Angela D. Hatton

Bio: Angela D. Hatton is an academic researcher from Scottish Association for Marine Science. The author has contributed to research in topics: Dimethylsulfoniopropionate & Coralline algae. The author has an hindex of 22, co-authored 34 publications receiving 2434 citations. Previous affiliations of Angela D. Hatton include University of East Anglia & Cincinnati College of Mortuary Science.

Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean

Abstract: The idea that iron might limit phytoplankton growth in large regions of the ocean has been tested by enriching an area of 64 km2 in the open equatorial Pacific Ocean with iron This resulted in a doubling of plant biomass, a threefold increase in chlorophyll and a fourfold increase in plant production Similar increases were found in a chlorophyll-rich plume down-stream of the Galapagos Islands, which was naturally enriched in iron These findings indicate that iron limitation can control rates of phytoplankton productivity and biomass in the ocean

Marine Sulphur Emissions

Abstract: The principal volatile sulphur species found in seawater are dimethyl sulphide (DMS), carbonyl sulphide (COS) and carbon disulphide (CS2. Of these, DMS is the most abundant and widespread in its distribution. The predominant oceanic source of DMS is dimethylsulphonioproprionate (DMSP), a compatible solute synthesized by phytoplankton for osmoregulation and/or cryoprotection. Not all species have the same ability to form DMSP; for example, diatoms generally produce little, whereas prymnesiophytes and some dinoflagellates make significantly larger amounts. Much of the release of DMSP and DMS to the water occurs on death or through predation of the plankton. Our recent field data strongly suggest that oxidation of DMS to dimethyl sulphoxide (DMSO) is an important process in the water column, and it is clear that considerable internal cycling in the DMSP/DMS/DMSO system occurs in the euphotic zone. A fraction of the DMS crosses the sea surface and enters the atmosphere where it is oxidized by radicals such OH and NO3 to form products such as methanesulphonate (MSA), DMSO and non-sea salt sulphate (NSSS) particles. These particles are the main source of cloud condensation nuclei (CCN) over oceanic areas remote from land.

Particulate dimethyl sulphoxide in seawater: production by microplankton

Abstract: Dimethyl sulphoxide (DMSO) represents a major pool of dissolved dimethylated sulphur in seawater. However, the origin and fate of this compound in the marine environment, and its role in the biogeochemical cycle of dimethyl sulphide (DMS), remain unclear. The only established route for the formation of DMSO in oxygenated seawater is photochemical oxidation of DMS. It is not known whether significant biotic production pathways exist. In a study of methylated sulphur speciation in coastal North Sea waters and cultures of marine unicellular algae, we measured pools of particulate DMSO (DMSO(p)) at nanomolar and micromolar concentrations, respectively. Analyses of size-fractionated seawater particulates and incubation experiments provided evidence that DMSO(p) was associated with microplanktonic organisms. Log-phase cultures of Amphidinium carterae and Emiliania huxleyi exhibited intracellular dimethylsulphoniopropionate (DMSP) to DMSO molar ratios of 25 and 8, respectively. Our results strongly suggest the existence of biological production and release of DMSO in eukaryotic microplankton.

Influence of photochemistry on the marine biogeochemical cycle of dimethylsulphide in the northern North Sea

Abstract: Shipboard experiments were conducted in the northern North Sea to assess the rate of removal of dimethylsulphide (DMS) and the rate of production of DMSO due to both UVB and UVA/visible light. Experiments were conducted using 0.2-μm filtered seawater and natural light conditions. The DMS photolysis rate constant was determined to be between 0.03 and 0.07 h−1, and initial photolysis rates were between 1.3 and 2.5 nmol dm−3 d−1. Using these rates, the in situ profiles for downward irradiance, and the DMS concentration in the water column, a photochemical turnover rate constant of between 0.1 and 0.37 d−1 was determined for the upper 20 m of the water column, with a photochemical turnover time of between 2.5 and 9.5 days. DMSO photoproduction rates were up to 1.20 nmol dm−3 d−1. Furthermore, results indicate that under UVA/visible light most of the DMS is photo-oxidised to form DMSO, whereas under UVB radiation DMS may be removed via a second photolysis pathway.

The Ecology of Phytoplankton

Abstract: Communities of microscopic plant life, or phytoplankton, dominate the Earth's aquatic ecosystems. This important new book by Colin Reynolds covers the adaptations, physiology and population dynamics of phytoplankton communities in lakes and rivers and oceans. It provides basic information on composition, morphology and physiology of the main phyletic groups represented in marine and freshwater systems and in addition reviews recent advances in community ecology, developing an appreciation of assembly processes, co-existence and competition, disturbance and diversity. Although focussed on one group of organisms, the book develops many concepts relevant to ecology in the broadest sense, and as such will appeal to graduate students and researchers in ecology, limnology and oceanography.

A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization

Abstract: Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the 'iron hypothesis' For this reason, it is important to understand the response of pelagic biota to increased iron supply Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days This drawdown was mostly due to the proliferation of diatom stocks But downward export of biogenic carbon was not increased Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction

A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean

Abstract: The seeding of an expanse of surface waters in the equatorial Pacific Ocean with low concentrations of dissolved iron triggered a massive phytoplankton bloom which consumed large quantities of carbon dioxide and nitrate that these microscopic plants cannot fully utilize under natural conditions. These and other observations provide unequivocal support for the hypothesis that phytoplankton growth in this oceanic region is limited by iron bioavailability.