Living (Rose Bengal Stained) Benthic Foraminifera in Sediments off the Southwest Taiwan Ai-Ping Chiang, Hui-Ling Lin, and Tai-Chun Lin Institute of Marine Geology and Chemistry National Sun Yat-sen University Kaohsiung, TAIWAN 804

Introduction Results and discussions Conclusions Outlines Study area

Introduction Studies of dead and living benthic foraminifera had shown that the organic carbon content in sediments, is the main factor controlling the distribution patterns and morphologic variations in benthic fauna (Corliss and Chen, 1986; Loubere and Gray, 1990; Jannink et al., 1998; Jorisson et al., 1998; Jorissen, 1999; Dulk et al., 1998, 2000). Other studies have demonstrated the sensitivity of the assemblage composition to changes in oxygen levels of the bottom water and within the sediment. As a result, the general contention is that oxygen and food supply are the main factors controlling the spatial and in-sediment distribution of benthic foraminifera. (Jorissen et al., 1995)

Therefore, the goal of this study is to examine what controls the spatial distribution of benthic foraminifera in Kao-ping Submarine Canyon in southwest Taiwan. Introduction

South China Sea Introduction

Kaoping Submarine Canyon Taiwan Strait Pacific Ocean This submarine canyon extends almost immediately seaward from the mouth of the Kao-ping River down to the lower continental slope over a distance of 240 km (Yu et al., 1993 and Liu, 2002). It eventually terminates in the northwestern corner of the South China Sea basin. This submarine canyon was considered the seaward continuation of the Kao-ping River (Yu et al., 1991). Kao-ping River Introduction

From: Kao-ping River 3-dimensional view of the sea-floor near the head of Kao-ping Submarine Canyon. The water depths are represented by the color bar. Introduction

Locations of study area Kao-ping River 242m 1360m 130m 561m 94m 440m 362m 723m 1126m Study area

Results and discussions 1 ‧ TOC % (total organic carbon) 2 ‧ Abundance of benthic foraminifera 3 ‧ Living (stained)/total benthic shells ratio (for each individual species) Analysis items

Benthic foraminifera abundance and TOC %

Station N1

Station N2

Station KP1-KP5

Station S Station S2

These results suggest that variations in total organic carbon contents do not preferentially affect benthic foraminifera abundance.

Hess and Kuhnt (1996) used the ratio of living specimens to the total abundance of species to determine the succession of recolonizers, assuming that species with high numbers of dead individuals probably colonized earlier than species with higher numbers of living individuals. The purpose of Rose Bengal is to stain organisms that were alive at the time of collection. (Hess et al,2001) Living (stained)/total benthic shells ratio (for each individual species)

Stained/total ratio

Stained foraminifera aboundance

Stained/total ratio In view of the higher stained/total ratio and lower dead tests, we are inclined to interpret the appearance of stained benthic foraminifera in the head of Kao-ping Submarine Canyon as the effect of migration, rather than caused by differential reproduction or differential mortality.

What causes the effect of migration? Arrows in this diagram represent the existence of transport directions according to the McLaren Model analysis plotted over the 3-D bathymetry of the study area. Each line of arrows represents a predetermined orientation of transport. The isobaths are in meters. (Liu et al )

Conclusions This study is the first report regarding the stained benthic foraminifera in Taiwan, especially in the region of Kao-ping Submarine Canyon, off the southwest island. Different from previous studies, the spatial distribution of stained benthic foraminifera seems not to be related with TOC contents in sediments. The higher stained/total ratio and lower dead tests at the head of Kao-ping Submarine Canyon than adjacent area might be the effect of migration, which could be resulted from complex interaction between tides and currents.