| dc.description.abstract | På bakgrunn av tidligere oppblomstringer av cyanobakterien Anabaena lemmermannii i Norsjø, er målsetningen å undersøke vannkvalitet, eventuelle forekomster av cyanobakterier og hvorvidt de er toksinproduserende. Norsjø ligger i Telemark fylke, fra Skien i sør, Nome i vest og til Sauherad i nord. Navnet kommer fra gammelt av fra no”r, som betyr trang eller smal. På langs er Norsjø ca. 29 km, den største bredden er 3 km ved Ulefoss. Arealet til Norsjø utgjør 58,4 km2, mens dypeste punkt er 170 m. Volumet av innsjøen er 5,1 km3. Norsjø brukes som drikkevannskilde for beboere i kommunene Skien og Nome. Feltarbeidet tar for seg prøvetaking av fysiske/ kjemiske vannparametre og planteplankton ved 6 stasjoner fra det nordlige området av Norsjø. Prøvetakingsperioden var fra 3.7.08 til og med 22.8.08. Tilstanden på vannkvalitet er bedømt etter SFTs inndeling av tilstandsklasser for næringssalter, organiske og forsurende stoffer. Med hensyn på næringssalter og organiske stoffer klassifiseres Norsjø som klasse II ”god”. For forsurende stoffer viste imidlertid tilstanden ”mindre god”. Sesongmiddelverdiene for klorofyll a på 4,8 μg/L, tyder på at Norsjø har endret seg fra oligotrof til en mer mesotrof tilstand. Et N/P forhold på 55, indikerer at fosfor er en begrensende vekstfaktor for planteplankton. Ved en analyse ble det påvist at Anabaena lemmermannii forekom i overflatevannet ved samtlige prøvestasjoner. I felt ble oppblomstring imidlertid kun observert ved Torsnes. Toksinet microcystin ble påvist (4.8) ved Torsnes, Ulefoss, Romnes og Årnes, det ble også påvist ved Patmos og Torsnes 14.8. ELISA- analysen viste konsentrasjoner mellom 0,18-0,25 μg microcystin/L. Ved PCR ble gen for microcystinproduksjon påvist ved Patmos og Ulefoss. I forkant av de største klorofyllkonsentrasjonene ble det målt høyere temperatur i overflatetevannet, og kommet store nedbørsmengder. Oppblomstringer skjer ved økende temperatur og ved tilstrekklig tilgang på næringsstoffer. En medvirkende årsak kan være at vestsiden ligger skjermet til i, forhold til vind fra sør. Dermed er det lite sirkulasjon i vannmassene. Ved Patmos er det langgrunt, vannet varmes opp, og næringspartikler virvles lett opp. I tillegg kan Anabaena lemmermannii ha blitt ført med vannmassene fra sør.||Lake Norsjø is located in the southwest of Telemark county and extends southward to Skien, westward to Nome, and northward to Sauherad. It is approximately 29 km long and is 3 km at its widest point by Ulefoss. The total water area constitutes 58.4 km2, with the deepest point being 170 m, resulting in a total volume of 5.1 km3 Water quality is judged by measuring quantities of nutrients, organic matter and acidifying substances, which then correspond to a class determined by the Norwegian Pollution Control Authority (SFT). Lake Norsjø was classified as follows: for nutrients and organic matter, Class II "good"; for the values of alkalinity and pH as acidifying substances, Class III “less good”. The seasonal measurement of chorophyll a at 4,8 μg / L suggests that Lake Norsjø has changed from an oligotrophic for more mesotrophic lake. The N:P ratio of 55 indicates that phosphorus is the limiting nutrient for phytoplankton in Lake Norsjø. . The lake is used as a source of drinking water for residents in the municipalities of Skien and Nome. Because of earlier finds of the cyanobacteria Anabaena lemmermannii in Lake Norsjø, it is desirable to monitorer water quality as well as any instances of cyanobacteria to determine exactly which bacteria and/or toxins are produced in order to assess health risks related to exposure. The field data collected here deals with samples and results from six stations along the northern area of Lake Norsjø. The sampling period was from 3 July 2008 up to and including 22 August 2008. Halfway through the quantitative analysis of the phytoplankton, it was discovered that Anabaena lemmermannii occurred in surface water at all sample stations. Water bloom only was observed by Torsnes. Hepatoxic microcystin was proven (4.8) by Torsnes, Ulefoss, Romnes and Årnes, it was also proven 14.8 by Patmos and Torsnes, using ELISA. The analysis showed concentrations between 0,18-0,25 μg / L. Using PCR, microcystingen was also detected at Patmos and Ulefoss. Prior to the major chlorophyll a concentrations in July, when relatively high temperatures in the water stabilized, there was a large amount of rainfall. Growth occurs with increasing temperature and sufficient supplies of nutrients, but another contributing factor may be that the west side of Lake Norsjø is shielded from winds from the south. This results in calm wind conditions and low circulation of water. On the side of Patmos, the water is shallow, which results in warm water in which food particles are easily stirred up. In addition, Anabaena lemmermannii was carried up with water from the south. | |
| dc.description.abstract | Lake Norsjø is located in the southwest of Telemark county and extends southward to Skien, westward to Nome, and northward to Sauherad. It is approximately 29 km long and is 3 km at its widest point by Ulefoss. The total water area constitutes 58.4 km2, with the deepest point being 170 m, resulting in a total volume of 5.1 km3 Water quality is judged by measuring quantities of nutrients, organic matter and acidifying substances, which then correspond to a class determined by the Norwegian Pollution Control Authority (SFT). Lake Norsjø was classified as follows: for nutrients and organic matter, Class II "good"; for the values of alkalinity and pH as acidifying substances, Class III ??ess good?? The seasonal measurement of chorophyll a at 4,8 μg / L suggests that Lake Norsjø has changed from an oligotrophic for more mesotrophic lake. The N:P ratio of 55 indicates that phosphorus is the limiting nutrient for phytoplankton in Lake Norsjø. . The lake is used as a source of drinking water for residents in the municipalities of Skien and Nome. Because of earlier finds of the cyanobacteria Anabaena lemmermannii in Lake Norsjø, it is desirable to monitorer water quality as well as any instances of cyanobacteria to determine exactly which bacteria and/or toxins are produced in order to assess health risks related to exposure. The field data collected here deals with samples and results from six stations along the northern area of Lake Norsjø. The sampling period was from 3 July 2008 up to and including 22 August 2008. Halfway through the quantitative analysis of the phytoplankton, it was discovered that Anabaena lemmermannii occurred in surface water at all sample stations. Water bloom only was observed by Torsnes. Hepatoxic microcystin was proven (4.8) by Torsnes, Ulefoss, Romnes and ?rnes, it was also proven 14.8 by Patmos and Torsnes, using ELISA. The analysis showed concentrations between 0,18-0,25 μg / L. Using PCR, microcystingen was also detected at Patmos and Ulefoss. Prior to the major chlorophyll a concentrations in July, when relatively high temperatures in the water stabilized, there was a large amount of rainfall. Growth occurs with increasing temperature and sufficient supplies of nutrients, but another contributing factor may be that the west side of Lake Norsjø is shielded from winds from the south. This results in calm wind conditions and low circulation of water. On the side of Patmos, the water is shallow, which results in warm water in which food particles are easily stirred up. In addition, Anabaena lemmermannii was carried up with water from the south. | |
