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 158:131-138 (1997) - doi:10.3354/meps158131 Dynamics of a landscape mosaic: size and age distributions, growth and demography of seagrass Cymodocea nodosa patches B. Vidondo1,*, C. M. Duarte2, A. L. Middelboe3, K. Stefansen3, T. Lützen3, S. L. Nielsen3 1Limnologisches Institut, Universität Konstanz, Mainaustrasse 212, D-78457 Konstanz, Germany 2Centro de Estudios Avanzados de Blanes - CSIC, Camí de Santa Bárbara s/n, E-17300 Blanes, Girona, Spain 3Department of Life Sciences and Chemistry, Roskilde University, DK-4000 Roskilde, Denmark *E-mail: beatriz.vidondo@uni-konstanz.de The patch dynamics (recruitment, growth and mortality) of seagrass Cymodocea nodosa were examined at the landscape scale (i.e. the scale at which disturbances occur) by means of 3-dimensional (X, Y dimensions and depth) mapping of shoot internal density and age structure within the basic units (patches) forming the landscape. Highly skewed patch size and age distributions indicated a high exponential patch mortality rate (m = 0.82 ± 0.07 yr-1) and a slightly higher exponential patch recruitment rate (1.04 yr-1) that ensures the maintenance and fast turnover of this population of patches. Patch growth (i.e. increase in number of shoots per patch) proceeded at an exponential growth rate of 2.28 ± 0.14 yr-1, indicating a doubling time of 111 d for the shoot population within each patch. Moreover, average patch growth rate accelerates with increasing patch size and age. This self-acceleration of patch growth means that this seagrass species has a remarkable potential for rapid space occupation due to its intense clonal growth. The results obtained emphasize the power of a landscape approach for describing the intense dynamics of colonising seagrass populations. Seagrass patch dynamics · Landscape scale · Three-dimensional mapping · Size and age distributions · Pareto distribution Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 158. Publication date: November 17, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.
Drawing from the growing database of complex three-dimensional RNA structures, a systematic method has been developed for classifying and analyzing the variety of conformations adopted by nucleic acids. This method is based on the development of a reduced representation for nucleic acid backbone conformation, simplifying the formidable eight-dimensional problem that has long complicated nucleic acid conformational analysis. Two pseudotorsion angles (eta and theta) have been defined, based on the selection of two appropriate pivot points along the RNA backbone, P and C4'. These pseudotorsions, together with a complete library of conventional torsion angles, can be calculated for any RNA structure or all-atom model using a new program called AMIGOS. Having computed eta and theta pseudotorsions for each position on an RNA molecule, they can be represented on a two-dimensional plot similar to the phi-phi plots that have traditionally been used for protein conformational analysis. Like a Ramachandran plot, clusters of residues appear at discrete regions on an eta-theta plot. Nucleotides within these clusters share conformational properties, often belonging to the same type of structural motif such as A-platforms, sheared tandem purine-purine pairs and GNRA tetraloops. An eta-theta plot provides a two-dimensional representation of the conformational properties of an entire RNA molecule, facilitating rapid analysis of structural features. In addition to the utility of eta-theta plots for intuitive visualization of conformational space, the pseudotorsional convention described here should significantly simplify approaches to macromolecular modeling of RNA structure.
Concern over the deterioration of the oceans has generated a demand for a system able to assess ocean health globally, and approaches to assess ocean health globally and an observing system delivering the data to support this assessment are now being developed. In parallel with public health systems, a system to assess ocean health should evaluate the occurrence and severity of a set of syndromes of concern through a series of indicators composed from a parsimonious set of ecosystem essential ocean variables delivered by a coherent and robust observing system. The development of such approach for the global assessment of ocean health will help inform policies acting upon the drivers causing ocean syndromes and help ensure a healthy ocean for all.
Abstract The introduction and establishment of exotic species often result in significant changes in recipient communities and their associated ecosystem services. However, usually the magnitude and direction of the changes are difficult to quantify because there is no pre‐introduction data. Specifically, little is known about the effect of marine exotic macrophytes on organic carbon sequestration and storage. Here, we combine dating sediment cores ( 210 Pb) with sediment eDNA fingerprinting to reconstruct the chronology of pre‐ and post‐arrival of the Red Sea seagrass Halophila stipulacea spreading into the Eastern Mediterranean native seagrass meadows. We then compare sediment organic carbon storage and burial rates before and after the arrival of H. stipulacea and between exotic ( H. stipulacea) and native ( C. nodosa and P. oceanica ) meadows since the time of arrival following a Before‐After‐Control‐Impact (BACI) approach. This analysis revealed that H. stipulacea arrived at the areas of study in Limassol (Cyprus) and West Crete (Greece) in the 1930s and 1970s, respectively. Average sediment organic carbon after the arrival of H. stipulacea to the sites increased in the exotic meadows twofold, from 8.4 ± 2.5 g C org m −2 year −1 to 14.7 ± 3.6 g C org m −2 year −1 , and, since then, burial rates in the exotic seagrass meadows were higher than in native ones of Cymodocea nodosa and Posidonia oceanica . Carbon isotopic data indicated a 50% increase of the seagrass contribution to the total sediment C org pool since the arrival of H. stipulacea . Our results demonstrate that the invasion of H. stipulacea may play an important role in maintaining the blue carbon sink capacity in the future warmer Mediterranean Sea, by developing new carbon sinks in bare sediments and colonizing areas previously occupied by the colder thermal affinity P. oceanica .
AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 60:175-191 (2010) - DOI: https://doi.org/10.3354/ame01421 Phyto- and bacterioplankton abundance and viability and their relationship with phosphorus across the Mediterranean Sea Sebastien Lasternas*, Susana Agustí, Carlos M. Duarte Department of Global Change Research, IMEDEA (CSIC-UIB), Instituto Mediterráneo de Estudios Avanzados, C/ Miquel Marqués 21, 07190 Esporles, Balearic Islands, Spain *Email: sebastien.lasternas@uib.es ABSTRACT: In a synoptic cruise performed during early summer, the composition and viability of pelagic communities of the Mediterranean Sea were studied across the different sub-basins and straits in relation to nutrient regimes and hydrological conditions. The picoplankton fraction dominated the pelagic community across the study region. Bacterioplankton was the most abundant (mean ± SE = 7.73 ± 0.39 × 105 cells ml–1) component of the plankton, reaching the highest abundance in the Marmara and Black Seas, and its abundance was positively related to phosphate concentration. Synechococcus spp. was abundant (3.70 ± 0.87 × 104 cells ml–1), and was most frequent in the surface layers of the West Basin and the Black Sea. Two populations of Synechococcus (Synechococcus sp. 1 and sp. 2) were identified, with contrasting distributions along the Mediterranean Sea. Prochlorococcus spp. was also present (3.77 ± 0.36 × 104 cells ml–1) and was associated with the deep chlorophyll maximum. Diatoms dominated the microphytoplankton except in the Black Sea, where dinoflagellates and flagellates became predominant. The percentage of living cells (%LC) of Synechococcus sp. 1 displayed a negative relationship with temperature, whereas that of Synechococcus sp. 2 increased with increasing temperature. Prochlorococcus spp. %LC was negatively related to inorganic nitrogen, but positively related to salinity. The viability of heterotrophic bacteria, dinoflagellates and Synechococcus sp. 1 increased with increasing phosphate, underlining the important role of phosphorus in the Mediterranean Sea. Our in situ observations relating survival to environmental forcing allowed the identification of competition and niche segregation within the coexisting populations. KEY WORDS: Phytoplankton · Bacterioplankton · Viability · Phosphorus · Mediterranean Sea Full text in pdf format PreviousNextCite this article as: Lasternas S, Agustí S, Duarte CM (2010) Phyto- and bacterioplankton abundance and viability and their relationship with phosphorus across the Mediterranean Sea. Aquat Microb Ecol 60:175-191. https://doi.org/10.3354/ame01421Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 60, No. 2. Online publication date: June 07, 2010 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2010 Inter-Research.
Incubation (in vitro) and incubation-free (in situ) methods, each with their own advantages and limitations, have been used to derive estimates of net community metabolism in the oligotrophic subtropical gyres of the open ocean. The hypothesis that heterotrophic communities are prevalent in most oligotrophic regions is consistent with the available evidence and supported by scaling relationships showing that heterotrophic communities prevail in areas of low gross primary production, low chlorophyll a, and warm water, conditions found in the oligotrophic ocean. Heterotrophic metabolism can prevail where heterotrophic activity is subsidized by organic carbon inputs from the continental shelf or the atmosphere and from nonphotosynthetic autotrophic and mixotrophic metabolic pathways. The growth of the oli-gotrophic regions is likely to be tilting the metabolic balance of the ocean toward a greater prevalence of heterotrophic communities.
