Annual Report 2009-2010 - Ministry Of Earth Sciences

7.3.2 Black Pearl Spat production and Pearl
farming
The life cycle of Pinctada margaritifera was closed
by achieving spat production in the hatchery
during February 2009. After repeated trials this
success was achieved mainly through the exclusive
use of the diatom Pavlova salina as feed. The other
critical factor was the quality of the seawater. With
the commissioning of the pressure sand filter
and the cartridge filters (10 to 1.0 µ) mortality
was considerably reduced totally to 25000 spat
production in the hatchery.
Pearl Farming
A new wooden raft with surgical implantation
facility was deployed in Panighat in Port Blair. This
raft now holds more than 1500 adult oysters and
hatchery produced spats (Fig. 7.3).
Fig. 7.3: Hatchery produced spat
Fig. 7.4: Pyrophacus steinii 400 x
A mono-specific bloom of dinoflagellate
Pyrophacus steinii (Fig. 7.4) was observed off
Mangalore on 1 st October 2009 without any
discolouration of the surface waters. This was,
to our knowledge, the first record of bloom of
Pyrophacus sp. in the Indian waters.
Chattonella marina bloom with rusty brown
discolouration of the surface water was observed
off Kochi on 23 rd September 2009.
7.4 Harmful Algal Bloom (HAB)
During 2009-10 Harmful Algal Blooms were
recorded from 10 locations in the Indian EEZ,
mainly in the Kerala – Karnataka coast. Extensive
Trichodesmium blooms were encountered off Goa
and Mangalore (April: Sagar Kanya), off Kollam, off
Kochi, off Kannur (June 09) just prior to the onset
of SM upwelling. The occurrence of the nutrient
depleted Arabian Sea High Saline Water (ASHSW) is
expected to be the causative factor for the blooming
of Trichodesmium species. It is well known that
Trichodesmium can fix atmospheric nitrogen
and hence occurrence of Trichodesmium blooms
along the SW coast during pre-monsoon can be an
adaptation to recycle nitrates to the ocean.
Detailed investigations were carried out onboard
FORV Sagar Sampada to study the extensive algal
blooms occurring along the northwest coast of India
during the fag end of winter monsoon and early
spring inter monsoon seasons. The bloom forming
species along the NW coast was identified as the
green Noctiluca (N. scintillans) with its associated
endosymbiont Pedinomonas noctilucae. Blooms
were monitored during the initiation, spreading
and crash stages. Bloom initiation was associated
with deep mixed layer (>100m) which brings the
cysts to the euphotic zone where cell proliferation
occurs in presence of relatively high nutrient load.
During the spreading stage the nitrate levels are
maintained by regenerated production through the
microbial loop and vertically shoaling Rhizosolenia
mats. Towards the end of the crash stage nitrate
levels in the surface waters reach very low values
(0.18 µmol/litre). A theoretical model to explain
the open ocean blooms of the NW coast, is being
refined (Fig. 7.5).
Ministry of Earth Sciences : Annual Report 2009-10 43