Water samples were collected from 250 to 1000 or 1100 m depth.
On cruises TTN043 and TTN045 aliquots totaling 4-9 liters per depth were taken from two 10 liter Niskin bottles. On cruises TTN050 and TTN054 entire contents (42-59 liters) of six 10 liter Niskin bottles per depth were used. Organisms were then concentrated within ~ 225 ml by the reverse filtration technique (Dodson and Thomas 1978) with 20 micrometer pore sized NitexTM mesh. Concentrated samples were measured and preserved in glass jars with a solution of 20% paraformaldehyde in 5% sodium borate to give a final concentration of 2% paraformaldehyde. Entire samples were settled in the dark at 4 degrees C in chambers to which a drop of a 1 mg per ml aqueous solution of DAPI (Coleman 1980) had been added. Entire chambers were examined at 150X using an epifluorescence microscope and a combination of tungsten and UV light. Microplankton (predominantly organisms 20-200 micrometers but sometimes larger) with a stained nucleus were counted and measured. Biomass was estimated by converting cell volumes to carbon using conversion factors for the various groups as described by Gowing et al. (2003).

References:
Coleman, A.W. 1980. Enhances staining of bacteria in natural environments by fluorochrome staining of DNA. Limnol. Oceanogr. 25:948-951.

Dodson, A.N., W.H. Thomas. 1978. Reverse filtration. In: Sournia, A. (ed), Phytoplankton Manual. UNESCO, Paris, pp. 104-122.

Gowing, M.M., D.L. Garrison, K.F. Wishner, C. Gelfman. 2003. Mesopelagic microplankton of the Arabian Sea. Deep-Sea Res. I. 50:1205-1234.