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Microphytobenthic species composition, pigment concentration, and primary production in sublittoral sediments of the Trondheimsfjord (Norway) 1
Author(s) -
Cibic Tamara,
Blasutto Oriana,
Hancke Kasper,
Johnsen Geir
Publication year - 2007
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2007.00405.x
Subject(s) - fucoxanthin , biology , botany , diatom , photosynthesis , chlorophyll a , dry weight , carotenoid , benthic zone , algae , ecology
In spring 2005, monthly sampling was carried out at a sublittoral site near Tautra Island. Microphytobenthic identification, abundance (ABU), and biomass (BIOM), were performed by microscopic analyses. Bacillariophyceae accounted for 67% of the total ABU, and phytoflagellates constituted 30%. The diatom floristic list consisted of 38 genera and 94 species. Intact light‐harvesting pigments chl a , chl c , and fucoxanthin and their derivatives were identified and quantified by HPLC. Photoprotective carotenoids were also observed (only as diadinoxanthin; no diatoxanthin was detected). Average fucoxanthin content was 4.57 ± 0.45 μg fucoxanthin · g sediment dry mass −1 , while the mean chl a concentration was 2.48 ± 0.15 μg · g −1 dry mass. Both the high fucoxanthin:chl a ratio (considering nondegraded forms) and low amounts of photoprotective carotenoids indicated that the benthic microalgal community was adapted to low light. Microphytobenthic primary production was estimated in situ (MPPs, from 0.15 to 1.28 mg C · m −2 · h −1 ) and in the laboratory (MPPp, from 6.79 to 34.70 mg C · m −2 · h −1 under light saturation) as 14 C assimilation; in April it was additionally estimated from O 2 ‐microelectrode studies (MPP O2 ) along with the community respiration. MPP O2 and the community respiration equaled 22.9 ± 7.0 and 7.4 ± 1.8 mg C · m −2 · h −1 , respectively. A doubling of BIOM from April to June in parallel with a decreasing photosynthetic activity per unit chl a led us to suggest that the microphytobenthic community was sustained by heterotrophic metabolism during this period.