Biological controls on dissolution of diatom frustules during their descent to the deep ocean: Lessons learned from controlled laboratory experiments     

Uta Passow  Megan A. French  Maya Robert 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(12):1147-1157

The majority of opal produced by diatoms dissolves during their sedimentation to the seafloor, but spatial and temporal variability of dissolution rates are large. Controlled laboratory experiments using live phytoplankton or phyto-detritus may help identify the different processes, including those that are biologically mediated or physico-chemically driven, that impact the dissolution of frustules and the aforementioned variability. Results of eight bSiO₂ dissolution experiments, seven of which were conducted at low temperatures (<6 °C) are presented within the context of earlier similar studies, and different phases of dissolution dynamics characterized. TEP concentration, aggregation and the physiological status of the diatoms determined the period during which diatoms may maintain the protective membrane that surrounds their frustule and effectively reduces or completely inhibits (lag period) dissolution for some time. Once diatoms loose the capability to maintain their protective membrane, bacterial activity compromises it. Physico-chemical dissolution, which depends on frustule structure and abiotic environmental conditions, begins once the protective membrane is damaged. The ability of diatoms to maintain their membrane, the bacterial composition and activity governing its degradation, and the physico-chemical dissolution dynamics of exposed frustules are all impacted by temperature. In our experiments instantaneous dissolution rates were not dependant on bSiO₂ concentration at low temperatures, although such a relationship was observed under otherwise identical conditions at 15 °C, implying that biotic factors rather than physico-chemical processes initially dominated dissolution at polar temperatures. Since inhibition of bSiO₂ dissolution at low temperatures was inhibited to a greater extent than organic matter degradation, we postulate that it was not reduced bacterial activity but the enhanced ability of diatoms to maintain their membrane and thus withstand microbial attack that caused the low initial dissolution rates at <6 °C. In situ, interactions between the different biotic and abiotic processes impacting dissolution combined with differences in sinking velocity of diatom aggregates and grazing effects could easily explain high spatial and temporal variability in the accumulation of diatoms on the seafloor. Simple calculations based on our experimental results suggest that Fragilariopsis kerguelensis, for example, would be appreciably more likely to reach the seafloor than Chaetoceros debilis if both grow at low growth rates, e.g. under growth limiting conditions. However, dissolution behavior of Chaetoceros debilis during sedimentation may differ under conditions where this species forms large blooms.  相似文献   

Mesozooplankton biomass and grazing responses to Cyclone Opal, a subtropical mesoscale eddy     

Michael R. Landry  Moira Decima  Melinda P. Simmons  Cecelia C.S. Hannides  Emy Daniels 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1378

As part of E-Flux III cruise studies in March 2005, plankton net collections were made to assess the effects of a cyclonic cold-core eddy (Cyclone Opal) on the biomass and grazing of mesozooplankton. Mesozooplankton biomass in the central region of Cyclone Opal, an area of uplifted nutricline and a subsurface diatom bloom, averaged 0.80±0.24 and 1.51±0.59 g DW m⁻², for day and night tows, respectively. These biomass estimates were about 80% higher than control (OUT) stations, with increases more or less proportionately distributed among size classes from 0.2 to >5 mm. Though elevated relative to surrounding waters south of the Hawaiian Islands (Hawai’i lee), total biomass and size distribution in Cyclone Opal were almost exactly the same as contemporary measurements made at Stn. ALOHA, 100 km north of the islands, by the HOT (Hawaii Ocean Time-series) Program. Mesozooplankton biomass and community composition at the OUT stations were also similar to ALOHA values from 1994 to 1996, preceding a recent decadal increase. These comparisons may therefore provide insight into production characteristics or biomass gradients associated with decadal changes at Stn. ALOHA. Gut fluorescence estimates were higher in Opal than in ambient waters, translating to grazing impacts of 0.11±0.02 d⁻¹ (IN) versus 0.03±0.01 d⁻¹ (OUT). Over the depth-integrated euphotic zone, mesozooplankton accounted for 30% of the combined grazing losses of phytoplankton to micro- and meso-herbivores in Opal, as compared to 13% at control stations. Estimates of active export flux by migrating zooplankton averaged 0.81 mmol C m⁻² d⁻¹ in Cyclone Opal and 0.37 mmol C m⁻² d⁻¹ at OUT stations, 53% and 24%, respectively, of the carbon export measured by passive sediment traps. Migrants also exported 0.18 mmol N m⁻² d⁻¹ (117% of trap N flux) in Cyclone Opal compared to 0.08 mmol N m⁻² d⁻¹ (51% of trap flux) at control stations. Overall, the food-web importance of mesozooplankton increased in Cyclone Opal both in absolute and relative terms. Diel migrants provided evidence for enhanced export flux in the eddy that was missed by sediment trap and ²³⁴Th techniques, and migrant-mediated flux was the major export term in the observed bloom-perturbation response and N mass balance of the eddy.  相似文献   

Winter-spring phytoplankton blooms in Dabob Bay, Washington   总被引：4，自引：2，他引：4  

Rita A. Horner  James R. Postel  Claudia Halsband-Lenk  James J. Pierson  Georg Pohnert  Thomas Wichard 《Progress in Oceanography》2005,67(3-4):286

Scientific investigations in Dabob Bay, Washington State, USA, have been extensive since the early 1960s, but phytoplankton blooms have been studied mostly with regard to chlorophyll concentrations and little is known about the phytoplankton species themselves. Here we provide information on the species present, their abundances during blooms, their contribution to organic carbon concentrations and the ability of some phytoplankton species to produce toxic aldehydes that may impact metazoan grazers.Multiple blooms of phytoplankton, dominated by diatoms, occurred in the late winter-early spring period, with depth-integrated chlorophyll levels ranging from <20 to 230 mg m⁻² and peaks in February and April. The major bloom species included Skeletonema costatum, Thalassiosira spp. and Chaetoceros spp; Phaeocystis cf. pouchetii occurred in 2002 and 2004. Other taxa or groups of organisms that were sometimes abundant included unidentified small flagellates <10 μm in size and unidentified heterotrophic dinoflagellates. Large diatoms usually comprised most of the cell carbon, but a large, heterotrophic dinoflagellate, identified only as Gyrodinium “tear” because of its shape, was a major contributor to the microplankton carbon when present even in small numbers. Five Thalassiosira species and S. costatum were found to produce polyunsaturated aldehydes (PUA) that are known to affect copepod reproduction and hatching success. Our findings are similar to the few previous studies in the last four decades that included phytoplankton species and suggest long-term similarities and relative stability in the phytoplankton species present and their timing in Dabob Bay.  相似文献   

渤海中、南部表层沉积硅藻的定量分析   总被引：4，自引：0，他引：4  

程广芬  曹玉强 《中国海洋大学学报(自然科学版)》1991,(4)

对取自渤海中、南部海底表层的44个沉积物样品进行了硅藻分析。样品中共含硅藻20属41种,主要是潮间带、沿岸性底栖或浮游种类,其中尤以具槽直链藻Melosira sulc-ata和小环藻Cyclotella最多见。对本区的表层沉积硅藻用多元统计方法进行分区,共划分出三区、两亚区,井与其他海区进行了比较。  相似文献   

Si–C interactions during degradation of the diatom Skeletonema marinoi     

Brivaëla Moriceau  Madeleine Goutx  Catherine Guigue  Cindy Lee  Robert Armstrong  Marie Duflos  Christian Tamburini  Bruno Charrire  Olivier Ragueneau 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1381-1395

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Taxonomic composition and seasonality of diatoms in three Dinaric karstic lakes in Croatia     

Nenad Jasprica  Dubravka Hafner 《Limnologica》2005,35(4):304-319

The composition and temporal distribution of planktonic diatoms were studied in three small shallow karstic lakes – Modro Oko, Desne, and Kuti – throughout the seasons in 1994, 1995, 1997, and 1998. Physico-chemical parameters did not differ among the three lakes, except for NO₃ concentrations. Altogether, 137 diatom taxa within 41 genera were found in all three lakes combined. The highest number of taxa belonged to the genera Surirella (13), Navicula (12), andCymbella (9). Most taxa were tychoplanktonic, with true panktonic taxa contributing only 14% of the total. Despite their physical-chemical similarity, the lakes showed differences in the structure and dynamics of their diatom communities. Blooms occurred at different times in each of the lakes, and community similarity (Jaccard index) among all three was low (17.6–29.1%). The highest mean values of surface diatom abundance in Modro Oko (2199 cells L⁻¹), Desne (7900 cells L⁻¹), and Kuti (20690 cells L⁻¹) were not significantly different. Margalef's species richness index did not differ either among the lakes or seasonally. Only five diatom taxa in quantitative samples, and 22 taxa in net-samples, were common to all lakes. The most frequent diatoms were Cyclotella striata (56–93%), Fragilaria ulna (50–67%), and Asterionella formosa (27–83%). The most abundant taxa in Modro Oko, Desne, and Kuti were, respectively, Cymbella sp. 1 (402 cells L⁻¹), Cyclotella striata (3000 cells L⁻¹) and Asterionella formosa (20690 cells L⁻¹). Eighteen taxa were recorded for the first time in Croatia: Amphora commutata, Caloneis amphisbaena var. subsalina, C. silicula var. peisonis, Campylodiscus echeneis, Coscinodiscus lacustris, Denticula elegans, Gyrosigma acuminatum var. lacustre, G. distortum var. parkeri, G. fasciola, Navicula menisculus var. menisculus, N. pusilla, N. helensis, Stauroneis parvula var. prominula, Staurosira construens f. subsalina, Stephanodiscus sp. 1, Surirella gracilis, S. ovalis, and S. striatula. The genus Stephanodiscus was recorded for the first time in Croatia.  相似文献   

Dissolved silica budget in the North basin of Lake Lugano     

Annette Hofmann  Didier RoussyMontserrat Filella 《Chemical Geology》2002,182(1):35-55

We studied the dissolved silica cycle in the water column of the North basin of Lake Lugano, Switzerland/Italy. Lake Lugano is a meromictic, eutrophic lake, permanently stratified below 100-m depth. A one-box model was used to calculate a silica mass-balance over 1993, based on various lake measurements, such as sediment traps, sediment cores, water analysis and biota countings. We found that the North basin of Lake Lugano is at steady state as far as dissolved silica is concerned. The primary source of dissolved silica in the lake is river input (about 80%), with diffusion from bottom sediments and groundwater input also playing a role. Atmospheric input is negligible. The main export of dissolved silica occurs via biogenic uptake by diatoms and final burial of their frustules in the bottom sediment. Loss of dissolved silica through the lake outflow only represents 15% of the total output. Of the total amount of Si exported to the lake bottom through diatom sinking, less than 20% is re-supplied to the surface water by diffusion. Thus, the lake acts as an important permanent sink for silica. The long residence time of dissolved silica in the lake (7 years) is related to the strong physical stratification of the lake. Only about 10% of the standing stock are available to phytoplankton uptake.  相似文献   

吉林省六道沟硅藻土的矿物学特征研究     

李海龙 《吉林地质》1992,11(4):60-66

六道沟硅藻土矿床是我国北方中—大型优质硅藻土矿床。本文通过电镜扫描、x光衍射、红外吸收光谱、差热分析和化学分析等手段。研究了该矿床硅藻土的一般矿物学特征。  相似文献   

昆明草海晚更新世硅藻植物群及其环境演化   总被引：3，自引：0，他引：3  

张茂恒  黄巧华 《云南地理环境研究》1993,5(1):55-64

通过对草海2号孔硅藻植物群生态演化及沉积特征的研究,将草海晚更新世划分为十个硅藻带和五个环境演化段落,说明5万年以来草海经历了由河流三角洲—中深湖滨—浅湖—沼泽的发展过程,在距今4.4万年时,滇池湖达到高潮,以后一直湖退,其中距今2.8万年左右由于河口砂坝的发展而形成海埂,使草海与滇池相对隔离而进入一个独立发展阶段,并加快了草海沼泽化进程。从气候上看,5万年以来,草海也经历了凉—暖—凉—温的两次周期性变化。  相似文献   

Diatomeen-, pollen- und sedimentmikrostratigraphische Untersuchungen zur anthropogenen Beeinflussung des Höllerer Sees (Oberösterreich)     

Roland Schmidt  Heikki Simola 《Aquatic Sciences - Research Across Boundaries》1991,53(1):74-89

A profundal sediment core from Höllerer See frozen in situ was studied by means of diatom, microstratigraphical tape peel and pollen analyses. Varved sequences reflect eutrophication during mediaeval settlement and according to varve counts a recent eutrophic phase since the 1970's. Mesotrophication in-between coincides with regrowth of forests near the lake.

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