排序方式： 共有3条查询结果，搜索用时 0 毫秒
1
1.
Isabel G. Teixeira Francisco G. Figueiras Bibiana G. CrespoSílvia Piedracoba 《Estuarine, Coastal and Shelf Science》2011
The dilution technique, combined with identification and enumeration of pico-, nano- and micro-plankton by microscopy, was used to estimate microzooplankton impact on the microbial community in surface waters of a coastal embayment on the NW Iberian upwelling system. Microzooplankton were important consumers of autotrophic and heterotrophic plankton in this system, feeding up to 93% of standing stock and more than 100% of production of several groups. Heterotrophic bacteria and heterotrophic picoflagellates experienced the highest and constant impact, with 75–84% of their standing stocks and 85–102% of their production being channelled through the microbial food web. Pico- and nano-phytoplankton were also consumed, although maximum grazing occurred on diatoms during upwelling events, coinciding with highest primary production. Predation on pico-nano-heterotrophs was especially relevant under downwelling conditions, when consumption of total carbon and particularly autotrophic carbon was considerably lower than during upwelling. The results suggest that the existence of a multivorous food web, extending from the microbial loop to the herbivorous food web, could be a major feature in this coastal upwelling system. The microbial loop, which occurs as a permanent background in the system, would contribute to sustain the microbial food web during downwelling, whereas the herbivorous food web could coexist with a microbial food web based on large diatoms during upwelling. The multivorous food web would partially divert diatoms from sinking and hence favour the retention of organic matter in the water column. This could enhance the energy transfer to higher pelagic trophic levels in coastal upwelling systems. 相似文献
2.
Mercedes de la Paz Bibiana Debelius Diego Macías Agueda Vázquez Abelardo Gómez-Parra Jesus M. Forja 《Continental Shelf Research》2008
This study presents the distribution of dissolved inorganic carbon (DIC) along the Strait of Gibraltar, its tidal-induced variability, as well as the inorganic carbon exchange between the Atlantic Ocean and Mediterranean Sea. During November 2003, water column samples were collected at nine stations to measure total alkalinity (TA), pH, and dissolved oxygen (DO) for the spatial characterization of the carbonate system. At the same time, anchored samplings were carried out, above the Camarinal Sill and in the Eastern Section of the Strait, in order to assess the tidal mixing effects for oxygen and DIC distribution on the water column. Three distinct water masses can be discerned in this area: the Surface Atlantic Water (SAW), the Mediterranean Water (MW), and the less abundant North Atlantic Central Water (NACW). The observations show an increase in the DIC and a decrease in oxygen concentration with depth, related to the different physico-chemical features of each water mass. The results show the high time-dependence of the vertical distribution of DIC with the interface oscillation, affected by the intense mixing processes taking place in the Strait. Intense mixing episodes over the Camarinal Sill are responsible for an increase in the DIC concentrations in the upper layer of the Eastern Section of the Strait. Higher DIC concentrations in the Mediterranean than in the Atlantic waters are responsible for a net DIC transport of 1.47×1012 mol C yr−1 to the Atlantic Ocean. Nevertheless, the net exchange is highly sensitive to the interface definition, as well as to the estimate of water volume transport used. 相似文献
3.
Five marine microalgae (Tetraselmis chuii, Rhodomonas salina, Chaetoceros sp., Isochrysis galbana (T-iso) and Nannochloropsis gaditana), in the same biovolume quantity, were exposed to 72h growth-inhibition tests with atrazine and LAS. In all cases, the inhibition effect of atrazine was higher than that of LAS up to two orders of magnitude higher in the case of T. chuii. In a second part of the study, initial cellular densities for each microalga strain and fixed organic compound concentration were varied, and results show density has a clear influence in growth inhibition tests. Finally, the sum of all data obtained in the study was expressed in terms of "toxic cellular quota" (mass of chemical substance per cell). The result was a sigmoid curve with a good fit, including the two main factors in toxicity tests, initial cellular density and contaminant concentration. This toxic cellular quota exhibits a general tendency to increase with cell volume/size. 相似文献
1