Indian Ocean
Zooplankton
Samples were taken by open-closing JUDAY nets with a 0.36 m ring diameter and mesh sizes of 112 to 120 mkm.
The JOM net (the JUDAY oceanic model), with a mesh size 300 mkm was also used occasionally.
All tows were taken in either a vertical or oblique manner and were hauled at a speed of approximately 0.5 m/s.
The open-closing mechanism used was the Nansen mechanical lock
system allowing nets to be vertically towed through standard depths
(0-10, 10-25, 25-50, 50-100, 100-200, 200-300, 300-500m) and closed
at the upper depth level.
Integrated hauls (0-100, 0-200m) were also taken.
The 10-20 ml samples were preserved in 3-4% buffered formaldehyde and processed on return to the laboratory.
Before processing, the sample was stirred and aliquots of 1 to 5 ml
were taken out of the sample using pipettes.
Organisms were identified and enumerated to the species level under
a binocular microscope (MBS-1 or MBS-3) in Bogorov chambers.
Abundance of males, females, and copepodites for each species and
the total abundance of nauplii were determined.
Two replicates from each sample were processed as a rule and these
replicates were averaged. The large size organisms were counted in
the whole sample.
Individual weight of organisms was calculated from measurements of
body length using the so-called Tables of Standard Weights (Kanaeva,
1962; Shmeleva, 1963; Kryilov, 1968; Gruzov, Alexeeva, 1970) or
nomograms relating the length and a typical body shape with the
weight of animals (Chislenko 1968).
Phytoplankton
Phytoplankton samples were taken by 6 liter water bottle from
different depths of 0 - 100 m layer.
Samples were concentrated by the method of back filtration.
Nucleopore filters of pore size 1.5 mkm were used.
Samples were fixed by Lugol's solution and after sample processing
were preserved by 4% formaldehyde.
In the laboratory samples were concentrated to 2-10 ml volume.
Calculations of phytoplankton cells numbers were made from 0.05 ml
drop using light microscope and then recalculated for 1 liter.
Additionally, sediments of samples were examined in Bogorov's
chambers to count large and rare cells.
Biomasses of phytoplankton algae were calculated using cell volume
by equating real or average volumes of cells to corresponding
geometric figures.
Physical Parameters
The standard hydrological methods were used to produce the
hydrological data:
- Nansen Bottles with deep-sea reversing thermometers;
- CTD-sounding systems.
For salinity determination before 1969 the argenometric titration
from the chlorine was used with salinity calculated from Knudsen's
formula. The finish of reaction was obtained from visual observation
of the indicator color change. Errors of estimation of the chlorine
observations on aboard condition were no more than +-0.015 promille,
and from salinity - no more than 0.025 promille with confidential
probability 0.95.
From 1969 year salinity was determined by means of laboratory
electrical salinity-meter GM-65. Error of estimation of the salinity
in water sample was no more +-0.02 promille with confidential
probability 0.95.
Temperature observation during batometric casts was provided by
means of Deep-sea reversing thermometers - DSRT. Root mean deviation
of the temperature observation was 0.015 degrees. Total temperature
observation error was +-0.04 degrees with confidential probability
0.95.
Depth observation during batometric casts was provided by means of
DSRT. Root mean deviation of the depth observation was 3-5 meters
from 0 to 1000 meters depth and 0.5 percents from over 1000 meters
depth.
CTD-sounding systems were used for temperature, salinity and depth
observations from 0 to 2000 meters depth.
Device types are ISTOK-3, ISTOK-4, and ISTOK-5.
Chemical Parameters
Hydrochemical information of R/V "Mikhail Lomonosov" and R/V "Academik Vernadskiy" of Marine Hydrophysical institute, received in the Indian ocean from 1966 to 1981 (9 cruises), is presented in this data set. Hydrochemical data include information on dissolved oxygen (O2), inorganic phosphates (PO4), silicates (Si), nitrates (NO3), nitrites (NO2), pH values (pH), and total alkalinity
Different methods were used to determine the same hydrochemical
parameter in different cruises and it should be recognized to
analyze and compare information of this general data set correctly.
The next methods were used:
1. Dissolved oxygen was determined by Winkler's method .
2. The method of Denige and Atkins (with SnCl2 as a reducer of
phosphomolibdate complex) was used since 1966 to 1975 (4 cruises) to
determine inorganic phosphates . Since 1979 (5 cruises) the method
of Murphy and Riley (with ascorbic acid as reducer) has been
using.
3. The method of Mullin and Riley (with methol-salphite solution as
reducer of silicomolibdic acid) was used since 1966 to 1980 (7
cruises) . In 22-nd and 24-th cruises of the R/V "Academik
Vernadskiy" (1980 and 1981) modification of above mentioned method
was applied (with ascorbic acid as reducer) .
4. The method of Morris and Riley with reducing of nitrates with
copper-coated cadmium grains in glass burette was used in all
cruises.
5. The method of Griess-Ilosvay was used to determine nitrites .
6. pH value was determined by visual comparison with the Serensen
scale in the 19-th cruise of R/V "Mikchail Lomonosov".
In the other cruises pH-meters "pH-262" and "pH-340" were used to
determine pH value.
7. Total alkalinity was determined by volumetric method of Bruevich
(titration of sample of water with hydrochloric acid and flushing it
with CO2-free air). The end point of titration was controlled
visually.