3069
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1
Development and Verification of Ecohabitat Chart based on Ecological Geotechnics
Développement et Vérification de Ecohabitat Diagramme ont basé sur Écologique Géotechnique
S. Sassa & Y. Watabe
Port and Airport Research Institute, Japan
S. Yang
Jeju National University, Korea
ABSTRACT: By utilizing our new approach in Ecological Geotechnics, we performed series of controlled laboratory experiments on
benthos-soil systems with six species of invertebrates that belonged to Arthropoda, Mollusca, and Annelida. The experimental results
demonstrated that for each of the burrowing activities, there exist optimal, transitional and critical geoenvironmental conditions,
which were found to differ considerably between species, body sizes and weights. On the basis of these results, we have constructed
an ecohabitat chart which enables an interspecific comparison of the burrowing performances and capabilities of the diverse benthic
fauna in light of the associated geoenvironments in the field. The results of integrated field observations and surveys at various natural
and artificial intertidal flats further demonstrate the validity and effectiveness of the ecohabitat chart in not only evaluating but also
predicting the linkage between the species distributions and the ensuing geoenvironments. Hence, the present findings, together with
the developed chart will effectively contribute to a new horizon of the performance-based geoenvironmental assessment, design and
management for the conservation and restoration of habitats with rich ecosystems in intertidal zones.
RÉSUMÉ : En utilisant notre nouvelle approche dans Écologique Géotechnique, nous avons exécuté série d'expériences de laboratoire
sur les systèmes du benthos-sol avec six espèces d'invertébrés qui ont appartenu à Arthropoda, Mollusca et Annelida. Pour chacun des
activités fouisseuses, là a existé des optimales, transitionnelles et critiques geoenvironmental conditions qui ont différé
considérablement entre espèces, dimension du corps, et poids qui ont permis le développement d'un diagramme de l'ecohabitat. Ce
diagramme a été validé à travers champ études de l'intertidal naturels et artificiels. Les conclusions contribueront à un nouvel horizon
de du geoenvironmental performance-basée estimation et gestion pour la conservation et restauration d'habitats avec les écosystèmes
riches dans les intertidal zones.
KEYWORDS: ecological geotechnics, geoenvironment, intertidal flat, ecosystem.
1 INTRODUCTION
Biodiversity in oceans has received increasing attentions in
recent years, particularly following the COP10 initiative to
conserve and restore the valuable ecological systems. Intertidal
zones are the vital elements in the sustainability of estuarine and
coastal environments since they foster rich natural ecosystems.
Previous research in the fields of ecology and water science has
been directed to understanding the diversity of ecosystems, their
water purification functions and associated hydroenvironments.
However, geoenvironments as habitats and their linkage with
biological activity remain poorly understood, although their
complete understanding is crucial to the conservation and
restoration of habitats.
Recently, we developed an integrated continuous
observation system that enables close inspection of the
geoenvironmental dynamics that take place in the zones relevant
to benthos diversity and applied it to intertidal flats (Sassa and
Watabe, 2007). Through the combined use of field,
experimental and theoretical investigations, we have found that
the dynamics of suction associated with tide-induced
groundwater level fluctuations play a substantial role in
controlling the geophysical environments of habitats (Sassa and
Watabe, 2007), and there is a close linkage between the
waterfront geophysical environment and the ecology of
intertidal flats (Sassa and Watabe, 2008; Kuwae et al., 2010;
Sassa et al., 2011).
The paper reports our recent findings from such new cross-
disciplinary research field which we call
“
Ecological
Geotechnics
”
(Sassa and Watabe, 2009). Specifically, the
present study aims to investigate systematically the burrowing
performances and capabilities of diverse species that belong to
Arthropoda, Mollusca, and Annelida, and to develop an
ecohabitat chart by which to evaluate the interrelationships
between suitable and critical geoenvironment among species.
The validity of the ecohabitat chart is assessed in light of the
results of integrated field observations and surveys of the
waterfront geoenvironment and species distributions at various
natural and artificial intertidal flats.
2 DEVELOPMENT OF ECOHABITAT CHART
For the purpose of the present study, we targeted diverse species
such as bivalves, worms, crabs, shrimp and decapod crustacean
and realized an integrated comparison of the burrowing
performances though a range of controlled laboratory
experiments of benthos-soil systems. For the materials, we used
tidal flat soils as well as agar based on the study of Sassa &
Watabe (2009). In the series of the experiments, we simulated
and varied the vane shear strength according to the procedures
described in Sassa & Watabe (2009), and investigated the
burrowing responses of each of the six species used, for one
hour period. In cases where burrowing was possible, an
individual burrowed under the soil surface. In contrast, in cases
where burrowing was impossible, the whole body remained on
the soil surface. For the bivalves and shrimp, partial burrowing
manifested, and thus in order to elucidate their burrowing
capabilities, we examined their responses for six hour period.
All of the individual species were collected from natural
intertidal flats such as Banzu, Ena, Nojima and Furenko
intertidal flats, and acclimated in a water tank for the period of
one month under constant air and water temperatures. We used
ass S., Watabe Y.
Yang S.
