Download Species Diversity and Distribution of Cnidarians in

Species Diversity and Distribution of Cnidarians in Raffles Marina
Teo, D. L. E.1 and Chou, L. M.2
Department of Biological Sciences, Faculty of Science, National University of Singapore
10 Kent Ridge Crescent, Singapore 119260
ABSTRACT
In Singapore, limited research on Cnidarian biodiversity in semi-enclosed water-bodies like
boating marinas has been done. Marina construction leads to changes in water quality due to
introduction of pollutants, and modification of hydrodynamics, thus causing habitat degradation,
and the resulting loss of many native marine fauna. Bioremediation measures aim to improve
and restore water quality. Prior to bioremediation, biological monitoring of the selected area has
to be done periodically and one useful way is to use bioindicators. Cnidarians require specific
environmental conditions for growth and survival and are sensitive to slight changes. Therefore
the objective of this research is to investigate cnidarian biodiversity and distribution in Raffles
Marina so as to identify potential bioindicators. A basic visual survey was conducted, in situ
photographs were taken and specimens were collected for further identification by comparing
differences in morphology, size and color using identification keys and reference pictorial
guides. A distribution map was created to represent the occurrences and abundance of various
classes in the marina. Up to twelve genera were identified and their distribution in the marina
reflects the specific conditions required for them to survive. Among the five marinas in
Singapore, Raffles has been observed to have highest cnidarian diversity.
INTRODUCTION
Marina construction leads to changes in water quality due to the introduction of various
pollutants, as well as increases in turbidity due to increased levels of sedimentation.
Sedimentation causes the choking up of marina seafloor and reduces dissolved oxygen content,
thereby creating an anoxic environment detrimental to living organisms. In addition, there
would also be a modification of hydrodynamics, which would cause habitat degradation, and the
resulting loss of many native marine fauna.
Bioremediation measures aim to improve and restore water quality. Prior to bioremediation,
biological monitoring of the selected area has to be done periodically and one useful way is to
use bioindicators. The detection of signs of environmental degradation and ecological stresses
could be the role of bioindicators, which have to be equipped with high sensitivity to the
environment they are placed in. Cnidarians require specific environmental conditions for growth
and survival and are sensitive to slight environmental changes. This group of animals
coincidentally fit into the criteria of being bioindicators and this includes hydroids, jellyfish, sea
anemones, zoanthids, gorgonians, hard and soft corals.
In general, cnidarians thrive in tropical waters with warm temperatures, low sedimentation
and stable salinity and this area covers Singapore. Therefore the objective of this research is to
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Student
Professor
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investigate cnidarian biodiversity and distribution in Raffles Marina so as to identify potential
bioindicators in the local context.
MATERIALS AND METHODS
To investigate the species diversity of cnidarians in a marina, the following methods were
used. A basic visual survey was conducted, in situ photographs were taken and specimens were
collected for further identification. It is important to know the exact parts of each specimen to be
collected and identified. Each specimen was accompanied with a label that contained relevant
information about its characteristics. All specimens collected were placed temporarily in plastic
containers in 70% alcohol for preservation. Using identification keys and reference pictorial
guides, descriptions and photographs of the specimens were compared for differences in
morphology, size and color, verified and identified to the lowest rank possible. A distribution
map was created to represent the occurrences and abundance of various classes in the marina.
RESULTS AND DISCUSSION
The identification of specimens collected at Raffles Marina is listed in Table 1 and the
distribution map representing the location and abundance of cnidarians in the marina is
illustrated in Figure 1. Up to twelve genera of cnidarians were identified and their distribution in
the marina reflects the specific conditions required for them to survive. The species richness of
cnidarians in a semi-enclosed estuary such as Raffles Marina can be considered high in
comparison with the other four marinas in Singapore, where cnidarians were absent or in very
low abundance. The pattern of distribution of the various classes of cnidarians in the marina
shows a relation between the physical factors and environmental conditions the organisms
require for survival, and the locality and abundance of the species at different sites in the
marina. The results from this study on the occurrence and abundance of various classes of
cnidarians at Raffles Marina will enable the identification of potential species found within the
marina to be used in the biological monitoring and remediation of waters within the marina.
CONCLUSION
As a holistic approach to understanding and maintaining biological diversity and water
quality in semi-enclosed marina waters, it is essential to study the animals found within the
marina in relation to the hydrodynamics of the water and marina architectural design. A good
understanding of these can help improve the management of marinas, in relation to maintaining
a healthy ecological balance.
ACKNOWLEDGEMENTS
Professor Chou Loke Ming, Karenne Tun and all who have helped and contributed in this
project are greatly appreciated.
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Table 1. List of identified cnidarians found in Raffles Marina.
Class
Hydrozoa
Subclass
Hydroidea
General group
describes
Hydroid
Anthozoa
Alcyonaria or
Octocorallia
Soft coral
Sea fan or gorgonian
Zoantharia or
Hexacorallia
Sea anemone
Hard coral
Zoanthids
Species
Sertularia sp.
Sertularella sp.
Plumularia sp.
Undetermined stinging hydroid
Dendronepthya sp.
Nephthea sp.
Stereonepthya sp.
Sarcophyton sp.
Subergorgia sp.
Subergorgia suberosa
Heteractis sp.
Oulastrea crispata
Zoanthus sp.
Figure 1. Distribution of cnidarians in Raffles Marina
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