Puspa Adhikari is an assistant professor of marine sciences in The Water School at Florida Gulf Coast University. He uses the water and sediments from the ocean to analyze toxins like red tide and organic pollutants and nutrients. His research and teaching interests focus on sediment biogeochemisty, analytical chemistry and radiochemistry.
Areas of Expertise (12)
Marine and Environmental Chemistry
Polycyclic Aromatic Hydrocarbons (PAHs)
Petroleum Geochemistry and Oil Fingerprinting
Gulf of Mexico
Deep Water Horizon Oil Spill
Louisiana State University: Ph.D., Chemical Oceanography 2015
University of Arkansas at Pine Bluff: M.S., Aquaculture and Fisheries 2011
Tribhuvan University: M.S., Environmental Science 2007
Tri-Chandra Multiple Campus, Tribhuvan University: B.S., Environmental Science 2004
- American Geophysical Union : Member
- The Oceanography Society : Member
- Association for the Sciences of Limnology and Oceanography : Member
- Environmental Graduates in Himalayan : Member
- Resources Himalaya Foundation : Member
Selected Media Appearances (3)
FGCU student researchers head to sea to check the red tide-devastated zone they found last year
Puspa Adhikari discusses how he and his students attempt to find the source of nutrients by tracking their radium content.
Under Our Toxic Sea
Florida Weekly - Fort Myers
Puspa Adhikari discusses how he and his students are collecting sea floor and water samples.
Study Demonstrates Sinking Marine Particles Help Remove PAHs from Water Column
Gulf of Mexico Research Initiative
Puspa Adhikari discusses how sinking particles can efficiently transport PAHs from the surface oceans to the seafloor.
Selected Event Appearances (3)
Application of Natural Radioisotope Tracers to Understand Transport and Accumulation of PAHs in Marine Environments
Gulf of Mexico Oil Spill & Ecosystem Science Conference Tampa, Florida
Real time measurement of gas composition from live well fluids at drilling site
Goldschmidt Conference Boston, Massachusetts
Distribution and transport of particle-bound polycyclic aromatic hydrocarbons in a river-influenced continental margin: the northern Gulf of Mexico
American Geophysical Union Fall Meeting New Orleans, Louisiana
Selected Research Grants (3)
Persistence of toxins from harmful algal blooms in coastal marine sediments
Florida Fish and Wildlife Conservation Commission, Red tide initiative $79,999
The 2017-18 red tide severely impacted local ecosystems and economies. While the immediate impacts of this historic event are behind us, there may be more chronic, lingering issues remaining. Brevetoxins, the toxic compounds produced by red tide, are very stable molecules that can persist in the environment, but the magnitude and duration of their risk to the environment are unknown (particularly on the seafloor in biomass that sank to the bottom). The goal of this study, therefore, is to document the persistence of brevetoxins in benthic environments to determine if the 2017-18 red tide is still impacting nearshore environments today.
MRI: Acquisition of a SAGe Well Detector to Support Geoscience Education and Student and Faculty Research at Florida Gulf Coast University
National Science Foundation $180,166
The SAGe Well Detector will allow for research related to Florida's most critical environmental issues such as sea level rise and hurricane impacts, harmful algal blooms, and marine pollution. Having such an essential instrument will greatly assist in the recruitment and retention of high quality STEM-minded students and high quality faculty candidates to the university and will greatly enhance student research participation and provide undergraduate and graduate students with experiences that will increase their chances of recruitment into graduate and research programs. Engaging our students in the use of the SAGe Well Detector will have a significant impact on underrepresented groups in STEM (60% of our students are female and 25% are Hispanic). The university provides outreach and collaborative opportunities to middle and high school research students, local agencies and the general public. Established, ongoing outreach efforts include the STEM High School Girls Summer Camp, the Vester Marine Field Station Marine Science Summer Camp, the Whitaker STEM Teacher Workshop, and the Middle School Science Academy. Finally, the SAGe Well Detector will greatly increase our capability to collaborate with local organizations.
The detector is commonly used to determine the age of soils and sediments in various environments - mainly using Pb-210 and Cs-137-based dating approaches. Historic reconstructions of Floridian coastal, marine and upland environments will provide important research results including those related to past climate change (hurricane and sea-level rise dynamics), eutrophication, hypoxia and marine pollution - all areas of current environmental urgency to the state of Florida. Campus access to this instrument will greatly increase faculty productivity. It will also enhance undergraduate and graduate student participation in courses with student research components, and will therefore aid in long-term student retention. The instrument will be integrated into university curriculum such as Paleoclimatology, Marine Chemistry and Coastal and Watershed Geology helping to engage students in hand-on research.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
Enhanced water quality and seagrass monitoring in the Caloosahatchee Estuary
U.S. Environmental Protection Agency $264,735
We propose to enhance Caloosahatchee River Estuary (CRE) water quality and submerged aquatic vegetation (SAV) resources by combining improved quantitative analyses of existing data with an array of novel monitoring techniques focused on both biotic and physicochemical aspects of the ecosystem. This integrated approach will better characterize the status of CRE SAV in relation to water quality stressors, will better identify nutrient pollution sources that can be targeted by managers, and will help scientists, managers understand the synergistic impacts of salinity fluctuations, nutrient loading, and water column and benthic ecosystem responses to these abiotic drivers. Proposed activities include:
1. Improved water quality monitoring addressing pollutant sources and eutrophication processes:
*We will enhance automated water quality sampling via the Sanibel Captiva Conservation Foundation’s RECON array, adding probes for nitrate, phosphate, and phycocyanin, and doing additional ground-truthing of automated monitoring.
*We will use automated phycocyanin monitoring as a trigger to analyze water samples for cyanobacterial abundance and species composition.
*We will integrate optical water quality monitoring with salinity monitoring and enhanced SAV monitoring to better predict SAV survivability in relation to environmental conditions.
*We will analyze elemental ratios of SAV and anchored algae as a proxy for nutrient availability in the environment and eutrophication stress.
*We will enhance nutrient pollution source tracing by combining stable isotope analysis (15N) with Ra isotope (223Ra, 224Ra, 226Ra, 228Ra) tracing.
2. Improved seagrass resource characterization and benthic habitat inventory in relation to water quality and flow regimes:
*We will map the distribution and species composition of SAV species and macroalgae in the CRE for the first time since Hoffacker (1994), by combining proven quadrat survey methods with an efficient, remotely operated vehicle (ROV) technique.
*We will combine SAV distribution and abundance data with spatially explicit water quality data to improve empirical models of multiple stressor impacts on SAV habitat suitability.
*We will use SAV productivity (shoot growth measurements) to assess physiological responses to short term fluctuations in environmental conditions in the CRE occurring during the monitoring period.
*We will assess the effects of freshwater discharges and nutrient loading on benthic algae
Selected Articles (3)
Puspa L. Adhikari, Kanchan Maiti, Edward B. Overton
Polycyclic aromatic hydrocarbon (PAH) concentrations in dissolved, suspended and sinking phases were measured in the northern Gulf of Mexico during 2012 and 2013 to estimate rate of loss of particulate PAHs from the water column via sinking fluxes. The concentrations of suspended particulate ΣPAH43 varied between 0.29–0.72 ng/L in 2012 and 0.17–1.31 ng/L in 2013 while dissolved ΣPAH43 varied between 31.2–51.2 ng/L and 24.2–58.0 ng/L in 2012 and 2013, respectively. The concentrations of dissolved PAHs were found to be orders of magnitude lower than the values reported during DWH oil spill. Sediment trap-based vertical sinking fluxes of particulate ΣPAH43 varied between 2.21–7.78 μg m− 2 day− 1 in 2012 and 1.95–2.53 μg m− 2 day− 1 in 2013. The vertical fluxes are found to be an important loss term for particle bound PAHs in this region with 3.1–6.7% of total particulate PAH inventory in the euphotic zone being lost daily via this pathway. The reported variability in the sinking rates of particle bound PAHs from the upper ocean can impact the residence time of PAHs in the upper ocean.
Puspa L. Adhikari, Roberto L. Wong, Edward B. Overton
Accurate characterization of petroleum hydrocarbons in complex and weathered oil residues is analytically challenging. This is primarily due to chemical compositional complexity of both the oil residues and environmental matrices, and the lack of instrumental selectivity due to co-elution of interferences with the target analytes. To overcome these analytical selectivity issues, we used an enhanced resolution gas chromatography coupled with triple quadrupole mass spectrometry in Multiple Reaction Monitoring (MRM) mode (GC/MS/MS-MRM) to eliminate interferences within the ion chromatograms of target analytes found in environmental samples. This new GC/MS/MS-MRM method was developed and used for forensic fingerprinting of deep-water and marsh sediment samples containing oily residues from the Deepwater Horizon oil spill. The results showed that the GC/MS/MS-MRM method increases selectivity, eliminates interferences, and provides more accurate quantitation and characterization of trace levels of alkyl-PAHs and biomarker compounds, from weathered oil residues in complex sample matrices. The higher selectivity of the new method, even at low detection limits, provides greater insights on isomer and homolog compositional patterns and the extent of oil weathering under various environmental conditions. The method also provides flat chromatographic baselines for accurate and unambiguous calculation of petroleum forensic biomarker compound ratios. Thus, this GC/MS/MS-MRM method can be a reliable analytical strategy for more accurate and selective trace level analyses in petroleum forensic studies, and for tacking continuous weathering of oil residues.
Puspa L. Adhikari, Kanchan Maiti, Somiddho Bosu, Patrick R. Jones
Particle-mediated vertical flux of polycyclic aromatic hydrocarbons (PAHs) plays an important role in their removal from upper oceans and sets a limit on the amount delivered to the deep-sea sediments. In this study, we applied a one-dimensional steady-state 234Th scavenging model to estimate vertical flux of PAHs in the northern Gulf of Mexico and compared them with sediment trap based flux estimates. The 234Th-based ∑ PAH43 fluxes were 6.7 ± 1.0 μg m− 2 d− 1 and 3.7 ± 0.6 μg m− 2 d− 1 while sediment trap-based fluxes were 4.0 ± 0.6 μg m− 2 d− 1 and 4.5 ± 0.7 μg m− 2 d− 1 at 150 m and 250 m, respectively. Alkylated homologues contributed to 80% of the total PAH fluxes which is in contrary to other regions where combustion derived parent PAHs dominate the fluxes. The results indicate that the 238U–234Th disequilibria can be an effective tracer of particulate PAH fluxes in upper mesopelagic zones and can provide flux estimates with high spatial coverage needed to quantify their long term fate and transport in the marine systems.