World Congress of Malacology Antwerp ... - Unitas Malacologica

Application of marine mollusk remains from shell middens for paleoenvironmental
reconstructions
Antipushina, Zhanna
A.N. Severtsov Institute of Ecology and Evolution RAS, Leninsky Prt., 33, Moscow, Russia,
Email: zhannaipee@mail.ru
Mollusc remains from two shell middens on Adak Island, Aleutians were analysed to reconstruct the
paleoenvironmental conditions in this area.
Radiocarbon analysis showed that the first shell midden was formed 6500-6100 years ago. This
deposit is situated near Clam lagoon. Analysis of invertebrates’ taxonomic structure showed that
seabed relief in Clam lagoon changed significantly during the existence of the ancient settlement. It is
manifested in decrease of share of epifaunal molluscs’ remains (foolish mussel Mytilus trossulus and
chitons) from layer 4 to layer 2 of shell midden. Also it is manifested in increase of share of Nuttall’s
cockle’s remains (Clinocardium nuttallii) and other species, which live in sand ground, in the same
layers. It is likely that the intertidal zone of Clam lagoon had more rocky structure at the end of 6 th
millennium BC. Then the portion of rock seabed decreased, and the sandy ground began to dominate.
The second shell midden, situated near Sweeper Cove, was formed 1800-750 years ago. The remains
of epifaunal molluscs dominating in deposit are the evidence of rocky structure of the intertidal zone
of Sweeper Cove during the 8 th -19 th centuries AD. Analysis of the invertebrates’ taxonomic structure
allows to mark out three periods in the development of this shell midden. Conceivably warmer
conditions were from the middle of the 11 th till the 15 th centuries and from the middle of the 16 th till
the 19 th centuries, because thermophilous species, non typical for this region, (Nucella heyseana)
were found in the layers. It is likely that higher production of intertidal community from the 15 th till
the middle of the 16 th centuries is result of relatively cold environmental conditions in this time. The
colder period correspondents to “Little Ice Age”.
Our research was supported RFBR (grant 06-04-48531) and National Science Foundation (grant
OPP-0353065).
Ecology and population dynamics of Tridacna maxima in Lakshadweep Archipelago, India
Apte, Deepak 1 ; Idrees, Babu 2
Bombay Natural History Society, Hornbill House, S.B. Singh Road, Mumbai 400
023, India,
Email: bnhs_conservation@vsnl.net; idrulak@yahoo.co.in
The ecology and population dynamics of Tridacna maxima were studied in Lakshadweep
Archipelago, India. A comparison of T. maxima population was carried out in 10 lagoons covering 24
islands. Various aspects related to ecology and population of T. maxima such as microhabitat,
associate, substrate preference, reef canopy distribution, mortality (predation, diseases, bleaching
etc), recruitment were studied in 10 lagoons.
Agatti Island has the highest population of T. maxima. Porites lutea and Porites solida are most
important species which offer suitable substrate for T. maxima in all islands. Role of herbivore in
maintenance of micro-habitat of T. maxima was studies in Kavaratti Island. Convict Surgeonfish
(Acanthurus triostegus) is the most important browser within the lagoon which is responsible in
maintenance of P. lutea and P. solida coral tops.
The trends clearly indicate high mortality in T. maxima on all islands while recruitment is very low.
Suheli and Bangaram group of islands have shown good recruitment. Bleaching of T. maxima has
been noticed on few occasions. However, habitat degradation due to human induced alteration in
lagoon ecology is the main cause for mortality in T. maxima in many islands. In few lagoons like
Kalpeni, Bangaram and Bitra, large size T. maxima has been observed (480-500 mm). The size
exceeds all the known size records for the species.
10