Macroinvertebrate community response to large-woody ... - Springer Link

Hydrobiologia (2008) 605:193–207 DOI 10.1007/s10750-008-9354-8

PRIMARY RESEARCH PAPER

Macroinvertebrate community response to large-woody debris additions in small warmwater streams Peter J. Hrodey Æ Bryan J. Kalb Æ Trent M. Sutton

Received: 11 April 2007 / Revised: 26 January 2008 / Accepted: 20 February 2008 / Published online: 5 March 2008 Ó Springer Science+Business Media B.V. 2008

Abstract Half-logs are a common restoration tool used to provide cover for fish in degraded streams. These structures may also provide a stable substrate for biofilm production and aquatic macroinvertebrate colonization. Half-logs (N = 108) were installed into nine streams of the upper Wabash River basin, Indiana, in July 2003 to examine changes in aquatic macroinvertebrate community composition and functional guilds under varying land-use types. Following installation, half-logs were colonized and showed statistically significant increases in both relative abundance and taxa richness of macroinvertebrates Handling editor: R. Bailey P. J. Hrodey B. J. Kalb T. M. Sutton Department of Forestry and Natural Resources, Purdue University, 195 Marsteller Street, West Lafayette, IN 47907, USA B. J. Kalb e-mail: [email protected] Present Address: P. J. Hrodey Annis Water Resources Institute, Grand Valley State University, 740 West Shoreline Drive, Muskegon, MI 49441, USA e-mail: [email protected] T. M. Sutton (&) School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 245 O’Neill Building, Fairbanks, AK 99775, USA e-mail: [email protected]

over time. The number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa collected from half-logs, as a percentage of total community composition, was positively related to the percentage of canopy coverage across streams and the relative abundance of shredder taxa utilizing half-logs decreased significantly with increasing canopy coverage. Forest streams exhibited significantly lower relative abundances of individuals colonizing half-logs (mean = 14.9 taxa/0.25 m2) than fallow field and agricultural streams (mean = 29.5 and 33.1, respectively). The percentage of pollution-tolerant taxa using half-logs was highest in fallow field streams (mean = 18.4%), followed by forest and agriculture systems (mean = 15.9% and 13. 9%, respectively). These results indicate that half-logs were colonized by aquatic macroinvertebrates and exhibited changes in community composition and functional feeding guilds over time and across land-use types. The extent of colonization and use of half-logs was largely dependent upon the pre-existing in-stream habitat quality and the predominant land-use type. Keywords Half-logs Large-woody debris Macroinvertebrate colonization Introduced substrate Warmwater streams

Introduction Large-woody debris (LWD) plays an important role in the function of stream ecosystems. This habitat

123

194

feature can stabilize the stream channel and dictate channel morphologies (Angermeier & Karr, 1984; Bilby & Ward, 1989; Talmage et al., 2002), regulate pool spacing (Montgomery et al., 1995), and retain organic materials (Bilby & Ward, 1989). Wood in streams also provides important habitat and flow refugia for fish and macroinvertebrates (Johnson et al., 2003). Fish seek out and use LWD as a site for spawning, resting, feeding, and hiding cover (Angermeier & Karr, 1984). Macroinvertebrates inhabit LWD because it is a stable site for colonization, serves as a refuge from currents and predators, and provides a valuable energy source (Anderson et al., 1978; Drury & Kelso, 2000). Large-woody debris creates ideal habitats for aquatic macroinvertebrates because of its large surface area and physical complexity (Anderson et al., 1978; Drury & Kelso, 2000; Rinella & Feminella, 2005). The vascular nature of LWD results in an air– water interface at capillary sites allowing for temperature and moisture gradients to develop which are beneficial to macroinvertebrate colonizers (Anderson et al., 1978). Similar to LWD, half-logs can provide a stable substrate for biofilm production and aquatic macroinvertebrate colonization. Large-woody debris is often the site for the majority of macroinvertebrate production in low-gradient, warmwater streams (Shields et al., 1995; Benke & Wallace, 2003). Aquatic macroinvertebrates use LWD for all life stages, including oviposition, nursery habitat, molting, pupation, and emergence (Anderson et al., 1978). In addition, LWD can provide resting cover, forage sites, hiding cover, and refuge from strong currents (Drury & Kelso, 2000; Benke & Wallace, 2003). Aquatic macroinvertebrates influence nutrient cycles, decomposition rates, and translocation of materials. In addition, aquatic macroinvertebrates serve as indicators of stream integrity and water quality (Wallace & Webster, 1996). Because they have rapid colonization rates and short life cycles, aquatic macroinvertebrates are ideal organisms to examine the effects of habitat manipulations in small streams. In streams dominated by agricultural land use, increased sedimentation can lead to decreased habitat heterogeneity, poor water quality, and degraded macroinvertebrate communities (Genito et al., 2002). Half-logs added to these streams could help to mitigate losses of larger, more stable substrates resulting from increased sedimentation. In

123

Hydrobiologia (2008) 605:193–207

addition, half-logs could also replace previously existing LWD habitat that has been removed during channelization. Half-logs have been shown to be an effective habitat-improvement tool for fish communities (Burgess, 1980; Hunt, 1982). However, few studies have examined the colonization and use of half-logs by macroinvertebrates in warmwater stream systems. While previous studies have shown increases in abundance, biomass, taxa richness, and diversity of macroinvertebrates associated with LWD accumulations (Armitage et al., 2001; Braccia & Batzer, 2001; Benke & Wallace, 2003; Johnson & Kennedy, 2003; Johnson et al., 2003), it is not clear if these results are applicable to macroinvertebrate colonization of halflogs. The objectives of this study were to: (1) determine the rates and patterns of aquatic macroinvertebrate colonization on half-logs; (2) examine changes in aquatic macroinvertebrate community composition on half-logs among different land-use types; and (3) document changes over time and across a disturbance gradient among aquatic macroinvertebrate functional feeding and tolerance guilds utilizing half-logs. These results will be used to make recommendations regarding riparian land-use management and in-stream habitat mitigation, and to direct future studies investigating the potential of these structures to increase stream production of fishes.

Methods Study site The Wabash River is the longest free-flowing system east of the Mississippi River, with the upper basin draining the northern third of Indiana (Fig. 1). Data for this research were collected from nine first- and second-order tributaries of the upper Wabash River (Table 1; Fig. 1). Streams in the basin are lowgradient, warmwater systems that are primarily dominated by sand substrates. Although agriculture was the predominant land-use activity in all nine watersheds (mean = 90.29%; range, 77.36–93.36%), streams were chosen with riparian areas dominated by agriculture, forest, and fallow field riparian land-use types. Agricultural sites were typically channelized ditches adjacent to row-crop (i.e., corn Zea mays and soy bean Glycine max) agriculture characterized by run


195

Fig. 1 Half-log study site locations within the upper Wabash River basin, Indiana (see Table 1 for code definitions)

N

KBC

CC

MC BC IC

GFC

TC

LPC KPC

40

0

40

80

Kilometers

Study Sites Upper Wabash River Watershed

Table 1 Half-log study streams organized by land-use type, and described by location, watershed size, mean width, the amount of fine substrates, and riparian canopy cover Fines (%)

Canopy cover (%)

Stream name

Code

County

Agriculture

Grassy Fork Creek

GFC

Howard

66.00

5.32

44.00

0.16

Keans Bay Creek

KBC

White

108.30

5.71

98.00

24.77

Turkey Creek

TC

Tipton

113.20

4.76

93.00

0.16

Burnett Creek

BC

Tippecanoe

139.10

7.59

44.00

90.55

Forested

Fallow field

Drainage area (km2)

Mean width (m)

Land-use type

Indian Creek

IC

Tippecanoe

76.70

6.18

67.00

71.75

Little Pine Creek

LPC

Warren

134.90

10.68

21.00

81.50

Crooked Creek

CC

Cass

153.80

9.26

65.00

73.70

Kickapoo Creek

KPC

Warren

116.50

6.58

15.00

75.04

Moots Creek

MC

Tippecanoe

132.60

10.29

17.00

80.41

habitat, sand-silt substrates, and little or no riparian vegetation. Forested streams had well-developed runpool sequences, sand-gravel substrates with some boulder complexes, and substantial riparian areas (i.e., [25 m riparian buffer widths). Fallow field sites were composed of heterogeneous habitat with riparian areas dominated by grasses and herbaceous plants with some larger trees adjacent to the stream. All sites examined in this study were at some degree of recovery from human perturbation (i.e., channelization, dredging, snagging, logging, clearing, and urban development) and contained little or no naturally occurring LWD.

Study design Tributaries (N = 9; 3 per land-use type) of the upper Wabash River basin were selected based on predominant riparian land use (i.e., agriculture, forest, and fallow field). Treatment sites (N = 27; 3 sites per stream) were 25 m in length and chosen based on stream depth and amount of existing cover. Half-logs (N = 108) were added to these sites (4 per site; spaced evenly within the 25 m section) in early July 2003. Half-logs were installed parallel to stream flow at or near the stream thalweg, and sites within streams were spaced 250-m apart to reduce bias (Fig. 2). The

123

196


Fig. 2 Stream diagram showing each site, half-log placement, and spacing throughout the reach

Stream flow 250m

25m

250m

5T

Stream channel 3T

1T

Study site Half-log 3T

Site number

half-log cover structure used in this study was based on a design from the Wisconsin Department of Natural Resources (Hunt, 1982). Each structure required a 30-cm diameter red pine Pinus resinosa log that was 2.6-m long (split lengthwise), two 15-cm spacer blocks, and two 1.5-m-long steel reinforcing rods that were 1.5 cm in diameter. Each steel rod was inserted through the spacer blocks and driven into the substrate at a slight downstream angle to increase stability. After the rods and spacers were in place, the half-log was added on top of the blocks with the flat side down. The remaining 30 cm of steel rod was then bent 90° to hold the structure in place, leaving a 15-cm gap beneath the log. Land-use and habitat mapping Prior to the addition of half-logs, sampling took place in June 2003 to provide a preliminary baseline description of each site. Detailed habitat maps were constructed for each site, which included information on channel morphology, current velocity (m/s), depth (cm), and substrate type based on Meador et al. (1993), and existing habitat-cover features located within each reach that would provide a stable site for macroinvertebrate colonization. In-stream cover was defined as any structure that redirected the current and/or shaded the substrate (Dufour, 1989), and included riffle, pool,

123

boulder, overhanging bank, aquatic vegetation, and LWD complexes (measured to the nearest m2 and computed as a percentage of total site surface area). Riparian canopy coverage also was measured using a convex spherical-crown densiometer in order to provide an estimate of canopy coverage at each site. Watersheds were delineated using Arc View 3.2 (Environmental Systems Research Institute, Redlands, California) to determine the amount of each land-use cover present (i.e., agriculture, forest, and fallow field) and the amount of forested area within a 30-m lateral buffer of the stream based on Frimpong et al. (2005). Land-use data for these analyses were derived from the National Agricultural Statistical Service (NASS) 2001 crop data and USGS—Land Use/Land Cover databases because they provided the most accurate representation of current land-use activities in the upper Wabash River basin. Information gathered from these analyses was used to explain trends in the colonization and use of half-logs by aquatic macroinvertebrates and changes in their community composition. Half-log sampling Aquatic macroinvertebrate populations were sampled once each month from a random 1/8th section of log (i.e., top, bottom, and sides; area = 0.25 m2) from July


through October 2003 and April through July 2004 (N = 864 samples) using a hard-bristle brush and a D-frame kick net. The hard-bristle brush was used to scrape and fan the accumulated biofilm in a downstream direction into the D-frame kick net (210-lm mesh). The removed biofilm was then preserved in a 10% formalin solution and returned to the laboratory where samples were sorted and macroinvertebrates were identified to family level according to McCafferty (1998) and Merritt & Cummins (1984). Samples and specimens were further categorized by measures of stream health (i.e., the abundance and richness of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa), functional feeding guilds (i.e., filterer-collector, gatherer-collector, predator, scraper, or shredder), and regional tolerance values according to the United States Environmental Protection Agency Rapid Bioassessment Protocols (Plafkin et al., 1989).

197

habitat variables. A fixed-effect ANOVA was used to compare functional guilds among streams where streams were treated as a fixed effect and sitespecific habitat variables were treated as covariates. To further explain these relationships, the relative abundance of each feeding and tolerance guild was regressed against the amount of riparian canopy coverage and the percentage of fine substrates. These models were developed to investigate trends in macroinvertebrate community composition along a gradient of human perturbation. All comparisons were made using SAS version 8.2 (SAS Institute, Cary, North Carolina). Proportion data were arcsine square root transformed prior to analyses to meet distributional assumptions. If a significant difference was detected at the a = 0.05 level for any comparison, a Tukey honestly significant difference (HSD) test was used to assess differences among means.

Data analysis Relative abundance, taxa richness, percentage of EPT taxa, and percentage of tolerant taxa (i.e., taxa with regional tolerance values greater than six) collected in each sample were documented following half-log additions to determine colonization rates and seasonal-use patterns. For these analyses, a mixed-effect analysis of variance (ANOVA) was used to compare community metrics with natural, in-stream, and riparian habitat variables over time. For each model, sampling month was treated as a fixed effect and stream as a random effect, while the amount of natural in-stream cover and riparian canopy coverage at each site were covariates. Further comparisons were made among riparian land-use scenarios (i.e., agriculture, forest, or fallow field) to determine where half-log structures were most effective in providing a stable site for colonization and use by aquatic macroinvertebrates. Halflog additions were pooled by land-use type and compared using the same response variables discussed previously. A fixed-effect ANOVA was used to compare mean differences in community characteristics using land-use type as a fixed effect, while the location of each half-log (i.e., site within the stream) was considered a blocking factor. Stream-level comparisons were made to describe the functional guild representation of macroinvertebrates on half-logs in each stream based on natural

Results Natural in-stream cover The amount and type of pre-existing habitat were variable by site, stream, and land-use type (Table 2). The average amount of cover found in these streams as a percentage of total stream area was 25.2% (range, 0.71– 43.8%). Aquatic vegetation (curly-leaf pondweed Potamogeton crispus) was the most dominant in-stream cover in two of the three agricultural streams (mean = 27.3%; range, 0–43.9%), but was found sparingly elsewhere. Forested sites had moderate percentages of pool habitat (mean = 10.1%), along with undercut banks (mean = 5.2%). However, riffle habitat was completely absent in two of the three forested streams. Natural in-stream cover at fallow field sites was the most heterogeneous, containing moderate amounts of pools (mean = 9.2%), riffles (mean = 5.8%), and undercut banks (mean = 4.8%). The percentage of fine substrates (i.e., particles \2 mm) were highest in agricultural sites (mean = 78.3%), followed by forest (mean = 44.0%) and fallow field (mean = 32.3%) streams. As expected, forested streams had the highest percentage of canopy coverage (mean = 78.3%) and agricultural sites had the lowest (mean = 8.4%). All streams, regardless of riparian land-use type, were dominated by sand substrates and run habitat, with very

123

198


Table 2 Summary of habitat variables used to quantify pre-existing natural habitat within each site as a percentage (%) of overall stream surface area Land-use type

Agriculture

Forested

Fallow field

Stream

Code

Habitat variables Large-woody debris

Boulder

Undercut bank

Riffle

Pool

Total cover

Grassy Fork Creek

GFC

0.43

0.00

0.28

0.00

0.00

0.00

0.71

Keans Bay Creek

KBC

0.00

38.20

0.14

4.25

0.00

0.00

42.59

Turkey Creek

TC

0.00

43.73

0.04

0.00

0.00

0.00

43.77

Burnett Creek

BC

1.43

0.00

0.09

3.06

0.00

10.40

14.98

Indian Creek

IC

2.64

0.00

0.91

4.05

0.00

17.66

25.26

Little Pine Creek Crooked Creek

LPC CC

1.23 1.43

2.28 0.00

0.45 0.20

8.33 6.14

18.98 0.00

2.21 6.52

33.48 14.29

Kickapoo Creek

KPC

0.20

0.00

0.28

7.00

9.14

21.18

37.80

Moots Creek

MC

0.79

1.26

2.60

1.11

8.12

0.00

13.88

little naturally occurring large-woody debris or hard substrates for macroinvertebrate colonization. Aquatic macroinvertebrate community composition A total of 20,730 macroinvertebrates were collected from July through October 2003 and April through July 2004, representing 55 families. Members of the family Chironomidae were the most represented taxa, comprising nearly 77% of all individuals collected. Seventeen families were considered rare collections (i.e., found at only one site and/or once during sampling), while an additional 10 families were collected less than five times. Aquatic macroinvertebrates that were primarily gatherer-collector feeders were the most dominant feeding guild present, accounting for greater than 86% of all taxa. Chironomids were classified as gatherer-collectors for these analyses. The remaining four guilds (i.e., filterer-collector, predator, scraper, and shredder) each contributed less than 5% of the total abundance, with predators being the least abundant guild (0.005%). A wide range of tolerance values also were represented in the collection, with the majority of taxa tolerant of pollution and environmental degradation (mean = 7.3; based on a scale of 0–10, 10 being the most pollution-tolerant). Half-log colonization A large-scale flood occurred 1 week after half-log installation and caused most macroinvertebrates to be

123

Aquatic vegetation

scoured from study reaches. Following the flooding event, half-logs were colonized and showed significant increases in macroinvertebrate relative abundance (F = 3.52, P \ 0.0001, Fig. 3) and taxa richness (F = 5.14, P \ 0.0001, Fig. 4) over time (Table 3). After the flood event, relative abundances of macroinvertebrates found on half-logs increased until September 2003 (mean = 21.4 taxa/0.25 m2) before decreasing when water temperatures cooled in October (Fig. 3). Relative abundances increased during spring and peaked in May 2004 (mean = 65.7 taxa/0.25 m2) before another large flood event occurred in early June. The high flow and periods of high emergence resulted in reduced population numbers. Average taxa richness across sites followed a similar pattern, peaking during September 2003 (mean = 3.4) before decreasing during the cooler temperatures of October and April 2004 (Fig. 4). Richness numbers appeared to plateau at *3 families following the second flooding event in 2004 (mean = 3.3, Fig. 4). The proportion of taxa intolerant towards pollution (i.e., EPT taxa) varied significantly by month, stream, and canopy coverage (F [ 9.57, P \ 0.0001, Fig. 5), as did the percentage of tolerant taxa (F [ 7.22, P \ 0.01, Fig. 6, Table 3). In August, the percentage of EPT taxa decreased slightly before increasing to its peak at the end of October 2003 (mean = 24.1%). The percentage of EPT taxa was at its lowest (mean = 3.9%) during April 2004, and increased every month thereafter until July 2004 (Fig. 6). The percentage of tolerant taxa was much less variable


200

GFC

KBC

TC

BC

IC

LPC

CC

KPC

MC

150 100

2

Relative abundance (taxa/0.25m )

Fig. 3 Relative abundance (taxa/0.25 m2) of macroinvertebrates colonizing half-logs by stream with standard errors for each month of sampling organized by land-use type (e.g., agriculture—top; forest—middle; fallow field—bottom; see Table 2 for code definitions)

199

50 0 200 150 100 50 0 200 150 100 50

M

4 Ju

l-0

4 ay

-0

03 p-

Ju

M

Se

l-0 Ju 4 l-0 3

4 ay

-0

03 pSe

Ju

l-0 Ju 4 l-0 3

4 M

ay

-0

03 pSe

Ju

l-0

3

0

Month

8 GFC

KBC

TC

BC

IC

LPC

CC

KPC

MC

6 4 2 0

Taxa Richness

Fig. 4 Taxa richness of macroinvertebrates colonizing half-logs by stream, with standard errors for each month of sampling organized by land-use type (e.g., agriculture—top; forest—middle; fallow field—bottom; see Table 2 for code definitions)

6 4 2 0 6 4 2

00 4 /2 07

00 4 /2 05

00 3 09 /2

07 004 /2 00 3

/2 07

00 4 05 /2

00 3 09 /2

07 /2 07 004 /2 00 3

4 05 /2 00

3 09 /2 00

07 /2 00

3

0

Month

over time, peaking in late summer (August 2003; mean = 81.8%) and early spring (April 2004; mean = 91.0%) when water temperatures were at their highest and lowest, respectively (Fig. 6).

Among-stream comparisons Among-stream comparisons based on predominant riparian land-use type yielded significant results for

123

200


Table 3 Results of the mixed-effect ANOVA for the colonization of half-logs over time, the fixed-effect ANOVA for among landuse type comparisons, and the mixed-effect ANOVA for within-stream comparisons including response variables, effects, and significant interactions (NS = not significant at the a = 0.05 level) Response

Model

Month

Stream

Cover Canopy

Interactions

Relative abundance \0.0001 \0.0001 \0.0001 NS

NS

Cover * month * stream; cover * stream; month * stream

Richness

\0.0001 \0.0001 \0.0001 NS

NS

Cover * month * stream; cover * stream; month * stream

EPT taxa

\0.0001 \0.0001 \0.0001 NS

\0.0001 Cover * month; cover * stream; month * stream

Tolerant taxa

\0.0001 \0.0001 \0.0001 NS

\0.0001 Canopy * stream; cover * month * stream; cover * stream; month * stream

Model

Land-use

Location

Relative abundance

0.0283

\0.0001

NS

Richness

\0.0001

\0.0001

NS

EPT taxa

0.0353

0.0259

NS

Tolerant taxa

NS

0.0242

NS

Interactions

Model

Stream

Cover

Canopy

Interactions

EPT taxa

\0.0001

\0.0001

NS

0.0196

Cover * stream

Tolerant taxa

\0.0001

\0.0001

NS

0.0009

Cover * stream

0.0001

0.0003

NS

0.0336

Canopy * stream

Filterer-collector taxa

\0.0001

\0.0001

NS

NS

Canopy * stream

Predator taxa Scraper taxa

\0.0001 \0.0001

\0.0001 \0.0001

NS NS

NS 0.001

Canopy * stream

Shredder taxa

\0.0001

\0.0001

NS

NS

Fig. 5 Percentage of EPT taxa colonizing half-logs by stream, with standard errors for each month of sampling organized by land-use type (e.g., agriculture—top; forest—middle; fallow field—bottom; see Table 2 for code definitions)

GFC

KBC

TC

BC

IC

LPC

CC

KPC

MC

60 40 20 0

Percent EPT taxa

Gatherer-collector taxa

60 40 20 0 60 40 20

Month

123

04 /2 0 07

04 /2 0 05

03 /2 0 09

/2 07 004 /2 00 3

07

04 /2 0 05

/2 00 3 09

4

/2 07 004 /2 00 3

07

05

/2

00

03 /2 0 09

07

/2 0

03

0

Hydrobiologia (2008) 605:193–207 100 80 60 40 20

Percent tolerant taxa

Fig. 6 Percentage of tolerant taxa colonizing half-logs by stream, with standard errors for each month of sampling organized by land-use type (e.g., agriculture—top; forest—middle; fallow field—bottom; see Table 2 for code definitions)

201

GFC

KBC

TC

BC

IC

LPC

CC

KPC

MC

0 80 60 40 20 0 80 60 40 20

4 /2

00

4 07

05

/2

00

3 00 /2 09

4

/2 0 07 04 /2 00 3

07

05

/2

00

3 00 /2 09

4

/2 0 07 04 /2 00 3

07

05

/2

00

3 00 /2 09

07

/2

00

3

0

Month

relative abundance (F = 1.52, P = 0.03) and taxa richness (F = 2.25, P \ 0.0001). Both response variables also showed significant land-use effects (P \ 0.0001), but location (i.e., site within the stream) was not a significant factor (P [ 0.37, Table 3). Forest streams had significantly lower relative abundances of aquatic macroinvertebrates colonizing half-logs (mean = 14.9 taxa/0.25 m2) than fallow field (mean = 29.5 taxa/0.25 m2) and agricultural (mean = 33.1 taxa/0.25 m2) streams (Fig. 3). Similar results were found for taxa richness by riparian landuse type. Forest stream taxa richness was significantly lower (mean = 2.2, P \ 0.05) than fallow field (mean = 2.9) and agriculture (mean = 3.1; Fig. 4) streams. Functional guilds and tolerant taxa responded differently to riparian land use. The percentage of EPT taxa showed significant variation by land-use type (F = 3.67, P = 0.03), although there were no significant location effects (F = 1.18, P = 0.30) or interactions (Table 3). The percentage of EPT taxa was highest in forest streams (mean = 23.0%), followed by agriculture (mean = 16.3%) and fallow fields (mean = 9.4%, Fig. 5). The percentage of tolerant taxa did not vary significantly among landuse types (F = 1.35, P = 0.09, Fig. 6).

Community metric comparisons The percentage of EPT taxa and tolerant taxa showed significant variation by stream (F [ 10.93, P \ 0.0001) and as a covariate of canopy coverage (F [ 5.47, P \ 0.02, Table 3). The percentage of EPT taxa was significantly related to the percentage of canopy coverage at each stream (r2 = 0.52, P = 0.03), but not to the percentage of fine sediments (r2 = 0.04, P = 0.60, Fig. 7). The relative abundance of tolerant taxa (regional tolerance value greater than 6) tended to decrease with increasing canopy coverage and fine substrates; however, only the fine substrate relationship was significant (r2 = 0.165, P \ 0.0001, Fig. 7). Individuals representing the gatherer-collector functional feeding guild varied significantly by stream (F = 3.66, P \ 0.001) and riparian canopy coverage (F = 4.53, P = 0.03, Table 3). Filterercollector individuals exhibited the same effects with regard to stream effects (F = 10.96, P \ 0.0001) as gatherer-collectors. The relative abundance of gatherer-collectors tended to decrease with increasing fine substrates (r2 = 0.27; P = 0.15; Fig. 7). The percentage of filterer-collector taxa was not significantly related to increasing canopy coverage and fine

123

202 50

50

y = 0.0816x + 12.0260 2 r = 0.0415 p = 0.5991

y = 0.2549x + 0.2513 2 r = 0.5240 p = 0.0275

40

EPT

Fig. 7 Percentage of EPT, tolerant, and gatherercollector taxa, as a function of canopy coverage (left column) and fine substrates (right column), with standard errors, lines of best fit, and equations


30

40 30

20

20

10

10

Tolerant

0

0

90

90

80

80

70

70

y = -0.1669x + 86.5220 2 r = 0.3748 p = 0.0797

60 50

90

60 50

y = -0.0278x + 86.4190 2 r = 0.0445 p = 0.5860

95

Gatherer-collector

y = -0.1260x + 82.5550 2 r = 0.1650 p < 0.0001 y = -0.0782x + 88.7060 2 r = 0.2716 p = 0.1502

90

85

85

80

80

75

75

70 0

20

40

60

80

Canopy coverage

substrates (F = 0.01, P = 0.96 and F = 3.28, P = 0.11, respectively; Fig. 8). Predaceous feeders were rare (\5%) in most collections, but demonstrated significant variation by stream (F = 13.67, P \ 0.0001, Table 3). There was a strong, negative relationship between the percentage of predator taxa and the amount of canopy coverage (F = 5.36, P = 0.05, Fig. 8). The relative abundance of predator taxa also increased with the percentage of fine substrates in streams (F = 2.07, P = 0.19; Fig. 8). Scraper feeders also showed significant stream effects (F = 27.26, P \ 0.0001, Table 3). The percentage of scraper taxa did not vary significantly with increasing canopy coverage or the percentage of fine substrates (Fig. 8). Shredder taxa showed significant stream effects (F = 9.87, P \ 0.0001, Table 3). The relative abundance of shredder taxa decreased significantly with increasing canopy coverage (F = 4.94, P = 0.02, Fig. 8). In contrast, shredder numbers increased with increasing fine sediments (F = 3.46, P = 0.11, Fig. 8).

123

95

0

20

40

60

80

70 100

Fine substrate

Discussion Half-log structures placed into tributaries of the upper Wabash River basin were colonized by aquatic macroinvertebrates that differed by functional guild and pollution tolerance. Hax & Golladay (1993) found that LWD in streams acts as a site for biofilm growth, which provides food and habitat for macroinvertebrates. This species–habitat interaction is often accompanied by changes in macroinvertebrate community composition and functional guilds (Johnson et al., 2003). Large-woody debris additions have been associated with increased abundance (Drury & Kelso, 2000), density (Angermeier & Karr, 1984), taxa richness (Johnson & Kennedy, 2003; Johnson et al., 2003), and diversity (Drury & Kelso, 2000; Johnson et al., 2003) of aquatic macroinvertebrates. By adding half-logs into the stream channel, habitat heterogeneity and complexity was increased in our study sites, which can have positive effects on survival, reproduction, and production of aquatic


20

20 y = 0.0022x + 5.9886 r2 = 0.0003 p = 0.9641

15

Filterer-collector

Fig. 8 Percentage of filterer-collector, predator, scraper, and shredder taxa as a function of canopy coverage (left column) and fine substrates (right column), with standard errors, lines of best fit, and equations

203

10

5

5

0

0 y = -0.0573x + 6.1735 r2 = 0.4335 p = 0.0538

10

Predator

15

10

12

8

12

y = 0.0472x + 0.1485 r2 = 0.2279 p = 0.1938

10 8

6

6

4

4

2

2

0

0 y = 0.1746x – 0.1940 r2 = 0.4138 p = 0.0616

30

Scraper

y = 0.0793x + 2.0384 r2 = 0.3192 p = 0.1130

y = 0.0610x + 7.6102 r2 = 0.0390 p = 0.6106

30

20

20

10

10

0

0

Shredder

y = 0.0128x – 0.0054 r2 = 0.3308 p = 0.1052

y = -0.0147x + 1.5758 r2 = 0.5698 p = 0.0187

3

3

2

2

1

1

0 0

20

40

60

80

Canopy coverage

macroinvertebrates (Braccia & Batzer, 2001; Benke & Wallace, 2003). Colonization rates of introduced substrates by aquatic macroinvertebrates are determined by several factors, including time and distance from previous disturbances (Anderson, 1992; Beisel et al., 2000), substrate stability (Hax & Golladay, 1998), adjacent habitat heterogeneity (Beisel et al., 2000), current velocity (Hax & Golladay, 1993; Drury & Kelso, 2000; Johnson & Kennedy, 2003), available food sources (Drury & Kelso, 2000; Mathooko & Otieno, 2002), season (Shaw & Minshall, 1980), and substrate composition (Wohl & Carline, 1996). In our

0

20

40

60

80

0 100

Fine substrate

study, aquatic macroinvertebrates were found on each half-log during the first sampling period, approximately 2 weeks after the large-scale flood. Mathooko & Otieno (2002) found that LWD added to the stream channel was colonized by invertebrates immediately despite not having a fully developed layer of biofilm. The authors hypothesized that macroinvertebrates were attracted to the new substrates because naturally occurring LWD is extremely rare at their study site. Hax & Golladay (1993) also found that the stability and greater potential for surface complexity of wood increased its suitability as habitat over natural, unstable habitats, such as sand or silt. Half-logs in

123

204

our streams were the most stable substrate available for colonization during the time immediately following the first flood event, which explains their early colonization in tributaries of the upper Wabash River where natural LWD was nearly absent. Seasonal changes in macroinvertebrate populations can develop due to thermal regime, current velocity, energy inputs, and life-history patterns (Shaw & Minshall, 1980; Delong & Brusven, 1998; Armitage et al., 2001). In their study of the River Frome, England, Armitage et al. (2001) reported the highest abundances of aquatic macroinvertebrates in late spring and the greatest taxa richness in late summer. Taxa richness in our streams was consistently low during all sampling months despite variable temperatures, water levels, current velocities, and land-use type. The low taxa richness and high percentages of tolerant taxa observed in this study may be the result of high proportions of homogenous habitat, which promotes dominance by only a few tolerant taxa (Lenat & Crawford, 1994; Beisel et al., 2000). This is especially true in tributaries of the upper Wabash River where increased sediment loads and embeddedness have decreased the amount of available gravel and cobble substrates. With increasing fine substrate, the relative abundance of filterer-collector, predator, scraper, and shredder taxa increased, which suggests that hard and stable substrates, such as half-logs, are increasingly important for these functional groups as sediment loads increase. The percentage of gatherercollector taxa, however, decreased with increasing fine sediment loads. Berkman et al. (1986) found that filterer-collector taxa become detached from hard substrates with increasing sedimentation, while gatherer-collectors can benefit from increased sedimentation because of their burrowing habits. The increase in periphyton and other prey items associated with the accumulated biofilm located on half-logs best explains increases in predator and scraper taxa (Delong & Brusven, 1998; Benke & Wallace, 2003). In addition to stream shading, stabilizing banks, and providing energy inputs, riparian vegetation can play a role in developing taxonomic and functional guild representation (Anderson, 1992; Delong & Brusven, 1998; Armitage et al., 2001). The percentage of EPT taxa increased with increasing canopy

123


cover. Several studies have reported both an increase in abundance and richness of EPT taxa with increasing forested riparian area because of increased habitat heterogeneity, stable substrates for colonization, and inputs of particulate organic matter (Lenat & Crawford, 1994; Genito et al., 2002; Rinella & Feminella, 2005). Further, Collier (1995) reported that riparian vegetation may increase aquatic invertebrate biodiversity, especially Ephemeroptera and Trichoptera spp., by decreasing stream temperatures and light penetration. Conversely, the percentage of shredder taxa in our streams decreased significantly with increasing canopy cover, which is likely due to a decreased dependence on introduced substrates in areas where natural substrates are considered to be of higher quality. In agricultural systems dominated by fine materials (i.e., sand, silt, and clay) and where a lack of existing quality habitat such as large-woody debris is a limiting factor, aquatic macroinvertebrates respond favorably to half-log additions. Agricultural streams had significantly higher relative abundance and taxa richness than fallow field and forested sites. These differences could be attributed to higher periphyton production on half-logs and more degraded natural habitat quality in agricultural streams making the half-logs patches of high-quality substrates in an otherwise degraded habitat. This could potentially attract greater numbers and diversity of macroinvertebrates to half-logs in agricultural streams than in streams with better natural habitat quality. Others have shown that increased light penetration and water temperatures associated with the absence of canopy cover can cause increased periphyton production and subsequent increases in aquatic macroinvertebrate abundance (Carlson et al., 1990). Forest sites had significantly lower taxa richness and relative abundances of macroinvertebrates collected from half-log structures. This is probably due to the high degree of habitat heterogeneity and quality already existing in these sites. Although riffle habitat was not found to be prevalent in the forested sites we sampled, there were patches of suitable riffle habitat located adjacent to sampling locations. Average taxa richness was lower in forest sites, but the difference between land-use types was less than one family. Similarly, Carlson et al. (1990) found increased numbers of macroinvertebrates in logged streams versus unlogged sites in Oregon streams, but


could not detect differences in taxa richness or diversity between treatments. While relative abundance was lower in forested streams than in other streams in this study, the percentage of EPT taxa was significantly higher. This probably reflects the higher habitat quality in forest streams than in agricultural or fallow field streams. There was no difference among land-use types in the percentage of pollution-tolerant taxa occupying half-logs. Decreased habitat heterogeneity can lead to an increased abundance of highly adaptive taxa which out-compete more sensitive individuals and dominate community composition (Delong & Brusven, 1998; Beisel et al., 2000). Haggerty et al. (2004) found that collector-feeding chironomids dominated samples in recently logged Washington streams. Other studies have reported similar trends with regard to this family and their ubiquitous manner and dominance in community composition (Delong & Brusven, 1998; Rinella & Feminella, 2005). Delong & Brusven (1998) decided to exclude members of the family Chironomidae from their analyses because they were unable to break them down further taxonomically. We chose to include this family because very few genera were represented, and failing to do so could have lead to spurious conclusions about functional guild representation and influence in half-log colonization dynamics. Functional guild response to half-log additions was variable by stream, natural habitat, and canopy coverage. Shaw & Minshall (1980) reported that the colonization rates of introduced substrates are often species specific and that seasonal differences may occur. Further, McKie & Cranston (2001) found that both macroinvertebrate taxa and guild colonization of introduced LWD varied by wood type and riparian vegetation. All half-logs in this study were constructed using the same type of wood from the same stand of trees. The riparian areas of these study streams did not contain red pine, so this type of wood may be considered foreign to macroinvertebrates in these systems. This may be a possible explanation of the poor relationships observed between functional guilds and habitat variables during the first 2 years of the study. Future studies should investigate colonization rates, community composition, and assemblage structure of different species of LWD used in manufacture of half-logs.

205

Additionally, the red pine logs used in this study were still green at the time of installation and showed little signs of decay after being submerged for 2 years. The most noticeable signs of wear were caused by pieces of bark being sloughed off during the sampling process. The softening and natural breakdown of wood caused by decay can increase LWD habitat suitability for macroinvertebrates by increasing microhabitat heterogeneity and surface area available for colonization (Hax & Golladay, 1993; Drury & Kelso, 2000; Braccia & Batzer, 2001; Mathooko & Otieno, 2002). Changes in community composition and functional guild response may take place over an extended period of time. Because of this, a long-term study examining the changes in macroinvertebrate composition associated with decaying LWD would greatly enhance the current literature on the subject. Our results suggest that half-log structures were readily colonized by aquatic macroinvertebrates, and that community metrics and functional feeding guilds among invertebrates on half-logs differed across land-use types. In most cases, the extent of colonization and use of half-logs was dependent upon the pre-existing in-stream habitat quality and the predominant land-use type. Agricultural stream macroinvertebrate communities in particular responded well to half-log additions because the half-logs increased habitat complexity and stability. High abundances and low taxa richness at most sites were the result of highly adaptive individuals associated with overall degraded conditions in these streams. This study has demonstrated that half-logs used for fish habitat improvement are rapidly colonized by macroinvertebrates, potentially providing ‘‘hot spots’’ of fish food organisms, and that invertebrate communities on half-logs can be used as bioindicators to differentiate among streams of varying riparian land use. Acknowledgments We would like to thank T. Bacula, A. Mooradian, D. Rajchel, S. Reed, and C. White for their laboratory assistance, as well as E. Frimpong for his assistance with spatial data analyses. Constructive comments on earlier drafts of this manuscript by D. Kreutzweiser, G. Parker, T. Simon, and A. Steinman improved this manuscript. Funding for this project was provided for by Purdue University Department of Forestry and Natural Resources. This research was approved for publication as manuscript 18099 by the Purdue University Agricultural Research Programs.

123

206

References Anderson, N. H., 1992. Influence of disturbance on insect communities in Pacific Northwest streams. Hydrobiologia 248: 79–92. Anderson, N. H., J. R. Sedell, L. M. Roberts & F. J. Triska, 1978. The role of aquatic invertebrates in processing of wood debris in coniferous forest streams. The American Midland Naturalist 100: 64–82. Angermeier, P. L. & J. R. Karr, 1984. Relationships between woody debris and fish habitat in a small warmwater stream. Transactions of the American Fisheries Society 113: 716–726. Armitage, P. D., K. Lattmann, N. Kneebone & I. Harris, 2001. Bank profile and structure as determinants of macroinvertebrate assemblages – seasonal changes and management. Regulated Rivers: Research & Management 17: 543–556. Beisel, J. N., P. Usseglio-Polatera & J. C. Moreteau, 2000. The spatial heterogeneity of a river bottom: A key factor determining macroinvertebrate communities. Hydrobiologia 442/423: 163–171. Benke, A. C. & J. B. Wallace, 2003. Influence of wood on invertebrate communities in streams and rivers. In Gregory, S. V., K. L. Boyer & A. M. Gurnell (eds), The Ecology and Management of Wood in World Rivers. American Fisheries Society, Symposium 37, Bethesda, Maryland, 149–177. Berkman, H. E., C. F. Rabeni & T. P. Boyle, 1986. Biomonitors of stream quality in agricultural areas: Fish versus invertebrates. Environmental Management 10: 413–419. Bilby, R. E. & J. W. Ward, 1989. Changes in characteristics and function of woody debris with increasing size of streams in western Washington. Transactions of the American Fisheries Society 118: 368–378. Braccia, A. & D. P. Batzer, 2001. Invertebrates associated with woody debris in a southeastern US forested floodplain wetland. Wetlands 21: 18–31. Burgess, S. A., 1980. Effects of stream habitat improvement on invertebrates, trout populations, and mink activity. Journal of Wildlife Management 44: 871–880. Carlson, J. Y., C. W. Andrus & H. A. Froehlich, 1990. Woody debris, channel features, and macroinvertebrates of streams with logged and undisturbed riparian timber in northeastern Oregon, U.S.A Canadian Journal of Aquatic Sciences 47: 1103–1111. Collier, K. J. 1995. Environmental factors affecting the taxonomic composition of aquatic macroinvertebrate communities in lowland waterways of Northland, New Zealand. New Zealand Journal of Marine and Freshwater Research 29: 453–465. Delong, M. D. & M. A. Brusven, 1998. Macroinvertebrate community structure along the longitudinal gradient of an agriculturally impacted stream. Environmental Management 22: 445–457. Drury, D. M. & W. E. Kelso, 2000. Invertebrate colonization of woody debris in coastal plain streams. Hydrobiologia 434: 63–72. Dufour, J. A., 1989. Evaluation of half-logs as habitat improvement structures for smallmouth bass Micropterus

123

Hydrobiologia (2008) 605:193–207 dolomieui and rock bass Ambloplites rupestris. M.S. Thesis, Michigan State University, East Lansing. Frimpong, E. A., T. M. Sutton, K. J. Lim, P. J. Hrodey, B. Engel, T. P. Simon, J. G. Lee & D. C. Le Master, 2005. Determination of optimal riparian forest buffer dimensions for stream biota landscape association models using multimetric and multivariate response. Canadian Journal of Fisheries and Aquatic Sciences 62: 1–6. Genito, D., W. J. Gburek & A. N. Sharpley, 2002. Response of stream macroinvertebrates to agricultural land cover in a small watershed. Journal of Freshwater Ecology 17: 109–119. Haggerty, S. M., D. P. Batzer & C. R. Jackson, 2004. Macroinvertebrate response to logging in coastal headwater streams of Washington, U.S.A. Canadian Journal of Fisheries and Aquatic Sciences 61: 529–537. Hax, C. L. & S. W. Golladay, 1993. Macroinvertebrate colonization and biofilm development on leaves and wood in a boreal river. Freshwater Biology 29: 79–87. Hax, C. L. & S. W. Golladay, 1998. Flow disturbance of macroinvertebrates inhabiting sediments and woody debris in a prairie stream. American Midland Naturalist 139: 210–223. Hunt, R. L., 1982. An evaluation of half-logs to improve brown trout habitat in Emmons Creek. Wisconsin Department of Natural Resources, Madison, Wisconsin. Report Number 116. Johnson, L. B., D. H. Breneman & C. Richards, 2003. Macroinvertebrate community structure and function associated with large wood in low gradient streams. River Research and Applications 19: 199–218. Johnson, Z. B. & J. H. Kennedy, 2003. Macroinvertebrate assemblages of submerged woody debris in the Elm Fork of the Trinity River, Texas. Journal of Freshwater Ecology 18: 187–197. Lenat, D. R. & J. K. Crawford, 1994. Effects of land use on water quality and aquatic biota of three North Carolina streams. Hydrobiologia 294: 185–199. Mathooko, J. M., & C. O. Otieno, 2002. Does surface textural complexity of woody debris in lotic ecosystems influence their colonization by aquatic invertebrates? Hydrobiologia 489: 11–20. McCafferty, W. P., 1998. Aquatic entomology the fishermen’s and ecologists’ illustrated guide to insects and their relatives. Jones and Bartlett Publishers, Sudbury, Massachusetts. McKie, B. & P. S. Cranston, 2001, Colonisation of experimentally immersed wood in south eastern Australia: Responses of feeding groups to changes in riparian vegetation. Hydrobiologia 452: 1–14. Meador, M. R., C. R. Hupp, T. F. Cuffney & M. E. Gurtz, 1993. Methods for characterizing stream habitat as part of the National Water-Quality Assessment program. U.S. Geological Survey, Raleigh, North Carolonia. Open-File Report 93-408. Merritt, R. W. & K. W. Cummins (eds), 1984. An Introduction to the Aquatic Insects of North America, 2nd edn. Kendall/Hunt Publishers, Dubuque, Iowa. Montgomery, D. R., J. M. Buffington, R. D. Smith, K. M. Schmidt & G. Pess, 1995. Pool spacing in forest channels. Water Resources Research 31: 1097–1105.

Hydrobiologia (2008) 605:193–207 Plafkin, J. L., M. T. Barbour, K. D. Porter, S. K. Gross & R. M. Hughes, 1989. Rapid bioassessment protocols for use in streams and rivers: Benthic macroinvertebrates and fish. EPA 444/4-89-001. U.S. Environmental Protection Agency, Cincinnati, Ohio. Rinella, D. J. & J. W. Feminella, 2005. Comparison of benthic macroinvertebrates colonizing sand, wood, and artificial substrates in a low-gradient stream. Journal of Freshwater Ecology 20: 209–218. Shaw, D. W. & G. W. Minshall, 1980. Colonization of an introduced substrate by stream macroinvertebrates. Oikos 34: 259–271. Shields, F. D., Jr., S. S. Knight & C. M. Cooper, 1995. Use of the index of biotic integrity to assess physical habitat

207 degradation in warmwater streams. Hydrobiologia 312: 191–208. Talmage, P. J., J. A. Perry & R. M. Goldstein, 2002. Relation of instream habitat and physical conditions to fish communities of agricultural streams in the northern Midwest. North American Journal of Fisheries Management 22: 825–833. Wallace, J. B. & J. R. Webster, 1996. The role of macroinvertebrates in stream ecosystem function. Annual Review of Entomology 41: 115–139. Wohl, N. E. & R. F. Carline, 1996. Relations among riparian grazing, sediment loads, macroinvertebrates, and fishes in three central Pennsylvania streams. Canadian Journal of Fisheries and Aquatic Sciences 53: 260–266.

123