Seasonality of living epiphytic foraminifera from seagrass beds in nearshore zones of the Ryukyu Islands, Japan

Kazuhiko Fujita, Hiroshi Nishi, Tsunemasa Saito

研究成果: Article査読

5 被引用数 (Scopus)

抄録

Seasonality of epiphytic foraminiferal populations living on leaves of seagrass has been studied in seagrass beds in the nearshore zone of Irabu Island, the Ryukyu Islands. For this study, seagrasses in a 100 cm2 sample area were collected monthly between February 1996 and November 1996, and in April 1997. The epiphytic foraminiferal assemblage consists predominantly of calcareous taxa, being dominated by a phytal form species, Calcarina calcar d'Orbigny, throughout the year. The assemblage is also associated with Hauerina pacifica, Vertebralina striata, Lamellodiscorbis sp. and Glabratella millettii during late winter and spring, and with Quinqueloculina seminulum, Q. semireticulosa, Bolivina striatula, and Cymbaloporetta plana during fall. Therefore, crawling forms increased in spring, and free living and attached forms are relatively abundant in fall. The species diversity increases in spring and fall, but drops in summer. The total abundances of foraminifers fluctuate seasonally from 2,258 individuals/g seagrass dried in spring to 128 individuals/g seagrass dried in late summer. Population dynamics of the dominant species C. calcar controls strongly these seasonal changes of total assemblage. The percentage of adult specimens with reproduction chambers and a large increase in the specimens smaller than 500 μm indicate that asexual reproduction typically occurs during spring. The spring is, therefore, most comfortable season for all epiphytic foraminifers, whereas summer season is so severe for survival and most of foraminifers die during late spring through summer. These seasonal variations in the epiphytic foraminifers are probably related to the changing regional environmental conditions within seagrass beds, such as food supply or physical factors, e.g. temperature, salinity and vertical circulation of water column.

本文言語English
ページ(範囲)16-33
ページ数18
ジャーナルFossils
66
出版ステータスPublished - 1999 9月 10
外部発表はい

ASJC Scopus subject areas

  • 古生物学

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