Ten Towns Committee
Macroinvertebrate Sampling - 2000
 
The Macroinvertebrate Communities of
the Great Swamp Watershed:
Summer, 2000:  Results

A Report to the
Ten Towns Great Swamp Management Committee

Leland W. Pollock, Ph.D.
Department of Biology
Drew University

October, 2000

Executive Summary, 2000
We have made a transition from the original survey procedures to those currently employed.  This year's survey should provide a new reference base for subsequent surveys.  Stressed sites are generally matched by more extreme environmental parameters.  However, in many cases, the range in conditions observed is surprisingly narrow.

A total of 3512 individuals including 122 distinct entities (either species or genera) were identified among the 17 sites in this survey.  Encouragingly, in all but 4 cases, summer 2000 data showed modest to considerable improvement.  For reasons that are not clear, the site closest to the Refuge boundary on Loantaka Brook, LB1, showed decline in the 1999-2000 period.  High turbidity found there may indicate stress from sedimentation.  The decline at GB4 was slight.  In Great Brook, the sites below the recent Silver Lake dredging and dam restoration project, i.e., GB3 and GB2, showed encouraging recovery between fall, 1999 and June, 2000.  All the Passaic River locations showed modest improvement in B-IBI community score.  The Primrose Brook location (PB1) immediately downstream from the recent Blue Mill Road bridge replacement project was understandably impacted by this activity.  Meanwhile the upper Primrose Brook sites, PB2 and PB3, showed strong recovery from a significant silting accident associated with the dredging of an upstream pond.

Finally, on the basis of my several years observing the five streams within the Watershed, I prepared first rough draft of what appears to me to be the most likely sources of environmental stress at each stream site.  Higher total dissolved solids (TDS) levels characterize upper Loantaka Brook sites, while LB1, GB5, and GB3 experience comparatively high turbidity.  LB3 (below the Morris Township sewage treatment plant), LB4 (next to the Township's swimming pool), and BB2 (next to Chatham Township's sewage treatment plant) appear to be the sites experiencing greatest stress.

All in all our stream communities reflect considerable improvement over their condition during the stressful 1999 drought period.  Our more pristine areas, including Indian Grave Brook, Primrose Brook, and the upper Passaic River, are at all-time highs, for the most part.  Compared to more stressed streams, such as Black Brook, Loantaka Brook, and much of Great Brook, these stream sites tend be wider, with greater riffle zone frequency, higher in dissolved oxygen, the variety of habitat options, and the extent and condition of the riparian zone, but lower in total dissolved substances and turbidity

The June 2002 Great Swamp Watershed Study: Results
An general introduction and descriptions of methods used in this survey are available elsewhere at this site.
Habitats & Environmental Monitoring
Environmental variables recorded during our survey of June 20, 2000 are displayed in Table 00-1. Combinations of physico-chemical conditions array the 17 sampling sites studied here along an environmental quality gradient.  Stressed sites are generally matched by more extreme environmental parameters.  However, in many cases, the range in conditions observed is surprisingly narrow.  Temperatures showed a mean of 20.98 C and a range of only 18.8 C to 24.1 C (at GB5, just below a slow-flowing, exposed impoundment, Foote's Pond).  Dissolved oxygen is often a key variable for macroinvertebrates.  But in Great Swamp streams, a range of 6.79 mg/L (at relatively sluggish, warm GB4) to 9.7 mg/L (at PB3, cool waters just below a shallow impoundment) surrounded a mean of 8.31 mg/L.  All levels considered to be well above stressful for most organisms.  The variation in pH was also modest, 7.28 units (at LB3, downstream from a sewage treatment plant) to 8.68 units (at GB5, probably reflecting the eutrophic productivity in the impoundment immediately upstream).  Larger variations were observed in Total Dissolved Substances (TDS) and turbidity.  TDS ranged from 93.2 units (at relatively clean PB3) to 790 units (at LB4 in a channelized reach next to the Morris Township swimming pool).  Mean TDS of 341.8 units separated our most stressed streams (Black Brook, Loantaka Brook, and upper Great Brook, all above the mean) from the remainder which are less stressed.  Turbidity was lowest, 0.62 FTU, at the PR2 site, perhaps surprisingly from its location just downstream to I-287.  On the other hand, current speeds at PR2 tend to favor sandier deposits rather than fine, suspendable silt.  Turbidity was highest, 10.6 FTU, at stressed LB1 (only slightly above 10.43 FTU at BB2, just below the Chatham Township sewage treatment plant).  Again, the mean of 4.86 FTU separates the more stressed sites (higher) from those less stressed, with the interesting exceptions of LB3, just below the Morris Township sewage treatment plant, with 2.98 FTU much lower than LB4 or LB2; and PR1, at oddly high 6.47 FTU, probably related to its position just below Osbourne Pond.
Macroinvertebrate Survey
A total of 3512 individuals including 122 distinct entities (either species or genera) were identified among the 17 sites in this survey.  Appendix 00-1 lists the count data.

Figure 00-1 shows family-level Beck Index values derived from parallel surveys conducted at 5 stream sites during the June, 1999 by the NRCS team using their standard techniques and by me ("LWP" in Fig. 00-1) using techniques described above.  While my techniques made little difference in the most stressed locality where comparatively few macroinvertebrate types occur (BB1), the differences were more significant in the other settings, LB1, GB2, PB1, and PR1.  Similar patterns can be seen in Figure 00-2 in which June, 1999 Beck Index data (from NRCS) are compared to June, 2000 Beck Index data from this study.  Higher Beck Index values in 2000 at LB2 and GB4 probably in part reflect adjustments in those sample site locations made to find more comparable substrates or to avoid proximity to an obvious disturbance.  But the substantial differences in Beck values found in Passaic River and Primrose Brook sites probably reflect a more thorough characterization of the communities present at those species-rich locales rather than any substantive improvement or change in actual field conditions between 1999 and 2000.  The Indian Grave Brook (IG1) site was newly added during this study. 

Based on differences observed here compared to past results (1992-1999 surveys), a correction factor has been applied to adjust Beck values in the current survey to accommodate the impact of changes in observation techniques.  Such results can be seen in summary Table 00-2.

As their 1999 report to the Ten Towns Committee notes (NRCS, 1999), the NRCS monitoring team indicated that the Beck Index values at many sites were lower in 1999 than in 1998, and are, in fact, near the bottom of all previous measures.  (We observed similar results comparing fall survey data gathered by Drew students in 1999 to those of previous years.  Community scores were at or near minimal values in fall, 1999 as well).  NRCS researchers attributed this to unusual drought conditions preceding and during their observation period.  The dramatic 1999 rise in Beck Index at the GB3 site is difficult to understand since that site has been heavily impacted by the recent dredging/dam repair project at Silver Lake immediately upstream.

A comparison between Beck Index and the new B-IBI values for June 2000 data is shown in Figure 00-3.  The fact that the patterns of the two metrics are quite similar suggests that the Beck Index used in the past works quite well to characterize the Great Swamp streams, even if absolute values for less stressed communities may have been underestimated in the past.  Because the B-IBI is based on more ecologically sound and locally tailored characteristics, it represents a more convincing metric for use in subsequent comparisons. 

Encouragingly, in all but 4 cases, summer 2000 data showed modest to considerable improvement.  (Note: sites BB2, LB3, GB4, and IG1 were not included in Oct., 1999 studies).  Using B-IBI data in Figure 00-4, only 2 locations showed no change in the 1999-2000 period, while only two others declined in quality.  For reasons that are not clear, the site closest to the Refuge boundary on Loantaka Brook, LB1, showed decline in the 1999-2000 period.  High turbidity found there may indicate stress from sedimentation.  The decline at GB4 was slight.  In Great Brook, the sites below the recent Silver Lake dredging and dam restoration project, i.e., GB3 and GB2, showed encouraging recovery between fall, 1999 and June, 2000. At least some of the mussel population at the GB2 site appear to have survived this disturbance.  All the Passaic River locations showed modest improvement in B-IBI community score.  The Primrose Brook location (PB1) immediately downstream from the recent Blue Mill Road bridge replacement project was understandably impacted by this activity.  Recovery of this normally rich community will be interesting to monitor.  Meanwhile the upper Primrose Brook sites, PB2 and PB3, showed strong recovery from a significant silting accident associated with the dredging of an upstream pond.

Combining Habitat Assessment and Community Analysis
The environmental correlates of these groups of sites were explored using the multi-variate statistical technique, canonical correspondence analysis (CCA).  In this procedure, site data for species (i.e., Appendix 00-1) is entered as the main file and site environmental data (i.e., Table 00-1) is entered as the secondary file.  A full explanation of this procedure can be found in the works of Ter Braak (1986, 1987).  A detailed accounting here surpasses our need.  The resulting 2-dimensional plot arrays all species in best-fit positions relative to the environmental variables present.  Then positions of all species included in a particular sampling site form a site-specific "constellation" of points within the graph space, and a symbol for each site is located at the centroid of its particular species cluster.  This places all of the sample sites in relative position to the major environmental gradients as well.

The results of canonical correspondence analysis are shown in Figures 00-5 and 00-6.  Figure 00-5 shows the relationship of species observed to important environmental gradients, including dissolved oxygen, total dissolved substances (TDS), temperature, turbidity, and pH.  Note that in several instances groups of species occurred at virtually the same spot.  To make the graph more readable, in those cases, the term "group" followed by a group number is shown on the graph, and its constituent members are listed to the lower left.  This figure can help to determine which species make useful indicators of particular environmental conditions.  Look in the direction of arrow heads representing increasing values or arrow tails showing decreasing values for particular variables.  Species found toward those extremes are best choices as indicators.  Note that frequently species beginning with "Dip" (standing for Order Diptera, Family Chironomidae) occur there, with different "Dip" species near each arrow head and tail.  This demonstrates the potential value of including species-level detail for this difficult group.

Figure 00-6 indicates the placement stream sites within the gradients of environmental factors.  Despite modest absolute ranges in dissolved oxygen and temperature, both species and site distributions are scattered most strongly along these gradients (top right to lower left).  This includes the more pristine sites (IG1, PR3, PB3, PB2) which are found toward the upper right.  Higher total dissolved solids (TDS) levels (toward the upper left) characterize upper Loantaka Brook sites, while the position of LB1, GB5, and GB3 reflects higher turbidity at those sites.  , while more stressed sites appear toward the periphery of several environmental gradient arrows suggesting more stressed conditions - Higher pH, Higher Turbidity (GB5, LB1); Lower Dissolved Oxygen, Higher Temperatures (BG5, BB2, LB4); Higher TDS (LB3).  LB3 (below the Morris Township sewage treatment plant), LB4 (next to the Township's swimming pool), and BB2 (next to Chatham Township's sewage treatment plant) appear to be the sites located farthest along the lines of increasing stress.  The position of BB1 in this figure is something of a mystery in that it appears in the higher quality quadrant of the diagram and yet is obvious as a site under considerable stress.

Finally, on the basis of my several years observing the five streams within the Watershed, I prepared first rough draft of what appears to me to be the most likely sources of environmental stress at each stream site.  In Table 00-3, I listed 6 most likely sources of stress for our region and indicated for each site the relative likelihood of significant impact from that source (++ high likelihood, + likelihood, 0 average or mild impact, - unlikely to be a significant source of stress).  These are subjective speculations, based on observations but not on direct, quantitative assessments.  In several cases, the most likely, but again speculative, source of the problem is assigned.  For each site, the sum of all "+"s was calculated.  This analysis reinforces the idea that Black Brook and the upper portion of Loantaka Brook face the strongest and most varied sources of stress, and Indian Grave, Primrose, and upper parts of the Passaic Rivers suffer least.  Clearly however I must e missing some important stress(es) impacting the LB1 location.

Stream Summaries
All in all our stream communities reflect considerable improvement over their condition during the stressful 1999 drought period.  Our more pristine areas, including Indian Grave Brook, Primrose Brook, and the upper Passaic River, are at all-time highs, for the most part.  Compared to more stressed streams, such as Black Brook, Loantaka Brook, and much of Great Brook, these stream sites tend be wider, with greater riffle zone frequency, higher in dissolved oxygen, the variety of habitat options, and the extent and condition of the riparian zone, but lower in total dissolved substances and turbidity.
Indian Grave Brook (IG1 ranked "Good" in B-IBI score)
As a new site in this survey, Indian Grave Brook serves as a "reference" stream, hosting the highest quality biological community in the area.
Passaic River (PR1 ranked "poor", PR3 ranked "fair", and PR3 was "good")
Our PR3 site in the upper Passaic River provides a lovely example of clean-water macroinvertebrate community structure.  However, the lower Passaic River sites appear to struggle from obvious sources of temperature, channelization, and sedimentation stress, probably in association with I-287 at PR2 and with Osbourne Pond just above PR1.
Primrose Brook (PB1 was "poor" in B-IBI score; PB2 & PB3 were both "good")
The upper Primrose Brook sites that appear to have recovered from the severe silting incident they suffered in 1997, although PB1 has dropped some in quality coincident with the summer, 2000 Blue Mill Road bridge replacement project immediately above this site.  While this comparatively pristine stream appears to be quite resilient to insult, it is worth noting that we have challenged all three of its sampling sites strongly with siltation stress during the past 5 years.

More disturbing is the fact that some of our already embattled localities appear to be losing ground, with BB1, LB1, LB4, the lower (swampward) half of Great Brook, and I287-impacted PR2 at or near the lower end of their 6 year range.

Great Brook (GB2 & GB3 were "poor" while upstream GB4 & GB5 were "very poor")
Lower Great Brook either is (GB2) or hopefully is about to begin (GB3) recovering from sedimentation resulting from the recent Silver Lake dredging project.  But all of Great Brook in general appears to suffer from excessive sedimentation and poor riparian protection, and high total dissolved substances mark upper Great Brook sites as well.
Loantaka Brook (LB1, LB3 & LB4 were all "very poor" ; LB2 was "fair"):
Loantaka Brook 4 and 2 may be edging upward, although high sediments, turbidity, and total dissolved substances, and a lack of riffle habitat appear to limit recovery prospects there.  The biotic community in the lower Loantaka Brook area (LB1) suggests that conditions are not good there, although it is not clear which environmental variables are primarily responsible.
Black Brook (BB1 was "poor", while BB2 was "very poor")
Characterization of this stream has been limited to small, slow moving, channelized tributaries in this and previous surveys.  Variable water levels, high total dissolved substances and turbidity, and poor macroinvertebrate habitat availability stress these communities.  Most of the more substantial flow of Black Brook lies within the Refuge itself and thus is beyond the boundaries for this survey.  While its several tributaries eventually coalesce into a substantial stream, its generally low gradient results in slow velocity and a silty bottom in which riffle habitat is not found.
The June 2000 Great Swamp Watershed Study:  Recommendations
  1. The continuity of data regarding macroinvertebrate communities in Great Swamp streams is valuable and should be continued.
  2. The eastern-most three streams, Great Brook, Loantaka Brook, and Black Brook, are clearly the most stressed.  Identifying sources of their stress and a reducing them where possible should be a priority.
Literature Cited

Barbour, M.T., J.Gerritsen, B.D.Snyder, and J.B.Stribling.  1999.  Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates and Fish, Second Edition.  (EPA 841-B-99-002).  U.S.  Environmental Protection Agency; Office of Water; Washington, D.C.

Karr, J.R.  and E.W. Chu.  1999.  Restoring Life in Running Waters: Better Biological Monitoring.  Island Press, Washington, 206 pp.

NRCS.  1999.  1999 Water Quality Inventory: Macroinvertebrates of the Great Swamp Tributaries.  USDA Natural Resources Conservation Service, Somerset, NJ. 13 pp.

Ter Braak, C.J.F.  1986.  Canonical correspondence analysis: a new eigenvector technique for multivariate direct gradient analysis.  Ecology, 67:1167-1179.

Ter Braak, C.J.F.  1987.  The analysis of vegetation-environment relationships by canonical correspondence analysis.  Vegetation, 69:69-77.

Acknowledgments
I wish to express my appreciation of the Ten Towns Great Swamp Watershed Management Committee's understanding of the value of maintaining this on-going data base that uses macroinvertebrate communities to document water quality conditions throughout the watershed.  In particularm, I am grateful for their funding of this particular study.  In addition I acknowledge the generous, in-kind support of my home institution, Drew University, and faculty colleagues who have provided encouragement as well as the equipment and facilities necessary to the project's completion.  And finally, I am especially indebted to Kristine Joppe-Mercure, my indefatigible Drew student assistant during this project, for being such a capable "quick study" in adopting the techniques used here.
All Figures.     All Tables.     Appendix.
 
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Macroinvertebrate Sampling Study - 2000 - Revised