SCATOLOGICAL STUDIES OF THE BIVALVIA
(MOLLUSCA)
429
pollution of the bottom under the beds chiefly caused by the bulky
biodeposits of these filter feeding bivalves and other fouling organisms
such as Mytilus and tunicates which compete with oysters for space as
well as for food. Detailed analytical studies on the chemical composition
of the oyster biodeposits by Haven and Morales-Alamo (1966) showed
that these contained approximately 14% of organic matter and 5% of
total organic carbon and that there is no evident seasonal trend. Ito
and Imai (1955) also demonstrated that in the Japanese oyster the biodeposit is composed of 9.1% of humus and O.Syo of total nitrogen. Our
results are similar to those of the above authors and show that the total
nitrogen contained in the biodeposits is approximately l.Oyo (Fig. 29).
Considering the quantities of biodeposits on thc bottom under the beds,
it may be supposed that the bottom sediments will be greatly polluted
by organic matter. As a matter of fact, it has been known among Japanese commercial oyster growers that in many of the oyster beds the oyster
crops decrease with the years, owing to their repeated use. Biodeposits
thus accumulated gradually modify the physical and chemical nature of
the bottom sediments and not only interfere with the lives of the oysters
but also often cause a high mortality during the summer season when
temperatures ara high.
To facilitate explanation of the complex process of biodeposition
involving many groups of animals and physical and chemical factors as
mentioned above, a clear illustration of the biodeposition cycle in the
estuary of the York River was furnished by Haven and MoralesAlamo (1966) (Fig. 30).
VIII. BIBLIOGRAPHY
Abbott, R. T. (1984). “American Seashells.” D. Van Nostrand Co. Inc., New
York.
Abbott, R. T. (1954a). Review of the Atlantic periwinkles, Nodilittorina, Echininus and Tecturius. Proc. U.S. natn. Mus. 103 (3328), 449-4G4.
Allen, J. A. (1962). Preliminary experiments on the feeding and excretion of
bivalves using P32. J . nmr. biol. Ass. U . K . 42, 609-623.
Amstutz, G. C. (1958). Coprolites: A review of the literature and a study of
specimens from Southern Washington. J . sedim. Petrol. 28(4), 498-508.
Arakawa, K. Y. (1960). Some ecological accounts on Scintilla witrea Quoy and
Gaimard. Venus, Tokyo, 21(1), 61-66.
Arakawa, K. Y. (1962). A coprological study on the molluscan faeces (A preliminary note). (In Japanese with summary in English.) Vcnus, Tokyo, 22(2),
151-172.
Arakawa, K. Y. (1963). Notes on the faeces of Macroch.eira kaenipferi de Haan.
Res. Crustacea, 1, 7-8.
Arakawa, K. Y. (1963). Studies on the molluscan faeces (I). Prrbls Set0 mar.
biol. Lab. 11(2), 185-208.
(MOLLUSCA)
429
pollution of the bottom under the beds chiefly caused by the bulky
biodeposits of these filter feeding bivalves and other fouling organisms
such as Mytilus and tunicates which compete with oysters for space as
well as for food. Detailed analytical studies on the chemical composition
of the oyster biodeposits by Haven and Morales-Alamo (1966) showed
that these contained approximately 14% of organic matter and 5% of
total organic carbon and that there is no evident seasonal trend. Ito
and Imai (1955) also demonstrated that in the Japanese oyster the biodeposit is composed of 9.1% of humus and O.Syo of total nitrogen. Our
results are similar to those of the above authors and show that the total
nitrogen contained in the biodeposits is approximately l.Oyo (Fig. 29).
Considering the quantities of biodeposits on thc bottom under the beds,
it may be supposed that the bottom sediments will be greatly polluted
by organic matter. As a matter of fact, it has been known among Japanese commercial oyster growers that in many of the oyster beds the oyster
crops decrease with the years, owing to their repeated use. Biodeposits
thus accumulated gradually modify the physical and chemical nature of
the bottom sediments and not only interfere with the lives of the oysters
but also often cause a high mortality during the summer season when
temperatures ara high.
To facilitate explanation of the complex process of biodeposition
involving many groups of animals and physical and chemical factors as
mentioned above, a clear illustration of the biodeposition cycle in the
estuary of the York River was furnished by Haven and MoralesAlamo (1966) (Fig. 30).
VIII. BIBLIOGRAPHY
Abbott, R. T. (1984). “American Seashells.” D. Van Nostrand Co. Inc., New
York.
Abbott, R. T. (1954a). Review of the Atlantic periwinkles, Nodilittorina, Echininus and Tecturius. Proc. U.S. natn. Mus. 103 (3328), 449-4G4.
Allen, J. A. (1962). Preliminary experiments on the feeding and excretion of
bivalves using P32. J . nmr. biol. Ass. U . K . 42, 609-623.
Amstutz, G. C. (1958). Coprolites: A review of the literature and a study of
specimens from Southern Washington. J . sedim. Petrol. 28(4), 498-508.
Arakawa, K. Y. (1960). Some ecological accounts on Scintilla witrea Quoy and
Gaimard. Venus, Tokyo, 21(1), 61-66.
Arakawa, K. Y. (1962). A coprological study on the molluscan faeces (A preliminary note). (In Japanese with summary in English.) Vcnus, Tokyo, 22(2),
151-172.
Arakawa, K. Y. (1963). Notes on the faeces of Macroch.eira kaenipferi de Haan.
Res. Crustacea, 1, 7-8.
Arakawa, K. Y. (1963). Studies on the molluscan faeces (I). Prrbls Set0 mar.
biol. Lab. 11(2), 185-208.