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Analys av kiselalgsmetoden - hur lång bör sedimenteringstiden vara

Berthold, Sara LU (2015) MVEK02 20151
Studies in Environmental Science
Abstract (Swedish)
Kiselalger, vattenlevande, mikroskopiska organismer med kiselskal, används som bioindikatorer för vattenkvalitet eftersom de är artrika och påverkas av sin omgivning. Processen kallas Kiselalgsmetoden och utförs genom en standard, en standard jag valde att analysera.
Proven tas från stenar i vattendrag och sedan görs ett preparat som är fixerat på objektglas som kan undersökas i mikroskop genom att räkna, mäta och bestämma arterna på dem. Ett moment i metoden går ut på att de insamlade proverna som består av en blandning av vatten och sediment skall stå och sedimentera så att överblivande vatten kan hällas av. Eftersom, normalt sett, det är det koncentrerade kiselalgsprovet som undersöks, är tiden för sedimentering avgörande. Får inte... (More)
Kiselalger, vattenlevande, mikroskopiska organismer med kiselskal, används som bioindikatorer för vattenkvalitet eftersom de är artrika och påverkas av sin omgivning. Processen kallas Kiselalgsmetoden och utförs genom en standard, en standard jag valde att analysera.
Proven tas från stenar i vattendrag och sedan görs ett preparat som är fixerat på objektglas som kan undersökas i mikroskop genom att räkna, mäta och bestämma arterna på dem. Ett moment i metoden går ut på att de insamlade proverna som består av en blandning av vatten och sediment skall stå och sedimentera så att överblivande vatten kan hällas av. Eftersom, normalt sett, det är det koncentrerade kiselalgsprovet som undersöks, är tiden för sedimentering avgörande. Får inte proverna sätta sig tillräckligt länge kan mindre alger i det vatten som sedan hälls av att gå förlorade. Konsekvensen av detta är att vattnets status kan felbedömas eftersom statusen grundas på vilka arter som kan identifieras i proverna. Jag valde att göra mina tester på det dekanterade vattnet och testade tre olika sedimenteringstider: 30-, 60- och 90 minuter. Eftersom jag ansåg det intressant att se vilka alger som i så fall hade hällts av. Jag delade upp resultaten i fyra olika kategorier: Alla alger i alla storlekar, bara små (<20µm), mellanstora (20-40µm) och stora (>40µm) alger. Jag noterade även medellängderna i en ytterligare räkning och några vanligt förekommande arter. Frågeställningarna var 1) Hur länge bör provet sedimentera? och 2) Sjunker de stora algerna fortare än de små?
I några av fallen visade det sig vara en signifikant skillnad mellan proven beroende av sedimenteringstid. Från p-värdena fann jag att för alla alger av alla storlekar och för de små upphörde avtagandet av alger efter 60 minuter. För de medelstora avtog sedimenteringen efter 90 minuter. Det fanns inga signifikanta resultat för de stora algerna, inte heller för medellängderna i den fjärde räkningen. En av vattendragen innehöll bara större alger och sedimentationshastigheten var där högre än i de andra. Tre vanligt förekommande alger i de räknade proverna var Mayamaea atomus var. permitis, Eolimna minima och Fistulifera saprophila. Jag kom på några metoder till framtida studier som kanske kan förbättra validiteten hos resultaten.
Arbetet utfördes i Uppsala på Sveriges Lantbruksuniversitet på Institutionen för vatten och miljö samt på Lunds Universitet 3 november 2014 - 20 maj 2015. (Less)
Abstract
Diatoms, water living, microscopic organisms with silicon shells, are used as bioindicators of water quality because they are diverse and influenced by their surroundings. The process is called The Diatom Method and is accomplished through a standard, a standard I have chosen to analyze.
The samples are taken from stones in water streams and then a preparation is made to fix the algae on slides that can be studied in a microscope by counting, measuring and identifying the species. A section in this method is a process where the collected samples, consisting of a mixture between water and sediment, are allowed to settle so that the prospective water can be decanted. Since, normally, it is the concentrated sediment that is investigated,... (More)
Diatoms, water living, microscopic organisms with silicon shells, are used as bioindicators of water quality because they are diverse and influenced by their surroundings. The process is called The Diatom Method and is accomplished through a standard, a standard I have chosen to analyze.
The samples are taken from stones in water streams and then a preparation is made to fix the algae on slides that can be studied in a microscope by counting, measuring and identifying the species. A section in this method is a process where the collected samples, consisting of a mixture between water and sediment, are allowed to settle so that the prospective water can be decanted. Since, normally, it is the concentrated sediment that is investigated, the time of sedimentation is crucial. If the sample does not settle long enough, too many algae will follow the decanted water, thus leading to a loss of diatoms in the investigated samples. The consequence of this is that the water status can be misjudged since the status of the water is based on the species identified. I chose to do my tests on the decanted water and tested three different times for sedimentation; 30, 60 and 90 minutes since I found it interesting to see which algae that would have been decanted. I divided the results into four categories; all algae in all sizes and only small (<20µm), medium (20-40µm) and large (> 40µm) algae. I also noted medium length and the most regularly occurring species. The questions were: 1) How long should the sample settle? And 2) Do the large algae settle faster than the small ones?
In some cases there proved to be a significant difference between samples depending on sedimentation time. From the p-values I derived that for all algae in all sizes and small algae the settling ceased after 60 minutes. For the medium sized algae the settling ceased after 90 minutes. There were no significant results regarding large algae, neither for the average sizes and sedimentation time in the fourth counting in which the algae where measured by medium length. One of the water streams consisted mainly of large algae and the sedimentation rate was higher there than for the algae in the other streams. Three common algae in the samples were Mayamaea atomus was. permitis, Eolimna minima and Fistulifera saprophila. I also came up with some methods for future analysing that could improve the validity of the results.
The work was done in Uppsala in Sweden's University of Agricultural Sciences at the Department of Water and Environment, and the University of Lund November 3, 2014 - May 20, 2015. (Less)
Please use this url to cite or link to this publication:
author
Berthold, Sara LU
supervisor
organization
course
MVEK02 20151
year
type
M2 - Bachelor Degree
subject
keywords
diatoms, kiselalger, kiselalgsmetoden, påväxtalger, sedimentering
language
Swedish
id
5469152
date added to LUP
2015-06-10 15:23:47
date last changed
2015-06-10 15:23:47
@misc{5469152,
  abstract     = {Diatoms, water living, microscopic organisms with silicon shells, are used as bioindicators of water quality because they are diverse and influenced by their surroundings. The process is called The Diatom Method and is accomplished through a standard, a standard I have chosen to analyze. 
The samples are taken from stones in water streams and then a preparation is made to fix the algae on slides that can be studied in a microscope by counting, measuring and identifying the species. A section in this method is a process where the collected samples, consisting of a mixture between water and sediment, are allowed to settle so that the prospective water can be decanted. Since, normally, it is the concentrated sediment that is investigated, the time of sedimentation is crucial. If the sample does not settle long enough, too many algae will follow the decanted water, thus leading to a loss of diatoms in the investigated samples. The consequence of this is that the water status can be misjudged since the status of the water is based on the species identified. I chose to do my tests on the decanted water and tested three different times for sedimentation; 30, 60 and 90 minutes since I found it interesting to see which algae that would have been decanted. I divided the results into four categories; all algae in all sizes and only small (<20µm), medium (20-40µm) and large (> 40µm) algae. I also noted medium length and the most regularly occurring species. The questions were: 1) How long should the sample settle? And 2) Do the large algae settle faster than the small ones? 
In some cases there proved to be a significant difference between samples depending on sedimentation time. From the p-values I derived that for all algae in all sizes and small algae the settling ceased after 60 minutes. For the medium sized algae the settling ceased after 90 minutes. There were no significant results regarding large algae, neither for the average sizes and sedimentation time in the fourth counting in which the algae where measured by medium length. One of the water streams consisted mainly of large algae and the sedimentation rate was higher there than for the algae in the other streams. Three common algae in the samples were Mayamaea atomus was. permitis, Eolimna minima and Fistulifera saprophila. I also came up with some methods for future analysing that could improve the validity of the results.
The work was done in Uppsala in Sweden's University of Agricultural Sciences at the Department of Water and Environment, and the University of Lund November 3, 2014 - May 20, 2015.},
  author       = {Berthold, Sara},
  keyword      = {diatoms,kiselalger,kiselalgsmetoden,påväxtalger,sedimentering},
  language     = {swe},
  note         = {Student Paper},
  title        = {Analys av kiselalgsmetoden - hur lång bör sedimenteringstiden vara},
  year         = {2015},
}