Y. Chen et al., RELATIONSHIP BETWEEN BLOCK DETRITION DEGR EES OF SEA-BOTTOM SEDIMENT (HEDORO), AND GROWTH AND SURVIVAL RATES OF BROWN ALGAL SPROUTS, Nippon Suisan Gakkaishi, 61(3), 1995, pp. 346-355
As a link in the chain of effective utilization programs of sea-bottom
sediment (i.e. HEDORO), a survival-type seaweed culturing concrete bl
ock (which is hereinafter referred to simply as ''block'') was designe
d. The block is quite different from the existing kind, and it has suc
h a distinctive feature that a scanty detrition takes place on the blo
ck at all times so that its surface could be always renovated. The HED
ORO collected from the coastal sea bottom off Tomioka-Machi, Fukushima
Pref. consisted of clay and silt, and a volume mean diameter of those
composites was 11.3 mum; and its moisture content was 100%. In the wa
ter standing still, the detrition degrees of the specimen block mixed
with varied Portland cement rates differed one after another, indicati
ng that the lower degrees was inversely proportional to the cement rat
es from 10% to 50%. For example, the degree showed 9.10 x 10(-6) cm/da
y when the cement rate was 10%, and 1.16 x 10(-6) cm/day when it was 3
0%. Any changes in the detrition degree were not observed from 40 days
after setting on the blocks in the water. The block detrition degree
had not any correlation with the growth rate of gametophyte as well as
sporophyte of brown algae Eisenia bicyclis; and such a degree was in
inverse correlation to the survival rate of algal sprouts. For instanc
e, in case of the higher detrition degree of 6.07 x 10(-6) cm/day, the
survival rate of those sprouts on 16 days was smaller showing the val
ue of 23.2%; on the contrary, in case of the lower degree of 9.15 x 10
(-7) cm/day, it stood for the larger value of 56.6%.