Ka. Silva et al., SEASONALITY OF LIVING BENTHIC FORAMINIFERA FROM THE SAN-PEDRO BASIN, CALIFORNIA BORDERLAND, Journal of foraminiferal research, 26(1), 1996, pp. 71-93
Analysis of Rose Bengal-stained benthic foraminifera from six box core
s collected from the San Pedro Basin in April, July, and October, 1988
(similar to 720 m water depth) reveals that the foraminiferal assembl
ages vary during this six month period. Species diversity is low, with
five to six species constituting 90% of the total abundance in the >1
50 mu m fraction, In the 63-150 mu m fraction, eight species account f
or 90% of the total abundance in April, decreasing to three species in
July, and increasing to seven in October. Species are vertically stra
tified within the sediments, reflecting microhabitat preferences, and
are grouped according to their vertical patterns. In the >150 mu m fra
ction, three groups occur: 1) taxa having maxima from 0-1 cm, 2) infau
nal taxa with maxima from 1.5-3 cm, and 3) species with more complex d
istributions. In the 63-150 mu m fraction, two groups are identified:
1) infaunal species having maxima between 1-6 cm, and 2) species with
variable distributions in April, nearly absent in July, and displaying
subsurface maxima in October. No change in species distribution patte
rns was observed between April and October in either size fraction. A
comparison of the two size fractions of Chilostomella ovoidea and Buli
minella tenuata shows similar depth profiles, which suggests that ther
e are no ontogenetic changes of microhabitat preferences of these two
taxa. Maxima of Nonionella stella and Buliminella tenuata in July and
Bolivina spissa, Chilostomella ovoidea, Globobulimina pacifica, Fursen
koina bramlettei, and the agglutinated foraminifera in October suggest
that rapid growth occurred over a three month period.