Effects of substrate on the benthic macroinvertebrate community: An ...

2 downloads 0 Views 540KB Size Report
Sep 21, 2014 - affect the macroinvertebrate community (O'Connor, 1991;. Mathooko and ..... using the Shannon's index (H0) for the latter. For richness and.
Ecological Engineering 73 (2014) 109–114

Contents lists available at ScienceDirect

Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng

Short communication

Effects of substrate on the benthic macroinvertebrate community: An experimental approach Nneka D. Molokwu a, * , Pedro G. Vaz b , Therin Bradshaw a , Abigail Blake a , Catherine Henessey a , Eric Merten a a

Department of Biology, Wartburg College, Waverly, IA 50677, United States CEABN – Centre of Applied Ecology “Prof. Baeta Neves”/InBIO – Research Network in Biodiversity and Evolutionary Biology, Institute of Agronomy, University of Lisbon, Tapada da Ajuda, Lisbon 1349-017, Portugal b

A R T I C L E I N F O

A B S T R A C T

Article history: Received 16 January 2014 Received in revised form 23 July 2014 Accepted 1 September 2014 Available online 21 September 2014

Wood and concrete are used in restoration projects in streams and rivers worldwide. Although the goal of such projects is often related to geomorphology or fish habitat, there may also be differences between wood and concrete materials in regards to colonization by macroinvertebrates. Similarly, installed structures with smooth surface textures may host different macroinvertebrate communities than those with complex surfaces (e.g., pitted or grooved). In the current study, a multiple-factor experimental setting was used to test the effect of wood and concrete and of their surface complexity in structuring stream macroinvertebrate assemblages. Forty uniform-sized substrates were placed in the Cedar River in northeast Iowa, USA and macroinvertebrate colonization was examined after one and two months. Using distance-based redundancy analysis, it was determined that (1) after one month community differences were only related to underlying streambed composition, (2) after two months differences were only related to smooth versus complex surfaces, and (3) at neither time did communities differ between wood and concrete. These results highlight the importance of colonization time in studies of introduced substrates; within the first month communities may have been related to local streambed inhabitants crawling onto the substrates, by the second month structural differences supported different communities on smooth versus complex surfaces, and over longer time periods it remains possible that communities would have responded to more subtle differences between wood and concrete. We suggest that restorationists should consider macroinvertebrates when installing structures in aquatic environments, and either use structures with both smooth and complex areas to promote different assemblages or conduct studies like this one to determine preferences for taxa of concern. ã 2014 Elsevier B.V. All rights reserved.

Keywords: Macroinvertebrate Colonization Restoration Substrate Aquatic ecosystems

1. Introduction Wood and concrete are used in restoration projects in streams and rivers worldwide. Although both materials can provide substrates for macroinvertebrates to colonise (Way et al., 1995; Tullos et al., 2006; Jahnig and Lorenz, 2008; Vaz et al., 2014), the question remains whether substrate material (concrete versus wood) or surface texture (smooth versus complex) is more important. This issue is particularly relevant because both wood and concrete can be manipulated or selected based on their texture or overall surface complexity. To address questions about

* Corresponding author. Tel.: +1 3195968426. E-mail addresses: [email protected] (N.D. Molokwu), [email protected] (P.G. Vaz), [email protected] (E. Merten). http://dx.doi.org/10.1016/j.ecoleng.2014.09.025 0925-8574/ ã 2014 Elsevier B.V. All rights reserved.

functional value of different substrate materials and textures, experimental substrates can be placed to examine colonisation preferences of benthic macroinvertebrates. In these studies, experimental substrates usually differ in the material (Magoulick, 1998) or the surface complexity (O’Connor, 1991; Mathooko and Otieno, 2002; Boyero, 2003), while other factors (e.g., size, area) can be controlled. Besides having the benefit of standardization, experimental substrates also have the advantage of being colonised by stream macroinvertebrates immediately after submergence (Boyero, 2003). Thus, some authors simply establish an arbitrary period of colonisation, typically 1 month, and document how the assembly is structured after that time period (Nilsen and Larimore, 1973; Lyon et al., 2009; Vaz et al., 2014). However, other studies indicate that colonisation time itself can affect the macroinvertebrate community (O’Connor, 1991; Mathooko and Otieno, 2002; Boyero, 2003).

110

N.D. Molokwu et al. / Ecological Engineering 73 (2014) 109–114

Although studies quantifying the effect of concrete or wood substrates on colonisation are relatively rare, existing studies with other materials allow some generalizations to be made. The substrate material can be important because some macroinvertebrates feed on the substrate itself (e.g., leaves, wood), use it opportunistically for physical support (e.g., refuge or perching habitat), or feed on deposited sediments and biofilms coating the surface (O’Connor, 1991). For example, several taxa ingest wood fragments (Spänhoff et al., 2000) and a few can digest the wood itself (Monk, 1976), whereas neither is expectable for concrete. Although some macroinvertebrates burrow into softer areas of wood, colonisation of wood and particularly concrete is primarily a surface phenomenon (Mathooko and Otieno, 2002) and therefore one may expect surface complexity to be a determinant factor in structuring macroinvertebrate assemblages on both materials. Indeed, the importance of surface complexity in altering macroinvertebrate assemblage composition is recognized across the literature. For example, O’Connor (1991) documented a significant macroinvertebrate–wood complexity relationship assessing different levels and types of structural complexity. Schmude et al.

(1998) also found more macroinvertebrates on substrates with physical complexity. Clifford et al. (1992) stated that this preference is because rough surfaces provide more secure attachment sites for macroinvertebrates to help them avoid getting swept away by current. On the other hand, surface complexity may also mediate differences in food resources for stream macroinvertebrates because, for example, rough surfaces may be colonised more quickly by algae—a major food source for macroinvertebrates—as compared to smooth surfaces (Clifford et al., 1992). Over time, macroinvertebrates can feed on the biofilms that coat the submerged substrate, providing organic layers of fungi, bacteria, algae, extracellular polysaccharides, and trapped seston (Golladay and Sinsabaugh, 1991; Couch and Meyer, 1992). In short, colonisation by stream macroinvertebrates could potentially be affected by food and substrate affinities which vary over time. In the current study, we used a multiple-factor experimental setting to test the effect of wood and concrete and of their surface complexity in structuring stream macroinvertebrate assemblages. Our research aimed to answer the following questions:

Table 1 Mean (1 SE) frequency of macroinvertebrate per substrate unit after one or two months of colonization in Cedar River. Frequencies are reported by complexity (complex, smooth) and substrate material (wood, concrete). Taxa

One month colonisation Complex

Chironomidae Total Corydalidae Total Heptageniidae Total Hydropsychidae Total Perlodidae Total Planareans Total Simuliidae Total Coenagrionidae Total Corixidae Total Hirudea Total Nematomorpha Total Tabanidae Total Hespherophylax Total Hydracarina Total Ephydridae Total Colicidae Total Ordobrevia Total Taeniopterygidae Total Ephemeroptera Total Elmidae Total Bivalvia Total Oligochaeta Total

Total Smooth

Complex

Wood

Concrete

Wood

Concrete

62.0  12.4

46.6  6.0 55.0  7.4 0.2  0.2 0.2  0.1 1.2  0.6 0.8  0.3 15.2  2.1 16.2  2.4 4.8  2.0 5.1  1.3 5.4  4.1 4.1  2.1 20.0  7.7 16.9  4.0 0.0 0.1  0.1 0.0 0.2  0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

25.3  10.7

41.6  9.3 34.3  7.2 0.0 0.0 0.4  0.2 0.2  0.1 15.4  5.1 10.7  3.5 2.6  1.7 4.2  1.4 2.0  1.8 1.2  1.0 14.4  4.9 19.9  4.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.2  0.2 0.5  0.3 17.0  4.2 5.3  1.8 3.0  2.0 14.3  4.1 0.2  0.2 0.3  0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.0 0.0 4.8  3.1 6.3  2.1 0.3  0.3 26.8  6.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Two months colonisation

Total Smooth

Wood

Concrete

Wood

Concrete

45.7  5.6

159.8  25.9

83.0  12.4

0.1  0.1

0.0

0.6  0.2

1.2  0.4

13.7  2.1

29.8  5.8

4.7  0.9

0.8  0.8

2.8  1.2

2.0  2.0

18.3  2.8

18.4  3.6

0.1  0.1

0.0

0.1  0.1

0.0

0.0

0.8  0.4

0.0

1.8  1.4

0.0

0.0

0.0

0.0

0.0

0.2  0.2

0.0

0.0

0.0

0.0

0.0

0.0

0.0

1.0  0.4

0.0

0.2  0.2

0.0

0.2  0.2

0.0

0.0

0.0

0.0

140.8  25.9 151.3  17.6 0.0 0.0 1.0  0.7 1.1  0.4 52.8  11.4 40.0  6.9 0.3  0.3 0.6  0.4 0.3  0.3 1.2  1.1 19.3  11.4 18.8  5.0 0.0 0.0 0.0 0.0 0.0 0.4  0.2 1.8  1.0 1.8  0.8 1.0  1.0 0.4  0.4 0.3  0.3 0.1  0.1 0.5  0.3 0.3  0.2 0.3  0.3 0.1  0.1 0.3  0.3 0.1  0.1 0.3  0.3 0.1  0.1 0.0 0.6  0.3 0.0 0.1  0.1 0.0 0.1  0.1 0.0 0.0 0.0 0.0

130.0  23.2 106.5  14.7 0.0 0.0 0.2  0.2 0.2  0.1 30.8  5.5 21.7  4.3 0.0 0.0 0.8  0.5 0.7  0.3 13.2  4.0 11.9  2.4 0.0 0.0 0.0 0.0 1.8  1.4 1.1  0.7 2.0  1.2 1.6  0.6 0.0 0.0 0.0 0.0 0.0 0.2  0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1  0.1 0.0 0.0 0.0 0.0 0.2  0.2 0.1  0.1 0.2  0.2 0.1  0.1

0.0 0.2  0.2 12.6  3.5 0.0 0.6  0.4 10.6  2.9 0.0 0.0 0.4  0.4 1.2  0.5 0.0 0.0 0.4  0.4 0.0 0.0 0.0 0.2  0.2 0.0 0.0 0.0 0.0

127.7  12.2 0.0 0.6  0.2 30.4  4.4 0.3  0.2 0.9  0.5 15.2  2.7 0.0 0.0 0.8  0.4 1.7  0.5 0.2  0.2 0.1  0.1 0.3  0.1 0.1  0.1 0.1  0.1 0.1  0.1 0.3  0.2 0.1  0.1 0.1  0.1 0.1  0.1 0.1  0.1

N.D. Molokwu et al. / Ecological Engineering 73 (2014) 109–114

(i) Does

substrate material (wood, concrete) or substrate complexity (smooth, complex) affect colonisation patterns of macroinvertebrates in the Cedar River? (ii) Is the effect of complexity comparable for wood and concrete? (iii) Does colonization time (one versus two months) affect the response to substrate material and complexity? We hypothesized that community composition would differ between materials and also between complexities, and that

111

macroinvertebrate community composition would shift over time in response to our substrate treatments. 2. Material and methods In order to assess the effects of substrate material and physical complexity on colonisation patterns, controlled substrates were created where the only differences among them were substrate material or physical complexity. These substrates were placed in the Cedar River, a lowland river, in northeast Iowa, USA and sampled to examine colonization by macroinvertebrates. 2.1. Substrates Substrates were created using untreated wood blocks (Southern yellow pine) and concrete bricks. Twenty of each kind of substrate material of the same size—19 cm  9 cm  5.5 cm were created. To increase the density, each wood block was embedded with eight metal rods (each 10  1 cm) (Fig. 3). Eye screws (1 cm diameter) were placed in the center of each end of each block. Screws in the concrete bricks were held in place with a waterproof epoxy. The eye screws were oriented vertically (Fig. 4). Ten blocks and ten bricks were made more physically complex by drilling evenly-spaced holes (~3 cm apart) that were 0.6 cm wide and 0.3 cm deep on the four faces of the block that did not contain eye screws (Fig. 4). Substrates were connected with 30 cm chain; each chain link was 1 cm in diameter and 5 cm long and attached to the eye screws with small plastic zip ties. The chains were not anchored, but provided spacing between the substrates along with additional weight to hold them down. Substrates were chained together in sets of four, each containing a smooth wood block, a complex wood block, a smooth brick, and a complex brick. The order of the substrates in each set was randomized. Ten replicates of each set of substrates for a total of 40 substrates were placed in the Cedar River on 14 December 2012; sets and substrates were oriented parallel to flow. Sets of substrates were dispersed evenly within a 100 m2 area of the Cedar River. Coordinates for the location were 42 430 32.900 N and 92 280 14.300 W, an unshaded area 100 m downstream from a lowhead dam. Wetted width at baseflow was ~70 m, mean depth in the area of the sets was 42 cm, and the ambient streambed was mainly cobble and sand. The immediate area containing the substrates did not develop ice cover during the study period. 2.2. Sampling and data collection

Fig. 1. Distance-based redundancy analysis ordination plots for one (A) or two (B) months of colonization). The first two axes explain the noted percent variances. Each symbol is one substrate (wood and concrete) and ellipses indicate where 95% of the units of the same complexity (smooth, complex) are expected to occur. Legend on A applies to B also.

Five sets of substrates were sampled (5 chains  4 substrates = 20 substrates) on 17 January 2013 and five sets on 11 February 2013 (20 substrates). Mean air temperature was 6.3  C from December 14 to January 17 and 6.1  C from January 17 to February 11. No displacement of substrates was observed during the study period, although one set was lost. To sample each substrate, the connecting zip ties were cut, the substrate was removed from the water while a Surber sampler was held beneath it to catch any detaching organisms, and the substrate with organisms was transferred immediately into a plastic bag with a label. Surplus water was filtered for macroinvertebrates with a 500-mm mesh sieve. Care was taken throughout the operation to minimize potential loss of organisms. Each substrate location was characterized in January by recording depth (cm), lateral distance to the nearest bank (m), and dominant bed substrate (boulders, cobbles, or sand). No change in substrate conditions was noted during the study. Substrates were transported to the lab within the hour where ~200 mL of 75% ethanol was added to each bag to kill and

112

N.D. Molokwu et al. / Ecological Engineering 73 (2014) 109–114

Table 2 Output of SIMPER analysis for after two months of colonisation showing families responsible for 99% of the overall average dissimilarity between the communities in complex and smooth substrates. The bold and underlined values show in which complexity type that family was more abundant. Taxa

Chironomidae Hydropsychidae Simuliidae Nematomorpha Planarians Heptageniidae Taeniopterygidae Hirudea Hydracarina Tabanidae

Average abundance

Ctr%

Complex

Smooth

151.3 40.0 18.8 1.8 1.2 1.1 0.6 0.4 0.3 1.0

106.5 21.7 11.9 1.6 0.7 0.2 0.1 1.1 0.2 0.0

61.1 21.7 10.4 1.4 1.4 1.0 0.6 0.6 0.4 0.4

percent) with a similarity percentages analysis (SIMPER; simper command in VEGAN; Clarke, 1993). Data were explored for differences between treatments in richness and in diversity (S), using the Shannon’s index (H0 ) for the latter. For richness and diversity, we used one-factor ANOVA to test for differences between material–complexity treatments and two sample t-tests for differences between one and two months of colonisation. 3. Results 3.1. Families encountered and diversity

preserve the macroinvertebrates. All visible macroinvertebrates were picked off each substrate with featherweight forceps, with a second person checking to pick any organisms that were missed. Each macroinvertebrate was then identified to the family level using Bouchard (2004).

Twenty two macroinvertebrate families in our wood and concrete substrates were identified (Table 1). Chironomidae was the most represented family (65%), followed by Hydropsychidae (17%) and Simuliidae (13%); other families were less represented (2% each). Exploring data for differences in diversity per substrate unit revealed no differences between treatments (F = 1.14, p = 0.346). However, H0 significantly decreased (t = 4.96, p < 0.001) from the first month (mean  SE; H0 = 1.10  0.04) to the second (0.84  0.04). Richness was also not significantly different between treatments (F = 1.84, p = 0.158) and increased not significantly (t = 1.71, p = 0.095) from the first month (S = 4.75  0.22) to the second (5.58  0.43).

2.3. Data analysis

3.2. Responses to material, complexity, and time of colonisation

Community composition was analyzed in relation to explanatory variables by distance-based redundancy analysis (db-RDA; Legendre and Anderson, 1999; McArdle and Anderson, 2001), based on Bray–Curtis dissimilarities (Bray and Curtis, 1957) on untransformed abundances, with the capscale algorithm in the R package VEGAN 2.0-5 (Dixon, 2003; Oksanen et al., 2012). Colonisation time (one or two months), material (wood, concrete), substrate complexity (smooth, complex), the material–complexity interaction, and habitat variables (depth, lateral distance, bed substrate) were used as predictors. Final models were assessed with a forward variable selection procedure. First, predictors were entered one at a time, their pseudo-F values and significances recorded, and the most significant predictor chosen. Second, all other independent variables were entered and the next most significant was chosen (F-test with anova command in VEGAN; P-values generated by permutation using P < 0.05 criteria). The procedure stopped when no significant term could be added. The pseudo-F ratio obtained by permutation tests (permutest command in VEGAN) was used as a measure of overall db-RDA fit. The contribution of each family was quantified to the average Bray–Curtis dissimilarity between treatments (contributive

Using the alpha-value of 0.05, the forward procedure selected colonization time alone for the final db-RDA, revealing that family community composition significantly differed between one and two months (F = 15.52, p < 0.01, 999 permutations). Thus, for the entire dataset, substrate material (wood, concrete) and substrate complexity (smooth, complex) were not considered significant predictors of colonisation patterns of macroinvertebrates in the Cedar River (Table 3). Running separate analyses for January and February samples showed that colonization time (one versus two months) affected how the macroinvertebrate community responded to our substrate treatments. After one month, the only significant predictor of community was the underlying streambed substrate (F = 4.05, p < 0.01, 999 permutations). After two months, the final

Table 3 Final distance-based redundancy analysis models for macroinvertebrates on substrates treated with two levels of physical complexity. The analysis was run for the entire dataset and separately for the two durations of colonisation. Numbers in parentheses are pseudo-F values, p-values were generated by 999 permutations and p < 0.01 in the 3 models. Substrate material (wood, concrete) was never significant. Variable Entire dataset (15.52) Duration of colonization Residuals One month colonization (4.05) Streambed substrate Residuals Two months colonization (7.46) Water depth Substrate complexity Residuals

df

MS

F

p

1 37

1.31 3.12

15.52

0.01

2 17

0.59 1.24

4.05

0.01

1 1 13

0.29 0.19 0.42

8.99 5.94

0.01 0.01

Main families

200 175 150

complex / smooth Chironomidae Hydropsychidae Simuliidae

125

Count

Overall average dissimilarity: 33.3%. Ctr% = percent of contribution to the overall dissimilarity between complex and smooth materials.

100 75 50 25

One month

Two months

Fig. 2. Mean (95% CI) counts per substrate unit of the three macroinvertebrate families contributing the most to all significant dissimilarities between smooth and complex substrates after one or two months of stream colonization.

N.D. Molokwu et al. / Ecological Engineering 73 (2014) 109–114

113

4. Discussion 4.1. Drivers of colonisation

Fig. 3. The ends of the wood blocks are shown after adding the metal rods but before adding the eye screws.

db-RDA (pseudo-F = 7.46, p = 0.001, 999 permutations) included depth (F = 8.99, p < 0.01) and substrate complexity (F = 5.94, p < 0.01). As after one month, substrate material was not a significant predictor of macroinvertebrate community. Likewise, the material–complexity interaction did not enter the final db-RDA model after two months, indicating that the effect of the substrate complexity was likely comparable for wood and concrete. However, the ordination plot of the db-RDA model applied after two months showed clearly that family composition was dissimilar between smooth and complex substrates (Fig. 1). 3.3. Families’ contribution The SIMPER analysis (Table 2) applied after two months revealed that the families that contributed the most to all significant dissimilarities between smooth and complex materials was Chironomidae, followed by Hydropsychidae and Simuliidae; the three families were more abundant in complex substrates. Overall, the abundance patterns of the main families relative to the substrates’ complexity changed in the second month (Fig. 2). It is especially noteworthy that Hydropsychidae increased significantly in complex substrates only. In general, macroinvertebrate density per substrate unit increased in the second month, which is particularly evident for Chironomidae regardless of the complexity. Lastly, even though Simuliidae was of major importance to the overall dissimilarity between complex and smooth units after two months of colonisation, this abundance did not differ significantly between substrate complexities over time.

The data partially supported our first hypothesis; colonisation patterns of benthic macroinvertebrate responded to differences in substrate complexity. However, in contrast to our expectation based on prior works (e.g., Tullos et al., 2006; Jahnig and Lorenz, 2008) results did not corroborate that substrate material (wood versus concrete) would affect macroinvertebrate community composition (Table 3). Furthermore, the effect of complexity in structuring the patterns of colonisation was similar for wood and concrete. Because wood is an organic substrate and concrete is not, we expected that differing biofilms would develop on their surfaces, which in turn would result in macroinvertebrate– substrate interactions accompanied by shifts in community composition (Magoulick, 1998; Mathooko and Otieno, 2002). Within the two-month time frame of this study, however, our findings can only support a significant response to substrate complexity, in line with the works of O’Connor (1991) for wood substrates and Way et al. (1995) for concrete. 4.2. Effect of colonisation time and seasonality Our second hypothesis that a longer time period for colonisation would lead to greater changes in macroinvertebrate community assembly was clearly supported. Our results suggest that an exposure time 1 month, commonly used in colonisation studies of submerged substrates (Nilsen and Larimore, 1973; Casey and Kendall, 1996; Scealy et al., 2007; Zbinden et al., 2008; Lyon et al., 2009), does not always provide adequate opportunity for a representative community of macroinvertebrates to colonise different treatments. It has been shown that even though one month is sufficient for colonisation to begin, this may not be the case for the time required to detect selectivity for different substrates. Boyero (2003) similarly found that the effect of surface roughness on macroinvertebrate communities colonising cobbles and gravel was highly dependent on the short-term colonisation period (two hours to one week). In the current study, it appears that colonisation within the first month was mainly a factor of underlying streambed substrate, in line with the results of Duan et al. (2009) for colonists of natural streambeds themselves. Macroinvertebrates may initially crawl onto introduced substrates from the immediate surrounding area or they may enter as drift and choose to remain on new substrates that are surrounded by preferred streambed types. In future studies of colonisation on introduced substrates, researchers should not assume that macroinvertebrate assemblages have stabilized simply because rapid colonisation has occurred. In fact, although this study clearly supports the idea that the physical structure of submerged substrates is important (Barnes et al., 2013), we further highlight that the importance of surface complexity may vary with the temporal extent of the investigation. Seasonality is another important aspect of the current study. Most studies of macroinvertebrate–substrate interactions in temperate zones have been conducted in spring through fall (e.g., Tullos et al., 2006; Jahnig and Lorenz, 2008), making winter an understudied period and worthy of further attention. However, this also means that results from winter studies must be applied to other seasons with caution. 4.3. Families’ responses

Fig. 4. Brick substrates contained eye screws, which were held in by a waterproof epoxy. The stack in the background had smooth surfaces whereas those in the foreground were complex with shallow holes.

This study demonstrated that the families contributing the most to differences in the macroinvertebrate assemblages between smooth and complex materials were differentially affected by

114

N.D. Molokwu et al. / Ecological Engineering 73 (2014) 109–114

surface complexity. Contrary to Chironomidae and especially to Hydropsychidae which tended to increase more in complex substrates after two months, surface complexity seems not to have been as important for Simuliids, possibly because smooth surfaces are preferred by these animals for reduced turbulence or better attachment sites (Mackay, 1992). Overall, the number of individuals on complex materials was consistently higher and dominated by Chironomids. Chironomids have been shown to be among the first colonists of submerged substrates in previous studies (McLachlan, 1970; Nilsen and Larimore, 1973; Spänhoff et al., 2000) and may colonise complex substrates more readily (O’Connor, 1991). Regarding Hydropsychidae, our finding of greater numbers on complex substrates is consistent with prior works showing some genera constructed their nets preferentially within pits or grooves rather than on flat surfaces (Downes and Jordan, 1993; Way et al., 1995). 4.4. Restoration concerns Wood and concrete are commonly used materials for restoration projects in stream and rivers (Way et al., 1995; Hrodey et al., 2008). The primary function considered when installing structures is often alterations to geomorphology or fish habitat (Vaz et al., 2013a,b), with macroinvertebrate substrates considered less frequently (Jahnig and Lorenz, 2008). The current study has shown that surface texture can contribute to differences in macroinvertebrate communities as well. If community structure of invertebrates is a concern, we suggest surfaces that have areas that are smooth and areas that are complex. Alternatively, if particular macroinvertebrate species are of concern, restorationists can repeat studies like ours to determine the optimal materials or texture for the species of interest. Acknowledgements We would like to thank the Wartburg College Biology Department for funding this research, Julie Paladino for procuring our supplies and Wartburg Maintenance for lending tools to help build our substrates. We would also like to thank Dr. David McCullough, Amy Kaschke, Jordan Neumann, Kofi Manteaw, and Linda Gondwe for their help with field sampling for this project. References Barnes, J.B., Vaughan, I.P., Ormerod, S.J., 2013. Reappraising the effects of habitat structure on river macroinvertebrates. Freshwater Biol. 58, 2154–2167. Bouchard Jr., R.W., 2004. Guide to Aquatic Invertebrates of the Upper Midwest: Identification Manual for Students, Citizen Monitors, and Aquatic Resource Professionals. University of Minnesota, St. Paul, MN. Boyero, L., 2003. The effect of substrate texture on colonization by stream macroinvertebrates. Ann. Limnol. Int. J. Limnol. 39, 211–218. Bray, J.R., Curtis, J.T., 1957. An ordination of the upland forest communities of southern Wisconsin. Ecol. Monogr. 27, 325–349. Casey, R.J., Kendall, S.A., 1996. Comparisons among colonization of artificial substratum types and natural substratum by benthic macroinvertebrates. Hydrobiologia 341, 57–64. Clarke, K.R., 1993. Non-parametric multivariate analyses of changes in community structure. Aust. J. Ecol. 18, 117–143. Clifford, H.F., Casey, R.J., Saffran, K.A., 1992. Short-term colonization of rough and smooth tiles by benthic macroinvertebrates and algae (chlorophyll-a) in 2 streams. J. N. Am. Benthol. Soc. 11, 304–315.

Couch, C.A., Meyer, J.L., 1992. Development and composition of the epixlyic biofilm in a blackwater river. Freshwater Biol. 27, 43–51. Dixon, P., 2003. VEGAN, a package of R functions for community ecology. J. Veg. Sci. 14, 927–930. Downes, B.J., Jordan, J., 1993. Effects of stone topography on abundance of netbuilding caddisfly larvae and arthropod diversity in an upland stream. Hydrobiologia 252, 163–174. Duan, X., Wang, Z., Xu, M., Zhang, K., 2009. Effect of streambed sediment on benthic ecology. Int. J. Sediment Res. 24, 325–338. Golladay, S.W., Sinsabaugh, R.L., 1991. Biofilm development on leaf and wood surfaces in a boreal river. Freshwater Biol. 25, 437–450. Hrodey, P., Kalb, B., Sutton, T., 2008. Macroinvertebrate community response to large-woody debris additions in small warmwater streams. Hydrobiologia 605 (1), 193–207. Jahnig, S.C., Lorenz, A.W., 2008. Substrate-specific macroinvertebrate diversity patterns following stream restoration. Aquat. Sci. 70, 292–303. Legendre, P., Anderson, M.J., 1999. Distance-based redundancy analysis: testing multispecies responses in multifactorial ecological experiments. Ecol. Monogr. 69, 1–24. Lyon, J.P., Nicol, S.J., Lieschke, J.A., Ramsey, D.S.L., 2009. Does wood type influence the colonisation of this habitat by macroinvertebrates in large lowland rivers? Mar. Freshwater Res. 60, 384–393. Mackay, R.J., 1992. Colonization by lotic macroinvertebrates – a review of processes and patterns. Can. J. Fish. Aquat. Sci. 49, 617–628. Magoulick, D.D., 1998. Effect of wood hardness, condition, texture and substrate type on community structure of stream invertebrates. Am. Midl. Nat. 139, 187–200. Mathooko, J.M., Otieno, C.O., 2002. Does surface textural complexity of woody debris in lotic ecosystems influence their colonization by aquatic invertebrates? Hydrobiologia 489, 11–20. McArdle, B.H., Anderson, M.J., 2001. Fitting multivariate models to community data: a comment on distance-based redundancy analysis. Ecology 82, 290–297. McLachlan, A.J., 1970. Submerged trees as a substrate for benthic fauna in the recently created Lake Kariba (Central Africa). J. Appl. Ecol. 7, 253–266. Monk, D.C., 1976. The distribution of cellulose in freshwater invertebrates of different feeding habits. Freshwater Biol. 6, 471–475. Nilsen, H.C., Larimore, R.W., 1973. Establishment of Invertebrate Communities on Log Substrates in the Kaskaskia River, Illinois. Ecology 54, 366–374. O’Connor, N.A., 1991. The effects of habitat complexity on the macroinvertebrates colonising wood substrates in a lowland stream. Oecologia 85, 504–512. Oksanen, J., Blanchet, F.G., Kindt, R., Legendre, P., Minchin, P.R., O’Hara, R.B., et al., 2012. VEGAN: Community Ecology Package. R package version 2.0-5. http:// CRAN.Rproject.org/package=vegan. Scealy, J.A., Mika, S.J., Boulton, A.J., 2007. Aquatic macroinvertebrate communities on wood in an Australian lowland river: experimental assessment of the interactions of habitat substrate complexity and retained organic matter. Mar. Freshwater Res. 58, 153–165. Schmude, K.L., Jennings, M.J., Otis, K.J., Piette, R.R., 1998. Effects of habitat complexity on macroinvertebrate colonization of artificial substrates in north temperate lakes. J. N. Am. Benthol. Soc. 17 (1), 73–80. Spänhoff, B., Alecke, C., Meyer, E.I., 2000. Colonization of submerged twigs and branches of different wood genera by aquatic macroinvertebrates. Int. Rev. Hydrobiol. 85, 49–66. Tullos, D.D., Penrose, D.L., Jennings, G.D., 2006. Development and application of a bio-indicator for benthic habitat enhancement in the North Carolina Piedmont. Ecol. Eng. 27, 228–241. Vaz, P.G., Merten, E.C., Warren, D.R., Robinson, C.T., Pinto, P., Rego, F.C., 2013a. Which stream wood becomes function al following wildfires? Ecol. Eng. 54, 82–89. Vaz, P.G., Warren, D.R., Merten, E.C., Robinson, C., Pinto, P., Rego, F.C., 2013b. Effects of forest type and stream size on volume and distribution of stream wood: legacies of wildfire in a Euro-Mediterranean context. Freshwater Sci. 32, 126–141. Vaz, P.G., Dias, S., Pinto, P., Merten, E.C., Robinson, C.T., Warren, D.R., Rego, F.C., 2014. Effects of burn status and preconditioning on wood colonization by stream macroinvertebrates. Freshwater Sci. 33, 000. doi:http://dx.doi.org/10.1086/ 676657. Way, C.M., Burky, A.J., Bingham, C.R., Miller, A.C., 1995. Substrate roughness, velocity refuges, and macroinvertebrate abundance on artificial substrates in the lower Mississippi River. J. N. Am. Benthol. Soc. 14 (4), 510–518. Zbinden, M., Hieber, M., Robinson, C.T., Uehlinger, U., 2008. Short-term colonization patterns of macroinvertebrates in alpine streams. Fundam. Appl. Limnol. 171, 75–86.