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High species diversity and low density typify drift and benthos composition in Neotropical streams

Javier Loboacuten-Cerviaacute 1 Carla Ferreira Rezende 2 and Claudia Castellanos 3

With 5 figures and 3 tables

Abstract We hypothesized that Neotropical streams might exhibit higher drift and benthos densities than their Palearctic counterparts in order to sustain the high diversity of drift-and benthos-feeding fish species that typify this vast region We assessed drift and benthos composition in two pristine streams deemed to represent the two less documented Neotropical regions Rio Amazonas (ie Yahuarcaca) and Coastal Serra do Mar (ie Mato Grosso) Four monthly benthos and drift samples were collected over diel cycles in the rainy and dry seasons Although the two streams showed remarkably low drift and benthos densities in Mato Grosso benthos density was mark-edly higher The same aquatic families predominate in the drift and benthos of the two streams High taxonomic richness low drift density consistent diel cycles with a peak just after dusk higher density during the night and temporal changes unrelated to seasonality typify drift composition of the two streams Although drift densities were lower in Yahuarcaca the dominant families did exhibit drift behavior with two drift peaks at night In Mato Grosso only Baetidae showed such behavioral drift with density peaks at night other families demonstrated passive drift Overall these results refute our hypothesis that Neotropical streams should exhibit higher drift and benthos densi-ties Actually these pristine streams show among the lowest drift and benthos density values worldwide

Key words Invertebrates terrestrial components streams Neotropics Serra do Mar Amazonas

Authorsrsquo addresses1 Museo Nacional de Ciencias Naturales (CSIC) C Joseacute Gutieacuterrez Abascal 2 Madrid 28006 Spain2 Universidade Federal do Cearaacute Campus do Pici Centro de Ciecircncias Bloco 909 Laboratoacuterio de Ecologia de Rios do Semiaacuterido

Departamento de Biologia Fortaleza 6021 Brazil3 Universidad Complutense de Madrid Facultad de Biologiacutea PhD Conservation Biology Corresponding author MCNL178mncncsices

Fundam Appl Limnol Vol 1812 129ndash142 ArticleStuttgart August 2012

copy 2012 E Schweizerbartrsquosche Verlagsbuchhandlung Stuttgart Germany wwwschweizerbartdeDOI 1011271863-913520120242 1863-9135120242 $ 350

Introduction

Drift the ldquodownstream transport of organisms in the water currentrdquo (Waters 1972) is a common phenom-enon in lotic systems It is largely considered a chro-no-biological phenomenon as well as a mechanism of colonization (Muumlller 1974) distribution and disper-sion of benthic fauna (Waters 1972 Brittain amp Eike-land 1988) Importantly drift serves as a major food resource for a broad array of vertebrate and inverte-brate predators (Allan 1982 Bailey 1981 McIntosh et al 1999 2002 Miyasaka amp Nakano 2001 Richmond amp Lansenby 2006)

Drift composition has been widely documented in temperate streams of Palearctic and Nearctic re-gions (for reviews see Brittain amp Eikeland 1988 Svendsen et al 2004) where drifting organisms are abundant and vary widely in species and size com-position (Muumlller 1954 1974 Waters 1972 Brittain amp Eikeland 1988 Hieber et al 2003) Dominant biotic factors associated with variations in drift composition over scales of space and time include species-specific phenology life history (OrsquoHop amp Wallace 1983 Cel-lot 1996) dispersion (Minshall amp Petersen 1985) re-source quality and availability (Brittain amp Eikeland 1988) intra- and inter-specific competition (Elliott

eschweizerbart_XXX

130 Javier Loboacuten-Cerviaacute Carla Ferreira Rezende and Claudia Castellanos

1968 Waters 1972 Bailey 1981 Rader amp McArthur 1995) and predation (Allan 1981 1982 Wilzbach et al 1986 Flecker 1990 Kratz 1996) Abiotic factors may also be important and include stream water cur-rent (Elliott 1968 Waters 1972 Fonseca amp Hart 1996 Gibbins et al 2005) discharge (Hemsworth amp Brook-er 1979 Lancaster 1992 Schreiber 1995 Rincoacuten amp Loboacuten-Cerviaacute 1997) temperature (Williams 1990 Winterbottom et al 1997 Hay et al 2008 Carolli et al 2011) photoperiod (Waters 1962 Muumlller 1963 Cowell amp Carew 1976 Nakano et al 1999) associ-ated shear stress (Gibbins et al 2005 2007 2010) sediment load (Walton 1978 Culp et al 1986 Bond amp Downes 2003) and human-induced alterations (Svendsen et al 2004)

Only a few studies have focused on Neotropi-cal stream drift (Bishop amp Hynes 1969 Ramiacuterez amp Pringle 1998 2001 Callisto amp Goulart 2005) Without exception these studies support behavioral mecha-nisms of avoidance to fish predation as the underlying mechanism of drift variation (Flecker 1992 Boyero amp Bosch 2002) However several experimental stud-ies have suggested that vertebrate predation may af-fect invertebrate drift in different ways For example drift density may increase in response to invertebrate predators and decrease in response to fish abundance (Svendsen et al 2004) Also in the wild benthic or drift-feeding fish predators may affect drift rates prey can significantly decrease activities such as crawling rate and emergence from refuge habitat in the pres-

ence of benthic predators (Dahl amp Greenberg 1996 Wooster amp Sih 1995)

Neotropical streams are inhabited by a high di-versity of fish species including a variety of feeding modes and predatory behaviours (Stout amp Vandermeer 1975 Sazima 1986 Mojica et al 2009) The scarcity of studies in this region cast doubt about whether drift patterns are actually consistent across the bewildering diversity of streams flowing in the vast Neotropical continent that in turn are inhabited by a remarkably high diversity of invertebrates and drift-feeding fishes (Stout amp Vandermeer 1975 Mojica et al 2009) This led us to hypothesize that Neotropical streams might show higher drift densities than their Palearctic coun-terparts to maintain the high diversity of drift-and benthos-feeding fishes that typify that region To this aim we examined benthos and drift composition in two streams deemed to represent two pristine ecosys-tems of the Neotropical region namely Rio Amazonas (Colombia) and Serra do Mar in southern Brazil

The study streams

This study focused on two streams flowing along two major pristine Neotropical regions Stream 1 named Yahuarcaca is located in the central reaches of Rio Amazonas (Leticia Colombia) Stream 2 named Mato Grosso is located in the coastal region of Serra do Mar (Rio de Janeiro southeast Brazil)

Table 1 Physico-chemical characteristics and sustrate composition of the two study streams at the time of sampling Mato Grosso in Rio de Janeiro (Serra do Mar southeast Brazil) and Yahuarcaca a Terra firme stream tributary of Rio Amazonas (Leticia Colom-bia) ND is no data available

Mato Grosso Yahuarcaca Dec-06 Apr-07 Jul-07 Oct-07 Dec-06 Apr-07 Jul-07 Oct-07

pH nd nd nd nd 56 45 50 53Conductivity (microS cmndash1) 736 750 791 706 205 122 414 214Temperature (degC) 229 223 180 197 252 250 252 257Water current (m sndash1) 02 05 03 02 05 05 02 03Discharge (m3 sndash1) 75 21 30 31 13 42 04 11Mean depth (cm) 016 010 011 015 03 06 02 04Mean width (m) 174 83 109 96 83 141 80 75

Substrate compositionLeaf litter 21 74 166 106 0 120 330 470Submerged roots 17 16 00 19 0 0 0 0Submerged trunks 0 0 0 0 0 60 220 0Cobble 12 85 0 0 0 0 0 0Boulder 450 273 560 341 0 0 0 0Pebble 209 118 61 132 0 0 0 0Sand 292 436 214 404 880 350 330 400Mud 0 0 0 0 120 470 120 130

eschweizerbart_XXX

131Drift and benthos composition in Neotropical streams

Yahuarcaca is located at the meeting point between Brazil Colombia and Peru (4deg 22prime S 69deg 94prime W) some 3500 km upstream of Rio Amazonas mouth This pris-tine region is fully covered by Amazonian Hyalea for-est and is characterized by a warm climate year round with a rainy season (November ndash May) followed by a dry season (June ndash October) (Galvis et al 2006) Yahuarcaca is a typical Terra firme stream flowing directly into the main stem of Rio Amazonas primeTerra firmeprime refers to those streams whose discharge depends entirely on rainfall and are not affected by the seasonal flood pulses that typify the annual hydrological cycle of Rio Amazonas and its larger tributaries (Lowe-McConnell 1987 Junk et al 1989) Run-off over geo-logically old soil virtually free of electrolytes causes the low conductivity of Terra firme streams In turn high concentrations of humic and fulvic acids derived from decomposition of organic forest matter in pod-zolic soils are responsible for their low pH and dark water color (Sioli 1967 Lowe-McConnell 1987 Mc-Clain amp Elsenbeer 2001) The Yahuarcaca substratum is primarily composed of sand wood and leaf litter Its major characteristics are shown in Table 1

The Serra do Mar mountainous corridor of coastal Brazil contains a complex network of streams that originate at rather high altitudes (asymp 1000 m asl) and flow east over basalt bedrock through pristine Mata Atlacircntica forest towards the Atlantic Ocean A rainy season (October ndash March) followed by a dry season (April ndash September) also characterizes this region but relative to the central Rio Amazonia the Serra do Mar shows a seasonal thermal regime with monthly tem-peratures ranging from an average of 18 degC in winter (June ndash July) to 229 degC in the summer (January) For the purpose of this study we selected a third order stream of clear and well oxygenated waters named Mato Grosso located asymp 70 km North of Rio de Ja-neiro (22deg 55prime S 42deg 35prime W) The study site covered by abundant riparian vegetation (ie canopy) was located at the uppermost stream reaches Unlike the Amazonian stream the substratum of Mato Grosso is composed of stones gravel and pebbles The study site ranged from 96 to 174 m width and le 010 cm depth Further details of study site are shown in Table 1

Methods

Benthos and drift were collected four times a year in the two streams Sampling was conducted in December 2006 and October 2007 (rainy season in the two localities) July 2007 (dry season in the two localities) and April 2007 (dry season in Mato Grosso and rainy season in Yahuarcaca) Given major

difference in depth between the two streams drift samples were collected using slightly different methods In Yahuarcaca drift-nets were 40 times 30 cm and 10 m long with a 270 microm mesh and 250 ml collecting bottles These were set partially submerged in the water column In Mato Grosso framed nets 20 times 20 cm 12 m long with a 250 microm mesh and 250 ml collecting bottles were fixed near the substratum just at the end of a riffle In both of them nets were set at a mid-distance from the banks in replicate to facilitate comparisons among samples and streams (Allan amp Russek 1985) The replicate nets were positioned side by side at 1000 h (daylight) 1400 h (daylight) 1800 h (dusk or early night) 0000 h (night) and 0500 h (night) for 30 min-utes Current velocity was measured at the mouth of the nets with a Global Water FP-1010 current meter before and after every collection The wet area of each net was also measured In total 80 drift samples were collected 10 drift samples col-lected per day (2 nets 5 collection times) on 4 sampling dates in both streams

Benthos samples were collected asymp 200 m upstream of the drift sampling sites Because of the differences in substrate composition (sandy Yahuarcaca vs stony Mato Grosso) we used stream-specific sampling strategies In sandy Yahuarcaca benthos was quantified with two simultaneous samples per date represented by a 6 m long transect where asymp 4 cm of substrate was sieved using a framed net (40 times 30 cm 270 microm mesh) to-taling eight benthos samples during the study period In stony Mato Grosso benthos was collected with a standard Surber (20 times 20 cm 250 microm mesh) framed with a 250 mm mesh net on the top to prevent the entry of drifting organisms A stratified sample consisted of 30 Surber units per sampling occasion divided randomly into 10 samples for each type of substrate (pebble sand and leaf litter) for a total of 120 samples On each sampling date we also measured water temperature water cur-rent and conductivity with an YSI Model 30 Handheld Salinity Conductivity amp Temperature System

All samples were preserved in 90 ethanol In the labo-ratory invertebrates were sorted identified and counted under a binocular microscope Invertebrates were identified to the highest possible resolution typically family using Merrit amp Cummins (1996) Melo (2003) and Borror et al (2004) Terres-trial invertebrates and terrestrial stages of aquatic forms were grouped into the category ldquoterrestrial taxardquo Larvae and adult stages of aquatic invertebrates were analyzed separately be-cause their different behaviors were expected to influence drift (Borror et al 2004)

Data analysis

Drift density was expressed as the number of individuals col-lected per cubic meter of water sampled (ind mndash 3) calculated by the volume of water sampled from the wet area of the nets (m2) mean water velocity at the netrsquos mouth (m sndash1) and sam-pling duration (s) For comparative purposes benthos density was expressed as the number of individuals collected per square meter (ind mndash 2) The relationship between the benthos vs drift composition was assessed with a propensity index dividing drift density by benthic density for each sampling month and stream (McIntosh et al 2002 Wilcox et al 2008)

Normality and homogeneity of variance were tested with Kolmogorov-Smirnov and Levene tests Overall the data did not meet these assumptions Therefore differences in the drift densities among months were tested with a Kruskal-Wallis non-parametric analysis followed by Dunnrsquos post-hoc test (Zar

eschweizerbart_XXX


1984) Environmental variables were compared with an Analy-sis of t Variance (ie ANOVA) only for Yahuarcaca because no replicates were available for Mato Grosso To detect patterns of drift composition hierarchical cluster analyses based on an un-weighted pair-group method algorithm (UPGMA) and Bray-Curtis index (as a similarity measurement of pair-wise samples) were applied to the Log10 + 1-transformed densities of the most common taxa (gt 5 in each sample)

Results

The study streams differed substantially from each other (Table 1) The sandy Yahuarcaca showed dif-ferences in water velocity discharge and conductiv-ity among sampling dates The stony Mato Grosso showed higher conductivity and discharge that in turn varied widely among seasons (Table 1)

In Yahuarcaca the benthos collections over sea-sons were represented by only 347 individuals belong-ing to 31 families (Table 2) Chironomidae Baetidae Elmidae and Leptophlebiidae dominated and account-ed for 67 of the total Concurrently this stream showed very low benthos densities with a mean aver-aged across seasons of only 18 ind mndash 2 Moreover weak temporal variations in benthos density appeared unrelated to the season as indicated by the fact that the lowest densities were recorded in opposing months and seasons ie 50 ind mndash 2 in the rainy December and 25 ind mndash 2 in the dry July (Table 2)

Fig 1 Relative abundance (in ) of dominant families in the benthos and drift over sampling months in (a) Mato Grosso (Serra do Mar Rio de Janeiro Brazil) and (b) Yahuarcaca (Am-azonas Leticia Colombia)

Fig 2 Mean drift density (indmndash 3 plusmn 1 SE) across sampling months (a) Mato Grosso (Mata Atlacircntica Rio de Janeiro Bra-zil) and (b) Yahuarcaca (Rio Amazonas Leticia Colombia) (bars plusmn SE)

eschweizerbart_XXX


Table 2 Benthos composition and densiy (mean ind mndash2) across sampling months in the two study streams Mato Grosso (Serra do Mar Brazil) and Yahuarcaca (Amazonas Colombia)

Mato Grosso YahuarcacaDec-06 Apr-07 Jul-07 Oct-07 Mean Dec-06 Apr-07 Jul-07 Oct-07 Mean

DipteraCeratopogonidae 02 004 06 02 02 13 04 05Chironomidae 235 309 260 768 393 19 88 19 188 79Dixidae 01 003 0Empididae 03 01 03 10 04 0Simuliidae 893 10 134 2919 989 0Tipulidae 004 01 01 01 17 04EphemeropteraBaetidae 135 26 39 440 160 04 50 14Euthyplociidae 0 02 005Leptohyphidae 05 07 26 18 14 0Leptophlebiidae 15 83 09 49 39 06 40 27 12Polymitarcyidae 0 02 005TrichopteraCalamoceratidae 04 01 02 005Glossosomatidae 004 001 02 04 02Helicopsychidae 01 02 03 02 02 005Hydrobiosidae 01 003 0Hydropsychidae 13 23 16 42 24 02 005Hydroptilidae 05 07 18 08 0Leptoceridae 16 20 26 54 29 02 005Philopotamidae 004 01 01 01 01 0Polycentropodidae 0 02 04 02PlecopteraGripopterygidae 03 01 14 10 07 0Perlidae 09 01 47 29 22 04 01ColeopteraDytiscidae 02 005Elmidae (L) 61 33 40 202 84 08 21 04 21 13Elmidae (A) 20 08 94 65 47 02 02 02Hydrophilidae 0 02 005Lutrochidae 0 02 005Ptilodactylidae 0 02 005Scirtidae 0 04 01OdonataAnisoptera 004 07 02 01 03 0Gomphidae 0 04 02 02Zygoptera 004 01 03 01 0LepidopteraPyralidae 004 001 0HemipteraCorixidae 08 02Veliidae 004 01 01 01 0Cyclopoida 0Cyclopidae 06 02DecapodaPalaemonidae (L) 01 04 02 04 03 02 33 09Trichodactylidae 01 01 004 03 01 0HaplotaxidaNaididae 0 04 15 05AcariAcari 0 15 04ArguloidaArgulidae 0 02 005BasommatophoraAncylidae 0 15 04MesogastropodaAmpullaridae 0 04 01Hydrobiidae 0 02 02 01OstracodaOstracoda 0 27 07

Density (ind mndash 2) 1422 540 735 4646 1836 50 263 25 379 179

eschweizerbart_XXX


Also in Yahuarcaca drift composition was repre-sented by only 808 individuals belonging to 42 fami-lies (Table 3) Chironomidae Baetidae and Elmidae dominated all samples and accounted for 63 of the total Aquatic invertebrates dominated drift compo-sition whereas terrestrial organisms were rare with very low contributions across samples (asymp 4 Table 3) Concurrently drift density was very low with a mean averaged across seasons of only 05 ind mndash 3 These collections highlighted lowest and highest drift densities in two rainy months April and December respectively (Table 3) with no consistent seasonal pat-tern (H = 256 p = 046) since lowest densities were recorded in rainy April and dry July (Fig 2b)

A cluster analyses for Yahuarcaca drift highlighted five groups of samples related to the diel cycles Groups 1 and 2 included all night samples characterized by higher densities whereas groups 3 to 5 includ-ed all diurnal samples with lower densities (Fig 3b) The pattern of drift density is characterized by lower density during daylight hours (ie from 1000 h to 1400 h) a peak just after dusk (1800 h) and a decline during the night (Fig 4) Dominant families tracked exactly the diel pattern for total density (Fig 5b) Chi-ronomidae density increased gt 13 times from 1400 h to 1800 h in December 2006 (from 006 to 082 ind mndash 3) and gt 20 times from 1400 h to 1800 h in October 2007 (from 003 to 062 ind mndash 3) decreasing gradu-ally to reach the lowest density at midnight in the two months Baetidae density increased asymp 60 times from 1400 h to 1800 h in October 2007 (from 0 to 058 ind mndash 3) decreasing gradually to reach the lowest density at 0500 h (night) Also Elmidae density increased gt 40 times from 1400 h to 1800 h in December 2006 (from 003 to 062 ind mndash 3) gradually decreasing to reach the lowest density at midnight

In Yahuarcaca the density of the dominant families did not show a common pattern in the composition of benthos and drift Whilst Chironomidae and Elmidae contributed similarly to both benthos and drift Lep-tophlebiidae dominated the benthos whereas Baetidae dominated the drift Nevertheless there was an appar-ent relationship between invertebrate life stages and the proportion in the benthos and drift The propor-tion of Chironomidae pupae was higher than the pro-portion of larvae in the drift whereas the proportion of Elmidae larvae was higher than the proportion of adults in the drift (Fig 1b)

Markedly higher was the benthos of Mato Grosso with a total of 9825 individuals belonging to 26 fami-lies (Table 2) Immature stages of Simuliidae Chi-ronomidae Baetidae and Elmidae accounted for 91

of the total with a mean averaged among months of 184 ind mndash 2

Unlike Yahuarcaca in Mato Grosso temporal dif-ferences in benthos density appeared related to the season with markedly low values during the dry sea-son (54 and 735 ind mndash 2 in April and July respective-ly) and higher values during the rainy season (1422 and 4646 ind mndash 2 in December and October respec-tively)

In Mato Grosso drift samples collected a total of 4352 individuals belonging to 24 families that were also represented by immature stages but included Elmidae adults as well (Table 3) Chironomidae Sim-uliidae Baetidae and Elmidae were dominant across samples and accounted for 74 of the total Aquatic invertebrates dominated the drift composition whereas terrestrial invertebrates were scarcely represented with a contribution of lt 1 over the seasons (Table 3) Drift density averaged among months was only 011 ind mndash 3 yet there were significant (H = 828 p = 004) differences among months more specifically between two dry months April (003 ind mndash 3) and July (018 ind mndash 3) (Dunn test p lt 005) (Table 3 Fig 2a)

A cluster analyses for Mato Grosso drift highlight-ed three groups related to both seasonality and diel cycles (Fig 3a) Group 1 included daylight samples with a predominance of Hydroptilidae Group 2 in-cluded night samples characterized by the occurrence of Leptohyphidae Veliidae and Perlidae and group 3 included only July when the proportion of organisms were similar during day and night As in Yahuarcaca total drift density in Mato Grosso was low during day-light hours showed a peak just after dusk (1800 h) and declined during the night (Fig 4) Unlike Yahuar-caca diel variation of dominant families did not track the diel variations observed in total density although Baetidae density increased at 1800 h 0000 h and 0500 h (Fig 5a)

Drift propensity

Drift propensity was surprisingly low in the two streams It was higher in Yahuarcaca (072) than in Mato Grosso (013) although the most abundant fami-lies in both drift and benthos (Chironomidae Baeti-dae and Elmidae) did not actually show meaningful values Whilst in Mato Grosso drift propensity scored only 00003 for Chironomidae 0001 for Simuliidae 0002 for Baetidae 0001 for Elmidae larvae and 0001 for adult Elmidae in Yahuarcaca these values attained 00008 for Chironomidae 005 for Baetidae 004 for Elmidae larvae and 007 for adult Elmidae Thus all families showed lower drift propensity in Mato Gros-

eschweizerbart_XXX


Fig 3 Results of Cluster analysis for drift composition across samples quantified in (a) Mato Grosso (Serra do Mar Rio de Ja-neiro Brazil) and (b) Yahuarcaca (Amazonas Leticia Colombia) Groups indicated by numbered bars Asterisks denote samples not included in any group Letters in code samples correspond to month and numbers (1 2 3 4 and 5) refer to the time of day 1000 h (day) 1400 h (day) 1800 h (night) 000 h (night) and 500 h (night)

eschweizerbart_XXX


Table 3 Drift composition and density (mean ind mndash 3) quantified in December 2006 and April July and October 2007 in the two study streams Mato Grosso (Mata Atlacircntica Rio de Janeiro Brazil) and Yahuarcaca (Rio Amazonas Leticia Colombia)


DipteraCeratopogonidae 002 0002 0004 001Chironomidae 002 0002 001 002 0013 03 006 009 03 019Culicidae 001 0008 005 002Diptera ND 0002 0002 0008 0004Dixidae 00009 0003 0006 00004 0003Empididae 00005 0001 00006Psychodidae 00002 00002Simuliidae 003 001 007 002 0032 001 0002 001 001Tipulidae 00002 00007 00004 001 0002 001EphemeropteraBaetidae 003 0006 004 006 0034 002 0006 003 02 006Caenidae 001 0008 0002 001Euthyplociidae 0004 0004Leptohyphidae 00005 0002 001 001 0005 0002 0004 0003Leptophlebiidae 00008 0002 0005 00026 0004 0006 001 002 001Polymitarcyidae 002 0002 0008 0002 001TrichopteraCalamoceratidae 00007 00007Hydrobiosidae 00004 00004Hydropsychidae 0002 0001 0002 0004 0002 0006 0008 0008 001 001Hydroptilidae 00001 00001Leptoceridae 00002 000004 0001 0001 00005 0002 0002 0002 0002Philopotamidae 00004 0002 0001Polycentropodidae 001 0002 001PlecopteraGripopterygidae 00002 0004 0001 0002Perlidae 00002 00003 00002ColeopteraDytiscidae 001 0002 0004 001Elmidae (L) 0003 0002 0007 0006 0005 016 002 001 001 005Elmidae (A) 0003 0001 0012 0005 0005 0002 0001 0013 0008 0006Lutrochidae 003 0004 002Noteridae 0004 0004Ptilodactylidae 0004 0002 0003Scirtidae 0004 0004Staphylinidae 0002 0002 0002HemipteraGerridae 00001 00001Notonectidae 0004 0004Veliidae 0001 00001 00008 0006 0002 001 003 002OdonataCalopterygidae 0002 0002Gomphidae 001 001Libellulidae 0004 0004 0004Zygoptera 00001 00003 00002DecapodaPalaemonidae 00004 00004 0004 0004 0004 0004CyclopoidaCyclopidae 001 001HaplotaxidaEnchytraeidae 0006 0004 0002 0004Naididae 0004 0004 0004AcariAcari 0002 0002 0004 0002 0003OstracodaOstracoda 0002 0002IsopodaSphaeromatidae 0004 0004CollembolaEntomobryidae 0002 0002MegalopteraSialidae 0004 0004Corydalidae 003 003Terrestrial itemsDiplopoda 00004 00004 0008 001Hemiptera 0004 0004Hymenoptera 00002 00002 003 003Lepidoptera 0006 0003 0005Termitidae 003 003Density (ind mndash 3) 009 003 018 015 011 077 016 024 069 047

eschweizerbart_XXX


so whereas in Yahuarcaca where drift and benthos abundance were lower drift propensity showed higher values for Hydropsychidae (ie 017) and for Polymi-tarcyidae (ie 016) Although Chironomidae Simuli-idae Baetidae and Elmidae contributed substantially to drift and benthos in Mato Grosso they all showed very low levels of drift propensity because their abun-dance in the benthos was much higher than in the drift

Discussion

In this study we quantified drift and benthos composi-tion and density in two streams deemed to represent two major pristine Neotropical regions a Terra firme stream of Rio Amazonas and a stream in the coastal Serra do Mar of southeast Brazil The study streams not only differ from each other in channel structure and substratum composition but also in climatic con-

ditions The Amazonian stream is characterized by a sandy substratum with abundant leaf litter and ex-tremely low water conductivity In contrat the Serra do Mar stream exhibits a stony substrate composed by cobble boulder pebble and submerged roots To establish the ecological significance of drift it is im-portant to take into account potential differences in the structure and function of the study system as well as the range of physical and biological parameters among streams (Brittain amp Eikeland 1988) In this context our study constitutes an important effort in document-ing benthos and drift in the two most diverse and least documented streams of the vast Neotropical region characterized in turn by an invertebrate diversity rec-ognized to be higher than in any other stream world-wide (Stout amp Vandermeer 1975) and by a bewildering number of co-occurring fish species with a predomi-nance of drift-and benthos-feeding species (Mojica et al 2009)

Despite substantial differences between the two study streams the same families Baetidae Chirono-midae and Elmidae predominate in both benthos and drift The only difference was a weak contribution of Simuliidae in the benthos and drift of Yahuarcaca (asymp 1 ) This is not surprising because a low abundance of Simuliidae typifies warm slow current Amazonian streams with a sandy substrate (Hamada et al 2002)

The predominance of Baetidae Chironomidae and Elmidae in the benthos and drift of our study streams concur with findings reported for other Neotropical (Bueno et al 2003 Callisto amp Goulart 2005) and tem-perate streams (Benson amp Pearson 1987 Schreiber 1995 Cellot 1996) Moreover as highlighted in this study an overall lack of relationship between benthos and drift composition has also been reported for a di-versity of Neotropical streams (Ramiacuterez amp Pringle 1998 2001 Bishop amp Hynes 1969 Turcotte amp Harper 1982 Jacobsen amp Bojsen 2002)

A major highlight of our study was the low benthos density recorded in the two streams Although ben-thos density differed by orders of magnitude between Mato Grosso (mean = 1840 ind mndash 2) and Yahuarcaca (mean = 180 ind mndash 2) these figures are substantially lower than those reported for any other temperate or Neotropical stream For example a benthos density as high as 42300 ind mndash 2 has been reported for a US stream with coarse sediment (Wilzbach amp Cummins 1989) or 384 ndash 6961 ind mndash 2 for 12 lowland streams in Ecuador (Jacobsen amp Bojsen 2002) or 228 ndash1504 ind mndash 2 for a stream in Costa Rica (Ramiacuterez amp Pringle 1998) Nevertheless the low drift densities recorded in our streams (mean = 01 and 05 ind mndash 3 for Mato

Fig 4 Diel variation in drift density (ind mndash 3) averaged across months for the two study streams (a) Mato Grosso (Serra do Mar Rio de Janeiro Brazil) and (b) Yahuarcaca (Amazonas Leticia Colombia)

eschweizerbart_XXX


Grosso and Yahuarcaca respectively) are similar in magnitude to those reported for other Neotropical streams For example a mean of 00013 ind mndash 3 for a stream in the Brazilian ldquocerradordquo (Callisto amp Gou-lart 2005) or 05 ndash130 ind mndash 3 and 04 ndash13 ind mndash 3 for streams in Costa Rica (Pringle amp Ramiacuterez 1998 Ramiacuterez amp Pringle 2001) In turn all these drift val-ues reported for Neotropical streams are markedly lower than those reported for practically all temper-ate streams as for example 24 times 107ndash 38 times 108 ind mndash 3 reported for an Australian stream (Schreiber 1995) or a mean of 15540 ind mndash 3 for a US stream (Benke et al 1986)

Lower drift rates in Neotropical streams may be due to the occurrence of a high diversity of fishes that include numerous species feeding upon benthic and drift organisms (Sazima 1986) As suggested by Svendsen et al (2004) and Winkelmann et al (2008) in the presence of invertebrate predators macroin-vertebrates show a tendency to higher drift densities whereas in the presence of vertebrate predators mac-roinvertebrates show decreased drift densities espe-cially during the day Moreover lower drift density in the presence of benthos-feeding fishes can be in-terpreted as a lack of mechanisms to escape predators (Winkelmann et al 2008) Although fish species in

Fig 5 Mean drift density (ind mndash 3) of dominant families across diel cycles and months in (a) Mato Grosso (Serra do Mar Rio de Janeiro Brazil) and (b) Yahuarcaca (Amazonas Leticia Colombia)

eschweizerbart_XXX


Mato Grosso preferentially feed upon benthos inver-tebrates such as Baetidae and Simuliidae (Rezende et al 2011) these families do show a remarkably low drift propensity which is consistent with studies that have suggested no major effects on invertebrate drift by benthos-feeding fish (Svendsen et al 2004 Win-kelmann et al 2008)

Interestingly in the two study streams the terres-trial components of drift was definitively low with lt 1 for Mato Grosso and 4 for Yahuarcaca These results contrast markedly with the abundance of ter-restrial components occurring in the drift of streams worldwide For example 13 ndash 23 in a stream of Ec-uador (Turcotte amp Harper 1982) 16 in an Australian stream (Benson amp Pearson 1987) 15 in a stream of Spain (Rincoacuten amp Loboacuten-Cerviaacute 1997) up to a maxi-mum of asymp 80 in a stream in Virginia USA (Garman 1991) Nevertheless it is likely that the proportion of terrestrial components recorded in our Amazonian stream might be actually higher than that quantified in our samples Previous studies on the diet of drift-feed-ing fishes in Yahuarcaca highlighted that fishes inhab-iting the water-column essentially feed upon terrestrial components (Castellanos 2011) Such a predominance of terrestrial components does not match the low pro-portions observed in our samples We suggest that such inconsistency may be caused by the preying tech-nique of predatory fishes that is based on extremely rapid pick-ups of falling prey as these touch the stream water surface Such pick-ups are actually so fast that terrestrial invertebrates disappear rapidly from the water and as a consequence these organisms do not drift andor become under-represented in drift sam-ples Moreover a predominance of predatory fishes such as those in Yahuarcaca is uncommon in streams where falling terrestrial components are a major part of the drift The Nakano et al (1999) suggestion that when fish consume terrestrial invertebrates their pres-ence will be greater in the fish diet than in the drift is strongly consistent with our results Actually in our analyses of Yahuarcacarsquos drift composition we were unable to detect the presence of Formicidae despite being a major prey of all dominant co-occurring fish species in the water column (Castellanos 2011)

Increased discharge has been related to increased drift density (Flecker 1990 Flecker 1992 Lancaster 1992) Both Yahuarcaca and Mato Grosso differed in discharge among sampling dates and showed higher values in December 2006 Such increased discharge appeared to have no obvious effect on the number of benthos and drifting organisms as inferred by a over-all lack of seasonal patterns in benthos and drift den-

sity in Yahuarcaca and variations in benthos and drift densities in the Mato Grosso unrelated to changes in discharge

In contrast the photoperiod appeared to be a major driver of drift composition In the two streams drift density showed distinct diurnal vs nocturnal patterns of taxa composition with higher drift density during the night The diel patterns are also consistent with crepuscular peaks in activity as reported for several streams worldwide (Muumlller 1963 Elliott 1968 Wa-ters 1972 Hynes 1975) Several authors eg Muumlller (1963) and Waters (1972) have further reported the occurrence of a second minor peak just before dawn (ie bigemius pattern) This appears to be the case in Yahuarcaca where a second peak just before sunrise (ie at 500 h) was frequently recorded in the drift Interestingly whilst in Mato Grosso the density of the dominant families remained more or less constant throughout the day (with the exception of an increase in Baetidae density during the night) in Yahuarcaca the dominant families showed marked diel cycles with two peaks during the day

In addition several authors (Allan 1978 Flecker 1992 Pringle amp Ramiacuterez 1998) have hypothesized that in tropical streams invertebrates are nocturnal to avoid predation by vertebrate diurnal predators Our results for the Amazonian stream are inconsistent with this mechanistic hypothesis As aforementioned si-multaneous studies of feeding patterns of Yahuarcaca fishes offered compelling evidence that the dominant drift-feeding fishes do not track diel feeding activ-ity (Castellanos 2011) In Mato Grosso dominant fish species are essentially benthic feeders (Rezende et al 2011) These include Astyanax taeniatus which feed mainly on plants (Manna et al 2012) Characidium cf vidali that mainly feed upon Trichoptera and Sim-uliidae (Mazzoni et al 2012) and Pimelodella later-istriga that feeds on Chironomidae and Simuliidae (Mazzoni et al 2010) These feeding patterns indicate that a dominance of benthic feeding may be due to an absence of consistent drift diel cycles of the dominant drifting families

Actually the only consistent diel cycle recorded in Mato Grosso occurred in Baetidae whose tempo-ral fluctuations were reflected in the patterns of total drift density Unlike in Mato Grosso consistent diel patterns in Yahuarcaca drift occurred in the dominant families Chironomidae Baetidae and Elmidae In-creased drift of dominant taxa during the night results from a behavioral pattern characteristic of certain spe-cies and can be considered active drift (Muumlller 1954 Waters 1972) There is evidence that diel cycles are

eschweizerbart_XXX


determined by behavioral mechanisms of aquatic in-vertebrates (Elliott 1968 1971 Waters 1972 Skinner 1985) including species of Baetidae (Flecker 1992 Miyasaka amp Nakano 2001 Richmond amp Lasenby 2006) Chironomidae (Ferrington 1984 Skinner 1985) and Simuliidae (Donahue amp Schindler 1998) Thus our results suggest that in Neotropical streams drift is determined to some extent by behavioral strategies of the dominant taxa (ie active drift Waters 1965)

Our results definitively refute the hypothesis that Neotropical streams should exhibit higher drift and benthos densities than their temperate counterparts Consistent with other Neotropical streams Yahuar-caca and Mato Grosso showed a markedly high spe-cies diversity and low drift density Drift densities were still lower in Yahuarcaca but the dominant fami-lies showed drift behavior with two drift peaks during the night In Mato Grosso only Baetidae showed such behavioral drift with density peaks at night whereas other families demonstrated passive drift

Acknowledgements

Thanks are due to Universidad Nacional de Colombia Instituto Sinchi and Fundacioacuten Amazoniacutea Eware for field and adminis-trative support in Colombia The study of the Colombian Ama-zon was financially supported by Colciencias (Colombia) un-der contract No 126ndash2007 Claudia Castellanos was financially supported by WWF Russell E Train for Education Program fellowship Part of this study belongs to the Ph D Thesis of Carla Rezende at Universidade Federal do Rio de Janeiro and was financially supported by a Fundacioacuten Carolina scholarship (Spain) Ref Nos CNPq 140928 2005ndash7 and CAPES ndash PDEE 012008-01 Warm thanks are extended to the Spanish CYTED Program that facilitated the visits of the senior author to the study streams

References

Allan J D 1978 Trout predation and size composition of stream drift ndash Limnol Oceanogr 23 1231ndash1237

Allan J D 1981 Determinants of diet of brook trout (Salve-linus fontinalis) in a mountain stream ndash Can J Fish Aquat Sci 38 184 ndash192

Allan J D 1982 The effects of reduction in trout density on the invertebrate community of a mountain stream ndash Ecology 63 1444 ndash1445

Allan J D amp Russek E 1985 The quantification of stream drift ndash Can J Fish Aquat Sci 42 210 ndash 215

Bailey P C E 1981 Diel activity patterns in nymphs of an Australian mayfly Atalophlebioides sp (Ephemeroptera Leptophlebiidae) ndash Aust J Mar Freshwat Res 32 121ndash131

Benke A C Parsons K A amp Dhar S M 1991 Population and community patterns of invertebrate drift in an unregulat-ed coastal plain river ndash Can J Fish Aquat Sci 48 811ndash 823

Benson L J amp Pearson R G 1987 Drift and upstream move-ment in Yuccabine Creek an Autralian tropical stream ndash Hy-drobiologia 153 225 ndash 239

Bishop J E amp Hynes H B N 1969 Downstream drift of invertebrate fauna in a stream ecosystem ndash Arch Hydrobiol 66 56 ndash 60

Bond N R amp Downes B J 2003 The independent and in-teractive effects of fine sediment and flow on benthic inver-tebrate communities characteristic of small upland streams ndash Freshwat Biol 48 455 ndash 465

Borror D J Triplehorn C A amp Johnson N F 2004 In-troduction to the study of insects 6th Edition ndash Thomson Brooks Cole Belmont pp 1ndash 864

Boyero L amp Bosch J 2002 Spatial and temporal variation of macroinvertebrate drift in two neotropical streams ndash Bio-tropica 34 567ndash 574

Brittain J E amp Eikeland T J 1988 Invertebrate Drift ndash a Review ndash Hydrobiologia 166 77ndash 93

Bueno A A P Bond-Buckup G amp Ferreira B D P 2003 Estrutura da comunidade de macroinvertebrados bentocircnicos em dois cursos de aacutegua do Rio Grande do Sul Brazil ndash Rev Bras Zool 20 115 ndash125

Callisto M amp Goulart M 2005 Invertebrate drift along a lon-gitudinal gradient in a Neotropical stream in Serra do Cipo National Park Brazil ndash Hydrobiologia 539 47ndash 56

Carolli M Bruno M C Siviglia A amp Maiolini B 2011 Responses of benthic invertebrates to abrupt changes of tem-perature in flume simulations ndash Riv Res Appl doi 101002rra1520

Castellanos C 2011 Disponibilidad y uso de los recursos ali-menticios de las especies de peces que habitan la columna de agua en un riacuteo amazoacutenico de Terra firme ndash PhD Thesis Universidad Complutense de Madrid pp 1ndash184

Cellot B 1996 Influence of side-arms on aquatic macroinver-tebrate drift in the main channel of a large river ndash Freshwat Biol 35 149 ndash164

Cowell B C amp Carew W C 1976 Seasonal and diel pe-riodicity in drift of aquatic insects in a subtropical Florida stream ndash Freshwat Biol 6 587ndash 594

Culp J M Wrona F J amp Davies R W 1986 Response of stream benthos and drift to fine sediment deposition versus transport ndash Can J Zool 64 1345 ndash1351

Dahl J amp Greenberg L 1996 Impact on stream benthic prey by benthic vs drift feeding predators A meta-analysis ndash Oikos 77 177ndash181

Donahue W F amp Schindler D W 1998 Diel emigration and colonization responses of blackfly larvae (Diptera Simulii-dae) to ultraviolet radiation ndash Freshwat Biol 40 357ndash 365

Elliott J M 1968 The life histories and drifting of Trichop-tera in a Dartmoor stream ndash J Anim Ecol 37 615 ndash 625

Elliott J M 1971 Distances travelled by drifting invertebrates in a Lake District stream ndash Oecologia 6 350 ndash 379

Ferrington L C 1984 Drift dynamics of Chironomidae lar-vae 1 Preliminary results and discussion of importance of mesh size and level of taxonomic identification in resolv-ing Chironomidae diel drift patterns ndash Hydrobiologia 114 215 ndash 227

Fittkau E J 1964 Remarks on limnology of central-Amazon rain forest streams ndash Verh Internat Verein Limnol 15 1092 ndash1096

Flecker A S 1990 Community structure in Neotropical streams fish feeding guilds disturbance and influence of direct versus indirect effects of predators on their prey ndash PhD Thesis University of Maryland pp 1ndash 218

Flecker A S 1992 Fish predation and the evolution of in-vertebrate drift periodicity ndash Evidence from Neotropical streams ndash Ecology 73 438 ndash 448

eschweizerbart_XXX


Fonseca D M amp Hart D D 1996 Density-dependent dis-persal of black fly neonates is mediated by flow ndash Oikos 75 49 ndash 58

Galvis G Mojica J I Duque S R Castellanos C Saacutenchez-Duarte P Arce M Gutieacuterrez A Jimeacutenez L F Santos M Vejarano-Rivadeneira S Arbelaacuteez F Prieto E amp Leiva M (eds) 2006 Peces del medio Amazonas Regioacuten de Leticia ndash Editorial Panamericana Colombia pp 1ndash 548

Garman G C 1991 Use of terrestrial arthropod prey by a stream-dwelling Cyprinid fish ndash Environ Biol Fish 30 325 ndash 332

Gibbins C N Scott E Soulsby C amp McEwan I 2005 The relationship between sediment mobilisation and the entry of Baetis mayflies into the drift in a laboratory flume ndash Hydro-biologia 533 115 ndash122

Gibbins C Vericat D amp Batalla R J 2007 When is stream invertebrate drift catastrophic The role of hydraulics and sediment transport in initiating drift during flood events ndash Freshwat Biol 52 2369 ndash 2384

Gibbins N C Vericat D amp Ramon J B 2010 Relations between invertebrate drift and flow velocity in sand-bed and riffle habitats and the limits imposed by substrate stability and benthic density ndash J Am Benthol Soc 29 945 ndash 958

Hamada N McCreadie J W amp Adler P H 2002 Species richness and spatial distribution of blackflies (Diptera Sim-uliidae) in streams of Central Amazonia Brazil ndash Freshwat Biol 47 31ndash 40

Hay C H Thomas E Franti G David D Marx B Ed-ward E Peters J Larry E amp Hesse W 2008 Macro-invertebrate drift density in relation to abiotic factors in the Missouri River ndash Hydrobiologia 598 175 ndash189

Hemsworth R J amp Brooker M P 1979 The rate of down-stream displacement of macroinvertebrates in the upper Wye Wales Holarctic ndash Ecology 2 130 ndash136

Hieber M Robinson C T amp Uehlinger U 2003 Season-al and diel patterns of invertebrate drift in different alpine stream types ndash Freshwat Biol 48 1078 ndash1092

Hynes J D 1975 Downstream drift of invertebrates in a river in southern Ghana ndash Freshwat Biol 5 515 ndash 532

Jacobsen D amp Bojsen B 2002 Macroinvertebrate drift in Amazon streams in relation to riparian forest cover and fish fauna ndash Arch Hydrobiol 155 177ndash197

Junk W J Bayley P B amp Sparks R E 1989 The flood pulse concept in river-floodplain systems ndash Spec Publ Can J Fisher Aquat Sci 106 110 ndash127

Kratz K W 1996 Effects of stoneflies on local prey popula-tions mechanisms of impact across prey density ndash Ecology 77 1573 ndash1585

Lancaster J 1992 Diel variations in the effect of spates on mayflies (Ephemeroptera Baetis) ndash Can J ZoolRev Can Zool 70 1696 ndash1700

Lowe-McConnell R H 1987 Ecological Studies in Tropical Fish Communities ndash Cambridge University Press Cam-bridge pp 1ndash 400

Manna L R Rezende C F amp Mazzoni R 2012 Plasticity in the diet of Astyanax taeniatus in a coastal stream from Southeast Brazil ndash Braz J Biol 72(4)

Mazzoni R Pereira M M Rezende C F amp Iglesias-Rios R 2010 Diet and feeding daily rhythm of Pimelodella lateshyristriga (Osteichthyes Siluriformes) in a coastal stream from Serra do Mar ndash RJ ndash Braz J Biol 70 1123 ndash1129

Mazzoni R Marques P Rezende C F amp Iglesias-Rios R 2012 Niche enlargement as a consequence of co-existence a case study ndash Braz J Biol 72 1ndash 8

McClain M E amp Elsenbeer H 2001 Terrestrial input to Amazon streams and internal biogeochemistry processing ndash In McClain et al (eds) The biogeochemistry of the Amazon Basin ndash Oxford University Press pp 185 ndash 208

McIntosh A R Peckarsky B L amp Taylor B W 1999 Rapid size-specific changes in the drift of Baetis bicaudatus (Ephemeroptera) caused by alterations in fish odor concen-tration ndash Oecologia 118 256 ndash 264

McIntosh A R Peckarsky B L amp Taylor B W 2002 The influence of predatory fish on mayfly drift extrapolating from experiments to nature ndash Freshwat Biol 47 1497ndash1513

Melo G A S 2003 Manual de identificaccedilatildeo de crustaacutecea decapoda de aacutegua doce do Brasil ndash Loyola Satildeo Paulo pp 1ndash 429

Merrit R amp Cummins K 1996 An Introduction to the aquatic insects of North Ameacuterica3th Edition ndash KendallHunt Pub-lishing Company Iowa pp 1ndash 862

Minshall G W amp Petersen Jr R J 1985 Towards a theory of macroinvertebrate community structure in stream ecosys-tems ndash Arch Hydrobiol 104 49 ndash76

Miyasaka H amp Nakano S 2001 Drift dispersal of mayfly nymphs in the presence of chemical and visual cues from diurnal drift- and nocturnal benthic-foraging fishes ndash Fresh-wat Biol 46 1229 ndash1237

Mojica J I Castellanos C amp Loboacuten-Cerviaacute J 2009 High temporal species turnover enhances the complexity of fish assemblages in Amazonian Terra firme streams ndash Ecol Freshwat Fish 18 520 ndash 526

Muumlller K 1954 Investigations on the organic drift in North Swedish streams ndash Rep Inst Freshwat Res Drottningholm 33 133 ndash148

Muumlller K 1963 Diurnal rhythms in ldquoorganic driftrdquo of Gam-marus pulex ndash Nature London 198 806 ndash 807

Muumlller K 1974 Stream drift as a chronological phenomenon in running water ecosystems ndash Annu Rev Ecol Syst 5 309 ndash 323

Nakano S Fausch K D amp Kitano S 1999 Flexible niche partitioning via a foraging mode shift a proposed mecha-nism for coexistence in stream-dwelling chars ndash J Anim Ecol 68 1079 ndash1092

OrsquoHop J amp Wallace J B 1983 Invertebrate drift discharge and sediment relations in a southern Appalachian headwater stream ndash Hydrobiologia 98 72 ndash 84

Pringle C M amp Ramiacuterez A 1998 Use of both benthic and drift sampling techniques to assess tropical stream inverte-brate communities along an altitudinal gradient Costa Rica ndash Freshwat Biol 39 359 ndash 373

Rader R B amp McArthur J V 1995 The relative importance of refugia in determining the drift and habitat selection of predaceous stoneflies in a sandy-bottomed stream ndash Oeco-logia 103 1ndash 9

Ramiacuterez A amp Pringle C M 1998 Invertebrate drift and ben-thic community dynamics in a lowland neotropical stream Costa Rica ndash Hydrobiologia 386 19 ndash 26

Ramiacuterez A amp Pringle C M 2001 Spatial and temporal pat-terns of invertebrate drift in streams draining a Neotropical landscape ndash Freshwat Biol 46 47ndash 62

Rezende C F Mazzoni R Pellegrini E C Rodrigues D amp Maiacutera M 2011 Prey selection by two benthic fish species in a Mato Grosso stream Rio de Janeiro Brazil ndash Rev Biol Trop 59 1697ndash1706

Richmond S amp Lasenby D 2006 The behavioral response of mayfly nymphs (Stenonema sp) to chemical cues from cray-fish (Orconectes rusticus) ndash Hydrobiologia 560 335 ndash 343

eschweizerbart_XXX


Rincoacuten P A amp Loboacuten-Cerviaacute J 1997 Temporal patterns in macroinvertebrate drift in a northern Spanish stream ndash Mar Freshwater Res 48 455 ndash 464

Sazima I 1986 Similarities in Feeding-Behavior between Some Marine and Fresh-Water Fishes in two Tropical Com-munities ndash J Fish Biol 29 53 ndash 65

Schreiber E S G 1995 Long-term patterns of invertebrate stream drift in an Australian temperate stream ndash Freshwat Biol 33 13 ndash 25

Sioli H 1967 Hydrochemistry and geology in the Brazilian Amazon region ndash Amazoniana 1 267ndash 277

Skinner W D 1985 Night day drift patterns and the size of larvae of two aquatic insects ndash Hydrobiologia 124 283 ndash 285

Stout J amp Vandermeer J 1975 Comparison of species rich-ness for stream-inhabiting insects in tropical and mid-lati-tude streams ndash Am Nat 109 263 ndash 280

Svendsen C R Quinn T amp Kolbe D 2004 Review of Macroinvertebrate Drift in Lotic Ecosystems Final Report ndash Department of Environmental Conservation Wildlife Re-search Program Seattle pp 1ndash 92

Tilley L J 1989 Diel drift of Chironomidae larvae in a pris-tine Idaho mountain stream ndash Hydrobiologia 174 133 ndash149

Turcotte P amp Harper P P 1982 Drift patterns in a high An-dean stream ndash Hydrobiologia 89 141ndash151

Walton O E 1978 Substrate attachment by drifting aquatic insect larvae ndash Ecology 59 1023 ndash1030

Waters T F 1962 Diurnal periodicity in drift of stream inver-tebrates ndash Ecology 43 316 ndash 320

Waters T F 1965 Interpretation of invertebrate drift in streams ndash Ecology 46 327ndash 334

Waters T F 1972 Drift of stream insects ndash Annu Rev Ento-mol 17 253 ndash 272

Wilcox C A Peckarsky P B Taylor B W amp Encalada A C 2008 Hydraulic and geomorphic effects on mayfly drift in high-gradient streams at moderate discharges ndash Ecohy-drol 1 176 ndash186

Williams D D 1990 A field-study of the effects of water temperature discharge and trout odor on the drift of stream invertebrates ndash Arch Hydrobiol 119 167ndash181

Wilzbach M A amp Cummins K W 1989 An assessment of short-term depletion of stream macroinvertebrate benthos by drift ndash Hydrobiologia 185 29 ndash 39

Wilzbach M A Cummins K W amp Hall J D 1986 Influ-ence of habitat manipulations on interactions between cut-throat trout and invertebrate drift ndash Ecology 67 898 ndash 911

Winkelmann C Petzoldt T Koop J H Matthaei C amp Benndorf J 2008 Benthivorous fish reduce stream inver-tebrate drift in a large scale field experiment ndash Aquat Ecol 42483 ndash 493

Winterbottom J H Orton S E amp Hildrew A G 1997 Field experiments on the mobility of benthic invertebrates in a southern English stream ndash Freshwat Biol 38 37ndash 47

Wooster D amp Sih A 1995 A Review of the Drift and Activ-ity Responses of Stream Prey to Predator Presence ndash Oikos 73 3 ndash 8

Zar J H 1984 Biostatistical analysis ndash Englewood CliffsPretince Hall pp 1ndash130

Submitted 13 September 2011 accepted 5 July 2012

eschweizerbart_XXX


1968 Waters 1972 Bailey 1981 Rader amp McArthur 1995) and predation (Allan 1981 1982 Wilzbach et al 1986 Flecker 1990 Kratz 1996) Abiotic factors may also be important and include stream water cur-rent (Elliott 1968 Waters 1972 Fonseca amp Hart 1996 Gibbins et al 2005) discharge (Hemsworth amp Brook-er 1979 Lancaster 1992 Schreiber 1995 Rincoacuten amp Loboacuten-Cerviaacute 1997) temperature (Williams 1990 Winterbottom et al 1997 Hay et al 2008 Carolli et al 2011) photoperiod (Waters 1962 Muumlller 1963 Cowell amp Carew 1976 Nakano et al 1999) associ-ated shear stress (Gibbins et al 2005 2007 2010) sediment load (Walton 1978 Culp et al 1986 Bond amp Downes 2003) and human-induced alterations (Svendsen et al 2004)

Only a few studies have focused on Neotropi-cal stream drift (Bishop amp Hynes 1969 Ramiacuterez amp Pringle 1998 2001 Callisto amp Goulart 2005) Without exception these studies support behavioral mecha-nisms of avoidance to fish predation as the underlying mechanism of drift variation (Flecker 1992 Boyero amp Bosch 2002) However several experimental stud-ies have suggested that vertebrate predation may af-fect invertebrate drift in different ways For example drift density may increase in response to invertebrate predators and decrease in response to fish abundance (Svendsen et al 2004) Also in the wild benthic or drift-feeding fish predators may affect drift rates prey can significantly decrease activities such as crawling rate and emergence from refuge habitat in the pres-

ence of benthic predators (Dahl amp Greenberg 1996 Wooster amp Sih 1995)

Neotropical streams are inhabited by a high di-versity of fish species including a variety of feeding modes and predatory behaviours (Stout amp Vandermeer 1975 Sazima 1986 Mojica et al 2009) The scarcity of studies in this region cast doubt about whether drift patterns are actually consistent across the bewildering diversity of streams flowing in the vast Neotropical continent that in turn are inhabited by a remarkably high diversity of invertebrates and drift-feeding fishes (Stout amp Vandermeer 1975 Mojica et al 2009) This led us to hypothesize that Neotropical streams might show higher drift densities than their Palearctic coun-terparts to maintain the high diversity of drift-and benthos-feeding fishes that typify that region To this aim we examined benthos and drift composition in two streams deemed to represent two pristine ecosys-tems of the Neotropical region namely Rio Amazonas (Colombia) and Serra do Mar in southern Brazil

The study streams

This study focused on two streams flowing along two major pristine Neotropical regions Stream 1 named Yahuarcaca is located in the central reaches of Rio Amazonas (Leticia Colombia) Stream 2 named Mato Grosso is located in the coastal region of Serra do Mar (Rio de Janeiro southeast Brazil)

Table 1 Physico-chemical characteristics and sustrate composition of the two study streams at the time of sampling Mato Grosso in Rio de Janeiro (Serra do Mar southeast Brazil) and Yahuarcaca a Terra firme stream tributary of Rio Amazonas (Leticia Colom-bia) ND is no data available

Mato Grosso Yahuarcaca Dec-06 Apr-07 Jul-07 Oct-07 Dec-06 Apr-07 Jul-07 Oct-07

pH nd nd nd nd 56 45 50 53Conductivity (microS cmndash1) 736 750 791 706 205 122 414 214Temperature (degC) 229 223 180 197 252 250 252 257Water current (m sndash1) 02 05 03 02 05 05 02 03Discharge (m3 sndash1) 75 21 30 31 13 42 04 11Mean depth (cm) 016 010 011 015 03 06 02 04Mean width (m) 174 83 109 96 83 141 80 75

Substrate compositionLeaf litter 21 74 166 106 0 120 330 470Submerged roots 17 16 00 19 0 0 0 0Submerged trunks 0 0 0 0 0 60 220 0Cobble 12 85 0 0 0 0 0 0Boulder 450 273 560 341 0 0 0 0Pebble 209 118 61 132 0 0 0 0Sand 292 436 214 404 880 350 330 400Mud 0 0 0 0 120 470 120 130

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Download - High species diversity and low density typify drift and benthos composition in Neotropical streams

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