Aquatic hyphomycetes in hyporheic freshwater habitats of southwest India

Limnologica 42 (2012) 87–94

Contents lists available at SciVerse ScienceDirect

Limnologica journal homepage: www.elsevier.de/limno

Aquatic hyphomycetes in hyporheic freshwater habitats of southwest India Naga Mangala Sudheep, Kandikere Ramaiah Sridhar ∗ Department of Biosciences, Mangalore University, Mangalagangotri, Mangalore 574 199, Karnataka, India

a r t i c l e

i n f o

Article history: Received 26 September 2010 Received in revised form 14 February 2012 Accepted 14 February 2012 Keywords: Aquatic hyphomycetes Freshwater habitats Sediments Hyporheic zone Coarse particulate organic matter Fine particulate matter Cations

a b s t r a c t The hyporheic zones constitute a major site of storage of organic matter and energy flow in freshwater ecosystems. To complement the studies carried out in North America and Europe, we evaluated the sediment quality and occurrence of aquatic hyphomycetes in coarse particulate organic matter (CPOM; ≥5 mm) and fine particulate matter (FPM; ≤1 mm) in three locations of Kaiga stream and eight locations of Kadra dam of the River Kali in Western Ghats. The pH of sediments of stream and dam was acidic (5.8–6.6) and the average organic carbon of stream sediments was higher than dam sediments (8.6% vs. 3.9%). Among the eight minerals monitored, Fe was highest in all sediments and Ni was below detectable limit in four dam sediments. Spores of aquatic hyphomycetes were directly released from the CPOM fractions of sediments upon bubble chamber incubation, while the FPM fractions produced spores indirectly by colonization of sterile leaf baits followed by bubble chamber incubation. The species richness and diversity in CPOM was higher than FPM in stream as well as dam sediments. The Sorensen’s similarity indices between the fungal flora of CPOM in stream (66.7–81.8%) and dam (69.2–88%) locations were generally higher than FPM. The spore output per mg CPOM was between 1215 (dam) and 3384 (stream). The species richness was negatively correlated with Cr (P < 0.01; r = −1.000) of stream sediments, while it was negatively correlated with organic carbon (P < 0.05; r = −0.740) and positively correlated with K (P < 0.05; r = 0.750) of dam sediments. Occurrence and survival of aquatic hyphomycetes in hyporheic habitats of freshwater bodies indicate the importance of such zones as reservoir of fungal inoculum necessary in fundamental functions such as organic matter processing and energy flow. The present study provides baseline data on the sediment quality and fungal composition of stream and dam locations of River Kali of Kaiga region, which will develop as center of industrial activities in future. Crown Copyright © 2012 Published by Elsevier GmbH. All rights reserved.

Introduction Freshwater ecosystems, particularly woodland streams and rivers are known to receive plant detritus as major source of organic matter and energy (Cummins et al. 1983, 1989). Aquatic hyphomycetes, a polyphyletically heterogeneous group, dominate the colonization and decomposition of coarse particulate organic matter (CPOM) especially of allochthonous leaf litter (Bärlocher 1992a; Gulis et al. 2009). Their activities are usually high on CPOM and decline on fragmentation into fine particulate organic matter (FPOM) by physical or biological processes (Sinsabaugh and Findlay 1995; Findlay et al. 2002). Aquatic hyphomycetes have several counter adaptations to survive and disseminate in spite of unidirectional flow of water. They are known to persist in different niches of the stream ecosystem such as riparian canopy, leaf litter on stream bank, woody litter in streams, aquatic roots and hyporheic zones (e.g. Sridhar and Bärlocher 1992, 1993; Sati

∗ Corresponding author. Tel.: +91 824 2287 261; fax: +91 824 2287 367. E-mail address: [email protected] (K.R. Sridhar).

and Belwal 2005; Bärlocher et al. 2006; Gönczöl and Révay 2006; Karamchand and Sridhar 2008, 2009; Sridhar et al. 2008, 2010a). The hyporheic zone is an intermediate connecting ecotone between stream water and groundwater and plays an important role in organic matter mineralization, biogeochemical cycle and stream metabolism (Pusch and Schwoerbel 1994; Brunke and Gonser 1997; Storey et al. 1999; Cleven and Meyer 2003; Boulton 2007). Substantial quantities of organic matter are deposited in the hyporheic zones (25–82%) and serve as sink or source of energy in stream ecosystem (Cummins et al. 1983; Smock 1990; Boulton 1993; Jones et al. 1997; Storey et al. 1999). Although some reports are available on the occurrence of fungi in hyporheic or aquifer habitats, the structure and functions of such fungi are not clearly understood (e.g. Sinclair and Ghiorse 1989; Eichem et al. 1993; Madsen and Ghiorse 1993; Ellis et al. 1998). Specific studies on fungal occurrence and functions in hyporheic habitats have gained attention only in recent years (e.g. Bärlocher et al. 2006; Sridhar et al. 2008; Cornut et al. 2010). Investigations have been carried out on fungal colonization on the surface of glass beads buried in stream sediments (Bärlocher and Murdoch 1989), fungal occurrence in organic matter present in different depths of sediment (Bärlocher et al. 2006) and impact of temperature on hyporheic

0075-9511/$ – see front matter Crown Copyright © 2012 Published by Elsevier GmbH. All rights reserved. doi:10.1016/j.limno.2012.02.001

88

N.M. Sudheep, K.R. Sridhar / Limnologica 42 (2012) 87–94

aquatic hyphomycetes in Canada (Bärlocher et al. 2008). Interestingly, representatives of aquatic hyphomycetes found in the stream sediments (Sridhar et al. 2008) were also recovered in groundwater wells in Central Germany (Krauss et al. 2003, 2005). The rate of decomposition of leaf litter buried in sediments shown to decrease (Metzler and Smock 1990; Naamane et al. 1999), accelerate (Nichols and Keeney 1973) or gave ambiguous results (e.g. Mayack et al. 1989; Smith and Lake 1993). The pattern of colonization of aquatic hyphomycetes and decomposition of leaf litter buried in the stream sediments have been studied recently by Cornut et al. (2010) and Marmonier et al. (2010). Even though the fungal assemblages were generally less diverse in hyphoreic zones, they were responsible for 12% leaf mass loss in hyphoreic zone (Cornut et al. 2010). Such leaf mass loss was 2–3 times higher than the mass loss of leaf litter exposed partially into sediments and mass loss leaf litter exposed to the surface of sediments. The breakdown rates of buried leaf litter in hyporheic zones were high (k = 0.0011–0.0188 day−1 ) and were negatively correlated with decreased oxygen, and positively correlated with percentage of coarse particles of sediment (20–40 mm) and richness of benthic macro-invertebrates (Marmonier et al. 2010). Storey et al. (1999) predicted that hyporheic fungi also play a significant role in decomposition of allochthonous organic matter as well as its incorporation in to the food webs as evident in fungi in surface waters. To our knowledge, there are no reports on occurrence and functions of aquatic hyphomycetes in hyporheic habitats in tropical freshwater habitats of India. Therefore, as a first step the current study extends investigations on the occurrence of fungi in hyporheic zones of freshwaters of the Western Ghats in India. Our goal was to study the diversity of aquatic hyphomycetes in sediments of a tributary and a river. The main objectives were: (1) to assess the characteristics of sediments; (2) to compare the occurrence and diversity of aquatic hyphomycetes in coarse particulate organic matter (CPOM) and fine particulate matter (FPM) of sediments; (3) to determine the similarity of aquatic hyphomycetes in CPOM and FPM; (4) to correlate the sediment characteristics with that of species richness and spore output of aquatic hyphomycetes. As seen in leaves, water and foam in the streams of Western Ghats (Raviraja et al. 1998), we also expect high diversity of aquatic hyphomycetes in sediments. To assess the occurrence of aquatic hyphomycetes in sediments, the CPOM and FPM were separated and they were subjected to direct (bubble chamber incubation) and indirect (baiting sterile leaf disks followed by bubble chamber incubation) methods of evaluation respectively.

Materials and methods Sampling locations and sediment collection The sampling area chosen for study located in the tropical southwest coast of India (Fig. 1) receiving an average rainfall of about 280 cm year−1 . Three prominent seasons of this sampling area include monsoon (June–September), post-monsoon (October–January) and summer (February–May). The sampling locations selected for study at the River Kali basin are situated adjacent to the Kaiga nuclear power station (∼35 km east of Karwar city; ∼55–70 m asl; 14◦ 50 –14◦ 53 N, 74◦ 22 –74◦ 27 E). The River Kali is one of the major rivers originates at the Western Ghats, drains an area up to 3400 km2 and flows westward about 180 km before emptying into the Arabian Sea. The dominant riparian tree species of the locations chosen for sediment collection are Artocarpus heterophyllus Lam., Ficus benghalensis Linn., Ficus racemosa Roxb., Syzygium caryophyllatum (L.) Alston, Terminalia arjuna (Roxb.) W. & A., Terminalia paniculata Roth. and Xylia xylocarpa Roxb. Taub. The sediment samples of Kaiga

stream and Kadra dam were collected using Peterson’s Grab (capacity, 1 kg; Partex Products, Mumbai, India) during post-monsoon season (January 2009). The depth of the sampling locations was determined (SIMRAD Echosounder CE 33). The Kaiga stream is a third order stream with sandy loam and rocky bottom endowed with ample roots, wood and leaf detritus of forest origin. The sampling locations (S1–S3) were distributed along a stream reach of about 1 km and the depth during sampling period ranged between 1.5 (S1) and 3.5 m (S3). The sediment samples of stream location were brown and sandy loam with coarse particulate organic matter (CPOM). The sampling locations of Kadra dam (D1–D8) were stretched about 3 km and the depth of sampling locations was ranged between 3.6 m (D3) and 16.6 m (D8). The sediment samples of dam locations were gray or black consists of silt with or without CPOM.

Sediment characterization The pH and conductivity of sediment samples were evaluated at the sampling site. Samples of sediment were mixed with distilled water (1:2.5, w/v), shaken (10 min), and the pH (pH meter 335, Systronics, India) and conductivity (Conductivity meter 304, Systronics, India) were determined. The organic carbon of the sediments was evaluated following Walkley and Black’s rapid titration method (Jackson 1973). The Na and K of sediments were estimated by flame-emission photometry (MK1/MK3, Systronics, India) (AOAC 1995), while the Fe, Cu, Pb, Zn, Ni and Cr were detected after digestion with di-acid mixture (HNO3 and HClO4 ; 3:4, v/v) and by the atomic absorption spectrophotometry (GBC 932 Plus) (AOAC 1995).

CPOM and FPM The coarse particulate organic matter (CPOM) (≥5 mm) (spongy wood, bark, root, leaf lamina and petiole pieces identifiable in stream locations S1–S3 and S6–S8) were collected, rinsed in distilled water to remove attached particles. Randomly selected 5–6 CPOM fragments (total dry mass range, 150–300 mg) were aerated for up to 48 h in 250 ml Erlenmeyer flasks containing 150 ml of sterile distilled water (23 ± 2 ◦ C). The released conidia in bubble chambers were trapped on Millipore filters (5 ␮m, 47 mm diam.), stained with 0.1% cotton blue in lactophenol to enumerate and identify the spores of aquatic hyphomycetes. Each stained filter was cut in to half, mounted on a microscope slide with a few drops of lactic acid for screening spores (20–100×) (Nikon OPTIPHOT, Japan) and they were identified based on morphology using original literature and monographs (e.g. Ingold 1975; Nawawi 1985; Marvanová 1997; Gulis et al. 2005). The aerated CPOM were dried (80 ◦ C; 24 h) and mass was determined to calculate spore production per unit dry mass. The fine particulate matter (FPM) (≤1 mm) was separated from the sediment by sieving. Because it could not be handled like the CPOM, an indirect method was used to determine the occurrence of aquatic hyphomycetes (Sridhar et al. 2008). Five pre-weighed replicates of FPM samples were used (∼500–800 mg dry mass; parallel samples were weighed before and after drying at 80 ◦ C for 24 h to convert wet mass to dry mass). Each weighed wet FPM sample was transferred to a 250 ml Erlenmeyer flask containing 150 ml sterile distilled water with 5 baited sterile target leaf disks (1.5 cm diam.) of banyan (F. benghalensis). The flasks were incubated on a rotary shaker (150 rpm, 23 ± 2 ◦ C) up to 2 weeks. The harvested leaf disks were rinsed in distilled water to remove sediment and aerated in bubble chambers (23 ± 2 ◦ C) to stimulate spore production of aquatic hyphomycetes as described above.

N.M. Sudheep, K.R. Sridhar / Limnologica 42 (2012) 87–94

89

Fig. 1. Sediment sampling locations at the Kaiga stream (S1–S3) and Kadra dam (D1–D8) of the River Kali of southwest India.

Data analysis

Results

The Shannon’s diversity index (H ) (Magurran 1988) and Pielou’s equitability (J ) (Pielou 1975) of aquatic hyphomycetes in CPOM and FPM of sampling locations were calculated:

Sediment features

H = −



(pi ln pi )

where pi is the proportions of individual that species i contributes to the total number of individuals.  J  = (H  ÷ Hmax )  where Hmax is the maximum value of diversity for the number of species present. Sorensen’s similarity coefficient (CS ) (%) of aquatic hyphomycetes among CPOM and FPM and between CPOM and FPM of sediments of stream and dam locations was calculated based on Chao et al. (2005):

CS (%) = (2 × c) ÷ (a + b) × 100 where a is total number of taxa in location 1; b is total number of taxa in location 2; c is number of taxa common to locations 1 and 2. The relationship between species richness and spore output by CPOM against sediment parameters was assessed by Pearson’s correlation (parameters: P values, two tailed; confidence intervals, 95%) (SPSS 6.0 Windows Student Version 3.5).

The mean water temperature of stream locations was lower than dam locations (25.6 ◦ C vs. 30 ◦ C). The average depth of sampling locations of dam was greater than that in the stream (11.3 m vs. 2.3 m) (Table 1). The mean pH of dam sediments was more acidic than stream sediments (6.15 vs. 6.43). The average conductivity was higher in stream than dam sediments (29.5 ␮S cm−1 vs. 21.2 ␮S cm−1 ) as was the organic carbon content (8.55% vs. 3.9%). The average levels of Na, K and Zn of stream sediments was lower than the dam sediments, while Fe, Cu, Pb and Cr were higher in stream sediments. The Ni content was similar in sediments of both locations in spite of below detectable limits in four sediments of dam. Among all the cations, Fe content was highest in sediments of stream as well as dam. Fungi in stream and dam sediments Altogether 14 species of aquatic hyphomycetes were found in CPOM of stream sediments ranging between 9 (S3) and 12 (S1) (Table 2). The extent of spore output from CPOM followed similar pattern of species richness with highest in S1 (4613 mg−1 ) and lowest in S3 (2260 mg−1 ). The Shannon’s diversity and Pielou’s equitability of fungi were highest in S1 and least in S2. In FPM of

90

N.M. Sudheep, K.R. Sridhar / Limnologica 42 (2012) 87–94

Table 1 Water temperature, depth and physicochemical features of sediment samples collected from sampling sites of Kaiga stream (S1–S3) and Kadra dam (D1–D8) (n = 5, mean). Parameter

Water temperature (◦ C) Depth (m) pH Conductivity (␮S cm−1 ) Organic carbon (%) Na (mg/g) K (mg/g) Fe (mg/g) Cu (mg/g) Pb (mg/g) Zn (mg/g) Ni (mg/g) Cr (mg/g) a

Kaiga stream

Kadra dam

S1

S2

S3

D1

D2

D3

D4

D5

D6

D7

D8

Kaiga stream (n = 15, mean ± SD)

25.0 1.5 6.30 31.60 10.27 0.08 0.15 45.48 0.13 0.02 0.04 0.001 0.06

27.0 2.0 6.40 27.40 6.06 0.08 0.10 63.13 0.10 0.01 0.06 0.001 0.08

25.5 3.5 6.60 29.51 9.31 0.09 0.13 55.23 0.11 0.02 0.04 0.001 0.09

29.0 6.4 6.30 19.2 3.57 0.10 0.29 27.85 0.06 0.01 0.08 0.002 0.04

28.5 9.6 6.20 10.66 2.79 0.09 0.38 5.12 0.09 0.01 0.09 BDLa 0.03

28.0 3.6 5.80 25.84 3.31 0.08 0.21 52.24 0.09 0.02 0.12 BDLa 0.11

29.3 13.8 6.20 7.15 7.88 0.09 0.24 45.44 0.08 0.004 0.11 BDLa 0.05

30.0 10.4 5.90 20.12 3.55 0.10 0.41 55.21 0.10 0.001 0.09 0.001 0.04

29.9 15.0 6.10 10.22 2.06 0.08 0.40 60.87 0.11 0.02 0.09 BDLa 0.10

31.8 14.6 6.10 2.50 6.00 0.08 0.54 66.36 0.11 0.02 0.12 0.003 0.09

31.0 16.6 6.60 44.2 2.01 0.11 0.63 70.0 0.12 0.02 0.13 0.003 0.07

25.61 2.33 6.43 29.50 8.55 0.08 0.13 54.61 0.11 0.02 0.05 0.001 0.08

± ± ± ± ± ± ± ± ± ± ± ± ±

1.06 1.04 0.15 2.10 2.21 0.01 0.03 8.84 0.02 0.01 0.01 0.00 0.02

Kadra dam (n = 40, mean ± SD) 29.99 11.25 6.15 21.24 3.90 0.09 0.39 47.89 0.10 0.01 0.10 0.001 0.07

± ± ± ± ± ± ± ± ± ± ± ± ±

1.29 4.57 0.25 12.61 2.04 0.01 0.14 21.74 0.02 0.008 0.02 0.001 0.03

BDL, below detectable limit.

Table 2 Percent contribution (n = 5, mean) and relative abundance of spores of aquatic hyphomycetes recovered from coarse particulate organic matter (CPOM) of sediments collected from Kaiga stream sampling sites (S1–S3). Taxon

Triscelophorus monosporus Ingold Lunulospora curvula Ingold Triscelophorus acuminatus Nawawi Flagellospora curvula Ingold Anguillospora longissima (Sacc. & P. Syd.) Ingold Tetracladium marchalianum De Wild. Lunulospora cymbiformis K. Miura Triscelophorus konajensis K.R. Sridhar & Kaver. Cylindrocarpon sp. Ingoldiella hamata D.E. Shaw Tetracladium setigerum (Grove) Ingold Phalangispora constricta Nawawi & J. Webster Synnematospora constricta K.R. Sridhar & Kaver. Lateriramulosa uni-inflata Matsush. Species richness Total spore output/mg CPOM Shannon diversity Pielou’s equitability

Percent contribution

Relative abundance (%)

S1

S2

S3

26.0 18.5 13.8 9.6 12.5 6.8 6.3 4.8 – 0.9 – 0.5 0.2 0.1 12 4613 2.903 0.810

46.3 22.3 12.9 10.4 – 3.1 0.7 3.4 0.6 – – 0.2 0.2 – 10 3280 2.160 0.650

43.2 22.8 11.2 6.7 9.9 – 2.8 0.7 1.4 – 1.4 – – – 9 2260 2.320 0.732

stream sediments, 13 species of aquatic hyphomycetes were found ranging between 5 (S2) and 7 (S3) (Table 3). The Shannon’s diversity and Pielou’s equitability of fungi were highest in S3 and least in S2. The species richness and diversity were higher in CPOM than FPM of stream sediments.

36.4 20.7 12.9 9.2 7.9 4.1 3.7 3.4 0.5 0.4 0.3 0.3 0.2 0.1

The total species of aquatic hyphomycetes in CPOM of dam sediments of three locations was 17 ranged between 11 (D6) and 15 (D8) (Table 4). The spore output from CPOM was highest in D6 (1558 mg−1 ) and lowest in D8 (823 mg−1 ), whereas the Shannon’s diversity was highest in D8 and least in D6. The FPM of dam

Table 3 Percent contribution (n = 5, mean) and relative abundance of spores of aquatic hyphomycetes colonized on leaf disks incubated with fine particulate matter (FPM) of sediments collected from Kaiga stream sampling sites (S1–S3). Taxon

Percent contribution S1

Triscelophorus acuminatus Nawawi Triscelophorus monosporus Ingold Cylindrocarpon sp. Triscelophorus konajensis K.R. Sridhar & Kaver. Lunulospora curvula Ingold Lunulospora cymbiformis K. Miura Tetracladium sp. Flagellospora curvula Ingold Phalangispora constricta Nawawi & J. Webster Anguillospora longissima (Sacc. & P. Syd.) Ingold Tetracladium setigerum (Grove) Ingold Unidentified species (tetraradiate spore) Tetracladium marchalianum De Wild. Species richness Shannon diversity Pielou’s equitability

18.4 60.1 – 12.0 – – 4.2 – – 3.3 – 2.1 – 6 1.729 0.669

Relative abundance (%) S2 81.9 10.9 – – 3.6 – – 3.6 – – – – 0.1 5 0.940 0.405

S3 41.9 – 32.1 9.5 3.2 6.4 – – 3.5 – 3.2 – – 7 2.117 0.754

46.9 23.4 10.6 7.1 2.2 2.1 1.4 1.2 1.2 1.1 1.1 0.7 0.03

N.M. Sudheep, K.R. Sridhar / Limnologica 42 (2012) 87–94

91

Table 4 Percent contribution (n = 5, mean) and relative abundance of spores of aquatic hyphomycetes recovered from coarse particulate organic matter (CPOM) of sediments collected from Kadra dam sampling sites (D6–D8). Taxon

Percent contribution

Triscelophorus konajensis K.R. Sridhar & Kaver. Anguillospora longissima (Sacc. & P. Syd.) Ingold Flagellospora penicillioides Ingold Clavariopsis aquatica De Wild. Triscelophorus monosporus Ingold Flagellospora curvula Ingold Triscelophorus acuminatus Nawawi Alatospora acuminata Ingold Cylindrocarpon sp. Anguillospora crassa Ingold Arborispora palma K. Ando Tetracladium marchalianum De Wild. Lunulospora curvula Ingold Clavariana aquatica Nawawi Lateriramulosa uni-inflata Matsush. Lunulospora cymbiformis K. Miura Phalangispora constricta Nawawi & J. Webster Species richness Total spore output/mg CPOM Shannon diversity Pielou’s equitability

Relative abundance (%)

D6

D7

D8

26.0 22.9 21.6 14.8 6.7 4.0 2.2 – – 1.2 0.2 – – 0.3 – – 0.1 11 1558 2.578 0.745

29.4 23.8 20.8 9.1 5.7 2.6 2.9 3.5 0.6 0.3 0.4 – – 0.5 0.2 – 0.2 14 1263 2.658 0.698

27.6 17.3 18.5 11.2 5.4 2.0 3.4 2.7 4.0 – 1.7 2.7 1.9 0.5 0.6 0.7 – 15 823 3.065 0.785

27.6 22.0 20.6 12.0 6.0 3.1 2.7 1.8 1.1 0.6 0.6 0.6 0.4 0.4 0.2 0.2 0.1

Table 5 Percent contribution (n = 5, mean) and relative abundance of spores of aquatic hyphomycetes colonized on leaf disks incubated with fine particulate matter (FPM) of sediments collected from Kadra dam sampling sites (D1–D8). Taxon

Percent contribution D1

Triscelophorus acuminatus Nawawi Cylindrocarpon sp. Triscelophorus konajensis K.R. Sridhar & Kaver. Anguillospora longissima (Sacc. & P. Syd.) Ingold Anguillospora crassa Ingold Flagellospora penicillioides Ingold Tetracladium marchalianum De Wild. Arborispora palma K. Ando Clavariopsis aquatica De Wild. Alatospora acuminata Ingold Lunulospora curvula Ingold Flagellospora curvula Ingold Clavariana aquatica Nawawi Triscelophorus monosporus Ingold Species richness Shannon diversity Pielou’s equitability

41.3 – 46.6 2.9 – – – 2.5 – 4.9 1.0 – – 0.9 7 1.662 0.592

D2 47.6 – 44.1 1.5 – – – 4.2 – – – 2.7 – – 5 1.459 0.626

Relative abundance (%) D3

51.9 – 32.0 – 5.4 – – 5.4 5.4 – – – – – 5 1.699 0.732

sediments collected from 8 locations (D1–D8) yielded 14 species of aquatic hyphomycetes ranging between 2 (D5) and 7 (D1 and D4) (Table 5). The Shannon’s diversity and Pielou’s equitability of fungi were highest in D7 and least in D6. As seen in stream sediments, the species richness and diversity were higher in CPOM than FPM. The Sorensen’s similarity indices between the fungal flora of CPOM in stream (66.7–81.8%) (Table 6) as well as dam (69.2–88%) (Table 7) sediments were high. The similarity between FPM of stream sediments was relatively low (30.8–36.4%) (Table 6),

D4

D5

45.0 – 40.7 3.7 1.4 – – 7 – – – 1.0 1.0 – 7 1.710 0.609

– 92.2 7.8 – – – – – – – – – – – 2 0.395 0.395

D6

CPOM CS1

CS2 81.8 CS2

FPM CS3 66.7 66.7 CS3

FS1 44 37.5 53.3 FS1

FS2 58.8 66.7 57.1 36.4 FS2

FS3 52.6 70.6 62.5 30.8 33.3

22.2 – 11.1 33.3 – – 22.2 – – – 11.1 – – – 5 2.197 0.946

D8 – – – 16.2 39.0 26.6 – – 10.3 7.9 – – – – 5 2.090 0.900

26.1 23.8 22.9 7.2 5.7 3.3 2.8 2.4 2.0 1.6 1.5 0.5 0.1 0.1

however, except for four pairs of sediments the similarity between FPM of dam sediments was ≤60% (Table 7). The similarity between CPOM and FPM of stream sediments was ranged between 37.5% and 70.6% (Table 6) while in dam sediments it was ranged from 15.3% to 77.8% (Table 7).

Table 7 Sorensen’s similarity coefficient (%) of aquatic hyphomycetes in CPOM (C) and FPM (F) of Kadra dam locations (D1–D8). CPOM

Table 6 Sorensen’s similarity coefficient (%) of aquatic hyphomycetes in CPOM (C) and FPM (F) of Kaiga stream locations (S1, S2 and S3).

D7

0.5 98.6 1.0 – – – – – – – – – – – 3 0.126 0.080

CD6

CD7 88 CD7

FPM CD8 69.2 82.8 CD8

FD1 55.6 57.1 63.6 FD1

FD2 62.5 52.6 50.0 66.7 FD2

FD3 62.5 52.6 40.0 50.0 60.0 FD3

FD4 77.8 66.7 54.5 57.1 83.3 50.0 FD4

FD5 15.4 25.0 23.5 22.2 28.6 28.6 22.2 FD5

FD6 28.6 35.3 33.3 40.0 50.0 25.0 40.0 80.0 FD6

FD7 37.5 31.6 50.0 66.7 60.0 40.0 50.0 28.6 50.0 FD7

FD8 50.0 52.6 40.0 33.3 20.0 40.0 33.3 0 0 20.0

92

N.M. Sudheep, K.R. Sridhar / Limnologica 42 (2012) 87–94

The species richness was significantly negatively correlated with chromium of Kaiga stream sediments (P < 0.01; r = −1.000), while it was significantly negatively correlated with organic carbon (P < 0.05; r = −0.740) and positively correlated with K (P < 0.05; r = 0.750) of Kadra dam sediments. However, the spore output of CPOM was correlated with none of the sediment parameters assessed.

Discussion Occurrence and functions of aquatic hyphomycetes have been studied on the naturally deposited or baited leaf litter on stream bed and up to a lesser extent in hyporheic zones in temperate regions (e.g. Bärlocher 1992b; Bärlocher et al. 2006, 2008; Sridhar et al. 2008). A variety of naturally buried organic matter in sediments (e.g. leaf, grass, root, twig and wood) supported aquatic hyphomycetes in water bodies of Canada and Germany (Bärlocher et al. 2006, 2008; Sridhar et al. 2008). Studies on baiting leaf litter in hyporheic zones reconfirmed substantial fungal biomass, fungal spore production and leaf decomposition (Cornut et al. 2010; Marmonier et al. 2010). Our study revealed decreased species richness, diversity and similarity in FPM than CPOM of sediment, which parallels low fungal biomass in FPM as reported earlier (Sinsabaugh and Findlay 1995; Findlay et al. 2002). Occurrence of aquatic hyphomycetes in sediments was significantly decreased with depth, which was related to scarcity of organic matter (Bärlocher et al. 2006). However, increased grain size with depth correlated with more oxygen, which supports survival of fungal propagules in interstices. The average species richness of aquatic hyphomycetes in CPOM and FPM of stream sediments was higher than dam sediments in our study may be because of low depth, high rate of water flow, high oxygen saturation and increased organic carbon. Longevity of aquatic hyphomycetes under anaerobic conditions up to 12 months was reported by Field and Webster (1983). However, depletion of oxygen saturation from 94% to 4% in microcosm experiments showed 60% loss in species richness and 90% loss in fungal biomass resulting in low spore output (Medeiros et al. 2009). The ergosterol concentration of particulate matter of 49 Baltic rivers (mean, 56.4 ng l−1 ) during summer was positively correlated with concentrations of dissolved organic matter and inorganic nutrients by Jørgensen and Stepanauskas (2009). High breakdown rates of buried leaf litter in hyporheic zones were negatively correlated with decreased oxygen levels and positively correlated with percent coarse particles in sediments as well as with richness of benthic macro-invertebrates (Marmonier et al. 2010). Besides low dissolved oxygen, a variety of stresses also affects the aquatic hyphomycetes in hyporheic habitats (e.g. pH, heavy metals, organic pollutants and low organic matter). Decrease in species richness of aquatic hyphomycetes was negligible in circumneutral waters (pH, 5.7–7.2), but a rapid decline was seen in alkaline waters in Canadian and European streams (pH, >7.2) (Bärlocher 1987). Similarly, a negative correlation was seen between species richness and pH in Western Ghat streams by Raviraja et al. (1998). In the current study, the pH of sediments was in the circumneutral range (5.8–6.6), which is not detrimental to aquatic hyphomycetes. Abel and Bärlocher (1984) reported rapid accumulation of Cd by aquatic hyphomycetes colonized on leaves. Sediment fungi in streams were superior to bacteria in Cd sequestration (Massaccesi et al. 2002). Besides heavy metals, Heliscus lugdunensis is known to transform organic pollutants such as 1-naphthol and likely the polycyclic aromatic hydrocarbons commonly found in sediments of water bodies in Central Germany (Augustin et al. 2006; Sridhar et al. 2008). Similarly, Mucor racemosus and Phialophora alba degraded pyrene in freshwater sediments (Ravelet et al. 2001). In

Kali River sediments 210 Pb (r = 0.20) and 210 Po (r = 0.82) were positively correlated with organic matter by Narayana and Rajashekar (2008). Surprisingly, in our study, the species richness of aquatic hyphomycetes was negatively correlated with organic carbon in Kadra dam sediments. As the decomposition of organic matter in sediments demands oxygen, depletion of oxygen may differentially influence the aquatic hyphomycetes present in organic matter. Interestingly, in our study the Sorensen’s similarity between fungal flora of CPOM in stream (66.7–81.8%) as well as dam (69.2–88%) sediments were generally high, but it was relatively low between FPM of stream (30.8–36.4%) as well as dam (≤60%) sediments (except for four pairs of sediments). The low species richness of aquatic hyphomycetes in River Bhadra, River Sitabhumi and Lakya stream of the Western Ghats was suspected due to high iron content (Raghu et al. 2001; Rajashekhar and Kaveriappa 2003). Similarly, Maltby and Booth (1991) reported sensitivity of aquatic hyphomycetes to high iron content of the River Don in England. In our study, despite high iron content in sediments (48–55 mg/g), dominance of Anguillospora longissima, Clavariopsis aquatica, Cylindrocarpon sp., Flagellospora penicillioides, Lunulospora curvula and Triscelophorus spp. indicating their tolerance to high iron content. Rajashekhar and Kaveriappa (2003) in Western Ghat streams and rivers also predicted the tolerance of Anguillospora spp., L. curvula and Triscelophorus spp. to high iron content (10.9–11.3 mg l−1 ) and low oxygen levels (4.0 mg l−1 and below). Boulton (2007) and Sarriquet et al. (2007) addressed the basic characteristics of healthy hyporheic zones of rivers and suggested the strategies necessary for rehabilitation of impaired hyporheic zones to restore the vertical connectivity. Some studies demonstrated impoverished fungal community on leaf litter deposited on the sediment surface in water bodies of Mansfelder Land of Central Germany contaminated with heavy metals (Jaeckel et al. 2005; Krauss et al. 2005, Sridhar et al. 2005; Braha et al. 2007). In spite of heavy metal pollution and low oxygen, stream sediments of Mansfelder Land consists of 8–15 species of aquatic hyphomycetes (Sridhar et al. 2008), which comparers to 20 species in the hyporheic zone of an unpolluted springbrook of Canada (Bärlocher et al. 2006) and 23 species in the present study. Although there is a wide difference in population structure of aquatic hyphomycetes in freshwater sediments between temperate regions and the present study, Alatospora acuminata, Anguillospora crassa, A. longissima, Clavariopsis aquaica and Flagellospora curvula were common (Bärlocher et al. 2006, 2008; Sridhar et al. 2008). Naturally accumulated leaf litter in Kali River yielded 18 species of aquatic hyphomycetes (Sridhar et al. 2010b), which is close to the species richness in sediments of Kadra dam in our study (17 species). Dominance of Cylindrocarpon sp., L. curvula, Triscelophorus acuminatus and Triscelophorus monosporus in sediments of Kaiga stream and A. longissima, C. aquatica, Cylindrocarpon sp., F. penicillioides, T. acuminatus and Triscelophorus konajensis in sediments of Kadra dam in our study is comparable to leaf litter colonized aquatic hyphomycetes in Kali River (Sridhar et al. 2010b) and possibly they serve as ideal candidates for bioremediation. Occurrence and survival of fungi in hyporheic habitats of freshwater bodies indicate the importance of such zones as reservoir of fungal inoculum involving in basic ecological services of organic matter processing and energy flow. Diverse fungal taxa including unculturable species have been documented in freshwater sediments using molecular approaches (Bärlocher et al. 2008). Clone libraries and fingerprints also revealed diverse fungal flora in anoxic sediments (Takishita et al. 2007). Analysis of organic matter by denaturing gradient gel electrophoresis resulted in identification of additional species of aquatic hyphomycetes as well as other fungal taxa which were not detectable by traditional techniques (Bärlocher et al. 2006). Knowledge on fungi in sediments and their role especially in accumulation and transformation of pollutants

N.M. Sudheep, K.R. Sridhar / Limnologica 42 (2012) 87–94

helps to understand the fundamental processes to evolve strategies of bioremediation. As hyporheic zones serve as sink for several pollutants (e.g. heavy metals and organics), many basic questions need to be addressed in future: What are the roles of fungi in accumulation and transformation of pollutants? Are there any limits of fungi to mobilize and transform pollutants in hyporheic zones? To what extent do hyporheic fungi decrease the release of pollutants in to groundwaters? Do the stress-tolerant fungal strains exist in hyporheic zones helpful in detoxification of toxic compounds? Acknowledgements The authors are grateful to Mangalore University for permission to carry out this study at the Department of Biosciences and Nuclear Power Corporation of India Ltd. (NPCIL), Mumbai for funding. NMS is indebted to the NPCIL for the award of research fellowship. Authors are thankful to Drs. H.M. Somashekarappa, University Science Instrumentation Centre, Mangalore University, S.G. Ghadge, M. Kansal, P.M. Ravi, B.N. Dileep and S.K. Singh, NPCIL, Kaiga, Karnataka for support. References AOAC, 1995. Official Methods of Analysis of the Association of Official Analytical Chemists. Association of Official Analytical Chemists, Arlington, VA, USA. Abel, T.H., Bärlocher, F., 1984. Effects of cadmium on aquatic hyphomycetes. Appl. Environ. Microbiol. 48, 245–251. Augustin, T., Schlosser, D., Schmidt, J., Baumbach, R., Grancharov, K., Krauss, G., Krauss, G.-J., 2006. Biotransformation of 1-naphthol by the aquatic hyphomycete Heliscus lugdunensis. Curr. Microbiol. 52, 216–220. Bärlocher, F., 1987. Aquatic hyphomycete spora in 10 streams of New Brunswick and Nova Scotia. Can. J. Bot. 65, 76–79. Bärlocher, F., 1992a. Research on aquatic hyphomycetes: historical background and overview. In: Bärlocher, F. (Ed.), The Ecology of Aquatic Hyphomycetes. Springer, Berlin, pp. 1–15. Bärlocher, F., 1992b. Community organization. In: Bärlocher, F. (Ed.), The Ecology of Aquatic Hyphomycetes. Springer, Berlin and New York, pp. 38–76. Bärlocher, F., Murdoch, J.H., 1989. Hyporheic biofilms – a potential food source for interstitial animals. Hydrobiologia 184, 61–68. Bärlocher, F., Nikolcheva, L.G., Wilson, K.P., Williams, D.D., 2006. Fungi in the hyporheic zone of a springbrook. Microb. Ecol. 52, 708–715. Bärlocher, F., Seena, S., Wilson, K.P., Williams, D.D., 2008. Raised water temperature lowers diversity of hyporheic aquatic hyphomycetes. Freshwat. Biol. 53, 368–379. Boulton, A.J., 1993. Stream ecology and surface-hyporheic hydrologic interchange: implications, techniques and limitations. Aust. J. Mar. Freshwat. Res. 44, 553–564. Boulton, A.J., 2007. Hyporheic rehabilitation in rivers: restoring vertical connectivity. Freshwat. Biol. 52, 632–650. Braha, B., Tintemann, H., Krauss, G., Ehrman, J., Bärlocher, F., Krauss, G.-J., 2007. Heavy metal stress response in two strains of the aquatic hyphomycete Heliscus lugdunensis. Biometals 20, 93–105. Brunke, M., Gonser, T., 1997. The ecological significance of exchange processes between rivers and groundwater. Freshwat. Biol. 37, 1–33. Chao, A., Chazdon, R.L., Colwell, R.K., Shen, T.-J., 2005. A new statistical approach for assessing similarity of species composition with incidence and abundance data. Ecol. Lett. 8, 148–159. Cleven, E.J., Meyer, E.I., 2003. A sandy hyporheic zone limited vertically by a solid boundary. Arch. Hydrobiol. 157, 267–288. Cornut, J., Elger, A., Lambrigot, D., Marmonier, P., Chauvet, E., 2010. Early stages of leaf decomposition are mediated by aquatic fungi in the hyporheic zone of woodland streams. Freshwat. Biol. 55, 2541–2556. Cummins, K.W., Sedell, J.R., Swanson, F.J., Minshall, G.W., Fisher, S.G., Cushing, C.E., Petersen, R.C., Vannote, R.L., 1983. Organic matter budgets for stream ecosystems: problems in their evaluation. In: Barnes, J.R., Minshall, G.W. (Eds.), Stream Ecology. Application and Testing of General Ecological Theory. Plenum Press, New York, pp. 299–353. Cummins, K.W., Wilzbach, M.A., Gates, D.M., Perry, J.B., Taliaferro, W.B., 1989. Shredders and riparian vegetation. Bioscience 39, 24–30. Eichem, A.C., Doss, W.K., Tate, C.M., Edler, C., 1993. Microbial decomposition of elm and oak leaves in a karst aquifer. Appl. Environ. Microbiol. 59, 3592–3596. Ellis, B.K., Stanford, J.A., Ward, J.V., 1998. Microbial assemblages and production in alluvial aquifers of the Flathead River, Montana, USA. J. N. Am. Benthol. Soc. 17, 382–402. Field, J.I., Webster, J., 1983. Anaerobic survival of aquatic fungi. Trans. Br. Mycol. Soc. 81, 365–369. Findlay, S., Tank, J., Dye, S., Valett, H.M., Mulholland, P.J., McDowell, W.H., Johnson, S.L., Hamilton, S.K., Edmonds, J., Dodds, W.K., Bowden, W.B., 2002. A

93

cross-system comparison of bacterial and fungal biomass in detritus pools of headwater streams. Microb. Ecol. 43, 55–66. Gönczöl, J., Révay, Á., 2006. Species diversity if rainborne hyphomycete conidia from living trees. Fungal Divers 22, 37–54. Gulis, V., Marvanová, L., Descals, E., 2005. An illustrated key to the common temperate species of aquatic hyphomycetes. In: Grac¸a, M.A.S., Bärlocher, F., Gessner, M.O. (Eds.), Methods to Study Litter Decomposition: a Practical Guide. Springer, Dordrecht, pp. 153–167. Gulis, V., Kuehn, K.A., Suberkropp, K., 2009. Fungi. In: Likens, G. (Ed.), Encyclopedia of Inland Waters, vol. 3. Elsevier, Oxford, pp. 233–243. Ingold, C.T., 1975. An Illustrated Guide to Aquatic and Waterborne Hyphomycetes (Fungi Imperfecti) with Notes on their Biology Freshwater Biological Association Scientific Publication # 30, UK. Jackson, M.L., 1973. Soil Chemical Analysis. Prentice Hall International, USA. Jaeckel, P., Krauss, G., Menge, S., Schierhorn, A., Ruecknagel, P., Krauss, G.-J., 2005. Cadmium induced a novel metallothionein and phytochelatin 2 in an aquatic fungus. Biochem. Biophys. Res. Commun. 333, 150–155. Jones, J.B., Schade, J.D., Fisher, S.G., Grimm, N.B., 1997. Organic matter dynamics in sycamore creek, a desert stream in Arizona, USA. J. N. Am. Benthol. Soc. 16, 78–82. Jørgensen, N.O.G., Stepanauskas, R., 2009. Biomass of pelagic fungi in Baltic rivers. Hydrobiologia 623, 105–112. Karamchand, K.S., Sridhar, K.R., 2008. Water-borne conidial fungi inhabiting tree holes of the west coast and Western Ghats of India. Czech Mycol. 60, 63– 74. Karamchand, K.S., Sridhar, K.R., 2009. Association of water-borne conidial fungi with epiphytic tree fern (Drynaria quercifolia). Acta Mycol. 44, 19–27. Krauss, G., Sridhar, K.R., Jung, K., Wennrich, R., Ehrman, J., Bärlocher, F., 2003. Aquatic hyphomycetes in polluted groundwater habitats of Central Germany. Microb. Ecol. 45, 329–339. Krauss, G., Sridhar, K.R., Bärlocher, F., 2005. Aquatic hyphomycetes and leaf decomposition in contaminated groundwater wells in Central Germany. Arch. Hydrobiol. 162, 416–428. Madsen, E.L., Ghiorse, W.C., 1993. Groundwater microbiology: subsurface ecosystem processes. In: Ford, T. (Ed.), Aquatic Microbiology: An Ecological Approach. Blackwell, Cambridge, MA, pp. 167–213. Magurran, A.E., 1988. Ecological Diversity and its Measurement. Princeton University Press, New Jersey. Maltby, L., Booth, R., 1991. The effect of coal-mine effluent on fungal assemblages and leaf breakdown. Water Res. 25, 247–250. Marmonier, P., Piscart, C., Sarriquet, P.E., Azam, D., Chauvet, E., 2010. Relevance of large litter bag burial for the study of leaf breakdown in the hyporheic zone. Hydrobiologia 641, 203–214. Massaccesi, G., Romero, M., Cazau, M., Bucsinszky, A., 2002. Cadmium removal capacities of filamentous soil fungi isolated from industrially polluted sediments, in La Plata (Argentina). World J. Microb. Biotechnol. 18, 817– 820. Marvanová, L., 1997. Freshwater hyphomycetes: a survey with remarks on tropical taxa. In: Janardhanan, K.K., Rajendran, C., Natarajan, K., Hawksworth, D.L. (Eds.), Tropical Mycology. Science Publishers, New York, pp. 169–226. Mayack, D.T., Thorp, J.H., Cothran, M., 1989. Effects of burial and floodplain retention on stream processing of allochthonous litter. Oikos 54, 378– 388. Medeiros, A.O., Pascoal, C., Grac¸a, M.A.S., 2009. Diversity and activity of aquatic fungi under low oxygen conditions. Freshwat. Biol. 54, 142–149. Metzler, G.M., Smock, L.A., 1990. Storage and dynamics of subsurface detritus in a sandbottomed stream. Can. J. Fish. Aquat. Sci. 47, 588–594. Naamane, B., Chergui, H., Pattee, E., 1999. The breakdown of leaves of poplar and holm oak in three Moroccan streams: effect of burial in the sediment. Int. J. Limnol. 35, 263–275. Narayana, Y., Rajashekar, K.M., 2008. Study of 210 Po and 210 Pb in the riverine environments of coastal Karnataka. J. Environ. Radioact. 101, 468–471. Nawawi, A., 1985. Aquatic hyphomycetes and other water-borne fungi from Malaysia. Malaysian Nat. J. 39, 75–134. Nichols, D.S., Keeney, D.R., 1973. Nitrogen and phosphorus release from decaying milfoil. Hydrobiologia 42, 509–525. Pielou, F.D., 1975. Ecological Diversity. Wiley InterScience, New York. Pusch, M., Schwoerbel, J., 1994. Community respiration in hyporheic sediments of a mountain stream (Steina, Black Forest). Arch. Hydrobiol. 130, 35–52. Raghu, P.A., Sridhar, K.R., Kaveriappa, K.M., 2001. Diversity and conidial output of aquatic hyphomycetes in heavy metal polluted river, Southern India. Sydowia 53, 236–246. Rajashekhar, M., Kaveriappa, K.M., 2003. Diversity of aquatic hyphomycetes in the aquatic ecosystems of the Western Ghats of India. Hydrobiologia 501, 167– 177. Ravelet, C., Grosset, C., Krivobok, S., Montuelle, B., Alary, J., 2001. Pyrene degradation by two fungi in a freshwater sediment and evaluation of fungal biomass by ergosterol content. Appl. Microbiol. Biotechnol. 56, 803–808. Raviraja, N.S., Sridhar, K.R., Bärlocher, F., 1998. Fungal species richness in Western Ghat streams (Southern India); is it related to pH, temperature or altitude? Fungal Divers 1, 179–191. Sarriquet, P.E., Bordenave, P., Marmonier, P., 2007. Effects of bottom sediment restoration on interstitial habitat characteristics and benthic macroinvertebrate assemblages in a head water stream. River Res. Appl. 23, 815–828. Sati, S.C., Belwal, M., 2005. Aquatic hyphomycetes as endophytes of riparian plant roots. Mycologia 97, 45–49.

94

N.M. Sudheep, K.R. Sridhar / Limnologica 42 (2012) 87–94

Sinclair, J.L., Ghiorse, W.C., 1989. Distribution of aerobic bacteria, protozoa, algae, and fungi in deep subsurface sediments. Geomicrobiology 7, 15–31. Sinsabaugh, R.L., Findlay, S., 1995. Microbial production, enzyme activity, and carbon turnover in surface sediments of the Hudson River estuary. Microb. Ecol. 30, 127–141. Smock, L.A., 1990. Spatial and temporal variation in organic matter storage in lowgradient, headwater streams. Arch. Hydrobiol. 118, 169–184. Smith, J.J., Lake, P.S., 1993. The breakdown of buried and surface-placed leaf-litter in an upland stream. Hydrobiologia 271, 141–148. Sridhar, K.R., Bärlocher, F., 1992. Endophytic aquatic hyphomycetes in spruce, birch and maple. Mycol. Res. 96, 305–308. Sridhar, K.R., Bärlocher, F., 1993. Aquatic hyphomycetes on leaf litter in and near a stream in Nova Scotia, Canada. Mycol. Res. 97, 1530–1535. Sridhar, K.R., Bärlocher, F., Krauss, G.-J., Krauss, G., 2005. Response of aquatic hyphomycete communities to changes in heavy metal exposure. Int. Rev. Hydrobiol. 90, 21–32.

Sridhar, K.R., Bärlocher, F., Wennrich, R., Krauss, G.-J., Krauss, G., 2008. Fungal biomass and diversity in sediments and on leaf litter in heavy metal contaminated waters of Central Germany. Fundam. Appl. Limnol. 171, 63–74. Sridhar, K.R., Karamchand, K.S., Hyde, K.D., 2010a. Wood-inhabiting filamentous fungi in 12 high altitude streams of the Western Ghats by damp incubation and bubble chamber incubation. Mycoscience 51, 104–115. Sridhar, K.R., Arun, A.B., Maria, G.L., Madhyastha, M.N., 2010b. Diversity of fungi on submerged leaf and woody litter in River Kali, Southwest India. Environ. Res. J. 5, 1–14. Storey, R.G., Fulthorpe, R.R., Williams, D.D., 1999. Perspectives and predictions on the microbial ecology of the hyporheic zone. Freshwat. Biol. 41, 119–130. Takishita, K., Tsuchiya, M., Kawato, M., Oguri, K., Kitazato, H., Maruyama, T., 2007. Genetic diversity of microbial eukaryotes in anoxic sediment of the saline meromictic Lake Namako-ike (Japan): on the detection of anaerobic or anoxictolerant lineages of eukaryotes. Protist 158, 51–64.