Abstract. One of the major features of the coastal zone is that part of its sea floor receives a significant amount of sunlight and can therefore sustain benthic primary production by seagrasses, macroalgae, microphytobenthos and corals. However, the contribution of benthic communities to the primary production of the global coastal ocean is not known, partly because the surface area where benthic primary production can proceed is poorly quantified. Here, we use a new analysis of satellite (SeaWiFS) data collected between 1998 and 2003 to estimate, for the first time at a nearly global scale, the irradiance reaching the bottom of the coastal ocean. The following cumulative functions provide the percentage of the surface (S) of the coastal zone receiving an irradiance greater than Ez (in mol photons m−2 d−1): SNon-polar = 29.61 − 17.92 log10(Ez) + 0.72 log102(Ez) + 0.90 log103(Ez) SArctic = 15.99 − 13.56 log10(Ez) + 1.49 log102(Ez) + 0.70 log103(Ez) Data on the constraint of light availability on the major benthic primary producers and net community production are reviewed. Some photosynthetic organisms can grow deeper than the nominal bottom limit of the coastal ocean (200 m). The minimum irradiance required varies from 0.4 to 5.1 mol photons m−2 d−1 depending on the group considered. The daily compensation irradiance of benthic communities ranges from 0.24 to 4.4 mol photons m−2 d−1. Data on benthic irradiance and light requirements are combined to estimate the surface area of the coastal ocean where (1) light does not limit the distribution of primary producers and (2) net community production (NCP, the balance between gross primary production and community respiration) is positive. Positive benthic NCP can occur over 33% of the global shelf area. The limitations of this approach, related to the spatial resolution of the satellite data, the parameterization used to convert reflectance data to irradiance, the lack of global information on the benthic nepheloid layer, and the relatively limited biological information available, are discussed.
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 197:231-240 (2000) - doi:10.3354/meps197231 An experimental test of the occurrence of competitive interactions among SE Asian seagrasses Carlos M. Duarte1,*, Jorge Terrados1, Nona S. R. Agawin1, Miguel D. Fortes2 1Instituto Mediterráneo de Estudios Avanzados (CSIC-UIB), c/Miquel Marqués 21, 07190 Esporles (Mallorca), Spain 2Marine Science Institute, University of the Philippines, Diliman, Quezon City 1101, Philippines *E-mail: ieacdq@clust.uib.es ABSTRACT: The occurrence of competitive interactions among the seagrass species present in a multispecific SE Asian seagrass meadow was tested by the cumulative removal of shoots of an increasing number of seagrass species from the meadow in order of decreasing and increasing resource requirements for plant growth. The removal of shoots of the dominant species Thalassia hemprichii had very few effects on shoot size, shoot density and leaf area index of the extant seagrass species. The shoot density of Enhalus acoroides decreased when T. hemprichii shoots were removed, but that of Syringodium isoetifolium increased when the shoots of all the species with higher resource requirements than itself were removed from the experimental plots. The size of Halophila ovalis shoots decreased by 30% when both T. hemprichii and E. acoroides shoots were removed from the plots. The shoot density of T. hemprichii increased only when the shoots of all the accompanying species were removed from the plots. The results show that species interactions in this multispecific seagrass meadow are asymmetric. The elucidation of the nature of the interactions among seagrass species provides a key to understanding the maintenance of the high biodiversity and production that characterizes pristine SE Asian coastal ecosystems. KEY WORDS: Interspecific competition · Tropical seagrasses · SE Asia Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 197. Publication date: May 12, 2000 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 2000 Inter-Research.
The air‐sea exchange of organic carbon (OC) remains largely unexplored, except for few organic compounds comprising a small fraction of the total aerosol and gaseous OC in the atmosphere. Observations of high atmospheric concentrations and diffusive air‐sea exchanges for such individual organic compounds, suggest that air‐sea exchange of total OC may contribute significantly to the oceanic carbon budget. Here we quantify the atmosphere‐ocean exchanges of total OC in the NE Subtropical Atlantic. Average net gaseous diffusive air‐water fluxes averaged –31 and –25 mmol C m −2 d −1 for the spring and fall, respectively, exceeding measured OC inputs by dry aerosol deposition (FDD OC , −0.98 mmol C m −2 d −1 ) and net CO 2 exchange (F CO2 , −6.3 mmol C m −2 d −1 ). These fluxes are important to understand the regional carbon budget of the NE Subtropical Atlantic, and depict the atmosphere as a major dynamic vector for OC exchange with the ocean.
AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 12:71-83 (1997) - doi:10.3354/ame012071 Dynamics of ciliate abundance, biomass and community composition in an oligotrophic coastal environment (NW Mediterranean) Vaqué D, Blough HA, DuarteCM The importance of ciliates as components of the microbial community of the oligotrophic coastal area of the Bay of Blanes (NW Mediterranean Sea) was examined based on a 3 yr, high resolution study focused on the composition, abundance and biomass of the ciliate community. The most abundant components of the ciliate community were 'oligotrich' ciliates. Naked oligotrichs included heterotrophic genera represented by Halteria, Strombidium, Strobilidium, and Lohmaniella, as well as mixotrophic genera represented by Laboea and Tontonia and loricate ciliates represented by the group of tintinnids. Autotrophic ciliates were represented by the genus Mesodinium. Other, less abundant groups encountered throughout the study period included the orders Scuticociliatida, Pleurostomatida and Prorodontida. Ciliate community abundance and biomass did not show a simple seasonal pattern. Maximum values were observed in spring, following the winter phytoplankton blooms, throughout the study period. Ciliate communities showed significant interannual differences in abundance and cell size. However, total ciliate biomass (μg C l-1) was similar among years. Changes in ciliate abundance and biomass were independent of temperature. Periods with persistent, heavy rainfall, which promotes pulses of allochthonous material from flushed rivers, were characterized by a reduced abundance of ciliates, and increased pico- and nanoplanktonic populations. Cross correlation analysis revealed that bacterial abundance and chlorophyll a (chl a) concentration were both significantly negatively correlated with ciliate abundance, with time lags of 15 d, suggesting a role for ciliates in the control of these communities. Examination of the variability of ciliate abundance and biomass at different time scales revealed a dominant scale of temporal variation in ciliate abundance at about 50 d, similar to that of chl a in the Bay of Blanes, whereas total ciliate biomass (μg C l-1) did not show any dominant scale of variation. Coastal area · Ciliate abundance and biomass · Community composition · Rainfall · Temporal variabilty Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 12, No. 1. Publication date: January 30, 1997 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1997 Inter-Research.
