RELATIONSHIP BETWEEN BIODIVERSITY OF MACRO BENTHOS AND
PHYSICAL HABITAT CHARACTERS IN TIDAL FLAT IN EASTERN SETO
INLAND SEA, JAPANSOSUKE OTANI1, YASUNORI KOZUKI1, KENGO KURATA2, KAORI UEDA1, SHIGEFUMINAKAI1, HITOSHI MURAKAMI1
1Ecosystem Engineering, Graduate School of Engineering The University of Tokushima, Japan,

2

Research Center for Coastal Lagoon Environments, Shimane University, Matsue, JapanIntroduction
A numbers of public work projects have been implemented in Japan to create artificialtidal flats to utilize the function of tidal flat such as water purification and habitat for
macro benthos. Macro benthos plays an important role for those functions in tidal flat.
The relation between the distribution of the macro benthos and the environmental factors
is considered to be a key. This fact is used in the design of an artificial tidal flat and theforecast of the distribution of the macro benthos. However, the chemical characteristics ofsediments, such as the amount of the organism and the sulfide that are changeable inqualitative factors, have been used in current researches, nevertheless these chemical
characters cannot forecast the change of macro benthos properly. Therefore, when thecorrespondence of the macro benthos and sediments is generalized, a researcher should
focus on physical characteristics of sediments. The objective of this study was to study
the relationship between physical characteristics of sediments and the biodiversity.
MethodQuantitative quadrate sampling of macro benthos was carried out at 6 tidal flats ineasterner Seto Inland Sea, Japan(Figure.1). We determined Physical characteristics of thehabitat, in term of difference in elevation and sediment particle size. The sedimentparticle size was collected up to 4cm in depth by using the core sampler of 15mm in thediameter and sorted into pebble gravel (4.75~19mm), granule gravel (4.75~19mm),coarse sand (2~4.75mm), medium sand (0.85~2mm), fine sand (0.25~0.85mm), silt clay
(0.075~0.25mm).
Result1) A total of 192 species were collected at 187 stations on 6 tidal flats. 2) A rate of silt
clay and fine sand was significantly higher in sediments of estuary tidal flats than those offoreshore tidal flats. Pebble gravel and granule gravel did not exist in sediments ofestuary tidal flats. 3) Physical characteristics of sediment were classified into 9 groups bycluster analysis in relation sediment particle size and difference in elevation. 4) Thosegroups had also significant difference with physical characteristics of sediments andcharacterized by some specific macro benthos species. 5) The result suggested that thebiodiversity and the number of species have a positive correlation with the number ofsediment group. These results show that when the diversity of the sediments increases,
various macro benthos appear and the biodiversity increases (Figure.2).

Omaehama:6ha
Miyajima:11ha

Koushienhama:2ha

Yoshino:60ha
Katsuura:7ha

Waka:35ha
0Foreshore

50km

River-mouth

Figure.1 Study Area

Shannon-WeaverH'()

32.5
21.5
112

345

The number of assorted groups
YoshinoKatsuura
Waka

Miyajima
Omaehama
Koushienhama

Figure.2 Relationship between diversity of the sediments and the biodiversity