The research of my group is broadly concerned with elemental cycling and the effects of environmental change. I work across a range of benthic and pelagic marine ecosystems.
We use a combination of observational, experimental, analytical and technological tools to facilitate our research (detailed below). Please don't hesitate to contact me if you are interested in any of the following work:
Sari Giering (Postdoc and previous PhD student) is looking at the role of zooplankton in the biogeochemistry of our seas. Her next project will examine how the composition of the microplankton community (zooplankton food) influences zooplankton growth and the ways in which they contribute to carbon export and nutrient recycling.
Amy Scott-Murray (PhD student) is developing novel ways to better communicate marine biological research to undergraduate students and academic researchers. She is using a range of digital scanning technologies to generate interactive, 3-D 'digital organisms', spanning from bacteria to fish.
Niki Lacey (PhD student) is looking at the biology of amphipods that inhabit the ultra-deep (>6,000 m) waters of the Kermadec Trench. She is using a combination of lipid- and isotope-based techniques to investigate their nutritional strategies and adaptations to a permanently cold and high-pressure environment.
Charlie Main (Research Assistant and PhD student) is studying how deep-water (>1,000 m) sediment communities respond to a simulated oil release. She is using compound-specific isotopic techniques to determine if and how sediment bacteria are affected by, and even utilise, the introduced hydrocarbons.
Seona Wells (PhD student) aims to better describe the zooplankton communities found to the west and north of Scotland, and how they are likely to respond to a changing environment.
Eleanna Grammatopoulou (PhD student) is examining the make-up and spatial distribution of organic matter and bacteria in the sediments of hadal trenches, the deepest marine environment, and how these relate to the distribution of organisms and their physiological adaptations.
Sarah Breimann (MSc student) is looking at how the fatty acids and isotopic signatures in deep-sea fish differ between tissues and change as the animals grow.
Giannina Hattich (MSc student) is investigating how fish farming activities affect the structure and metabolic functioning of benthic microbial communities.
ARTICLES PUBLISHED/SUBMITTED IN REFEREED JOURNALS
Main CE, Ruhl HA, Jones DOB, Yool A, Thornton B & Mayor DJ. (Submitted). Hydrocarbon contamination affects deep-sea benthic oxygen uptake and microbial community composition.
Pond DW, Tarling GA & Mayor DJ. (2014). Hydrostatic pressure and temperature effects on the membranes of a seasonally migrating marine copepod. PLoS ONE 9: e111043. doi:10.1371/journal.pone.0111043
Mayor DJ, Sanders R, Giering SLC & Anderson TR. (In Press). Microbial gardening in the ocean's twilight zone: Detritivorous metazoans benefit from fragmenting, rather than ingesting, sinking detritus. BioEssays. doi:10.1002/bies.201400100
Giering SLC, Sanders R, Lampitt RS, Anderson TR, Tamburini C, Boutrif M, Zubkov M, Marsay CM, Henson SA, Saw K, Cook K & Mayor DJ. (2014) Reconciliation of the carbon budget in the ocean's twilight zone. Nature 507: 480-483. doi:10.1038/nature13123
Mayor DJ, Gray NB, Elver-Evans J, Midwood A & Thornton B. (2013). Metal-macrofauna interactions determine microbial community structure and function in copper contaminated sediments. PLoS ONE 8(5): e64940. doi:10.1371/journal.pone.0064940
Mayor DJ, Sharples CJ, Webster L, Walsham P, Lacaze J-P & Cousins NJ (2013). Tissue and size-related changes in the fatty acid and stable isotope signatures of the deep sea grenadier fish Coryphaenoides armatus from the Charlie-Gibbs Fracture Zone region of the Mid-Atlantic Ridge. Deep Sea Research II 98: 421-430. doi: 10.1016/j.dsr2.2013.02.030
Anderson TR, Hessen DO, Mitra A, Mayor DJ & Yool A (2013). Sensitivity of predicted secondary production and export flux to choice of trophic transfer formulation in marine ecosystem models. Journal of Marine Systems 125: 41-53. doi: 10.1016/j.jmarsys.2012.09.008
Mayor DJ, Everett N & Cook K (2012). End of century warming and acidification effects on reproductive success in a temperate marine copepod. Journal of Plankton Research. 34: 258-262. doi: 10.1093/plankt/fbr107
Pond DW, Tarling GA, Ward P & Mayor DJ (2012). Wax ester composition influences the diapause patterns in the copepod Calanoides acutus. Deep Sea Research II. 59-60: 93-104. doi:10.1016/j.dsr2.2011.05.009
Mayor DJ & Solan M (2011). Complex interactions mediate the effects of fish farming on benthic chemistry within a region of Scotland. Environmental Research. 111: 635-642. doi:10.1016/j.envres.2011.03.013
Gontikaki E, Mayor DJ, Narayanaswamy BE & Witte U (2011). Feeding strategies of deep-sea sub-Arctic macrofauna of the Faroe-Shetland Channel: combining natural stable isotopes and enrichment techniques. Deep Sea Research I. 58: 160-172. doi:10.1016/j.dsr.2010.11.011
Gontikaki E, Mayor DJ, Thornton B, Black K & Witte U (2011). Processing of 13C-labelled algae by a bathyal community at sub-zero temperatures. Marine Ecology Progress Series 421: 39-50. doi: 10.3354/meps08892
Mayor DJ, Cook K, Thornton B, Walsham P, Witte U, Zuur, AF & Anderson TR (2011). Absorption efficiencies and basal turnover of C, N and fatty acids in a marine Calanoid copepod. Functional Ecology 25: 509-518. doi: 10.1111/j.1365-2435.2010.01791.x
Mayor DJ, Zuur AF, Solan M, Paton GI & Killham K (2010). Factors affecting benthic impacts at Scottish fish farms. Environmental Science and Technology 44: 2079-2084. doi: 10.1021/es903073h
Jamieson AJ, Fujii T, Mayor DJ, Solan M & Priede IG (2010). Hadal Trenches: the ecology of the deepest places on Earth. Trends in Ecology & Evolution 25: 190-197 doi:10.1016/j.tree.2009.09.009
Mayor DJ, Solan M, McMillan H, Killham K & Paton GI (2009a). Effects of copper and the sea lice treatment Slice® on nutrient release from marine sediments. Marine Pollution Bulletin 58: 552-558 doi: 10.1016/j.marpolbul.2008.11.015.
Mayor DJ, Anderson TR, Pond DW & Irigoien X (2009b). Egg production and associated losses of carbon, nitrogen and fatty acids from maternal biomass in Calanus finmarchicus before the spring bloom. Journal of Marine Systems 78: 505-510 doi: 10.1016/j.jmarsys.2008.12.019
Mayor DJ, Anderson TR, Pond DW & Irigoien X (2009c). Limitation of egg production in Calanus finmarchicus in the field: a stoichiometric analysis. Journal of Marine Systems 78: 511-517 doi: 10.1016/j.jmarsys.2008.12.020
Castellani C, Irigoien X, Mayor DJ, Harris R & Wilson D (2008). Feeding of Calanus finmarchicus and Oithona similis on the microplankton assemblage in the Irminger Sea, North Atlantic. Journal of Plankton Research 30: 1095-1116 doi: 10.1093/plankt/fbn074.
Heath MR, Rasmussen J, Ahmed JY, Allen J, Anderson C, Brierley AS, Brown L, Bunker A, Cook K, Davidson R, Fielding S, Gurney WSC, Harris R, Hay S, Henson S, Hirst AG, Holliday PN, Ingvarsdottir A, Irigoien X, Lindique P, Mayor DJ, Montagnes D, Moffat C, Pollard R, Richards S, Saunders RA, Sidey J, Smerdon G, Speirs D, Walsham P, Waniek J, Webster L & Wilson D (2008). Spatial demography of Calanus finmarchicus in the Irminger Sea. Progress in Oceanography 76: 39-88 doi:10.1016/j.pocean.2007.10.001.
Mayor DJ, Solan M, Martinez I, Murray L, McMillan H, Paton GI & Killham K (2008). Acute toxicity of UK-registered sea lice treatments to Corophium volutator and Hediste diversicolor: whole sediment bioassay tests. Aquaculture285: 102-108 doi: 10.1016/j.aquaculture.2008.08.008.
Mayor DJ, Matthews CA, Cook K, Zuur AF & Hay S (2007). CO2-induced acidification affects hatching success in keystone copepods. Marine Ecology Progress Series 350: 91-97 doi: 10.3354/meps07142.
Mayor DJ, Anderson TR, Irigoien X & Harris R (2006). Feeding and reproduction of Calanus finmarchicus during non-bloom conditions in the Irminger Sea. Journal of Plankton Research 28: 1167-1179 doi:10.1093/plankt/fbl047.
Allen JT, Brown L, Sanders R, Moore, M, Mustard A, Fielding S, Lucas M, Rixen M, Savidge G, Henson S & Mayor DJ (2005). Diatom carbon export enhanced by silicate upwelling in the northeast Atlantic. Nature 437: 728-732 doi:10.1038/nature03948.
Wheeler AJ, Bett BJ, Billett DSM, Masson DG & Mayor DJ (2005). The Impact of Demersal Trawling on NE Atlantic Deep-Water Coral Habitats: the Darwin Mounds, U.K. In: Benthic Habitats and the Effects of Fishing, America Fisheries Society, Bethesda, Maryland, USA. (Ed. Peter Barnes).
OTHER PUBLISHED ARTICLES
Mayor DJ. Plankton in the open ocean. MARBEF (European Union) 'Marine Biodiversity Wiki' http://www.marbef.org/wiki/Marine_Plankton
Mayor DJ (2009). The carbon crunch. British Ecological Society Bulletin: Marine special issue.
Mayor DJ (2009). Event report: 'Inspiring oceans'. Challenger Wave (Challenger Society news letter).
Mayor DJ (2008). Acid oceans. Planet Earth magazine (NERC). Summer 2008, 22-23. http://www.nerc.ac.uk/publications/planetearth/2008/summer/sum08-acidoceans.pdf
Mayor DJ & Cook K (2008). The Water Flea: Source of all life in our seas. Leopard Magazine: Feb'08, 21-22.
Solan M, Mayor DJ, Murray L, Paton GI & Killham K (2008). Coastal assimilative capacity for amalgamated fish farm chemicals/organic inputs. Final report to SARF, April 2008.
Mayor DJ (2007). Feature article: The carbon conundrum. Petroleum Review: 61 (728): 13.
Blackford J, Austen M, Halloran P, Iglesias-Rodriguez D, Mayor DJ, Pearce D & Turley C (2007). Report to DEFRA arising from the AMEMR workshop: Modelling the response of marine ecosystems to increasing levels of CO2.
Mayor DJ (2005). Challenger Society Special Interest Group and the NERC Marine Productivity programme - Biophysical Interactions in High Latitude Oceans. British Antarctic Survey (Cambridge), 20 - 21 April 2005. Ocean Challenge 14: 22-23.
I mark Honours student theses/oral presentations and write/deliver the following lectures to 2nd/3rd/4th year undergraduate (Honours) students:
Ocean Biology (BI25Z2):
Copepods, 1 × 1 hr;
Marine Ecology and Ecosystems (ZO3304; Course Coordinator):
Ocean acidification: The other side of the CO2 story, 4 × 0.5 hr;
Aquatic Biology (ZO3809):
Zooplankton interactions, 2 × 1 hr;
Marine Benthic Ecology (ZO4808):
Sampling the marine benthos, 2 × 1 hr;
Adaptations to soft sediments, 2 × 1 hr;
Adaptations to sandy sediments, 2 × 1 hr;
Factors influencing marine benthic community structure, 2 × 1 hr;
Organic matter in marine sediments: Food quantity vs food quality, 2 × 1 hr;
Sustainable Aquaculture (ZO4811):
Environmental impacts of aquaculture, 2 × 1 hr
Marine sediments store billions of tonnes of carbon, making them one of the Earth's largest carbon reservoirs. Their importance in the global carbon cycle has long since been acknowledged, but the factors that influence the fate of organic material arriving at the seabed remain poorly understood. It is therefore difficult to make reliable predictions about how the role of marine sediments in global biogeochemical cycles will be altered by future climate change.
Stable isotope 'pulse-chase' experiments, in which a pulse of 13C-labelled organic material is introduced to the sediments and the fate of the 13C tracer is followed over time, represent a powerful technique for exploring carbon cycling. I am currently undertaking benthic pulse-chase experiments to examine the factors that affect carbon cycling in marine sediments. This work involves collaborations with scientists from the Marine Scotland Science, Aberdeen, the James Hutton Institute.
I am also using benthic mesocosm experiments to examine how some of the therapeutic treatments used in marine aquaculture affect the ability of marine sediments the generate inorganic nutrients. For more information, see the section below on 'The environmental impacts of aquacluture'.
Burning fossil fuels to produce energy is releasing billions of tonnes of carbon dioxide (CO2) into our atmosphere. The associated phenomenon of 'global warming' is now widely accepted, and has received considerable media interest. Conversely, the concept of 'ocean acidification' is almost unheard of outside of the scientific community. The Royal Society's recent report has highlighted the almost complete lack of knowledge on how the oceans and their 'keystone' organisms will be affected by CO2-induced acidification. As explained above, the copepod C. finmarchicus is one such keystone organism that lives in the North Sea and North Atlantic.
I am particularly interested in how elevated CO2 concentrations affect the biology and ecology of these animals. Our preliminary research, conducted in collaboration with the Fisheries Research Services (FRS) Aberdeen, has found that the reproduction of C. finmarchicus is significantly impaired at a pH of 6.95 ([CO2] = 8000 ppm). Click here for a short report. This concentration is not predicted to occur until 2300, and then only if we manage to extract and burn all of the world's hydrocarbon reserves. However, 'carbon capture and storage' (CCS) initiatives that will collect industrial CO2 and store it in the marine environment (e.g. down old oil wells and in the deep ocean) have the potential to acidify large volumes of seawater. It is clear that the costs and benefits of CCS initiatives need to be carefully weighed against those of increasing atmospheric concentrations of CO2. Click here to see the 'Acid Oceans' article (picture above) in the NERC's 'Planet Earth' magazine.
We are currently looking at the sub-lethal effects of 'environmentally-relevant' CO2 concentrations that will inevitably occur in the next 50-100 years.
Calanus finmarchicus (pictured above) is a tiny water flea-like crustacean that lives in the North Atlantic and northern North Sea. They serve as an essential interface between the microscopic primary producers and juvenile fish such as cod, and are therefore essential for healthy fish stocks. Time-series observations in the North Atlantic suggest that the abundance of Calanus has fallen dramatically over the past 50 years, and some claim that this a contributing factor to the poor recovery of heavily exploited cod stocks.
The egg production (growth) of marine copepods is positively correlated with the quantity of available organic carbon (food quantity), which is required for both the production of energy and new tissues. However, other research shows that their egg production also correlates with descriptors of food 'quality' i.e. other nutrient elements and compounds that cannot be synthesized by the animals, but are also required for healthy growth and reproduction. These include nitrogen and 'omega-3' polyunsaturated fatty acids.
The question is; 'which component of the diet is responsible for limiting their growth?'
My PhD directly addressed this question by experimentally determining the supply and demand of carbon, nitrogen and 'omega-3's' in C. finmarchicus, and used stoichiometric theory to help me understand which component of the diet was most limiting. Stoichiometric theory isn't as daunting as it may sound. To explain; if I started up a ham and tomato sandwich factory, the number of sandwiches that I can produce is potentially determined by the supply of A) bread, B), ham, or C) tomato. If each sandwich is made from 2 units of bread, 1 unit of ham and 1 unit of tomato, the 'demand ratio' is 2 bread : 1 ham : 1 tomato. This is assuming that I can use each component with 100 % efficiency. If I can only use half of every tomato i.e. 50 % efficiency, the demand for tomatoes immediately doubles. If my supply of bread, ham and tomatoes is at the ratio 2:1:1, tomatoes will limit my production line. Stoichiometric theory provides the mathematical framework for me to determine which component is most likely to be limiting. When I know the demand ratio of my production line, I can monitor the supply of bread, ham and tomatoes and predict which is most likely to limit my factory's productivity. In the same way, if we compare the supply and demand of dietary components for copepods in the natural environment, we can predict which substrate is limiting their growth.
The experimental component of my PhD was conducted in the northern North Atlantic, between Iceland and Greenland. One of the surprise results was that in April, before the spring bloom, C. finmarchicus was reproducing at a personal cost: they were breaking down their own body proteins in order to sustain their reproductive efforts. Proteins are rich in nitrogen, and perhaps not surprisingly, the stoichiometric model predicted that the supply of carbon was most likely to have been limiting their egg production.
This project aims to better understand the broader ecological impacts of marine aquaculture. In particular, we wish to know: 'is there a relationship between the 'size' of a fish farm and its 'area of impact?' We are addressing this question in the field, and have already mapped the biological and chemical properties of sediments around numerous fish farms using a combination of traditional and state-of-the-art sampling techniques. These include sediment grabs and a Sediment Profile Imaging (SPI) camera respectively.
The SPI camera is a wire-deployed imaging system used to observe spatial and temporal patterns of biological activity on and below the sediment-water interface. SPI is essentially a vertically mounted camera that faces down into a 45 degree mirror – like an upside-down periscope. The mirror and camera are housed in a water-tight surround that is forced into the sediment. The resulting photos are horizontal, cross-sectional images of the sediment. These provide us with information about the overall 'health' of the sediment and the biological communities that they support.
We are also interested in learning about the more subtle impacts associated with the therapeutic treatments used to remove sea lice from farmed fish; 'do these 'medicines' also have an effect on non-target organisms that inhabit the sediments beneath fish farms? If so, are certain organisms more susceptible than others, and would their extinction change how the ecosystem functions?' More information about this project can be found here.