclusion of rare Symbiodinium taxa in robustness analyses revealed a significant contribution to the stability of the host-symbiont community overall. As such, it highlights the potential functions rare symbionts may provide to environmental resilience of the coral holobiont.
Examination of latitudinal patterns in species richness, size, and distributional range of East Atlantic fish, based on a compilation of data encompassing the full latitudinal and depth distribution of 1746 East Atlantic fish species, showed that species richness declined towards higher latitudes at a rate of c 1 % of the number of species present, in five‐degree bands, for each degree of latitude for both teleosts and elasmobranchs, regardless of habitat However, the latitudinal patterns in maximum fish size and latitudinal range differed between teleosts and elasmobranchs, and changed with habitat No clear evidence was obtained that the latitudinal range occupied increased with latitude, indicating that Rapoport's rule does not apply to E Atlantic fishes Rather, the latitudinal patterns in species richness, size, and distributional range of benthic Atlantic fish were depth‐dependent, because species richness, average maximum size, and the average latitudinal range increased with depth and declined with latitude The importance of accounting for this depth‐latitude covariation in the distribution of marine fish demonstrated here, together with recent evidence obtained for deep‐sea benthic macrofauna, points to depth and latitude as the main factors in the distribution of marine animals
The rapidly expanding scientific knowledge on seagrasses has led to a growing awareness that seagrasses are a valuable coastal resource. Where seagrasses abound, humans benefit directly and indirectly from the presence of this marine vegetation. At the same time, it has also become evident that seagrasses are a vulnerable resource, easily lost in coastal areas facing environmental changes. Declines of seagrasses are reported world-wide, and in many cases anthropogenic factors are suspected to be responsible for these declines. In this chapter the relations between seagrasses and humans are addressed. Particular attention will be given to the various stresses on seagrasses resulting from human activities. Knowledge of the processes that lead to seagrass decline is obviously the key to remedial measures targeting the re-establishment or protection of seagrass systems.
Defining biogeographic provinces to understand the history and evolution of communities associated with a given kind of ecosystem is challenging and usually requires a priori assumptions to be made. We applied network theory, a holistic and exploratory method, to the most complete database of faunal distribution available on oceanic hydrothermal vents, environments which support fragmented and unstable ecosystems, to infer the processes driving their worldwide biogeography. Besides the identification of robust provinces, the network topology allowed us to identify preferential pathways that had hitherto been overlooked. These pathways are consistent with the previously proposed hypothesis of a role of plate tectonics in the biogeographical history of hydrothermal vent communities. A possible ancestral position of the Western Pacific is also suggested for the first time. Finally, this work provides an innovative example of the potential of network tools to unravel the biogeographic history of faunal assemblages and to supply comprehensive information for the conservation and management of biodiversity.
Abstract. The variation of surface partial pressure of CO2 (pCO2), pH, salinity and dissolved organic carbon (DOC) in 12 coastal Brazilian lakes was examined following periods of contrasting rainfall. It was tested the hypothesis of a positive relationship of rainfall and the associated transport of terrestrial carbon with pCO2 in tropical lakes. High rainfall was followed by a large, almost 10 fold increase in pCO2 and a one unit decrease in pH in the lakes, whereas no consistent changes in DOC were observed. CO2 emissions to the atmosphere from the Brazilian coastal lakes studied here were enhanced, on average, almost 10 fold, from 28.5±6.0 mmol m−2 d−1 in drier periods to 245.3.1±51.5 mmol m−2 d−1 following heavy rain. Hence, precipitation and subsequent ventilation of groundwater CO2 in lakes might provide an important conduit to deliver CO2 resulting from soil respiration to the atmosphere.
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Abstract Like most species of mangrove trees of the genus Avicennia , A. alba is widely distributed among tropical and subtropical coasts around the world. Mangroves play an essential role in ecosystem dynamics but are reported to be regressing as human pressure increases on coastal zones. Hypervariable genetic markers are useful for population genetics studies, to estimate the level of impact and the populations potential for recovery. Microsatellite markers for A. alba were obtained by screening a partial genomic library enriched for microsatellite dinucleotide repeats. Among 20 primer pairs defined, six amplified polymorphic microsatellites with a satisfying level of variability.
The air‐sea CO 2 gradient at the subtropical NE Atlantic was strongly dependent on the metabolism of the planktonic community within the top cms, but independent of that of the communities deeper in the water column. Gross primary production (GPP) and community respiration (R) of the planktonic community within the top cms exceeded those of the communities deeper in the water column by >10‐fold and >7 fold, respectively. Net autotrophic metabolism (GPP > R) at the top cms of the water column in some stations drove CO 2 uptake by creating a CO 2 deficit at the ocean surface, while net heterotrophic metabolism (GPP < R) at the top cms of the water column in other stations resulted in strong CO 2 supersaturation, driving CO 2 emissions. These results suggest a strong control of the air‐sea p CO 2 anomaly by intense biological processes.
Abstract. The metabolism of the Arctic Ocean is marked by extreme pronounced seasonality and spatial heterogeneity associated with light conditions, ice cover, water masses and nutrient availability. Here we report the marine planktonic metabolic rates (Net Community Production, Gross Primary Production and Community Respiration) along three different seasons of the year for a total of eight cruises along the western sector of the European Arctic (Fram Strait – Svalbard region) in the Arctic Ocean margin: one at the end of 2006 (fall/winter), two in 2007 (early spring and summer), two in 2008 (early spring and summer), one in 2009 (late spring–early summer) and one in 2010 (spring). The results show that metabolisms of the western sector of the European Arctic varies throughout the year, depending mostly on the stage of bloom, which is mainly determined by availability of light and nutrients. Here we report metabolic rates for the different periods, including the spring bloom, summer and the dark period, increasing considerably the empirical basis on metabolic rates in the Artic Ocean, and especially in the European Arctic corridor. We also report a rough annual metabolic balance for this area of the Arctic Ocean, resulting in a Net Community Production of 108 g C m−2 yr−1.
Abstract. Diatoms are generally the dominant contributors to the Arctic Ocean spring bloom, which is a key event in regional food webs in terms of capacity for secondary production and organic matter export. Dissolved silicic acid is an obligate nutrient for diatoms and has been declining in the European Arctic. The lack of regional silicon cycling information precludes understanding the consequences of such changes for diatom productivity during the Arctic spring bloom. This study communicates the results from a cruise in the European Arctic around Svalbard reporting the first concurrent data on biogenic silica production and export, diatom cellular export, the degree of kinetic limitation by ambient silicic acid, and diatom contribution to primary production. Regional biogenic silica production rates were significantly lower than those achievable in the Southern Ocean and silicic acid concentration limited the biogenic silica production rate in 95 % of samples. Compared to diatoms in the Atlantic subtropical gyre, regional diatoms are less adapted for silicic acid uptake at low substrate, and at some stations during the present study, silicon limitation may have been intense enough to limit diatom growth. Thus, silicic acid can play a critical role in diatom spring bloom dynamics. Diatom contribution to primary production was variable, ranging from
