The Epipelic Diatom Community at the Downstream Rivers of Torong, Galeh and Legi, Semarang (Indonesia)

Submitted by: Nina Desianti (Supervise by Tri Retnaningsih Soeprobowati and Murningsih)

ABSTRACT

The Torong, Galeh and Legi rivers are 3 out of 17 inlets of Rawa Pening Lake, which have varied of sedimentation potencies: from the lowest (77.73 ton/ha/yr.) to the very high (369.63 ton/ha/yr.). Those differences may induce the different of the relative abundance, diversity, evenness and similarity of epipelic diatom species. The result of the research was expected to be database for the watershed monitoring related to the river sedimentation. Samples were taken on July 2004 at the downstream of Torong, Galeh and Legi rivers in 3 sampling site based on Justified Random sampling method. Altogether, 148 species were found: 141 species are Pennatophycidae diatoms and only 7 species are Centrophycidae diatoms. The species relative abundance was low and only 7 dominant species were found (Melosira varians, Cymbella tumida, Diploneis smithii, Meridion circulare, Selaphora sp., and Synedra ulna). The total number of individuals and the diversity index of epipelic diatom species of Legi downstream, which has the highest sedimentation potencies, was a little bit higher. However, the epipelic diatom similarity index of Torong, Galeh and Legi downstream were relatively high. Keywords: epipelic diatom, sedimentation INTRODUCTION Diatoms are photosynthesizing microalgae belonging into the division Bacillariophyta. The chloroplast in diatom containing pigments such as chlorophyll a, chlorophyll c and dominated by fucoxanthin and carotenoid that give golden-brown colour. The unique feature of diatom cell is that they are encased within siliceous cell wall with beautiful ornamentation called frustula. The cell wall form a box that is constructed of two halves that fit together, one inside the other called valves and they are joined together by siliceous girdle bands element.

Based on the habitat, diatoms can be classified into two groups, planktonic and benthic. Planktonic diatoms are floating algae in the water coloumn, whereas benthic diatoms are associated with substrates. Benthic diatoms can be divided into epilithic, epiphytic and epipelic diatoms. Epilitic diatoms growing attached to rock surface, epiphytic diatoms growing attached to other plants, while epipelic diatom growing on sediment (Hauer & Lamberti, 1996).

Diatom is a good bioindicator of environmental condition in rivers and streams. The advantages using diatom as bioindicator is because of diatom is widely distributed, abundant, has a short life cycles, a primer producer and has important role in the food chains. Diatom also very species rich, with each species having different environmental preferences, there are sensitive species and tolerant species to environmental changes. Previous diatom study by Soeprobowati (2001) has showed that epipelic diatom could reflect the environmental changes of the lotic or streams ecosystem.

Diatom study of epipelic diatom community, based on sediment cores from Rawapening Lake inlets, provide an opportunity for examining the impact of natural and human-induced changes in the river imply sediment accumulation on stream

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ecosystem. There have been numerous study in Rawapening Lake, which have focused only on individual Lake, e.g. the composition of diatom epipelic community in Rawapening Lake (Soeprobowati, et.al., 2004); comparison of diatom epiphytic community on Ludwigia sp., Pistia stratiotes, Echinochloa sp. and Eichhornia crassipes roots in Rawapening Lake (Kusnawati, 2005). However, there was only few study on Rawapening Lake inlets. Rawapening Lake is located in Salatiga, Central Java, Indonesia. Rawapening Lake collects water from 17 inlets and only has one outflow across Tuntang river as an outlet. Rawapening Lake has a quite high sediment accumulation rate, averaged 778.93 ton yr-1 and was predicted will be drained out by the year of 2011. Erosion and sedimentation of the Rawapening Lake inlets has contributed to the lake drought. Legi river has the highest sedimentation potencies at 369.63 ton ha-1 yr-1, Galeh river sedimentation potencies was at 166.16 ton ha-1 yr-1, Torong (77.33 ton ha-1 yr-1), Panjang (50.82 ton ha-1 yr-1), Parat (238.3 ton ha-1 yr-1), Sraten (197.79 ton ha-1 yr-1), Rengas (21.47 ton ha-1 yr-1), Kedung Ringin (68.83 ton ha-1 yr-1), Ringis (13.11 ton ha-1 yr-1) (Anonim, 2000). Sedimentation is weathering of the impervious surfaces of the riverbeds followed by the erosion of minerals from it, their transport, deposition and their burial. Flowing water moves and carries sediment over the riverbeds, exceeded with the changes of sediment carrying volume and water flow rate (Soewarno, 1991). Epipelic diatoms that live on sediment substrate are affected by the condition of the substrate. Therefore, the assessment of epipelic diatoms communities on ranged sedimentation rate of the rivers was needed to investigate whether and how this factor affects the epipelic diatoms communities. The objective of the research is to assess the relative abundance, diversity, evenness and similarity of epipelic diatom community of Torong, Galeh and Legi downstream rivers, which have varied sedimentation potencies. The assessment could serve database for environmental water monitoring, especially those related to sedimentation of the rivers. METHODS

The research was conducted in the Torong, Galeh and Legi downstream rivers located in Semarang, Central Java, Indonesia. Samples were taken on July 2004 at the downstream of Torong, Galeh and Legi rivers in 3 sampling site based on Justified Random sampling method (Figure 1).

Physicochemical parameters were measured in-situ at each sample site.

Temperature and pH of the water was recorded using pH meter 90 WTW. Electrical conductivity was measured using conductivity meter. DO meter YSI Model 51 B was used to measure oxygen content of the water. Turbidity was measured using turbid meter La Motte Model 2008. The transparency and depth of the site of the streams was recorded using Secchi disk.

Water samples collected from each sample site using water sampler. The

samples were sent for chemical analysis to Chemistry Laboratory, Diponegoro University, Semarang, Indonesia (UNDIP). Variables tested were silica (SiO2), total

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phosphorus (TP) and total nitrogen (TN). Sediment samples were taken at each sample site using modified corer. Cores were extruded and sectioned at 5 cm over the 20 cm cores achieved. The top layer (5 cm) was used for diatom analysis at Ecology and Biosystematics Laboratory UNDIP. The remaining cores sent to Chemistry Laboratory, UNDIP for SiO2, TP and TN analysis.

N 1 x a year rice field 2 x a year rice field

Rawapening Lake

Source: The Landuse Plan of Watershed Management of Rawapening. Local Government of Semarang 2000. Figure 1. River sampling site and their upstream catchments

1:50.000

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Preparation of diatom was followed those outlined in the Wetzel & Likens (1991). 4 gram sediment sample were put into a beaker glass, 50 mL Hydrogen Peroxide (H2O2) and 10 grams Potassium Dichromat (K2Cr2O7) were added carefully to oxidize organic matter and clean the diatom frustule. The beaker were placed on a hot plate and allowed to boil for 20 minutes. After boiling, the suspension was settled for 20 minutes and supernatant was removed. To the beaker, 50 mL aquadest were added and were boiled again on the hot plate for 20 minutes, was then settled for 20 minutes and supernatant was removed. This process was repeated a few times to ensure all trace of the acid were removed. The diatom residue was then stored for making permanent slides. 200 L diatom residue was pipette onto glass coverslips (20 mm x 20 mm) using micropipette. The coverslips were placed onto a warmer plate and was heated to evaporate the solution. Once dry, the coverslips affixed to slides with entellan, a high refractive index mountant. Three replicate slides were made from each sample to ensure maximum representation from diatom residue. All slides of diatom have been labeled and deposited with the Diponegoro University for future reference.

Diatoms are identified to the species level based on morphological

characteristic observed using light microscopy. In this research, diatoms were identified to species level following Gell et.al (1999), Gasse (1986) and Holland & Clark (1989). Enumeration of diatom was done by scanning the permanent slide of diatoms, first under 100 X, then 400X to assess general profile of the frustules and then frustules counted scanning the slide from top to bottom. Frustules count until minimal 100 frustules of the dominant species was reached (Round, 1993).

Epipelic diatom community was assessed using standard diatom metrics and

ecological indexes. Diatom relative abundance (Di) was calculated the number of species in a sample and determine the dominance species. Shannon diversity index (H’) reflects the number of species in the sample, as well as the equitability of their relative abundances, and was predicted to be lower at stressed sites. Evenness index (e) and Sorensen similarity index show the distribution pattern of diatom on sites. RESULTS AND DISCUSSION

A total of 148 species were identified in Torong, Galeh and Legi downstream rivers respectively. Composition of epipelic diatoms community at Torong, Galeh and Legi downstream were dominated by Pennatophycidae diatom (141 species) and only 7 species Centrophycidae diatom. Members of the Pennatophycidae diatom were represented by Achnanthes (5 species), Cymbella (8 species), Eunotia (10 species), Fragillaria (8 species), Gomphonema (14 species), Gyrosigma (5 species), Navicula (14 species), Nitzschia (9 species), Pinnularia (6 species), Surirella (7 species) and remaining 34 genera was represented less than 5 species (Table 1). It shows that Pennatophycidae diatoms were the prominent diatoms of benthic diatoms community (Killinc & Sivaci, 2001; Werner, 1977).

Centrophycidae diatoms are mainly holoplanktic or meroplanktic, with only a few genera that are associated with substrates throughout their life cycles and were rarely occur in epipelic diatoms communities. The presence of Centrophycidae diatoms in the epipelic diatom community was considered as sinking diatom that settled to the bottom of the rivers (Gell et.al, 1999). Centrophycidae diatoms recorded in the sediments of Torong, Galeh and Legi downstream were Aulacoseria distans

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Ehrenberg, Aulacoseria granulata Ehr., Cyclotella compta Kutzing, Cyclotella meneghiana Kutzing, Melosira sp., Melosira varians Agardh dan Stephanodiscus astraea Ehr. Table 1. Diatom species recorded from Torong, Galeh and Legi Downstream Aulacoseria Eunotia Neidium Aulacoseria distans Eunotia camelus Neidium affine Aulacoseria granulata Eunotia curvata Neidium sp Cyclotella Eunotia exigua Nitzschia Cyclotella compta Eunotia flexuosa Nitzschia acuta Cyclotella meneghiniana Eunotia lunaris Nitzschia atomus Melosira Eunotia monodon Nitzschia closterium Melosira sp Eunotia pectinalis Nitzschia fonticola Melosira varians Eunotia serpentina Nitzschia linearis Stephanodiscus Eunotia sp Nitzschia palea Stephanodiscus astraea Eunotia tenella Nitzschia sigmoidea Achnanthes Fallacia Nitzschia sp Achnanthes brevipes Fallacia pygmaea Nitzschia tryblionella Achnanthes delicatula Fragilaria Pinnularia Achnanthes lanceolatum Fragilaria imtermedia Pinnularia acuminate Achnanthes minutissima Fragilaria sp Pinnularia divergens Achnanthes sp. Fragillaria brevistriata Pinnularia gibba Amphora Fragillaria capucina Pinnularia leptosoma Amphora coffaeformis Fragillaria crotonensis Pinnularia sp Amphora ovalis Fragillaria pinnata Pinnularia viridis Amphora sp. Fragillaria rumpens Pleurosigma Amphora veneta Fragillaria virescens Pleurosigma obscurum Anomoeneis Frustulia Rhoicosphenia Anomoeneis sp Frustulia Rhoicosphenia abbreriata Bacillaria Frustulia rhomboides Rhopalodia Bacillaria Gomphonema Rhopalodia Bacillaria paradoxa Gomhpnema olivacea Rhopalodia gibba Caloneis Gomphonema acuminatum Rhopalodia vermicularis Caloneis Gomphonema affine Sellaphora Caloneis bacillum Gomphonema angustatum Sellaphora Caloneis ventricosa Gomphonema augur Sellaphora bacilum Campylodiscus Gomphonema constrictum Stauroneis Campylodiscus noricus Gomphonema fanensis Stauroneis Cocconeis Gomphonema gracile Stauroneis acuta Cocconeis placentula Gomphonema intricatum Stauroneis anceps Cocconeis sp Gomphonema lanceolatum Stauroneis phenicenteron Cymatopleura Gomphonema parvulum Stenopterobia Cymatopleura solea Gomphonema sp Stenopterobia intermedia Gomphonema truncatum Gomphonema ventricosum

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Table 1. Diatom species recorded from Torong, Galeh and Legi Downstream Cymbella Gyrosigma Surirella Cymbella affinis Gyrosigma acuminatum Surirella augusta Cymbella aspera Gyrosigma obtusatum Surirella linearis Cymbella caespitosa Gyrosigma scalproides Surirella nyassae Cymbella cistula Gyrosigma sp Surirella ovalis Cymbella prostata Gyrosygma peisonis Surirella robusta Cymbella sp Hantzschia Surirella sp Cymbella tumida Hantzschia amphyoxus Surirella spiralis Cymbella ventricosa Mastogloia Synedra Denticula Mastogloia Synedra acus Denticula Mastogloia elliptica Synedra affinis Denticula elegans Meridion Synedra capitata Diatoma Meridion circulare Synedra ulna Diatoma hiemale Navicula Tabellaria Diatoma vulgare Navicula acicularis Tabellaria flocculosa Diploneis Navicula atomus Tabularia Diploneis elliptica Navicula brakkaensis Tabularia fasciculate Diploneis ovalis Navicula cryptochepala Tabularia tabulate Diploneis smithii Navicula cuspidata Tersipnoe Encyonema Navicula erigmatica Tersipnoe musica. Her Encyonema minuta Navicula gallica Tryblionella Entomoneis Navicula geoppertiana Tryblionella levidensis Entomoneis alata Navicula gregaria Epithemia Navicula lanceolata Ephitemia argus Navicula mutica Ephitemia zebra Navicula pupula Navicula rhyncochepala Navicula sp

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Fragilaria cappucina

Pinnularia gibba

Navicula cryptochepala

Cymbella tumida

Source : Soeprobowati (2004) Under light microscopy 400 x magnification, picture was taken using

Olympus digital camera with optical zoom 5 x.

Figure 2. Some epipelic diatom recorded from Torong, Galeh and Legi downstream

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Tabularia sp.

Surirella linearis

Rhoicosphenia abbreviata

Gomphonema sp.

Source : Soeprobowati (2004) Under light microscopy 400 X magnification, picture was taken using

Olympus digital camera with optical zoom 5 X.

Figure 2. Some epipelic diatom recorded from Torong, Galeh and Legi downstream

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The highest population of epipelic diatoms were recorded in Legi downstream

(233.813 individu/g), followed by Torong downstream (188.367 individu/g) and Galeh downstream (137.829 individu/g) (Figure 3). Regarding on the sedimentation rate of the rivers, epipelic diatom population was found relatively high on Legi downstream that has higher sedimentation potencies. It was suspected related to sedimentation process. High sedimentation rate encourage the deposition of sediment particles along with diatom cell happen rapidly and at large quantities (Cawly, 2002).

0

50000

100000

150000

200000

250000

Torong Galeh Legi

Popu

lasi

(ind

ivid

u/gr

am)

Figure 3. Epipelic diatom population in Torong, Galeh and Legi downstream

Diversity index (Shannon-Wienner) and evenness index of epipelic diatom in Torong, Galeh and Legi were relatively high. Diversity index ranged from 4.31 up to 4.91, while the evenness index values from 0.91 to 1.27 (Figure 4). High diversity index reflects stable ecosystem of Torong, Galeh and Legi downstream based on epipelic diatom community. Evenness index of epipelic diatom in Torong, Galeh and Legi downstream indicates the quite even of species distribution on these downstream rivers (Odum, 1993).

4.61

4.31

4.91

3.80

4.00

4.20

4.40

4.60

4.80

5.00

5.20

5.40

Torong Galeh Legi

Div

ersi

ty in

dex

0.91 0.87

1.27

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

Torong Galeh Legi

even

ness

inde

x

Figure 4. Comparison of diversity index and evenness index of epipelic

diatom in Torong, Galeh and Legi downstream

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High diversity index and evenness index also related to sediment and water quality of Torong, Galeh and Legi downstream that support the diatom grow well. Generally, water quality has ranged pH value between 6.45 to 6.67; DO concentration value from 5.83 to 6.80 mg/L and SiO2 concentration value from 1.40 to 1.60 mg/L. high silica and DO concentration contribute to the increasing of diatom productivity and biomass (Anonim, 2005; Werner 1977).

Table 2. Water quality of Torong, Galeh and Legi downstream

STATION No. Parameters Torong Galeh Legi

1 pH 6.67 6.67 6.45 2 Conductivity (mS) 0.80 1.10 0.85 3 DO (mg/L) 6.80 6.50 5.83 4 Temperature (oC) 25.97 23.30 26.73 5 Transparency (cm) 11.17 11.00 65.00 6 Depth (cm) 81.67 116.67 65.00 7 Turbidity (NTU) 14.35 16.20 6.60 8 TSS 5.50 6.95 2.20 9 TDS 0.00 0.00 0.00 10 SiO2 (mg/L) 1.40 1.60 1.60 11 Total nitrogen (mg/L) 8.17 7.19 2.91 12 Total phospor (mg/L) 0.59 0.42 0.37 13 Sedimentation potencies (ton/ha/th) 77.73 166.16 369.63

Table 3. Sedimen quality of Torong, Galeh and Legi downstream

STATION No. Parameters Torong Galeh Legi

1 SiO2 (mg/L) 43.26 45.5 48.91 2 Total nitrogen (mg/L) 4.52 5.42 4.45 3 Total phospor (mg/L) 2.43 1.42 2.18

Similarity were observed between Torong, Galeh and Legi downstream rivers.

There was no difference in diatom species composition between the downstream rivers that could be inferred by high value of Sorensen index, ranged from 0.58 to 0.76 as shown on table 2 below.

Table 2. Epipelic Diatom Sorensen similarity index in Torong, Galeh and Legi

Station Sorensen similarity index Torong Galeh 0.58 Galeh Legi 0.70 Legi Torong 0.76

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Generally, diatom population in Torong, Galeh dan Legi as Rawapening inlets is similar with those in Rawapening Lake itself as well as in Rawapening Lake outlet. Plankton community in Rawapening Lake outlet showed that there was diatom species as plankton community assemblages that is also found in epipelic diatom assemblages in Rawapening Lake inlets. The similarity of diatom species composition between Torong, Galeh and Legi downstream rivers and Rawapening Lake outlet was 28 %. These planktonic diatoms species are Navicula sp., Eunotia pectinalis Rab., Fragilaria capucina var. rumpens Desmazieres, Tabellaria sp., Pinnularia gibba Ehr. dan Synedra ulna Her. (Astuti, 2005).

Epiphytic diatoms found in Rawapening Lake are Achnanthes minutissima Kutz., Cocconeis placentula Ehr., Epithemia zebra Ehr. Rhiocosphenia abbreviata Lange Bartalot dan Navicula rhyncocephala Kutz. (Kusnawati, 2005). These species were also found as epipelic diatom community in Torong, Galeh and Legi downstream rivers with quite high similarity at 43 %.

Epipelic diatoms populations of Torong, Galeh and Legi downstream are mix species of planktonic diatom (15 %), epiphytic diatom (21 %), epilitic diatom (14 %) and epipelic diatom (44 %). Varied diatom population is suspected due to planktonic diatoms that sink and buried over the bottom of the river, could be from epiphytic diatoms that lose from plant substrate because wind and finally sinking and buried in the sediment, also from epilitic diatom that release from rock surface (Killinc & Sivaci, 2001). Dominant species in Torong, Galeh and Legi downstream are Diploneis smithii Cleve also several species, such as Melosira varians Ag., Cymbella tumida Van Heurck, Meridion circulare Ag., Sellaphora sp., Synedra ulna Ehr. that dominant in all station (Torong, Galeh and Legi) (Figure 5).

Figure 5. Dominant epipelic diatom species in Torong, Galeh and Legi downstream

Legi

Galeh

0 5 10 15 20 0 5 10 15 20 250 5 10 15 20 250 5 10 15 20 250 5 10 15 20 250 5

Torong

10 15 20 25

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Those species were species that have high tolerant range and widely distributed species (Gell et.al, 1999).

The presence of Cyclotella meneghiana Kütz., Melosira varians Ag., Achnanthes lanceolata Round & Bukht., Amphora veneta Kütz., Cocconeis placentula Ehr., Gomphonema parvulum Kütz., Navicula geoppertiana Mann., Navicula mutica Mann., Nitzschia palea Kütz. and Rhoicosphenia abbreviata Lange-Bart. in Sungai Torong, Galeh dan Legi indicates eutrophication of the water region (Gell et.al., 1999; Fore & Grafe, 2002). Eutrophic water is aquatic habitat which has very high phosphor content, more than 0.02 mg/L, while oligotrophic is water with phosphor concentration less than 0,01 µg/L and the mesotrophic has phosphor concentration ranged between 0,01 to 0,02 mg/L (Waite, 1984). The phosphor concentration of the water was quite high and showed that Torong, Galeh and Legi downstream was in the eutrophic category, which have 0,37 to 0,59 mg/L of phosphor concentration. TP of the water were above the water quality standard for drinking water (0,2 mg/L), however it still meet the water quality standard for irrigation (0,5 µg/L) (PP No.82 Tahun 2001).

However, some species that indicate oligotrophic environment were found,

they are Achnanthidium minutissima Kütz., Meridion circulare Ag., Gomphonema lanceolatum Ehr. and also the mesotrophic species were found, such as Diatoma vulgare Bory dan Synedra ulna Ehr. Oligotrophic and meso-eutrophic species could not grow well under high nutrient (phosphor and nitrogen) concentration. CONCLUSSION The differences of sedimentation potencies of Torong, Galeh and Legi downstream river did not have strong influence on relative abundance, diversity, evenness and similarity of the epipelic diatom. ACKNOWLEDGEMENT I would like to thank the Grant Competitive Research XII No.031/SPP/PP/DP3M/IV/2005 for giving me the opportunity to work on this study. Many thanks to my mentor, Tri Retnaningsih Soeprobowati and Murningsih, and surveyor team for their support and encouragement. I would also like to thank Eni, Yunita and Maya for their invaluable help in the lab and Karyadi Baskoro for sharing his knowledge. Many thanks to Ecology & Biosystematics Lab staff and students for making this fun, memorable experience possible.

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Appendix

Legi 1 Legi 2

Legi 3

Galeh 1

Galeh 2

Galeh 3

Gomphonema lanceolatum

Torong 1

Torong 2

Torong 3