remain closed for long periods out of water. Specimens held in a desiccator 

 contain an equivalent amount of CO2 to those held in air. This great 

 increase in CO2 content is not caused by death processes, because the 

 process is reversible if the clam is returned to seawater . Gill cilia and 

 heart beat normally. No important difference in pH develops in the pallial 

 cavity of clams held out of water, as compared with fresh clams. Con- 

 centration of CaC03 builds up in the same proportions as that of CO2. 

 Concurrently, erosion of the inside central portions of the valves occurs, 

 that is, in the part bounded externally by the pallial line. It is evident 

 that the increase in CO2 concentration is caused by dissolution of CaC03 of 

 the clam. CO2 concentration in mantle is not uniform. It increases most 

 sharply in the central part of the mantle in the same region as shell 

 erosion. No significant increase in CO2 occurs in other tissues. The 

 central region of the mantle must therefore dissolve CaC03 of the shell and 

 transport it to the liquid in the pallial cavity. During interruption of 

 normal respiration it functions to buffer metabolic acids. Because the 

 reaction is localized in a specific tissue, it seems that this provides a 

 favorable material for study of the mode of Ca transport. - J.L.M. 



524 



Dugal, Louis-Paul, and Laurence Irving. 1938. 



The relation of the shell to anaerobic metabolism in Venus mercenaria. Biol. 

 Bull. 75(2): 352-353. 



When Venus mercenaria is kept out of water the C02 content of mantle cavity 

 fluid increases without much decrease of pH. Shell is visibly eroded under 

 the center of the mantle. Ca in the fluid increases more than CO2 , which 

 indicates formation of other acids. Small pH change indicates that the 

 other acid is neutralized and buffered, and glass electrode titration shows 

 that its pK corresponds with that of lactic acid. Volatile weak acid in the 

 fluid as determined by titration agrees with CO2 determined by Van Slyke 

 method. The sum of CO2 and other acid is equivalent to Ca. Thus, CO2 

 gained by the fluid is derived from shell and not by anaerobic or aerobic 

 metabolism. When the clam is out of water a process resembling glycolysis 

 in vertebrate tissue forms an acid, which is neutralized by the shell 

 through the living mantle. Part of the CO2 dissolved from CaC03 of the 

 shell remains in solution. Gains in CO2 and in non-volatile weak acid are 

 equivalent to gain in Ca, thus these are the only participants in buffering. 

 The process depicts well-regulated use of shell for buffering products of 

 glycolysis during anaerobic metabolism. - J.L.M. 



525 



Dunstan, W. M., and K. R. Tenore. 1972. 



Intensive outdoor culture of marine phytoplankton enriched with treated 

 sewage effluent. Aquaculture 1: 181-192. 



526 



Dunstan, William M., and Kenneth R. Tenore. 1974. 



Control of species composition in enriched mass cultures of natural phyto- 

 plankton populations. J. Appl . Ecol. 11: 529-536. 



In a series of 3 experiments in which cells were counted and identified 

 during the 6th to 10th day of the daily 50% harvest, N, P, and Si definitely 

 favored growth of diatoms. Addition of just N and P, or N, P, and trace 

 metals stimulated a green micro-algae population. Addition of treated 

 sewage effluent resulted in a 70-80% diatom culture. In another series of 

 experiments the rate of daily dilution was varied and in two experiments in 

 June a clear control of species composition resulted. In 10% daily dilution 

 green micro-algae dominated while at 75% dilution diatoms dominated, par- 

 ticularly Skeletonema costatum (now Stephanopyxis costata) . Results from 

 experiments in July and August were not as definitive as those in June and 

 the ubiquitous diatom Cylindrotheca closterium prevailed at all dilution 

 rates. Mercenaria mercenaria is not mentioned. - J.L.M. 



146 



