REARING O F BIVALVE MOLLTJSKS
56
of oysters or clams, growth of these organisms was stimulated, often
becoming considerably more rapid than in control cultures. Possibly,
this was a result of adsorption, by particles of such materials, of toxic
substances formed in larval cultures. It is also possible that some of
these materials that were added to the water contained a positive
growth factcr, as do certain soil solutions.
In summarizing the observations on the effect of turbidity on
oyster and clam larvae, it may be concluded that; larvae, as well as
dults, are affected by turbidity-creating substances, although larvae
seem to display a considerable tolerance towards some of these
materials. Moreover, larvae of different species react differently, one
species may be more tolerant or less resistant to the same material
under the same conditions. It is significant, nevertheless, that in some
instances comparatively light concentrations of common silt may
strongly interfere with normal development of eggs of some bivalves.
I. Effects of foods on growth of larvae
In any laboratory, where large numbers of adult and juvenile
mollusks are kept, these animals, becaust. of limited space, are often
crowded, receiving insufficient quantities of water and, therefore,
food. To improve these conditions we add large quantities of artificiallygrown plankton to the water flowing through troughs and trays.
Because of the scope of our work several hundred gallons. per day
of relatively rich phytoplankton are often needed. Obviously, it is
impractical to grow such large quantities of plankton in glass flasks
using common laboratory techniques. Fortunately, by merely adding
complete commercial fertilizers to sea waher, rapid growth of phytoplankton can be initiated and later maintaiiied in heavy concentrations.
Our experiments have shown that fertilizers designated by formulas
5-3-b and 6-3-6, both used by Connecticut tobacco growers, gave the
best results, although lawn fertilizer, 10-6-4, was also good (Loosanoff
and Engle, 1942). Using these fertilizers, mass cultures of rich, mixed
plankton have been continuously grown at our laboratory since 1938.
A wooden, 2000-gal oval tank is used for this purpose, although on
several occasions the cultures have been grown in outdoor, concrete,
10000-gal tanks. The sea water used in these tanks was passed through
a sand filter.
To supply the laboratory in winter. with a sufficient quantity of
plankton we designed a special enclosure, resembling a greenhouw, in
which a plankton-containing tank is instalhd (Fig. 21). By providing
artificial light, when needed, and maintaining the temperature of the
56
of oysters or clams, growth of these organisms was stimulated, often
becoming considerably more rapid than in control cultures. Possibly,
this was a result of adsorption, by particles of such materials, of toxic
substances formed in larval cultures. It is also possible that some of
these materials that were added to the water contained a positive
growth factcr, as do certain soil solutions.
In summarizing the observations on the effect of turbidity on
oyster and clam larvae, it may be concluded that; larvae, as well as
dults, are affected by turbidity-creating substances, although larvae
seem to display a considerable tolerance towards some of these
materials. Moreover, larvae of different species react differently, one
species may be more tolerant or less resistant to the same material
under the same conditions. It is significant, nevertheless, that in some
instances comparatively light concentrations of common silt may
strongly interfere with normal development of eggs of some bivalves.
I. Effects of foods on growth of larvae
In any laboratory, where large numbers of adult and juvenile
mollusks are kept, these animals, becaust. of limited space, are often
crowded, receiving insufficient quantities of water and, therefore,
food. To improve these conditions we add large quantities of artificiallygrown plankton to the water flowing through troughs and trays.
Because of the scope of our work several hundred gallons. per day
of relatively rich phytoplankton are often needed. Obviously, it is
impractical to grow such large quantities of plankton in glass flasks
using common laboratory techniques. Fortunately, by merely adding
complete commercial fertilizers to sea waher, rapid growth of phytoplankton can be initiated and later maintaiiied in heavy concentrations.
Our experiments have shown that fertilizers designated by formulas
5-3-b and 6-3-6, both used by Connecticut tobacco growers, gave the
best results, although lawn fertilizer, 10-6-4, was also good (Loosanoff
and Engle, 1942). Using these fertilizers, mass cultures of rich, mixed
plankton have been continuously grown at our laboratory since 1938.
A wooden, 2000-gal oval tank is used for this purpose, although on
several occasions the cultures have been grown in outdoor, concrete,
10000-gal tanks. The sea water used in these tanks was passed through
a sand filter.
To supply the laboratory in winter. with a sufficient quantity of
plankton we designed a special enclosure, resembling a greenhouw, in
which a plankton-containing tank is instalhd (Fig. 21). By providing
artificial light, when needed, and maintaining the temperature of the