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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.
Triplicate samples of Posidonia oceanica were randomly collected at 26 locations along the Balearic Islands (Mediterranean Sea) during the summers of 2005 and 2006. Roots were subjected to a surface-sterilization protocol prior to nucleic acid extraction. The nitrogenase was amplified by PCR using degenerate primers for nifH gene sequences. The PCR products were checked by electrophoresis on 1.5% agarose gels. The youngest leaf (free of epiphytes) of three shoots and three young rhizome fragments were dried at 60oC for 48 h and ground to a fine powder. All isotopic analyses were measured using standard elemental analyzer isotope ratio mass spectrometer (EA-IRMS) procedures. Isotopic ratios (R) are reported in the standard delta notation (‰), deltasample=1000((Rsample/Rstandard)-1), where R = 15N/14N. These results are presented with respect to the International standard of atmospheric nitrogen (AIR, N2). Analytical reproducibility of the reported delta values, based on sample replicates, was better than ±0.2‰.
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 146:155-161 (1997) - doi:10.3354/meps146155 Spatial and temporal variations in nutrient limitation of seagrass Posidonia oceanica growth in the NW Mediterranean Alcoverro T, Romero J, Duarte CM, López NI The extent and seasonality of nutrient limitation of Posidonia oceanica (L.) Delile in the Costa Brava littoral (NW Mediterranean) in 5 meadows was investigated by means of repeated nutrient additions along a year cycle. Nutrient additions had a modest effect on leaf growth. The response to fertilization varied considerably among meadows, with those meadows consistently maintaining low (300 µM dissolved inorganic nitrogen and 9 µM soluble reactive phosphorus) dissolved inorganic nutrient concentrations in sediment pore waters showing the greatest response to fertilization. The seasonality of the growth response to fertilization was consistent with calculated nutrient deficiencies, which were greatest in late spring and summer. Nutrient deficiency was alleviated in the fall, partially due to reduced growth, but also to nutrient reclamation from old leaves, which represented 20% and 18% of the annual nitrogen and phosphorus incorporation, respectively. The relative deficiency of nitrogen and phosphorus differed among sites, with the highest response found in P-deficient meadows. Nutrient limitation of P. oceanica meadows was greatest in late spring and summer, but differed greatly in magnitude and nature (nitrogen vs phosphorus) depending on local nutrient regimes. Nitrogen · Phosphorus · Growth · Seasonality · Retranslocation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 146. Publication date: January 30, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.
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 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.
The proposed threshold planktonic gross primary production (GPP) value for O2 of 2.05 mmol m−3 d−1 separating net heterotrophic from net autotrophic communities in the Southern Ocean was tested experimentally using large mesocosms (20 m3). A set of eight mesocosms was moored in Johnson's Dock (62°39.576'S, 60°22.408'W, Livingston Island, Antarctica) and a gradient of GPP was experimentally generated by imposing four light levels (100%, 50%, 25%, and 10%) in the presence or absence of nutrient additions (0.1 mol NH4Cl, 0.1 mol of F6Na2Si, and 0.01 mol KH2PO4 per mesocosm per day). The experimental treatments resulted in a broad range of chlorophyll a (Chl a) (0.31–93.5 mg m−3) and GPP (O2, 0.17–16.7 mmol m−3 d−1). Community respiration (R) increased with increasing GPP, but not proportionately, resulting in a range of P :R ratios ranging from 0.12 in intensely shaded communities to 1.3 in those receiving high irradiance and nutrient additions, with the compensation irradiance for community metabolism (i.e., percentage irradiance at P:R = 1) being reached at 83% of the ambient irradiance. The experimental estimate of the threshold GPP for metabolic balance of the community investigated (i.e., P :R = 1) was 2.2 (SE ± 0.016) mmol O2 m−3 d−1, thereby validating the estimate of 2.05 mmol O2 m−3 d−1 derived in the past from comparative analyses of planktonic metabolism across the Southern Ocean. The validation of this threshold suggests that net heterotrophic planktonic communities may be more prevalent in the Southern Ocean than hitherto believed.
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.
