CALIBRATION ERROR IN THE AMLR PLANKTON TIME SERIES

Analysis of the time series of the volume of water filtered during tows using a 1.8 m Isaac-Kidd Midwater Trawl (IKMT) from 1992 to 2007 showed a marked decline (~35%) in the volume of water filtered beginning in 2000. Analysis of tow time duration, reported ship speed during tows, and mean number of rotor counts from the flow meters showed no significant trends. The discrepancy in volume is traced to a simple arithmetic error in the calculation of the mouth area of the net. Since 2000, the net area was not calculated and instead only the length of the net was used in the determination of the flow constant. Thus, since 2000, the abundance of all zooplankton taxa have experienced a false increase in abundance. Representative corrected time series of Antarctic krill and three species of other Antarctic species is reported. The database has been corrected and protocols are in place to increase the quality control of data in order to ensure data integrity.