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Table C2. (Continued). 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 this the second page of the table show a comparison with NS19 scored against NS17 as the upstream reference.



STATION #

1998SL00

1998NM23B

1998NM29

1998NM30

1998NT61

1998NT67

1998NT68

1998NS17

1998NS19


STREAM


Stillwater

River


Nashua River

Nashua River

Nashua River

Squannacook

River


Nissitissit

River


Nissitissit

River


Nashua River

Nashua River

HABITAT SCORE

(percent of reference)



150

(100%)


142

(95%)


130

(87%)


184

(>100%)


136

(91%)


151

(>100%)


139

(93%)


121

(100%)


113

(93%)


TAXA RICHNESS

(percent of reference : score)



38

(6)


20

(53% 2)


21

(55% 2)


28

(74% 4)


19

(50% 2)


36

(95% 6)


29

(76% 4)


28

(6)


21

(75% 4)


BIOTIC INDEX

(percent of reference : score)



4.10

(6)


5.47

(75% 4)


5.64

(73% 4)


5.02

(82% 4)


4.66

(88% 6)


4.71

(87% 6)


4.79

(86% 6)


5.28

(6)


5.50

(96% 6)


EPT INDEX

(percent of reference : score)



14

(6)


9

(64% 0)


5

(36% 0)


10

(71% 2)


9

(64% 0)


12

86% 4)


14

(100% 6)


11

(6)


9

(82% 4)


EPT/CHIRONOMIDAE

(percent of reference : score)



1.06

(6)


3.08

(>100% 6)



0.47

(44% 2)


1.88

(>100% 6)



2.13

(>100% 6)



0.70

(66% 4)


3.09

(>100% 6)



1.12

(6)


2.82

(>100% 6)



SCRAPERS/FILT. COLL.

(percent of reference : score)



0.84

(6)


0.05

(6% 0)


0.09

(11% 0)


0.21

(25% 2)


0.47

(56% 6)


0.69

(82% 6)


0.06

(7% 0)


0.23

(6)


0.09

(39% 4)


[FILT. COLL./TOTAL]

(not scored)



0.35

0.56

0.55

0.54

0.55

0.28

0.73

0.48

0.71

% CONTRIBUTION (dominant)

(score)


12

(6)


24

(4)


17

(6)


9

(6)


24

(4)


9

(6)


26

(4)


12

(6)


21

(4)


RSA—%

(score)


100

(6)


58

(4)


56

(4)


65

(6)


75

(6)


78

(6)


60

(4)


100

(6)


67

(6)


Total Score

42

20

18

30

30

40

30

42

34

Percent of Reference

100

48

43

71

71

95

71

100

81

Impact Category

Reference

moderately

moderately

slightly

slightly

nonimpacted

slightly

Reference

Non-slightly

of the best opportunities for a “least disturbed” watershed reference. Upon our reconnaissance in August of 1998, however, we discovered that not a drop of water flowed from the Quinapoxet Reservoir into the dry riverbed. Farther downstream at Mill Street, Holden, there was still little water, leaving 75% or more of the bed substrates exposed. The first site encountered that had both a sufficient amount of water and suitable habitat was downstream from the lower (more downstream) River Street crossing in Holden.


This site offered excellent instream habitat. Water depth varied from about 0.2 m up to about 0.5 m. Deep and shallow pools were present but the reach was dominated by well developed riffles and runs of varying depths. The bottom substrates were a good mix of boulder, cobble, and gravel. Instream fish cover was also excellent. In fact, nearly all habitat considerations scored in the optimal range. The overall habitat score was 181.
There was little instream vegetation: all of it mosses. There were no visible signs of algal growth but the slippery film on the surface of boulders and cobbles indicated the presence of periphyton. Trees in the riparian buffer zone were Tsuga canadensis (Hemlock), Pinus sp. (Pine), Quercus sp., and Acer sp. The most prominent shrub was Kalmia latifolia. Mosses and ferns dominated the herbaceous layer and the stream bank areas.

Benthos


Taxa richness at this station was 34 and the EPT index was 17—the highest EPT value from any of these survey sites. Though the HBI was slightly higher than at the reference (SL00) it was still comparable. The overall RBP score rated this site as nonimpacted.
In spite of being downstream from an urbanized area this site appeared to have very good water quality as well as excellent habitat.

1998NS17—Nashua River, Clinton, MA

Habitat


This sampling location was on the Nashua River downstream from Wachusett Reservoir. It was chosen as the upstream half of a pair of sites intended to bracket the impacts from the Massachusetts Water Resource Authority’s (MWRA’s) Clinton wastewater treatment plant (WWTP). The channel was relatively straight, with only a gentle sinuosity that may be the normal flow pattern or may be indicative of minor past channel alterations. Remnants of bridge abutments on each side of the river provided evidence of past influences that likely altered channel character; and two well-worn pairs of bike tracks on opposing banks indicate activities that are currently influencing channel morphology.
Flow tended to be swift over a fairly uniform, shallow depth throughout the sample reach. The bottom substrates were marginally optimal, with gravel and sand accounting for about half of the composition and the other half being of cobble size or larger. Sediment deposition affected about 30% of the bottom in the sample reach. Instream cover for fish barely scored as marginal. The overall habitat score was 121.
Vegetation instream covered about 40% of the reach. Recorded for rooted vegetation were Sparganium sp., Potamogeton sp. (Pond Weed), and Callitriche sp. Attached algae were present: some long filamentous greens and some highly branched filamentous types (identified in the lab as Ulothrix sp. and Batrachospermum sp., respectively). The riparian zone of both banks was no more than 6 m deep and showed no signs of recent disturbance other than the aforementioned bike crossings. Beyond the thin buffer of trees and shrubs were fields/pastures; the one on the east looked as if it may have been mowed earlier in the summer. Rhamnus cathartica (Buckthorn), Betula populifolia (Gray Birch), and Acer saccharinum (Silver Maple) were among the trees in the riparian zone. Alnus sp. (Alder), Cornus sp. (Dogwood), Vitis sp., and Spiraea latifolia (Meadow sweet) comprised the shrub layer. The herbaceous layer included Onoclea sensibilis (sensitive fern), Lythrum salicaria (purple loosestrife), Carex stricta, and other Carex spp. (sedges).


Benthos


Nearly every metric applied to the benthos data from NS17 was lower than for the reference. In spite of this, the distribution was fairly even (most abundant taxa ≤12% of total). The total RBP score indicated that this site is slightly impacted. The difference in habitat quality between this site and the reference could account for most of the difference in the RBP score. Potential exists, however, for impacts from an upstream cooling water discharge and NPS contamination.
This reach was also sampled in 1993 (labeled as NS17U) to serve as the upstream bracket on the MWRA/Clinton WWTP. In 1985 (Johnson, et al. 1990) the upstream sample reach was approximately 200 to 300 m farther downstream. (This is bound to be a point of confusion because NS17 in 1998 and NS17U in 1993 were comparably located. In 1993 (Nuzzo, et al. 1997) and 1985 NS17 was used for a location ca. 200 m downstream from the current location of the discharge; but prior to a treatment plant upgrade completed in 1992 it was upstream from the discharge). In Table C3 the 1993 and 1985 RBP scores for the upstream monitoring site (1993NS17U and 1985NS17) are compared against the 1998 upstream data (1998NS17). From this comparison it appears there is little difference in the indicators of aquatic community health except that the EPT index from the 1998 data set is nearly twice as high as in 1993, and almost three times higher than in 1985—a hopeful sign of improving instream conditions.

1998NS19—Nashua River, Lancaster, MA

Habitat


This site was the downstream half of a bracket around the MWRA/Clinton WWTP. The sample reach was located upstream from Bolton Road in Lancaster, about 2.5 km downstream from the effluent discharge. Though a location closer to the discharge was desired, finding suitable habitat was problematic. Even at Bolton Road the riffle habitat was marginal, but was most comparable to the habitat at NS17.
While this site had better developed riffles than NS17 the substrates were again roughly 60% sand and gravel; only about 20% was cobble. There were no indications of channel alteration, but extensive areas of deposition revealed bottom instability over half, or more, of the reach. The reach was littered with tires and other trash. There was a small pile of refuse in the middle of the reach, but for most of the trash no source was immediately evident in the vicinity. Fish cover was limited and mostly provided by snags of fallen trees or large tree limbs, or by the many tires present. The overall habitat score was 113.
Instream vegetation was limited to patches of Callitriche sp. and Potamogeton sp. Much of the herbaceous cover in the riparian zone occurred along the low muddy margins of the river. About 75% of the streambank area was covered with plants including Carex sp., Leersia oryzoides (Rice Cut-grass), Peltandra virginica (Arrow Arum), Boehmeria cylindrica (False Nettle), Bidens sp. (Beggar-ticks), Lythrum salicaria, and Onoclea sensibilis. The upper banks were mostly covered with shrubs and trees. Among the shrub cover was Rhus radicans (Poison Ivy), Rhamnus cathartica, and Vitis sp. The tree components of the riparian zone included Acer saccharinum (Silver Maple), A. rubrum (Red Maple), and Platanus occidentalis (Sycamore). The width of the vegetated riparian zone was pretty good for the most part. On the north side of the river, however, the zone of undisturbed vegetation between the river and a corn field was about 12 m or less, and there were obvious signs of runoff and erosion.

Benthos


Every metric except the ratio of EPT:chironomid abundances scored low when compared to the watershed reference site (SL00). At that, the high EPT abundances were mostly due to three species of the filter-feeding hydropsychid caddisflies. The overall RBP score rated this site as Moderately Impacted. When compared against the station used as the upstream bracket (NS17) of the MWRA/Clinton WWTP, NS19 scores as Non-slightly Impacted (Table C2).
When compared against the downstream monitoring site data from 1993 (1993NS17) and 1985 (1985NS19) it would appear that there has been substantial improvement in the health of these aquatic communities. In Table C3 this is particularly evident in the large difference in most metrics between the 1998NS19 and 1985NS19 datasets. Of particular note is the change from no EPT taxa in 1985 to nine in 1998, and the drop in the HBI from 7.07 in 1985 to 5.50 in 1998. These are indications of improvements in water quality in the segment between the Clinton WWTP and the confluence with the North Branch. The habitat scoring system was not in use in 1985, however, so it must be acknowledged that there may have been differences in habitat qualities that account for at least some of the improvement in the metrics results. While it is unlikely that this is the case, differences in water depth and discharge can make a difference in the availability of suitable habitat and, consequently, the assemblage of organisms capable of colonizing the reach.

1998NN03—North Branch Nashua River, Fitchburg, MA

Habitat


This station was located in the North Branch Nashua River downstream from the bridge to Mill #9 in Fitchburg. This was downstream from the city’s westerly WWTP, several impoundments, and a section of the river that historically had received waste from several paper mills. Immediately upstream from the Mill #9 bridge is a breached dam that has left much of the bottom of the former impoundment exposed. Much of this sediment appears to be layers of paper sludge.
The sample reach had enough gradient to create good riffle/run habitat. Bottom substrates were roughly 80% cobbles and boulders, 20% sand and gravel. The water column was only slightly turbid and there was no buildup of apparent paper waste, as had been recorded during surveys in past years. Channel alteration was obvious here. Among other things, there was a parallel channel between the sample reach and Westminster Street. This channel was dead-ended at the upstream end, separated from the main channel by a long peninsula of large rocky material, and connected with the main channel just below the sample reach. The side-channel had stagnant water in it on our visit and probably functions as a settling basin for road run-off. Stable fish cover in the sample reach was provided by the larger rocky material and some fallen trees, but was somewhat limited. The overall habitat score was 142.
Filamentous algae and mosses were noted in the reach, but coverage was sparse. The vegetative protection of the banks was pretty good and provided mostly by trees and ferns and to a much lesser extent by shrubs. Tree species recorded were Quercus rubra (Red Oak), Acer rubrum, and Fraxinus americana (White Ash). Shrubs observed were Ilex verticillata (Winterberry), Cornus sp. (Dogwood), Cephalanthus occidentalis (Buttonbush), and Vitis sp. Some Carex sp. was also observed.

Benthos


Five of the seven RBP metrics lost points relative to the reference station. The largest point loss was on the EPT index. The overall RBP score categorized the site as: Slightly Impacted.
Referring back to 1985 data for this site it would appear that a dramatic improvement has taken place. This is evident in nearly all of the metrics, but perhaps most striking is the increase in the EPT index from zero to 11 and in the drop in the HBI from 7.08 to 5.37. As with NS19, the lack of habitat scoring data makes it impossible to weight the importance of any differences in habitat qualities between the two years that may have existed.

1998NN09—North Branch Nashua River, Fitchburg, MA

Habitat


NN09 was downstream from Falulah Road, downstream from downtown Fitchburg, yet upstream from the Fitchburg easterly WWTP. The channel was about 12 m wide, two thirds of which was shallowly submerged, with little or no perceptible current; the other third carried most of the volume, creating riffles ranging in depth up to about 0.75 m. The bottom substrates were mostly cobbles. Little more than 10% of the reach had useful, stable fish cover. The stream banks were judged to be moderately stable, in part due to rip-rap stabilizing portions of the banks. There were small areas of erosion, however, and evidence of surge overflow trailing down the embankment to the water’s edge from a sewer manhole cover. The overall habitat score was 166.
There were no rooted plants observed instream, but patches of algae were present. Among these were long streamers of the filamentous green alga, Mougeotia sp., and several species of diatoms (long chains of Fragilaria sp., Synedra sp., and undetermined small pennates). The vegetative protection of the banks was very good and the width of the vegetated riparian zone was 18 m or more. The riparian zone was mostly wooded and included Catalpa speciosa (Catalpa), Robinia pseudoacacia (Black Locust), Betula papyrifera, Fraxinus sp., Acer rubrum, Salix spp. (willows), and Platanus occidentalis. The only shrub

Table C3. Summary of RBP scores for three years of samples bracketing the Clinton WWTP. Upstream stations are compared against the 1998 upstream site (1998NS17) and downstream sites are compared against the 1998 downstream site (1998NS19).


Station

1998NS17

1993NS17U

1985NS17




1998NS19

1993NS17

1985NS19

Nashua River @:

Upstream from

Clinton WWTP



Upstream from

Clinton WWTP



Upstream from

Clinton WWTP






Bolton Rd.,

Lancaster



Downstream from

Clinton WWTP



Bolton Rd.,

Lancaster



Habitat Score

121

140

Not scored




113

143

Not scored

Taxa Richness

(% of Ref. . . . score)



28

(100 6)


29

(>100 6)


22

(79 4)





21

(100 6)


19

(90 6)


9

(43 2)


Biotic Index

(% of Ref. . . . score)



5.28

(100 6)


5.59

(94 6)


6.44

(82 4)





5.50

(100 6)


5.45

(>100 6)


7.07

(78 4)


EPT Index

(% of Ref. . . . score)



11

(100 6)


6

(55 0)


4

(36 0)





9

(100 6)


5

(56 0)


0

(0 0)


EPT/Chironomidae

(% of Ref. . . . score)



1.12

(100 6)


0.95

(85 6)


1.03

(92 6)





2.82

(100 6)


3.89

(>100 6)


0

(0 0)


SC/FC

(% of Ref. . . . score)



0.23

(100 6)


0.09

(39 4)


0.58

(>100 6)





0.09

(100 6)


0.05

(56 6)


0

(0 0)


[FC/Total]

(not scored)



0.48

0.34

0.22




0.71


0.63

0.01

% Contribution (dominant)

(score)


12

( 6)


17

( 6)


19

( 6)





21

( 4)


27

( 4)


21

( 4)


RSA

(score)


Ref.

( 6)


94%

( 6)


65%

( 6)





Ref.

( 6)


81%
( 6)

32%

( 0)


Total Score

42

34

32




40

34

10

% of Ref.

100

81

76




100

85

25

Impact Category

Ref.

Non.

Slightly




Ref.

Non.

Moderately

Reference:

1998NS17

1998NS17

1998NS17




1998NS19

1998NS19

1998NS19

recorded was Cephalanthus occidentalis. Among the herbaceous growth was false bamboo or knotweed (a species of Polygonum sp.), Eupatorium sp., Lythrum salicaria, Impatiens sp. (Jewel Weed), and Phalaris arundinacea (Reed Canary Grass).



Benthos


With the exception of EPT:chironomid abundance ratio the performance of all the metrics resulted in point reductions. The preponderance of EPT individuals was nearly all accounted for by three species of filter-feeding hydropsychid caddisflies. The EPT index, in fact, was only four—the lowest of any of the stations sampled. Also notable, the total richness was only half that of the reference and the HBI was the second-highest encountered during this watershed survey. Inasmuch as the habitat at this site scored better than that for the Stillwater River reference station (1998SL00), the assessment result was surely related to water quality and not habitat deficiencies. The overall RBP score was: Moderately Impacted.

1998NN10A—North Branch Nashua River, Leominster, MA

Habitat


Located just downstream from Route 2 in Leominster, and about 1.3 km downstream from the Fitchburg Easterly WWTP, the water at this site had a grey turbidity and carried sewage odors. There was a swift current over large rocky substrates dominated by boulders and cobbles. Depth was variable in the riffles; pools tended to be shallow. The banks were judged to be moderately stable, with some evidence of scour taking place at high water. Cover for fish was adequate but available in less than 50% of the reach. The overall habitat score was 166.
There were no rooted aquatic plants observed in the sample reach. The slipperiness of the rocks indicated the presence of thin-film periphyton but no easily collected accumulations were seen. The vegetative protection of the banks was quite good. The riparian zone of both banks was wooded and included trees such as Platanus occidentalis, Acer saccharinum, Populus sp. (Aspen), and Catalpa speciosa; the most apparent shrub was Cornus sp. The understory included false bamboo (a Polygonum sp.), some hydrophilic grasses, and sparse coverage of low herbaceous growth (not determined).

Benthos


This station had the lowest richness (less than half that of the reference) of any of the sites in this watershed survey and a greatly reduced EPT index. The contribution of the most abundant taxon (17%) was indicative of a fairly even distribution, but hydropsychid caddisflies (filter feeders, three species) dominated the assemblage (37%). The emphasis on filter feeding may be indicative of a high loading of suspended solids. The overall RBP score category was: Slightly Impacted.
Both the comparison of raw metric values and the scores relative to the respective references (the Stillwater River in 1998 and the Whitman River in 1985) show evidence of improved water quality since the 1985 biomonitoring was conducted. Based on the 1985 data (Johnson, et al. 1990) the assessment indicated the reach was slightly to moderately impacted. While the total richness was higher in the 1985 analysis, the EPT index was only half of what was encountered in 1998. Also notable was the higher ratio of scrapers to filtering collectors seen in the 1998 data. Though these observations are encouraging, the differences are small and the comparisons are weakened somewhat by the lack of a common reference. Nevertheless, it is worth noting that habitat characteristics have been fairly consistent in this reach between each of the sampling events, irrespective of any differences in discharge there may have been. This reach has always provided ample riffle habitat with coarse substrates and adequate depth.

1998NN13—North Branch Nashua River, Lancaster, MA

Habitat


The sample reach was located upstream from the closed bridge that served a former section of Ponakin Road west of Route 70 at Ponakin Mill. The water was turbid and had a sewage odor. The reach was dominated by fast-flowing water. The bottom substrates were about 40% boulders, 30% cobble/gravel, and 30% sand. The channel was about 25 m wide and depths ranged from 0.25 m to 0.5 m. The stability of the banks was very good, with no evidence of erosion or any readily apparent indications of nonpoint sources of pollution. The available cover for fish was very good. The overall habitat score was 181 (the highest score recorded in this survey).
Instream vegetation was limited to mosses and thin-film periphyton. Trees in the riparian zone included Platanus occidentalis, Acer saccharinum, and Acer rubrum. The only shrubs noted were Cornus sp. and Lonicera tartarica (Tartarian Honeysuckle). Except for false bamboo (a Polygonum sp.) there was no herbaceous cover to speak of.

Benthos


At this site, too, the richness was merely half that of the reference station, in spite of a much better habitat score. The relatively high HBI, low EPT index, and moderate dominance by a single taxon resulted in a score in the range for Slightly Impacted.

1998NM23B—Nashua River, Shirley/Ayer, MA

Habitat


This station was downstream from a railroad bridge and along side of McPhearson Road, Ayer, MA (the river is the boundary between Shirley and Ayer). The water was turbid and had sewage odors. There were well developed riffles and runs but the pools tended to be somewhat restricted. Water depth ranged from about 0.25-0.5 m. The cobble-dominated bottom substrates were excellent for benthic invertebrate populations. The channel was about 40 m wide along this stretch. Bank stability was marginal, with signs of moderate to heavy erosion. There were obvious signs of nonpoint source pollution in the form of runoff from McPhearson Road in the vicinity of the railroad bridge. Stable fish cover was available in about half of the sample reach. The overall habitat score was 142.
Aquatic macrophytes were well established throughout this reach. Lemna sp. (Duckweed) was present floating at the water’s surface. The many rooted macrophytes included: Isoetes sp., P. crispus and other Potamogeton spp., Sparganium sp., Elodea sp. (Water-weed), Myriophyllum spp., Callitriche sp., and Peltandra virginica. The riparian buffer between McPhearson Road and the river was very narrow, covered mostly by Rhus radicans. There was other shrubby cover—Viburnum dentatum (Arrow-wood) and Cornus sp.—and a few scattered trees—Acer saccharinum, A. rubrum, and Betula sp. In the herbaceous layer Glyceria sp. and Carex sp. were present along with Bidens sp., Lythrum salicaria, and Onoclea sensibilis. At the opposite edge of the river there was a sparsely vegetated margin against steep, high, sandy banks. About 30% of this bank had obvious areas of erosion. At the top of the bank was a meadow and woods.

Benthos


Every metric except the EPT:chironomid ratio scored poorly against the reference. While EPT individuals were much more plentiful than chironomids the EPT index was relatively low. The overall RBP score category for this site was: Moderately Impacted.

1998NT61—Squanacook River, Shirley/Groton, MA

Habitat


A major tributary to the Nashua River, the Squanacook River enters the Nashua downstream from NM23B at the point where Shirley, Groton, and Ayer come together. The Squanacook is a relatively low gradient stream with several impounded sections as it makes its way through Townsend and along the Shirley/Groton line. NT61 was a short (ca. 200 m), steep section of the river downstream from the dam at Route 225. There were well developed riffles over cobble-dominated substrates. The water depth was shallow throughout. This segment ran between steep, high slopes. There was evidence of moderate to heavy erosion. Stable cover for fish was limited. The overall habitat score was 136.
The only instream vegetation observed were occasional growths of mosses. In the riparian zone the trees Carya sp. (Hickory) and Acer rubrum were present. The shrubs recorded were Rhamnus cathartica, Hammamelis virginiana (Witch hazel), Ilex verticillata (winterberry), and Vitis sp. There was very sparse coverage in the understory by hydrophilic grasses, Urtica sp. (Nettle), and Osmunda regalis (Royal fern).

Benthos


The richness in this sample was only half that of the reference station, and the EPT index was reduced enough that it scored zero. There was slight hyperdominance by a filter-feeding caddisfly and more than half of the assemblage was filter-feeders. This is not unexpected, however, because the sampling location was directly downstream from an impoundment and filter-feeding caddisflies are often abundant in such situations. The overall RBP score rated this site: Slightly Impacted.

1998NM29—Nashua River, Pepperell, MA

Habitat


This sample reach was immediately downstream from the Groton Street covered bridge in East Pepperell, MA. It was also downstream from the Pepperell Pond dam and the Pepperell Paper Company effluent discharge. The water column within the sample reach was so densely turbid as to be nearly opaque. By walking upstream, however, it was readily apparent that the water upstream from the Pepperell Paper discharge was reasonably clear. Because of the mid-stream injection of the effluent, the turbidity was evenly mixed across the width of the river by the time it passed under the bridge. The water had a rich organic, fishy odor.
The reach was dominated by well developed riffles and runs flowing over coarse substrates, mostly cobble and boulder. The steepness of both embankments contributed to their instability and susceptibility to erosion, but this was exacerbated by disturbances within the riparian buffer zone that reduced or nearly eliminated bank vegetative protection. In particular, a horse farm on one bank has left the upslope areas nearly devoid of vegetative cover and the effects of runoff were obvious both over the slope of the bank and instream. Fish cover was available only in about 25% of the sample reach. The overall habitat score was 130.
The diatom Melosira sp. was collected from rocks instream. A sample of moss in the reach revealed that it was serving as substrate for several species of microbes: the diatoms Fragilaria sp., Synedra sp., and some undetermined pennates; the greens Pediastrum sp., Cosmarium sp., and Scenedesmus sp.; the blue green Lyngbya sp.; and undetermined fungal hyphae. Lemna sp. and Wolfia sp. were present on the water’s surface. The other macrophytes recorded were Potamogeton sp., Myriophyllum sp. The vegetation in the 18 m riparian buffer zone was sparse but included Acer saccharinum, A. rubrum, and the shrub, Cornus sp. In the herbaceous layer were Carex sp., hydrophilic grasses, and Lythrum salicaria.

Benthos


This site had the highest HBI (5.64), and the second lowest EPT index (5). The distribution among taxa appeared to be fairly even, with the most abundant taxon accounting for 17% of the assemblage; all other metrics scored low. This site had the lowest overall RBP score (18; 43% of the reference) from this watershed survey. It’s rating was: Moderately Impacted.

1998NT67—Nissitissit River (Prescott St.), Pepperell, MA

Habitat


The Nissitissit River is the last large tributary to enter the Nashua River before its confluence with the Merrimack River. The Nissitissit drains parts of Mason, Brookline, and Hollis, NH and most of Pepperell, MA west of the Nashua River. The Nissitissit empties into the Nashua less than a kilometer downstream from the Groton Street bridge and upstream from the Pepperell municipal WWTP. NT67 was about 3 km downstream from the state line (about 300 m downstream from Prescott Street) and offered good riffle habitat with lots of cobble. The water depth was shallow throughout. The water column was clear and there was no evidence of erosion or nonpoint sources of pollution along the reach. Availability of fish cover was limited. The overall habitat score was 151.
Bank stability was very good and the banks were well protected with vegetation. Both banks were wooded and offered a buffer of undisturbed vegetation in excess of 18 m. The mixed stand of trees included Acer rubrum, Quercus rubra, Carpinus caroliniana (Hornbeam), and Pinus strobus. Shrubs recorded at this site were Ilex verticilata, Viburnum dentatum, and Vitis sp. Grasses and herbs in the riparian zone included Carex sp., Leersia oryzoides, Lobelia cardinalis, Hypericum sp. (St. John’s-wort), Sium sp. (Water-parsnip), Thelypteris palustris (Marsh fern), and Osmunda regalis. Aquatic vascular plants instream or at the margins were Mimulus sp. (Monkey-flower), Myosotis sp. (Forget-me-not), Sparganium sp., Nasturtium sp., Eleocharis sp., Callitriche sp., Potamogeton sp., and Elatine sp. (Waterwort).

Benthos


All metrics scored well except for the two related to EPT taxa. The assemblage was remarkably evenly distributed, with no taxon making up more than 9% of the total. The overall RBP score was: nonimpacted.

1998NT68—Nissitissit River (Mill St.), Pepperell, MA

Habitat


This site was approximately 3 km downstream from NT67 in a more residentially developed section of Pepperell and with the parking lot of an oil loading facility abutting a portion of one stream bank. The substrates were mostly cobble. The reach had a good sequence of alternating riffles and pools, mostly shallow, with deep riffles present but quite restricted. There was moderate erosion along one of the banks and it was recognized that the parking lot of the oil company was a potential nonpoint source of pollution. Fish cover was available in less than 30% of the reach. The overall habitat score was 139.
One bank was stable, with little evidence of erosion or bank failure, with good vegetative protection, and with a buffer zone of undisturbed vegetation that was about 15 m or so. The other bank had many areas of erosion, only about 80% of the bank benefited from vegetative protection, and the vegetative buffer zone was only about 10 m wide. On the list of woody vegetation observed were Acer rubrum, Platanus occidentalis, Ilex verticilata, Cephalanthus occidentalis, Vitis sp., and Cornus sp. In the understory or the more open areas were Phalaris arundinacea, Carex stricta, Lobelia cardinalis, Eupatorium sp., and Thelypteris palustris.

Benthos


The most striking aspect of this assemblage was the very high percentage of filter-feeders, leading to a very low ratio of scrapers to filtering collectors. Slight hyperdominance and reduced richness relative to the reference also accounted for point losses. The overall rating from the RBP score was: Slightly Impacted. Relative to its upstream counterpart (NT67), however, the metrics were quite comparable. But even in this comparison the preponderance of filtering collectors skewed the assemblage enough to result in a rating of slightly impacted.

1998NM30—Nashua River, Hollis, NH

Habitat


The final sampling location on the Nashua River was downstream from Route 111 in Hollis, NH. The channel was approximately 35 m wide, and because the eastern half was too deep, sampling was conducted in the western half of the channel. The substrate encountered here was about half bedrock and nearly all the rest being accounted for by cobble and boulder (no appreciable amounts of sand and gravel). There was quite a variety of water depth and velocity combinations through this reach. Bank stability generally appeared good though there was slight evidence of erosion and there was the potential of NPS pollution from road run-off and adjacent lawns on one bank. Instream cover for fish was regarded as excellent, provided by plenty of deeper water areas with large boulders and rock outcroppings. The overall habitat score was 184 (the highest recorded in this watershed survey).
The banks were generally well protected with vegetation. The vegetated buffer zone was greater than 18 m on one bank but only about 15 m on the other. Woody cover in the buffer zone included Acer saccharum (Sugar Maple), Pinus strobus, Cornus sp., Alnus sp. (Alder), and Cephalanthus occidentalis. Phalaris sp., Bidens sp., and Lythrum salicaria were found providing the grass/herbaceous cover.
In spite of the dominance of rock substrates Elodea sp. and Myriophyllum sp. were recorded in this reach. The duckweeds Lemna sp. and Wolfia sp. could be seen on the water’s surface. Some floating aggregates of algae were found as well as attached filamentous forms. These were later identified in the laboratory as the green algae Ulothrix sp. and Spirogyra sp.

Benthos


No taxon contributed more than 9% of the assemblage, indicating a very even distribution of individuals among the taxa. All other metrics, however, lost points for poor performance against the reference. The overall RBP rating for this station was: Slightly Impacted. For the most part the RBP results from 1998 looked very similar to those from 1985 (Johnson, et al. 1990), with perhaps some metrics suggesting a slight improvement in conditions.

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