Recent News...

Zehria floridana, a newly described genus and species of cyanobacteria. (Image credit: Mares et al., 2019)

Meet Zehria! A newly described genus of marine N2-fixing cyanobacteria is named in honor of Professor Zehr

April 2019

Jeffrey Johansen (John Carroll University) and colleagues disentangled the phylogeny of Cyanothece-like organisms and described two new genera of cyanobacteria, including Zehria, in a recent article in the Journal of Phycology.

 

Mareš, Jan, Jeffrey R. Johansen, Tomáš Hauer, Jan Zima Jr, Stefano Ventura, Oana Cuzman, Bruno Tiribilli, and Jan Kaštovský. "Taxonomic resolution of the genus Cyanothece (Chroococcales, Cyanobacteria), with a treatment on Gloeothece and three new genera, Crocosphaera, Rippkaea, and Zehria." Journal of phycology (2019). 

See UCSC press release here

Graduate student Katie Harding and colleagues demonstrate cyanobacterial N2 fixation in cold Arctic waters

December 2018

 

See UCSC press release here

Prof. Zehr elected 2018 AAAS Fellow

November 2018

 

See UCSC announcement here

Read a more integrative view and detailed description of the Zehr’s lab work aboard the Falkor here.
Eddy Exploration & Ecosystem Dynamics
Schmidt Ocean Institute
R/V Falkor

Ana Cabello and Rosie Gradoville, April-May 2018

 

The main objective of this cruise was to characterize the deep chlorophyll maximum within the center of eddy fields in the North Pacific Subtropical Gyre using long-range autonomous underwater vehicles (LRAUVs). These self-driving vehicles collect information about water temperature, chemistry, and chlorophyll and also are able to collect and preserve seawater samples at sea to study the microorganisms present. In parallel, our group was performing diel sampling every 3-6 hours from CTD casts, nitrogen fixation incubations on free drifting arrays, and deck-board experiments. These experiments all explored the diversity and activity of nitrogen-fixing bacteria, with special focus on UCYN-A. During the diel sampling we collected DNA, RNA and CARD-FISH samples at different depths to compare UCYN-A transcriptional activity and cell-division rates between surface and deep populations. Our incubation experiments investigated how UCYN-A cell-specific carbon and nitrogen fixation rates vary with depth (from 5 to 125m), and also tested whether UCYN-A is fixing nitrogen during the natural dark period.

What is UCYN-A doing in a coastal shelf ecosystem?
SP1729 R/V Gordon Sproul 

Kendra Turk-Kubo, Ana Cabello, Britt Henke, Brittany Stewart, and honorary Zehr Lab member Jenna Spakeen (VIMS) in collaboration with Matt Mills and Arrigo Lab members (Stanford), October 2017

This was the second of two cruises scheduled this year off the coast of Baja. Our objectives for both cruises were to track growth rates, bulk and cell-specific N2 fixation, nitrate uptake rates, CO2 fixation, and metabolic activities of UCYN-A1 and UCYN-A2 in coastal waters. We also conducted core casts at each station to measure environmental variables including POC/PON, chl a, nutrients (N, P, Si) and take samples to characterize the microbial community composition (DNA/RNA/FCM/CARD-FISH).

Are there Diazotrophs in the Arctic?
Field operations out of BARC &
R/V Sikuliaq

Kendra Turk-Kubo, Britt Henke, Katie Harding, 

August-September 2017

This was our second trip to the Arctic to investigate the spatial extent of nitrogen fixation and which diazotroph species may be active in the Beaufort and Chukchi Sea (Arctic Ocean). Led by Rachel Sipler (VIMS), a team of researchers from VIMS, UCSC, and GIT have come together to study this enigma. 

Follow the blog: https://thedynamicarctic.com

And hear an interview with K. Turk-Kubo about our research: 

https://thedynamicarctic.com/2017/08/16/diazotrophs-in-the-arctic/

Gradients 2.0 cruise in the North Pacific, from the Subtropical Gyre (21°N) to the Subarctic Gyre (43°N). 
R/V Langseth 

Rosie Gradoville and Brittany Stewart, May-June 2017

This cruise tracked the gradients in diversity and biogeochemistry in the North Pacific on a transect from the Subtropical Gyre to the Subarctic Gyre. We steamed north from Honolulu and mapped out the “transition zone” between the two gyres. Then, we turned around and sailed back to Hawaii, collecting samples at stations aimed at characterizing all three regions. The Zehr lab collected samples for DNA, RNA, and fluorescence in situ hybridization (FISH) in order to explore the diversity, abundance, and activity of nitrogen-fixing bacteria along this transect.

 
What is UCYN-A doing in a coastal shelf ecosystem?
SP1714 R/V Gordon Sproul 

Kendra Turk-Kubo, Mary Hogan, Katie Harding, and honorary Zehr Lab members Meredith McPherson (UCSC) and Jenna Spakeen (VIMS) in collaboration with Matt Mills and Arrigo Lab members (Stanford), May 2017

Our objective on this cruise were to track growth rates, bulk and cell-specific N2 fixation, nitrate uptake rates, CO2 fixation, and metabolic activities of UCYN-A1 and UCYN-A2 in coastal waters. We also conducted core casts at each station to measure environmental variables including POC/PON, chl a, nutrients (N, P, Si) and take samples to characterize the microbial community composition (DNA/RNA/FCM/CARD-FISH).

While off the coast of Baja California, we encountered a storm - the seas were high and the boat was small. See the videos to the left! 

 

 
In the News...
Gordon and Betty Moore Foundation awards Himadri Pakrasi (InCEES/WUStl) and Prof. Zehr funding to study the symbiotic relationship between oceanic cyanobacteria and microalgae 

January 2017

Read the press release:

https://incees.wustl.edu/2017/01/26/1-million-grant-awarded-to-i-cares-director-and-ucsc-professor/

Link to the Pakrasi Lab:

https://sites.wustl.edu/photosynthbio/

Prof. Zehr invited to give Plenary talk at The Third Xiamen Symposium on Marine Environmental Sciences

Xiamen, China, January 9-11, 2017

 

http://mel.xmu.edu.cn/conference/3XMAS/

 
Arctic Research Cruise, R/V Sikuliaq, September 3-29, 2016

 

Katie Harding, September 2016

We visited the Arctic to investigate the spatial extent of nitrogen fixation and which diazotroph species may be active in the Beaufort and Chukchi Sea (Arctic Ocean). Led by Rachel Sipler (VIMS), a team of researchers from VIMS, UCSC, and GIT have come together to study this enigma. 

Follow the blog: https://thedynamicarctic.wordpress.com/

And read up on our research goals: 

https://thedynamicarctic.wordpress.com/2016/08/31/an-arctic-fixation/

 
Gradients cruise KOK1606, Transect northbound to 37°N along 158°W

 

Hanna Farnelid and Brittany Stewart, April-May 2016

Our objectives during the Gradients cruise were to characterize diazotroph diversity and abundances across the transition zone region between the North Pacific Subtropical Gyre and the Subpolar Gyre. Along the cruise tract, diazotroph diversity and community composition will be analyzed using nifH amplicon sequencing, quantitative PCR (qPCR) targeting known diazotrophs, and fluorescence in situ hybridization (FISH) targeting the unicellular symbiont UCYN-A. We also conducted mixing experiments between different water masses to simulate what happens in the transition zone.  We had an eventful cruise with a termite swarm (!) and a toilet flooding but seas were mainly calm.

 
SCOPE cruise KM1605, North Pacific Subtropical Gyre

 

Mary Hogan and Kendra Turk-Kubo, March 2015

 

Our research group had several objectives for this cruise: 1) Investigate diazotroph growth rates under various nutrient, light, trace metal and temperature regimes; and 2) Investigate diazotroph grazing rates under different light and temperature regimes.

 
Prof. Zehr in the News:
'This is how scientists will save the Baltic Sea'

 

http://mobil.unt.se/uppland/uppsala/sa-ska-forskarna-radda-ostersjon-3848114.aspx

 
SCOPE cruise KOK1507, 200 miles N. of Station ALOHA

 

Hanna Farnelid, Britt Henke and Kendra Turk-Kubo, July-August 2015

 

Our research group had several objectives for this cruise: 1) Investigate diazotroph growth rates under various nutrient, light and temperature regimes (K. Turk-Kubo); 2) Investigate particle associated and phytoplankton associated bacteria (H. Farnelid), and 3) Continue cultivation efforts to isolate the UCYN-A symbiont (B.Henke).

 
C-MORE/SCOPE cruise C-20, Station ALOHA

 

Maria del Carmen Muñoz-Marin, April 2015

 

During the C-20 cruise, Postdoc Maria del Carmen Muñoz-Marin sampled diel cycles over 3 days for RNA, DNA and CARD-FISH. With these samples she will develop a whole genome array approach for the nitrogen-fixing cyanobacterium UCYN-A1. With this technique, she will try to determine the whole genome transcription patterns related to PSI, energy metabolism and nitrogenase gene expression over light-dark cycles.

 

Moreover, she will study the interaction between the host and the cyanobacterium during light-dark cycles using double CARD-FISH.

 
HOT-269
Kendra Turk-Kubo and Hanna Farnelid, February 2015
 
NEMO Cruise, August 2014
Irina Shilova, Julie Robidart, and colleagues from Stanford, MIT, and the Univeristy of Hawaii

 

In late summer of 2014, the UCSC, Stanford, and UH research team conducted a month long expedition named NEMO (Nutrient Effects on Marine microOrganisms), as a part of our research funded by the NSF Dimensions in Biodiversity program. The objective of the NEMO research cruise was to investigate the role of nitrogen in shaping phytoplankton biodiversity and physiology in the central North Pacific Ocean. Starting from San Diego, CA, they characterized the nutrient rich dynamic waters of the California Current System, followed by an extensive phytoplankton bloom in the middle of North Pacific Ocean, low-nutrient waters and a large Trichodesmium bloom near Hawaii. Through taking various physicochemical and biological measurements along the transect, and conducting nutrient manipulation experiments, they examined how different forms of nitrogenous substrates together with phosphorus and iron alter microbial community structure, physiology and the rates of phytoplankton photosynthesis. 

 

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