title: Remote sensing of bacterial response to degrading phytoplankton in the Arabian Sea.
abstract: A remote sensing technique has been developed to detect physiological condition of phytoplankton using in situ and moderate imaging spectroradiometer (MODIS)-Aqua data. The recurring massive mixed algal bloom of diatom and Noctiluca scintillans in the Northern Arabian Sea during winter-spring was used as test bed to study formation, growth and degradation of phytoplankton. The ratio of chlorophyll (chl) to particulate organic carbon (POC) was considered as an indicator of phytoplankton physiological condition and used for the approach development. Algal blooms represent the areas of new production, and therefore, knowledge of their degradation is important to the study microbial loop and export carbon flux. Relation of chl/POC ratio with bacterial abundance revealed Gaussian distribution. Bacteria were strongly correlated with POC, and hence, the latter which is available from satellite data could be used as a proxy for remote assessment of bacteria. Thresholds for active and degrading phytoplankton were determined using the ratio computed from the satellite data. The criteria were implemented on MODIS data to generate an image representing distribution of degrading algal bloom. Bacteria abundance data from two validation cruises during dinoflagellate and cyanobacteria bloom confirmed well match up of phytoplankton degradation information from the satellite. Comparison of environmental parameters during decay phase of dinoflagellate (N. scintillans bloom (winter) and Trichodesmium bloom (summer) revealed that degradation after active Trichodesmium bloom was more severe as compared to the N. scintillans. The present study also highlights the prediction capability of phytoplankton degradation using a time series of satellite retrieved chlorophyll/POC images.
authors.affiliation: Centre for Marine Living Resources and Ecology (MoES), Kochi, 682 037, India.
authors.forename: P
authors.initials: P
authors.lastname: Priyaja
authors.affiliation: Indian National Centre for Ocean Information Services, Hyderabad, India. rashmindwivedi@gmail.com.
authors.forename: R
authors.initials: R
authors.lastname: Dwivedi
authors.affiliation: Cochin University of Science and Technology, Kochi, 682 022, India.
authors.forename: S
authors.initials: S
authors.lastname: Sini
authors.affiliation: Cochin University of Science and Technology, Kochi, 682 022, India.
authors.forename: M
authors.initials: M
authors.lastname: Hatha
authors.affiliation: Centre for Marine Living Resources and Ecology (MoES), Kochi, 682 037, India.
authors.forename: N
authors.initials: N
authors.lastname: Saravanane
authors.affiliation: Centre for Marine Living Resources and Ecology (MoES), Kochi, 682 037, India.
authors.forename: M
authors.initials: M
authors.lastname: Sudhakar
mesh_terms: D001419:Bacteria / Q000254:growth & development* / Q000302:isolation & purification; D001673:Biodegradation, Environmental; D057486:Carbon Cycle; D002734:Chlorophyll / Q000032:analysis; D017377:Diatoms / Q000254:growth & development / Q000502:physiology; D004141:Dinoflagellida / Q000254:growth & development / Q000502:physiology; D004784:Environmental Monitoring / Q000379:methods*; D005068:Eutrophication; D019156:Indian Ocean; D010839:Phytoplankton / Q000254:growth & development* / Q000502:physiology; D058998:Remote Sensing Technology / Q000379:methods*; D012621:Seasons; D012623:Seawater / Q000737:chemistry / Q000382:microbiology*
chemical_list: D002734:Chlorophyll
keywords: Algal bloom; Arabian Sea; Degradation; Remote sensing