The Vertical Dynamics of Larval Chironomids on Artificial Substrates in Lake Lido (Bogor, Indonesia)

Abstract

The composition and abundance of chironomid larval communities was studied on artificial substrates in Lido Lake, located in Bogor, West Java, Indonesia. The lake is organically enriched as a result of fish farming activity. Seventy two artificial substrates were deployed at three depths (2.0, 3.5 and 5.0 m) at two sites: a cage culture site and a non-cage culture site (control). Larval chironomid larvae were collected 7, 14, 28 and 56 days after the artificial substrates were deployed. In addition, selected physical and chemical parameters of the water were simultaneously measured. Three chironomid subfamilies, the Chironominae, Tanypodinae and Orthocladiinae, were found at both sites. At the cage culture site, both diversity and total abundance were significantly higher at the 2.0 and 3.5 m depths than at the 5.0 m depth, but this was not the case at the non-cage culture site. Based on pooling of the data from all depths, a Mann-Whitney U test showed that the non-cage culture site had a significantly higher diversity and total abundance than the cage culture site. Dissolved oxygen (DO) and turbidity showed significant differences between the 2.0 m depth and the 2 greater depths at the cage culture site, whereas none of the environmental parameters showed significant differences among the three depths at the non-cage culture site. A comparison of the environmental parameters at the same depth at the two sites showed significant differences in turbidity, pH and DO. A Spearman rank correlation analysis at the cage culture site showed that abundance and DO were positively correlated, whereas abundance and turbidity were negatively correlated. However, only pH was negatively correlated with abundance at the non-cage culture site.

Kelimpahan dan komposisi komuniti larva kironomid di atas substrat buatan telah dikaji di Tasik Lido, Bogor, Jawa Barat, Indonesia. Tasik ini kaya secara organik kerana aktiviti penternakan ikan. Tujuh puluh dua substrat buatan telah diatur pada tiga kedalaman (2.0, 3.5 dan 5.0 m) di dua lokasi: satu lokasi kultur sangkar dan satu lokasi kultur bukan sangkar (kawalan). Larva kironomid telah dikumpul pada 7, 14, 28 dan 56 hari selepas substrat buatan diaturkan. Pada masa yang sama, beberapa parameter fizikal dan kimia air juga telah diukur. Tiga subfamili kironomid iaitu Chironominae, Tanypodinae dan Orthocladiinae telah dijumpai di kedua-dua lokasi. Di lokasi kultur sangkar, kedua-dua kepelbagaian dan jumlah kelimpahan lebih tinggi secara signifikan pada kedalaman 2.0 dan 3.5 m berbanding kedalaman 5.0 m; walau bagaimanapun keadaan ini tidak sama di lokasi kultur bukan sangkar. Berdasarkan data terkumpul daripada semua kedalaman, ujian Mann-Whitney U telah menunjukkan bahawa lokasi kultur bukan sangkar mempunyai kepelbagaian dan jumlah kelimpahan yang lebih signifikan daripada lokasi kultur sangkar. Oksigen terlarut dan kekeruhan menunjukkan pebezaan signifikan antara kedalaman 2.0 m dan 2 kedalaman yang lain di lokasi kultur sangkar, manakala tiada satu parameter persekitaran pun menunjukkan perbezaan signifikan antara ketiga-tiga kedalaman di lokasi kultur bukan sangkar. Perbandingan parameter persekitaran pada kedalaman yang sama di kedua-dua lokasi menunjukkan perbezaan yang signifikan untuk kekeruhan, pH dan oksigen terlarut. Analisis Spearman rank di lokasi kultur sangkar telah menunjukkan bahawa kelimpahan dan oksigen terlarut berkorelasi secara positif, manakala kelimpahan dan kekeruhan berkorelasi secara negatif. Walau bagaimanapun, hanya pH yang berkorelasi secara negatif dengan kelimpahan di lokasi kultur bukan sangkar.