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Preliminary report of Cruise no 231
15
12
11
10
9
14
13
8
7
MR-LR Stations
Biodiversity stations
Additional Stations
90
Fishing Stations
91 92 93
LONGITUDE (°E)
6
89 94 95 96
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Preliminary report of Cruise no 231
The main objectives of the Cruise 231 are to investigate environment & productivity, plankton diversity, survey of marine mammals, marine benthos and demersal fishery. The FORV Sagar Sampada left Chennai on 23 rd January 2005 at 17:
00 hrs. Sampling started from the first station (13° 50’ N & 90°0’E) on 26 th January
8:55 hrs. We have completed 18 MR_LR stations, 16 Biodiversity stations, 10 additional onboard coastal stations, 18 boat cruise stations and 2 fishing stations. The additional stations include those near to Digilipur, Rangath, Barren Island and
Indira Point. To study the near shore species diversity of plankton, samples were collected from 30, 20-and10m-depth contours off Digilipur and 2 inter island observation stations. After the successful completion of the stations on 13 th Feb. 2005 at 10.00hrs. We reached at Chennai on 16 th Feb. 2005 at 09.00hrs.
(National Institute of Oceanography, Regional Centre Kochi)
Physical Oceanography
Muraleedharan.K.R.
During the Cruise 231, CTD was operated at all stations and processed all the dat files with a bin average of 1m depths. The wind speed and direction were measured by using Anemometer and humidity by Psychrometer. Surface meteorological parameters including SST were measured manually and compared it with the data from automated Integrated Data Acquisition Software (IDAS). Visual identification and estimation of clouds were observed in daytime. The salinity values from the
CTD were corrected against the values from the ship borne Autosal.
Salient features observed onboard
 The primary analysis based on the onboard observations in the Andaman waters showed atmospheric forcing and significant features of north east monsoon.
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Preliminary report of Cruise no 231
 Northern transect profiles showed inversion of temperature (  3°C) up to 60 m depth. The intensity and depth of inversion decreases towards southern transects and it was only up to10°N.
 High SST for the season was observed (29.1°C) at southern transects, while it was low (27°C) in northern transects.
 Winds were north northeasterly in nature with high magnitude (7m/s) at west and low magnitude (2m/s) at east of Andaman Islands.
 MLD profiles showed high values (60m) in open ocean regions and it shallows (7m) towards the coastal regions.
 Sea surface salinity and density contours showed a comparatively high saline, dense waters at western and low saline, low dense waters at eastern region of
Andaman Islands. This condition is attributed to the existence of Bay of
Bengal water in western side and fresh water influx in the eastern side respectively.
 Even though visual observations showed fumes at the top of island, there were no noticeable changes in distribution of temperature and salinity profiles up to 1800m depth.
Chemical Oceanography
Rejo Mon George, Josia Jacob & Lalu Raj, C. M.
Water sampling from standard depths was done using CTD rosette sampler fitted with 1.8 litres Niskin bottles. Samples for dissolved oxygen were immediately fixed with Winkler A and Winkler B reagents and subsequently analyzed onboard using standard sodium thiosulfate solution (Dosimat). pH was estimated using PHM
84 Meter after calibrating using buffer standards of pH 7 and 9. Nutrients (nitrate, phosphate, silicate and nitrite) were analyzed by Segmented flow Auto analyzer
(SKALAR) onboard after calibration using appropriate standards and standard procedures.
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Preliminary report of Cruise no 231
Salient features
 Along the open ocean stations highly saturated dissolved oxygen concentrations (205-220µM) were found along the surface waters of the
Andaman Sea. A thin layer of oxygen minimum zone (~20µM) were observed in the intermediate waters (150-500m) along the stations west of the islands, when compared to the stations east of the islands in the northern transects
(north of 10°N). In comparison to the northern transects, the oxygen minimum zone was not so prominent in the southern transects.
 High nutrient concentrations (NO
3
~1.1µM and SiO
4
~5.3 µM) were observed along the stations west of the 13.8°N transect which may be due to the influence of BOB waters.
 Surface dissolved oxygen concentration was found to be high along the western coastal stations (225µM) when compared to the eastern coastal stations (210µM).
 Nutrient levels were found to be high along the coastal stations east of the islands (NO
3
~0.07-0.36µM and SiO
4
~3.85-5.5µM) when compared to the stations in the west (NO
3
~0.02-0.15µM and SiO
4
~3.5-4.4µM).
 Along the near shore stations, the dissolved oxygen concentrations were found to be higher along the Wandoor area (215-230µM) when compared to the North Bay and Diglipur (~210µM). Nitrate concentrations in the surface waters were found to be higher in the Jolly boys, Viper Island, North Bay and
Ross Island areas (1.5-2.0 µM).
Biological Oceanography a) Planktonology
Prabhakaran, M.P., Biju, A. and Honey U.K. Pillai.
Water samples for quantitative and qualitative analysis of phytoplankton and particulate organic carbon (POC) were collected from seven standard depths, and kept for analysis at shore laboratory.
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Preliminary report of Cruise no 231
Bongo Net and Multiple Plankton Net (MPN) were used for collecting zooplankton samples. Salient features observed concerned with zooplankton during the study period were given below.
1.
The zooplankton biomass distribution showed a decreasing trend from mixed layer to the deeper depth strata.
2.
Mixed layer supported 58.77% and thermocline layer, 26.39% of zooplankton biomass. During previous winter season, it was 58% and 18.7 % respectively.
3.
Highest biomass of 664.71% ml/1000 m 3 was recorded at 8° 00’N and 93° 00’
E, (west of Campbell Bay) and lowest, 100ml/1000m 3 at 13° 50’N and 93° 00’E.
4.
Average zooplankton biomass in the mixed layer, was higher (313.07 ml/1000m3), during night when compared to the daytime collections (210.67 ml/1000m 3 ).
5.
Western side of Andaman waters has more zooplankton biomass (506.8 ml/1000m3), than eastern side (414.1ml/1000m 3 ).
6.
Latitudinally, highest zooplankton biomass was observed in the southern transects (514.56 ml/1000m 3 ) while it was 417.56 ml/1000m3 in the northern transects.
7.
Myctophid fishes and bioluminescent copepods were common in almost all stations.
8.
Numerous Porpita were obtained from northern most transect (13° 50’N) and not observed from other transects.
9.
More fish larvae were obtained from station 1627 (8° 00’N and 93° 00’E).
Zooplankton was comparatively high in all depth strata at 10° 00’N and 91°
00’E. b) Biodiversity of Plankton
Cruise 231 covered all the predecided 16 stations and additional stations for the biodiversity study of plankton of Andaman waters. In addition to this, 18 near shore collections were made by conducting a boat cruise. Zooplankton and phytoplankton samples were collected for the detailed biodiversity studies.
Salient features of observations
 Phytoplankton bloom was observed at Viper Island and Minnie Bay, where nitrate conc. of 1.86 µmol was observed.
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Preliminary report of Cruise no 231
 Highest biomass with high amount of Salps (7500ml/1000m 3 ) was observed in coastal station # 1621 (BD7).
 Highest biomass with out jelly fish (2727.27ml/1000m 3 ) was observed in coastal station # 1632.
 Swarms of large medusae observed in coastal station #1637 (BD
14
).
 Abundance of chaetognaths and bioluminant copepods were observed.
Survey of marine mammals
Dr. P. Kannan
CMFRI, Mandapam Regional Centre
On board observations on marine mammals were carried out during the cruise 231 of FORV Sagar Sampada on the eastern and western sides of the Andaman and Nicobar Islands. The area located between lat. 6 0 and 13 0 N and long. 90 0 and 94 0 E.
Visual observations on marine mammals were made from 23 rd January to 15 th
February 2005 during day daylight hours (0600-17.30 hrs). A binocular Vanguard
BR.7500, 7X50 mm field: 7.1 was used during the survey, photographs were taken of animals whenever possible by using Yashica MF-2 Super, Yashica lens 38 mm 1:3.8.
The reliability of the identification of sightings, is indicated as follows (1) unidentified whale or dolphins denote a sightings were a name could not be reliably assigned due to long distance, poor visibility and fast moving nature of dolphins (2) presence of name denotes a sightings were there was a full confidence in the identification. Field identification was aided by a reference book Sea Guide to Whales
of the World by Lyall Watson (1981).
Observations
A total of 21 sightings representing 4 species of cetaceans were recorded during the cruise period that included 18 sightings (3 species) in Andaman waters.
The survey area was divided in to five geographical sections that included north, middle, south and little Andaman, and Nicobar Islands in the southern part of Bay of Bengal of the Indian Ocean and covered 1768 nautical miles. Cetaceans were sighted mostly during morning and evening hours (Fig.1)
Fig. 1. Sightings of cetaceans during day light hours in Andaman waters
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Preliminary report of Cruise no 231
16-17.30
38%
6-8.30
33%
6-8.30
9-12.30
14-15.30
16-17.30
14-15.30
5%
9-12.30
24%
Sighting of Cetaceans
North Andaman (Lat. 13 0 34.00 N and 12 0 52.00 N and Long. 93 0 00.15 E)
The coastal and offshore areas of north Andaman were surveyed during the cruise. A total of 6 sightings that included 1 sighting of sperm whale Physeter
macrocephalus, 3 sightings of bottle nose dolphins Tursiops sp. and 2 sightings of unidentified dolphins were recorded.
Middle Andaman (Lat. 12 0 52.00 N and Long. 93 0 00. 00 E)
No sightings in the middle Andaman regions.
South Andaman (Lat. 12 0 16 .00 N- 11 0 26 .00 N and Long. 93 0 00. 00 E)
There were 10 sightings in which dolphins could not be identified in 8 occasions. These sightings involved 1 to 25 dolphins occurred in the offshore and near shore areas of Port Blair. Sighted bottlenose dolphins Tursiops sp. and a pod of sperm whale P. macrocephalus at off Barren Island that included 8 individuals of large to medium sized whales found in 4 groups containing 2 animals each in a single group found scattered in one kilometer radius. They were on the surface emitted blow often and stayed in the surface for more than 5 minutes and finally took dive.
These whales were identified as sperm whale by their long blunt head appeared above the surface and produced spouts often, the spouts shoots up to 2-3 m height at forward angle. All whales are black in color.
Little Andaman (Lat. 10 0 18 .00 N and Long. 93 0 00. 00 E)
A group of spinner dolphin Stenella longirostris was sighted at the above position in ten degrees channel followed by > 7 unidentified dolphins at Lat. 08 0 29
.00 N and Long. 92 0 42. 89 E.
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Preliminary report of Cruise no 231
Nicobar Islands (Lat. 10 0 00..00 N - 06 0 44..00 N and Long. 93 0 00. 00 E)
The offshore and inshore areas of Car Nicobar, Katchall, Little Nicobar, Great
Nicobar and Indira point areas were surveyed during the cruise but no marine mammals were sighted from these regions.
Cetacean’s sightings were higher in South Andaman 10 (48%) followed by north and Little Andaman waters respectively 6 (28.5%) and 2 (9.5%). There were 3
(14.2%) of sightings in Bay of Bengal waters on the east coast of India. Cetaceans were not sighted anywhere in the Nicobar group of Islands.
Observations on Benthic Biota
V. S. Sharma. SRF
&
Y. K. V. Rao. JRF
Andhra University
Benthic sampling was carried out at a few selected stations in the shallower regions of east and west coast of Andaman Islands. Benthic macro fauna was collected by means of Van Veen grab (0.2 m 2 ). As soon as the grab sample was hauled, it was washed gently with seawater through a sieve (0.5 mm mesh size). The samples were then fixed in 7% formaldehyde in Bengal Rose for later sorting.
Sediment samples were collected from grab, weighed for moisture content, kept in the hot air oven for drying to analyse organic matter and granulometry.
A corer of 2.4 cm diameter was employed for collecting the meiobenthic samples. A core sample of 5 cm height was narcotized in saturated magnesium chloride and preserved with 4% formaldehyde in Bengal Rose for further analysis.
A naturalist’s dredge (75×30cm) was employed for sampling the epifauna.
The net had an eye diameter of 1 mm and an open-ended sleeve tied at the bottom with a cod end knot. On the deck the sample was emptied into a polythene trough, washed thoroughly with seawater. The samples were fixed with 7% formaldehyde for further analysis.
Stations and remarks
S.No. St. No. Depth (m)
1.
2.
4
8
50
117
Operation proposed
Grab
Grab
No sample (Coral sand bed)
No sample.
Remarks
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Preliminary report of Cruise no 231
3.
8A
4.
9
150
200
Grab/ Dredge Full sample/ No sample
Grab 20% sample (Muddy & Rocky)
5.
6.
7.
9A
16
17
250
300
119
Grab/ Dredge Full Grab/ No sample
Grab 70% sample
Grab/ Dredge Full / No sample
8.
17A 106 /100 Grab/ Dredge Full / successful sampling
9.
10.
23
34
11.
34A
12.
13.
40
41
220
117
57
120
100
Grab No sample
Grab/ Dredge Full / No sample
Grab Full sample
Grab/ Dredge Full / Only empty shells
Grab Full sample
In total 6 Dredge attempts were made, out of which 1 attempt was successful.
Due to the unevenness of the bottom topography Dredge was a failure. In the northeast region, due to the presence of corals, most of the grab attempts were failed.
List of Benthic forms observed in the fish trawl
S. No. Phylum Common names
1
2
Porifera
Cnidaria
Sponges - 5sp.
Sea Anemone - 2sp.
Anthozoans - 1sp.
3 Nematyhelmenths Hirudinaria - 1sp.
4 Arthropods
5 Molluscs
6 Echinoderms
7 Pisces
Crabs - 4sp.
Lobsters - 2sp.
Shrimps - 3sp.
Squilla - 1sp.
Lepas - 1sp.
Barnacles - 1sp.
Squids - 1sp.
Chiton - 1sp.
Natiluca - 1sp.
Nudibranch - 1sp.
Octopus - 1sp.
Pecten - 1sp.
Star fish - 4sp.
Brittle stars - 1 sp.
Holothurians - 1 sp.
Rays - 1sp.
Flat fishes - 1sp.
Sholes - 1sp.
Others
+ Present, - Absent, ** Very high numbers
+
+
+
+
+
+
+
+
-
Northeast
Andaman
+**
+
+
+
+**
+**
+
+
+
+
+
+
+
+
Southwest
Andaman
+
+
-
-
+
+**
+
+**
+
-
-
-
+**
-
+**
-
+
-
-
+
+
-
+**
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Preliminary report of Cruise no 231
It was observed that the benthic fauna showed variations in the two locations.
Northeast region was rich in terms of species diversity with very high numbers of sponges, gorgonids, spider crabs and lobsters, whereas the southwest region was rich in terms of abundance with very high numbers of Natiluca sp. (Gastropod) and fish sp. The high diversity may be attributable to the sediment nature of the trawled areas with high sandy silt natured sediment in the northeast region and silty-clay in the southwest region.
Demersal Fishery
Department of Ocean Development & National Institute of Oceanography
Bottom topographical studies have been conducted in the north east (off
Diglipur and Mayabunder) and south west of Andaman by using EK 60 Echo sounder (38 KHz). In the north east region fishing ground was located in between 13
04 N to 13 11’ N and 93 07’E to 93 09’E with a depth range of 313 to 323m and in the south west region it was 11 13.4’N to 11 17.3’N and 92 21.3’E to 92 24.9’E with a depth range of 232 to 270m.
In the northeast region average catch obtained was 125 kg while in the south was it was 300 kg. From the preliminary observations it was found that species diversity was higher in the southwest region.
Catch composition in north east region
1.
Deep sea lobster
2.
Deep sea non penaeid prawns
3.
Deep sea black rays (Rajiformes)
4.
Chlorophthalmus sp.
5.
Lizard fish
6.
Deep sea shark (Chiloscyllium indicum)
7.
Nemipterus sp.
8.
Puffer fish
9.
Flat fish
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Preliminary report of Cruise no 231
10.
Hawk fishes
11.
Peristiidae
12.
Crabs
13.
Octopus
14.
Squids
The most dominant forms were Priacanthus sp. Saurida sp. Pomatomus sp. and
Neoscopulus sp. In addition to the species seen in the northeast region as mentioned above one species of deep sea lobster, two species of prawns, two species of shark, ribbon fishes, eel, more number of squids, etc., were found in the southwest region.
Compared to the previous fish catch data (1500 kg) during the year the present catch showed a decrease (300 kg), in the south west region while in the north east region the catch was more (9 kg in 2002 & 125 kg in 2005).
Remarks
Both earthquake and the tsunami have affected the coastal regions of southern Andaman and Nicobar Islands. It has been reported that severe damage has been inflicted on the ecosystems such as beaches, coral reefs and other coastal habitats. In the northeastern region, the coastal area is not much affected as evidenced by the status of corals in the near shore waters. Corals, gorgonids and coral reef associated fauna are alive and in good condition in this region, which indicates the stability of the bottom. Even though the surface salinity and temperature didn’t show much variation in the middle Andaman, coral and associated fauna were heavily damaged in the Wandoor and Jolly boys region. This may be due to heavy force and beach erosion by Tsunami waves. Comparatively high values of nutrients concomitted with the high dissolved oxygen promote the phytoplankton production (Presence of bloom) in the near shore waters of Vyper
Island and Minnie Bay, where the intensity of Tsunami waves were high.
A part of the beach is either submerged or eroded due to earthquake and tsunami. In the fishing ground of northeast region, benthic organisms including sponges, gorgonids, echinoderms, etc. were alive and abundant while in the southern region it was very less but have large number of Nautilus of various sizes.
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Preliminary report of Cruise no 231
During the study it was noted that the areas having thick mangrove vegetation are least affected. In such areas beach erosion is very much reduced. This may be due to the reduction of intensity of waves by mangrove vegetation.
Dr.C.B.LalithambikaDevi
Chennai
17-02-05.
Chief Scientist
Cruise no. 231
FORV Sagar Sampada Cruise no 231
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