Kevin M. Johnson

Phone: (805) 893-6176
Email: Kevin.Johnson"at"lifesci.ucsb.edu
Office: MSRB 2409
CV

Research

My research is focused on combining molecular techniques with physiological and morphological measurements to understand how marine organisms respond to abiotic stress. An important component of this work is using observations of the natural environment to develop environmentally relevant experiments. As a molecular ecologist, I believe that exploring these genotype x environment responses is crucial to accurately predicting how organisms will respond to future environments. 

Antarctica

As a member of the Hofmann lab Antarctic science team (B-134) I have focused on two key questions: (1) To understand how the Antarctic pteropod Limacina helicina antarctica responds to the natural pH variability in McMurdo Sound and (2) To understand the range of plasticity that pteropods have to deal with future ocean acidification conditions.  To address these questions I have spent two field seasons (2014-2015 and 2015-2016) in McMurdo station and have combined field collections with laboratory manipulation experiments.  

In order to accurately address these questions from a molecular perspective, I first had to generate the molecular tools.  Specifically, I used  RNA sequencing to build a de novo transcriptome for L.h.antarctica using pteropods from a variety of abiotic conditions.  This approach has lead to the development of a robust transcriptome for Limacina that was published in Marine Genomics in 2016. The development of this tool, this de novo transcriptome, now allows for more targeted RNA sequencing with the goal of identifying gene expression patterns in Limacina that describe the degree of stress pH variability has on Limacina. 

To accurately describe how Limacina responds to pH variability, I completed a series of laboratory experiments where I held pteropods at a range of pH levels for extended incubation periods.  During the course of these experiments, I collected samples to look at gene expression changes as the pteropods use all of their molecular tools to maintain their shell structure in a more acidic environment.  This is currently in  the analysis stages so stay tuned to hear how Limacina responds to ocean acidification and warming.


Pacific Ocean

I am also working with pteropods closer to home and I have been invited to join NOAA's Pacific Marine Environmental Laboratory (PMEL) for  the 2016 West Coast Ocean Acidification Cruise (WCOAC) to collect Limacina helicina helicina on board the NOAA Ship Ronald H. Brown.  

In the last 40 years there has been a 10% increase in under-saturated surface waters as a result of wind-driven upwelling moving deep offshore-water (200 m) up onto the continental shelf and into the surface waters. In 2007, the first West Coast Ocean Acidification Cruise observed upwelled, under-saturated waters along the Coast of California, Oregon and Washington at depths of 40 - 120 m and into the surface waters in Northern California. These upwelling events present an opportunity to explore patterns in gene expression with Limacina collected from a range of pH conditions. My goal for the 2016 cruise is to capture the in-situ molecular response of Limacina  across upwelling zones and to look for the transcriptomic signals of physiological stress identified in the Antarctic laboratory experiments.


Publications

Johnson, K.M., and G.E. Hofmann (2016) A transcriptome resource for the Antarctic pteropod Limacina helicina antarctica. Marine Genomics 28:25-28.​ doi:10.1016/j.margen.2016.04.002

Johnson, K.M., U. Hoshijima, C.S. Sugano, A.T. Nguyen, and G.E. Hofmann (2016) Shell dissolution observed in Limacina helicina antarctica from the Ross Sea, Antarctica: paired shell characteristics and in situ seawater chemistry. Biogeosciences Discussions: doi:10.5194/bg-2016-467