Macroinvertebrate colonisation of perspex artificial ...

New Zealand Journal of Marine and Freshwater Research

ISSN: 0028-8330 (Print) 1175-8805 (Online) Journal homepage: http://www.tandfonline.com/loi/tnzm20

Macroinvertebrate colonisation of perspex artificial substrates for use in biomonitoring studies I. K. G. Boothroyd & B. N. Dickie To cite this article: I. K. G. Boothroyd & B. N. Dickie (1989) Macroinvertebrate colonisation of perspex artificial substrates for use in biomonitoring studies, New Zealand Journal of Marine and Freshwater Research, 23:4, 467-478, DOI: 10.1080/00288330.1989.9516383 To link to this article: http://dx.doi.org/10.1080/00288330.1989.9516383

Published online: 30 Mar 2010.

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New Zealand Journal of Marine and Freshwater Research, 1989, Vol. 23: 467-478 0028-8330/2304-0467$2.50/0 © Crown copyright 1989

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Macroinvertebrate colonisation of perspex artificial substrates for use in biomonitoring studies

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I. K. G. BOOTHROYD B. N. DICKIE Hauraki Catchment Board P.O. Box 246, Te Aroha, New Zealand Abstract Perspex multiplate artificial substrates were deployed in the Ohinemuri River on two occasions from May to November 1987. A pilot study was conducted to compare the fauna on substrates with that occurring naturally in the benthos, and a second study to investigate the colonisation dynamics. In general, the fauna on artificial substrates was similar to that of natural benthic samples, but with a greater macroinvertebrate density and total taxa number, and dominated by Austrosimuliwn australense and Chironomidae larvae. Colonisation stabilised after 28 days, after which there was little change in diversity. In contrast, equitability decreased, reflecting the greater contribution from A. australense and Chironomidae. There was a steady build-up of fine particulate organic matter (FPOM) on the perspex surface. The relatively low exposure time necessary for equilibrium levels to be reached was attributed to the distinctive characteristics of the New Zealand aquatic fauna. The artificial substrates were slightly more variable in their density estimates than was the natural benthic sampler, but were considered suitable for collecting macroinvertebrates for biomonitoring studies where conventional techniques are impractical or inappropriate, and the stated aims of the use of artificial substrates are clearly defined. Keywords artificial substrata; biomonitoring; pollution; perspex; streams; colonisation; macroinvertebrates

Received 5 April 1989; accepted 4 August 1989

INTRODUCTION Monitoring macroinvertebrates as indicators of water quality has only recently gained much attention in New Zealand. Problems have been the accurate identification of aquatic invertebrates, now largely resolved (Winterbourn & Gregson 1981), although difficulties still exist with some groups; and the difficulty in sampling the diverse and often changing habitat types that occur in flowing waters. Conventional benthic (surber or box) samplers have generally been favoured in swift, shallow waters (Winterbourn 1985), but these may be impractical or impossible to use in slow-flowing, deep rivers, or in rivers with a hardrock substrate. Furthermore, many investigations are handicapped by the need to sample a similar natural substrate at all sites (Mason et al. 1973; Deniseger et al. 1986) and in many rivers, shallow water sites suitable for conventional techniques that occur up stream, may not occur down stream. Artificial substrates can overcome these shortcomings by providing a standard substrate type and area, and can be used in situations where other techniques are unsuitable. Other advantages lie in their light weight, simple design, and ease in handling (Rosenberg & Resh 1982). More importantly, given the contagious nature of stream benthos (Resh 1979), the standard surface area provided by artificial substrates can reduce the variability of density estimates (Beak et al. 1973; Shaw & Minshall 1980; Mason 1981; Rosenberg & Resh 1982; Davenport 1985; Lamberti& Resh 1985), although other workers have shown that this may not be consistently so (Chadwick & Canton 1983; Morin 1985). This aspect is important if the aims of a monitoringprogrammearetobe achieved, and where the exact duplication of natural conditions is less important than the ability to obtain replicate samples at different times and locations (Beak et al. 1973). Whereas artificial substrates have been used for macroinvertebrate surveys in New Zealand (Davenport 1981; Taranaki Catchment Commission 1985), no attempt has been made to evaluate their

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New Zealand Journal of Marine and Freshwater Research, 1989, Vol. 23

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Fig. 1 Location of study site on the Ohinemuri River, Waihi, North Island, New Zealand.

performance and limitations in local streams and rivers. Various factors can influence the composition of the colonising fauna, such as depth in the water column and exposure period (Mason et al. 1973; Meier et al. 1979; Canton & Chadwick 1983). Sufficient time must be allowed for a community to develop before retrieval of artificial substrates from the watercourse. The accumulation of periphyton anddetritus may also greatly influence the colonising community (Roby et al. 1978). The substrate material can become modified during the exposure period, for example by a particular discharge or effluent type. Perspex is an inert material that does not suffer distortion or chemical adsorption, and is sufficiently robust to be used several times. One criticism of using artificial substrates is that the time taken for an equilibrium fauna to develop is unpractically long (Peckarsky 1984). Meier et al. (1979) concluded that the 6-week period generally recommended (Mason 1981; APHA1985) may not always provide adequate opportunity for a truly

representative community to develop. Exposure times of other studies have varied from 3 5 to 84 days. Davenport (1985) suggested a minimum colonisation period of 28 days in New Zealand streams, and Davis & Winterbourn (1977) found that population densities colonising leaf packs approached equilibrium levels after 21-28 days. This paper evaluates the use of perspex multiplate artificial substrates for biomonitoring, and quantifies colonisation by aquatic macroinvertebrates, and determines an optimum period for deployment. STUDY AREA The Ohinemuri River originates in the Waihi Basin, in the Coromandel Peninsula, North Island, New Zealand, and flows west via the Karangahake Gorge to join the Waihou River which then enters the Firth of Thames (Fig. 1). The river has a number of small tributaries in the upper catchment which generally pass through open farmland, but some arise in the bush-clad hills.

Boothroyd & Dickie—Macroinvertebrate biomonitoring

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The study site (37°23'S, 175°52'E) (Fig. 1) was situated west of Waihi where tlle river flows through open pasture. Here the river forms a series of slowflowing pools and faster runs. The site was confined to a fast-flowing run c. 10 m wide and 0.6 m deep. The substrate consisted of a heterogeneous mixture of small rocks, gravel, and sand. Small stands of Potamogeton crispus L. and Lagarosiphon major (Ridley) Moss were present, and the riparian vegetation was dominated by willows (Salix spp.). METHODS Artificial substrates The multiplate artificial substrates, modified from the design of Hester & Dendy (1962), consisted of 14 square plates (76 mm X 76 mm) separated by 25 mm diam. round spacers. The plates were mounted on a central stainless steel bolt, with eight upper spacers of 3 mm thickness and five lower spacers of 6 mm thickness. The plates were constructed of 3 mm clearperspex with surfaces uniformly roughened in a cross-hatched pattern with 80 grade sandpaper. Spacers were also constructed of perspex. The total area available for colonisation on each substrate was 0.16 m2. These were then securely bolted to warratah standards already set in the stream bed, and placed in similar conditions of depth, natural substratum, and shading.

469

Pilot study Ten artificial substrates were deployed in pairs, with one of each pair set just below the water surface and one just above the stream bed. The substrates were left for a period of 50 days (from 9 May 1987 to 8 July 1987) before removal, but were checked weekly when any weed/debris accumulation on the warratah standards was cleared. During this period, mean daily river flow ranged from 4001 s"1 to 20 0001 s"1 but only at 14 days was there any significant difference (P < 0.05) between the mean water velocity passing the upper and lower substrates. To compare the fauna colonising the artificial substrates with that occurring naturally on the stream bed, five replicate samples of the benthos were taken at the same time as artificial substrate retrieval, using a box sampler modified from Hiley et al. (1981). This enclosed an area of 0.05 m2 and samples were collected in a 250 \m mesh net. Colonisation study We deployed 28 multiplate samplers on 25 August 1987 and took four replicates (determined from the pilot study to give a + 20% standard error of the mean: Elliott 1977) at selected periods over a 10week period. A difference between the upper and lower substrates was identified from the pilot study, so for the colonisation study, one of each pair was placed just above the stream bed, with the second

Table 1 Mean water velocities recorded alongside each substrate position (n=8), and maximum and minimum temperatures recorded from the Ohinemuri River, 25 August 1987 (Day 0) to 5 November 1987 (Day 70). Substrate position refers to artificial substrate position in the water column. L, immediately above natural substrate; U, midwater column.

Day 14 28 35 42 49 56 70

Mean velocity (ms" 1 )

Velocity range (ms- 1 )

L U L U —

0.348 0.429 0.502 0.613 -

0.230-0.434 0.313-0.569 0.379-0.678 0.450-0.799 -

L U -

0.268 0.344 -

0.153-0.338 0.269-0.454 -

L U -

0.194 0.276 -

0.122-0.236 0.173-0.305

Substrate position

-

Temperature (°C) Max.

Min.

14

11

15

11

16 16.5

12 13.5

18

13

18

12

18

13

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New Zealand Journal of Marine and Freshwater Research, 1989, Vol. 23 column then those placed just above the natural substrate (Table 1). Temperatures ranged from 11 to 18°C (Table 1). Sample treatment Artificial substrates were retrieved in a sequential manner moving up stream using a 250 jxm mesh hand net, which was placed around the complete artificial substrate before removal to prevent loss of organisms. The substrates were then placed in labelled containers, and in the laboratory were dismantled, each plate scraped clean with a singleedged razor, and all organisms preserved in 70%

Table 2 Total macroinvertebrate numbers collected from upper (US) and lower (LS) artificial substrates (0.16 m2) and benthic samples (B) (0.05 m2) during the pilot study in = 5), August 1987, and from artificial substrates during the colonisation study (n = 4), August-November 1987. Pilot study Aug 1987 Substrate

PLECOPTERA Acroperla trivacuata (Tillyard) Zealandobius furcillatus Tillyard ODONATA Xanthocnemis zealandica (McLachlan)

14

28

35

42

49

56

70

3

3

13

_

_

2

_

_

_

_

23 1

65 3 1

6 4

50

31 1

5

21 1 2

107

-

22

68

47

11

30

17

53

12

96

109

_.

_.

_.

_.

1

_.

_.

_.

_.

_.

l

1

1

2

l

5

2

2

7

11 1

2

-

1

4

1

1

19

1

1

15

59

2

1

3

-

1

-

1

-

1 1 to

1 1

1 I to

B

I

CRUSTACEA Paracalliope fluviatilis (Thomson) ARACHNIDA Acarina EPHEMEROPTERA Coloburiscus humeralis (Walker) Deleatidium sp. Zephlebia Atalophlebioides crormvelli (Phillips)

LS

i

MOLLUSCA Potamopyrgus antipodarum (Gray) Physa cf. acuta Latia neritoides (Gray)

US

i

PLATYHELMNTHES Turbellaria ANNELIDA Naididae Other Oligochaeta Glossiphonia sp.

00 1 1

Taxa

Colonisation study Aug-Nov 1987 No. of days from deployment

ill

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placed in the centre of the water column. The final four substrates were removed on 5 November 1987. As a deployment period of between 28 and 56 days has been recommended by numerous workers, substrates were removed every 7 days during this period, but otherwise were retrieved every 14 days. Daily mean flows ranged from 431 to 55811 s"1, with flows higher during the initial period of the study. The natural basin formation of the catchment, and the frequent cyclonic events locally, mean that the river rises and falls rapidly during rainfall events. Water velocities were, as expected, greater around the artificial substrates placed higher in the water

-

-

-

15

27

42

3

-

3

2

1

-

-

-

Boothroyd & Dickie—Macroinvertebrate biomonitoring

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alcohol. For the colonisation study, samples were also washed through a 90 |om sieve; dry weight and organic content were then measured using standard methods (APHA 1985). When large numbers of organisms occurred, particularly of Chironomidae and Simuliidae, subsampling was carried out using a sample splitter. A variance-to-mean ratio test (Elliott 1977) was carried out to ensure a random distribution of organisms within the sampler (P > 0.05), and enough subsamples taken for a total subsample count of 100 (for 95% CL ± 20%: Elliott 1977). Most samples were reduced to one-eighth or one-sixteenth. Organisms were identified to the lowest possible

Table 2

471

taxon except Oligochaeta (Naididae separated) and Chironomidae, which were identified to family only. Because the box sampler and the perspex substrates sampled different habitats, and provided different surface areas for colonisation and attachment, a statistical comparison is inappropriate. However, the composition of the macroinvertebrate communities from the lower and upper substrates, and the benthos, was compared using Jaccards coefficient of similarity (Hellawell 1978):

J=c/(a + b-c) where a and b are the total number of taxa in each of the two communities, and c is the number of taxa common to both communities.

(Continued) Colonisation study Aug-Nov 1987 No. of days from deployment

Pilot study Aug 1987 Substrate Taxa TRICHOPTERA Aoteapsyche colonica (McLachlan) A. raruraru (McFarlane) Oxyethira albiceps (McLachlan) Paroxyethira hendersoni Mosely Hydrobiosis parumbripennis .McFarlane Rhyacophilidae spp. Psilochorema sp. Hydrobiosella mixta (Cowley) Hudsonema amabilis (McLachlan) Pycnocentrodes sp. Pycnocentrella eruensis Mosely DIPTERA Aphrophila neozelandica (Edwards)

US

LS

B

14

28

35

42

49

56

70

1

1

1

5

48

52

85

81

107

145

-

-

-

-

2

14

30

63

49

71

165

114

35

6

52

106

378

120

114

222

3

0 7

I

2

1

1

6 -

5 -

1 1 -

— 3 -

13 8 1

18

20 8 -

34 11 -

63

2 -

2 -

89 8 -

-

-

-

-

-

-

1

-

-

-

-

1

1

9

492

-

1

-

-

1

-

-

4

9

8

4

5

3

-

2

9

3

1

—

18

1

2

3

3

9

8

3

2152 2589

6435 2100

3092 2632

2218 3992

3240 5711

1930 2917

Austrosimulium australense (Schiner) Chironomidae Empididae Ephydridae

14672 17968 886 867 1117 1055 10 — — —

890 2808

Total taxa Total individuals

lt lt 15963 19089

lt 3758

20 2841

—

— lt 5018

— lt 8793

— lt 6331

— lt 6562

— lt 9438

1 lt 5555

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New Zealand Journal of Marine and Freshwater Research, 1989, Vol. 23

Diversity was measured using the ShannonWiener Diversity Index (H') (Shannon & Weaver 1949; Washington 1984). A modified Hills Ratio (Hill 1973; Peet 1974; Alatabo 1981) was used to measure the evenness component of colonisation. Alatabo (1981) considered the modification important if species diversity is low. A maximum evenness (1.0) arises when all species are equally abundant, and the lower the evenness, the more relative abundances differ.

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RESULTS Pilot study Twenty taxa were recorded from the artificial substrates (Table 2), with the lower substrates collecting a slightly higher mean number of taxa and individuals than the upper deployment. Total density recorded with the benthic sampler was much lower than that of the artificial substrates, although the method sampled a smaller area, whereas the mean taxanumber was greater. OnlyDeleatidiwn,Elmidae beetles, Empididae larvae, and Hirudinea did not colonise the artificial substrates, although these were not common in the benthic fauna. Similarly, four species were exclusive to the artificial substrates and were not found in the benthic samples. Austrosimulium australense larvae dominated the fauna colonising the artificial substrates, but in the natural benthos, Chironomidae and Pycnocentrodes sp. were also very abundant Only two species showed any significant difference between the upper and lower substrates. Both Pycnocentrodes sp. (ANOVA, P < 0.01), and P. antipodarum (P < 0.05) had significantly higher densities on the lower substrates. There was agreater similarity between the benthic community and the upper substrates than between the benthos and the lower substrates. Over 65% of the macroinvertebrate taxa were shared by any two of the substrate types. Greatest similarities (75%) occurred between the upper and lower substrates. Table 3 Inter-sample variability. Mean Jaccard coefficient (7 = % inter-sample similarity) with 95% confidence limits, and co-efficients of variation (CV) for total numbers (N) and taxa richness (5). Upper substrates Lower substrates J 49.9 ± 7.0 CV (N) 0.53 CV (S) 0.20

56.8 ± 6.0 0.28 0.23

Box sampler 67.7 ±4.5 0.24 0.17

Consistency amongst replicates is necessary for both qualitative and quantitative comparisons and is important if variability is to be reduced (Hughes 1975; Elliott 1977). The lower substrates exhibited a greater similarity (7) and a lower variability for total numbers amongst replicates than did the upper substrates (Table 3). This may have been a result of the effect of accumulations of floating plant material and debris around the upper substrates. The box sampler exhibited the greatest similarity and the least variability amongst replicates. Colonisation A total of 28 taxa colonised the substrates over the 70-day period (Table 2). Seven taxa (A. colonica, O. albiceps, Rhyacophilidae spp., A. neozelandica, A. australense, Chironomidae, and P. fluviatilis) were present on all sampling occasions, whereas eight taxa were recorded only once. Numbers of taxa collected ranged from 12 to 18 (Table 2), with the greatest number collected after 35 days. Chironomidae and A australense were abundant at all times, comprising over 90% of the fauna colonising the substrates, and only after 42 and 70 days did another taxon, O. albiceps, make any major contribution (6% and 4%, respectively). Two major peaks in colonisation occurred over the study period (Fig. 2A), the first of which corresponded to the peak density of A. australense (Fig. 2B) at 5 weeks. The decrease after 5 weeks probably represents a major emergence of adults. The second peak corresponded to a peak in chironomiddensity at 8 weeks (Fig. 2C). Colonisation by Chironomidae and by the caddis larvae A. colonica, H. parumbripennis, and O. albiceps (Fig. 3) followed a linear regression (Table4) and increased steadily during the study period. In contrast, densities

Table 4 Regression statistics for colonisation of total numbers and common species on perspex artificial substrates. Statistics calculated according to the equation log iV(+l = a + b log t where N = number of organisms or FPOMattimef.NS, not significant,/>> 0.05;* P 0.05; *P