A. Hansen

Publications11
h-index8
Citations1,617
Highly Influential Citations126
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High rates of N2 fixation by unicellular diazotrophs in the oligotrophic Pacific Ocean
TLDR
Direct measurements of 15N2 fixation by small diazotrophs in various parts of the Pacific Ocean, including the waters off Hawaii where the unicellular diazOTrophs were first characterized, show that N1 fixation by unicells can support a significant fraction of total new production in oligotrophic waters.
Unicellular cyanobacteria fix N2 in the subtropical North Pacific Ocean
TLDR
It is shown that there are unicellular cyanobacteria in the open ocean that are expressing nitrogenase, and are abundant enough to potentially have a significant role in N dynamics.
Experiments linking nitrogenase gene expression to nitrogen fixation in the North Pacific subtropical gyre
TLDR
Monitoring of diazotroph activity in controlled experiments containing natural populations of nitrogen (N2)-fixing microbes collected offshore from Kane'ohe Bay, Hawai'i, and from Station ALOHA in the North Pacific subtropical gyre showed that the abundances of the major phylotypes did not change substantially during experimental incubations.
Assessment of Recent Habitat Conditions of Eastern Oyster Crassostrea virginica Bars in Mesohaline Chesapeake Bay
TLDR
Between 1999 and 2001, an acoustic seabed classification system and underwater videography were used to assess oyster habitat conditions throughout Maryland's portion of Chesapeake Bay relative to eastern oyster recruitment and habitat restoration activities.
Introduction Pathways, Differential Survival of Adult and Larval Zebra Mussels (Dreissena polymorpha), and Possible Management Strategies, in an Adirondack Lake, Lake George, NY
TLDR
Bioassays confirmed model predictions that zebra mussel recruitment is limited by the moderate water alkalinity in Lake George, but that adults were able to survive and grow, and indicated that Lake George water limited the survival of zebraMussel larvae but not of adults.
Bigger is better: size-selective mortality throughout the life history of a fast-growing clupeid, Spratelloides gracilis
TLDR
A cohort of the fast-growing sprat Spratelloides gracilis was sampled during late-larval, juvenile and adult life-history phases using light traps on the North West Shelf of Western Australia finding that individuals that survived the larval stage to become juveniles underwent strong selective mortality.
Specific amplification of the 18S rRNA gene as a method to detect zebra mussel (Dreissena polymorpha) larvae in plankton samples
TLDR
A Dreissena polymorpha-specific 18S ribosomal RNA gene targeted oligonucleotide primer (ZEB-715a) and Polymerase Chain Reaction (PCR) assay was developed and compared with cross-polarized microscopy as a means to detect zebra mussel veligers in plankton samples and results were generally consistent between the two methods.
Unicellular cyanobacteria ® x N 2 in the subtropical North Paci ® c Ocean
NATURE | VOL 412 | 9 AUGUST 2001 | www.nature.com 635 8. McKenzie, D. Finite deformation during ̄uid ̄ow. Geophys. J. R. Astron. Soc. 58, 689±715 (1979). 9. Ribe, N. M. Seismic anisotropy and mantle…
Development and Utilization of Genetic Probes for Studying Zebra Mussel Veligers
TLDR
An alternative technology to microscopic enumeration of zebra mussel veligers has been developed based on a species specific genetic probe targeting the 18S rRNA molecule that did not hybridize to any other bivalve representative tested.
Long-term observations of foraminifera in situ
ROMEO — the world’s southernmost cabled underwater observatory, located in Explorers Cove, Antarctica, was used to image Cibicides refulgens living epizoically on the scallop Adamussium colbecki…
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