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PAPER • OPEN ACCESS Diatoms in the rivers of Calamba Occidental,

To cite this article: Astrid L. Sinco and Annielyn D. Tampus 2020 IOP Conf. Ser.: Earth Environ. Sci. 528 012008

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This content was downloaded from IP address 170.106.35.229 on 25/09/2021 at 22:31 ICEFC2019 IOP Publishing IOP Conf. Series: Earth and Environmental Science 528 (2020) 012008 doi:10.1088/1755-1315/528/1/012008

Diatoms in the rivers of Calamba , Philippines

Astrid L. Sinco1 and Annielyn D. Tampus2

1 Biology Department, Xavier University, Cagayan de Oro City, Philippines 2 Marine Biology Department, MSU-Iligan Institute of Technology, Tibanga Iligan City, Philippines

Abstract. Diatoms are good indicators of the environmental integrity of lotic ecosystems. This study aims to identify the genera of diatoms present in the rivers of Calamba, Misamis Occidental, Philippines and their corresponding abundance. Sixteen genera of diatoms were identified in the rivers where the majority of the genera favor intermediate to the high nutrient concentration. The species of Fragilaria and Navicula were most abundant upstream while the species of Amphora was the most abundant downstream. The following genera were present in all the rivers sampled and most of these have high cell densities: Amphora, Cymbella, Epithemia, Fragilaria, Gomphonema, Navicula, and Nitzschia. Based on the assemblage of diatom genera, the rivers sampled at Calamba Misamis Oriental are already showing signs of nutrient enrichment. Using probes to measure the concentrations of nutrients in the rivers can further validate this finding.

1. Introduction The physical and chemical conditions of rivers give cues on the condition of riparian zones, geomorphology of the streambed and the capacity of rivers to support riverine organisms [1]. The aquatic ecosystems also harbor a diversity of organisms including macrophytes, algae, bacteria, invertebrates, and fish which can be used to monitor stream conditions [2]. Calamba is a municipality of Misamis Occidental. Misamis Occidental is bounded on the Northeast by Sea, East by , Southeast by Panguil Bay and West by Zamboanga del Norte and . The municipality of Calamba is mainly an agricultural area where commercial plantation of bananas, papayas, coconuts and cassava are the dominant agricultural products. An evaluation of riverine microorganisms is important since these organisms are affected by alterations in the surrounding habitats [3]. Thus this study focused to determine the genera of diatoms present in the rivers of Calamba, Misamis Occidental, Philippines and its corresponding abundance.

2. Methods There were three sampling sites in Calamba Misamis Occidental specifically located in Langaran, Bunawan, and Dioyo. In each site, downstream, midstream and upstream segments were identified. Global Positioning System (GPS) was used to determine the exact coordinates of the sampling sites. Diatom samples were collected in each location by picking stones (20 cm or greater) from the stream bottom along a 50-meter sampling reach. A 1.5-inch diameter delimiter was placed on the upper surface of each stone to define a 12 cm2 area then a firm-bristled toothbrush was used to dislodge diatoms from the stone surface within the delimiter. The dislodged diatoms were transferred into a sample bottle and fixed with 10% formalin. The sample bottles were labeled according to the sampling site and date. Each

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sample bottle contains a composite of diatom samples from the stones collected in each sampling reach. The diatom samples were cleaned using H2O2 wherein the sample was placed in a beaker added with an equal volume of H2O2. The aliquot was oxidized using a hot water bath. When oxidation was complete, the diatom samples were rinsed with distilled water, centrifuged and the supernatant was siphoned. Rinsing was done five to six times and the mounting medium used is Naphrax. Genera of diatoms were identified under a compound microscope using an oil immersion objective.

Figure 1. Map of Calamba, Misamis Occidental

2 ICEFC2019 IOP Publishing IOP Conf. Series: Earth and Environmental Science 528 (2020) 012008 doi:10.1088/1755-1315/528/1/012008

3. Results and discussion Diatoms are good indicators of the environmental integrity of lotic ecosystems because they are common in most streams and they are at the base of the food chain [4]. Furthermore, diatoms can integrate the effects of multiple environmental stressors over time [5]. Other reasons why diatoms are good indicators of environmental integrity include (a) being readily dispersed and can invade a variety of habitats, (b) being relatively easy to sample and create minimal impact to other organisms during collections, (c) are sensitive to subtle changes in environmental conditions that may not visibly affect other communities or may only affect other communities at greater levels of disturbance [6]. Sixteen genera of diatoms were identified in Calamba Rivers. The relative abundance of diatom genera as shown in table 1 had a variety of diatoms. The upstream segment of the rivers at Langaran and Dioyo showed that species of Fragilaria was the most abundant while the species of Navicula was the most abundant in the river at Bunawan. Species of Amphora was the most abundant in the downstream segment of the river located at Bunawan. Table 1 further showed that among the sampling sites, the species of Achnanthes were found only in the rivers at Bunawan and Langaran while and species of Sellaphora were found only in the river at Langaran.

Table 1. The relative abundance of diatoms in rivers of Calamba, Misamis Occidental (DS-downstream, MS-midstream, and US-upstream; - not observed). River at Langaran River at Bunawan River at Dioyo Diatom Genera DS MS US DS MS US DS US Achnanthes - 1.14 - - 1.79 - - - Amphora 1.33 0.57 2.01 28.63 16.07 3.67 13.17 2.24 Cocconeis 15.33 26.86 14.09 1.71 5.36 1.83 - 11.94 Cymbella 3.33 5.71 9.40 2.56 3.57 8.26 6.59 5.97 Epithemia 2.67 5.14 2.68 0.85 3.57 5.50 5.39 2.24 Fragilaria 32.67 8.57 28.86 14.96 46.43 19.27 16.77 41.04 Frustulia 0.67 - - - - 12.84 8.38 - Gomphonema 8.00 33.71 28.19 24.79 14.29 7.34 16.17 6.72 Navicula 6.00 6.86 2.01 10.26 3.57 24.77 19.16 14.93 Nitzschia 14.67 4.00 10.07 13.25 3.57 12.84 10.78 10.45 Pinnularia 1.33 2.29 0.67 1.28 - 2.75 2.40 0.75 Placoneis 3.33 ------Sellaphora - 2.86 0.67 - - - - - Stauroneis - 1.14 - 0.43 - - 1.20 - Surirella 2.00 - - - - 0.92 - 1.49 Tabularia 8.67 1.14 1.34 1.28 1.79 - - 2.24

In terms of density, Figure 2 showed that in the river located at Langaran, the species of Fragilaria, Cocconeis, Nitzschia, Tabularia, Gomphonema, Navicula, and Cymbella had the highest density. In the river at Bunawan, the species of Amphora, Gomphonema, Fragilaria, Nitzschia, Navicula, Cocconeis, Cymbella and Frustulia had the highest density. In the river at Dioyo, the species of Navicula, Fragilaria, Gomphonema, Amphora, Nitzschia, and Cocconeis had the highest density. It should also be noted that the species of Fragilaria was commonly observed in all sampled rivers of Calamba. The species of Tabularia was only observed in the downstream segment of the river located at Langaran. Analysis of variance was used to test if the densities of diatoms significantly differed among the sampling sites. Results showed that the sampling sites did not differ significantly (p=0.89) in terms of diatom density this indicates that the densities of diatom genera did not vary among the sampling sites.

3 ICEFC2019 IOP Publishing IOP Conf. Series: Earth and Environmental Science 528 (2020) 012008 doi:10.1088/1755-1315/528/1/012008

Figure 2. Diatoms with high densities per site in Calamba (DS=downstream; MS=midstream; US=upstream).

Considering generic richness the river located at Langaran had the highest richness consisting of 13 genera in both downstream and midstream segments (Table 2). The river located at the downstream segment of Dioyo had the highest diversity and equitability while the river located at the midstream segment of Bunwan had the least diversity and equitability. The diversity pattern observed in Calamba Rivers showed that higher diversities characterize the downstream segments of the rivers. This pattern supports the river continuum concept (RCC) wherein downstream area of rivers would have higher diversity compared to upstream areas.

Table 2. Diversity, richness, and evenness of diatom genera in rivers of Calamba, Misamis Occidental (DS-downstream, MS-midstream and US-upstream). Location Richness Diversity (H) Equitability (J)

River at Langaran Downstream 13 2.07 0.81 Midstream 13 1.93 0.75 Upstream 11 1.82 0.76 River at Bunawan Downstream 11 1.83 0.76 Midstream 10 1.71 0.74 Upstream 11 2.08 0.87 River at Dioyo Downstream 10 2.11 0.91 Upstream 11 1.84 0.77

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Cluster analysis was conducted to see which rivers have similar generic composition (Figure 3). Results showed that there are four groups produced from cluster analysis. The rivers with the highest similarity of genera are located at the downstream portion of Langaran and the upstream of Dioyo which in turn is similar to the upstream portion of Langaran. The upstream site at Bunawan, the downstream of Dioyo, and the midstream portion of Bunawan forms another cluster as shown in Figure 2. The midstream site at Langaran and the downstream segment of Bunawan is considered as separate clusters indicating that both rivers have their own unique sets of genera which is different from the other clusters.

Figure 3. The similarity of the rivers sampled for diatoms in Calamba Misamis Oriental using Cluster Analysis (DS=downstream; MS=midstream; US=upstream).

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Figure 4. Diatoms in Calamba and La Libertad Rivers (A= Achnanthes, B= Amphora, C= Cocconeis, D= Cylotella, E= Cymbella, F= Gomphonema, G= Navicula, H= Frustulia, I= Fragilaria, J= Tabularia, K= Sellaphora, L= Placoneis, M= Stauroneis)

It is interesting to note that out of the sixteen (16) genera of diatoms in the sampling sites of Calamba Misamis Occidental, seven genera are indicators of very high nutrient concentrations namely, Amphora, Cymbella, Navicula, Nitzschia, Sellaphora, Stauroneis, and Tabularia (Figure 4). The genera of Amphora, Cymbella, Navicula and Nitzschia had high densities in the rivers located at Bunawan, Dioyo and Langaran. The genera of Cocconeis, Epithemia, Fragilaria, Frustulia, and Pinnularia are adapted to very low to low nutrient concentrations in rivers. The genus Fragilaria had very high densities in all sampling sites.

4. Conclusion Based on the assemblage of diatom genera, the rivers sampled at Calamba Misamis Oriental are already showing signs of nutrient enrichment especially with the presence of the following genera having high cell densities: Amphora, Cymbella, Epithemia, Fragilaria, Gomphonema, Navicula, and Nitzschia. This finding can be validated further by using probes to measure the concentrations of nutrients in the rivers.

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References [1] Harding J C 2009 Stream habitat assessment protocols for wadeable rivers and streams of New Zealand. New Zealand: School of Biological Sciences, University of Canterbury [2] Victoria E 2003 Rapid biassessment methodology for rivers and streams. Australia: EPA [3] Karr J R and Chu E W 1999 Restoring life in running waters - better biological monitoring. Covelo, CA: Island Press [4] Walker C and Pan Y 2006 Using diatom assemblages to assess urban stream conditions. Hydrobiologia 561 179-189 [5] Stevenson R L 2009 Comparing responses of diatom species composition to natural and anthropogenic factors in streams of glaciated ecoregions. Nova Hedwigia 135 1-13

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