The Humboldt-09 cruise covered a narrow meridional band along the Chilean continental slope (44–23º S). Here we use physical and biochemical data from a long meridional section (4000 km) and three short zonal sections (100 km) to describe the distribution of the different water masses found in this region. Six water masses were identified: Subantarctic Water (SAAW), Summer Subantarctic Water (SSAW), Subtropical Water (STW), Equatorial Subsurface Water (ESSW), Antarctic Intermediate Water (AAIW), and Pacific Deep Water (PDW). For the first time, a novel set of source water mass properties (or water types) is introduced for SSAW, and nutrient and dissolved oxygen water types are proposed for all the water masses. Optimum multiparameter (OMP) analysis was used through an iterative process to obtain a sound definition of the water types that minimizes the residuals of the method. Both the classic OMP and the quasi-extended OMP models reproduced the data rather well. Finally, the spatial distribution of the different water masses was calculated with the quasi-extended OMP, which is not influenced by the respiration of organic matter. The distribution of the different water masses is presented over the meridional and zonal transects and in property-property diagrams. A smooth meridional transition from subantarctic to tropical and equatorial water masses is observed in this area. This transition takes place in surface, central, and intermediate waters over distances of the order of 1000 km. The meridional transition contrasts with the abrupt zonal changes found in the cross-slope direction, which are of comparable magnitude but over distances of the order of 100 km. Both AAIW and SAAW (fresh and well oxygenated) partially mix with the hypoxic ESSW and, therefore, play an important role in the ventilation of the southern part of the oxygen minimum zone.
Macroalgal forests export much of their production, partly supporting food webs and carbon stocks beyond their habitat, but evidence of their contribution in sediment carbon stocks is poor. We test the hypothesis that macroalgae contribute to carbon stocks in arctic marine sediments. We used environmental DNA (eDNA) fingerprinting on a large-scale set of surface sediment samples from Greenland and Svalbard. We evaluated eDNA results by comparing with traditional survey and tracer methods. The eDNA-based survey identified macroalgae in 94 % of the sediment samples covering shallow nearshore areas to 1460 m depth and 350 km offshore, with highest sequence abundance nearshore and with dominance of brown macroalgae. Overall, the eDNA results reflected the potential source communities of macroalgae and eelgrass assessed by traditional surveys, with the most abundant orders being common among different methods. A stable isotope analysis showed a considerable contribution from macroalgae in sediments although with high uncertainty, highlighting eDNA as a great improvement and supplement for documenting macroalgae as a contributor to sediment carbon stocks. Conclusively, we provide evidence for a prevalent contribution of macroalgal forests in arctic surface sediments, nearshore as well as offshore, identifying brown algae as main contributors.
Protecting the ocean has become a major goal of international policy as human activities increasingly endanger the integrity of the ocean ecosystem, often summarized as “ocean health.” By and large, efforts to protect the ocean have failed because, among other things, (1) the underlying socio-ecological pathways have not been properly considered, and (2) the concept of ocean health has been ill defined. Collectively, this prevents an adequate societal response as to how ocean ecosystems and their vital functions for human societies can be protected and restored. We review the confusion surrounding the term “ocean health” and suggest an operational ocean-health framework in line with the concept of strong sustainability. Given the accelerating degeneration of marine ecosystems, the restoration of regional ocean health will be of increasing importance. Our advocated transdisciplinary and multi-actor framework can help to advance the implementation of more active measures to restore ocean health and safeguard human health and well-being.
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 206:97-106 (2000) - doi:10.3354/meps206097 Response of Mediterranean Synechococcus growth and loss rates to experimental nutrient inputs Nona S. R. Agawin*, Carlos M. Duarte, Susana Agustí Instituto Mediterraneo de Estudios Avanzados (CSIC-UIB), C/Miquel Marqués 21, 07190 Esporles, Mallorca, Spain *E-mail: ieanar@clust.uib.es ABSTRACT: The response of Synechococcus sp. growth, primary production and loss rates was examined in a large-scale mesocosm nutrient enrichment experiment in a coastal NW Mediterranean bay community during the summer of 1997. The mesocosm units (33 m3) received N, P and Si at a stochiometric ratio of 20N:7Si:1P, at the normal nutrient loading rate for the site (5 mmol N m-2 d-1), and at 0.5-, 2-, 4-, 8-, and 16-fold the normal nutrient loading input into the bay. Growth and primary production of Synechococcus during the early phase of the experiment increased 2- to 4-fold in the mesocosms receiving ≥4-fold the normal nutrient loading rate compared to those receiving less, providing evidence of nutrient-limited growth of the population in the Mediterranean bay studied during that summer. Synechococcus growth was saturated at approximately 0.25 µM DIN, and was unsustained as nutrient inputs continued, showing growth inhibition at relatively high DIN levels (>8 µM). The response of loss rates of Synechococcus to the experimental nutrient inputs was similar to the growth responses, although the dynamics of Synechococcus population size seemed to be an interplay between growth and loss rates. The population size of Synechococcus increased early by almost 3-fold, indicative of limitation of Synechococcus biomass in the Bay of Blanes during summer. The increase is suggested to result from the lag between Synechococcus growth and loss rate responses during the early phase of the experiment when growth rates exceeded loss rates, resulting in an increase in net production with increased loading. The increase of Synechococcus population size towards the end of the experiment was a result of decreased grazing pressure on Synechococcus, despite the low growth rates of Synechococcus at the high nutrient inputs. Grazing of Synechococcus is suggested to be the main loss process (>50% of calculated loss rates) except towards the end of the experiment when grazing was only 13% of the calculated losses. KEY WORDS: Synechococcus sp. growth and loss rates · Nutrient inputs · Mediterranean coastal area · Mesocosm experiments Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 206. Online publication date: November 03, 2000 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2000 Inter-Research.
This report, produced by some of the world's leading scientists, finds that the most crucial, climate-combating coastal ecosystems cover less than 0.5% of the sea bed. But they are disappearing faster than anything on land and much may be lost in a couple of decades. These areas, covering features such as mangroves, salt marshes and seagrasses, are responsible for capturing and storing up to some 70% of the carbon permanently stored in the marine realm.
