The ecology and distribution of alcyonaceans at Mandapam (Palk Bay, Gulf of Mannar), South India

4 Pages·1997·2.7 MB·

by  V Jayasree

THE ECOLOGY AND DISTRIBUTION OF ALCYONACEANS AT MANDAPAM
(PALK BAY, GULF OF MANNAR), SOUTH INDIA1
V. Jayasree and A.H. Parulekar2
(With one text-figure)
Key words: Alcyonacea, distribution, Mandapam, GulfofMannar
New distribution records for 27 species ofAlcyonaceans are given. These include major
genera Sinularia (12 spp.), Lobophytum (7 spp.), Sarcophyton (6 spp.), Dampia (1 sp.)
and Nephthya (1 sp.). The factors that influence the distribution of corals, such as
temperature, sedimentation and currents on this reef are discussed.
Introduction diving under the D.O.D. National Project on
“Development ofPotential Drugs from the Sea.”
Mostly the coral reefs offringing type are Some environmental and hydrological para-
found in the Palk Bay and Gulf of Mannar on meters such as temperature and salinity were
the southeastern coast ofIndia. These arechiefly recorded.
located aroundvarious islands betweenTuticorin All the specimens reported are preserved
andRameswaraminthe GulfofMannar andPalk in 70% methanol and deposited in the Marine
Bay at Mandapam. The reeflies between 79° 27' Biology Museum and Taxonomy Reference
40” to 79° 8' E long, and 9° 17' N lat. (Fig. 1). Centre at theNational Institute ofOceanography,
The Palk Bay is a shallow basin with an average Goa.
depth of 9 m, with mainly muddy bottom at
inshore regions and depth ranges from 1 to 5 m. Results
In spite of some investigations of South Indian
coral reefs (Foote, 1889; Walther, 1891; Major environmental and hydrological
Thurston, 1895; Sewell, 1935; Pillai, 1969, 1971) conditions show thatthe study area receivesboth
our knowledge, particularly ofOctocoral fauna, the southwest and northeast monsoons. Rain is
is scanty. The only literature available on this moderate to heavy during October to mid-
part ofthe Indian Oceanis Hickson (1906), Pratt December, with occasional gales. The average
(1906), Thomson and Henderson (1906), atmospheric temperature varies from 25°C to
Thomson and Simpson (1909). 31°C with maximum and minimum in May and
January respectively.
Material and Methods The surface temperature of the waters of
Palk Bayvaries from 24.6°C to 29. 1°C, with the
Alcyonacean coral material was studied lowest and highest in January and April
from collection made by N.I.O, Goa, Andhra respectively. The salinity is low during January,
University, Waltair and I.I.C.T. Hyderabad gradually rising to the maximum in November,
during May 1993 to February 1994 by SCUBA followedbya declineinDecember. Itvaries from
33 to 36 ppt. The tidal range is usually within
Accepted February, 1996 anamplitude ofone metre. The Palk Bayremains
2National Institute ofOceanography, Dona Paula,
Goa 403 004, India. calm during most months except at the onset of
522 JOURNAL, BOMBAYNATURALHIST. SOCIETY, Vol. 94 (1997)
the northeast monsoon, when turbulent numerous alcyoniids in shallow water. It is also
conditions prevail. No fresh water inflow dilutes reported that a marked difference in the species
the sea near Mandapam. diversity is found in deeper areas (Benayahu,
The study material comprises 27 species 1985). This survey also reveals the presence of
which are listed in Table 1. Most of them are nephtheids and patchy assemblages of
new geographical records for this part of the Sinularia brassica and S. abrupta, confirming
Indian Ocean earlier findings. The rare occurrence of these
The most abundant and dominating species could be due to their low repro-
genera in the study area are Sinularia dessecta ductive potential and short-distance dispersal
and S. leptoclados. The species Sinularia of planulae. Another major factor which
leptoclados is well known from numerous influences alcyonacean distribution could be the
Indo-Pacific sites (Verseveldt, 1980). The most availability of a firm substrate suitable for
common Lobophytum spp. are Lobo- the settlement of planulae. Depth distribution
phytum crassum and L. pauciflorum. Sinularia and zonation of different species is determined
manaarensis in Krusadai Island confirms by biotic and abiotic factors (Dineson, 1983).
its exclusive occurrence (Verseveldt, 1980). In The present survey also indicates a particular
the genus Sarcophyton, Sarcophyton elegansand species of soft coral which forms colonies in
S. trocheliophorum were the most frequent soft different reefs. Also, the frequent occurrence
corals. of a particular species in these areas suggests
The reefs in the Gulf of Mannar are the resistance to wave action, temperature and
most diverse in soft corals compared with other salinity variations, tidal influence and
parts of the Indian Ocean (Pillai, 1971). The sedimentation. These reefs also provide good
present study shows the accumulation of light penetration and tidal currents which
ECOLOGYANDDISTRIBUTIONOFALCYONACEANSATMANDAPAM 523
Table
1
SPECIES AFFILIATION OF ALCYONACEANS IN GULF OF MANNAR
PLACE DATE DEPTH TAXONOMIC AVAILABILITY
IDENTIFICATION
m
OffKrusadai Island 25.06.93 2 Lobophytum sarcophytoides Frequent
m
Vadakadu 20.06.93 3 Sarcophyton trocheliophorum Frequent
Rameswaram
m
Vadakadu 20.06.93 2 Sarcophyton crassocaule Frequent
Rameswaram
m
OffManauli Island 23.07.93 2 Sinularia dissecta Frequent
m
OffPulli Island 23.06.93 2 Sinularia polydactyla Frequent
m
OffPulli Island 23.06.93 2 Sinularia abrupta Frequent
m
Moyli Island 24.06.93 2 Sinularia leptoclados Frequent
m
Moyli Island 24.06.93 2 Sinularia hirta Frequent
m
Krusadai Island 25.06.93 1 Sinularia dissecta Frequent
m
Krusadai Island 25.06.93 1 Sinularia manaarensis Frequent
m
Krusadai Island 25.06.93 2 Lobophytumpauciflorum Frequent
m
Krusadai Island 24.01.94 3 Lobophytum crassum Abundant
m
Mandapam 27.01.94 3 Sarcophyton cherbonneri Frequent
m
Krusadai Island 27.01.94 3 Sarcophyton elegans Frequent
m
Mandapam 27.01.94 3 Sinularia exilis Frequent
m
Mandapam 27.01.94 3 Sarcophyton stellatum Frequent
m
Mandapam 26.01.94 3 Sinularia intacta Frequent
m
Mandapam 26.01.94 3 Lobophytum ransoni Frequent
Mandapam 26.03.94 3 m Sinularia grandilobata Frequent
Tuticorin 03.01.94 Deep sea Sinularia brassica Abundant
Tuticorin 04.01.94 Deep sea Sinularia abrupta Rare
Tuticorin 04.01.94 Deep sea Dampia poecilliformes Rare
Tuticorin 05.01.93 Intertidal Lobophytum compactum Rare
m
Mandapam 27.01.93 3 Lobophytum variatum Frequent
m
Krusadai Island 27.01.93 3 Lobophytum latilobatum Frequent
—
m
Krusadai Island 3 Sarcophytonglaucum Abundant
m
Mandapam 26.01.94 3 Sinulariagranosa Frequent
m
OffMandapam Island 23.06.93 2 Sinulariagranosa Frequent
m
OffMandapam Island 23-06.93 2 Sinularia erecta Frequent
m
Tuticorin 14.02.93 2 Nepthya sp. Rare
, 1
524 JOURNAL, BOMBAYNATURAL HIST. SOCIETY, Vol. 94 (1997)
enrich the water with plankton (Klenker et al Acknowledgements
.
1976). The frequency of appearance of soft
corals could be based on differences in life We are thankful to the present and former
history or reproductive nature. Also, it is Directors of this Institute for extending all
suggested for the soft coral genera of facilities. Wegratefully acknowledgeProfA.S.R.
family Xeniidae, that the successful inhabi- Anjaneyulu, Andhra University, Waltair, Dr.
tance in Red Sea is achieved by asexual Venkateswarlu, Indian Institute of Chemical
reproduction and high fecundity (Benayahu and Technology, Hyderabad for sending soft coral
Loya, 1984b). collections to us.
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