Umeå University's logo

Här presenteras resultaten från forskningsprojektet ”Eutrofiering och närsalter iBottniska viken - Ett ekosystem i förändring”. Projektet är ett av fyra syntesprojektsom genomförts inom forskningssatsningen Avloppsvatten och övergödning.

Med de fyra syntesarbeten ville Naturvårdsverket och Havs- och vattenmyndighetenfå sammanfattad och analyserad kunskapsläge och kunskapsbehovinom områdena avloppsvatten och övergödning. Det övergripande syftet medsynteserna var att bidra till policyutveckling inom hållbar vattenhantering så attvi uppnår miljömålen på lång sikt och att miljöns tillstånd förbättras. Utlysningenvar inriktad på tre områden varav ett var om övergödning i kust och hav i Bottniskaviken.

Projektet har finansierats med medel från Naturvårdsverkets miljöforskningsanslag.

Rapporten har skrivits av Agneta Andersson, Siv Huseby, Joakim Ahlgren,Karolina Eriksson och Sonia Brugel från Umeå universitet.

Rapporten har granskats för vetenskaplig kvalitet av Jens Fölster (SLU) samtför praktisk relevans av Lars Åkesson (Havs- och vattenmyndigheten), Anneli Sedin(Länsstyrelsen i Västerbotten) samt Kerstin Rosén Nilsson (Naturvårdsverket).

Författarna svarar för rapportens innehåll.

Phytoplankton are used worldwide to monitor environmental status in aquatic systems. Long-time series of microscopy-analyzed phytoplankton are available from many monitoring stations. The microscopy-method is however time consuming and has short-comings. DNA metabarcoding has been suggested as an alternative method, but the consistency between different methods need further investigation. We performed a comparative study of microscopy and metabarcoding analyzing micro- and nanophytoplankton. For metabarcoding, 25-1000 ml seawater were filtered, DNA extracted and the 18S and 16S rRNA gene amplicons sequenced. For microscopy, based on the Utermöhl method we evaluated the use of three metrics: abundance, biovolume and carbon biomass. At the genus, species, and unidentified taxa level, metabarcoding generally showed higher taxonomic diversity than microscopy, and diversity was already captured at the lowest filtration volume tested, 25 ml. Metabarcoding and microscopy displayed relatively similar distribution pattern at the group level. The results showed that the relative abundances of the 18S rRNA amplicon at the group level best fitted the microscopy carbon biomass metric. The results are promising for implementing DNA metabarcoding as a complement to microscopy in phytoplankton monitoring, especially if databases would be improved and group level indexes could be applied to classify the environmental state of water bodies.

Bacterioplankton growth rate is an indicator of the decomposition of organic matter and thereby trophic status of the Sea. The bacterioplankton metabolism accounts for about half of the mineralization of organic matter and thereby pelagic oxygen consumption.

The bacterioplankton growth rate in deep waters indicates good trophic status in the off-shore Bothnian Bay and Bothnian Sea. Deep water growth rates were 67 % higher than at corresponding depths in the Atlantic Ocean, lacking excess enrichment. The decline that has earlier been reported has now ceased. During the last few years the growth rates has increased some and there is now no significant trends in any of the studied basins.

Fyra utsjöstationer, som ingår i den nationella miljöövervakningen i Bottniskaviken, har i denna undersökning naturtypsbestämts enligt art- och habitatdirektivets naturtyper och EUNIS/HUB. Stationerna provtogs med Van Veen huggare och den taxonomiska analysen utfördes på lab. För utsjö finns tre möjliga Natura 2000-naturtyper: 1110 sandbankar, 1170 rev och 1180 bubbelstrukturer. Ingen av de fyra stationerna passade beskrivningen av några av dessa tre möjligheter och klassades därmed inte som naturtyp enligt habitatdirektivet. Alla stationer hade lerigt sediment (>90%) med inslag av lite sand, silt eller noduler. Vid alla stationer dominerade amphipod-arterna Monoporeia affinis och/eller Pontoporeia femorata och stationerna bedömdes som ABH3N1 baltisk afotisk lerigt sediment dominerad av Monoporeia affinis och/ eller Pontoporeia femorata.

Four offshore monitoring stations in the Gulf of Bothnia were in this study classified according to the Habitat Directive and EUNIS/ HUB. The stations were sampled with Van Veen grab and later taxonomically analyzed in the laboratory. For offshore stations there are three possible Natura2000 types: 1110 sandbanks, 1170 reefs and 1180 submarine structures made by leaking gases. None of the stations could fit the descriptions of any of these Natura2000 habitat types. The sediment at all four stations was mostly clay (>90%) with elements of sand and silt and ferromanganese concretions. At all stations the amphipod species Monoporeia affinis and/or Pontoporeia femorata dominated the biomass. The EUNIS/HELCOM HUB classification for all stations was ABH3N1 Baltic aphotic muddy sediment dominated by Monoporeia affinis and/or Pontoporeia femorata.

Despite cyanobacteria being a key phytoplankton group in the Baltic Sea, the factors governing their community structure are still poorly understood. Here, we studied the occurrence of the orders Chroococcales, Oscillatoriales and Nostocales, and potentially explanatory variables at five locations in the northern Baltic Sea from June–September, 1998–2012. Cyanobacteria constituted 1–36% of the total phytoplankton biomass along the north–south gradient. In the Bothnian Bay, Chroococcales and Oscillatoriales dominated the cyanobacterial community, whereas in the Bothnian Sea and northern Baltic Proper, Nostocales was the dominant group. The dominance of Chroococcales was coupled to low salinity and low total phosphorus, whereas Oscillatoriales correlated with high total nitrogen and low salinity. Nostocales correlated to high total phosphorus, inorganic phosphorus and salinity. Chroococcales showed an increase over time in the offshore Bothnian Bay, whereas Nostocales increased in the coastal Bothnian Sea and coastal Baltic Proper. The increase of Nostocales in the coastal Bothnian Sea was explained by a rise in total phosphorus and decrease in dissolved inorganic nitrogen compared to an increase of total nitrogen and phosphorus in the coastal Baltic Proper. No significant trends were observed in the cyanobacterial community in the offshore Bothnian Sea and the offshore northern Baltic Proper. We concluded that Chroococcales may be a useful indicator for increased phosphorus levels in waters with low phosphorus concentrations, whereas Nostocales could be used as a quality indicator for increasing phosphorus concentrations in waters with low inorganic N/P ratios (<20), such as in the coastal Bothnian Sea and Baltic Proper.

During normal sample preparation, storage in freezers and subsequent freeze/thaw cycles are commonly introduced. The effect of freeze/thaw cycles on the metabolic profiling of microalgal extracts using HR-MS was investigated. Methanolic extracts of monocultures of Arctic marine diatoms were analyzed immediately after extraction, after seven days of storage at -78 degrees C (one freeze/thaw cycle), and after additional seven days at -20 degrees C (two freeze/thaw cycles). Repeated direct infusion high-resolution mass spectrometry analysis of microalgae extracts of the same sample showed that reproducibility was ca. 90% when a fresh (unfrozen) sample was analyzed. The overall reproducibility decreased further by ca. 10% after the first freeze/thaw-cycle, and after one more freeze/thaw cycle the reproducibility decreased further by ca. 7%. The decrease in reproducibility after freeze-thaw cycles could be attributed to sample degradation and not to instrument variability.

In this study, we investigate how metabolic fingerprints are related to temperature. Six common northern temperate diatoms (Attheya longicornis, Chaetoceros socialis, Chaetoceros furcellatus, Porosira glacialis, Skeletonema marinoi, and Thalassiosira gravida) were cultivated at two different temperatures, 0.5 and 8.5 °C. To exclude metabolic variations due to differences in growth rates, the growth rates were kept similar by performing the experiments under light limited conditions but in exponential growth phase. Growth rates and maximum quantum yield of photosynthesis were measured and interpreted as physiological variables, and metabolic fingerprints were acquired by high-resolution mass spectrometry. The chemical diversity varied substantially between the two temperatures for the tested species, ranging from 31% similarity for C. furcellatus and P. glacialis to 81% similarity for A. longicornis. The chemical diversity was generally highest at the lowest temperature.

I flera områden i norra Östersjön har cyanobakterierna ökat under de senaste tio till femton åren. I Bottenhavets och Egentliga Östersjöns kustområden ökar de kvävefixerande cyanobakterierna. I Bottenvikens utsjö är det den småcelliga och kolonibildande gruppen Chroococcales som blir fler. Förändringarna beror i flera fall på ökande halter av fosfor.