POLYCHAETES: THE MARINE WORMS
Polychaetes are dominant benthic fauna in the marine environment. These marine worms are multi-segmented annelids with parapodia. Their secretive habits often made them easily overlooked by casual observers but around 10,000 species have been described wo
rldwide so far. Many of them are strikingly beautiful, colored red, pink or green or a combination of colors. The majority of them are less than 10 cm long and between 2 mm and 10 mm wide.
Polychaetes occur in most habitats ranging from estuaries and inshore waters to the open sea and hyper saline lagoons. Many species are found along intertidal areas, especially on sandy or muddy beaches. Majority of these ancient group of worms are bent
hic while 50 planktonic species are distributed throughout the worldís region.
In Singapore, a need is clearly sought for taxonomic and ecological studies on polychaetes as the information of local polychaetes is obviously lacking. A major of the polychaete collection in Singapore had been contributed by
the Reef Ecology Study Team, School Of Biological Sciences, NUS. Over the years, benthic surveys were conducted by the Reef Ecology Study Team for the Asean-Australia Marine Science Project : Liv
ing Coastal Resources. Both fauna and sediment samples were collected using a Smith-McIntyre Grab or a Charcot dredge. The sites surveyed include:
A total of 57 families were recorded from these surveys. The majority
of the specimens were identified only to family level due to inexperienced personnel and insufficient literature. The most dominant family in the study was
Eunicidae which are mostly found in coastal locations.
Importance of Polychaetes
- Some of the polychaetes are known to be economically important. Both the adult and larvae of the family Nereidae has been reported to be food for many economically important fishes. They are also used as bait for recre
ational fishing. In coastal areas of Fujian,Guangdong, Guangxi and Southeast Asia regions (Wu et al. 1985) they are a delicacy. Since the polychaetes are the main food supply of many commercial fishes, they also serve as an important factor in the evalu
ation of fishing grounds. Therefore, the information on their biology, ecology and distribution is necessary for their conservation (Natividad & Palpal-Latoc 1986).
- Polychaetes also play an important role in biomonitoring the marine environmental quality being monitors for toxic materials and pollution indicators.. The primary objective of biomonitoring is to access the impact of man-made changes such as the in
troduction of toxic chemicals on the biosphere by examining the effects on the chemicals have on the polychaete through bioessay techniques, the body burdens of the chemical residues in selected organisms and examining the biodata which have been affected
by the chemical contaminants at the various levels. Countries using polychaetes as pollution indicators include USA, UK, Canada and Germany.
- The use of polychaetes in monitoring the marine environmental quality is due to their direct contact with the water column and the sediments of their environment thus showing sensitivity to anthropogenic compounds which is expressed through changes in
their reproduction, growth and mortality.
- Being abundant, having a short life cycle and covering a wide range size, polychaetes from the families Nereidaeand Dorvilleidae are suitable for assessing the toxicity of sediments. They a
re good monitors of the presence and bioaccumulation potential of anthropogenic compounds such as PCBs, PAH and metal organic complexes as the polychaetes accumulate deleterious materials within their tissues in concentrations proportional to concentrat
ions found in the environment.
- The presence and absence of specific polychaetes in sediments provides an indicator of the condition and health of the benthic environment as they are the dominant microfauna within the fine sediments. Large numbers of the families Capitellidae and Spionidae found to the exlusion of others have been accepted widely as pollution indicators. Rygg (1985) suggests that the absence of sensitive species such as Harmothoe imbricata and M
aldane sarsi would be indicative of detrimental environmental conditions. He further suggests that if Paramphinome, Ceratocephale, Harmothoe and Lumbrineris are absent, and the diversity is low, the chances that the site is impacted is g
reat. Species of Nereidae and Nephytidae are accepted as indicators of early successional phases of environmental discovery after pollution has been abated (Pearson & Rosenberg, 1978).
- Polychaetes are very useful organisms for monitoring the marine environment. They are readily available, easy to sample, available commercially and easy to maintain. They respond quickly to changes in environmental conditions. The ability to monitor
different phases in the recovery of disturbed sites is possible because the different species of polychaetes appear after the cessation of the impact.
The main limitation of using polychaetes as monitors are
- the paucity of taxonomic and biological information for many species.
- there is little biological information on the life histories and seasonal variation of endemic populations
- the information on their natural responses to the other environmental parameters is limited and the ecotoxicology is still at infancy stage thus complicating interpretation of field data.
- The expertise to work on polychaetes is being improved and the potential for their greater use is being recognized. To realize their potential, each country should know more about its indigenous polychaete fauna. This can be achieved by having a list
of local polychaetes and atlases showing their distribution.
- A computer based taxonomic tool like the EPIC-online serves as a useful identification tool towards the first step of identifying the indigenous polychaetes in Singapore which is accessible via the internet.