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Potentially toxic diatom genus Pseudo-nitzschia in the northern Adriatic Sea: ecological, taxonomic and molecular features

Marić Pfannkuchen, Daniela (2013) Potentially toxic diatom genus Pseudo-nitzschia in the northern Adriatic Sea: ecological, taxonomic and molecular features. Doctoral thesis, Sveučilište u Zagrebu, Prirodoslovno matematički fakultet.

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Phytoplankton samples were collected at two stations, RV001 and SJ107, in the northern Adriatic Sea from 1972 to 2009. The analysis of this 37 years long data set provided significant insights in the phytoplankton dynamics, species succession and changes in the phytoplankton community. It was found that the total abundance of phytoplankton, diatoms and nanophytoplankton significantly decreased after the year 2000, and a change in the species composition and blooming periods has been observed. Species from the genus Pseudo-nitzschia were among the most abundant and most frequent diatoms during the entire investigated period. Changes in the species composition within the genus have been observed. In the 1980ies the phytoplankton community was dominated by the P. seriata group. While the group P. delicatissima first appeared in the '80s and since then their frequency continuously increased. P. delicatissima has a frequency of appearance from 76-97% in the period from 1993-2010. Morphological, ecological and toxic properties of the genus Pseudo-nitzschia were studied in the recent years in the northern Adriatic. Monoclonal cultures were established for taxonomical and molecular identification. The existence of 7 different Pseudo-nitzschia species is confirmed in the northern Adriatic on the basis of detailed morphological characteristics. Three in the P. seriata group: P. fraudulenta, P. pungens and P. subfraudulenta, and four species in P. delicatissima group: P. mannii, P. pseudodelicatissima, P. delicatissima and P. calliantha. The genus Pseudo-nitzschia is associated with the production of domoic acid (DA), a strong neurotoxin. Special attention was given to a potentially toxic P. calliantha that dominated the bloom in 2007. Most of the identified species were confirmed by molecular methods with different genetic markers (18S, ITS1-5,8S-ITS2, 28S). Similarity representation after Neighbourjoining analysis, most parsimoneous phylogenetic reconstruction and analysis of populations confirmed that populations from the Northern Adriatic are separated and genetically different from the rest of the Mediterranean and the world (ITS1-5.8S-ITS2). It could be demonstrated that the investigated Pseudo-nitzschia populations of the northern Adriatic are indigenous and genetically separated from populations in the Mediterranean and other regions of the world.

Item Type: Thesis (Doctoral thesis)
Uncontrolled Keywords: phytoplankton; Pseudo nitzschia; ecology; taxonomy; philogeny; 18S; ITS1 5; 8S ITS2; 28S
Subjects: NATURAL SCIENCES > Geology
Divisions: Center for Marine Research
Project titleProject leaderProject codeProject type
Mehanizam dugoročnih promjena u ekosustavu sjevernog Jadrana[38614] Robert Precali098-0982705-2731MZOS
Depositing User: Daniela Marić Pfannkuchen
Date Deposited: 11 Sep 2014 08:09

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