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Summary of Abstract Submission

Abstract Submission No.ABS-13-0202
Title of AbstractAmalgamating acoustic and in situ measurements for evaluating zooplankton biomass in the Eastern Arabian Sea with ADCP integration
AuthorsShirin Jadhav*, Kranthikumar Chanda, Smitha B R
OrganisationCentre for Marine Living Resources and Ecology, MoES, Kochi
AddressAt Post Bhosare Taluka Khatav District Satara
Satara, Maharashtra, India
Pincode: 415527
Mobile: 7387523900
E-mail: shirinjadhav64@gmail.com
AbstractEnumerating the plankton and other living organisms are critical towards the understanding of the habitat and the ecological interactions that ultimately are critical input to evaluate the ecosystems and its resources. One of the emerging techniques for the zooplankton biomass estimation is the use of acoustic based instruments/methods through various approaches. Present study explains an attempt that employ a suit of acoustic and in-situ measurements to evaluate the mixed layer zooplankton biomass with Acoustic Doppler Current Profiler (ADCP) integration. The area selected for the study is South Eastern Arabian Sea (SEAS) during May-June and Sept-Oct 2005 on-board the FORV Sagar Sampada. The study employed in situ measurements of vertical zooplankton using Multiplankton Net (MPN), as well as acoustic estimation of zooplankton biomass utilizing the backscatter strength [Sv dB re (4πm)-1] obtained from the Vessel Mounted Broad Band ADCP operating at a frequency of 75 KHz. The backscatter intensity was determined using the operational form of the sonar equation. Data on echo intensity from RDI's VMBB ADCP and MPN collections were made at selected stations in the area 8-21N to 68-76.6E. Regression equations giving the proxy of zooplankton biomass were derived separately for the May-June and Sept-Oct periods using 39 and 58 samples, respectively. The estimation was restricted to the water column up to the mixed layer depth, excluding the upper layer's ringing distance, also taken care to filter the Received Signal Strength Indicator (RSSI) to avoid the influence due to larger DSL organisms like myctophids. ADCP transects and net tows were utilized to capture signals from vertically migrating organisms. The sampling stations were distributed along eight transects at latitudes 8N, 10N, 11.5N, 13N, 15N, 17N, 19N, and 21N. Comparing the acoustic technique-based estimates of zooplankton biomass with conventional techniques, a closer agreement was observed for the May-June period (correlation coefficient R = 0.58), while a weaker correlation was found for the Sept-Oct period (R=0.25). In addition, the study highlights the connection between areas exhibiting significant acoustic backscattering and surface characteristics indicative of a productive environment.
KeywordsAcoustic Doppler Current Profiler,zooplankton biomass,ecological interactions
For Awardsyes
Date Of Birth09-03-1995