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AIMS Environmental Science, 10(1): 82–92.
DOI: 10.3934/environsci.2023005
Received: 15 June 2022
Revised: 01 November 2022
Accepted: 02 November 2022
Published: 03 January 2023
http://www.aimspress.com/journal/environmental
Research article
A Study of Infaunal Abundance, Diversity and Distribution in
Chettuva Mangrove, Kerala, India
Rukhsana Kokkadan1,*, Resha Neznin1, Praseeja Cheruparambath2, Jerisa Cabilao1and
Salma Albouchi1
1Nautica Environmental Associates LLC, Abu Dhabi, United Arab Emirates
2Department of Zoology, SN College, Alathur, Kerala, India
* Correspondence: Email: rukhsanaktkl@gmail.com; Tel: +919539478606.
Abstract: This study investigates an account on the diversity and abundance of benthic infauna of
Chettuva mangrove in Kerala. Marine benthic infaunal species are an important factor in marine
ecosystems and play a chief ecological function in the mangrove ecosystem. This research article
gives an overview of infaunal diversity associated with eight sites of Chettuva mangrove. The
present study revealed that infaunal species are significantly moderate within this mangrove
ecosystem.
Keywords: Polychaetes; infauna; mangrove; population density; statistical analysis
1. Introduction
Mangroves are a precise coastal ecosystem contributing as a wealthy store of resident
biodiversity. The diversity of the benthic infauna is largely underestimated and must undergo regular
revision in order to detect and monitor changes of benthic communities within the area.
The benthic communities constitute a dominant component that supports habitat productivity to
a greater extent. Due to this, the species composition may negatively affect the resident community
and consequently impact trophic relationships within these communities as a result of any activity
exerted, causing a change for sediment features [1,2]. Zainal et al. and Ali et al. pointed out that the
macrobenthic faunal diversity around the Huwar islands [3,4] and Bahrain are very important in
ecosystem balancing. Other regions, such as Europe [5,6], North America [7,8] and South Africa,
have produced monographs for faunal identification [9]. However, most of the benthic faunal
communities have not yet been thoroughly explored in India.
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Kerala is gifted with a long coastal line and extensive estuaries. Estuarine water contains a rich
supply of nutrients. No comprehensive study has been done so far on benthic infaunal biodiversity
and abundance in this Chettuva mangrove area.
2. Material and methods
2.1. Collection of water and sediment samples
The present study was designed to characterize the benthic infauna community of eight different
sites in Chettuva mangrove, Kerala, as seen in Figure 1. Biological samples from each station, three
replicate samples, were collected using benthic grab sampler. The procedure adopted for sampling
was following the method of Mackie [10]. After collecting the samples, they were emptied into a
plastic tray. The larger organisms were handpicked (extracted) immediately from the sediments and
then sieved through 0.5 mm mesh screen. The organisms retained by the sieve were placed in a
labelled container and fixed in 5%–7% formalin. Subsequently, the organisms were stained with
Rose Bengal solution (0.1 g in 100 ml of distilled water) for greater visibility during sorting. All the
species were sorted, enumerated and identified to the advanced possible level with the consultation
of available literature. The works of Fauvel and Day and http://www.marinespecies.org/polychaeta/
were referred for identification [11].
Figure 1. A Chettuva Mangrove map showing eight different sites of collection.
2.2. Statistical analyses
Statistical software was used to analyze the data obtained from different sites [12]. This was
done using various statistical methods, such as univariate, multivariate and graphical/distributional
methods. Biodiversity indices were calculated for the infaunal community, which included diversity
index (H’) using the method of Shannon-Wiener’s [13] formula, species richness (d) using the
Margalef [14] formula and species evenness (J’) using the Pielou [15] formula. Similarities (or
dissimilarities) between sites were obtained showing the interrelationships of all through an MDS
plot (non-metric Multi-Dimensional Scaling) [16,17]. Cluster analysis was also done to calculate the
similarities. All the various statistical methodologies and calculations were obtained through the
AIMS Environmental Science Volume 10, Issue 1, 82–92.
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software PRIMER V7 (Plymouth Routines in Multivariate Ecological Research) developed by
Plymouth Marine Laboratory.
3. Results
3.1. Species Composition in Chettuva Mangrove
A total of 339 organisms were identified from eight samples, spanning 40 taxa from four phyla
(Tables 1 & 2), representing an average of 42 specimens per sample. The species composition by
phylum within the Chettuva Mangrove area was predominated by annelids with 72.27% (Figure 2).
Arthropods formed the second most important group, represented by 15.93%. Mollusca constituted
9.73%, and the fourth important group was the Echinodermata, which comprised of 2.06%. Annelids
composed the majority of the infaunal species composition (Table 1).
Figure 2. Infauna species composition by phylum level in the Chettuva Mangrove area.
Figure 3: Total number of individuals per site.
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Among all the eight stations, Site 7 is the most abundant and diverse, with 55 individuals across
19 taxa. Capitellidae was the most numerous family, indicating a clear dominance. Samples with
common abundant taxa are presented in Figure 3. Within the polychaetes, Capitellidae, Opheliidae,
Spionidae and Terebellidae were found to be the most recurring species in the samples collected
within this mangrove ecosystem. With respect to arthropods, Anoplodactylus sp. and Apseudidae
were the most abundant species.
Table 1. Taxonomic breakdown of infauna in the Chettuva Mangrove area.
Phylum
Number of Taxa
Relative abundance (%)
Annelida
22
72.27
Arthropoda
13
15.93
Mollusca
4
9.73
Echinodermata
1
2.06
Total
40
100
Figure 4.Branchiostoma lanceolatum, Terebellidae, Capitellidae, Anoplodactylus sp.,
Sabellidae, and Lumbrineridae.
3.2. Dominance
Figure 5 represents the k-dominance curves for each station at each area. These plots illustrate
the cumulative abundance of infauna plotted against the species rank. The curves are formulated
from both a richness measure (species rank) and an evenness measure (% cumulative dominance).
AIMS Environmental Science Volume 10, Issue 1, 82–92.
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Figure 5. Dominance plots of benthic Infaunal taxa in the Chettuva Mangrove area.
Figure 6. Biodiversity indices of infaunal benthic community in the Chettuva Mangrove area.
AIMS Environmental Science Volume 10, Issue 1, 82–92.
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Figure 7. Dendrogram of benthic infaunal communities by site, based on Bray-Curtis similarity.
Figure 8: MDS Plot of benthic infaunal communities by site, based on Bray-Curtis
similarity.
The results of the dendrogram show that species from these eight sites were grouped to two
major categories (Figure 7). Among these sites, site 4, site 6, and site 7 form a separate group while
all other sites are branched to from a major group.
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Table 2. Infaunal taxa and its distribution in the Chettuva Mangrove area.
Taxon
SITE 1
SITE 2
SITE 3
SITE 4
SITE 5
SITE 6
SITE 7
SITE 8
Golfingia sp.
-
4
1
-
-
-
1
4
Sipunculidae
-
1
-
2
-
1
-
-
Phascolosoma sp.
-
1
1
-
1
-
-
-
Phyllodocidae
1
-
1
-
-
1
-
-
Nephtyidae
-
-
-
-
-
1
3
-
Syllidae
1
2
-
-
3
-
5
-
Nereididae
-
-
2
-
-
4
-
1
Sigalionidae
-
2
-
3
-
-
-
-
Polynoidae
1
-
-
-
1
-
-
-
Glyceridae
2
-
-
1
3
-
-
-
Maldanidae
-
1
-
-
-
-
-
-
Lumbrineridae
2
1
-
5
1
1
3
2
Opheliidae
1
2
3
1
5
9
2
1
Spionidae
1
-
10
9
2
1
-
1
Capitellidae
20
14
5
6
5
4
8
6
Magelonidae
-
-
-
-
-
-
-
1
Orbiniidae
1
8
-
-
1
3
5
-
Terebellidae
1
1
3
2
1
4
2
8
Flabelligeridae
-
-
-
-
-
-
-
-
Cirratulidae
1
-
-
-
-
1
-
-
Amphinomidae
-
-
2
-
-
-
-
-
Sabellidae
3
1
-
4
1
2
1
1
Anoplodactylus sp.
2
4
1
-
5
1
6
1
Hyalidae
-
1
-
-
-
-
1
-
Melitidae
-
-
-
3
-
-
4
-
Isaeidae
-
-
-
-
-
-
-
1
Ampeliscidae
-
-
-
-
-
-
1
1
Urothoe brevicornis
-
-
-
-
-
-
2
-
Leptanthuridae
-
-
-
-
-
-
-
1
Accalathura borradailei
-
-
-
-
-
1
-
-
Cirolanidae
-
-
-
-
-
-
-
-
Bodotriidae
-
-
-
-
-
-
2
-
Paranebalia sp.
-
-
-
-
-
-
1
-
Apseudidae
-
-
-
8
-
1
5
-
Paratanaidae
-
-
-
-
-
-
1
-
Amphiuridae
1
1
1
1
1
-
-
2
Ancillariidae
-
1
1
-
4
2
1
3
Pteriidae
-
-
-
-
1
-
-
-
Veneridae
-
-
-
-
-
3
-
1
Tellinidae
1
3
6
-
3
1
1
1
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89
Table 3 shows the total abundance per site, number of species and their diversity indices;
Margalef species richness, Pielou species evenness and the Shannon-Weiner diversity index. Graphs
of the biodiversity indices by site can be seen in Figure 6.
The three indices provide an indication of the diversity of each of the samples based on the
number of species, number of individuals and the distribution of individuals between species. A
more settled community will generally have a greater number of species with individuals spread
more evenly between them, while a stressed or recovering community will tend to be numerically
dominated by a small number of species and have fewer species overall.
Margalef species richness index (d) is heavily influenced by the overall number of species
measured, though it makes a slight allowance for the number of individuals. Higher values indicate a
greater number of species per individual. Margalef species richness index (d), values are ranged
between 2.89 and 4.74 showing reasonably moderate to high richness. Pielou’s species evenness
index (J’) reflects the level of spread of the individuals between the species and lies between 0
(uneven) and 1 (even). The Shannon-Weiner diversity index (H’) lies between 1.94 to 2.75,
indicating an average diversity. The total number of species and individuals present was influenced
by salinity regimes, sediment types, organic content food availability [18]. etc. Overall, the range of
species present in all samples combined suggests a moderately high level of diversity [19–22].
Multivariate analyses were conducted to investigate resemblances in the infaunal assemblages
between sites across the study area (Clarke and Gorley). A Bray-Curtis (BC) similarity matrix was
used to calculate the percentage similarity between all infaunal sites based on all the species present
and their abundances. The samples from each site were summed so that the focus of the analysis was
on similarities and differences between locations. To ensure better representation for
presence/absence of taxa rather than the analysis being dominated by the most numerous species, a
fourth-root transformation was applied.
Table 3. Infaunal abundance and univariate diversity indices of all sites.
Site ID
No. of Taxa (s)
No. of
Individuals (n)
Margalef Species
Richness (d)
Pielou Species
Evenness (J')
Shannon-Weiner Diversity
(loge)(H')
SITE 1
15
39
3.82
0.72
1.94
SITE 2
17
48
4.13
0.84
2.37
SITE 3
13
37
3.32
0.87
2.23
SITE 4
12
45
2.89
0.91
2.25
SITE 5
16
38
4.12
0.92
2.56
SITE 6
18
41
4.58
0.90
2.60
SITE 7
20
55
4.74
0.92
2.75
SITE 8
17
36
4.47
0.88
2.50
Average by site
16
42
4.01
0.87
2.40
To assist with visualizing relationships between sites, the BC values have been displayed as a
dendrogram (group average), in which sites where the communities are more comparable (i.e., have
a higher percentage similarity value) split from one another further down the diagram.
AIMS Environmental Science Volume 10, Issue 1, 82–92.
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Table 4:Similarity Percentage of sites
SITE 1
SITE 2
SITE 3
SITE 4
SITE 5
SITE 6
SITE 7
SITE 8
SITE 1
-
-
-
-
-
-
-
-
SITE 2
59.601
-
-
-
-
-
-
-
SITE 3
51.726
55.286
-
-
-
-
-
-
SITE 4
55.143
48.329
40.422
-
-
-
-
-
SITE 5
76.999
69.116
59.144
49.716
-
-
-
-
SITE 6
61.097
52.862
55.576
47.677
55.462
-
-
-
SITE 7
48.443
62.275
38.993
43.931
52.765
53.200
-
-
SITE 8
53.663
55.334
61.420
45.064
56.319
59.580
49.866
-
The BC values are also used to create Multi-Dimensional Scaling plots (MDS), where sites
which have similar assemblages are plotted closer together, while those that are more dissimilar are
plotted further apart. Fig. 8 shows an MDS plot for the Bray-Curtis matrix (fourth rooted data), with
colored symbols indicating the transect type and a line added to show the 25% similarity level to
assist with interpretation.
4. Discussion and conclusions
In this study, polychaetes were found to be the predominating phylum, playing a very important
role in the recycling of organic materials within the mangroves. Their biomass creates the energy
needed for the survival of this ecosystem, fueling aquatic benthic feeders. Bandekar et al. [23] stated
that families like Nereidae, Nephthydae, Onuphidae, Eunicidae, Spoinidae, Maladanidae, Sabellidae,
etc. are the major biomass producing annelids which form as an important food source for fishes and
prawns. Similarly, bivalves provide stability to soil inhabitants and their diversity and species
abundance.
The infaunal species found in all the sites occupy varied benthic habitats, such as, sandy, muddy
and even seagrasses, indicating an adaptive feature for survival, especially among polychaetes.
However, not many studies have been conducted within the Chettuva mangroves regarding infaunal
diversity to impose an assertive conclusion on this.
Although that may be the case, similar studies in other mangrove fields like Bandekar et al. in
Karwar Mangrove and Sarkar et al. [24] in Sunderban Biosphere Reserve Mangroves, have
concluded that polychaetes carry certain features that help in the adaptation for survival. They are
known to secrete mucus protecting themselves within peculiar habitats.
Several factors play a role causing a change in infaunal diversity and abundance, like
competition with epifauna, predation by epifauna, poor quality of food and chemical defense by
mangroves [25–27]. Seasons affect the diversity and density mostly due to salinity, water and
sediment quality, inundation and waterlogging [28].
Acknowledgments
The authors would like to thank Mr. Veryan Pappin (Nautica Environmental Associates LLC)
for the support offered to complete this research.
Conflict of interest
The authors declare no conflict of interest.
AIMS Environmental Science Volume 10, Issue 1, 82–92.
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