Benthic foraminiferal distribution and its ecological studies in a shallow shelf setting off Colachel, Kanyakumari District, Tamil Nadu
Suresh Gandhi M1 *, Rajeshwara Rao2 N, Raja M1 & Suresh N1
1Department of Geology, University of Madras, Guindy Campus, Chennai -600 025, India
2Department of Applied Geology, University of Madras, Guindy Campus, Chennai -600 025, India
*[E-mail: msureshgandhi@gmail.com]
Received 19 December 2014; revised 20 May 2015
Samples were collected at 2 transects from stations at Colachel and Mandaikaddu in water depths ranging 0 to
~20 m. In the present study 109 foraminiferal taxa belong to 56 genera are identified. At Colachel, the total foraminiferal species increase from shallow to intermediate depths (0 to 10 m). Important benthic species of this zone are Amphistegina radiata, Quinqueloculina lamarckiana, Q. seminulum, Q. sulcata Q. elongata, Reussella simplex and Textularia agglutinans. The scatter plot of organic matter (OM) versus living species shows positive correlation. Further, the positive trend of Organic matter Vs carbonate reveals that due to littoral drift, the sediment brought from the shallow shelf region has played a significant role in the contribution of dead species as well as shell fragments. In the study area, some important foraminiferal species which mark significant appearance, disappearance and faunal abundance in tune with their depth trails are helpful for demarcating the zonation of benthic populations.
[Keywords: Benthic foraminifera, Ecology and environment, Colachel, Kanyakumari]
Introduction
Recent benthic foraminifera from marine sediments have long been used for paleo environmental reconstructions. The understanding of the distribution patterns of modern benthic foraminifers and its relation to the environment is very important. The present study area, off Colachel, is a natural harbour located at latitude 8°10′ N and 77°14′ E in the southern part of South India. It is well protected by rocky shores and the Muttam Promontory. This coastal track affected badly by tsunami. Seawater inundation has occurred to the maximum of around ~750 m in Colachel and in the beaches of Kadiapattanam, Mandaikkadu and Vaniakudy the inundation had not exceed 100 m. It is the only beach to suffered maximum destruction in the northwestern coast.
Hence, an attempt has been made in this region using foraminiferal distribution to identify the environmental conditions.
Materials and Methods
The study area off Colachel and Mandaikkadu (Fig. 1) lies between latitudes 80° 04′ and 80o 17′
N and longitudes 77o 32′ and 77o 54′ E in Kanyakumari District.
A total of 18 surface sediment samples were collected off Colachel (11 nos) and Mandakadu (7 nos). Physico-chemical parameters in seawater as temperature and pH were determined onboard (motor launch) immediately after collection.
Salinity was determined by standard titration after Knudsen1. Textural nomenclature was followed after Trefthen’s2, organic carbon content estimated after Walkey-Black3, adopted and modified after Jackson4, and calcium carbonate determination followed by Piper5. Loeblich and Tappan6 have been followed in the present study for foraminiferal classification. The identification of the species is based on comparison with the Catalogue of Foraminifera by Ellis and Messina7 and relevant publications on this subject. Studies specimens reposited in the Department of Geology, University of Madras, Chennai, India.
Results
A total of 109 foraminiferal species belonging to 59 genera from 27 families, have been identified. Among these, 10 are, agglutinated taxa, 34 forms are calcareous, imperforate, porcelaneous, 48 are calcareous, perforate species and 4 planktonic species. The checklist of species
is shown in the Table. 1.
Fig.1.Location map of the study area
Table 1—Checklist of foraminifera in the study area
Ammobaculites exigus T.aura Q. tenagos Pyrgo elongata
Eggerella advena T.palustris Q.undulose costata Reussella atlantica
Calcarina spengleri Edentostomina cultrata Q. sp Fursenkoina pontoni
Spiroplectinella sagittula Adelosina laevigata Pseudomassilina australis Sigmavirgulina tortuosa pirotextularia fistulosa Spiroloculina antillarum Triloculina insignis Nonionoides boueanum
Textularia agglutinans S. communis T. ornata N. elongatum
T.conica S. costifera T. rotunda Nonionellina labrodoricum
T. foliacea S. orbis T. tricarinata Hanzawaia concentrica
Hauerina brady F. marginata T. carinata Pararotalia calcar
M. circularis Globorotalia tumida T. trigonula P. nipponica
M. elongata Globigerina bulloides Rupertianella rupertiana Ammonia beccarii
Quinqueloculina agglutinans Globigerina conglomerata Sorites marginalis A .tepida
Q. costata Bolivina spathulata Monalysidium politum Asterorotalia inflata
Q. elongata B. subspathulata Lagena striata A. trispinosa
Q. ferussaci B. lanceolata L. laeavis Elphidium advenum
Q. kerimbatica B. striatula L. sulcata E. crispum
Q. parkeri Bolivinellina translucens Lagenosolenia sp. E. discoidale
Q. polygona Rectobolivina raphanus Lenticulina limbosa E. incertum
Q. seminulam Loxostomina limbata Laevidentalina communis Assilina ammonoides
Q. sulcata Siphogenerina virgula Fissurina cucullata
Depth/ Species Name 10.0m 7.5m 5.5.m
Living/ Total L T L T L T L T L T L T L T L T L T L T L T L T L T L T L T L T L T L T
Station
1 Acervullina inhaerens 2 2 6 4 2
2 Adelosina laevigata 4 5 6 12 2 14 2 8 2 3
3 Ammonia beccarii 12 2 24 12 54 18 88 3 14 6 28 19 103 4 48 12 112 6 34 2 25 4 24 12 98 16 78 3 45 3 14 22 21
4 Ammonia tepida 1 8 2 46 2 36 6 18 5 56 7 67 3 4 6 12 3 13 2 12 3 2 1 1 6 3
5 Amphistegina radiata 3 46 0 34 23 2 29 3 2
6 Assilina ammonoides 8 48 4 56 7 48 5 73 4 52
7 Ammobaculites exigus 12 4 2 2 1
8 Asteroratila trispinosa 2 6 3 2 5 5
9 Asterorotalia inflata 1 3 1
10 Bolivina lanceolata 3 4 12 3 22 2 17 2 12 3 13 3 12 3 12 2 22 2 14 1 12 1 13 1 15 2 12 2 12 1 12
11 Bolivina subsbathulata 1 2 16 1 5 1 15 2 22 2 15 2 12 1 15 1 4 1 5
12 Bolivina spathulata 2 12 3 18 3 18 2 19 1 14 1 12 1 13 1 12 1 1
13 Bolivinellina translucens 4 3 4 2
14 Brizaline striatula 5 6 3 20 12 4 2 1
15 Calcarina spengleri 4 2 1 1 2 2 2 1 1 1 1
16 Cancris oblanga 2 2 2 30 2 8 1 19 2 19 13 14 1 4 3 1 4
17 Chrysalidinella dimorpha 2 1 1 10 1 1 2
18 Cibicides lobatulus 1 3 3 2 1 3 13 12 2 13 3 14 16 12 12 12 14 1 13 1 13
19 Cibicides refulgins 2 1 1 1 1 1 1 1
20 Cibicides sp. 10
21 Cocoarota madrasensis 12 3 18 1 12 1 14 ` 1 12 1 14 1 4 1 8
22 Cymbalo poretta squammosa 2 4 8 9 8 6 5 12 4 2 1 1 3 1
23 Cymbaloporetta brady 12 11 9 7 6 5 3
24 Discorbinella bertheloti 2 3 4 2 10 10 1 2 3 2 1 2 2 1 11 2 1
25 Edentostomina cultrata 1 2 7 6 5 5 4 3 3 3 2 1 1 1 1
26 Eggerella advena 3 2 1 1
27 Elphidium advenum 1 3 1 5 2 19 1 4 1 8 1 9 1 10 1 3 1 3 10 2 1
28 Elphidium botaniensis 2 1 1 2
29 Elphidium crispum 0 9 4 12 9 37 2 14 1 18 2 12 1 9 1 5 2 19 3 22 1 4 1 9 1 4 2 12 3 5 2 9 2 8 1 9
30 Elphidium discoidale 3 4 8 8 9 0 12 3 18 3 19 2 16 2 19 4 17 9 7 8 5 12
31 Elphidium incertum 4 2 1 4 5 9 3 8 8 4 4
32 Elphidium limbatum 2 3
33 Elphidium norvangi 2 7 8 1 2 3 2
34 Eponides repandus 4 19 19 14 23 28 19 11 12 14 44 2 1 1
35 Fissurina cucullata 3 12 20 1 3
36 Fissurina marginata 3 1 3 10
37 Fursenkoina pontoni 5 3
38 Nonionoides boueanum 8 12 18 19 4 18 2 22 9 34 2 19 3 14 2 18 3 21 1 7 2 12 3 2
39 Nonionella grateloup 3 17 12 14 4 15 1
40 Nonionella stella 2 6 3 12 1 8 3 7 2 7 1 4 1 9 3 8 1 12 1 5 5
41 Floriius labradoricum 4 3 48 9 73 2 18 2 29 1 18 3 18 2 7
42 Globigerina sp. 2 1
43 Globigerinina bulloides 4 22 4 46 7 45 2 36 1 12 18 2 12 5 28 3 32 2 12 1 14 19 12
44 Globigerinina conglomerata 4 1 6 2 3 1 6 4 2 1 1 5
45 Globorotalia tumida 3 4 2 1 2 4 7 0
46 Globorotalia menardii 2 1 2
3.0m
Off Colachel-1 Off Colachel-2 Off Mandakadu
0.5 m 2.5 m 4.0m 6.0m 10.0m 14.5 m 18.0m 20.0m 19.5 m 18.4m 17.8m 17.0m 15.0m Table.2. Distirbution of Foraminifera Off Colachel and Mandakadu
12.0m
Out of the 18 sediment samples that were collected from off Colachel and Mandakadu, 32 living foraminiferal species have been observed (Table.2). Sand is deposited all along the coast with silty sands at comparatively greater depths.
Among the species identified, Ammonia beccarri, A. tepida, Elphidium crispum, E. advenum and Rosalina globularis show higher abundance at all stations, barring one or two, followed by A.
dentata. The third species assemblage of abundance is represented by Q. seminulum, Elphidium crispum, Cocoarota madrasensis, Nonionellina labradoricum, Hanzawaia concentrica,Pararotalia calcar, P.
nipponoica and Q. polygona at all the stations.
Some species such as Reophax comprima, Massilina sp., Brizalina striatula and Reussella simplex are more abundant at greater depths, having an affinity for substrate with higher silt content and relatively deeper waters. Similar distribution of Ammonia was reported in the Andaman Sea8. This suggests that Ammonia is a stress-tolerant taxon and could dominate highly stressed environments.
Depth/ Species Name 10.0m 7.5m 5.5.m
Living/ Total L T L T L T L T L T L T L T L T L T L T L T L T L T L T L T L T L T L T
Station
52 Lagena laevis 4 3 8 12 27 3 2 1 1 2 1 1
53 Lagena solenia 4 3 8 12 27 3 2 1 1 2 1 1
54 Lagena striata 16 15 3 5 5 7 8 5 4 3 3 1
55 Legina sulcata 1 1
56 Lenticulina limbosa 2 2
57 Laevindentalina communis 3 2 1 2 2 1
58 Loxostomina limbatum 4 2 3 1 2 1 2 3 2 3 1 1 1 2 1
59 Miliolinella elongata 1 3 1 1 10 1 1
60 Miliolinella circularis 2 4 3 2 1 3 3 12 3 2 3 3 2
61 Monalysidium politum 0 10 10 1 23 1 3 4
62 Nonionoides elongatum 0 3 19 2 18 1 30 2 19 2 18 4 36 7 43 2 17 2 19 2 11 1 18 2
63 Operculina granulosa 2 2 3 3 2
64 Pararotalia calcar 4 4 28 9 18 3 17 3 34 2 28 2 14 2 17 3 19 21 98 3 23 2 23 3 21 6 4 3 2 12 2 9
65 Pararotalia nipponica 3 34 18 37 4 34 6 89 4 59 2 28 1 3 1 2 3 38 2 12 3 32 2 24 2 24 2 13 3 24 2 18 3 48 2 24
66 Planorbu linella larvata 2 3 3 4 5 2 2 1 2 1
67 Pseudo massilina australis 2 3 2 1
68 Pseudoeponides paucilaculata 1 1 2
69 Pseudotriloculina oblonga 2 3 0 3 1 2 2 2 2 2
70 Pyrogoelongata 2 2 12 4 3 2 2
71 Quenqueloculina agglutinans 2 12 3 24 4 14 6 23 0 12 18 0 28 2 10 12 1 3 10 2 2
72 Quenqueloculina ferrusaci 4 3 2
73 Quenqueloculina lamarckiana 3 19 2 78 2 43 9 28 10 80 4 48 9 29 3 24 4 102 2 12 5 9 17 3 19 4 29 2 5 45 2 34
74 Quenqueloculina parkeri 2 3 2 4 3 2 4 2 1 3 1
75 Quenqueloculina polygona 39 2 24 9 37 9 24 4 48 2 34 3 28 1 18 2 24 9 34 9 48 3 34 3 5 5 4 12 24
76 Quenqueloculina seminulum 3 32 7 45 3 4 6 3 25 2 18 3 19 3 19 2 10 3 43 9 54 3 56 13 43 4 76 4 25 4 25 2 43
77 Quenqueloculina SP 1 3 1 3 1
78 Quenqueloculina tenagos 2 1 1 2 1 3 1 1 1
79 Quenqueloculina undulose costata 2 2 1 1 1 12 1 3 1 1 3 1 1
80 Quinqueloculina costata 2 3 4 2 3 3 1 4 1 4 1 1
81 Quinqueloculina elongata 2 12 14 45 56 3 2 45 3 23 12
82 Quinqueloculina kerimbatica 2 3 3 4 4
83 Quinqueloculina sulcata 3 3 4 3
84 Rectobolivina raphanus 3 38 3 24 2 23 9 19 0 45 12 3 3 5 8 2 16 2 18 2 34
85 Reussella atlantica 2 12 24 25 1 4 18 42
86 Rosalina globularis 2 23 4 39 3 48 9 67 4 56 23 129 2 34 4 23 9 87 4 28 4 29 8 21 8 20 3 49 2 78 2 89 2 108 8 43
87 Rotorboides granulosum 2 2 2 2 2
88 Rupertianella rupertiana 8 12 24 12 4 9
89 Sorites marginaluis 2 2 6 2
90 Sigmavirgulina tortuosa 3 2 2 8 2 2 2 3 4 2 1 2 2 4
91 Siphogenerina virgula 2 3 2 6 2 12 28 34 24 3 3 4 8
92 Spirloculina orbis 4 2 2 4 2 12 4 7 9 3 9 2
93 Spiroloculina antillarum 2 2 3 2 1
94 Spiroloculina communis 8 12 5 6 4 4 34 2 38 4 23 3 9 1 8 4 5 8
95 Spiroloculina costifera 4 3 2 1 1 2 1
96 Spiroplectinella sagittula 2 1
97 Spirotextularia fistulosa 2 3
98 Textularia agglutinans 18 76 48 37 18 2 98 12 4 3 2 9 9 4 8 2 12 32 34
99 Textularia aura 2 30 2 2 2 3 1 2 3 3 9 4 2
100 Textularia conica 2 3 2 2 2 1 2 20 1 3 2
101 Textularia foliacea 2 2 2 2 2 2
102 Textularia palustris 4 4 3 2 2 2 2 2
103 Triloculina carinata 4 3 2 2
104 Triloculina insignis 8 1 4 2 12 4 24 1 12 1 9 2 23 2 5 2 2 1 1 2
105 Triloculina ornata 2 2 3 2 2 2 3 3 3
106 Triloculina rotunda 12 2 24 3 4 23 32 3 40 4 2 12 4 34 3 24 2 30 2 3 4
107 Triloculina tricarinata 2 4 3 2 2 2 1 2 2 2 3 2 3 2 3 1
108 Triloculina trigonula 12 18 19 2 17 3 9 9 3 4 2 19 3 14 1 13 14 12
109 Trochammina inflata 2 2 1
TOTAL 21 391 66 693 80 671 109 706 64 810 95 1004 86 825 50 704 70 888 85 654 49 561 62 609 53 690 63 586 32 588 28 499 26 559 19 380
Individual species 5 46 19 42 18 46 23 46 21 50 23 56 24 61 21 66 21 55 16 55 16 52 19 60 16 65 18 67 10 59 14 62 11 56 7 41
3.0m 19.5 m 18.4m 17.8m 17.0m 15.0m 12.0m
0.5 m 2.5 m 4.0m 6.0m 10.0m 14.5 m 18.0m 20.0m
Off Colachel-1 Off Colachel-2 Off Mandakadu
The following species are reported for the first time in the study area: Textularia palustris, Bolivina lanceolata, Bolivina subspathulata, Bolivinellina translucens, Calcarina spengleri, Elphidium botaniensis, Floriius grateloup, Globigerinina conglomerate, Lagena solenia, Quenqueloculina ferrusaci, Calcarina spengleri and Cibicidus refulgins.
Ecology of foraminifera
The results of various ecological parameters and ratios of living/dead species are presented in Table 3. Not show much variation in temperature at different depths is noticed. (35o to 36o C) and salinity do not shows much variation. In the study region, sand is dominant in several stations, particularly up to 10 m depth. Silty sand are distributed in the deeper depths. Living foraminiferal populations are more abundant in the silty sand. Organic matter content ranges from0.12 to 2.12% (Fig.3). Calcium carbonate content varies from 8.5 to 17.34% off Colachel (Fig. 4), and from 7.28% to 14.32% off Mandakadu has been observed (Fig. 5). The bathymetry chart is shown in Fig.5a. Trend of positive correlation between organic matter vs.
calcium carbonate (Fig. 6) reveals that littoral drifting of sediment brought from the shallow shelf region has played a vital role in the contribution of dead species as well as calcareous shell fragments. The calcium carbonate content is higher at deeper depths. Other ecological parameters generally exhibit positive correlations with living species (Fig. 7).
Discussion
The principal genera restricted to this area include Amphistegina, Reussella, Elphidium, and Brizalina The less dominations are Rectobolivina, Quinqueloculina, Spiroloculina and Textularia. A.
beccarii is a dominant species in the shelf region.
It is evident from Table. 2 that the overall dominance of A. beccarii, which is a cosmopolitan species with records world over9, and the associated taxa constituting the assemblages from these area suggest a nearshore inter-tidal environment possibly connected with the Arabian Sea. Presence of few tests of planktonic species such as Globigerina bulloides and
Globorotalia tumida, suggests that should have drifted here due to tidal current action; both are essentially marine taxa and hence support the marine connection.
Fig.5a. Bathymetry chart of the study area (after Hentry et al25)
Conclusion
The A total of 109 foraminiferal taxa belonging to present area, it may be observed that organic matter and calcium carbonate are the major controlling factors for the thriving of foraminifera fauna throughout the year. The following species are reported first time in the study area: T.
palustris, Bolivina lanceolata, B. subspathulata, Bolivinellina translucens, Calcarina spengleri, E.botaniensis, Nonionoides grateloupi, Globigerina conglomerata, Lagenosolenia sp., Pseudotriloculina oblonga, Pyrgo elongata,
Table 3 Results of ecological parameters of the study area – off Colachel and Mandaikkadu
S. No. Depth in m
Salinity
(ppt) CaCO3 (%) OM (%)
Sand (%)
Silt (%)
Clay (%)
Total.
Population (number)
Living ( %)
Dead (%)
Sediment type
C1 0.5 33.3 8.5 0.12 73.2 19.3 7.5 391 5.37 94.63 Sand
C2 2.5 34.3 10.2 0.48 47.1 48.4 4.5 693 9.52 90.48 Sand
C3 4.0 35.9 10.2 1.24 94.5 4 1.5 671 11.92 88.08 Sand
C4 6.0 35.64 17.34 1.64 82.2 10.3 7.5 706 15.43 84.57 Sand
C5 10.0 35 18 2.6 72.7 25.4 1.9 810 7.90 92.10 Silty sand
C6 14.5 37.4 18.3 2.49 50.7 47.3 2 1004 9.46 90.54 Silt
C7 17.8 35.5 10.4 0.13 82.3 10.2 7.5 561 8.73 91.27 Silt
C8 18.0 37.3 17.4 1.33 73.9 25.1 1 825 10.42 89.58 Silty sand
C9 18.4 35.9 12.3 2.54 75.2 22.3 2.5 654 12.9 87.1 Silty sand
C10 19.5 35.33 18.48 2.12 71.1 24.5 4.4 888 7.8 92.12 Silty sand
C11 20.0 36.3 18.1 1.11 92.1 7.4 0.5 704 7.10 92.90 Silty sand
M12 17.0 36.6 14.3 2.1 58.4 40.1 1.5 609 10.18 89.82 Silt
M13 15.0 36.68 14.32 0.14 65.7 33.3 1 690 7.68 92.32 Silty sand
M14 12.0 35.7 12.1 0.25 73.1 24.9 2 586 10.75 89.25 Siltysand
M15 10.0 36.28 9.48 0.34 98.2 1.8 1 588 5.4 94.56 Sand
M16 7.5 36.12 7.28 0.29 98 1.5 0.5 499 5.61 94.39 Sand
M17 5.5 36.22 9.52 0.54 94.1 1.9 4 559 4.65 95.35 Sand
M18 3.0 36.12 10.22 0.12 94.9 2.1 3 380 5 95 Sand
Pseudoeponoides pauciloculata, Quinqueloculina ferussaci, Spirotextularia fistulosa, Chrysalidinella dimorpha, Calcarina spengleri and Cibicidus refulgins. Total population are more in Colachel than Mandakadu. Based on foraminiferal distribution, the study area off Colachel and Mandakadu is characteristic of shallow shelf marine and tropical environmental conditions.
Acknowledgement
The first author thanks the Professor and Head, Department of Geology, University of Madras for grant permission to carry out this work and providing lab facilities.
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