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Biological Assessment of Streams in the Nashua River Watershed From 1998 Data




introduction


I
Table C1. Description of sampling locations for 1998 Nashua River watershed benthos monitoring.


STATION CODE

DESCRIPTION


1998SL00

Stillwater River upstream from Crowley Road, West Boylston, MA

1998QP00

Quinapoxet River downstream from River Street, Holden (Canada Mills), MA

1998NS17

Nashua River upstream from MWRA-Clinton WWTP, Clinton, MA

1998NS19

Nashua River upstream from Bolton Road, Lancaster, MA

1998NN03

North Nashua River downstream from Mill #9 bridge, Fitchburg, MA

1998NN09

North Nashua River downstream from Falulah Road, Fitchburg, MA

1998NN10A

North Nashua River @ Searstown Mall (just downstream from Rte. 2), Leominster, MA

1998NN13

North Nashua River @ Ponakin Mill (upstream from closed bridge east of Ponakin Rd. dead-end), Lancaster, MA

1998NM23B

Nashua River downstream from McPhearson Road railroad bridge, Ayer/Shirley, MA

1998NT61

Squannacook River downstream from Route 225, Shirley/Groton, MA

1998NM29

Nashua River downstream from covered bridge, Pepperell, MA

1998NT67

Nissitissit River downstream from Prescott Street, Pepperell, MA

1998NT68

Nissitissit River downstream from Canal Street, Pepperell, MA

1998NM30

Nashua River downstream from Route 111, Hollis, NH



n an effort to appraise the biological health of the Nashua River watershed, the Massachusetts Department of Environmental Protection (DEP)/Division of Watershed Management (DWM) collected samples of benthic macroinvertebrate communities in wadable streams across the watershed. The description of the sampling locations appears in Table C1, and the distribution of the locations through the watershed is shown in Figure C1. Of the 14 sampling locations, 10 have been sampled in previous years. To the extent possible, given differences in methods and taxonomic effort, results were examined for signs of improvement in aquatic life conditions.

methods


Sampling and processing procedures are described in detail in the benthos monitoring SOP (Nuzzo 1999) but a brief description is given here. A 100 m reach of stream at each location was sampled by kicking bottom substrates in riffle habitats to dislodge resident invertebrates and capture them in a 500 μm mesh kick-net. Ten kicks in squares approximately 0.46 m x 0.46 m were composited for a total sample area of about 2 m2. Samples were preserved in the field with denatured 95% ethanol, then brought to the DWM lab for processing. Before leaving the sample reach, habitat qualities were scored using a modification of the evaluation procedure in Plafkin, et al. (1989). A copy of the habitat evaluation form appears in Appendix A, Table C-A1; habitat metadata were recorded on forms similar to those in Table C-A2.
Processing entailed distributing a sample in pans, randomly selecting grids within the pans, and sorting specimens from the other materials in the sample until approximately 100 organisms (±10%) were extracted. Specimens were identified to genus or species as allowed by available keys, specimen condition, and specimen maturity. Taxonomic data were analyzed using a modification of Rapid Bioassessment Protocol III (RBP III) metrics and scores (Plafkin, et al. 1989). The modifications were: substitution of “reference site affinity” (RSA) for the Community Loss Index and elimination of the shredder/total ratio (no separate leaf-pack material was collected). The reference site affinity metric is a modification of Percent Model Affinity (Novak and Bode 1992). Instead of using the model’s percentages for Oligochaeta, Ephemeroptera, Plecoptera, Trichoptera, Coleoptera, Chironomidae, and other, these percentages were taken from the reference site data. The RSA score is then calculated as:
100 – (Σ δ x 0.5)

where δ is the difference between the reference percentage and the sample percentage for each taxonomic grouping. RSA percentages convert to RBP III scores as follows: <35% receives 0 points; 2 points in the range from 35 to 49%; 4 points for 50 to 64%; and 6 points if ≥65%.






Figure C1.Map of the Nashua River watershed showing aquatic macroinvertebrate sample collection locations.


results and discussion


Composite habitat scores were used as a way of comparing the overall habitat quality between reference sites and examined sites, and thus weighted the importance of habitat as a determinant in any differences detected between the two sites. The scores were also useful in characterizing habitat degradation. The best possible score for the habitat assessment is 200; the closer to that score, the more optimal the habitat is considered to be for benthos and fishes adapted to riffle-dominated streams. Deficiencies indicated by the scores for the individual habitat categories often can help identify cases of habitat degradation and the causes. The comparative habitat scores and RBP III metrics scores are shown in Table C2. The list of benthos taxa from each site can be found in Appendix B, Table C-B1. The RSA results are shown in Appendix B, Tables C-B2 and C-B3, and the habitat score break-down in Table C-B4.

1998SL00—Stillwater River, Sterling, MA

Habitat


The Stillwater River is one of two major tributaries to Wachusett Reservoir at the Thomas Basin. The site sampled (SL00) was just upstream from Crowley Road in Sterling, MA. This represented a relatively undeveloped catchment within the Nashua watershed and thus was expected to provide a reference as to what aquatic macroinvertebrate communities within the watershed would look like under least disturbed conditions. The drainage is, of course, not without human influence. Areas upstream from SL00 are subject to light residential development, agricultural activities, and road run-off.
Though these attributes made it a good choice for reference purposes, SL00 presented the best habitat for applying the RBP III methodology and yet it was somewhat less than optimal. The methodology is best suited to wadable, riffle-dominated streams with coarse substrates. The sample reach had adequate riffles, though they were somewhat restricted. The substrates were dominated by cobble and gravel, but sand appeared to account for about 30% of the bottom substrate—with moderate accumulations of sandy deposits throughout the reach. There was evidence of erosion and bank instability, becoming severe at the top of the reach, where the river was in proximity to Crowley Road. The steep embankments along the north side of the reach also had areas of moderate erosion, but the banks were judged to be moderately stable overall.
Fish cover was very good, especially near the top of the reach. There was a relatively undisturbed natural meander, and the reach encompassed shallow riffles, as well as deep and shallow pools. Many dace (Rhinichthys sp.) could be seen in the pools.
Attached algae were not observed at the time of sampling. About half the reach had macrophyte coverage. The dominant types were mosses, Myriophyllum sp. (Water Milfoil), Sparganium sp. (Bur Reed), Callitriche sp. (Water Starwort), and Nasturtium officianale (Water Cress). The riparian zone was largely forested, mostly with Pinus strobus (White Pine), Quercus spp. (oaks), and Acer spp. (maples); Kalmia latifolia (Mountain Laurel) was the most prominent shrub, with the presence of Vitis sp. (grapes) notable as well. Herbaceous cover included grasses, Solidago sp. (Goldenrod), Eupatorium sp. (Joe-pye Weed), Lobelia cardinalis (Cardinal Flower), and ferns. The vegetated riparian zone on the north side was 18 m or more. Along the south side the buffer narrowed to virtually no vegetated zone at the top of the reach where it ran along the road.
The overall habitat score for this site was 150.

Benthos


The assemblage of benthic macroinvertebrates collected from SL00 had the highest taxa richness (38) of any of the Nashua watershed sites, and distribution among the taxa was fairly even (greatest presence was 12% of the total). The Hilsenhoff biotic index (HBI) was 4.10, the lowest for any of the stations in this watershed (for the HBI, low value = low pollution stress). The EPT value was 14, a little lower than might be expected from a reference stream, but it was still the second highest from this watershed survey. The other metrics generally had values commonly encountered for reference samples.

1998QP00—Quinapoxet River, Holden, MA

Habitat


The Quinapoxet River is the second major tributary to the Thomas Basin of Wachusett Reservoir. A sampling location upstream from downtown Holden had been sought because it was believed to offer one

Table C2. RBP data summary for 1998 benthic macroinvertebrate samples from the Nashua River watershed. Data from the Stillwater River are used for reference for all sites. In addition, the last two columns of the second page of the table show a comparison with NS19 scored against NS17 as the upstream reference.


STATION #

1998SL00

1998QP00

1998NN03

1998NN09

1998NN10A

1998NN13

1998NS17

1998NS19

STREAM


Stillwater

River


Quinapoxet

River


North Nashua

River


North Nashua

River


North Nashua

River


North Nashua

River


Nashua

River


Nashua

River


HABITAT SCORE

(percent of reference)



150

(100%)


181

(>100%)


142

(95%)


166

(>100%)


166

(>100%)


181

(>100%)


121

(81%)


113

(75%)


TAXA RICHNESS

(percent of reference : score)



38

(6)


34

(89% 6)


25

(66% 4)


19

(50% 2)


14

(37% 0)


19

(50% 2)


28

(74% 4)


21

(55% 2)


BIOTIC INDEX

(percent of reference : score)



4.10

(6)


4.24

(97% 6)


5.37

(76% 4)


5.55

(74% 4)


5.28

(78% 4)


5.44

(75% 4)


5.28

(78% 4)


5.50

(75% 4)


EPT INDEX

(percent of reference : score)



14

(6)


17

(>100% 6)



11

(79% 2)


4

(29% 0)


8

(57% 0)


8

(57% 0)


11

(79% 2)


9

(64% 0)


EPT/CHIRONOMIDAE

(percent of reference : score)



1.06

(6)


2.19

(>100% 6)



1.50

(>100% 6)



1.43

(>100% 6)



2.88

(>100% 6)



1.61

(>100% 6)



1.12

(>100% 6)



2.82

(>100% 6)



SCRAPERS/FILT. COLL.

(percent of reference : score)



0.84

(6)


0.30

(36% 4)


0.30

(36% 4)


0.02

(2% 0)


0.50

(60% 6)


0.60

(71% 6)


0.23

(27% 2)


0.09

(11% 0)


[FILT. COLL./TOTAL]

(not scored)



0.35

0.45

0.58

0.64

0.37

0.36

0.48

0.71

% CONTRIBUTION (dominant)

(score)


12

(6)


17

(6)


20

(4)


28

(4)


17

(6)


27

(4)


12

(6)


21

(4)


RSA—%

(score)


100

(6)


74

(6)


65

(6)


52

(4)


55

(4)


59

(4)


69

(6)


59

(4)


Total Score

42

40

30

20

26

26

30

20

Percent of Reference

100

95

71

48

62

62

71

48

Impact Category

Reference

nonimpacted

slightly

moderately

slightly

slightly

slightly

moderately
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