The physiological and ecological functions of volatile halogen production by marine diatoms

Lead Research Organisation: University of York
Department Name: Environment

Abstract

The oceans are a major reservoir of halogens including chlorine, bromine and iodine in the form of halide ions. Various biological and chemical reactions convert the halides to volatile halogen species which can move across the sea surface and into the atmosphere. The volatile halogens produced in the marine environment include organic compounds like CH2I2 and CH2BrI and reactive inorganic species like I2 and Br2. Once in the atmosphere the halogens are involved in ozone cycling and can influence the formation of clouds. A major source of organic and inorganic volatile halogens in the oceans is a phytoplankton group known as diatoms which live in open waters and in sea-ice. While experiments have shown that diatoms produce volatile halogens we do not understand why they do this or how it might impact other organisms around them. One idea is that diatoms produce volatile halogens to protect themselves against damage from reactive oxygen species and another is that they do this to defend themselves against other microbes or grazing invertebrates. It is important that we understand the reasons why diatoms produce the volatile halogens so we known when and where halogen emissions from the oceans to the atmosphere will take place and are able to predict how climate change will influence this. This is especially crucial for polar regions experiencing rapid warming where climate-induced changes in diatom communities have already been seen. In this study I will carry out laboratory experiments to explore if volatile halogen production helps to protect the diatoms from oxidative stress and if this has any impact on the abundance or composition of bacteria in the seawater around them. This will allow me to produce mathematical relationships that describe volatile halogen production by diatoms in the presence of bacteria. These relationships will allow computer models of volatile halogen production in seawater to be developed which will tell us how halogen emissions will change in the future and how this will impact atmospheric chemistry.

Planned Impact

The following summary lists potential users of the proposed research and how each will benefit from it:

- Research scientists studying halogen biogeochemistry
This work will create new knowledge on volatile halogen production in seawater which will contribute to the development of modelling tools that can be used to accurately predict the impact of climate change on sea-to-air halogen flux and associated atmospheric processes such as ozone depletion and new particle formation. This will help marine and atmospheric investigators to gauge where to position halogen biogeochemistry in the ranking of priority topics for future research.

- The wider scientific community and delivering bodies
The wider scientific areas that will benefit from the new knowledge gained through this work include microbial physiology, biogeochemical modelling, atmospheric chemistry and climate system feedbacks. An improved understanding of the physiological and ecological functions of volatile halogen production will allow researchers in these areas to determine how this process fits within their own work.

Additionally, an understanding of how volatile halogen production by diatoms will change with future climate-induced stresses to ocean systems will help scientists and delivering bodies, such as the UK Met Office, to resolve the importance of including halogen biogeochemistry in climate models.

- Intermediary organisations
By contributing to new scientific knowledge and providing parameterisations that can be used in 3-D climate models, the results of this study may feed in to assessments and reports produced by intermediary organisations [e.g. Intergovernmental Panel on Climate Change, World Meteorological Organisation] which are at the interface between basic research and policy.

- School children
The concept behind this work is that microbes can play an important role in processes occurring at the global scale. I will present this exciting and intriguing topic to school children at University of York Science Awareness events to 'engage young people with contemporary research to enhance their experience of science, encouraging more to pursue science studies.....' which is a key aim of the RCUK Science and Society Strategy.

Publications

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Atkinson H (2014) Halocarbons associated with Arctic sea ice in Deep Sea Research Part I: Oceanographic Research Papers

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Küpper FC (2018) Emission of volatile halogenated compounds, speciation and localization of bromine and iodine in the brown algal genome model Ectocarpus siliculosus. in Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry

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Von Glasow, R And Hughes, C (2014) Encyclopedia of Atmospheric Sciences

 
Description 1. The diatoms Thalassiosira antarctica and Porosira glacialis produce haloperoxidase enzymes. This results expands our knowledge of the occurrence of haloperoxidases in marine diatoms.

2. Haloperoxidase activity in Thalassiosira antarctica increases with photosynthetic rate and ambient hydrogen peroxide concentrations suggesting that these enzymes are involved in photosynthetic reactive oxygen species scavenging. Responses were less strong but were also observed for Porosira glacialis suggesting that controls on haloperoxidase activity may vary between diatom species.

3. Haloperoxidase activity in Thalassiosira antarctica and Porosira glacialis has a diel cycle with increased activity in the light. Again, this finding supports the idea that the haloperoxidases are produced to prevent oxidative stress in the diatoms.

4. Haloperoxidase activity is not influenced by the presence of bacteria in the diatom cultures.

5. The growth of the bacterium Gelidibacter algens, isolated from sea-ice algae, is not reduced at ambient halocarbon concentrations suggesting that haloperoxidase production in marine diatoms is not linked to antimicrobial defence.
Exploitation Route The new knowledge on the occurrence and controls on halogenating activity we have produced through this grant is potentially of use for the antifouling paints industry in which haloperoxidases have recently started to be used.
Sectors Manufacturing, including Industrial Biotechology

 
Description Environment Department Overseas PhD Student Bursary
Amount £30,000 (GBP)
Organisation University of York 
Sector Academic/University
Country United Kingdom
Start 02/2014 
End 01/2017
 
Description Environment Department Research Priming Fund
Amount £2,000 (GBP)
Organisation University of York 
Sector Academic/University
Country United Kingdom
Start 10/2014 
End 03/2015
 
Description NERC Standard/Discovery Grant
Amount £554,617 (GBP)
Funding ID NE/N009983/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 08/2016 
End 07/2019
 
Description University of York Research Priming Fund
Amount £41,864 (GBP)
Organisation University of York 
Sector Academic/University
Country United Kingdom
Start 08/2014 
End 07/2015
 
Description British Antarctic Survey Collaborative Gearing Scheme 
Organisation British Antarctic Survey
Country United Kingdom 
Sector Academic/University 
PI Contribution Personnel and equipment to make measurements made at the Rothera Time-Series site during the 2015/2016 summer season.
Collaborator Contribution Travel costs to Antarctica, and living and laboratory space at the Rothera Research Station.
Impact There are no outcomes yet but the work will be written up for publication. The project involves researchers working on physical, chemical and biological oceanography.
Start Year 2016
 
Description Challenger Society for Marine Science, Genes to Gases meeting at University of East Anglia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact This multidisciplinary meeting examined the metabolic pathways and their control at the molecular level that affect the dynamics of a wide range of volatile compounds and precursors in the marine biosphere. It combined these approaches with research on in-situ field measurements and lab-based, process-orientated studies, thus providing the research community with a holistic overview of the subject ranging from molecular ecology, tracking these microbes that are involved in key biogeochemical cycles, understanding the metabolism (key genes, enzymes and pathways) of these compounds, regulation of these processes , measurements of trace gas/precursor production, biological and chemical oceanography, atmospheric chemistry and modelling of these processes. Discussions identified future directions in this research area encompassing multiple disciplines.
Year(s) Of Engagement Activity 2017
 
Description Invited Seminar speaker (Kiel, Germany) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talks and discussions with staff at IFM Geomar in Kiel have led to the recruitment of a PDRA from the institute for a NERC research project.
Year(s) Of Engagement Activity 2015
 
Description Invited seminar (Chicheley Hall, Royal Society Meeting, In icy waters) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Seminar at Royal Society International Meeting at Chicheley Hall ('In icy waters'). Attendees included a wide range of international scientists from a wide range of research areas. Sparked lots of discussion and has led to the development of a review paper on future scientific direct for western Antarctic Peninsula Research.
Year(s) Of Engagement Activity 2017
URL https://blogs.royalsociety.org/inside-science/2017/05/31/what-is-going-on-in-the-oceans-around-the-w...
 
Description Invited seminar speaker (Newcastle) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Around 40 undergraduate, postgraduate students studying in the School of Marine Science and Technology at the University of Newcastle attended the seminar alongside their lecturers. This sparked questions from the students and discussions with potential future projects with postgraduates and academic staff.
Year(s) Of Engagement Activity 2008,2017
 
Description Presentation at European Geophysical Union General Assembly (Vienna) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The physiological and ecological roles of volatile halogen production by
marine diatoms
Claire Hughes and Shuo Sun
Environment Department, University of York, Heslington, York, YO10 5DD, United Kingdom
Sea-to-air halogen flux is known to have a major impact on catalytic ozone cycling and aerosol formation in
the troposphere. The biological production of volatile organic (e.g. bromoform, diiodomethane) and reactive
inorganic halogens (e.g. molecular iodine) is believed to play an important role in mediating halogen emissions
from the marine environment. Marine diatoms in particular are known to produce the organic and inorganic
volatile halogens at high rates in pelagic waters and sea-ice systems. The climate-induced changes in diatom
communities that have already been observed and are expected to occur throughout the world's oceans as warming
progresses are likely to alter sea-to-air halogen flux. However, we currently have insufficient understanding of the
physiological and ecological functions of volatile halogen production to develop modelling tools that can predict
the nature and magnitude of the impact.
The results of a series of laboratory studies aimed at establishing the physiological and ecological role of
volatile halogen production in two marine polar diatoms (Thalassiosira antarctica and Porosira glacialis) will be
described in this presentation. We will focus on our work investigating how the activity of the haloperoxidases, a
group of enzymes known to be involved in halogenation reactions in marine organisms, is altered by environmental
conditions. This will involve exploring the antioxidative defence role proposed for marine haloperoxidases by
showing specifically how halogenating activity varies with photosynthetic rate and changes in the ambient light
conditions in the two model marine diatoms.We will also present results from our experiments designed to investigate
how volatile halogen production is impacted by and influences diatom-bacterial interactions. We will discuss
how improved mechanistic understanding like this could pave the way for future volatile halogen-ecosystem
model development.
Year(s) Of Engagement Activity 2015
URL http://meetingorganizer.copernicus.org/EGU2015/EGU2015-11836-1.pdf
 
Description Session Convenor at European Geophysical Union General Assembly (Vienna) 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact OS3.1 Sensitivity of marine ecosystems and biogeochemical cycles to global change
Integrated studies of the sensitivity of marine ecosystems and biogeochemical cycles to global change are essential to understand how biogeochemical cycles and marine ecosystems interact together and with the changing global environment and help prepare the responses of society to regional and global marine change. To develop a comprehensive understanding of, and accurate predictive future capacity for, physical, biogeochemical, and ecosystemic ocean responses to accelerating anthropogenic global change on time scales ranging from years to decades, and the consequent marine feedbacks on the Earth System. This IMBER / SOLAS session calls for contributions related to experimental work at sea or in the laboratory, theoretical, modelling and remote sensing studies on the responses of key marine biogeochemical cycles, the structure and functioning of oceanic ecosystems and their interactions with each other and to global change. Contributions dealing with exchange processes at the air-sea interface, with mesoscale and sub-mesoscale processes and associated with oxygen minimum zones are also welcome.
Year(s) Of Engagement Activity 2015
URL http://meetingorganizer.copernicus.org/EGU2015/session/17344
 
Description Student visit days (York) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Presentations at undergraduate open days at the University of York, Environment Department Open Days

After the talk A level students contacted me for further information for inclusion in their coursework. Increased interest in undertaking a degree in environmental science.
Year(s) Of Engagement Activity 2012,2013,2014,2015,2016
 
Description Workshop to discuss future research (British Antarctic Survey, Cambridge) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Study participants or study members
Results and Impact Submission of a NERC large grant outline to the March 2017 round
Year(s) Of Engagement Activity 2017