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- Title
Nitrogen-fixing cyanobacteria (free-living and diatom endosymbionts): their use in southern California stream bioassessment.
- Authors
Stancheva, Rosalina; Sheath, Robert; Read, Betsy; McArthur, Kimberly; Schroepfer, Chrystal; Kociolek, J.; Fetscher, A.
- Abstract
A weight-of-evidence approach was used to examine how nutrient availability influences stream benthic algal community structure and to validate nutrient-response thresholds in assessing nutrient limitation. Data from 104 southern California streams spanning broad nutrient gradients revealed that relative abundance of N-fixing heterocystous cyanobacteria ( Nostoc, Calothrix), and diatoms ( Epithemia, Rhopalodia)-containing cyanobacterial endosymbionts, decreased with increasing ambient inorganic N concentrations within the low end of the N gradient. Response thresholds for these N fixers were 0.075 mg l NO-N, 0.04 mg l NH-N, and an N:P ratio (by weight) of 15:1. The NO-N threshold was independently validated by observing nitrogenase gene expression using real-time reverse transcriptase PCR. Morphometric analysis of cyanobacterial endosymbionts in Epithemia and Rhopalodia indicated that endosymbiont biovolume per diatom cell decreased with increasing NO-N. Our findings indicate that abundance of heterocyst-containing cyanobacteria and endosymbiont-containing diatom cells are good indicators for rapid nutrient biomonitoring. Because heterocystous cyanobacteria and Epithemia/Rhopalodia were not always recorded together at N-limited sites, examining both assemblages jointly may provide a more comprehensive assessment of stream nutrient limitation than using either assemblage alone.
- Subjects
SOUTHERN California; NITROGEN-fixing cyanobacteria; DIATOMS; ENDOSYMBIOSIS; WATER quality biological assessment; REVERSE transcriptase polymerase chain reaction
- Publication
Hydrobiologia, 2013, Vol 720, Issue 1, p111
- ISSN
0018-8158
- Publication type
Article
- DOI
10.1007/s10750-013-1630-6