Browsing by Subject "hydrobiologia"

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  • Kuparinen, Jorma; Lahti, Kirsti; Mäkelä, Ari; Rekolainen, Seppo; Talsi, Tuija; Tamminen, Timo; Virtanen, Anneli; Uusi-Rauva, Antti (Vesihallitus. National Board of Waters, 1984)
    Vesientutkimuslaitoksen julkaisuja 56, 35-41
    Vesistöjen bakteeriplanktonin aktiivisuuden määritys yhden substraattipitoisuuden menetelmällä: käytännön suoritus
  • Suikkanen, Sanna (Helsingin yliopisto, 2008)
    Eutrophication and enhanced internal nutrient loading of the Baltic Sea are most clearly reflected by increased late-summer cyanobacterial blooms, which often are toxic. In addition to their toxicity to animals, phytoplankton species can be allelopathic, which means that they produce chemicals that inhibit competing phytoplankton species. Such interspecific chemical warfare may lead to the formation of harmful phytoplankton blooms and the spread of exotic species into new habitats. This is the first report on allelopathic effects in brackish-water cyanobacteria. The experimental studies presented in this thesis showed that the filamentous cyanobacteria Anabaena sp., Aphanizomenon flos-aquae and Nodularia spumigena are capable of decreasing the growth of other phytoplankton species, especially cryptophytes, but also diatoms. The detected allelopathic effects are rather transitory, and some co-occurring species show tolerance to them. The allelochemicals are excreted during active growth and they decrease cell numbers, chlorophyll a content and carbon uptake of the target species. Although the more specific modes of action or chemical structures of the allelochemicals remain to be studied, the results clearly indicate that the allelopathic effects are not caused by the hepatotoxin, nodularin. On the other hand, cyanobacteria stimulated the growth of bacteria, other cyanobacteria, chlorophytes and flagellates in a natural phytoplankton community. In a long-term data analysis of phytoplankton abundances and hydrography of the northern Baltic Sea, a clear change was observed in phytoplankton community structure, together with a transition in environmental factors, between the late 1970s and early 2000s. Surface water salinity decreased, whereas water temperature and the concentration of dissolved inorganic nitrogen increased. In the phytoplankton community, the biomass of cyanobacteria, chrysophytes and chlorophytes significantly increased, and the late-summer phytoplankton community became increasingly cyanobacteria-dominated. In contrast, the biomass of cryptophytes decreased. The increased temperature and nutrient concentrations probably explain most of the changes in phytoplankton, but my results suggest that the possible effect of chemically mediated biological interactions should also be considered. Cyanobacterial allelochemicals can cause additional stress to other phytoplankton in the nutrient-depleted late-summer environment and thus contribute to the formation and persistence of long-lasting cyanobacterial mass occurrences. On the other hand, cyanobacterial blooms may either directly or indirectly promote the growth of some phytoplankton species. Therefore, a further increase in cyanobacteria will probably shape the late-summer pelagic phytoplankton community by stimulating some species, but inhibiting others.
  • Lindén, Eveliina (Helsingin yliopisto, 2006)
    Predation is an important source of mortality for most aquatic animals. Thus, the ability to avoid being eaten brings substantial fitness benefits to individuals. Predator detection abilities and antipredator behaviour were examined in various planktivores, i.e. the littoral mysids Neomysis integer and Praunus flexuosus, three-spined stickleback Gasterosteus aculeatus larvae, pelagic mysids Mysis mixta and M. relicta, and the predatory cladoceran Cercopagis pengoi, with cues from their respective predators European perch Perca fluviatilis and Baltic herring Clupea harengus membras. The use of different aquatic macrophytes as predation refuges by the littoral planktivores was also examined. All pelagic planktivores and stickleback larvae were able to detect the presence of their predator by chemical cues alone. The littoral mysids N. integer and P. flexuosus responded only when chemical and visual predator cues were combined. The responses of stickleback larvae were stronger to the combined cues than the chemical cue alone. A common antipredator behaviour in all of the planktivores studied was decreased ingestion rate in response to predator cues. N. integer and stickleback larvae also decreased their swimming activity. Pelagic mysids and C. pengoi altered their prey selectivity patterns in response to predator cues. The effects of predator cues on the swarming behaviour of N. integer were examined. Swarming brings clear antipredator advantages to N. integer, since when they feed in a swarm, they do not significantly decrease their feeding rate. However, the swarming behaviour of N. integer was not affected by predation risk, but was instead a fixed strategy. Despite the presence or absence of predator cues, N. integer individuals attempted to associate with a swarm and preferred larger to smaller swarms. In studies with aquatic macrophytes, stickleback larvae and P. flexuosus utilized vegetation as a predation refuge, spending more time within vegetation when under predation threat. The two macroalgal species studied, bladderwrack Fucus vesiculosus and stonewort Chara tomentosa, were preferred by P. flexuosus, whereas Eurasian watermilfoil Myriophyllum spicatum was strongly avoided by N. integer and stickleback larvae. In fact, when in dense patches in aquaria, M. spicatum caused acute and high mortality (> 70%) in littoral mysids, but not in sticklebacks, whereas C. tomentosa and northern watermilfoil M. sibiricum did not. In contrast, only 2-4% mortality in N. integer was observed with intact and broken stems of M. spicatum in field experiments. The distribution of littoral mysids in different vegetations, however, suggests that N. integer avoids areas vegetated by M. spicatum.
  • Kuparinen, Jorma; Lahti, Kirsti; Talsi, Tuija; Tamminen, Timo; Virtanen, Anneli (Vesihallitus. National Board of Waters, 1984)
    Vesientutkimuslaitoksen julkaisuja 56, 26-34
    Bakteeriplanktonin glukoosinottoa kuvaavien kineettisten parametrien määritys yhden substraattipitoisuuden menetelmällä
  • Pertola, Sari (Helsingin yliopisto, 2006)
    In this thesis the role played by expansive and introduced species in the phytoplankton ecology of the Baltic Sea was investigated. The aims were threefold. First, the studies investigated the resting stages of dinoflagellates, which were transported into the Baltic Sea via shipping and were able to germinate under the ambient, nutrient-rich, brackish water conditions. The studies also estimated which factors favoured the occurrence and spread of P. minimum in the Baltic Sea and discussed the identification of this morphologically variable species. In addition, the classification of phytoplankton species recently observed in the Baltic Sea was discussed. Incubation of sediments from four Finnish ports and 10 ships ballast tanks revealed that the sediments act as sources of living dinoflagellates and other phytoplankton. Dinoflagellates germinated from all ports detected and from 90% of ballast tanks. The concentrations of cells germinating from ballast tank sediments were mostly low compared with the acceptable cell concentrations set by the International Maritime Organization s (IMO s) International Convention for the Control and Management of Ships Ballast Water and Sediments. However, the IMO allows such high concentrations of small cells in the discharged ballast water that the total number of cells in large ballast water tanks can be very high. Prorocentrum minimum occurred in the Baltic Sea annually but with no obvious trend in the 10-year timespan from 1993 to 2002. The species occurred under wide ranges of temperatures and salinities and the abundance of the species was positively related especially to the presence of organic nitrogen and phosphorus. This indicated that the species was favoured by increased organic nutrient loading and runoff from land and rivers. The cell shape of P. minimum varied from triangular to oval-round, but morphological fine details indicated that only one morphospecies was present. P. minimum also is, according to present knowledge, the only potentially harmful phytoplankton species that has recently expanded widely into new areas of the Baltic Sea.
  • Halmeenpää, Hanna; Niemelä, Pirjo; Alahuhta, Janne; Dvornikova, Natalya; Erkinaro, Heikki; Heikkinen, Kaisa; Kotov, Sergey; Masyk, Natalya; Meissner, Kristian; Riihimäki, Juha; Vuori, Kari-Matti; Zueva, Marina (North Ostrobothnia Regional Environment Centre, 2007)
    The Finnish Environment 28/2007
    The Kola River is situated in Northwestern Russia, Kola Peninsula, which is an area with about 70 year long history of copper and nickel mining and smelting. However, environmental effects on the Kola River, caused by industry and other human activities, are not studied thoroughly. Area of the Kola River basin is 3850 km2. The river flows 83 km from south to north and enters the Kola Bay of the Barents Sea in front of the Kola City. The Kola River is vital for the reproduction of salmon and it is also an important source of drinking water for about half a million people in the city of Murmansk and in the surrounding settlements. In the Kola Water Quality -project in years 2001–2004 one the main objectives was to define the ecological status of the Kola River. The Näätämöjoki River in northern Finland and Norway was surveyed as a reference area. This publication includes ecological studies carried out by North Ostrobothnia Regional Environment Centre (NOREC, Finland) and The Murmansk Areal Department for Hydrometeorology and Environmental Monitoring (MUGMS, Russia). Chapters concerning macroinvertebrate studies were written by Kristian Meissner (NOREC/SYKE). Studies on macrozoobenthos after federal Russian hydrobiological monitoring methods are grouped in separate chapters and were reported by Sergey Kotov (MUGMS). Chapters concerning fish communities were written by Heikki Erkinaro (NOREC, Finnish Game and Fisheries Research Institute). Diatom community analyses were reported by Hanna Halmeenpää and Pirjo Niemelä (NOREC). Chapters concerning hydromorphological state of the river (River Habitat Survey) were written by Janne Alahuhta (NOREC) and chapters on macrophyte survey by Juha Riihimäki (Finnish Environment Institute). Studies on metal concentrations in aquatic bryophytes were reported by Hanna Halmeenpää (NOREC) and Kari-Matti Vuori (Finnish Environment Institute). Chapters concerning bacterioplankton and phytoplankton were written by Natalya Masuk (MUGMS), chapters on zooplankton by Natalya Dvornikova (MUGMS). Chapters concerning physical and chemical water quality of the rivers Kola and Näätämöjoki were written by Marina Zueva (MUGMS) and Hanna Halmeenpää (NOREC). Hanna Halmeenpää and Pirjo Niemelä (NOREC) took the responsibility of editing the report and writing of common chapters. On grounds of the ecological studies, the Kola River can be divided into three separate areas. At the upper river sections (K2-K3) the ecological status ranged from good to moderate. Signs on nutrient and metal (copper, nickel) loading could be detected both in water quality and in aquatic organisms. The ecological status of the mid-section (K4-K8) of the Kola River basin ranged from good to high. No major human impact could be seen. The estuary section (K9-K12) of the Kola River represented the moderate ecological status. This was probably caused by small, heavily polluted tributaries (Varlamov, Medvegiy and Zemlanoy) draining organic load and nutrient rich waters into main flow and also by other anthropogenic loading along the lower river section. The ecological status of the reference river Näätämöjoki was high on grounds of all the biological parameters used in this study.
  • Lehtonen, Kari K. (Finnish Institute of Marine Research, 1997)
    Monographs of the Boreal Environment Research 7
  • Heiskanen, Anna-Stiina (Finnish Environment Institute, 1998)
    Monographs of the Boreal Environment Research 8
  • Piiparinen, Jonna (Helsingin yliopisto, 2011)
    The aim of this thesis was to study ecology of Baltic Sea ice from two perspectives. In the first two studies, sea-ice ecology from riverine-influenced fast ice to drift ice in the Bothnian Bay was investigated, whereas the last two studies focus on the sensitivity of sea-ice bacteria and algae to UVA examined in situ. The seasonal sea ice cover is one of the main characteristics of the Baltic Sea, and despite the brackish parental water, the ice structure is similar to polar ice with saline brine inclusions, the sea ice habitat. The decreasing seawater salinity from the northern Baltic Sea to the Bothnian Bay translates to decreasing brine volumes along the gradient, governing the size and community structure of the food webs in ice. However, the drift and fast ice in the Bothnian Bay may differ greatly in this sense, as drift ice may have been formed at more southern locations. Rafting and the formation of snow ice are common processes in the ice field of the Bothnian Bay. As evidenced in this thesis, rafting altered the vertical distribution of organisms and snow-ice formation provided habitable space in the better-illuminated, nitrogen-rich surface layer. The divergence between fast and drift ice became apparent at the more advanced stages, and chlorophyte biomass decreased from fast to drift ice, while the opposite held true for protozoan and metazoan biomass. The brine volumes affected the communities somewhat, and a higher percentage of flagellate species was generally linked to lower brine volumes, whereas chain-forming diatoms were mostly concentrated in layers with larger brine volumes. These results add to knowledge of the ecological significance of the ice cover lasting up to 7 months per year in this area. Sea-ice food webs are generally light-limited, but while increasing light irradiances typically enhance the primary production and further, the secondary production in sea ice, any increase in solar radiation also includes an increase in harmful UVA radiation. The Baltic Sea ice microbial communities were clearly sensitive to UVA and the responses were strongly linked to the earlier light history, as well as to the solar irradiances they were exposed to. The increased biomass of chlorophytes and pennate diatoms, when UVA was excluded, indicates that their normally minor contribution to the biomass in the upper layers of sea ice might be partly dictated by UVA. The effects of UVA on bacterial production in Baltic Sea ice mostly followed the responses in algal growth, but occasionally the exposure to UVA even enhanced the bacterial production. The dominant bacterial class, Flavobacteria, seemed to be UVA-tolerant, whereas all the Alpha-, Beta- and Gammaproteobacteria present in the surface layer showed UVA sensitivity. These results indicate that changes in the light field of ice may alter the community structure and affect the functioning of ice food webs, and are of importance when the effects of thinning of the ice cover are assessed.
  • Uronen, Pauliina (Helsingin yliopisto, 2007)
    This study deals with algal species occurring commonly in the Baltic Sea: haptophyte Prymnesium parvum, dinoflagellates Dinophysis acuminata, D. norvegica and D. rotundata, and cyanobacterium Nodularia spumigena. The hypotheses are connected to the toxicity of the species, to the factors determining toxicity, to the consequences of toxicity and to the transfer of toxins in the aquatic food web. Since the Baltic Sea is severely eutrophicated, the fast-growing haptophytes have potential in causing toxic blooms. In our studies, the toxicity (as haemolytic activity) of the haptophyte P. parvum was highest under phosphorus-limited conditions, but the cells were toxic also under nitrogen limitation and under nutrient-balanced growth conditions. The cellular nutrient ratios were tightly related to the toxicity. The stoichiometric flexibility for cellular phosphorus quota was higher than for nitrogen, and nitrogen limitation led to decreased biomass. Negative allelopathic effects on another algae (Rhodomonas salina) could be observed already at low P. parvum cell densities, whereas immediate lysis of R. salina cells occurred at P. parvum cell densities corresponding to natural blooms. Release of dissolved organic carbon from the R. salina cells was measured within 30 minutes, and an increase in bacterial number and biomass was measured within 23 h. Because of the allelopathic effect, formation of a P. parvum bloom may accelerate after a critical cell density is reached and the competing species are eliminated. A P. parvum bloom indirectly stimulates bacterial growth, and alters the functioning of the planktonic food web by increasing the carbon transfer through the microbial loop. Our results were the first reports on DSP toxins in Dinophysis cells in the Gulf of Finland and on PTX-2 in the Baltic Sea. Cellular toxin contents in Dinophysis spp. ranged from 0.2 to 149 pg DTX-1 cell-1 and from 1.6 to 19.9 pg PTX-2 cell-1 in the Gulf of Finland. D. norvegica was found mainly around the thermocline (max. 200 cells L-1), whereas D. acuminata was found in the whole mixed layer (max. 7 280 cells L-1). Toxins in the sediment trap corresponded to 1 % of DTX-1 and 0.01 % PTX-2 of the DSP pool in the suspended matter. This indicates that the majority of the DSP toxins does not enter the benthic community, but is either decomposed in the water column, or transferred to higher trophic levels in the planktonic food chain. We found that nodularin, produced by Nodularia spumigena, was transferred to the copepod Eurytemora affinis through three pathways: by grazing on filaments of small Nodularia, directly from the dissolved pool, and through the microbial food web by copepods grazing on ciliates, dinoflagellates and heterotrophic nanoflagellates. The estimated proportion of the microbial food web in nodularin transfer was 22-45 % and 71-76 % in our two experiments, respectively. This highlights the potential role of the microbial food web in the transfer of toxins in the planktonic food web.
  • Uronen, Pauliina (Finnish Environment Institute, 2007)
    Monographs of the Boreal Environment Research 28
    This study deals with algal species occurring commonly in the Baltic Sea: haptophyte Prymnesium parvum, dinoflagellates Dinophysis acuminata, D. norvegica and D. rotundata, and cyanobacterium Nodulariaspumigena. The hypotheses are connected to the toxicity of the species, to the factors determining toxicity, to the consequences of toxicity and to the transfer of toxins in the aquatic food web.Since the Baltic Sea is severely eutrophicated, the fast-growing haptophytes have potential in causing toxic blooms. In our studies, the toxicity (as haemolytic activity) of the haptophyte P. parvum was highest under phosphorus-limited conditions, but the cells were toxic also under nitrogen limitation and under nutrient-balanced growth conditions. The cellular nutrient ratios were tightly related to the toxicity. The stoichiometric flexibility for cellular phosphorus quota was higher than for nitrogen, and nitrogen limitation led to decreased biomass. Negative allelopathic effects on another algae (Rhodomonas salina) could be observed already at low P. parvum cell densities, whereas immediate lysis of R. salina cells occurred at P. parvum cell densities corresponding to natural blooms. Release of dissolved organic carbon from the R. salina cells was measured within 30 minutes, and an increase in bacterial number and biomass was measured within 23 h. Because of the allelopathic effect, formation of a P. parvum bloom may accelerate after a critical cell density is reached and the competing species are eliminated. A P. parvum bloom indirectly stimulates bacterial growth, and alters the functioning of the planktonic food web by increasing the carbon transfer through the microbial loop.Our results were the first reports on DSP toxins in Dinophysis cells in the Gulf of Finland and on PTX-2 in the Baltic Sea. Cellular toxin contents in Dinophysis spp. ranged from 0.2 to 149 pg DTX-1 cell-1 and from 1.6 to 19.9 pg PTX-2 cell-1 in the Gulf of Finland. D. norvegica was found mainly around the thermocline (max. 200 cells L-1), whereas D. acuminata was found in the whole mixed layer (max. 7 280 cells L-1). Toxins in the sediment trap corresponded to 1 % of DTX-1 and 0.01 % PTX-2 of the DSP pool in the suspended matter. This indicates that the majority of the DSP toxins does not enter the benthic community, but is either decomposed in the water column, or transferred to higher trophic levels in the planktonic food chain.We found that nodularin, produced by Nodularia spumigena, was transferred to the copepod Eurytemoraaffinis through three pathways: by grazing on filaments of small Nodularia, directly from the dissolved pool, and through the microbial food web by copepods grazing on ciliates, dinoflagellates and heterotrophic nanoflagellates. The estimated proportion of the microbial food web in nodularin transfer was 22-45 % and 71-76 % in our two experiments, respectively. This highlights the potential role of the microbial food web in the transfer of toxins in the planktonic food web.
  • Tamminen, Timo (Vesihallitus. National Board of Waters, 1984)
    Vesientutkimuslaitoksen julkaisuja 56, 11-20
    Michaelis-Menten -kinetiikan lineaarimuunnokset luonnon mikrobiyhteisöjen tutkimuksessa
  • Spilling, Kristian (Helsingin yliopisto, 2007)
    Increased anthropogenic loading of nitrogen (N) and phosphorus (P) has led to an eutrophication problem in the Baltic Sea, and the spring bloom is a key component in the biological uptake of increased nutrient concentrations. The spring bloom in the Baltic Sea is dominated by both diatoms and dinoflagellates. However, the sedimentation of these groups is different: diatoms tend to sink to the sea floor at the end of the bloom, while dinoflagellates to a large degree are been remineralized in the euphotic zone. Understanding phytoplankton competition and species specific ecological strategies is thus of importance for assessing indirect effects of phytoplankton community composition on eutrophication problems. The main objective of this thesis was to describe some basic physiological and ecological characteristics of the main cold-water diatoms and dinoflagellates in the Baltic Sea. This was achieved by specific studies of: (1) seasonal vertical positioning, (2) dinoflagellate life cycle, (3) mixotrophy, (4) primary production, respiration and growth and (5) diatom silicate uptake, using cultures of common cold-water diatoms: Chaetoceros wighamii, C. gracilis, Pauliella taeniata, Thalassiosira baltica, T. levanderi, Melosira arctica, Diatoma tenuis, Nitzschia frigida, and dinoflagellates: Peridiniella catenata, Woloszynskia halophila and Scrippsiella hangoei. The diatoms had higher primary production capacity and lower respiration rate compared with the dinoflagellates. This difference was reflected in the maximum growth rate, which for the examined diatoms range from 0.6 to 1.2 divisions d-1, compared with 0.2 to 0.3 divisions d-1 for the dinoflagellates. Among diatoms there were species specific differences in light utilization and uptake of silicate, and C. wighamii had the highest carbon assimilation capacity and maximum silicate uptake. The physiological properties of diatoms and dinoflagellates were used in a model of the onset of the spring bloom: for the diatoms the model could predict the initiation of the spring bloom; S. hangoei, on the other hand, could not compete successfully and did not obtain positive growth in the model. The other dinoflagellates did not have higher growth rates or carbon assimilation rates and would thus probably not perform better than S. hangoei in the model. The dinoflagellates do, however, have competitive advantages that were not included in the model: motility and mixotrophy. Previous investigations has revealed that the chain-forming P. catenata performs diurnal vertical migration (DVM), and the results presented here suggest that active positioning in the water column, in addition to DVM, is a key element in this species' life strategy. There was indication of mixotrophy in S. hangoei, as it produced and excreted the enzyme leucine aminopeptidase (LAP). Moreover, there was indirect evidence that W. halophila obtains carbon from other sources than photosynthesis when comparing increase in cell numbers with in situ carbon assimilation rates. The results indicate that mixotrophy is a part of the strategy of vernal dinoflagellates in the Baltic Sea. There were also indications that the seeding of the spring bloom is very important for the dinoflagellates to succeed. In mesocosm experiments dinoflagellates could not compete with diatoms when their initial numbers were low. In conclusion, this thesis has provided new information about the basic physiological and ecological properties of the main cold-water phytoplankton in the Baltic Sea. The main phytoplankton groups, diatoms and dinoflagellates, have different physiological properties, which clearly separate their life strategies. The information presented here could serve as further steps towards better prognostic models of the effects of eutrophication in the Baltic Sea.
  • Tamminen, Timo; Kuparinen, Jorma (Vesihallitus. National Board of Waters, 1984)
    Vesientutkimuslaitoksen julkaisuja 56, 3-10
    Vesistöjen bakteeriplanktonin aktiivisuuden mittauksesta radioaktiivisten merkkiaineiden avulla
  • Forsström, Laura Johanna (Helsingin yliopisto, 2006)
    Climate is warming and it is especially seen in arctic areas, where the warming trend is expected to be greatest. Arctic freshwater ecosystems, which are a very characteristic feature of the arctic landscape, are especially sensitive to climate change. They could be used as early warning systems, but more information about the ecosystem functioning and responses are needed for proper interpretation of the observations. Phytoplankton species and assemblages could be especially suitable for climate-related studies, since they have short generation times and react rapidly to changes in the environment. In addition, phytoplankton provides a good tool for lake classifications, since different species have different requirements and tolerance ranges for various environmental factors. The use of biological indicators is especially useful in arctic areas, were many of the chemical factors commonly fall under the detection limit and therefore do not provide much information about the environment. This work brings new information about species distribution and dynamics of arctic freshwater phytoplankton in relation to environmental factors. The phytoplankton of lakes in Finnish Lapland and other European high-altitude or high-latitude areas were compared. Most lakes were oligotrophic and dominated by flagellated species belonging to chrysophytes, cryptophytes and dinoflagellates. In Finnish Lapland cryptophytes were of less importance, whereas desmids had high species richness in many of the lakes. In Pan-European scale, geographical and catchment-related factors were explaining most of the differences in species distributions between different districts, whereas lake water chemistry (especially conductivity, SiO2 and pH) was most important regionally. Seasonal and interannual variation of phytoplankton was studied in subarctic Lake Saanajärvi. Characteristic phytoplankton species in this oligotrophic, dimictic lake belonged mainly to chrysophytes and diatoms. The maximum phytoplankton biomass in Lake Saanajärvi occurs during autumn, while spring biomass is very low. During years with heavy snow cover the lake suffers from pH drop caused by melt waters, but the effects of this acid pulse are restricted to surface layers and last for a relatively short period. In addition to some chemical parameters (mainly Ca and nutrients), length of the mixing cycle and physical factors such as lake water temperature and thermal stability of water column had major impact on phytoplankton dynamics. During a year with long and strong thermal stability, the phytoplankton community developed towards an equilibrium state, with heavy dominance of only a few taxa for a longer period of time. During a year with higher windiness and less thermal stability, the species composition was more diverse and species with different functional strategies were able to occur simultaneously. The results of this work indicate that although arctic lakes in general share many common features concerning their catchment and water chemistry, large differences in biological features can be found even in a relatively small area. Most likely the lakes with very different algal flora do not respond in a similar way to differences in the environmental factors, and more information about specific arctic lake types is needed. The results also show considerable year to year differences in phytoplankton species distribution and dynamics, and these changes are most likely linked to climatic factors.
  • Kauppila, Pirkko (Finnish Environment Institute, 2007)
    Monographs of the Boreal Environment Research 31
    The tackling of coastal eutrophication requires water protection measures based on status assessments of water quality. The main purpose of this thesis was to evaluate whether it is possible both scientifically and within the terms of the European Union Water Framework Directive (WFD) to assess the status of coastal marine waters reliably by using phytoplankton biomass (ww) and chlorophyll a (Chl) as indicators of eutrophication in Finnish coastal waters. Empirical approaches were used to study whether the criteria, established for determining an indicator, are fulfilled.The first criterion (i) was that an indicator should respond to anthropogenic stresses in a predictable manner and has low variability in its response. Summertime Chl could be predicted accurately by nutrient concentrations, but not from the external annual loads alone, because of the rapid affect of primary production and sedimentation close to the loading sources in summer. The most accurate predictions were achieved in the Archipelago Sea, where total phosphorus (TP) and total nitrogen (TN) alone accounted for 87% and 78% of the variation in Chl, respectively. In river estuaries, the TP mass-balance regression model predicted Chl most accurate when nutrients originated from point-sources, whereas land-use regression models were most accurately in cases when nutrients originated mainly from diffuse sources. The inclusion of morphometry (e.g. mean depth) into nutrient models improved accuracy of the predictions.The second criterion (ii) was associated with the WFD. It requires that an indicator should have type-specific reference conditions, which are defined as “conditions where the values of the biological quality elements are at high ecological status”. In establishing reference conditions, the empirical approach could only be used in the outer coastal waters types, where historical observations of Secchi depth of the early 1900s are available. Most accurate prediction was achieved in the Quark. However, the average reference values in the outer coastal types are underestimated in sites near the zone of the inner coastal waters. In the inner coastal water types, reference Chl, estimated from present monitoring data, are imprecise - not only because of the less accurate estimation method - but also because the intrinsic characteristics, described for instance by morphometry, vary considerably inside these extensive inner coastal types. As for phytoplankton biomass, the reference values were less accurate than in the case of Chl, because it was possible to estimate reference conditions for biomass only by using the reconstructed Chl values, not the historical Secchi observations. An paleoecological approach was also applied to estimate reference conditions for Chl. In Laajalahti, an urban embayment off Helsinki, strongly loaded by municipal waste waters until 1986, reference conditions prevailed in the mid- and late 1800s. The recovery of the bay from pollution has delayed as a consequence of benthic release of nutrients. Laajalahti will probably not achieve the good quality objectives of the WFD on time.The third criterion (iii) was associated with coastal management including the resources it has available. Analyses of Chl are cheap and fast to carry out compared to the analyses of phytoplankton biomass and species composition; the fact which has an effect on number of samples to be taken and thereby on the reliability of assessments. However, analyses on phytoplankton biomass and species composition provide more metrics for ecological classification, the metrics which reveal various aspects of eutrophication contrary to what Chl alone does.
  • Kauppila, Pirkko (Helsingin yliopisto, 2007)
    The tackling of coastal eutrophication requires water protection measures based on status assessments of water quality. The main purpose of this thesis was to evaluate whether it is possible both scientifically and within the terms of the European Union Water Framework Directive (WFD) to assess the status of coastal marine waters reliably by using phytoplankton biomass (ww) and chlorophyll a (Chl) as indicators of eutrophication in Finnish coastal waters. Empirical approaches were used to study whether the criteria, established for determining an indicator, are fulfilled. The first criterion (i) was that an indicator should respond to anthropogenic stresses in a predictable manner and has low variability in its response. Summertime Chl could be predicted accurately by nutrient concentrations, but not from the external annual loads alone, because of the rapid affect of primary production and sedimentation close to the loading sources in summer. The most accurate predictions were achieved in the Archipelago Sea, where total phosphorus (TP) and total nitrogen (TN) alone accounted for 87% and 78% of the variation in Chl, respectively. In river estuaries, the TP mass-balance regression model predicted Chl most accurately when nutrients originated from point-sources, whereas land-use regression models were most accurate in cases when nutrients originated mainly from diffuse sources. The inclusion of morphometry (e.g. mean depth) into nutrient models improved accuracy of the predictions. The second criterion (ii) was associated with the WFD. It requires that an indicator should have type-specific reference conditions, which are defined as "conditions where the values of the biological quality elements are at high ecological status". In establishing reference conditions, the empirical approach could only be used in the outer coastal water types, where historical observations of Secchi depth of the early 1900s are available. The most accurate prediction was achieved in the Quark. In the inner coastal water types, reference Chl, estimated from present monitoring data, are imprecise - not only because of the less accurate estimation method but also because the intrinsic characteristics, described for instance by morphometry, vary considerably inside these extensive inner coastal types. As for phytoplankton biomass, the reference values were less accurate than in the case of Chl, because it was possible to estimate reference conditions for biomass only by using the reconstructed Chl values, not the historical Secchi observations. An paleoecological approach was also applied to estimate annual average reference conditions for Chl. In Laajalahti, an urban embayment off Helsinki, strongly loaded by municipal waste waters in the 1960s and 1970s, reference conditions prevailed in the mid- and late 1800s. The recovery of the bay from pollution has been delayed as a consequence of benthic release of nutrients. Laajalahti will probably not achieve the good quality objectives of the WFD on time.    The third criterion (iii) was associated with coastal management including the resources it has available. Analyses of Chl are cheap and fast to carry out compared to the analyses of phytoplankton biomass and species composition; the fact which has an effect on number of samples to be taken and thereby on the reliability of assessments. However, analyses on phytoplankton biomass and species composition provide more metrics for ecological classification, the metrics which reveal various aspects of eutrophication contrary to what Chl alone does.
  • Lepistö, Liisa (National Board of waters and the Environment. Vesi- ja ympäristöhallitus, 1995)
    Publications of the Water and Environment Research Institute. 19
    Tiivistelmä: Kasviplanktonin kehitys vuosina 1968-1990 subarktisessa Lokan tekoaltaassa
  • Kangas, Pentti; Forsskåhl, Mikaela (Vesi- ja ympäristöhallitus, 1986)
    Vesientutkimuslaitoksen julkaisuja 68
  • Hällfors, Heidi (Helsingin yliopisto, 2013)
    Dinoflagellates are an important part of the Baltic Sea phytoplankton community. The group includes significant primary producers, consumers, bloom-forming species, toxic species, and species capable of rapid expansion to new areas. The aim of this thesis is to provide new information on the occurrence of dinoflagellates in the northern Baltic proper and the western Gulf of Finland by investigating 1) trends in temporal and spatial distribution of dinoflagellates, 2) patterns of co-occurring taxa in the dinoflagellate community, and 3) external factors that explain dinoflagellate occurrence. These issues were investigated in four studies, on which this thesis is based. In the first study, we compared the phytoplankton communities of the early 1900s and the present, and examined the role of dinoflagellates in the species compositions of these two periods. In the second study, the focal point was moved forward in time to the annual and interannual dynamics and diversity of the present-day dinoflagellate community, and in the third study further to a more detailed level, the description of a new taxon, Heterocapsa arctica subsp. frigida, and its ecology and distribution. Lastly, in the fourth study we shifted focus from seasonal, interannual and geographical occurrence to smaller-scale occurrence, i.e. the vertical distribution of dinoflagellates in the water column, as represented by a case study on Dinophysis acuminata and D. norvegica. A total of 47 dinoflagellate species, 28 genera, and four higher-level taxa were observed. Of the species-level taxa, 15 have not been previously reported from the northern Baltic proper and/or the Gulf of Finland. We also contributed to the knowledge of Baltic Sea dinoflagellate diversity by formally describing the new taxon, Heterocapsa arctica subsp. frigida, which furthermore represents a for phytoplankton unusual taxonomical level, i.e. a subspecies. The conspecificity of H. arctica subsp. frigida with H. arctica subsp. arctica, described from the Canadian Arctic, was demonstrated by their practically identical ITS rDNA sequences in combination with similarities in the morphological characteristics which are important in distinguishing between members of the genus Heterocapsa (i.e. body scale structure, shape and position of the nucleus, and position and ultrastructure of the pyrenoid). Despite the aforementioned similarities in genotype and fine structure, the two dinoflagellates can easily be distinguished by their general morphology; this together with their distinct geographical distributions warranted the description of the new subspecies. Investigating a selection of taxa comprising dinoflagellates, diatoms, cyanophytes, a chrysophyte and a chlorophyte, we documented clear differences in the historical (1903–1911) and modern (1993–2005) phytoplankton communities. The most obvious differences were the increased occurrence of dinoflagellates and the decrease in the diatom to dinoflagellate ratio in all seasons. Focusing on the present-day dinoflagellate community (1993–2000), we found a change in species composition even within the relatively short 8-year study period. None of the examined environmental descriptors could explain the observed centurial or decadal shifts. In light of the severe eutrophication of the Baltic Sea during the 20th century and the documented sensitivity of phytoplankton to different nutrient levels, we are inclined to interpret the centurial shift in phytoplankton communities as evidence of the direct and/or indirect influence of nutrient enrichment, though we lack data on the nutrient status a century ago. An attempt to find eutrophication indicator species failed, however, since none of the 10 candidate taxa fulfilled the criteria of good indicator species. On an annual scale, temperature in combination with season is the best predictor of dinoflagellate species composition. The dinoflagellates formed five groups according to their seasonality: vernal, early summer, summer and autumn, throughout the growing season occurring, and generalist taxa; sporadically occurring dinoflagellates constituted a sixth group. The seasonal groups reflect the annual succession from dinoflagellates occurring in a high-biomass spring bloom community that thrives in cold, nutrient-rich waters, to dinoflagellates occurring later in the year in warm, nutrient-poor waters with a lower phytoplankton biomass. Overall, annual succession is of much greater importance than interannual variability in explaining variation in the dinoflagellate species composition in the northern Baltic Sea. Their regular presence and tendency to form subsurface maxima qualified Dinophysis acuminata and D. norvegica as suitable case study objects to investigate the vertical distribution patterns of dinoflagellates. Both species formed population maxima either in the nutrient-poor mixed surface layer above 10 m depth, or alternatively, below 10 m depth, in or out of the euphotic zone but near the thermocline and coinciding with a nutricline. When D. acuminata and D. norvegica co-occurred, their abundances peaked at different depths, even when both species formed maxima in the surface layer. This emphasizes the importance of accurate species determinations and the riskiness of drawing conclusions on the ecology of one species based on findings regarding a close relative. Based on our results, the primary mode of nutrition for D. acuminata in the northern Baltic Sea seems to be photoautotrophy, and also D. norvegica may utilize photoautotrophy to a greater extent than lately suggested.