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.
Algal blooms are increasing around the world in frequency, duration as well as geographical distribution. This expansion has been at a huge environmental cost- an environmental cost with ramification that includes human health, ecological health and enormous economic costs. Harmful algal blooms are those proliferations of algae that can cause fish and shellfish kills, produce toxins harmful to human health, and develop biomass accumulations that can alter ecosystems in other deleterious ways. Since the 1990s such blooms have been occurring with increased frequency in the Arabian Sea and the Gulf of Oman. The recent blooms are now having a large impact on the food web, the carbon cycling, and the nitrogen cycling of this ocean. A particularly severe bloom in 2008 resulted in fish kills and economic consequences, including damage to intake filters of desalination plants. This study advanced our knowledge of the blooms in this region in several ways. First, this study contributed to the first global review of the distribution and factors associated with the major bloom-forming species, Noctiluca scintillans. Although this species is functionally a heterotroph, this review established that Noctiluca may be a coastal or offshore manifestation of eutrophication in some areas, since an increase in nutrients provides an increase in phytoplankton, its main food supply as a grazer. Second, this study provided analyses and evaluation of the environmental factors associated with the major bloom of the species, Cochlodinium polykrikoides, that occurred in the coastal waters of Oman in 2008. It was concluded that the bloom was likely facilitated through the mesoscale forcing towards the coastal regions, while the occurrence and persistence of high densities of C. polykrikoides was significantly influenced by the increased nutrient load observed at that time. Specific rates of nitrogen uptake by bloom species were also assessed on cruises conducted in 2010 and 2011. The broader impacts resulting from this project included partial support for one graduate student, as well as training for international students from both India and Oman on the application of stable isotope techniques. An article on harmful algal blooms in Asia was prepared for a journal that targets undergraduate students. The results were also presented to forums that included management agency personnel in Oman and Kuwait. These agencies were and are interested in developing prevention, control, and mitigation strategies to prevent harmful algal blooms or to minimize their impact when they do occur. Three journal articles resulted from this study.
