Morphological traits and vertical distribution of hyporheic chironomid larvae in Atlantic Forest streams

Abstract

Hyporheic zone is an active ecotone constituted by the interstitial spaces between the particles of the riverbed. The use of morphological traits can be useful to detect organisms distribution patterns in these areas. Information concerning hyporheic communities are scarce as well on chironomid vertical distribution. Fauna samples from the hyporheic zone were collected at three depths and in four microhabitats. Eighteen genera were recorded and 13 morphological traits were identified. The results indicate that the distribution patterns of hyporheic chironomid taxa vary according to depth and microhabitat. Spatial preferences for riffles habitats are evident, and the vertical distribution is correlated with morphological traits like body size, pseudopods and mentum. Faunal abundance and richness decreased with depth and the vertical distribution influenced the chironomid morphological traits. We conclude that the use of morphological trait can introduce new useful information about the distribution of hyporheic fauna.

http://zoobank.org/urn:lsid:zoobank.org:pub:E1DDF958-AA8C-40FD-A0D5-F281AA4AEA04

Keywords:

• neotropical region
• hyporheos
• mini-piezometer
• spatial distribution

Introduction

The hyporheic zone (HZ) was formally nominated by Orghidan (1959) and Käser (2010) and for this environment there is no single conceptual definition due to different terminologies, methodologies and dogma among biologists, hydrologists and geomorphologists (Smith 2005; Boulton et al. 2010). The HZ can be defined as an active ecotone constituted by the interstitial spaces between the particles of the riverbed (Gibert et al. 1990). The HZ comprises the subsurface interface between streamwater and subsurface water that comprises the saturated sediments beneath the benthic zone that exchanges water with both the surface stream and the underlying groundwater (Dahm and Valett 1996; Bencala 2000, 2005; Mugnai et al. 2015a).

Three categories of hyporheic organisms can be distinguished in the HZ: (1) stygoxenes that have no affinity with the subterranean environment and are present only accidentally; (2) stygophiles that actively exploit the resources in this environment for part of their lifecycle; and (3) stygobites that are adapted to subterranean environments and complete their lifecycle in subsurface waters (see Gibert et al. 1994; Claret et al. 1999; Malard et al. 2002). The stygophiles can be subdivided into three categories. The occasional hyporheos, species that have no affinities with the underground environment and that occur in it only accidentally, amphibite species that have a lifecycle that requires both surface and subsurface environments, as some insects that use the hyporheic zone as nursery, and the permanent hyporheos that can spend their entire lifecycle in subsurface waters. Chironomidae family as some Nearctic and Palearctic genera of Plecoptera (e.g. Paraperla Banks, 1906, Isocapnia Banks, 1938, Kathroperla Banks, 1920, and probably Paraleuctra Hanson, 1941) are classified as amphibites (Sabater and Vila 1992; Gibert et al. 1994; Berg 1995; DeWalt and Stewart 1995; Culver and Pipan 2009; Stark et al. 2013).

Insect larvae use the HZ to protect against competition or predation and as nursery and refuge from the movement of the substrate or from environmental variations due to seasonal flooding and drought (Dole-Oliver et al. 1997; Lencioni et al. 2008; James and Suren 2009; Stubbington 2012). Many studies document that chironomid larvae are ubiquitous and abundant in rivers, often contributing substantially to the energy balance of various habitats (Reynolds and Benke 2006). Chironomidae family plays an important role on transfer of energy on aquatic ecosystems by consuming organic matter and becoming an abundant prey (Serra et al. 2016). Many species are capable of using various types of substrate and several exhibit preferences for a certain substrate type (Henriques-Oliveira et al. 2003; Siqueira et al. 2008; Rosa et al. 2011). Chironomid larvae as well as other macroinvertebrates are generally confined to shallow layer of sediments, mainly the first 15 cm (Bo et al. 2006) but some species actively explore a wide vertical section of the riverbed penetrated deeper and are an important component of the hyporheic fauna ( Godbout and Hynes 1982; Bo et al. 2006; Lencioni et al. 2008).

The hyporheic fauna generally varies with depth (Malard et al. 2002), nature of the substrate that can influence animals' ability to move, settle, gather food and find shelter (Olsen et al. 2001; Omesová and Helešic 2007; Omesová et al. 2008), and hyporheic water exchange (Harvey and Wagner 2000). In the HZ, in contrast to the surface stream, the water flow is laminar and not unidirectional, and the pressure gradient generated by the flow from the irregular riverbed induces the water to move into and out of the riverbed (Thibodeaux and Boyle 1987; Hutchinson and Webster 1998). The pattern of this exchange regulates the physical and chemical conditions, determining patterns of microbial activity and the occurrence of hyporheic fauna (Franken et al. 2001; Olsen and Townsend 2003; Mugnai et al. 2015b).

Research on the HZ in Neotropics is still a challenge due to the paucity of basic information (Mugnai et al. 2015a). The ecology of many invertebrate taxa found in the HZ of Neotropical streams is almost unknown, particularly for amphibite species. In Brazil, as elsewhere in the Neotropical Region, information concerning stygoxene or stygophile species is scarce. Such information is important to understand the lifecycles of the species that occupy the HZ, which represents seminal information for conservation plans and the establishment of standards for biomonitoring programs.

This is the first study that uses Chironomidae morphological traits in response to depth in hyporheic zone. The trait approach is widely used in North America and Europe (Poff et al. 2006; Tachet et al. 2010; Serra et al. 2016), but for Chironomidae the knowledge is scarce (see Serra et al. 2016). We analyzed only Chironomidae body morphology, which did not confer functional traits. However, Chironomidae are used in monitoring programs as a measure for environmental integrity and the morphological information can be used to explain their distribution patterns.

The aim of the present study was to describe the hyporheic chironomid community and its vertical distribution in the HZ at a depth between 10 and 45 cm in a stream at Atlantic Forest in Brazil. Our hypotheses were: (a) faunal density and diversity decrease with depth; (b) the vertical distribution will influence the morphological traits composition (McGill et al. 2006); and (c) that organisms will show a preference for microhabitats, constituted by depositional areas, with higher size grains which facilitated fauna locomotion. The study also shows the performance of a new sampling methodology.

Materials and methods

Study area

The Tijuca National Park is located entirely in the urban area of the city of Rio de Janeiro (Brazil), between 22°55′ and 23°00′S and 43°11′ and 43°19′W, with an area of approximately 32 km². The vegetation is characteristic of the Atlantic Forest (Martins 2011). The climate is humid tropical with annual average temperature between 20 °C and 25 °C and an annual rainfall of >1,500 mm. The annual distribution of rain is characterized by only two seasons: the rainy season, between November and February (>250 mm/month), and the dry season, from June to September (<100 mm/month). The geological substratum type is predominantly granite (Brasil 1987).

Invertebrate samples were collected in June 2012 in two stream reaches (P I: 22°57′35.68″S, 43°16′33.54″W, 530 m altitude; P II: 22°57′13.08″S, 43°16′55.45″W, 475 m altitude), located in the first and second orders (sensu Strahler 1957) of the Tijuca River, respectively (Figure 1). The sampling sites are quite different. In the first order site (P I), boulders cover 80% of the riverbed, and sand fills the cavities between these rocks, and the transversal section of riverbed is concave. The second order site (P II) is less steep, sand represents 60% of the riverbed, the rest is constituted by cobble and coarse gravel, with regular riffles and pools, and the transversal section of the riverbed is flat.

Figure 1 Map of the study area indicating the sampling sites (P I and P II) in the Tijuca River, Tijuca National Park, Rio de Janeiro, Rio de Janeiro state, Brazil.

Sampling methodology

In each site, PVC mini-piezometers with 2.6 cm of diameter were positioned for collecting samples at three depths: 10, 25 and 45 cm. The design of a traditional piezometer (Lee and Cherry 1978; Valett 1993; Malard et al. 2002) was modified, reducing the 20 cm height of the perforated band (hole was 0.5 cm) to 5 cm to allow stratified sampling (Mugnai et al. 2015c) (Figure 2).

Figure 2 Mini-piezometers and the position of the perforated bands at the different sampling depths.

For each depth, five mini-piezometers were positioned in four different habitats: upstream of riffles (A); downstream of riffles (B); lateral side of pools (C); and in areas of sand accumulation (bars, curves) (D), amounting to 30 mini-piezometers. Each mini-piezometer was distributed at a minimum distance of 1.5 m in order to ensure the independence of the samples (Boulton and Marmonier 2007).

Samples were collected using a modified Bou-Rouch pump (Vigna Taglianti et al. 1969). For each mini-piezometer, five samples of water were collected (Malard et al. 2002; Boulton et al. 2004). To separate fine sediment, particulate organic matter (POM) and invertebrates, the samples were elutriated in the field, filtered with a 68 µm mesh, and preserved in 75% ethanol. In the laboratory, the material was stained with rose bengal for 48 h before sorting.

Identification, morphology and statistical analyses

For microscopic study, Chironomidae larvae were slide-mounted using Euparal (Epler 2001; Mugnai and Serpa-Filho 2015). Identification was made using Trivinho-Strixino (2011). Larval body length was measured from the head (excluding mandibles) to the tip of the abdomen. All individuals are deposited at the Entomological Collection of Museu Nacional/UFRJ.

For the analysis, samples are considered as replications according to Hurlbert (1984) and Magurran (2004). Comparing: three different depths (10, 25 and 45 cm) and four different habitats typologies (upstream of riffles, downstream of riffles, lateral side of pools and in areas of sand accumulation), considering each sample spatially independent. The sampling effectiveness was evaluated by a sample rarefaction test (collector curve) with genera data. The tests were performed using the program EstimateS 9.1 (Colwell 2013) and the sample rarefaction test showed that the sampling methodology for Chironomidae was efficient (Figure 3).

Figure 3 Sample rarefaction tests, error 5%, for Chironomid larvae at P I and P II sampling sites in Tijuca river, Rio de Janeiro.

Chironomidae richness and abundance (log transformed) were calculated and the values were compared among depths and habitats. To analyze morphological traits and feeding habits a database including information about body size and morpho-anatomical characters, totalizing 13 traits was done by literature revision (except for body size) (Table 1). To calculate the frequency of each morphological trait we used the species trait (binary code) and weighted by the individual abundance in each depth and habitat. We evaluated the effect of depth on richness, abundance and traits with analyses of variance (ANOVA) using Tukey test a posteriori. We added a block factor on the ANOVA, considering each sample as a block. The statistical analyses and graphics were performed with the open software package R (R Development Core Team 2013).

Table 1 Chironomidae genera and 13 morphological characteristics (traits).

							Pseudopds			Body size
Morphological traits	Elongated head	With ligula	With ligula_4teeths	Short antennae	Developed mentum	Ventromental lates	With short	With long	Without reduced	1	2	3	4
Labrundinia	1	1	0	1	0	0	0	1	0	1	1	1	0
Larsia	1	1	0	1	0	0	0	1	0	0	1	0	0
Ablabesmyia	1	1	0	1	0	0	0	1	0	1	1	1	1
Paramerina	1	1	0	1	0	0	0	1	0	0	1	0	0
Djamabatista	0	1	1	1	0	0	0	1	0	1	1	1	1
Fittkauimyia	0	1	0	1	0	1	0	1	0	0	0	0	1
Metriocnemus	0	0	0	0	1	0	0	0	1	0	1	0	0
Lopescladius	1	0	0	0	1	0	0	0	1	1	1	1	1
Ubatubaneura	1	0	0	0	1	0	0	0	1	0	1	0	0
Cricotopus	0	0	0	0	1	0	0	0	1	1	1	1	0
Corynoneura	1	0	0	0	1	0	0	0	1	1	1	1	0
Tanytarsus	0	0	0	0	1	1	1	0	0	1	1	1	0
Caladomyia	0	0	0	0	1	1	1	0	0	1	1	0	0
Polypedilum	0	0	0	1	1	1	1	0	0	0	1	1	0
Cryptochironomus	0	0	0	1	1	1	1	0	0	0	1	0	0
Phaenopsectra	0	0	0	1	1	1	1	0	0	0	1	0	0
Xestochironomus	0	0	0	1	1	1	1	0	0	0	1	0	0
Beardius	0	0	0	0	1	1	1	0	1	1	0	0	0

Results

From 30 hyporheic samples, a total of 1,069 individuals were collected. Of these individuals, 382 (36%) belonged to Insecta, 351 belonged to Crustacea and the remaining 336 were equally distributed among Hydrachnidia, Nematoda and Annelida. Diptera dominated among Insecta (334 individuals). Chironomidae represented 22% of the total fauna and 62% of the insects.

Chironomidae assemblage description

Of the 238 chironomid individuals, 199 were identified at genus level, 13 were identified at subfamily level and 26 were identified only to family level, due to the poor condition and the development stage of the individuals (Table 2).

Table 2 Abundance of Chironomid genera at different depth and habitats, and total abundance (%) for each depth.

	10 cm				25 cm				45 cm
Depth	Upstream of riffles	Downstream of riffles	Pools	Sand	Upstream of riffles	Downstream of riffles	Pools	Sand	Upstream of riffles	Downstream of riffles	Pools	Sand
Labrundinia	0	2	11	3	0	4	25	0	0	0	0	0
Larsia	0	0	2	1	0	1	1	0	0	0	0	0
Ablabesmyia	0	4	2	2	0	5	0	1	0	0	0	0
Paramerina	0	1	0	0	0	0	0	0	0	0	0	0
Djamabatista	0	0	5	0	0	4	1	0	0	0	0	0
Fittkauimyia	0	1	0	1	0	1	0	0	0	0	0	0
Metriocnemus	0	0	0	1	0	1	0	1	0	0	0	0
Lopescladius	1	3	6	8	0	3	1	2	2	0	0	4
Ubatubaneura	0	1	0	1	0	0	0	0	0	0	0	0
Cricotopus	3	0	0	2	0	4	3	2	0	0	0	1
Corynoneura	3	7	3	13	2	6	3	2	2	0	1	1
Tanytarsus	1	2	4	5	1	2	0	2	0	0	0	1
Caladomyia	0	0	1	0	0	4	0	1	0	0	0	0
Polypedilum	0	1	0	1	0	6	0	0	1	0	0	0
Cryptochironomus	0	1	0	0	0	0	0	0	0	0	0	0
Phaenopsectra	0	1	0	1	0	0	0	0	0	0	0	0
Xestochironomus	0	0	0	0	0	0	0	0	0	0	0	0
Beardius	0	0	0	1	0	0	0	0	0	0	0	0
Total for each depth	98 (49%)				88 (44%)				13 (7%)

Seventeen genera were found at a depth of 10 cm. Specifically, 15 genera were found at sampling site P I (Ablabesmyia Johannsen, 1905; Beardius Reiss & Sublette, 1985; Caladomyia Säwedal, 1981; Corynoneura Winnertz, 1846; Cricotopus van der Wulp, 1874; Djalmabatista Fittkau, 1968; Fittkauimyia Karunakaran, 1969; Labrundinia Fittkau, 1962; Larsia Fittkau, 1962; Lopescladius Oliveira, 1967; Metriocnemus van der Wulp, 1874; Phaenopsectra Kieffer, 1921; Polypedilum Kieffer, 1912; Tanytarsus van der Wulp, 1874; and Ubatubaneura Wiedenbrug & Trivinho-Strixino, 2009) and 11 genera were found at sampling site P II (Ablabesmyia; Corynoneura; Cricotopus; Cryptochironomus Kieffer, 1918; Djalmabatista; Labrundinia; Larsia; Lopescladius; Paramerina Fittkau, 1962; Polypedilum; and Tanytarsus).

Eleven genera were found at a depth of 25 cm. Seven genera were found at sampling site P I (Caladomyia, Corynoneura, Cricotopus, Djalmabatista, Lopescladius, Metriocnemus, Polypedilum, Tanytarsus, and Xestochironomus) and 10 genera were found at sampling site P II (Ablabesmyia, Corynoneura, Cricotopus, Djalmabatista, Labrundinia, Larsia, Lopescladius, Polypedilum, and Tanytarsus).

At a depth of 45 cm, 17 individuals were found, seven at P I and 10 at P II. All individuals, except one Chironominae (Tanytarsus), were Orthocladiinae. At P I, four individuals of Corynoneura sp. and three individuals of Lopescladius sp. were found. The individuals were found in microhabitats A, C and D. At P II, three individuals of Lopescladius sp., one Cricotopus sp. and one Tanytarsus sp. were found. All of them were found in areas of sand accumulation (habitat D).

The dimensions of individuals ranged from 0.5 to 4.5 mm, with a mean of 1.57 ± 0.68 mm. Corynoneura and Lopescladius larvae of all sizes were present at all sediment depths. At sampling site P I within a depth of 45 cm, the four individuals of Corynoneura sp. ranged between 1 and 3 mm long and three individuals of Lopescladius sp. ranged between 1.0 and 3.0 mm long. At sampling site P II, three individuals of Lopescladius ranged between 2.5 and 3.0 mm long, one Cricotopus sp. was 1.0 mm long and one Tanytarsus sp. was 2.0 mm long.

The genera Beardius, Metriocnemus, Phaenopsectra, Ubatubaneura and Xestochironomus were found only at P I and Cryptochironomus and Paramerina only at P II. All of these genera were represented by two individuals, except Metriocnemus, which was represented by four individuals.

Chironomidae assemblage structure

Richness and abundance were higher at 10 cm depth (F = 5.19, p = 0.006 and F = 3.46, p = 0.04, respectively (block = p > 0.05) (Figure 4A, B, respectively). Richness was lower upstream riffles (habitat A) (F_3,16 =3.08, p = 0.05, Figure 5).

Figure 4 A, richness and B, abundance of chironomid individuals at different depths and sampling sites in Tijuca River, Rio de Janeiro. Different lowercased letters show significative differences.

Figure 5 Richness at different microhabitats at sampling sites in Tijuca River, Rio de Janeiro. A, upstream of riffles; B, downstream of riffles; C, lateral side of pools; D, areas of sand accumulation (bars, curves). Different lowercased letters show significant differences.

Analysis of functional traits showed that functional diversity is higher at 45 cm depth, because presented less variation. Individuals found at shallow depth (10 cm) with posterior pseudopods reduced or absent, elongated head and mentum developed were more common in samples from 10, than in the 25 and 45 cm. For 13 traits that we measure, only four were influenced by depth: head elongated, body size, developed mentum and posterior pseudopods reduced or absent (Figure 6).

Figure 6 Percentage of chironomid morphological characteristics on different depths at sampling sites in Tijuca River, Rio de Janeiro. A, body size; B, elongated head; C, mentum present and developed versus depth; D, posterior pseudopods reduced or absent versus depth.

Discussion

The family Chironomidae consists of approximately 20,000 species (Ferrington 2008) with 11 subfamilies, five of which are present in Brazil. In the state of Rio de Janeiro, 64 genera occur in the subfamilies Chironominae (35 genera), Orthocladiinae (18), Tanypodinae (10) and Telmatogetoninae (1) (Nessimian et al. 2003). In this survey, the presence of Chironomidae in the HZ was confirmed for 18 genera. Regarding the fauna composition, our results contrast with research on HZ Chironomidae distribution done in other countries, particularly in the shallow sediments that indicates Chironominae as the most abundant and diverse subfamily and frequently predominant (e.g. Ford 1962; Morris and Brooker 1979; Pinder 1995; Sherfy et al. 2000; Lencioni 2004). Moreover, results are in agreement with findings reported by Henriques-Oliveira et al. (2003) that worked in surface sediments of streams in the Tijuca National Park and found Orthocladiinae as dominant in all substrates. The same results were found by Lencioni et al. (2008), who studied the hyporheos in an Alpine stream in Italy.

Similar to epibenthic fauna, hyporheic fauna vary along longitudinal gradients, particularly if the order covaries with altitude, hydraulic condition and substrate granulometry (e.g. Pinder 1995; Principe et al. 2008; Puntí et al. 2009). All this factors influenced by the inclination and concavity of the riverbed and consequently causing changes in species assemblages; this last varying increasing downstream in both density and diversity (Anderson et al. 2005). The surface Orthocladiinae are easily found in rapids and riffles, whereas Chironominae are found in pools in lowlands or lentic waters (Pinder 1986, 1995).

In relation to the vertical distribution, two of the general hypotheses, fauna density and diversity decreasing with depth, were confirmed. For Chironomidae, some authors (e.g. Coffman and Ferrington 1996; Sherfy et al. 2000) report that vertical distribution is related to the instar. The genera Corynoneura and Lopescladius, for example, were present at all three depths and were dominant at 45 cm depth, where individuals of all sizes occurred. The genera Labrundinia was present until a depth of 25 cm and varied in size between 1.0 and 2.7 mm at a depth of 10 cm and between 1 and 2.5 mm at a depth of 25 cm.

Moreover, the study of traits allows us to score species along a continuum of dissimilarity (Pinder 1995; McGill et al. 2006; Petchey and Gaston 2006) and shows other relationships with environmental factors. Four traits were influenced by depth: head elongated, body size, developed mentum and posterior pseudopods reduced or absent. These four traits probably determine the distribution of chironomidae on hyphoreic zone. We can infer that in shallow depth, organisms had longer body, probably because it is easy for large organisms stay in this zone. If organisms need to go deep on hyporheic zone, the pseudopods would help and in shallow depths we detect more chironomidae without pseudopods. Chironomidae with developed mentum were most abundant in shallow zones due to availability of food resources that were higher in shallow than in deep zones. Omesová and Helešic (2007) and Omesová et al. (2008) showed that the distribution of hyporheic fauna is influenced by size, form, appendages and flexibility. We can infer that to reach deeper layers the different genera of chironomidae developed a variety of characteristics for adaptation to deeper depths. Each organism has a different type of morphological body trait which allows them to remain at this depth. Bo et al. (2006), for example, found small or medium-sized organisms, short-lived crawlers, with aquatic respiration and flexible, cylindrical shaped or elongated bodies as the most common attributes of taxa found in the subsurface zone.

At the local scale, factors such as riparian vegetation, environmental quality, water temperature, hydraulic conditions and grain size influence the spatial distribution and species assemblages of epibenthic macroinvertebrates (e.g. Rossaro 1991; Jacobsen et al. 1997; Roque et al. 2003; Kleine and Trivinho-Strixino 2005; McKie et al. 2005; Sonoda et al. 2009; Reynolds and Benke 2012). In relation to the microhabitat distribution B and C showed higher richness. This can be due to two main factors. First, the coarse sediment that provided a microhabitat with large interstitial spaces and a major supply of oxygen and nutrients as suggested by Reynolds and Benke (2012) who found different chironomid productivity in different substrates. Second, the hydraulic conditions of the stream environment (Buffagni et al. 2010). Dent et al. (2000) reported that different points of the stream are different in relation to hyporheic exchange according to the local geomorphologic structure. In our case, microhabitats A are preferential local of upwelling and B, C and D of downwelling. The hyporheic fauna is strongly influenced by the hyporheic exchanges, characterized principally by direction and strength of flux (Hahn 2006). The downwelling surface water and the upwelling hyporheic water zones differ significantly in terms of the temperature, pH, redox potential, and the dissolved oxygen and nitrate levels (Brunke and Gonser 1997; Franken et al. 2001). In general, downwelling waters have high dissolved oxygen, organic matter, nutrients and subsurface fauna. Conversely, upwelling waters have low dissolved oxygen, organic matter, nutrients and subsurface or underground fauna. Because of these characteristics the richness was low in habitat A.

In relation to feeding habits, not included in the analyses, some authors (e.g. Berg 1995; Sanseverino and Nessimian 2008) have reported that the majority of chironomid larvae are generalist and nonselective feeders, ingesting food items in the proportion they occur in the surrounding water. According to Berg (1995), many factors such as larval size, quality and type of sediment influence the feeding behavior of chironomid larvae. Most groups that are predators, such as Tanypodinae, are present in the upper layers. In relation to the feeding habits, the five genera found at 45 cm depth have the similar diets including microalgae and detritus (Henriques-Oliveira et al. 2003; Saito and Fonseca-Gessner 2014).

Studies of hyporheic fauna and ecology have undoubtedly been slowed by the fact that quantitative sampling of the hyporheic zone is considerably more difficult than surface sampling in streams (Reynolds and Benke 2012). Sampling methods for studying vertical distribution include coring (Sherfy et al. 2000), freezing coring (Pugsley and Hynes 1983; Marchant 1988), are all developed for potamal habitats (Lencioni et al. 2008), colonization samplers and pumping methods (Mugnai et al. 2015a; Reynolds and Benke 2012). Some have been criticized because of disturbance during installation and removal, loss of animals by leakage during removal, use of unnatural substrata and high effort in the field or financial cost (Reynolds and Benke 2012). The modified mini-piezometers presented here are efficient as shown by the sample rarefaction test, are low cost, allowing seasonal samplings in the same point and allowing an alternative method for collecting stratified samples.

Conclusion

The present work represents the first attempt to study the chironomid community and its vertical distribution in the HZ in Neotropical streams. The study also shows sampling performance with a new methodology. Human activity can strongly influence the HZ, not only with water pollution, but also, for example, with deforestation that can cause clogging with fine sand infiltration in the HZ (Pinder 1995; Hancock 2002; Boulton and Marmonier 2007). This can limit the hyporheic exchange, thereby reducing biodiversity and causing extinction of the amphibite species (Malard et al. 2002; Bencala 2005). Finally, as we predicted, faunal abundance and richness decreased with depth and the vertical distribution influenced the chironomid morphological traits. The use of morphological trait can introduce new information about the distribution of hyporheic fauna and about dynamics and ecology of hyporheic zone. We conclude that more studies are necessary for detecting patterns of Chironomidae community structure and composition in the hyporheic zone.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by CAPES and FAPERJ under Grant no. 87756.