Broad-scale biovolume and bioacoustic backscattering data
are being compared to examine seasonal and the year to year variations. The kriging technique and a newly developed
wavelet/fractal interpolation scheme is being applied to the acoustic and
biovolume data sets to obtain 3D volume renditions.
1)
Work is being completed on data collected on cruises in the fall 1997,
1998, and 1999
to survey diapausing populations of Calanus finmarchicus and their predators in the Gulf of Maine
using MOCNESS and BIOMAPER-II. Following the precipitous drop in the NAO index that
occurred in 1996, colder and fresher water of Labrador Sea origin entered the Gulf
of Maine in 1998 after a lag of about two years. Coincidently, the autumn diapausing C. finmarchicus abundance was much lower
in 1998 than in 1997 or 1999. Despite the substantially lower Calanus abundance in 1998, overall zooplankton biomass levels as
revealed by net catches and acoustic indices were comparable between the three years. Potential competitors (other copepods, the
pteropod Limacina
retroversa), and predators (euphausiids, decapods, medusae, and siphonophores) had
enhanced biomass and/or numbers, which may explain the reduced Calanus in 1998.