Intertidal
Foraminifera of Indian coast - a scanning electron photomicrograph-illustrated
catalogue
G. Subhadra Devi1 & K.P. Rajashekhar 2
1,2Department of
Applied Zoology, Mangalore University, Mangalore, Karnataka 574199, India
Present
Address: 1 Depatrment of Zoology, Carmel
College for Women, Nuvem-Salcete, Goa 403601, India
Email: 2 (Corresponding author) drrkpatil@yahoo.com
Date of online publication 26 January 2009
ISSN 0974-7907 (online) | 0974-7893 (print)
Editor: R. Ramanibai
Manuscript details:
Ms # o1977
Received 08 April 2008
Final received 20 November 2008
Finally accepted 02 December 2008
Citation: Devi, G.S.
& K.P. Rajashekhar (2009). Intertidal Foraminifera of Indian coast - a
scanning electron photomicrograph-illustrated catalogue. Journal of
Threatened Taxa 1(1): 17-36.
Copyright: © G.
Subhadra Devi and K.P. Rajashekhar 2009. Creative Commons Attribution 3.0
Unported License. JoTT allows unrestricted use of this article in any medium
for non-profit purposes, reproduction and distribution by providing adequate
credit to the authors and the source of publication.
Author Details: Dr. G. Subhadra Devi is a Reader at the
Carmel College for Women in Goa, India and teaches Zoology. She is interested in marine biodiversity and
is currently working on foraminifera in the coral reefs of Lakshdweep
archipelago.
Dr. Rajashekhar K. Patil is Professor of Applied Zoology at Mangalore
University, Karnataka, India. He is studying foraminifera of Mangroves to
understand the dynamics of Mangroves and patterns of Monsoons.
Author Contribution: Both
the authors have made equal contributions to the study and the current paper.
Acknowledgement: We
are grateful to Dr. Rajiv Nigam of Geological Oceanography Division, National
Institute of Oceanography, Goa, India, for his valuable suggestions and
support. We express our sincere thanks
to Dr. Shyam Prasad and Mr. Vijay Kedekar, National institute of Oceanography,
Goa, for Scanning Electron Microphotography. The study was supported by FIP
Fellowship by University Grants Commission, New Delhi, to GSD. Grants from
DST-FIST programme are gratefully acknowledged.
Abstract: Foraminifera (forams) are very useful in deducing diverse
environmental parameters such as palaeoclimate, oil deposits, oceanography,
pollution monitoring and palaeomonsoons. Forams are calcareous, shell-secreting
protists and are likely to be adversely affected due to anthropogenic ocean
acidification caused by CO2emission. Considering their significance
and status, we have surveyed the occurrence of intertidal forams along the
Indian Coast and Amini atoll of Lakshdweep Islands. Scanning electron microscopic observations
have been carried out and are presented here. The foram assemblage is distinct
from the tropical sites surveyed elsewhere while some of the species are
common, suggesting that the local oceanographic conditions are major
determinants in distribution of foram species. A total of 151 species of Foraminifera belonging to 65 genera, 41
families and 7 suborders were recorded in the present study. Only 4 species were planktonic and the rest
were benthic. Rotalina and Miliolina were found to be dominant suborders. This paper contains SEM images of 142
identified species and surface details of some of species. The observations will serve the needs of
researchers working with forams, especially in identification and morphological
analysis.
Keyword: Foraminifera, Diversity, Intertidal, Indian Coast, SEM
For Images & Tables – click here
Introduction
The diversity of marine life is being affected dramatically due to many
causes. Increased atmospheric CO2 emission leads to
its increased dissolution in ocean water causing acidification. Such anthropogenic ocean acidification exerts
a great impact on calcifying organisms (Orr et al. 2005). Foraminifera (forams) are one such
shell-secreting group. Among the many
marine taxa that are surveyed for their diversity, there is a bias towards
commercially important organisms and higher vertebrates (Nee 2004). Protists are one of such groups which are
least studied, despite being diverse and abundant. Foraminifera or forams in
short are the most abundant, diverse and widely distributed Protists in the
marine realm. The estimated living species are about 10,000 (Vickerman
1992). Of these, about 40 species are
planktonic and the rest are benthic. Foraminifera are found in all marine
environments (Todo et al. 2005). Diversity of Foraminifera is highest in tropical waters and gradually
declines towards poles (Brasier 1980). The distribution of Foraminifera is not random, but is controlled by
environmental gradient. The factors which influence their distribution and
abundance include bathymetry, sediment texture, and physicochemical
characteristics of sediment as well as water. Therefore, these organisms
provide one of the best sources of proxy oceanic and climatic information.
The calcareous test of forams that protects the single cell incorporates
important physico-chemical properties of the ambient environment during the
life and gets preserved after the death of the organism. The tests are built of hollow chambers
separated by partitions, with small openings called foramina that connect the
chambers. Due to their tests, forams have a good potential to be fossilized. They are the most widely used fossil
organisms for biostratigraphy and age dating. Abundance, species richness, species assemblage, test morphology and
chemical composition of tests of foraminifera have been used to interpret
palaeoenvironmental conditions, such as global sea level variations (Anthony et
al. 2006), palaeomonsoons (Weldeab et al. 2007), palaeodepth (Nigam &
Henriques 1992), palaeotemperature (Zachos et al. 2005), tsunami (Gadi
& Rajashekhar 2007), pollution studies (Debenay et al. 2001). Benthic foraminifera have proved to be good
indicators of methane releases in marine environment (Hill et al. 2003). Scott et al. (2001) have emphasized the
importance of foraminifera in monitoring coastal environment.
The recent reviews of Bhalla et al. (2007) and Khare et al.
(2007) on foraminiferal studies in near shore regions of western and eastern
coasts of India reveal that most of the studies are related to taxonomic and
ecological aspects and palaeoenvironmental interpretations. A few studies have been undertaken along the
eastern coast of India on applied aspects of Foraminifera. Taxonomic and ecological studies on
foraminifera from west coast of India were carried out by some researchers. Bhalla & Nigam (1979) and Bhalla &
Gaur (1987) worked on foram diversity of Calangute and Colva beach sands
respectively. Bhalla & Raghav (1980)
studied the ecology of Foraminifera of Malabar coast and suggested that
salinity is the chief governing factor. Raj & Chamyal (1998) studied the ecology of foraminifera of Mahi
valley of Gujarat. Shareef &
Venkatachalapathi (1988) reported 40 and 41 species of foraminifera from
Bhatkal and Devgad islands, respectively. Nigam (2005) addressed the question
as to how environmental issues can be solved through Foraminifera. Some studies were carried out on taxonomy and
ecology of Forminifera from beaches and estuaries of east coast of India. Foraminiferal diversity in relation to
different ecological conditions was reported by Bhalla (1968) from
Vishakhapatnam beach sands, Hamsa (1973)
and Kathal & Bhalla (1998) from Palk Bay and Gulf of Mannar, Narappa et al.
(1981) from Godavari river system, and Kathal et al. (2000) from Kanyakumari,
and Satyanarayana et al. (2007) from Nagapattinam. Very scanty literature is available on
Foraminifera of Lakshadweep (Gupta 1973; Rao et al. 1987; Saraswati 2007). To utilize these marine protists efficiently,
adequate knowledge of their diversity and distribution pattern in modern
environment is of utmost importance. Therefore, a study of intertidal forams was undertaken comparing the
east and west-coast and the sensitivity of forams to monsoons. This paper presents the scanning electron
photomicrographs of inter tidal forams along the Indian coast, so as to benefit
researchers in diverse areas who use Foraminifera.
Study Area
India has a coastline of 7,517km. The West and East coasts of India exhibit
a number of dissimilarities in terms of oceanography. Bathymetry of the West Coast shows that the
continental shelf is narrow and broadens northwards off the Gujarat coast. The continental shelf of the east coast is
much narrower than the West Coast. The
West Coast is characterised by heavy surf, rocky shores and sandy beaches. The rivers, which originate in the Western
Ghats are short and rapid and westward flowing into Arabian Sea, forming
estuaries rather than deltas. The elevation of the Eastern Ghats is lower than that of
the Western Ghats. Most of the
rivers flow eastwards, form deltas and discharge into the Bay of Bengal. The west coast experiences intense upwelling
during southwest monsoon which brings the nutrients from deeper waters to upper
ocean. The east coast is characterised by a weak upwelling during the northeast
monsoon. Sea surface temperatures of Bay
of Bengal are 1.5 to 2.00C higher than that of Arabian Sea. The salinity of the upper water column is
more in the Arabian Sea than in Bay of Bengal. These dissimilarities are expected to provide variations in ecological
conditions influencing foraminiferal distribution and their diversity. Hence
the following sites of west- and east coasts of were chosen for the present
study.
West Coast of
India
The following 8 sites
of west coast of India were chosen for the present study (Figure 1):
1. Juhu beach,
Mumbai, (W1), is on the west coast of India, in Maharashtra on the
eastern shore of the Arabian Sea. The
location is highly polluted and has considerable organic matter input.
2. Malvan (W2) is
located in Sindhudurg District of Maharashtra. This site is less polluted and is partly a rocky beach.
3. Baga (W3) is a
beach and has large grain sediments and has lesser clay. It is situated along the north Goa coast.
4. Calangute (W4)
beach extends for 7km, stretching along the north Goa coast.
5. Majorda (W5) is a
part of 30km long stretch of uninterrupted beach from Velsao to Cavellossium in
South Goa.
6. Ankola - Belikeri beach (W6) is situated 8km
away from Ankola it is pristine and less impacted by anthropogenic activities.
7. Murudeshwar beach
(W7) is wide and long, dotted with occasional rocks. The gradient of the shore is shallow.
8. Kozhikode - Beypore (W8) beach is located
about 10km south of Kozhikode town at the mouth of the Chaliyar River in North
Kerala. It is a site that is influenced
by estuarine conditions.
9 Amini (W9)is one of
the islands of Lakshadweep Archipelago. The unique feature of the Amini island is that it is encircled by a
lagoon. The depth of the lagoon varies
from 1.0- 2.5m.
10. Kochi - Cherai
beach (W10) is a beach in the Cherai village. The beach has a narrow water way
formed due to Vypeen Island.
11. Kollam (W11) is a
shore with a steep gradient.
12. Shankhumugham
(W12) is close to the southern tip of the peninsula and is a shallow water
sandy beach near Thiruvananathapuram.
East Coast
The following sites
were chosen for the present study (Figure 1):
1. Bali Island is one
of the islands of Sunderbans (E1). The Indian Sundarbans at the apex of the Bay
of Bengal is a deltaic complex of approximately 426,300ha formed by the depositional
activities of the Ganges and the Brahmaputra. A group of 108 islands and a dense network of rivers, canals and creeks
comprise the area. The intertidal zone
of Bali island registers a gradual change in the textural characteristics from
high water level to low level, indicating a sediment change from sandy to silty
and clay nature
2. Digha (E2) is in
Purba Medinipur district of West Bengal. It is located 187km away from Kolkata.
Digha has considerable amount of clay.
3. Paradwip (E3) is
located on the Bay of Bengal and is sandy.
4. Puri (E4) beach is
long and wide extending for miles and is uninterrupted by rocky outcrops.
5. Bheemunipatnam
beach (E5) is about 25km from Vishakhapatnam. This beach is located at the mouth of the river Gosthani in Andhra
Pradesh.
6. Vishakhapatnam -
Ramakrishna beach (E6) is a long stretch of beach with brown sands in Andhra
Pradesh.
7. Chennai - Besant
Nagar beach (E7). Here, the river Adyar
meets the sea. It has impact of a populated city on it and is influenced by
Adyar river discharge.
8. Nagapattinam (E8)
is a long stretch of beach in Tamil Nadu. The width of the continental shelf of the coast near Nagapattinam is
narrow.
9. Rameswaram (E9) is
an island in the Gulf of Mannar at the very tip of the Indian peninsula. The island is spread in an area of 61.8km2.
10. The southernmost
tip of the Rameswaram island is called Dhanushkodi (E10). It is 18km away from Rameshwaram.
The sites studied
thus include locations that are estuarine or influenced by human habitat while
some are pristine.
Methods
Intertidal sediment samples were collected during a period of two years,
from October 2004 to September 2006. Samples were dried at 600C and soaked in
water overnight to remove salts. The sediments were treated with 10% Sodium
hexa-meta-phosphate overnight to dissociate clumped aggregates. To disintegrate the organic matter the samples
were treated with 5ml of hydrogen peroxide. Afterwards, the samples were washed through a 63µm (230 ASTM) sieve
under low water pressure. The sand
fraction was collected and dried at 600C. Finally dried
samples were examined for foram specimens. Individual, intact species were
isolated under Olympus SZ 11 stereomicroscope. Individual specimens were mounted on brass stubs (0.5mm diameter) using
double-sided adhesive carbon tape and coated with gold for about 2 minutes
(SPI-Module Gold Sputter Coater). Specimens were observed using JEOL JSM-5800VS scanning electron
microscope.
To identify live specimens, samples fixed in 70% alcohol were stained
with Rose Bengal (Walton, 1952). The
species were identified and classified by following Loeblich & Tappan
(1987). Recent literature by various
authors was also considered for identification. Diagnostic morphological features of the tests such as shell
ornamentation, chamber arrangement and shape and position of aperture were
considered for identification of species.
Results
A list of Foraminifera recorded in the present study from the
inter-tidal regions of Indian Coast including Amini island of Lakshadweep along
with their taxonomic status is reported in Table 3. Images SEM 1-13 of scanning electron microphotographs
reveal the morphological features of the tests of Foraminifera recorded in the
present study. The study revealed the
occurrence of 151 species of Foraminifera belonging to 65 genera, 41 families
and 7 suborders. All foraminiferal
species belong to the order Foraminifera under Protista. Among the seven
suborders, Rotaliina was represented by maximum number of species 72 belonging
to 36 genera and 21 families. Rotaliinids have calcareous multilocular tests. The suborder Miliolina
was found to be second in species richness with 59 species belonging to 13
genera and 8 families. In this suborder the tests of the foraminiferal species
are porcelaneous. Textularina was
represented by 10 species. They belong
to 9 genera and 7 families. They have
agglutinated tests. Under the suborder
Lagenina 4 species belonging to 2 genera and 2 families were recorded. Tests are monolamellar. Globigerinina was
represented by 4 species of planktonic Foraminifera belonging to 3 genera and 1
family. Tests are calcareous and hyaline
in nature. The suborders Involutinina
and Robertinina were represented by single species, single genus and single
family. Presence of calcareous tests
with tubular second chamber is the characteristic feature of the sub order
Involutinina. Tests are planispirally to
trochospirally enrolled in Robertinina. Out of 151 species, only 4 were planktonic and the remaining were
benthic forms. The number of species
found in each site is provided in Table 2. The occurrence of individual species in each site surveyed is provided
in Table 3. The variations between the
west- and east-coast are due to variations in the physicochemical properties
between Arabian and the Bay of Bengal. A
detailed account of these differences is provided elsewhere (Gadi &
Rajashekhar, Communicated). Clear,
Monsoon related fluxes in diversity do occur in some species.
Conclusion
The assemblage of Foraminifera as observed in the present study reveal
the following important points. The
diversity of foraminifera depends largely on the ecological conditions at a
site. The latitude being the same, they
differ considerably between the West and East coasts of India. The dominant species however are the same,
though their ranking in abundance differs. The relative density and diversity of forams differs between East and West coast. Observations suggest occurrence of
morphogroups. The assemblage differs
considerably from regions studied and reported from elsewhere and it also
differs from other tropical sites where comparable studies have been undertaken
(Javaux & Scott 2003). However, near
shore forams of other regions are comparable to the assemblage found in the
present study. Studies on fossil forams
carried out by Talib & Gaur (2008) in Jumara Dome, Kutch, India revealed 51
species. Comparison of our observations with that of Talib & Gaur (2008)
shows that the present day fauna is considerably different than the fauna of
forams of the Oxfordian age (~160 Myr) and suggests rapid speciation.
We have developed an SEM illustrated catalogue for future reference and
comparison as Arabian Sea has good prospects of natural gas and oil deposits,
for survey of which fossil forams are used. Robust and well defined SW monsoons are also a characteristic climatic
feature that influences Arabian Sea. The SEM images obtained in the present
study will facilitate researchers in proper identification of foraminiferal
species. The surface characteristics revealed will help morphological analysis
from polluted areas and regions affected by high energy waves. The present study gives an overview of the
foram diversity and records the dominant species found along the Indian
coast. Environmental conditions and the
subtleties of variations in oceanography of Arabian Sea and the Bay of Bengal
are reflected in their distribution.
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