Hydrobiological Investigations in Ayyampattinam Coast (Southeast Coast of India) with Special Reference to Zooplankton
C. Santhosh Kumar
An investigation was made on the influence of physico-chemical parameters on zooplankton composition of Ayyampatinam coastal region situated in southeast coast of India (Lat. 09°54 N: Long. 79°08 E). Quantitative and qualitative analysis of zooplankton besides physico-chemical parameters were carried out from October 2007 to September 2008. 45 species of zooplankton were recorded, Copepoda formed the major fraction (44%) followsed by other metazoans (25%), decapodal larval forms (15%), Ciliats (8%), Foraminiferans (3%), Hydromedusae (2%), Decapoda (2%) and Appendicularians (1%). Higher values of zooplankton density and species diversity were found during premonsoon and summer seasons. The seasonal distribution and abundance of zooplankton are discussed in relation to hydrographical parameters.
May 22, 2010; Accepted: July 15, 2010;
Published: August 18, 2010
Zooplankton is the primary consumers of the oceans and grazes on the phytoplankton.
They themselves are an important food source for large animals. Basking sharks,
whales, fish and some species of rays rely on zooplankton for their food supply.
Most fishes and prawns during their critical phase receive their nourishment
by feeding on copepods Zooplankton provides an important food source for larval
fish and shrimp in natural waters and in aquaculture ponds. It has been reported
that in many countries the failure of fishery was attributed to the reduced
zooplankton especially copepod population (Stottrup, 2000).
Success of aquaculture of fin and shell fishes depend upon the availability
of live-feed organisms like copepod. Studies on zooplankton communities, especially
copepods are very important in assessing the health of coastal ecosystems (Ramaiah
and Nair, 1997). Most of the planktonic organisms are restricted in the
neritic zone due to abundance of nutrients, light and favorable physico-chemical
variables like water temperature, dissolved oxygen, salinity and pH etc. Information
on species diversity, richness, evenness and dominance evaluation on the biological
components of the ecosystem is essential to understand detrimental changes in
environs (Krishnamoorthy and Subramanian, 1999; Ashok
Prabu et al., 2005). Species composition and seasonal variation in
zooplankton abundance has been studied in other regions of Indian coastal waters
(Gopinathan et al., 2001; Ashok
Prabu et al., 2005; Mathivanan et al.,
2007). Phytoplankton initiates the marine food chain, by serving as food
to primary consumers like zooplankton, shellfish and finfish (Saravanakumar
et al., 2008). Since, zooplankton are at the base of the marine
ecosystems, understanding their properties and the relationships between them
will allow us to detect and avoid a potential crash in the ecosystem (Conway,
2005). Ayyampattinam coast is a fishery landing place. Present investigation
was made on the spatial and temporal changes of zooplankton from Ayyampattinam
region in relation to hydrography.
MATERIALS AND METHODS
The Ayyampattinam coast (Fig. 1) is situated 45 km North of Thondi and it is a fishing hamlet (Lat. 09°54 N: Long. 79°08 E). Rainfall data collected from October 2007 to September 2008 and were obtained the local meteorological unit (Govt. of India) located at Manamelkudi, Southeast coast of India. Temperature was measured using a standard Centigrade Thermometer. Salinity was estimated with the help of a hand refracto meter (ATAGO) and pH by using a ELICO Grip pH meter.
Water samples were collected in one liter clean polythene bottle at the monthly
interval at Oct. 2007 to Sep. 2008. Samples were kept in an ice box and immediately
transported to the laboratory. Initially water samples were filtered through
the Millipore filter system to remove the plankton and debris. Filtered seawater
was used for analysis of nutrients like inorganic nitrate, nitrite, inorganic
phosphate, reactive silicate and ammonia by the standard method of Stickland
and Parsons (1972).
The zooplankton samples were collected through Indian ocean standard net (dia=
0.36 m; mesh size 158 μM; cloth No. 10) during the full moon day of the
Oct. 2007 to Sep. 2008. For the quantitative analysis 500 L of water were filtered
through conical plankton net made up of bolting silk having the same mesh size
of the net.
|| Study area
Zooplankton samples were preserved in 5% neutralized formalin and used for
quantitative analysis. Zooplankton were identified using the standard works
of Kasturirangan (1963), Newell and
Newell (1977), Smith (1977), Wimpenny
(1966), Todd and Laverack (1991) and
Perumal et al. (1998).
Biodiversity indices were calculated following the standard formulae of Shannon
and Weaver (1949) diversity index (H), Gleason
(1922) richness (D); Pielou (1966) evenness. Pearson
correlation co- efficient (r) values calculated to understand the relationships
between distribution, diversity of zooplankton and hydrographical features.
RESULTS AND DISCUSSION
The total rainfall recorded was 1708.1 mm at Ayyampattinam. The remarkable variations were noticed in salinity and temperature patterns. The surface water temperature varied from 25.5 to 33.4°C and the salinity varied from 23 to 35 ppt (Fig. 2), whereas, only limited variations were observed in pH and Do distribution. The pH values fluctuated between 7.8 and 8.2 and the Do (mL L-1) from 3.6 to 5.2 (Fig. 2). Nitrates values (μg L-1) ranged between 3.21 and 6.34 (Fig. 2), Nitrites (μg L-1) varied from 0.74 to 0.896 (Fig. 2). Phosphates (μg L-1) ranged between 0.22 and 1.16 (Fig. 2). The ranges of reactive silicate (μg L-1) were: 24.85-61.92 (Fig. 2). The concentrations of ammonia (μg L-1) ranges were: 0.05-0.32 (Fig. 2).
Totally 45 zooplankton were identified at Ayyampattinam coastal region, which comprised of Foraminifera (2 species), Copepoda (24 species), Decapoda (1 species), Appendicularia (1 species), Chaetognatha (1 species), Hydromedusae (1 species), Ciliata (6 species), Cladocera (1 species) and Larvae (8) (Table 1). Presently recorded zooplankton consisted of 45 forms including 8 larvae. The descending order of abundance of the various groups of zooplankton is as follows: Copepoda> Larvae>Ciliata>Cladocera>Chaetognatha>Foraminifera>Decapoda.
The ranges of population densities (Org L-1) of zooplankton were: 3300-20262. During the study period the individual species of Oithona brevicornis were dominant. The maximum density of zooplankton was recorded during premonsoon period. In copepod population, calanoida is the most dominant and it contains 15 species. The species diversity ranged from 3.75 to 4.62; species richness varied between 0.91 and 0.94; species evenness ranged from 0.92 to 0.97 (Fig. 3).
Physico-chemical variables in the marine environment are subjected to wide
temporal variations. Rainfall is the most important cyclic phenomenon in tropical
countries as it brings about important changes in the physical and chemical
characteristics of the coastal environment. The rainfall in India is largely
influenced by two monsoons viz., Southeast monsoon on the West coast and Northeast
monsoon on the east coast (Perumal, 1993). The salinity
acts as a limiting factor in the distribution of living organisms and its variation
caused by dilution and evaporation is most likely to influence the fauna in
the coastal ecosystems (Balasubramanian and Kannan, 2005;
Sridhar et al., 2006).
Presently, the salinity was found to be high during summer season and low during
the monsoon season. Generally, its seasonal variation is attributed to factors
like removal of CO2 by photosynthesis through bicarbonate degradation,
dilution of seawater by freshwater influx, low primary productivity, reduction
of salinity and temperature and decomposition of organic matter (Karuppasamy
and Perumal, 2000; Rajasegar, 2003; Paramasivam
and Kannan, 2005). The recorded higher values (34.0%) could be attributed
to the low amount of rainfall, higher rate of evaporation and also due to neritic
water dominance, as reported by earlier workers in other areas (Govindasamy
et al., 2000; Rajasegar, 2003). The minimum
salinity recorded during the monsoon season and the maximum was recorded during
summer season as reported earlier by Sundaramanickam et
||Temporal variations of temperature, salinity, pH, dissolved
oxygen, ammonia, nitrite, nitrate, phosphate and silicate in Ayyampattinam
coast, south east coast of India
The recorded high Summer pH might be due to the influence of seawater inundation
and biological activity and due to the presence of high photosynthetic organisms
(Das et al., 1997; Santhanam,
1998). The observed high monsoonal values might be due to the cumulative
effect of higher wind velocity coupled with heavy rainfall and the resultant
freshwater mixing (Das et al., 1997).
|| List of zooplankton of the ayyampattinam area
|D: Dominant, M: Moderate, R: Rare
|| Seasonal variations of zooplankton population density, diversity,
richnness and eveness
Mitra et al. (1990) have mainly attributed seasonal
variation of dissolved oxygen to freshwater flow and terrigenous impact of sediments.
Nutrients are considered as one of the most important parameters in the estuarine
environment influencing growth, reproduction and metabolic activities of living
beings. Distribution of nutrients is mainly based on the season, tidal conditions
and freshwater flow from land source. Presently recorded high monsoonal values
could be mainly due to the organic materials received from the catchment area
during ebb tide (Das et al., 1997). The increased
nitrates level was due to fresh water inflow, mangrove leaves (litter fall)
decomposition and terrestrial run-off during the monsoon season (Karuppasamy
and Perumal, 2000; Santhanam and Perumal, 2003).
The recorded low values of nitrate may be due to its utilization by phytoplankton
as evidenced by high photosynthetic activity and also due to the neritic water
dominance, which contained only negligible amount of nitrate (Govindasamy
et al., 2000).
The recorded earlier Summer nitrite values could be due to the increased phytoplankton
excretion, oxidation of ammonia and reduction of nitrate and by recycling of
nitrogen and also due to bacterial decomposition of planktonic detritus present
in the environment (Govindasamy et al., 2000).
The recorded low nitrite values during summer season may be due to less freshwater
inflow and high salinity (Mani and Krishnamurthy, 1989;
Murugan and Ayyakkannu, 1991).
The recorded high concentration of inorganic phosphates during monsoon season
might possibly be due to intrusion of upwelling seawater into the creek, which
in turn increased the level of phosphate (Nair et al.,
1984). Low Summer values could be attributed to the limited flow of freshwater,
high salinity and utilization of phosphate by phytoplankton (Senthilkumar
et al., 2002). The variation may also be due to the processes like
adsorption and desorption of phosphates and buffering action of sediment under
varying environmental conditions (Rajasegar, 2003).
The recorded high concentration of inorganic silicate content was higher than
the other nutrients (NO3, NO2 and PO4) and
higher value was noticed during monsoonal season when the salinity was very
low and this may be due to heavy influx of fresh water (Anbhazhagan,
1988). The low value of silicate recorded during post-monsoonal season could
be attributed to uptake of silicates by phytoplankton for their biological activity
(Mishra et al., 1993). Higher concentration of
ammonia was observed during monsoon season could be partially due to the death
and subsequent decomposition of phytoplankton and also due to the excretion
of ammonia by planktonic organisms (Segar and Hariharan,
High density of zooplankton recorded in Summer season might be due to the stable
salinity and high phytoplankton population density. The abundance of zooplankton
during Summer season was also reported by Srinivasan and
Santhanam (1991) in pullavazhi backwaters, Karuppasamy
and perumal (2000) in the Pichavaram mangroves, Madhu
et al. (2007) in Cochin backwaters. The recorded high densities might
be due to the relatively stable environment condition, which prevailed during
those seasons and great neritic elements presence from the adjacent sea could
have also contributed to the maximum density of zooplankton. Further, salinity
is the key factor influencing the distribution and abundance of zooplankton
(Padmavati and Goswami, 1996).
The copepod population densities were high and Acartia sp., was dominated
in sub-order calanoids and that of Oithona sp., among cyclopoid was noticed,
the abundance of Oithona sp., was mainly due to its high reproductive
capacity. Similar findings were earlier reported by Santhanam
and Perumal (2003). Many copepod species disappear during monsoon and species
composition also changed, since they are mostly stenohaline (Eswari
and Ramanibai, 2004). During monsoon period heavy flood changed the salinity
and temperature and due to this environmental variation the zooplankton population
density also decreased. Similar observation was earlier made by Padmavati
and Goswami (1996). The important factors which controlled the distribution
of copepods were rainfall, river discharge and decreased phytoplankton abundance
due to increased turbidity (Bijoy Nandan and Abdul Azis,
1994). The meroplanktonic organisms such as veligers of bivalves and gastropod,
copepod nauplii and barnacle nauplii and that of the most common species of
copepods Acartia spinicauda, A, danae, A, erytharea, A. southwelli,
Paracalanus parvus, Oithona brevicornis, O. similis, O. rigida were commonly
found in Ayyampattinam region.
The observed maximum premonsoonal species diversity may be due to the high
zooplankton density that also indicated the stable high salinity values and
phytoplankton density. The low species diversity was observed monsoon season,
which could be attributed to heavy freshwater influx and low salinity (Prasad,
2003). This is supported by the obtained statistically significant values
between diversity and density (r = 0.65). Maximum species richness was recorded
during premonsoon season. During premonsoon season, population density of zooplankton
also increased with increasing species richness (Santhanam
and Perumal, 2003).
Population density, species diversity and species richness values were high
during premonsoon along with high values of evenness index, suggesting the equal
distribution of species during this season (Karuppasamy
and Perumal, 2000). The statistical correlation values of evenness showed
positive correlation with species richness and species diversity. The results
of Analysis of Variance (ANOVA) for the difference in zooplankton distribution
between the stations are significant at 0.05% level.
In the present investigation, the increase or decrease of salinity in the water column exerts either a direct or an indirect effect in the appearance or disappearance of some forms and replacement by others. The indirect effect might be due to the scarcity of food caused by the fluctuations of salinity in the waters ultimately affecting the population abundance of zooplankton.
The collected information is a base line data on the zooplankton distribution and abundance with reference to hydrography and this would form a useful tool for further ecological assessment at Ayyampattinam coast.
The authors are grateful to the Prof. T. Balasubramanian, Director, Faculty of Marine Science and CAS in Marine Biology, Annamalai University, Parangipettai, Tamil Nadu and India for providing the requisite facilities and to the authorities of Sethusamudram Ship Channel Project for providing fellowship to the first author.
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