Abstract. The concentration of dissolved organic carbon (DOC) in groundwater emanating as spring discharge at several locations in Florida, USA and the net increase in DOC in the downstream receiving waters were measured as part of a larger investigation of carbon dynamics in flowing waters. Springs with high discharge (>2.8 m3 s−1) were found to be the most organic-poor natural waters yet reported (13 ± 1.6 μmol C L−1), while springs with lesser discharge exhibited somewhat higher DOC concentrations (values ranging from 30 to 77 μmol C L−1). DOC concentrations increased rapidly downstream from the point of spring discharge, with the calculated net areal input rate of DOC ranging from 0.04 to 1.64 mol C m−2 d−1 across springs. Rates of DOC increase were generally greater in those springs with high discharge rates. These input rates compare favorably with values reported for gross primary production in these macrophyte-dominated spring systems, assuming that 17% of macrophyte primary production is lost, on average, as DOC. The measures reported here are possible only because of the remarkably low DOC levels in the up-surging groundwaters and the short residency times of the water in the spring-runs themselves.
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 159:29-36 (1997) - doi:10.3354/meps159029 Rates of changes in organic matter and nutrient stocks during seagrass Cymodoceanodosa colonization and stand development Morten F. Pedersen1,*, Carlos M. Duarte2, Just Cebrián3 1Department of Life Sciences and Chemistry 17.2, University of Roskilde, Box 260, DK-4000 Roskilde, Denmark 2Centre d'Estudis Avançats de Blanes, C.S.I.C., Cámi de Santa Bárbara s/n, E-17300 Blanes, Girona, Spain 3Boston University Marine Program (Marine Biological Laboratory), Woods Hole, Massachusetts 02543, USA *E-mail: mfp@virgil.ruc.dk The rates of changes in stocks of organic matter and major nutrients (N and P) during colonization and development of seagrass Cymodocea nodosa biomass in a semi-closed estuary, Alfacs Bay, Spain, were studied. The non-vegetated sediments of Alfacs Bay contain large reserves of N and P, but most of these nutrients are not readily available for plant growth as they are tied up in organic matter or mineral fractions within the sediment. Seagrass biomass per unit area increased linearly during the first 5 yr after colonization although the very low tissue concentrations of P in leaves of C. nodosa suggested P limitation. Development of plant biomass was accompanied by a net accumulation of N at a rate of 3.6 g N m-2 yr-1. Half of this increase was caused by the build up of plant-bound N in living and dead biomass, while the other half was accounted for by accumulation in other N fractions. P accumulated as plant-bound P, but this fraction constituted less than 1% of the total P pool. Accumulation of plant-bound P was of the same magnitude as depletion of other P fractions, leaving the pool of total P unaffected by plant development. These results suggest that colonization and development C. nodosa in Alfacs Bay facilitate capture and accumulation of external N within the stands, while P may be mobilized from mineral-bound P reserves within the sediments. Nutrient accumulation · Phosphorus · Nitrogen · Seagrasses · Sediments · Estuaries Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 159. Publication date: November 29, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.
Une communaute de picophytoplancton dominee par Synechoccoccus sp., presente pendant toute l'annee dans la Baie de Palma, a montre une forte dynamique et des changements le long de la baie observes a l'echelle temporelle d'une semaine. Les populations de pico-phytoplankton ont montre une variation saisonniere importante. Synechococcus sp. offre la plus grande abondance en ete, avec un maximum a la mi-aout. Prochlorococcus sp. presente 3 pics en hiver, au printemps et en ete, le premier etant le plus important. L'abondance des picoeucariotes presente des variations saisonnieres, avec la plus grande concentration de cellules a la mi-avril. Au dela de ces differences en quantite de cellules, les trois groupes phytoplanctoniques offrent des patrons similaires du taux de survie, avec des maxima a la fin de l'hiver et au debut de l'ete, correspondant aux deux pics les plus eleves de concentration en substances nutritives dans la baie. Similairement, le taux plus bas de cellules vivantes, indicatif d'une forte mortalite du pico-phytoplancton, est observe a la fin du printemps, quand la concentration en substances nutritives chute fortement. L'augmentation moderee de l'abondance des cellules suit la haute viabilite de la fin de l'hiver, ce qui indique que des facteurs autres que la presence de substances nutritives controlent les populations de pico-phytoplancton. Malgre la reduction de la mortalite des cellules de pico-phytoplancton au debut de l'ete, seul Synechococcus sp. developpe un bloom important, ce qui indique que les conditions estivales lui sont plus favorables qu'aux autres groupes. La viabilite des cellules permet d'elucider le role des pertes - tensions dans le controle de la dynamique des populations du picoplancton dans la Baie de Palma.
Abstract 保护海洋生物的养护措施已经初见成效。通过开展这些 行动，我们得以遏制物种数量的下降趋势，修复已经退 化的海洋生态系统。但要普遍恢复海洋健康，我们必须 更加积极地治理污染, 防止过度捕捞并抵御气候变化带 来的影响。
All seagrasses are rhizomatous plants that grow by reiteration of a limited set of modules.Their past growth history can therefore be reconstructed from the scars left by abscised leaves and flowers on the long-lived rhizomes or the seasonal slgnals Imprinted in the frequency and size of their modules.We provide here the basic foundations and assumptions of these reconstruction techniques and the calculations involved in their application.We then show their reliability and potential to quantlfy an array of ecological processes, such as plant demography, leaf and rhlzome production, flowering ~ntensity, and seagrass responses to anthropogenic perturbations, based on our recent studies of Mediterranean, Caribbean and Indo-Pacific seagrass species.Reconstruction techniques have also proven useful in demonstrating the role of seagrasses as tracers of sedlment movement over seagrass beds and the rates of colonisation and expansion of seagrass patches.These reconstruction techniques should provide a powerful tool to improve our knowledge of seagrass species and populations from remote areas based on a single or just a few visits This should, therefore, allow us to sample many seagrass meadows using limited resources, thus generating a strong foundation for the study of comparatlve seagrass ecology and testing of theories previously applied to terrestrial plant populations.
