Huxleyi Blooms Research Articles

Effects of the diatom-Emiliana huxleyi succession on photosynthesis, calcification and carbon metabolism by size-fractioned phytoplankton

Changes in the species composition, photosynthesis, calcification and size-fractionated carbon metabolism by natural phytoplankton assemblages were monitored in three mesocosms under different nutrient conditions during May 1993. In the 3 enclosures, the decline of the diatom-dominated assemblages was followed by the development of a bloom of the coccolithoporid Emiliania huxleyi. Highest growth of E. huxleyi was observed in the mesocosm with a high N : P ratio, suggesting this species is a good competitor at low phosphate concentrations. The transition from diatom- to E. huxleyi-dominated assemblages brought about a sharp reduction of the phytoplankton standing stock and carbon-specific photosynthetic rate. The relative contribution of the smaller size fraction to total photosynthesis increased as the succession progressed. Calcification rate and E. huxleyi cell-specified calcite production were highest during the early stages of development of the E. huxleyi bloom. Distinct changes in the patterns of 14C allocation into biomolecules were noticed during the diatom-E. huxleyi succession. The diatom-dominated assemblage showed high relative 14C incorporation into low molecular weight metabolites (LMWM), whereas proteins and, specially, lipids accounted for the largest proportion of carbon incorporation in the E. huxleyi bloom. The patterns of photoassimilated carbon metabolism proved to be strongly dependent on cellular size, as protein relative synthesis was significantly higher in the smaller than in the larger size fraction, irrespective of the nutrient regime and the successional stage. These results are discussed in relation to the ecological and physiological features of small phytoplankton.

Patterns of carbon and nitrogen uptake during blooms of Emiliania huxleyi in two Norwegian fjords

Blooms of the coccolithophorid Emiliania huxleyi were monitored in two land-locked fjords, Fauskangerpollen and Nordasvannet (Western Norway), in May 1993. The chemical composi- tion of participate matter, size-fractionated photosynthesis , calcification, nitrogen uptake rates and the patterns of macromolecular synthesis were examined during the peak and decline of E. huxleyi blooms. The temporal evolution of the bloom in Fauskangerpollen was defined by a gradual decrease in cell abundance and cell-specific calcification rates, and by increasing numbers of empty coccospheres and the ratio detached coccoliths/living cells. A large proportion of the nitrogen required for microplank- ton growth was supplied by ammonium and dissolved organic compounds such as urea and, as a con- sequence, the f-ratios were low (-0.2). In general, nitrogen uptake patterns were consistent with ambient concentrations of nitrogenous species. The photosynthetic carbon metabolism of E.huxleyi- dominated phytoplankton assemblages was characterized by high carbon allocation into lipids and relatively low carbon incorporation into protein as compared with diatom-dominated assemblages. Consequently, the organic Gnitrogen uptake ratio determined stoichiometrically was significantly higher (up to 10.8) when coccolithophorids were dominant than in diatom-based or mixed-phyto- plankton assemblages. These carbon incorporation patterns were reflected in differences in the chemi- cal composition of paniculate matter.

Trends in inorganic and organic carbon in a bloom of Emiliania huxleyi in the North Sea

During a survey of the end phase of an Emiliania huxleyi bloom in the northern part of the North Sea we measured total inorganic carbon (TIC) and the fugacity of CO2 (f CO2), as well as standing stocks of CaC03 and particulate organic carbon (POC). Production of CaC03 by E. huxleyi resulted in an immediate increase of f C 0 2 , but led to a long-term decrease in fCO, Observations during a surface survey and at 24 h stations showed a large increase of fCOz with the standing stock of CaCO,. The immediate increase of f C 0 2 is caused by a shift in the chemical equilibria In the inorganic carbon system when alkal~nity decreases relative to dissolved inorganic carbon (DIC). Average f C 0 2 in the high reflectance area (with high numbers of detached coccoliths) was lower than average fCOz In the reference areas, located outside the E. huxleyi bloom. The long-term decrease in fCO, is due to an enhdnced sedimentation of both organic and inorganic carbon in faecal pellets containing heavy calcite. This enhanced sedimentation is reflected in the vertical gradient of TIC between the surf~lce mixed layer and the aphotic zone, which increased from the POC-rich zone to the CaCO, maximum. The overall effect of production, air-sea exchange, mineralisation and sedimentation was a decreabr of f C 0 2 due to a net transport of carbon to below the pycnocline. We tentatively calculate an atmospheric carbon sink of 1.3 m01 m-2 for this bloom of E. huxleyi.

Viral activity in relation to Emiliania huxleyi blooms:a mechanism of DMSP release?

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 128:133-142 (1995) - doi:10.3354/meps128133 Viral activity in relation to Emiliania huxleyi blooms: a mechanism of DMSP release? Bratbak G, Levasseur M, Michaud S, Cantin G, Fernández E, Heimdal BR, Heldal M The role of viral activity with respect to bloom dynamics and production of dissolved dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) was investigated in Norwegian coastal waters and in sea water mesocosms during blooms of the coccolithophorid Emiliania huxleyi (Lohm.) Hay &AMP Mohler. In coastal waters the collapse of the E. huxleyi bloom was accompanied by a simultaneous increase in large virus-like particles (LVLP) and there was a significant inverse relationship between cell-specific calcification rate and LVLP abundance. Results from the mesocosm study indicate that the viral activity may either prevent or terminate the development of E. huxleyi blooms. No significant relationships were found between the abundance of LVLPs and the concentrations of dissolved DMSP and DMS in the field or in the mesocosms. This may be explained by the relatively small size of the E. huxleyi blooms (maximum cell concentration of 11 x 106 l-1) and bacterial degradation of DMSP and DMS, which may have been sufficient to prevent the accumulation of sulfur compounds released after lysis of the cells. Phytoplankton . Emiliania huxleyi . Virus-like particles . VLP . Dimethylsulfoniopropionate . Dimethylsulfide . Calcification . Mesocosm Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 128. Publication date: November 23, 1995 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1995 Inter-Research.

Production and downward flux of organic matter and calcite in a North Sea bloom of the coccolithophore Emiliania huxleyi

In July 1993, an extensive study was made of a large bloom of the coccolithophorid Emiliania huxleyi in the North Sea halfway between the Shetland Islands and Norway. Here we report on the hydrography, production and sedimentation of particulate organic carbon (POC) and calcite carbon (calcite-C) at 4 stations occupied for 24 h, 2 inside the bloom and 2 just outside. The coccolithophorid bloom was confined to North Sea waters, where a stable shallow mixed layer had been formed. Bloom development had entered the decaying phase, judged by the relatively low living cell number (maximally 1200 cells cm-3), the high number of loose coccoliths (up to 350000 coccoliths cm-3), and the fact that sedimentation of calcite-C exceeded production. In the top 15 m at the bloom stations, the mean daily production of coccoliths was 17 per cell. At the 2 stations outside the bloom, the dominant coccolithophore was a holococcolithophorid (up to 1400 cells cn1r3), wlth insignificant amounts of calcite produced per cell. At these stations, nutrients were present in non-lim~ting concentrations and production of POC was twice as high as at the bloom stations. In the bloom, mixed layer nitrate levels were below 0.2 PM. Faecal pellets collected in the sediment traps contained large numbers of coccoliths of E, huxleyi. Although the numbers of grazers at the 2 stations outside the bloom were not lower than those in the bloom, the volume of faecal matter sedimenting at 50 m was about 70 times lower. It is hypothesized that faecal pellets outside the bloom were so light in weight that they did not sink very far before degradation, whereas the pellets produced in the E. huxleyi bloom in general were exported rapidly due to their heavy load of calcite. This implies that recycling of materials in the mixed layer of this bloom is relatively low due to high downward flux rate. The ratio at which POC and calcite-C were sedimenting amounted to 1.3 on average for the 2 bloom stations at 50 m water depth.

Enhanced calcification in the coccolithophorid Emiliania huxleyi (Haptophyceae) under phosphorus limitation

Abstract The effect of phosphorus limitation on calcification in the coccolithophorid Emiliania huxleyi (Lohmann) Hay et Mohler was investigated by chemical Ca and C analyses, as well as in short-term 14C uptake experiments. The latter made use of a newly developed microdiffusion method to separate 14C in coccolith carbonate from photosynthetically assimilated 14C. In comparison with exponentially growing cells in a nutrient-replete medium, cells grown in P-limited chemostats at half the maximum growth rate produced c. 60% more CaCO3 relative to organic carbon. In the short-term incubations, cells from P-limited chemostats showed a relative increase in the capacity for calcification under reduced irradiance and in the dark. Nutrient effects on calcification are of potential interest in considerations of the impact of E. huxleyi blooms on the sea-air CO2 interchange, and they deserve further study.

Zooplankton grazing on the coccolithophore Emiliania huxleyi and its role in inorganic carbon flux

Grazing and faecal pellet production by the copepods Calanus helgolandicus and Pseudocalanus elongatus, feeding on the coccolithophore Emiliania huxleyi, were measured under defined laboratory conditions, together with the chemical characteristics and sinking rates of the faecal pellets produced. Ingestion rates of both copepods were equivalent at comparable cell concentrations, the relationship between ingestion rate (I, cells copepod-1 h-1) and food concentration (C, cells ml-1), being I=0.558C for both species. P. elongatus produced a larger number of smaller faecal pellets than C. helgolandicus, but egested a larger volume of material per individual. Only between 27 and 50% of the ingested coccolith calcite was egested in the faecal pellets, and it is possible that acid digestion in the copepod gut is responsible for these considerable losses. Average sinking rates of faecal pellets containing E. huxleyi coccoliths, produced by both species, were >100 m d-1. The implications of the quantitative laboratory estimates for the vertical flux of inorganic carbon are considered using recently studied shelf-break and oceanic E. huxleyi blooms in the N. E. Atlantic as examples.

Coccolithophorid blooms in the global ocean

The global distribution pattern of coccolithophorid blooms was mapped in order to ascertain the prevalence of these blooms in the world's oceans and to estimate their worldwide production of CaCO3 and dimethyl sulfide (DMS). Mapping was accomplished by classifying pixels of 5‐day global composites of coastal zone color scanner imagery into bloom and nonbloom classes using a supervised, multispectral classification scheme. Surface waters with the spectral signature of coccolithophorid blooms annually covered an average of 1.4×106 km2 in the world oceans from 1979 to 1985, with the subpolar latitudes accounting for 71% of this surface area. Classified blooms were most extensive in the Subarctic North Atlantic. Large expanses of the bloom signal were also detected in the North Pacific, on the Argentine shelf and slope, and in numerous lower latitude marginal seas and shelf regions. The greatest spatial extent of classified blooms in subpolar oceanic regions occurred in the months from summer to early autumn, while those in lower latitude marginal seas occurred in midwinter to early spring. Though the classification scheme was efficient in separating bloom and nonbloom classes during test simulations, and biogeographical literature generally confirms the resulting distribution pattern of blooms in the subpolar regions, the cause of the bloom signal is equivocal in some geographic areas, particularly on shelf regions at lower latitudes. Standing stock estimates suggest that the presumed Emiliania huxleyi blooms act as a significant source of calcite carbon and DMS sulfur on a regional scale. On a global scale, however, the satellite‐detected coccolithophorid blooms are estimated to play only a minor role in the annual production of these two compounds and their flux from the surface mixed layer.

The impact of a coccolithophore bloom on oceanic carbon uptake in the northeast Atlantic during summer 1991

Measurements of the carbonate system in the surface waters of the northeast Atlantic during summer 1991, following the main growth phase of a bloom of the coccolithophore Emiliania huxleyi are presented. We examine the perturbation of the carbonate system and assess the effect of calcification on the air-sea gradient of dissolved carbon dioxide in the surface ocean. An estimate of 1:1 organic to inorganic carbon uptake is calculated using the measurements of the surface carbonate parameters which is consistent with other estimates for E. huxleyi populations using radio-tracer methods. Using the changing ratio of dissolved carbon dioxide to nitrate concentration we demonstrate a relative increase in dissolved carbon dioxide due to calcification with evidence of this increase supported by estimates of the buffer factor and C:N assimilation ratios. Within the E. huxleyi bloom the effect of calcification on alkalinity appears to have reduced the air-sea gradient by ∼ 15 μatms (corrected to a constant temperature) using measurements from a 440 km section along the 20°W meridian. This reduction could prove to be significant in terms of the overall drawdown of carbon during the spring-summer season in this area.

Dimethylsulfide in a large-scale coccolithophore bloom in the Gulf of Maine

Blooms of the coccolithophore, Emiliania huxleyi, are common phenomena in the Gulf of Maine in early summer, as revealed by AVHRR imagery. It is known from laboratory cultures and some field studies that the production of the important volatile sulfur compound, DMS, and its precursor, DMSP, are confined largely to a few classes of phytoplankton, specifically the Dinophyceae and the Prymnesiophyceae, which includes the coccolithophores. In the Gulf of Maine, concentrations of DMS and DMSP were as much as an order of magnitude higher within a E. huxleyi bloom than at stations outside the bloom area, including stations with high phytoplankton biomass of other taxa. Values of both DMS and DMSP were highest in the mixed layer, with depth maxima associated with the chlorophyll maxima, generally at 10–15 m. In addition, higher levels of DMS and dissolved DMSP were associated with older parts of the bloom, as determined by numbers of loose coccoliths. This is the first example in nature where DMS production is related, not only to a given species of algae, but also to the stage of the bloom.

The coccolithophore Emiliania huxleyi and global climate

Cells of Emiliania huxleyi are surrounded by ‘coccoliths', minute, elegant scales of calcium carbonate. In all the oceans, particularly at mid-latitudes, this species forms gigantic blooms, readily visualized by satellite imagery. Coccolith-bearing organisms, of which E. huxleyi is by far the most abundant representative, are the major contributors to the ocean floor limestone sediments, and this in turn is the largest long-term sink of inorganic carbon on earth. In addition, E. huxleyi blooms emit vast amounts of dimethyl-sulphide (DMS), a gas which, on oxidation, is a dominant source of cloud nuclei. The profusion of E. huxleyi and its intimate involvement with the global biogeochemical cycles of both carbon and sulphur make it a key component of the greenhouse effect (CO2), natural acid rain and albedo regulation.E. huxleyi blooms are often almost monospecific. They can be visualized by satellite imagery and leave highly characteristic skeletal and macromolecular markers which accumulate on the deep-sea floor as a long-term record of their history. The organism is easily cultured in the laboratory and molecular genetical, biochemical and physiological studies are underway.We focus on Emiliania huxleyi as a model organism to study interactions between oceanic plankton and climate. Benefits of this approach are: (1) to highlight the idiosyncratic non-linear character of these interactions; (2) to reveal the intimate coupling of the oceanic carbon cycle and DMS productivity; and (3) to allow an integrated modelling and experimental approach, integrating multi-disciplinary studies that range from the global down to the macromolecular level and through geological time. E. huxleyi coccoliths and specific biomarkers preserved in the geological archive not only provide information on the distribution of this organism in the geological past. The connection with extensive neontological research offers a unique opportunity to reconstruct the development of the entire E. huxleyi system, including its multifarious climatic interactions, through geological time.The ‘Global Emiliania Modeling Initiative’ (GEM), started in 1990, is a European research program intended to investigate and model the Emiliania huxleyi system.