Protection and Management Plan for the Millbrook Marsh Nature Center

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Stream Fauna

Stream Macroinvertebrates

Both Thompson Run and Slab Cabin Run support a moderately depauperate macroinvertebrate fauna. Midge larvae (Chironornidae) and blackfly larvae (Simuliidae) were the most common taxa in Thompson Run, while chironomids and hydropsychid caddisflies were most common in Slab Cabin Run (Tables 1 and 2). Slab Cabin Run had a richer invertebrate fauna, with an average taxa richness of 17.2, as compared to 11.0 in Thompson Run.

REP Ill showed slight to moderate disturbances in the macroinvertebrate community (Table 3). MI stations except Station 2 were "Moderately impaired," while Station 2 was "Slightly impaired." The scrapers/ftlterers, EPT/Chironomidae, and % dominant taxon indices suggest a generally unbalanced community. Low values for scrapers/filterers at all stations except Station 4 indicate a predominance of filtering collectors and suggest a disproportionate amount of fine particulate organic matter suspended in the water column. An overabundance of pollution-tolerant chironomids was shown by the BPT/Chironomidae index. The most dominant taxon made up a large portion of the total macroinvertebrate assemblage at each station (% dominant taxon). Ideally, the most dominant taxon should contribute less than 20% to a healthy, balanced macroinvertebrate community.
 

July 1997

 

October 1997

 

Thompson Run

Slab Cabin Run

 

Thompson Run

Slab Cabin Run

Station

1

5

6

2

3

4

 

1

5

6

2

3

4

Insecta

                         

Ephemeroptera

                         

Baetidae

                         

Baetis sp.

23

8

20

16

2

3

 

51

21

22

7

8

3

Heptageniidae

                         

Stenonema sp.

                   

15

   

Tricorythodae

                         

Tricorythodes sp.

         

3

             

Trichoptera

                         

Glossosomatidae

                         

Glossosoma sp.

                       

1

Hydropsychidae

     

1

4

               

Ceratopsyche sp.

 

4

9

123

57

11

     

1

57

77

3

Cheumatopsyche sp

     

4

 

20

       

2

2

3

Hydropsyche sp.

 

1

2

18

 

2

       

29

6

3

Hydroptilidae

                         

Hydroptila sp.

                       

1

Ochrotrichia sp.

2

3

3

4

8

2

             

Limnephilidae

                         

Pycnopsyche

                     

1

 

Psychomyiidae

                         

Psychomyiia sp.

     

5

                 

Rhyacophilidae

                         

Rhyacophila sp.

                   

2

   

Diptera

                         

Ceratopogonidae

                         

Forcipomyia sp.

         

4

             

Chironomidae

96

131

161

45

88

156

 

158

196

139

32

85

56

Empididae

                         

Chelifera sp.

 

1

                     

Muscidae

15

2

7

       

9

11

4

1

2

 

Nymphomyiidae

                         

Nymphomyiia sp.

1

                       

Station

1

5

6

2

3

4

 

1

5

6

2

3

4

Simuliidae

143

103

72

2

138

5

 

67

65

113

8

55

24

Tabanidae

                       

1

Chrysops sp.

         

6

             

Tipulidae

                         

Antocha sp.

 

2

4

44

4

3

 

1

 

2

16

28

7

Tipula sp.

             

1

2

   

2

1

Coleoptera

                         

Dytiscidae

                         

Agabus sp.

 

1

                     

Elmidae

                         

Dubiraphia sp.

     

2

 

1

       

7

3

6

Optioservus sp.

     

7

1

42

       

36

2

5

Stenelmis sp.

     

2

 

14

       

2

   

Psephenidae

                         

Ectopria sp.

         

1

         

1

 

Psephenus sp.

     

21

 

1

       

15

   

Hemiptera

                   

1

   

Corixidae

                         

Trichocorixa

                     

1

 

Crustacea

                         

Amphipoda

                         

Gammaridae

                         

Gammarus minus

2

9

3

 

3

     

2

3

 

2

 

Talitridae

                         

Hyalella azteca

         

6

             

Decapoda

                   

1

   

Isopoda

                         

Asellidae

                         

Asellus sp.

     

6

 

8

   

1

 

19

9

12

Turbellaria

             

2

       

9

Tricladida

                         

Planariidae

1

5

 

2

 

1

             

Station

1

5

6

2

3

4

 

1

5

6

2

3

4

Cura foremanii

 

2

               

47

   

Hymanella retenuova

 

10

1

                   

Oligochaeta

14

18

23

 

3

10

 

11

11

13

1

15

155

Gastropoda

               

3

       

Basommatophora

                         

Physidae

         

1

     

1

 

1

2

Planorbidae

2

1

             

2

     

Bivalvia

                         

Veneroida

 

3

                     

Pisidiidae

                       

9

Pisidium sp.

1

                   

2

 

Total

300

304

305

302

308

300

 

301

317

306

300

305

305

Species Richness

11

17

11

16

10

21

 

8

9

10

19

19

18

26
Raw Scores:

Stations

 

1

2

3

4

5

6

Ref

Taxa Richness

11

16

10

21

17

11

19

Modified 11131

5.91

4.18

5.49

5.46

5.59

5.86

4.05

Scrapers/Filterers

0.18

0.36

0.02

1.73

0.08

0.24

30.50

EPT/Chironomidae

0.26

3.80

0.81

0.26

0.12

0.21

1.46

% Dominant Taxon

47.67

40.73

44.81

52.00

43.09

52.79

36.20

EPT Index

2

7

4

6

4

4

10

Community Loss Index

1.27

0.94

1.30

0.57

0.71

1.18

--------

Percent Comparison to Reference:

Taxa Richness

57.89

84.21

52.63

110.53

89.47

57.89

------

Modified HBI

68.53

96.89

73.77

74.18

72.45

69.11

------

Scrapers/Filterers

0.59

1.18

0.07

5.67

0.26

0.79

------

EPT Chironomidae

17.81

260.27

55.48

17.81

8.22

14.38

------

% Dominant Taxon

47.67

40.73

44.81

52.00

43.09

52.79

------

EPT Index

20.00

70.00

40.00

60.00

40.00

40.00

------

Community Loss Index

1.27

0.94

1.30

0.57

0.71

1.18

------

Biological Condition Scores:

Taxa Richness

2

6

2

6

6

2

6

Modified HBI

2

6

4

4

4

2

6

Scrapers/Filterers

0

0

(I

(I

0

0

6

EPT Chironomidae

0

6

4

()

(I

(I

6

% Dominant Taxon

0

0

(I

(I

(I

(I

2

EPT Index

0

2

C)

C)

0

C)

6

Community Loss Index

4

4

4

4

4

4

6

Totals

8

24

14

14

14

8

38

Bioassessment (level of impairment:

Moderate

Slight

Moderate

Moderate

Moderate

Moderate

Not Impaired

27

The number of generally pollution-intolerant taxa (mayflies, stoneflies, and caddisflies) was low at all stations (EPT index). The Hilsenhoff Biotic Index (HBI) suggests that all stations except Station 2 are affected to some degree by organic pollution. Intermediate values of the Community Loss Index at all stations indicate moderate dissimilarity from the reference station.

Lipton (1998) compared macroinvertebrate communities for samples collected in 1997 during this study with those collected about 20 years ago. Although the location of sampling sites varied, the ecological integrity of these biological communities in the Millbrook streams appears to be similar, perhaps slightly better. The earlier samples were collected before the University’s sewage treatment plant cased discharging into Thompson Run in 1983, so the macroinvertebrates were subjected to a higher load of organic pollution. More recently, increasing stormwater discharges may have prevented further recovery. Overall, the aquatic macroinvertebrate communities have remained slightly to moderately impaired. These conditions are unlikely to improve unless significant reductions in stormwater quantity and improvements in stormwater quality occur in the portions of the Spring Creek watershed that are upstream of Millbrook Marsh.

Fish.

Wild brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), white suckers (Catostomus commersoni), and slimy sculpins (Cottus cognatus) were found in both Thompson Run and Lower Slab Cabin Run (Tables 4, 5, 6, and 7). Wild brown trout, white suckers, blacknosed dace (Rhinichthys atratulus), and creek chubs (Semotilus atromaculatus) were found in Upper Slab Cabin Run (Tables 4, 5, 6, and 7).

Density and biomass estimates were made for brown trout only. Rainbow trout were either not captured during both electrofishing passes (Upper Slab Cabin Run), not captured on the second pass (Thompson Run), or only one was captured on the second pass (Lower Slab Cabin Run). Density and biomass estimates of brown trout were highest in Thompson Run (4800/ ha, 423 kg/ha; Table 5), followed by Lower Slab Cabin Run (983/ha, 106 kg/ha; Table 6) and Upper Slab Cabin Run (761/ha, 106 kg/ha; Table 7). Recruitment of young-of-the-year (1997) fish was good in all 3 stream reaches, as evidenced by the first peak in length-frequency distribution of fish 139 mm and smaller (Fig. 2). A gap in fish 139-169mm long (1 year olds) indicates poor recruitment during 1996, most likely due to the severe flooding that occurred early that year.

Fig2.JPG (203426 bytes)

Fig. 2. Length-frequency distributions for brown trout from (a) Thompson, (b) Lower Slab
Cabin, and (c) Upper Slab Cabin Runs (Files TR97.WD4, SCRD97.WK4, SCRU97.WK4).

Table 4, Table 5, and Table 6 combined into Electrofishing data for (a) brown and (b) rainbow trout from Thompson Run – August 8 and 11, 1997, Run 1, August 14, 1997, Run 2, File TR97.WK4;  (a) brown and (b) rainbow trout from Lower Slab Cabin Run – August 5 and 7, 1997, Run 1, August 14, 1997, Run 2, File SCRD97.WK4;  (a) brown trout from Upper Slab Cabin Run – August 7 and 8, 1997, Run 1, August 14, 1997, Run 2, File SCRU97.WK4

(a)1997 Electrofishing Data for Brown Trout in Millbrook Marsh Streams

Brown Trout

Thompson Run

Lower Slab Cabin Run

Upper Slab Cabin Run

Length

Group

(mm)

Total

caught

(N)

Mean

Weight

(g)

g*N

(kg)

Total

caught

(N)

Mean

weight

(g)

g*N

(kg)

Total

caught

(N)

Mean

weight

(g)

g*N

(kg)

60-69

4

0

0.00

70-79

8

4

0.16

3

4

0.02

13

4

0.09

80-89

39

7

1.38

20

7

0.26

22

7

0.26

90-99

40

14

2.83

33

14

0.84

17

14

0.41

100-109

51

16

4.13

22

16

0.64

10

16

0.27

110-119

38

18

3.46

5

18

0.16

1

18

0.03

120-129

11

20

1.11

2

-

-

1

-

-

130-139

4

25

0.51

0

0

0.00

0

0

0.00

140-149

0

0

0.00

0

0

0.00

1

0

0.00

150-159

1

41

0.21

1

40

0.07

0