Authors
Patricia M Glibert, Cynthia A Heil, Emily R Hall, Cong Fei, Shady A Amin
Published in
Harmful algae. Volume 159. Pages 103208. Epub Aug 22, 2026.
Abstract
Blooms of Karenia brevis occur almost annually in the eastern Gulf of Mexico (Gulf of America). Submarine ground water discharges (SGD) have been previously suggested as a potential nutrient source in sustaining blooms. The West Florida Shelf is dotted with blue holes, or underwater sinkholes, which may be a route by which SGD seeps into offshore waters. Previously reported measurements within the holes demonstrated potentially high rates of denitrification, and dissimilatory nitrate reduction to ammonia (DNRA). Here, multiple water column stations were monitored monthly for four years near to-and away from-these sinkholes to assess the nitrogen (N) isotopic signatures of the particulate material. One offshore site, but not others, had mean δ15N values of 13.28 in surface samples and 12.58 in bottom samples, with the highest value reaching 38.86, reflecting highly processed N. Other sites had much lower δ15N values. Higher δ15N values were associated with lower river flows, as N would have a longer time to undergo processing. The microbiome of the free-living (>0.22 μm) planktonic communities of this site, examined via 16S rRNA amplicon sequencing, confirmed the presence of putative denitrifying bacteria. Following Hurricane Ian, a K. brevis bloom formed with low δ15N (<5), but as the bloom was sustained, the δ15N of the particulate material increased significantly, reflecting greater reliance on recycled N. Historical reports of Karenia within 10 km of known blue holes show that K. brevis can concentrate in these locations, which may be hot spots for a diversity of Karenia species.
PMID:
42702416
Bibliographic data and abstract were imported from PubMed on 07 Sep 2026.
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