**3. Results and discussion**

## **3.1 Study site**

The characteristic substrate of the study site in Asry Beach is shown in **Figure 2**. It is an obligate, slightly elevated rocky platform which is often exposed to alternating tide sequences resulting to its periodic submergence and emergence. As part of the public beach, however people prefer the sandy part and spend their leisure time in water for swimming. Hence this area remains undisturbed which promotes massive growth of algae that provides nutrients and venue for ecological and intra-inter-specific interactions [5] among the faunal community of organisms. Based on observation and results of the study on the entire intertidal ecosystem [17] human factor is considerably not a limiting factor for the gastropod assemblage to be abundant in the area. This is in contrast to some research findings that human activities may intensify the exploitation of gastropod species for commercial purposes [11, 14]. Hence the rocky platform of the intertidal zone in this particular area serves as the habitation of the many life forms enduring the harsh environmental condition [1].

#### **3.2 Sampling, identification and field collection**

A total of 16 families composed of 25 genera and 31 species were identified in the rocky shore of Asry Beach from January 2016 to January 2018. The taxonomic

identification, classification and total population of individual gastropod species in the sampled quadrates are presented in **Table 1**. Of the 16 families, *Family Muricidae* has four species which belong to four genera, *Nucella*, *Ocenebra*, *Ocinebrina* and *Scabrotrophon* while *Family Cerithiidae* [8] and *Oliveliidae* [7] has three species each. *Calliostoma selectum* of the *Family Calliostomatidae* has the most


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**3.3 Data analysis**

*3.3.1 Measure of diversity*

*Assemblage of Gastropods in the Rocky Intertidal Zone of Asry Beach, Kingdom...*

number of the gastropods in the rocky intertidal zone having a total of 3841 followed by *Lirobittium attenuatum* of the *Family Cerithiidae* with 471, *Turbonilla* sp. 1 of the *Family Pyramidellidae* [7] with 226, *Cerithiopsis* sp., 211 of the *Family Cerethiopsidae*, and *Calliostoma variegatum*, 203 which is also from *Family Calliostomatidae*. Over-all, the highest number of total species was recorded in 2018 with 2011, a total of 1908 in 2017 while 1624 in 2016. In a 3-year study, a total of 5543 individual species were identified inhabiting the small parcel of the rocky shore of Asry Beach. Samples of gastropods in their natural habitat are shown in **Figure 3**, which include *Turbonilla* sp. (A) of the *Family Pyramidellidae*, *Lirularia olirulata* (B) of the *Family Trochidae*, and a group of *Cerithiopsis* sp. (C) of the *Family Cerethiopsidae* in association with algal community. Various studies on gastropod assemblage showed diversity of gastropods in the intertidal habitats [13–16] similar in this study with the use of diversity indices. However, the types of substrate vary from fine sand coral reef flats [13] and rocky shore beaches [9], including intertidal rocky shores [14, 15] and generally the intertidal zone of mixed substrate [6, 11]. Results of gastropod diversity study in Sombu Beach, Wakatobi, Indonesia showed 13 species of classes of gastropods covering only a month of study however using more transects [13] while a 3 year study of monthly sampling but using only one transect with 31 identified species. Generally, the type of substrate and the length of time for data gathering vary, although both conducted researches utilized the same sampling method. Composition of molluscs was compared in two communities of rocky shore beaches exposed to human activities. Results showed greater abundance and evenness in the site with less human activities [9] which is comparatively different from the claim that human factor considerably exerts no effect on diversity of gastropods in Asry Beach based on the results of monitoring studies [17]. Likewise, the researches being compared used diversity indices in quantitative analysis of data. Some similar researches covered wider spatial distribution of intertidal gastropods [1, 11, 14] although this research covered only a smaller scale on obligate rocky platform. Identified gastropods were taxonomically classified [13, 14] to the lowest level and specific count of species was determined.

Species diversity and evenness are presented in **Table 3**. Results of the Shannon-

Wiener diversity index (H′) and Pielou's evenness index (J') show that species diversity is high (H′ > 4) in the *Family Muricidae* with computed H′ value of 4.19. Evenness is complete (J' = 1) where J' value is 3.81. High species diversity of this group indicates the most number of species (four species) and evenly distributed in the sampled plots of the study site compared to other gastropod families. Generally, the muricids are commonly found in rocky habitat hence these are called rock snails. They are carnivores and predators of sessile animals [18, 19]. Identified gastropod assemblage can adapt to varying environmental conditions such as fluctuation in temperature due to intense solar radiation [1, 6] biotic and abiotic factors [11], substrate condition [10] and wave actions [1, 13]], physical and chemical factors such as temperature [1, 6], salinity, pH and dissolved oxygen (DO) [16] and increase human activities [9, 11]. Specifically in this particular research, aerial temperature was considered as a factor since transect with sampled plots were laid on the elevated rocky habitat (**Figure 1**). Recorded monthly aerial temperature from January 2016 to January 2018 was correlated with the population of gastropod species assemblage (**Table 1**). In some related gastropod diversity studies, temperature in general [16] was considered as limiting factor instead of aerial temperature.

*DOI: http://dx.doi.org/10.5772/intechopen.87772*

#### **Table 1.**

*Gastropod assemblage in the sampled quadrates using belt transect method.*

*Assemblage of Gastropods in the Rocky Intertidal Zone of Asry Beach, Kingdom... DOI: http://dx.doi.org/10.5772/intechopen.87772*

number of the gastropods in the rocky intertidal zone having a total of 3841 followed by *Lirobittium attenuatum* of the *Family Cerithiidae* with 471, *Turbonilla* sp. 1 of the *Family Pyramidellidae* [7] with 226, *Cerithiopsis* sp., 211 of the *Family Cerethiopsidae*, and *Calliostoma variegatum*, 203 which is also from *Family Calliostomatidae*. Over-all, the highest number of total species was recorded in 2018 with 2011, a total of 1908 in 2017 while 1624 in 2016. In a 3-year study, a total of 5543 individual species were identified inhabiting the small parcel of the rocky shore of Asry Beach. Samples of gastropods in their natural habitat are shown in **Figure 3**, which include *Turbonilla* sp. (A) of the *Family Pyramidellidae*, *Lirularia olirulata* (B) of the *Family Trochidae*, and a group of *Cerithiopsis* sp. (C) of the *Family Cerethiopsidae* in association with algal community. Various studies on gastropod assemblage showed diversity of gastropods in the intertidal habitats [13–16] similar in this study with the use of diversity indices. However, the types of substrate vary from fine sand coral reef flats [13] and rocky shore beaches [9], including intertidal rocky shores [14, 15] and generally the intertidal zone of mixed substrate [6, 11]. Results of gastropod diversity study in Sombu Beach, Wakatobi, Indonesia showed 13 species of classes of gastropods covering only a month of study however using more transects [13] while a 3 year study of monthly sampling but using only one transect with 31 identified species. Generally, the type of substrate and the length of time for data gathering vary, although both conducted researches utilized the same sampling method. Composition of molluscs was compared in two communities of rocky shore beaches exposed to human activities. Results showed greater abundance and evenness in the site with less human activities [9] which is comparatively different from the claim that human factor considerably exerts no effect on diversity of gastropods in Asry Beach based on the results of monitoring studies [17]. Likewise, the researches being compared used diversity indices in quantitative analysis of data. Some similar researches covered wider spatial distribution of intertidal gastropods [1, 11, 14] although this research covered only a smaller scale on obligate rocky platform. Identified gastropods were taxonomically classified [13, 14] to the lowest level and specific count of species was determined.

#### **3.3 Data analysis**

*Invertebrates - Ecophysiology and Management*

**Family Species**

identification, classification and total population of individual gastropod species in the sampled quadrates are presented in **Table 1**. Of the 16 families, *Family Muricidae* has four species which belong to four genera, *Nucella*, *Ocenebra*,

species each. *Calliostoma selectum* of the *Family Calliostomatidae* has the most

*Ocinebrina* and *Scabrotrophon* while *Family Cerithiidae* [8] and *Oliveliidae* [7] has three

**Identified gastropods/Taxonomic hierarchy Year Total**

*Volutidae Arctomelon tenrsii*, Dall, 1872 3 3 6 **12** *Columbellidae Astyris aurantiaca*, Dall, 1871 1 2 1 **4** *Batillariidae Batillaria attramentaria*, Sowerby, 1855 3 3 3 **9** *Cerithiidae Bittium vancoverense*, Dall & Bartsch, 1910 4 4 7 **15**

*Oliveliidae Callianax baetica*, Carpenter, 1864 5 7 9 **21**

*Calliostomatidae Calliostoma selectum*, Dillwyn, 1817 1025 1221 1231 **3481**

*Cerethiopsidae Cerithiopsis* sp. 63 71 77 **211** *Pyramidellidae Evalea tenuisculpta*, Carpenter, 1864 37 42 53 **132**

*Turbinidae Homalopoma baculum*, Carpenter, 1864 28 38 42 **109**

*Buccidae Lirabuccinum odirum*, Reeve, 1846 6 8 11 **25**

*Trochidae Lirularia olirulata*, Carpenter, 1864 52 60 67 **179**

*Velutinidae Marsenia thrombica*, Dall, 1871 9 15 9 **33**

*Muricidae Nucella lamellosa*, Gmelin, 1791 3 3 5 **11**

*Epitoniidae Opalia borealis*, Kepe, 1881 7 10 13 **30** *Margeliidae Oepota olividensis*, Carpenter, 1864 1 1 3 **5**

*Borsoniidae Ophiodermelta cacellata*, Carpenter, 1864 1 1 1 **3** Total **1624 1908 2011 5543**

*Gastropod assemblage in the sampled quadrates using belt transect method.*

*Lirobittium attenuatum*, Carpenter, 1864 156 148 167 **471** *Stylidium eschrichtii*, Middendroft, 1849 10 17 21 **48**

*Callianax obiplicata*, Sowerby, 1825 5 7 6 **18** *Callianax pycna*, S. S. Berry, 1925 2 3 7 **12**

*Calliostoma variegatum*, Carpenter, 1864 54 68 81 **203**

*Turbonilla* sp. 1 68 77 81 **226** *Turbonilla* sp. 2 5 7 6 **18**

*Homalopoma luridum*, Dall, 1885 58 62 67 **187**

*Volutharpa ampullarea*, Middendroft, 1848 2 5 5 **12**

*Lirularia succinata*, Carpenter, 1864 3 5 8 **16**

*Velutina velutina*, O. F. Muller, 1776 2 5 3 **10**

*Ocenebra inornata*, Recluz, 1851 2 2 3 **7** *Ocinebrina atropupurea*, Carpenter, 1864 1 4 5 **10** *Scabrotrophon maltzani*, Kobett & Kuster, 1878 1 1 1 **3**

*Oenopota tabulate*, Carpenter, 1864 6 8 8 **22**

2016 2017 2018

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**Table 1.**

Total *Family* **16** Total *Genus* **25** Total *Species* **31**

#### *3.3.1 Measure of diversity*

Species diversity and evenness are presented in **Table 3**. Results of the Shannon-Wiener diversity index (H′) and Pielou's evenness index (J') show that species diversity is high (H′ > 4) in the *Family Muricidae* with computed H′ value of 4.19. Evenness is complete (J' = 1) where J' value is 3.81. High species diversity of this group indicates the most number of species (four species) and evenly distributed in the sampled plots of the study site compared to other gastropod families. Generally, the muricids are commonly found in rocky habitat hence these are called rock snails. They are carnivores and predators of sessile animals [18, 19]. Identified gastropod assemblage can adapt to varying environmental conditions such as fluctuation in temperature due to intense solar radiation [1, 6] biotic and abiotic factors [11], substrate condition [10] and wave actions [1, 13]], physical and chemical factors such as temperature [1, 6], salinity, pH and dissolved oxygen (DO) [16] and increase human activities [9, 11]. Specifically in this particular research, aerial temperature was considered as a factor since transect with sampled plots were laid on the elevated rocky habitat (**Figure 1**). Recorded monthly aerial temperature from January 2016 to January 2018 was correlated with the population of gastropod species assemblage (**Table 1**). In some related gastropod diversity studies, temperature in general [16] was considered as limiting factor instead of aerial temperature.

**Figure 3.** *Samples of gastropods in their natural habitat during the lowest low tide.*

In sampling locations partly submerged in water as in tidal pool [6, 12] coral reef habitat [13] and the littoral zone [14], water temperature was considered a moderating variable. Generally, the various habitats determined the species of gastropods [7] which directly or indirectly affected by the dynamics of the environmental temperatures. The distribution of organisms is non-homogeneous in the intertidal zone which changes based on the biotic and abiotic factors [12]. Species diversity is moderate (2 < H′ < 4) among the *Family Pyramidellidae* (H′ = 3.29; J' = 2.99); *Family Cerithiidae* (H′ = 3.22; J' = 2.92); *Family Oliveliidae* (H′ = 3.12; J' = 2.84); *Family Calliostomatidae* and *Turbinidae* (H′ = 2.19; J' = 1.99) including species

**173**

**Table 2.**

*Assemblage of Gastropods in the Rocky Intertidal Zone of Asry Beach, Kingdom...*

**Identified gastropods/Taxonomic classification Shannon-**

1910*Lirobittium attenuatum*, Carpenter, 1864*Stylidium eschrichtii*, Middendroft,

1864*Callianax obiplicata*, Sowerby, 1825*Callianax pycna*, S. S. Berry, 1925

1817*Calliostoma variegatum*, Carpenter,

1864*Turbonilla* sp. 1*Turbonilla* sp. 2

1864*Homalopoma luridum*, Dall, 1885

1864*Lirularia succinata*, Carpenter, 1864

*Epitoniidae Opalia borealis*, Kepe, 1881 1.07 0.97

*Borsoniidae Ophiodermelta cacellata*, Carpenter, 1864 1.11 1.01 Weighted Mean 2.06 1.88

1864*Oenopota tabulate*, Carpenter, 1864

1846*Volutharpa ampullarea*, Middendroft, 1848

*velutina*, O. F. Muller, 1776

1791*Ocenebra inornata*, Recluz, 1851*Ocinebrina atropupurea*, Carpenter, 1864*Scabrotrophon maltzani*, Kobett &

*Cerethiopsidae Cerithiopsis* sp. 1.10 1.0

*Volutidae Arctomelon ternsii*, Dall, 1872 1.04 0.95 *Columbellidae Astyris aurantiaca*, Dall, 1871 1.04 0.95 *Batillariidae Batillaria attramentaria* Sowerby, 1855 1.11 1.01

**Wiener (H′)**

3.22 2.92

3.13 2.84

2.19 1.99

3.29 2.99

2.19 1.99

2.10 1.91

2.12 1.93

2.08 1.89

4.19 3.81

2.04 1.85

**Species evenness (J')**

of *Family Trochidae*, *Buccidae*, *Velutinidae*, and *Margeliidae* having two to three species. Other species in the *Family Batillariidae*, *Borsoniidae*, *Cerethiopsidae*, *Epitoniidae*, *Volutidae* and *Columbellidae* have low diversity (H′ < 2). Of the 31 species (**Table 1**), three gastropod species have no evenness, *O. borealis* of the *Family Epitoniidae* (J' = 0.97) *A. ternsii* which belong to *Family Volutidae* and *A. aurantiaca of the Family Columbellidae* (J' = 0.95). Over-all, diversity in the rocky habitat of Asry Beach is moderate with the weighted mean of H′ = 2.06 however evenly distributed (J' = 1.88) (**Table 2**). Results imply that the resources specifically food [5] in the sampled rocky habitat supports the assemblage of gastropod species thus

*DOI: http://dx.doi.org/10.5772/intechopen.87772*

maintaining ecological balance in beaches [9].

*Cerithiidae Bittium vancoverense*, Dall & Bartsch,

1849

*Oliveliidae Callianax baetica*, Carpenter,

*Calliostomatidae Calliostoma selectum*, Dillwyn,

1864

*Pyramidellidae Evalea tenuisculpta*, Carpenter,

*Buccidae Lirabuccinum odirum*, Reeve,

*Trochidae Lirularia olirulata*, Carpenter,

*Muricidae Nucella lamellosa*, Gmelin,

*Margeliidae Oepota olividensis*, Carpenter,

*Velutinidae Marsenia thrombica*, Dall, 1871*Velutina* 

Kuster, 1878

*Result of Shannon-Wiener diversity index (H*′*) and Pielou's species evenness (J').*

*Turbinidae Homalopoma baculum*, Carpenter,

*Family Species*

*Assemblage of Gastropods in the Rocky Intertidal Zone of Asry Beach, Kingdom... DOI: http://dx.doi.org/10.5772/intechopen.87772*

of *Family Trochidae*, *Buccidae*, *Velutinidae*, and *Margeliidae* having two to three species. Other species in the *Family Batillariidae*, *Borsoniidae*, *Cerethiopsidae*, *Epitoniidae*, *Volutidae* and *Columbellidae* have low diversity (H′ < 2). Of the 31 species (**Table 1**), three gastropod species have no evenness, *O. borealis* of the *Family Epitoniidae* (J' = 0.97) *A. ternsii* which belong to *Family Volutidae* and *A. aurantiaca of the Family Columbellidae* (J' = 0.95). Over-all, diversity in the rocky habitat of Asry Beach is moderate with the weighted mean of H′ = 2.06 however evenly distributed (J' = 1.88) (**Table 2**). Results imply that the resources specifically food [5] in the sampled rocky habitat supports the assemblage of gastropod species thus maintaining ecological balance in beaches [9].


**Table 2.**

*Result of Shannon-Wiener diversity index (H*′*) and Pielou's species evenness (J').*

*Invertebrates - Ecophysiology and Management*

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**Figure 3.**

In sampling locations partly submerged in water as in tidal pool [6, 12] coral reef habitat [13] and the littoral zone [14], water temperature was considered a moderating variable. Generally, the various habitats determined the species of gastropods [7] which directly or indirectly affected by the dynamics of the environmental temperatures. The distribution of organisms is non-homogeneous in the intertidal zone which changes based on the biotic and abiotic factors [12]. Species diversity is moderate (2 < H′ < 4) among the *Family Pyramidellidae* (H′ = 3.29; J' = 2.99); *Family Cerithiidae* (H′ = 3.22; J' = 2.92); *Family Oliveliidae* (H′ = 3.12; J' = 2.84); *Family* 

*Calliostomatidae* and *Turbinidae* (H′ = 2.19; J' = 1.99) including species

*Samples of gastropods in their natural habitat during the lowest low tide.*
