Foraminiferal Analysis Around the Beach of Mumbai Coast

 ACKNOWLEDGEMENT

                The successful completion of my thesis requires a combined effort of several people. I would like to thank all those people who have been directly or indirectly involved with me during my research work.

Firstly I am grateful to Dr. Hrishikesh Samant, the Head of the Geology Department, St. Xavier’s College, Autonomous, for being kind enough to permit me to use the laboratory. I would like to thank my guide Dr. Pravin Jude Henriques. His thought provoking discussions have enabled me to complete this thesis and for instilling in me the importance of hard work. Special thanks to Prof. Vikram Pratap Singh, who provided me with some useful insights and for showing unending enthusiasm during the work that has taught me to aim higher in life.

                I would like to express my sense of gratitude to Dr. Rajeev Saraswat, Scientist C at National Institute of Oceanography (NIO) for granting me permission to use the laboratory at NIO for my analysis. I am extremely thankful for my collegues, Delora Pereira, Plancy Pereira and Tanvi Mungekar for helping me in my research work and encouraged me to work at a faster pace.

                 I owe my deepest gratitude to my parents, my brother and sister for their love and faith in me. It is only with their motivation and blessings that has enabled me to successfully complete this work. I am extremely grateful to my best friend Claire for being there for me whenever I needed her.

ABSTRACT

        Two surface sediment samples collected near the shoreline from the beaches of Versova and Gorai were studied for their foraminiferal content. The study reveals twelve foraminiferal genuses of which eleven are benthic and one is planktic. The distribution of foraminifera in both the beaches are compared and with the help of salinity data it is interpreted.

CHAPTER 1: INTRODUCTION

1.1 General Description:

        Foraminifera are exclusively marine organisms. Foraminfera are unicellular amoeboid protists. They are unicellular organisms. Fully grown individuals range in size from about 100 𝜇m to almost 20 cm long (Foraminifera: Introduction).  The cell of a foraminfer is bounded by a membrane. Its shell is also known as a test and it consists of one or more than one chambers. A wall termed as septum divides one chamber from another. Protoplasm is continuous between the chambers through a hole in the septum called the foramen (Boersma & Haq, 1998). The protoplasm extends outside the test through the aperture in a mass of branching, anastomosing pseudopodia.

        Foraminifera are divided into two major groups: (a) Planktonics and (b) Benthonics.

[pic 1]

                                 Fig 1. Classification of foraminifera

The Benthic Foraminifera live on the sea bed and have existed since the Cambrian time while the Planktic Foraminifera float freely in the open ocean and are present since the Mesozoic. Jahn and Rinaldi (1959) observed that the pseudopodia consists of thin fragments of a gel-like substance bent back on themselves, similar to a conveyor belt (Boersma & Haq, 1998). Pseudopodia then moves the particles in and out of the inner protoplasm like a conveyor belt. This motion is termed as streaming and is the most characteristic feature of foraminiferal protoplasm. In culture foraminifera feed several times a day, generally at the last chamber (Boersma & Haq, 1998). In some planktic forms, ingestion occurs outside the test whereas in benthic Miliolidae food is drawn directly into the test. Foraminifera live in symbiosis with algae where algae provide nutrition to the foraminifera and in turn shelter is provided by the foraminifera.

        Benthic Foraminifera may be sessile or vagile. Movement on ocean bottom or any substrate is done by means of the pseudopodia. They inhibit all marine environments ranging from the intertidal zone to the deep ocean. Three main morphological characters for classifying foraminifera are:

1. The wall structure of the test.

The basic types of wall structures are:

1. Agglutinated: The test is made up of particles cemented together onto a layer of an organic compound, tectin.
2. Calcareous hyaline: Calcareous walls may be composed of either low- or high-Mg calcite (Boersma & Haq, 1998) When the c-axis of calcite or aragonite are arranged normal to the test surface, the type of wall structure is called radial hyaline whereas if they are arranged randomly then they are termed as granular hyaline.
3. Porcellaineous: The wall is made of randomly arranged microscopic rods of calcite, with inner and outer surface layers (Foraminifera: More on Morphology).

Planktonic foraminifera belong to the calcareous hyaline type whereas benthic foraminifera belong to the porcellaineous type.

1. The number of chambers.

Foraminifera can be monothalamous or polythalamous. Monothalamous means one chambers whereas polythalamous means more than one chambers. The initial chamber is often spherical or oblate with an aperture while the later chambers range in shape from tubular, spherical, to ovate (Boersma & Haq, 1998).

1. The test morphology.

This includes the mode of coiling, chamber arrangement and apertural system.

The different modes of coiling shown by foraminifera are:

1. Planispiral coiling: The chambers are arranged spirally about an axis of coiling and lie in a single plane.
2. Trochospiral coiling: The spiral does not lie in one plane but progresses up the coiling axis.
3. Streptospiral coiling: Trochospiral coiling taking place in several planes of coiling.

When a series of chambers is coiled about an axis, the chambers involved in one complete revolution are termed as a whorl or coil (Boersma & Haq, 1998).

Evolute coiling is one where the previous whorls are visible whereas involute coiling is one where previous whorls are hidden. The side of the foraminifera showing the trace of the coil is termed as the spiral side. The opposite side is the umbilical side. The umbilicus is the axial space between the inner wall margins of the chambers belonging to the same coil (Boersma & Haq, 1998).