Spring Bloom Period Research Articles

Micro- and mesozooplankton in Southwest Greenland waters in relation to environmental factors

Plankton samples and oceanographic data were obtained during transect studies across fishing banks over the Southwest Greenland shelf in June 1999, May, and July 2000. The study gives a detailed description of micro- and mesozooplankton distributions and community structures during spring bloom and post bloom periods. Plankton distributions were related to the physical environment described by a hydrodynamic ocean circulation model. More than 30 species and a larger number of taxonomic categories were identified in the zooplankton samples. Large copepodites of Calanus finmarchicus, Calanus glacialis, and Calanus hyperboreus generally dominated the micro- and mesozooplankton biomass, with Pseudocalanus spp., Metridia longa, and Oithona spp. comprising most of the remaining biomass. By number, bivalves larvae and relatively large copepod nauplii (>200 μm) dominated the zooplankton community (>50 μm) in May, whereas smaller copepod nauplii (<200 μm) were dominating in June and July. In May during a spring bloom period, diatoms, Thalassiosira spp. and Chaetoceros spp., generally dominated the biomass of the plankton community of the upper 100 m followed by heterotrophic flagellates, copepods, other invertebrates, and ciliates. Conversely in June (and July) during post bloom, large copepods were dominating. Hydrodynamic model simulations of ocean currents and trajectories of potential plankton transports showed differences in potential advection of plankton across shelf banks. The circulation around the banks seems to create retention areas entrapping plankton for periods. Model simulations predict that upwelling occurs west of the shelf banks and to a lesser extent in the deep channels separating the banks. This upwelling, caused by wind and tidal motions, probably increases productivity and carbon cycling over the shelf areas.

Regional water quality mapping through the assimilation of spaceborne remote sensing data to ship‐based transect observations

Satellite observations and surface‐observed transect data are combined to assess the spatial characteristics of water quality in the Baltic Sea, northern Europe. The technique that optimally assimilates the two data sources is based on Bayes' theorem. The method considers the spatial accuracy characteristics of both transect and satellite data. The mathematical formulation of the method is generally applicable. Hence it can be applied to other environmental monitoring problems as well. This investigation demonstrates its feasibility for water quality mapping. The characteristic under investigation is chlorophyll (chl a) concentration, which is currently operationally monitored in the Baltic Sea at shipborne Alg@line transects, using flow‐through fluorometer sampling systems. In order to optimally extrapolate transect observations the developed method benefits from the full spatial coverage of spaceborne optical spectroradiometer data. The results show that the estimation accuracy of regional chl a concentration during the spring bloom period substantially improves as satellite observations are assimilated to transect data. The assimilation results show significantly higher accuracies than those obtained using either extrapolated transect data or stand‐alone retrieval algorithms for satellite data.

Phytoplankton Pigments in Baltic Sea Seston and Sediments: Seasonal Variability, Fluxes, and Transformations

We studied the temporal variability in the composition of plant pigments in water-column particulate matter and in surface sediments, with specific emphasis on bloom events. The pigment concentration of sinking and suspended particles was used to evaluate pre- and post-depositional decomposition of bloom-derived phytodetritus in the Baltic proper. Water, sediment, and sediment trap samples were collected in 1994 at a long-term coastal monitoring station with fine sediments and a water depth of 36m, situated near the Askö Laboratory in the north-western part of the Baltic Sea proper.Annual phytoplankton succession showed an early spring bloom dominated by diatoms, followed by dinoflagellates in late spring and early summer. Later in summer, this dinoflagellate community was gradually replaced by a filamentous, nitrogen-fixing cyanobacterial bloom; late summer-early autumn was characterized by diatoms. The highest chlorophylla flux occurred in spring during peak diatom bloom conditions, which resulted in peak concentrations of chlorophylla in sediments. Assuming that all chlorophylla in sediments in early May was derived from the current bloom, it was estimated that approximately half (48%) the bloom-derived chlorophylla was decomposed in two months. The highest total phaeopigment/chlorophylla ratios (an index of the amount of chlorophylla decay), were found in water column particulate matter (PM) during the spring bloom and occasional high-energy winter periods. The latter higher ratios were likely due to wind-induced resuspension of surface sediments into the water column and trap materials. The settling rate of pigments in the water column indicated rapid sedimentation of diatoms and slow sedimentation of dinoflagellates during the spring bloom. In summer, unicellular cyanobacteria, including picocyanobacteria, appeared to have higher sedimentation rates than filamentous nitrogen-fixing cyanobacteria, which seemed to decompose largely in the water column. Thus, this study demonstrated that plant pigments were useful biomarkers of the taxonomic composition of phytoplankton blooms and their sedimentation and subsequent decomposition in the Baltic Sea.

The plankton community on Sukkertop and Fylla Banks Off West Greenland during a spring bloom and post-bloom period: Hydrography, phytoplankton and protozooplankton

Abstract The plankton community structure was investigated on Sukkertop and Fylla Banks off West Greenland during the spring bloom in May 2000 and the post-bloom period in June 1999. In May a small change in density, clearly illustrated by the profile of potential energy, was sufficient to support a spring bloom in the upper part of the water column. The spring-bloom phytoplankton community displayed high biomass (92 ± 45 mg C m3) dominated by species of the genera Thalassiosira and Chaetoceros. The phytoplankton species composition, ongoing sedimentation and nutrient depletion indicated late spring-bloom conditions. Spring-bloom heterotrophic biomass (17 ± 7 mg C m-3) was dominated by large heterotrophic dinoflagellates (> 20 μm). In June, low autotrophic biomass was present at post-bloom stations (2 ± 1 mg C m-3) and small autotrophic flagellates (< 10 μm), mostly haptophytes, dominated the phytoplankton community. Heterotrophic biomass was low (5 ± 1 mg C m-3) and an important part was comprised by het...

Zooplankton population dynamics: measuring in situ growth and mortality rates using an Optical Plankton Counter

An application to assess in situ population dynamics rates is introduced based on the measurements of size-structured zooplankton population. This method differs from those based on species and stages by taking advantage of allometrically-scaled rates, automated sampling devices and net tows. For the first test of this method, we conducted 3 surveys in a nearly enclosed sub-Arctic fjord in northern Norway, from early May to mid June 1998, the period of the spring bloom. Bio-volume spectra in the size range between 10 -1 and 10 3 mm 3 individual body volume, from small mesozooplankton to euphausiids, were derived from the Optical Plankton Counter measurements. From 3 bio-volume spectra measured on Days 1, 21, and 35, we calculated in situ individual growth and mortality rates using the theory based on biomass spectra. The net samples corroborate the basic fact that Calanus finmarchicus and euphausiids absolutely dominate in 2 different size ranges. In this spring bloom period, the first generation of Calanus finmarchicus at copepodite stage CIV dominated the size range between 0.3 and 0.58 mm 3 , and had a growth rate within 0.02 and 0.17 d -1 . C. finmarchicus at copepodite stage CV and euphausiid larva dominated the size range from 0.58 to 4 mm 3 . Their growth rates increased from 0.2 d -1 at the size of 0.71 mm 3 to the peak of 0.59 d -1 at the size of 1.9 mm 3 , and then decreased to 0.22 d -1 at the size of 4 mm 3 . In the size range above 4 mm 3 , euphausiid juveniles and adults were absolutely dominant. The growth rate estimated from the bio-volume spectra varied between 0.11 and 0.19 d -1 at the size range from 4 to 400 mm 3 . In the size range between 0.3 and 0.58 mm 3 , the mortality rate varied between -0.03 and -0.05 d -1 . The mortality rate reached -0.38 d -1 in the range from 0.71 to 10 mm 3 . In the size range between 10 and 40 mm 3 the rate decreased from -0.31 to -0.11 d -1 , and in the size range above 40 mm 3 the rate increased to -0.27 d -1 . The comparison with estimates from net tow samples and literature data indicates that the biomass spectrum theory affords a valuable method for estimating in situ individual growth and population mortality rates by providing high resolution in size classes and a greater degree in accuracy. It is also less labor-intensive and time-consuming than other methods. A test of this method in an advective environment needs further study.

Comparison of carbon and opal export rates between summer and spring bloom periods in the region of the Antarctic Polar Front, SE Atlantic

Abstract Although primary production in the Antarctic Circumpolar Current is not above the world average and carbon burial rates are low, 70% of the world's opal burial occurs in this zone and it has been suggested that blooms of large diatoms are responsible for this extraordinary situation. Here we compare export fluxes during bloom and steady-state situations near the Antarctic Polar Front in the SE Atlantic. In a previous expedition during the austral spring, we observed the development of a bloom that led to the sudden export of particles (Deep-Sea Res. II 44 (1997) 457). Here we report the results of a second expedition to the same area in summer (December–January), 3 years later. 234 Th was monitored in the surface water and in Rosette casts down to a water depth of 500 m as tracer of export production in an intensive sampling program within a box of 275×375 km 2 . The distribution of particulate and dissolved 234 Th was remarkably constant over time and location. Total (dissolved+particulate) 234 Th activities were depleted relative to its parent 238 U at the surface ( 234 Th/ 238 U activity ratio approximately 83%), reaching equilibrium at a depth of around 190 m. This constant depletion corresponds to a 234 Th export rate of 1115 dpm/m 2 /d, 35% of the value observed during the spring bloom. Below 80 m depth, 234 Th on suspended particles correlates well with both particulate organic carbon (POC) and particulate biogenic silica (BSi), with a POC/ 234 Th ratio of 10.2±0.8 μmol/dpm and a BSi/ 234 Th ratio of 2.9±0.2 μmol/dpm. Using these ratios, the export from the upper 190 m is calculated to be 11.3 mmol C/m 2 /d and 3.2 mmol Si/m 2 /d. The export rates from the surface mixed layer (at 100 m depth) are 8.8 mmol C/m 2 /d and 2.5 mmol Si/m 2 /d. Thus, whereas in spring we had observed a sudden increase from a negligible to a high export rate, the summer situation around the Polar Front was characterized by a lower but steady export rate. This summer flux contributes a similar fraction to the annual export budget as the previously observed spring bloom, which has higher export rates but a much shorter duration.

Stability of bacterial and viral community compositions in Danish coastal waters as depicted by DNA fingerprinting techniques

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 27:219-232 (2002) - doi:10.3354/ame027219 Stability of bacterial and viral community compositions in Danish coastal waters as depicted by DNA fingerprinting techniques Lasse Riemann*, Mathias Middelboe Marine Biological Laboratory, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark *Present address: Freshwater Biological Laboratory, University of Copenhagen, 51 Helsingørsgade, 3400 Hillerød, Denmark. E-mail: lriemann@vip.cybercity.dk ABSTRACT: Variations in bacterial and viral community compositions were examined over spatial scales ranging from centimeters to kilometers and over temporal scales of days to months in Danish coastal environments by means of denaturing gradient gel electrophoresis (DGGE) and pulsed field gel electrophoresis (PFGE), respectively. Despite several-fold differences in bacterial activity and chlorophyll a, we found only a few differences in microbial community composition among samples from 30 cm intervals in a 3 m vertical profile across a narrow pycnocline during a subsurface coccolithophorid bloom in the southern Kattegat. Likewise, only a few changes in community composition were observed during a 2 mo spring bloom period in the eutrophic Roskilde Fjord. However, more pronounced differences were observed among samples from 5 stations on a transect crossing the Skagerrak-Kattegat front where 2 water masses with different physico-chemical properties meet. The 2 water masses harbored distinct bacterial and viral communities, and a gradual mixing of the microbial communities was observed across the front. Our study indicates stability of microbial community compositions in Danish coastal waters and suggests that changes in microbial abundance and activity were not associated with successions in bacterial and viral communities discernible by the applied DGGE and PFGE protocols. KEY WORDS: Bacteria · Virus · Fingerprinting · Denaturing gradient gel electrophoresis · DGGE · Pulsed field gel electrophoresis · PFGE Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 27, No. 3. Online publication date: April 16, 2002 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2002 Inter-Research.

One-dimensional model of short-term dynamics of the pelagic ecosystem in the NW Mediterranean Sea: effects of wind events

A one-dimensional coupled physical–biological model of the mixed layer was applied to the pluridisciplinary data set acquired at short-time scales at a fixed station during the DYNAPROC cruise (May 1995) in the open NW Mediterranean. This cruise provided the opportunity to observe upper layer mixing, pycnocline deepening and vertical advection resulting from several wind events. The physical model is an eddy–kinetic-energy model; parameterisation of Ekman pumping and relaxation to the temperature data were introduced to reproduce the vertical advection observed during the major wind event. Eight variables were included in the ecosystem model: three classes of phytoplankton (diatoms, nanoflagellates and picoplankton), two nutrients (nitrate and ammonium), one herbivorous zooplankton and two types of detritus. Simulation over a 1-month period, performed with real meteorological data recorded during the cruise, reasonably reproduced the effects of the wind events, i.e. mixing and Ekman pumping which induced a 10-m vertical advection of the pycnocline. The observed nitrate and ammonium concentrations and the phytoplankton decrease were reproduced by the model. The transition from a mesotrophic ecosystem, characteristic of the spring bloom period, to an oligotrophic system was successfully simulated. For example, the nanoflagellate and diatom contributions decreased during the month while that of the picoplankton doubled; the decline in herbivorous zooplankton was also reproduced. The simulated results showed that the decrease in diatoms and nanoflagellates resulted from both grazing pressure and significant cloud cover at the end of the month. Vertical advection also plays a nonnegligible role on the simulated temporal changes of the three phytoplankton classes. In fact, it displaces the subsurface peak nearer the surface, and thus allows the phytoplankton to slightly develop a few days after the major wind event, even if diatoms and nanoflagellates decrease overall.

Phytoplankton production patterns in Massachusetts Bay and the absence of the 1998 winter-spring bloom

The seasonal productivity cycle and factors controlling annual variation in the timing and magnitude of the winter–spring bloom were examined for several locations (range: 42°20.35′–42°26.63′N; 70°44.19′–70°56.52′W) in Boston Harbor and Massachusetts Bay, USA, from 1995 to 1999, and compared with earlier published data (1992–1994). Primary productivity (mg C m−2 day−1) in Massachusetts Bay from 1995 to 1999 was generally characterized by a well-developed winter–spring bloom of several weeks duration, high but variable production during the summer, and a prominent fall bloom. The bulk of production (mg C m−3 day−1) typically occurred in the upper 15 m of the water column. At a nearby Boston Harbor station a gradual pattern of increasing areal production from winter through summer was more typical, with the bulk of production restricted to the upper 5 m. Annual productivity in Massachusetts Bay and Boston Harbor ranged from a low of 160 g C m−2 year−1 to a high of 787 g C m−2 year−1 from 1992 to 1999. Mean annual productivity was higher (mean=525 g C m−2 year−1) and more variable near the harbor entrance than in western Massachusetts Bay. At the harbor station productivity varied more than 3.5-fold (CV=40%) over an 8 year sampling period. Average annual productivity (305–419 g C m−2 year−1) and variability around the means (CV=25–27%) were lower at both the outer nearfield and central nearfield regions of Massachusetts Bay. Annual productivity in 1998 was unusually low at all three sites ( 0.05) among years (1995–1999). The mean photic depth during the bloom period was significantly deeper (P < 0.05) in 1998, signifying greater light availability with depth. Nutrients were also in abundance during the winter–spring of 1998 with stratified conditions not observed until May. In general, the magnitude of the winter–spring bloom in Massachusetts Bay from 1995 to 1999 was significantly correlated with winter water temperature (r2=0.78) and zooplankton abundance (r2=0.74) over the bloom period (typically February–April). The absence of the 1998 bloom was associated with higher than average water temperature and elevated levels of zooplankton abundance just prior to, and during, the peak winter–spring bloom period.

Biogeochemistry of total organic carbon and nitrogen in the Sargasso Sea: control by convective overturn

The contributions of total organic carbon and nitrogen to elemental cycling in the surface layer of the Sargasso Sea are evaluated using a 5-yr time-series data set (1994–1998). Surface-layer total organic carbon (TOC) and total organic nitrogen (TON) concentrations ranged from 60 to 70 μM C and 4 to 5.5 μM N seasonally, resulting in a mean C : N molar ratio of 14.4±2.2. The highest surface concentrations varied little during individual summer periods, indicating that net TOC production ceased during the highly oligotrophic summer season. Winter overturn and mixing of the water column were both the cause of concentration reductions and the trigger for net TOC production each year following nutrient entrainment and subsequent new production. The net production of TOC varied with the maximum in the winter mixed-layer depth (MLD), with greater mixing supporting the greatest net production of TOC. In winter 1995, the TOC stock increased by 1.4 mol C m−2 in response to maximum mixing depths of 260 m. In subsequent years experiencing shallower maxima in MLD (<220 m), TOC stocks increased <0.7 mol C m−2. Overturn of the water column served to export TOC to depth (>100 m), with the amount exported dependent on the depth of mixing (total export ranged from 0.4 to 1.4 mol C m−2 yr−1). The exported TOC was comprised both of material resident in the surface layer during late summer (resident TOC) and material newly produced during the spring bloom period (fresh TOC). Export of resident TOC ranged from 0.5 to 0.8 mol C m−2 yr−1, covarying with the maximum winter MLD. Export of fresh TOC varied from nil to 0.8 mol C m−2 yr−1. Fresh TOC was exported only after a threshold maximum winter MLD of ≈200 m was reached. In years with shallower mixing, fresh TOC export and net TOC production in the surface layer were greatly reduced. The decay rates of the exported TOC also covaried with maximum MLD. The year with deepest mixing resulted in the highest export and the highest decay rate (0.003 d−1) while shallow and low export resulted in low decay rates (0.0002 d−1), likely a consequence of the quality of material exported. The exported TOC supported oxygen utilization at ΔC : ΔO2 molar ratios ranging from 0.17 when TOC export was low to 0.47 when it was high. We estimate that exported TOC drove 15–41% of the annual oxygen utilization rates in the 100–400 m depth range. Finally, there was a lack of variability in the surface-layer TON signal during summer. The lack of a summer signal for net TON production suggests a small role for N2 fixation at the site. We hypothesize that if N2 fixation is responsible for elevated N : P ratios in the main thermocline of the Sargasso Sea, then the process must take place south of Bermuda and the signal transported north with the Gulf Stream system.

Particulate organic carbon mass distribution at the Bermuda Atlantic Time-series Study (BATS) site

Abstract Errors in total particulate organic carbon (total POC) measurements caused by particles settling in Niskin water samplers, loss of bacterial cells during filtration and undersampling of rare particles such as the diazotrophic cyanobacterium Trichodesmium spp. were investigated at the Bermuda Atlantic Time-series Study (BATS) site. Regular core samples of temperature, primary production, bacterial abundance, chlorophyll-a (Chl-a) and POC were collected at monthly intervals from 1991 to 1996. During this period of time, shorter investigations of particles settling in water samples (1991–1992), bacterial cells lost during filtration (1992–1993), and Trichodesmium abundance (1995–1996) were performed at the BATS site. The BATS site shows striking seasonal patterns in hydrography and phytoplankton primary productivity, with a strong maximum immediately following the deep winter mixing of the water column. Following the peak in primary production, bacterial abundance showed only slightly elevated levels in spring. Maxima of Chl-a and POC also were associated with the primary production peaks, but these particle concentrations became less pronounced through summer and fall. An average of 26% of total POC collected in Niskin water bottles settled below the spigot before it could be sampled. An average of 47% of all bacterial cells passed the nominal pore size of a Whatman GF/F filter, and total POC measurements generated from GF/F filtered seawater samples had to be corrected for this loss. The average integrated stocks of total POC in the upper 65 m of the water column was 32% pigmented phytoplankton, 15% microheterotrophs, 54% other detrital matter (32 : 15 : 54). Phytoplankton C equaled bacterial C in the 65–135 m depth range (16 : 19 : 65), but phytoplankton C was virtually non-existent deeper than 135 m (2 : 14 : 74). Bacterial C biomass was higher than phytoplankton in surface waters outside the spring bloom period, but carbon not accounted for by phytoplankton and bacteria (other C) showed an overall dominance throughout the year. Uncorrected, suspended POC collected on GF/F filters (POCSW) was nearly equal to the sum of phytoplankton C and bacterial C alone, and hence, the other C fraction of total POC was largely generated by the addition of settling particles (POCDreg). Seasonal occurrences of rare particles such as Trichodesmium colonies in surface waters in late summer may account for as much as 17–56% of total POC. Settling particles and Trichodesmium colonies, seldom included in POC estimates from temperate and tropical regions, constituted more than half of total POC measured in surface waters at BATS.

DMSP and DMS dynamics and microzooplankton grazing in the Labrador Sea: application of the dilution technique

We adapted the dilution technique to study microzooplankton grazing of algal dimethylsulfoniopropionate (DMSP) vs. Chl a, and to estimate the impact of microzooplankton grazing on dimethyl sulfide (DMS) production in the Labrador Sea. Phytoplankton numbers were dominated by autotrophic nanoflagellates in the Labrador basin, but diatoms and colonial Phaeocystis pouchetii contributed significantly to phytomass at several high chlorophyll stations and on the Newfoundland and Greenland shelfs. Throughout the region, growth of algal Chl a and DMSP was generally high (0.2–1 d − 1), but grazing rates were lower and more variable, characteristic of the early spring bloom period. Production and consumption of Chl a vs. DMSP followed no clear pattern, and sometimes diverged greatly, likely because of their differing distributions among algal prey taxa and size class. In several experiments where Phaeocystis was abundant, we observed DMS production proportional to grazing rate, and we found clear evidence of DMS production by this haptophyte following physical stress such as sparging or filtration. It is possible that grazing-activated DMSP cleavage by Phaeocystis contributes to grazer deterrence: protozoa and copepods apparently avoided healthy colonies (as judged by relative growth and grazing rates of Chl a and DMSP), and grazing of Phaeocystis was significant only at one station where cells were in poor condition. Although we hoped to examine selective grazing on or against DMSP-containing algal prey, the dilution technique cannot differentiate selective ingestion and varying digestion rates of Chl a and DMSP. We also found that the dilution method alone was poorly suited for assessing the impact of grazing on dissolved sulfur pools, because of rapid microbial consumption and the artifactual release of DMSP and DMS during filtration. Measuring and understanding the many processes affecting organosulfur cycling by the microbial food web in natural populations remain a technical challenge that will likely require a combination of techniques to address.

Trophic efficiency of the planktonic food web in a coastal ecosystem dominated by Phaeocystis colonies

The trophic efficiency of the planktonic food web in the Phaeocystis-dominated ecosystem of the Belgian coastal waters was inferred from the analysis of the carbon flow network of the planktonic system subdivided into its different trophodynamic groups. A carbon budget was constructed on the basis of process-level field experiments conducted during the spring bloom period of 1998. Biomass and major metabolic activities of auto- and heterotrophic planktonic communities (primary production, bacterial production, nanoproto-, micro- and mesozooplankton feeding activities) were determined in nine field assemblages collected during spring at reference station 330. In 1998, the phytoplankton spring flowering was characterised by a moderate diatom bloom followed by a massive Phaeocystis colony bloom. Phaeocystis colonies, contributing 70% to the net primary production, escaped the linear food chain while the early spring diatom production supplied 74% of the mesozooplankton carbon uptake. The rest of mesozooplankton food requirement was, at the time of the Phaeocystis colony bloom, partially fulfilled by microzooplankton. Only one-third of the microzooplankton production, however, was controlled by mesozooplankton grazing pressure. Ungrazed Phaeocystis colonies were stimulating the establishment of a very active microbial network. On the one hand, the release of free-living cells from ungrazed colonies has been shown to stimulate the growth of microzooplankton, which was controlling 97% of the nanophytoplankton production. On the other hand, the disruption of ungrazed Phaeocystis colonies supplied the water column with large amounts of dissolved organic matter available for planktonic bacteria. The budget calculation suggests that ungrazed colonies contributed up to 60% to the bacterial carbon demand, while alternative sources (exudation, zooplankton egestion and lysis of other organisms) provided some 30% of bacterial carbon requirements. This suggests that the spring carbon demand of planktonic bacteria was satisfied largely by autogenic production. The trophic efficiency was defined as the ratio between mesozooplankton grazing on a given source and food production. In spite of its major contribution to mesozooplankton feeding, the trophic efficiency of the linear food chain, restricted to the grazing on diatoms, represented only 5.6% of the available net primary production. The trophic efficiency of the microbial food chain, the ratio between mesozooplankton grazing on microzooplankton and the resource inflow (the bacterial carbon demand plus the nanophytoplankton production) amounted to only 1.6%. These low trophic efficiencies together with the potential contribution of ungrazed Phaeocystis-derived production to the bacterial carbon demand suggest that during spring 1998 most of the Phaeocystis-derived production in the Belgian coastal area was remineralised in the water column.

Changes in the elemental composition of Asterionella formosa during the diatom spring bloom

Changes in the elemental composition of the diatom Asterionella formosa within mixed phytoplankton samples were determined over the spring bloom period using energy dispersive X-ray microanalysis. Using a 10 kV electron microprobe, X-ray information from the top 1-2 µm of the cell revealed overall mean concentrations of: Si (4636 mmol kg -1 dry wt), P (82), S (54), Cl (71) K (94) and Ca (90). Concentrations of all elements showed wide variation within each date sample, with unimodal frequency distributions approximating to a Normal distribution. Correlation of the entire data set demonstrated clear statistical associations between elements, including Si, P and K. Uptake of Si during the course of the diatom bloom led to a major fall in lake water concentration (1.0 to 0.07 mg l -1 ), which correlated with a decrease in the mean cell Si concentration (6735 to 3107 mmol kg -1 dry wt) during the final phase of the bloom. Mean cell concentrations of P and K also showed marked decreases with time, in close parallel with cell Si. These changes in P and K were attributed to the high level of internal correlation with Si and not to any significant decrease in P and K availability in the environment.

Coccolithophore export production, species composition, and coccolith-CaCO 3 fluxes in the NE Atlantic ( [formula omitted] and [formula omitted

Coccolithophores were examined in two sediment traps, deployed for one year (April 1989 to April 1990) at approximately 1 km water depth, in the subtropical NE Atlantic at 34° N 21° W (station NABE-34) and in the temperate NE Atlantic 48° N 21° W (station NABE-48) as part of the JGOFS North Atlantic Bloom Experiment (NABE). At both stations, maximum coccolith and coccosphere fluxes were recorded during local spring bloom periods. The average coccolith and coccosphere fluxes at NABE-34 were 1.12×10 9 m −2 d −1 and 4.90×10 6 m −2 d −1 , respectively. At this station coccoliths from 51 taxa were identified. A marked seasonal change was noticed in relative abundances of Emiliania huxleyi and deep photic zone species: E. huxleyi dominated during spring, while in late autumn the coccolith assemblage was dominated by Florisphaera profunda and the coccosphere assemblage by G. flabellatus and Algirosphaera spp.. Emiliania huxleyi was the most abundant species in the overall coccolith and coccosphere assemblages with 69% and 64%, respectively. At NABE-48, the average daily fluxes were significantly lower, with 3.88×10 8 coccoliths m −2 d −1 and 8.45×10 5 coccospheres m −2 d −1 , and only 36 taxa were recorded in the trap samples. Emiliania huxleyi was the dominant species in the coccolith assemblage throughout the year with 72%, and showed maximum fluxes during spring 1990. Coccolithus pelagicus exhibited a distinct seasonal pattern, with maximum fluxes in early June 1989, probably related to the development of a mesoscale cyclonic eddy in the vicinity of the trap site. Holococcolithophore fluxes were highest during maximum sea surface temperatures in summer. The coccosphere assemblage was dominated by Gephyrocapsa spp., Syracosphaera spp., and E. huxleyi. Estimated CaCO 3 fluxes of coccoliths, coccospheres, and calcareous dinophytes were compared with the CaCO 3 content in the fine (<32 μm) fraction. The annual mass estimated CaCO 3 flux of coccoliths and coccospheres was 5.1 g m 2 yr at NABE-34 and 2.7 g m 2 yr at NABE-48, and that of calcareous dinophytes 0.9 and 0.1 g m 2 yr , respectively. These summed mass estimated values contributed on average only 55% at NABE-34 and 60% at NABE-48 to the fine fraction CaCO 3.

Phytoplanktonic and Bacterial Carbon Pools and Productivities in the Gerlache Strait, Antarctica, during Early Austral Spring.

Abstract Phytoplankton and bacterial biomass and productivities were investigated at four depths in the upper 500 m of the water column in the Gerlache Strait, Antarctica, during the prebloom period of early austral spring, from October 13 to November 4, 1995. The concentrations of all carbon pools were low, with the total particulate organic carbon (POC) concentration averaging 1.9 +/- 0.9 µM. Bacterial, protozoan, and phytoplankton carbon accounted for 21% of the total POC, indicating that detritus or unenumerated organisms comprised the bulk of the POC during this period. Larger zooplankton or protozoa, such as ciliates, may account for this difference, since microzooplankton can represent a significant fraction of the total microbial biomass. Primary and bacterial secondary production rates were also low, less than 300 and 30 ng C L(-1) h(-1), respectively. However, when production was normalized to either chlorophyll or bacterial cell number, rates were similar to those recorded during the spring bloom periods. This indicates that the cells were metabolically active during the prebloom period. Chlorophyll specific primary production averaged over the upper 80 m of the water column was 1.28 +/- 0.84 µg C µg chl(-1) h(-1), whereas the mean bacterial specific growth rate over the same depth interval was 0.34 +/- 0.24 d(-1). The overall production rates were low only because of the low abundance of cells during the prebloom period. When the site was reoccupied the following year, all measures of biomass and productivity were higher [36], emphasizing the large interannual variability in the Gerlache Strait.http://link.springer-ny.com/link/service/journals/00248/bibs/38n3p296.html</hea

Environmental Factors Affecting the Occurrence and Production of the Spring Phytoplankton Bloom in Funka Bay, Japan

The concentration of nutrients was measured during the spring phytoplankton bloom in Funka Bay over a 5-year period (1988–92). During the winter mixing period, nutrient concentrations were similar in every year except in 1990 when a high concentration of silicate was observed. There was interannual variation in the onset of the bloom, presumably depending on the stability of the water column. The bloom developed in early March when the Oyashio water (OW), which has a lower density than the existing winter water, flowed into the bay and the pycnocline formed near the bottom of the euphotic zone. In this case, high chl a was found only in the euphotic zone and nutrient utilization was limited to this zone. In the year when the inflow of OW was not observed by April, the bloom took place at the end of March without strong stratification and high chl a was found in the whole water column, accompanied by a decrease in nutrients. Interannual differences were found not only at the beginning of the decrease, but also in the thickness of the layer which showed a decrease in nutrients. Primary production from the beginning to the end of the spring bloom was estimated from the nutrient budget before and after the spring bloom. The integrated production over the spring bloom period ranged from 25 to 73 g C m-2, which accounts for 19–56% of the annual production in this bay. We found that the timing of the bloom was strongly dependent on the inflow of OW, but the amount of production was not clearly related to this timing.

Formula omitted] composition of marine dissolved organic carbon

The stable isotopic composition of marine dissolved organic carbon (DOC) was measured with a high temperature, sealed tube combustion technique. The δ 13 C values of DOC ( DO 13 C) were approximately −22‰ for all samples that were collected (1) in a monthly survey conducted in Woods Hole Harbor, (2) in a spatial survey across Georges Bank during a spring bloom period, and (3) in depth profiles near Bermuda, Georges Bank and in the eastern Equatorial Pacific. The DO 13 C values were uniform in waters of varying DOC content, including low DOC deep waters and high DOC surface waters, indicating little overall isotopic fractionation during formation and degradation of marine DOC. The −22‰ DO 13 C values are similar to those observed for average marine particulate and sedimentary organic material, and exclude a large contribution from −27‰ terrestrial DOC to ocean pools.

Description of the oceanographic condition off Sanriku, northwestern Pacific, and its relation to spring bloom detected by the Ocean Color and Temperature Scanner (OCTS) images

We describe the oceanographic condition as observed by hydrographic data and phytoplankton spring bloom detected by OCTS images off Sanriku, northwestern Pacific, during the spring bloom period in 1997. The relationship between the two is discussed. OCTS images detected the bloom in early April in the coastal area around the Izu ridge north of the Kuroshio and the eastern coastal area of Hokkaido to the Oyashio front. The bloom areas were seen along the offshore Kuroshio Extension from the end of April, in the upstream region of the Oyashio south of the Kurile Islands, except for a part of coastal area from the end of May, and in the Kuroshio warm-core ring 93A (KWCR 93A) from early June. The temperature difference between the surface and subsurface layer is used as a stratification index. This was large in the upstream region of the Oyashio south of the Kurile Islands and KWCR 93A from early June. Previous research has pointed out that the spring bloom usually corresponds to the development of stratification in the water column due to seasonal warming. In addition to that, we suggest that the transportation of water containing a high chlorophylla concentration by advection due to strong currents, like the Kuroshio and the Oyashio, is important for the formation of an area of high chlorophylla concentration. These results indicate that the OCTS images are useful for a knowledge of the distribution and the change of chlorophylla concentration in the northwestern Pacific region.

Copepod egg production rates in the Pomeranian Bay (Southern Baltic Sea) as a function of phytoplankton abundance and taxonomic composition

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 174:183-195 (1998) - doi:10.3354/meps174183 Copepod egg production rates in the Pomeranian Bay (Southern Baltic Sea) as a function of phytoplankton abundance and taxonomic composition Katrin Schmidt*, Paul Kähler, Bodo von Bodungen Institut für Ostseeforschung an der Universität Rostock, Seestraße 15, D-18119 Rostock, Germany *E-mail: katrin.schmidt@io-warnemuende.de ABSTRACT: The copepod community of the Pomeranian Bay, in the outer part of the Oder Estuary (Southern Baltic Sea), is dominated by Acartia bifilosa Giesbrecht in winter and spring and by A. tonsa Dana in autumn. During summer both species co-occur. The egg production of these species was studied in 1994/1995. Rates (eggs female-1 d-1) were found to vary both seasonally and spatially. In winter, egg production rates of A. bifilosa were low, but showed a positive response to increasing chlorophyll a concentrations. During the late phase of the spring bloom (dominated by the diatom Skeletonema costatum), egg production of A. bifilosa was clearly higher than in winter, while water temperature remained at a low level. Phytoplankton concentrations during the spring bloom varied, but egg production rates were uniform all over the bay, suggesting production was not food limited. Length-specific weight and lipid content indicate that females were in good physiological condition. During summer and autumn, both high and very low egg production rates were observed for both species. The relation between egg production rate and chlorophyll a concentration was negative. The analysis of the phytoplankton composition in summer suggested that a high proportion of dinoflagellates was beneficial for egg production whereas high proportions of cyanobacterial colonies and filaments had negative effects. Except during the spring bloom period, the egg production of Acartia spp. in the Pomeranian Bay was limited by the amount and quality of phytoplankton. KEY WORDS: Acartia spp. · Egg production · Phytoplankton · Food quality · Pomeranian Bay Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 174. Publication date: November 26, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.