The community structure of epiphytons on Utricularia sp. and Hydrilla sp. plants at Situ Alam FMIPA Universitas Indonesia, Depok, West Java

Water plants will affect abundance and diversity of epiphytons in the community structure. The purpose of this research is to know the difference between the community structure of epiphytons on Utricularia sp. and Hydrilla sp., also periphytic planktons at Situ Alam FMIPA UI. Abundance and diversity of epiphytons community are the main discussion in this research. Research was carried out from March 2018 until May 2018. Using the purposive sampling method, samples were taken from Utricularia sp. and Hydrilla sp. Each sample was taken three times, one repetition, once every 2 weeks. Research showed that 67 genera, including 1 planktonic genus were found on the object glass. Utricularia sp. had higher abundance of epiphytons (84609 cells/mL) than Hydrilla sp. (74392 cells/mL). Both diversity indices are categorized as low diversity (H’ < 2.302). Different diversities were found between epiphytons on both plants (P < 0.05), but there was no difference between abundance of epiphytons on both plants (P > 0.05).


Introduction
Situ Alam FMIPA UI is a pond (1-1.5 m depth) isolated from other water sources, thus supporting growth of typical biota. Therefore,research about biotas that reside in this lake can determine conservation value of this lake. The Epiphyton's main role in an aquatic ecosystem consist of primary producers and contributors to nutrient cycles in maintaining the stability of an aquatic ecosystem. The structure of substrate affects abundance and diversity of epiphyton community. Utricularia sp. and Hydrilla sp. are two macrophytes with different morphological structures that potentially could become habitat for epiphytons [1]. Utricularia's bladders are suitable habitats for epiphyton growth such as Euglena, Phacus, Spirulina, and Anabaena sp. In return, Utricularia obtains Nitrogen source from the captured epiphytons [2]. Meanwhile, the leaves arrangement of Hydrilla around each node of the stem are easily attached by epiphytons [3].
There has not been any comparative study between epiphyton communities on Hydrilla sp. and Utricularia sp. at Situ Alam FMIPA UI yet. The aim of this study is to know the difference between community structuresof epiphyton on Utricularia sp. and Hydrilla sp., also to discover planktons that have the potential to become epiphytons in Situ Alam FMIPA UI, Depok, West Java. The hypothesis of

Study aarea
Research was conducted in Situ Alam FMIPA UI with the coordinates of 6° 22'05.9" S and 106° 49'31.0" E, Depok. Situ Alam does not have inlet and outlet, and is isolated from several situ in UI. Sampling stations were determined based on location of Utricularia sp. and Hydrilla sp. using purposive sampling method. Research was carried out March 2018 until May 2018. Coordinates for each sample location was taken with GPS (figure 1).

Physic-chemical water assessment
Some parameters like temperature, pH, and DO were measured in situ. The content of carbon dioxide, nitrate and phosphate were measured in laboratory Mutu Agun. Measured water parameters were temperature by thermometer, pH by pH paper indicator, Dissoved Oxygen with DO meters and CO2 using titration method. TDS and TSS were measured based on the results of filtering 50 mL of water sample with Whatman filter paper according to the method in [4,5]. The color of situ Alam water was documented with the camera.

Sampling, identification, and analysis of epiphyton and plankton samples
Epiphyton on object glass were acquired by binding to 3 threads at 10 cm, 77 cm, and 154 cm depths. After 1 week, epiphytons were taken based on [6]. Planktons in water are obtained by filtering water with planktonet. Epiphyton in Utricularia and Hydrilla was obtained by shaking the Utricularia and Hydrilla in a plastic bag filled with water [7]. All samples were preserved in 10 % formaldehyde. Enumeration and identification of samples was carried out under a microscope using the subsample method. The observed cells were counted with counter, documented with camera, and identified.
Abundance of epiphyton in cell/mL (N) was calculated using the formula: where n is number of individuals per mililitre in subsample; V isand (Vm) is plant volume [8].
Abundance of planktons in cell/mL (N): The number of individuals (Z)was multiplied by filtrated water (T) then divided by subsample volume (Y), then the result was divided the with sample volume (V) [9]. Shanon-Wiener Diversity Index (H'): with pi is the proportion of the ith genus. The samples were compared to see the potentially periphytic epiphyton. The result was computed into PAST v3 software for Sorensen similarity index. Data results between epiphyton on Hydrilla sp. and Utricularia sp. were then compared with t-test based on p-value of 0.05 (5 %) with formula: with D is the difference between the ith pair and n. Sd is the value of Standard deviation, and SD means Standard error [10,11]. was higher than zooepiphyton due to nature of predator plant of Utricularia, the bladder selects zooepiphyton as prey rather than epiphyton [12].

Abundance and diversity of epiphyton in
There were 67 genera of epiphyton on Hydrilla sp., Utricularia sp., on object glass, and water at Situ Alam. The results are categorized into Chlorophyta, Glaucophyta, Rapidophyta, and Bacillariophyta, Cyanophyta, Protozoa, Trochelminthes, and Arthropods (table 2).   Based on analysis (table 4), similiarity between epiphyton in Hydrilla sp. and Utricularia sp. is 77 %, indicating relatively high similarity. Dissimiliarity by 23 % result by different structure of the two plants on the leaves and stems.
Based on observation (table 5), epiphyton on Utricularia sp. had higher abundance than epiphyton on Hydrilla sp. Utricularia lives free-floating on water and shade Hydrilla. Sunlight can increase growth rate and photosynthesis of epiphyton and plant [13].
Based on observation (table 6), all samples had low diversity (H' < 2.302) [14]. Epiphyton on Hydrilla sp. had higher genus and diversity than epiphyton on Utriculariasp. Leaves arrangement (verticillata) and stem structure of Hydrilla are firmer than Utricularia, making it suitable for the growth of various microalgae such as diatoms [3]. Result shows diferent diversities (table 7) between epiphyton on both plants (P < 0.05), but there is no difference between abundance of epiphyton on both plants (P > 0.05).

Physical-chemical water assessment of Situ Alam FMIPA UI, Depok, West Java
The physical-chemical water assessment of Situ Alam were measured on the sides and middle area of the lake, which represent the condition of the lake. Result showed (table 8) that Situ Alam had acid pH, temperature suitable for Cyanophyta [15], low TSS and TDS, high DO, was an oligotrophic lake [16] and had a tolerable range of CO2 for Scenedesmus, Spirulina dan Euglena [17].
Both diversity indices are categorized as low diversity (H' < 2.302). Result shows different diversities between epiphytons on both plants (P < 0.05), but there is no difference between abundance of epiphytons on both plants (P > 0.05).