rates for each of the lakes was similar despite different seasons of coring 

 each lake and averaged about 2000 (i.e., 2000 yg Si/cm2/yr) micrograms 

 Si/cm2/yr. If this flux represents an annual average then the amount of Si 

 regenerated from sediments each year in Lake Erie for 

 The vertically integrated amount of dissolved silicon 

 is a maximum of about 200 micrograms/cm^, so the time 

 the Si removed from the water (through incorporation 



example is enormous, 

 in the water column 

 required to replenish 

 into diatoms) by re- 



generation from sediments is 0.1 year. Robbins and Edgington (1979) found 

 that the flux of Si from sediments in Lake Erie is proportional to the con- 

 centration of amorphous silicon in surface sediments suggesting the flux is 

 dominated by dissolution of particulate cilica recently deposited on the 

 sediment surface. This result indicates a particular role for organisms 

 like the larvae of Chironomids which are shallow water plankton detritus 

 feeders and whose effect on the release of silicon from sediments was noted 

 many year ago by Tessenow (1964). 



By comparing silicon fluxes with benthos densities in a series of repli- 

 cate cores taken on two cruises in Saginaw Bay, Lake Huron, last year (fall 

 1978), we have been able to confirm Tessenow's observations for our particu- 

 lar Great Lakes environment. Shown in Table 1 is the density of benthos in 



TABLE 1. BENTHOS DENSITY AND SILICON FLUX: SAGINAW BAY, LAKE HURON 



"•October, 1978. 

 ^November, 1978, 



each of several replicate core 

 timed sampling of overlying wa 

 the dominant species in terms 

 However, densities of these or 

 as can be seen from Table 2. 

 most correlations are not sign 

 Si flux and the density of Chi 

 for both observation periods ( 

 ents were measured as well and 

 both cruises are underlined 



s along with the silicon flux measured via 

 ter as described above. It can be seen that 

 of numbers are the immature tubificid worms, 

 ganisms correlate poorly with the silicon flux 

 Because of the limited number of observations 

 ificant. However, the correlation between the 

 ronomids is outstandingly high and significant 

 Figure 12). In this experiment, other nutri- 

 correlations which are persistently high over 

 The observed decrease in the concentration of 



217 



