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Horn Point Laboratory

Fuchsman Lab

The Fuchsman lab focuses on linking microbes and biogeochemical cycles in low oxygen waters. 

At the moment our lab is particularly focused on the role of organic particles in Oxygen Deficient Zones. Oxygen Deficient Zones are hot spots of N loss from the ocean by N2 production. The microbes mediating this N2 production must either consume organic matter or use by products of organic matter degradation as energy. Thus fluxes of organic C and N2 production are closely linked. Organic particles and the water column are also quite different niches for microbes. Organic particles are rich in organics and reduced N but are transient. The open ocean water column is organic and reduced N poor but stable. Microbes must adapt to respire and reproduce quickly on particles and to acquire scarce resources and reproduce slowly in the water column. Not surprisingly the communities in these two niches are often different.  To examine these systems, we combine field work, lab work and bioinformatics. 

For more information contact Clara Fuchsman: https://www.umces.edu/clara-fuchsman

Eastern Tropical North Pacific Oxygen Deficient Zone Cruises 

There are three naturally occuring regions in the ocean with no oxygen (and no measurable sulfide). The Fuchsman lab is involved in two completed and one upcoming cruises in Mexican waters to study the ETNP Oxygen Deficient Zone

These cruises have a goal of understanding the microbial community, and biogeochemical rates associated with organic particles in anoxic conditions.  In collaboration with Rick Keil (UW), Allan Devol (UW)  and Gabrielle Rocap (UW), we will be looking at meta-genomics, meta-proteomics, in situ rates, sediment trap fluxes, and N2 gas concentrations and isotopes. The offshore Oxygen Deficient Zone is organic matter limited. One question we are interested in answering is how primary productivity by cyanobacteria in the Oxygen Deficient Zone affects organic C fluxes and the activity of the microbial community. 

Oxygen Deficient Zone Microbial Community
 

Our lab studies the microbial community in oxygen deficient water using meta-genomics, with particular interest in the N cycle and sinking particles. 

What biogeochemical processes occur on sinking particles and which bacteria mediate these processes? and which processes and  microbes occur strictly in the water column? and how does this affect the biogeochemistry of the Oxygen Deficient Zone? In the following paper we examine depth distributions of phylotypes of functional genes involved in N cycling both on particles and in the water column:   https://www.frontiersin.org/articles/10.3389/fmicb.2017.02384/full

We have also examined the utilization of small nitrogen containing organic compounds, cyanate and urea, for both assimilation and dissimilation in the ammonium limited Oxygen Deficient Zone: https://academic.oup.com/femsec/article-abstract/94/10/fiy138/5055141 

Currently, we are examining potential sources of organic matter fueling activity in the Oxygen Deficient Zone, including fluxes from the euphotic zone, cyanobacterial primary production in the Oxygen Deficient Zone or micronekton migration into the Oxygen Deficient Zone. This work has implications for predicting microbial activity in the Oxygen Deficient Zone in a changing ocean. 

Evolution and Horizontal Gene Transfer in Low Oxygen Environments

Horizontal gene transfer can increase the fitness of a microbe to its environment. We are interested in the amounts and types of genes acquired by horizontal gene transfer under low oxygen conditions. A recent paper can be found at:  https://peerj.com/articles/3865/In this paper we show increased horizontal transfer between anaerobic archaea and anaerobic bacteria.

Viruses are one vector for horizontal gene transfer because viruses sometime acquire genes from their host. We have been working with Michael Carlson (Technion, IL) to examine host genes specific to cyanobacterial viruses in the ETNP Oxygen Deficient Zone. These viruses are also a way for cyanobacteria to die and become organic particles. 

Stable Isotopes of N2

In situ stable isotopes are one way to track microbial activity in the environment. In our lab, we track the production of N2 gas under anoxic conditions. A recent paper can be found at: 
https://www.sciencedirect.com/science/article/pii/S0967064517301194
In this paper we determine the apparent isotope effect for N2 production in the Eastern Tropical North Pacific and Arabian Sea Oxygen Deficient Zones. The isotope effect is particularly large, which may be explained by the fact that denitrifying bacteria live on organic particles. The isotope effect can then be used in ocean models to determine the amount of N2 production occuring in the entire ocean. 

At sea