The ecology of living (stained) deep‐sea benthic foraminifera from the Sulu Sea

Abstract

The distribution of living (rose bengal stained) deep‐sea benthic foraminifera was determined in the upper 20 cm of sediments of eight Soutar box cores taken from two depth transects (510‐4515 m) in the thermospheric (> 10°C) Sulu Sea. Despite the uniformity of bottom water temperatures, salinities, and dissolved oxygen levels below 1000 m, significant faunal differences exist at different depths in the low‐oxygen (∼1.25 mL/L below 1000 m) basin. The shallowest site (510 m) is dominated (> 10% of the calcareous fauna) by Cibicidoides, Uvigerina, (> 150 µm) and Bolivina (> 63 µm), while Siphonina is codominant with Cibicidoides and Uvigerina in the 1005‐m core. The 2000‐m cores are dominated by Cibicidoides, Gyroidinoides, and Oridorsalis, while Cibicidoides bradyi and Oridorsalis umbonatus dominate the 3000‐ and 4000‐m cores. Infaunal assemblages of Valvulineria mexicana are found in the sediments of the 4515‐m core. Relatively low bottom water oxygen values do not necessarily yield "typical low‐oxygen taxa" such as Bolivina, Uvigerina, Chilostomella, Bulimina, and Globobulimina. Changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments. An examination of the vertical distributions of foraminiferal assemblages from the > 63‐µm and > 150‐µm fractions reveals that taxa have microhabitat preferences similar to those observed in other regions. Taxa found in the upper 0‐ to 1‐cm interval (epifaunal) include Cibicidoides wuellerstorfi and Hoeglundina elegans, while taxa such as Chilostomella and Globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences. Cibicidoides bradyi and O. umbonatus live in sediment depths from 0‐ to 4‐cm and have transitional preferences with both epifaunal and infaunal occurrences. Intrageneric differences in test morphologies, including pore distribution, rounded peripheries, and variable spire height, are observed in Cibicidoides and Gyroidinoides and are suggested to be related to microhabitat preferences. Vertical distributions of a number of taxa found in both the 63‐ to 150‐µm and > 150‐µm fractions are similar, suggesting that juveniles and adults live under similar microhabitat conditions. Ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies.

Timing of Langhian bioevents in the Carpathian Foredeep and northern Pannonian Basin in relation to oceanographic, tectonic and climatic processes

“…and deep infaunal Uvigerina spp. (Caralp, 1989;Hermelin, 1992;Sjoerdsma and Van der Zwaan, 1992;Sen Gupta and Machain-Castillo, 1993;Miao and Thunell, 1993;Rathburn and Corliss, 1994).…”

Historical records of coastal eutrophication-induced hypoxia

“…Here, the faunas are rich in uvigerinids and buliminids (Jorissen et al, 1998), which are often considered as low oxygen markers. Conversely, in the Sulu Sea, where fairly low oxygen bottom waters (<2 ml L −1 ) occur in a moderately oligotrophic context, the density of species traditionally considered as low oxygen markers is surprisingly low (Rathburn and Corliss, 1994). Several experimental studies have tried to distinguish between the effects of hypoxia/anoxia and food input.…”

Recostruction of the unusual Mid Miocene (Badenian) palaeoenvironment of the Carpathian Foredeep (Lomnice/Tišnov denudational relict, Czech Republic)

“…Stud ies of Re cent Uvigerina as well as Melonis show that a high sup ply of or ganic ma te rial to the sed i ments and not the ox y gen concen tra tion in the bot tom wa ters is the most im por tant fac tor in con trol ling dis tri bu tion of both gen era (Caralp, 1989;Hermelin, 1992;Sjoerdsma and Van der Zwaan, 1992;Sen Gupta and Machain-Castillo, 1993;Miao and Thunell, 1993;Rathburn and Corliss, 1994). Then, abun dant Uvigerina, Bolivina, Bulimina and Melonis typ ify re gions of high or ganic pro duc tiv ity and a sus tained flux of or ganic mat ter to the sea-floor, e.g., un der areas of upwelling (Thomas et al, 1995) which can sup port an infer ence of sea sonal upwelling from plank tonic as sem blages.…”