SW Coast Of Finland Research Articles

Contribution of nanoprotists to metazooplankton diet in a mesocosm experiment in the coastal northern Baltic

Grazing by a metazooplankton community on nanoprotists <10 (JLOT was studied four times during a 21 day enclosure experiment carried out off the SW coast of Finland in late summer. During the study, the pelagic community was manipulated through nutrient enrichment (N + P) and through predation by stickleback fry. Grazing experiments were conducted in the laboratory using 5 \im pre- filtered, 3H-labelled nanoplankton as tracer food. Grazing by mesozooplankton (Meso) and metazoan microplankton (Micro), screened through 140 and 100 |xm mesh, was studied. Owing to enrichment effects and weak predation control by fish, the biomass of Meso and Micro increased during the study period. Meso biomass consisted mostly of the copepod Eurylemora affinis and the cladoceran Bosmina longispina maritima, and Micro biomass of copepod nauplii NIII-NVI. The community clear- ance rate of Meso usually exceeded that of Micro when feeding on nanoprotists. The opposite was found for the biomass-specific clearance rate, revealing nanoprotists to be a more important food source for Micro than for Meso. Metazooplankton were not able to control nanoprotists, because Meso and MicTO were estimated to remove on average 4 and 2% of nanoprotozoan biomass daily. When inte- grated through the study period, grazing on nanoprotists could meet 5 and 17% of the carbon need for Meso and Micro, 3 and 12% of their production being estimated to consist of bacterial carbon trans- ferred by nanoprotists. Micro were estimated to be more closely linked to the microbial food web than Meso, suggesting that the trophic position of copepods changes slightly during their maturation from nauphi to larger copepodites.

Urea uptake kinetics of a midsummer planktonic community on the SW coast of Finland

Urea uptake kinetics of a midsummer planktonic community on the SW coast of Finland

Seasonal and long-term variations in the body size of planktonic copepods in the northern Baltic Sea

Seasonal and long-term variations in the body size of planktonic copepods were studied in the northern Baltic Sea. The influence of temperature, salinity and phytoplankton concentration to the body size of Eurytemora affinis, Acartia bifilosa and Limnocalanus macrurus (Calanoida) was examined at three sea areas, differing in their hydrographical and trophic conditions (an archipelago area and an enclosed bay on the SW coast of Finland in 1992 and at an open sea station in the Gulf of Bothnia in 1991). There was an inverse relationship between copepod body length and temperature, while there was a direct effect of phytoplankton concentration. According to multiple regression analysis, the relative importance of these factors varied according to species, developmental stage and study area. In the archipelago area, copepod body size was mainly determined by temperature, while in the open Gulf of Bothnia, phytoplankton concentration was usually more important. Interannual variation in the summer body length of E. affinis and A. bifilosa was examined using samples collected over 18 years (1967 to 1984) in the archipelago area. In this analysis, the inverse relationship between water temperature and copepod body size disappeared; in E. affinis the average female length correlated positively with summer temperature. We suggest that the length and timing of the study period greatly influence the investigator's view of the factors regulating copepod body size.

Nitrate and ammonium depletion rates and preferences during a Baltic spring bloom

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 120:123-133 (1995) - doi:10.3354/meps120123 Nitrate and ammonium depletion rates and preferences during a Baltic spring bloom Tamminen, T. Nitrate and ammonium depletion potential of the planktonic community was studied during a spring bloom off the SW coast of Finland in the Baltic Sea. Depletion rates were measured after nutrient enrichments with different concentrations and combinations of NO3, NH4 and PO4. Depletion kinetics, N source preferences, mutual inhibition, utilization efficiency and P stimulation of N depletion were estimated. During the bloom peak, the community showed a depletion potential over 24 h equivalent to the total wintertime accumulation of inorganic nitrogen. A clear succession in N source preferences, mutual inhibition and utilization efficiency illustrated the shift from NO3 to NH4 as the basis for nitrogenous nutrition of the community. The succession of these potential qualities was gradual, in sharp contrast to the abrupt depletion of NO3 from the water column and to profound changes in the species composition of the phytoplankton community. This gradual succession allowed the community to effectively utilize both NO3 and NH4 as N sources according to their availability. The relative proportions of new and regenerated production seem therefore to be regulated mainly by relative supply rates of NO3 through physical transport and NH4 through mineralization processes within the community, while inherent preferences of the community play a subordinate role. Phytoplankton . Nitrogen sources . Depletion rate . Preference . Inhibition . Spring bloom . Baltic Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 120. Publication date: April 20, 1995 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1995 Inter-Research.

Contamination of sediment trap fluxes by vertically migrating phototrophic micro-organisms in the coastal Baltic Sea

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 122:45-58 (1995) - doi:10.3354/meps122045 Contamination of sediment trap fluxes by vertically migrating phototrophic micro-organisms in the coastal Baltic Sea Heiskanen AS Sedimentation rates of phytoplankton and particulate organic carbon (POC) were studied in the northern Baltic Sea, SW coast of Finland, during the spring bloom and early summer periods in May and June 1988. Sediment traps were moored at 15 and 30 m depths, and the cylinders were either preserved with formaldehyde (F) or remained as unpreserved control cylinders (C). The phytoplankton spring bloom in May was dominated by motile dinoflagellates. Due to the high abundance and vertical migration of the chain-forming dinoflagellate Peridiniellacatenata, the POC fluxes measured by the F-cylinders were, on average overestimated by 12%, and at most by 32% during the spring period. Between 3 and 12% of the P. catenata population was estimated to migrate daily below 15 m depth; part of the population also reached 30 m depth. Another migrating phototrophic organism present in the water column was the ciliate Mesodiniumrubrum. Generally, a larger fraction of the M. rubrum population (2 to 26%) migrated, but they did not contaminate the measurements to the same degree as P. catenata (&LT3% of total POC fluxes) due to their lesser abundance in the water column. In June, Eutreptiella sp. (Euglenophyceae) had significantly higher cell numbers in the F- than in the C-cylinders. They were estimated to contaminate the POC fluxes up to 13% at 15 m depth (F-cylinder). The difference in the Eutreptiella cell numbers between the 2 treatments could have been partly due to increased copepod grazing rates inside the C-cylinders (up to 90% of the total difference if they fed on phytoflagellates only). Contamination caused by the total apparent vertical migration of P. catenata, M. rubrum and Eutreptiella sp. accounted for 17 and 12%, on average, of the total POC sedimentation (F-cylinders) at 15 and 30 m depths, respectively. This study indicates that vertical migration of the phototrophic micro-organisms can significantly bias sediment trap measurements in shallow coastal areas where sediment traps are often deployed within the vertical range of the migrating microplankton (i.e. above 30 to 40 m). Sediment traps · Sedimentation · Preservation · Swimmer contamination · Vertical migration · Dinoflagellates · Mesodiniumrubrum · Eutreptiella sp. Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 122. Publication date: June 15, 1995 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1995 Inter-Research.

Mesozooplankton resting eggs in the Baltic Sea: identification and vertical distribution in laminated and mixed sediments

Benthic resting eggs of rotifers, cladocerans and calanoid copepods were studied at two sites with different hydrographical and sediment properties off the SW coast of Finland, the northern Baltic Sea between 1991 and 1993. Vertical distribution of the resting eggs in the sediment was studied down to 10 cm depth, and hatching of the eggs extracted from different 1-cm thick sediment layers was experimentally tested. The larvae of eight mesozooplankton taxa emerged from the eggs: Calanoida (mostlyAcartia bifilosa), cladoceransBosmina spp.,Daphnia spp.,Evadne nordmanni, andPodon spp. (mostlyP. polyphemoides), and rotifersSynchaeta spp.,Keratella spp. andAsplanchna priodonta. Some calanoid and cladoceran eggs hatched after 7 mo storage of the sediment at 3°C. A few calanoid and cladoceran eggs hatched from the 8 to 10 cm deep sediment layer. Their age, estimated by means of137Cs analysis, was ca. 8 to 10 yr. Vertical distribution of the benthic eggs reflected the different sediment structures of the study sites. The eggs of all zooplankton taxa were more stratified in the laminated sediment than in the disturbed sediment. We suggest that the intensity of deep water mixing is the key factor for regulating the vertical distribution and hatching probability of mesozooplankton resting eggs, since it largely determines the stratification of the sedimenting material, distribution of oxygen within the sediment, and the living conditions of benthic animals causing bioturbation.

Annual variation in the abundance and size of heterotrophic nanoflagellates on the SW coast of Finland, the Baltic Sea

Annual variation in the abundance and size of heterotrophic nanoflagellates on the SW coast of Finland, the Baltic Sea

Nutrient limitation and grazing control of the Baltic plankton community during annual succession

Nutrient limitation and grazing control of the planktonic community were studied in the northern Baltic Sea off the SW coast of Finland during the phytoplankton growth season of 1985. In situ experiments based on a 23 factorial design were performed in mesocosm enclosures on 10 occasions. The manipulations used included phosphorus (PO43−) and nitrogen (NH4+) additions and the removal of metazooplankton by 100‐µm prefiltration. In each experiment, the responses of phytoplankton, bacterioplankton, heterotrophic nanoflagellates, and protozooplankton were followed for 2 d. Orthogonal multiple regression analysis was used to reveal which manipulations had statistically significant effects.Nitrogen was found to be the basic limiting nutrient for phytoplankton throughout the productive season. During early summer, only the combined addition of P and N evoked a clear increase in the growth of phytoplankton. In general, bacterial productivity was not highly affected by the manipulations. In summer the removal of metazooplankton caused a rapid increase in the amount of protozooplankton in the units with 100‐µm prefiltration or prefiltration combined with N addition. In the absence of metazooplankton, the nutrient‐induced increase in primary productivity was channeled to protozooplankton, whose growth in the units where metazooplankton was present was severely limited by food competition or by direct metazooplankton grazing.

Fate of a phytoplankton spring bloom: sedimentation and carbon flow in the planktonic food web in the northern Baltic

During the spring bloom in 1988, the dynamics of planktonic carbon flow were studied weekly in the euphotic layer in the northern Baltic. The spring bloom developed after the formation of a s l~gh t vertical salinity gradient near the surface at the end of April, and a peak in phytoplankton primary productivity and biomass (dominated by the dinoflagellate Peridiniella catenata) was reached about 1 wk later. The biomass of all heterotrophic compartments, especially that of bactena and copepods, increased strongly durlng the peak and declining phases of the algal bloom, showing that their success was closely linked with the bloom. During the whole bloonl period, the integral pnmary production (I4C incorporation) was 45.5 g C m-', and 'new' (NO<-N-based) production contributed about 80% of this value. The rotifers-copepods grazing chain and the bacteria-heterotrophic nanoflagellates-ciliates 'microbial loop' consumed directly about the same amount (3.5 g C m-') of phytoplankton carbon. Algae accounted for 64% of the total carbon consumption of zooplankton. Sedimentation corresponded to 72% of the primary production. The sum of algal biomass increase and loss factors (exudation, grazing and sedimentation) was 94% of the integral primary production, which supports our conclusion that there is a strong imbalance between primary and secondary production in the vernal planktonic food web off the SW coast of Finland.

Horizontal distribution of photo- and heterotrophic microorganisms on the coastal area of the northern Baltic Sea—a case study

The horizontal distribution of bacteria (BACT), bacterial production (FDC), picoplanktonic cyanobacteria (CYANO), and photosynthetic (PNF) as well as heterotrophic (HNF) nanoflagellates was studied at the end of June on the SW coast of Finland, the Baltic Sea. Samples were taken at 0 and 10 m depths from three transects ∼500 and 800 m apart. The distance between sampling points was ∽20 m. Cell counts of BACT, CYANO, PNF, HNF and the FDC showed 3- to 5-fold deviations in the whole data set. Differences between the duplicate counts within the subsamples were 10–20%. Within the transects, the maximum values were 1.2–3.0 times higher than the minimum values. Differences between the transects were statistically significant for all variables except FDC. Deviations in cell numbers between the surface and 10 m were quite irregular. but often statistically significant. In most cases, the organism groups did not correlate significantly with each other. The horizontal distribution of pelagic microbes was sufficiently uniform, on a meter scale. for one sampling point to give a reliable estimate of microbial densities in the area under investigation. The differences between the surface and the lower stratum of the mixed layer (10 m) were in most cases statistically significant.

Production of the benthic amphipodsPontoporeia affinisandP. femoratain a Baltic archipelago

Abstract The production dynamics of Pontoporeia affinis Lindström and P. femorata Kröyer (Crustacea, Am-phipoda) were studied in 1980 near Tvärminne, SW coast of Finland. The study areas were located in the outer archipelago at depths of 21–25 and 26–30 m and in the sea zone at 46 m.p In P. affinis abundance declined from 12 000-17 000 ind. m-2 in May to 800–3000 ind. m-2 in November, but the maximum biomass of 5–8 g AFDM m-2 was attained in August. In the archipelago the daily production values were highest in June-July and biomass losses in July-August. In the sea zone production peaked in June but was considerable until autumn, and biomass losses increased toward autumn. Annual production to biomass ratios (P/B) declined from 2.9 to 1.3 with increasing depth. This decrease was most probably due to the lower temperature and food competition in the denser population of Ponloporeia at greater depths. The 0 + age group had the highest P/B ratio (4.8-3.4) and in the two archipelago areas about as high an annual production as the 1 + age group. In the sea zone production of the 1+ and 2+ age groups by far exceeded that of the 0+ age group. In P. femorata, present only in the sea zone, total abundance remained at a steady level of about 2500 ind. m-2 throughout the study period. The maximum biomass, 3 g AFDM m-2, was attained in September and was mainly composed of the 1 + and 2 + age groups. In all age groups maximum daily production values were attained in October-November. Daily biomass losses also peaked in the autumn. The annual P/B ratio for the entire population was 2.1, but the highest P/B ratio (3.4) was obtained for those young released in the spring.

Seasonal growth of the benthic amphipodsPontoporeia affinis andP. femorata in a Baltic archipelago in relation to environmental factors

An intensive field study of three depth zones in 1980 revealed different seasonal patterns of growth in the deposit-feedingPontoporeia affinis Lindstrom andP. femorata Kroyer (Crustacea, Amphipoda) in the northern Baltic Sea, SW coast of Finland. The study areas were situated in the outer archipelago at depths of 21 to 25 m and 26 to 30 m and in the sea zone at 46 m. InP. affinis growth rates decreased with increasing depth, but the same seasonal pattern was evident at all depths: growth began in spring, increased to a maximum in early or midsummer, and decreased again or ceased altogether by autumn. In the archipelago the 1 + age group attained its maximum growth rate in May–June and the 0 + age group clearly later, in June–July. InP. femorata the growth rates of all age groups were more even, having only slight peaks in summer and autumn. The seasonal variation in growth ofPontoporeia spp. was not directly dependent on sedimentation of the spring phytoplankton bloom, but was more closely connected with seasonality of temperature and total benthic metabolism. Because estimates of annual food consumption byPontoporeia spp. exceeded bacterial and meiofaunal production, these species must have derived the majority of their energy demands from dead organic detritus. BothPontoporeia species are probably strictly food-limited in the area. The cessation of growth seemed to coincide with the approach of a plateau of total biomass, suggesting food competition. Different timing of growth between the age groups ofP. affinis suggests differences in sources or utilization of food; differences betweenP. affinis adP. femorata may indicate interspecific competition or different food.

Excretion of organic carbon by phytoplankton:its relation to algal biomass, primary productivity and bacterial secondary productivity in the Baltic Sea

In 1985, algal biomass, primary productivity (incorporation of 14C, acidified water sample), excretion of organic matter (exudation), and bacterial secondary productivity were followed off the SW coast of Finland, in the nothern Baltic Sea. Molecular size fractionation of the dissolved (net) excreted organic carbon pool (EOC,) was carried out by gel filtration. During the phytoplankton growth season the mean algal standing stock was 0.54 g C m-', and picoalgae ( 10 000 daltons) were also observed. On the basis of the size of the excreted compounds, exudation probably took place via mediated transport across the algal cell membrane, rather than via passive leakage from the cell.

Protozoan grazing on planktonic bacteria and its impact on bacterial population

Grazing by heterotrophic nanoflagellates and < 100 Fm microzooplankton on planktonic bacteria was followed during a mesocosm experiment in the Baltic Sea between 23 July and 12 August 1988 on the SW coast of Finland. During the succession of the planktonic community in one mesocosm, 4 grazing experiments were run with a size-fractionation technique. The size fractions used were: < 1 pm (bacterioplankton), < 5 pm (bacteria and heterotrophic nanoflagellates), and < 100 pm (bacteria, heterotrophic nanoflagellates and ciliates). Clearance rate of < 5 pm flagellates was 0.6 to 5.3 nl flag.-' h-' Grazing in the < 5 pm size fraction was 34 to 134 % of grazing in the < 100 pm fraction. The <S pm and < 100 pm protozoa harvested hourly on average 75 and 90 % of bacterial production, respectively. Nonetheless, heterotrophic nanoflagellates could not satisfy their carbon demand from bacteria. Grazing by protozoa altered bacterial size distribution, and reduced bacterial cell number and production. When the water temperature was ca 20°C, < 100 pm microzooplankton could consume about 50 to 100 % of flagellate standing stock daily. During the 3 wk mesocosm experiment, protozoan clearance rate fluctuated in the < 5 and < 100 pm filtrates by a factor of 9 and 3, respectively. A fall of water temperature from 18 to 14°C was the main factor affecting the activity of the microbial community in the mesocosm.