RAPID: Sources and Fates of Nitrogen and its Role in Supporting Dinoflagellate Blooms in the Arabian Sea

University Of Maryland Center For Environmental Sciences, Cambridge MD

Investigators

Abstract

In the past several years, a massive expansion of dinoflagellate blooms has occurred in the Arabian Sea. These blooms are dominated by the heterotrophic dinoflagellates Nocticula milaris. Moreover, along the Oman coast, blooms of the dinoflagellate Cochlodium polykrikoides were seen on a massive scale for the first time last year. These blooms are now are having a large impact on the food web, the carbon cycling, and the nitrogen cycling of this ocean. Rates of primary productivity are higher than previously reported, the oxygen minimum zone is more intense, and denitrification rates are very high. Thus, this is a system that is rapidly changing and one in which nitrogen pathways and processes may be significantly altered in years to come as climate and eutrophication forces become more pronounced. This project will supplement previously funded efforts making primary production and grazing rate measurements by directly addressing the question of the source and fate of nitrogen supporting these blooms. Specifically, this project will conduct, in collaboration with US, Indian and Omani colleagues, a suite of process measurements to assess the rates of nitrogen uptake, nitrogen fixation, and nitrogen cycling, and integrate these measurements into the broader suite of measurements on this rapidly changing system to better understand the nitrogen dynamics supporting these blooms. There is a particular concern over the emergence and expansion of blooms of Nocticula milaris, blooms that were not present a decade ago but which now are having a large impact on the trophodynamics and biogeochemistry of this ocean. Large-scale blooms of the ichthyotoxic dinoflagellate Cochlodinium have only emerged in the past year. This project provides a unique opportunity for establishing long term international collaboration with Indian and Omani scientists. Indian students will be trained in the techniques of15N isotopic tracers. In addition, one REU student will be hired for the summer of 2010 to help with sample and data analysis. It is hoped that this REU student would be interested in furthering his/her studies and would apply for graduate study with a focus on these complex and changing blooms. This work will be integrated and leveraged with other ongoing efforts to convey the importance of climate change and eutrophication to a broad range of students and the public.