Ten Towns Committee
Macroinvertebrate Sampling - 2003
 
The Macroinvertebrate Communities of
the Great Swamp Watershed:
June, 2003:  Results

A Report to the
Ten Towns Great Swamp Management Committee

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

December, 2003

Executive Summary
Increased precipitation through the winter of 2002-2003 and a wet spring were reflected during June, 2003 observations in lower average temperature, TDS, and pH, but in substantially higher turbidity at the Great Swamp watershed stream sites.  Sites displaying highest temperatures (> 20 C in 2003), i.e., BB1, LB2, and GB5, are all immediately downstream from dammed impoundments.  The pattern noted previously of strikingly high values for total dissolved substances (TDS > 470 ppm) at all the Loantaka Brook sites continues in 2003.  Most habitat assessment scores match expected trends of increasing quality along an east to west gradient across the watershed.

A bi-monthly survey of temperature, dissolved oxygen, pH, total dissolved substances (TDS), and a selection of habitat features (regime, embeddedness, cover, and sedimentation) was conducted starting in January, 2003.  Temperatures remain much higher at the two sewage treatment sites (LB3, BB2) during the winter months, leaving these sites with a conspicuously narrower range in temperature overall.  Total dissolved substances were lowest everywhere during March runoff dilution and highest in July.  TDS readings were highest in all of the Loantaka Brook sites in a consistent gradient from upstream highs to downstream lows.   Dissolved oxygen (DO) tended to decline from January into July, but then rise again by September.   This year-round survey revealed a striking variation associated with the immediately post-snowmelt period in March as pH readings at nearly all sites fell from the normal mid-7’s to the 5.0-5.5 unit range.  Almost surely these acidic readings were associated with a pulse of accumulated snowmelt waters, made acid by regional acid deposition.  GB4 showed broad ranges in TDS and depressed dissolved oxygen values from May through November.

Spring and early-summer brought rainfall amounts that finally appear to have relieved the drought conditions that have prevailed for the past couple of years.  With it came improvements in overall species richness in watershed sampling sites, i.e., a total of 132 species observed compared to 99 species in June, 2002.  In only 2 instances, i.e., GB5 and PR2, did macroinvertebrate communities decline even slightly (by 2 points) between June, 2002 and June, 2003.   Five sites, BB1, LB1, LB2, PB1, and PB2, all hosted significantly higher quality communities (by 4 or more B-IBI points) in 2003, likely as a result of a return to more normal (i.e., non-drought) rainfall conditions.  Eight sites, including these five, showed substantially increased total taxa – an average increase of 6.8 species and a high of 16 species at LB2, as compared to 2002.  The alarmingly decline in the macroinvertebrate community at LB2 noted over recent years was reversed in 2003 by a significant increase in community richness (23 species vs. 7 in 2002), with better elements, e.g., caddisfly larvae, replacing stress-tolerant types. 

Strong negative correlation was seen between June B-IBI measures and June estimates of variables such as total dissolved substances (TDS) and temperature, while the correlation with dissolved oxygen was significant and positive.  The bimonthly environmental monitoring was performed in part to see whether community quality, as measured by B-IBI score, was any more strongly correlated with conditions expressed as annual means, maximal values encountered, minimal values encountered, or as the range of conditions experienced rather than simply to the variables measured at the mid-June sampling period.   The negative correlation between macroinvertebrate community scores (B-IBI) and total dissolved substances was strong in all categories.  Likewise, the subjective habitat quality estimates correlated positively and strongly with community quality, especially with June 2003 and with mean and minimal bimonthly estimates.  Average levels of dissolved oxygen, temperature, and turbidity also produced positive correlations.   No correlations was seen with any estimate of pH exposure.  June values showed the highest correlation in 4 of 9 variable comparisons, and they still reflected strong significance for 4 of the remaining 5 variables.  These observations appear to validate our use of single-date June observations to characterize patterns of available environmental conditions.

Graphic comparisons between B-IBI scores and conditions observed in June, 2003 permit us to hypothesize that conditions of total dissolved substances below ca 150 ppm, dissolved oxygen above 9 mg/L, and temperatures below 17 C no longer limit Great Swamp stream communities.  Below these dissolved oxygen or above these TDS or temperature thresholds, community quality appears to be more linearly related.  Especially for the higher quality sites that consistently appear in these beyond-threshold arrays, i.e., PB1, PB2 (DO excepted), PB3, PR2, PR3, IG1, it requires the Habitat Value comparison to reveal their relationships.

Refer to the Stream Summaries section of this report for more details.

The June 2003 Great Swamp Watershed Study: Results
See the Methods and Introduction for a complete description of the 17 sampling sites and methodology (based on the EPA Rapid Bioassessment Protocols (Barbour et al., 1999)) that were used during this survey.
Habitats & Environmental Monitoring
On June 12, 2003, we monitored environmental conditions at all 17 sites between 9 am and 3:30pm.  Refer to Table 03-1 for site-specific values for these variables and Table 03-2 for multi-year comparisons.  Increased precipitation through the winter of 2002-2003 and an unusually wet spring are reflected in lower average temperature, TDS, and pH, but in substantially higher turbidity (and sedimentation buildup noted visually especially at LB1, GB3, PB1, and PR2).  The now familiar pattern of broad ranges in TDS and Habitat Value underscore the continuing cause for concern regarding the impact of human disturbance within the Great Swamp watershed.

Predictably, sites displaying highest temperatures (>20 C in 2003), i.e., BB1, LB2, and GB5, are all immediately downstream from dammed impoundments.  The pattern noted previously of strikingly high values for total dissolved substances (TDS > 470 ppm) at all the Loantaka Brook sites continues in 2003.  It is important to note that values increase upstream, a trend that continues above LB4, the most upstream site in this survey.  (Note:  During winter and spring, 2004, the Great Swamp Watershed Association and the Stream Team have been investigating the patterns and causes of this phenomenon).  Lowest dissolved oxygen values were recorded from the sluggish flow at GB4.  As in the past, no discernable pattern was observed in the stream site distribution of pH or turbidity. 

Most habitat assessment scores match expected trends of increasing quality along an east to west gradient across the watershed.  While variability might be expected in this cumulative, subjective evaluation of habitat conditions, it is interesting to note that lower quality (i.e., eastern) sites have shown greater variability over the years (see Table 03-2 ) than have higher quality (i.e., western) sites.  It makes sense that these measures, emphasizing erosion and sedimentation, vary more in the impacted streams.

A supplemental study of some environmental factors was conducted during 2003.  In the past, environmentally-linked interpretations of macroinvertebrate community quality have been limited to conditions measured during a mid-June set of habitat measures of the sort described to immediately above.  But conditions in June represent only a single set of circumstances to which macroinvertebrates are exposed.  Further, conditions in June are likely to be intermediate within ranges expected to show extremes in mid-winter and mid-summer.  While a single, mid-June survey is useful in comparing the 17 sampling sites to one another on a "typical" day, macroinvertebrates present in June must have endured environmental conditions covering a much broader range during the weeks, months or years preceding.  To gain a better picture of the range and the extremes of conditions experienced annually by organisms at the 17 sampling sites, a bi-monthly survey of temperature, dissolved oxygen, pH, total dissolved substances (TDS), and a selection of habitat features (regime, embeddedness, cover, and sedimentation) has been conducted starting in January, 2003.

Data from this survey appear in Appendix 03-1.  In 2003, the period from January into early March was characterized by an unusual (at least in recent years) amount of snow and conditions cold enough for the snow cover to accumulate over that time.  However, substantial snowmelt immediately preceded the March sampling period.  March data reflect the impact of the unusually strong snow-to-melt pattern experienced in winter 2003.

These data can be used to note several features in annual patterns at the stream sites.  Patterns seen in Primrose Brook and Passaic River sites reflect minimally disturbed environmental responses against which more stressed streams can be compared.  For example, low temperature readings were comparatively much higher at the two sewage treatment sites (LB3, BB2), leaving these sites with a narrower range in temperature overall (Figure 03-1).  Sites below sluggish impoundments (LB2, GB5, PR1) had distinctly higher temperatures from July through September.  Pristine streams show no bimonthly variation in total dissolved substances, although they reflect a slight tendency to accumulate higher concentrations in a downstream direction (Figure 03-2), a trend typical of additive, non-point sources of dissolved substances.  In stressed streams, total dissolved substances were lowest during March runoff dilution and highest in July.  TDS readings were markedly the highest in Loantaka Brook sites in a gradient from upstream highs to downstream lows, a trend consistent with downstream dilution of some upstream point source(s).  Upstream Great Brook sites (GB5 but especially GB4) and Chatham sewage treatment plant site (BB2) had higher than average TDS readings.  Pristine streams show a regular pattern of dissolved oxygen (DO) availability (Figure 03-3), which contrasts with irregularities in more stressed sites.  Dissolved oxygen (DO) tended to decline from January into July, but then rise again by September.  The BB1 site showed a steeper decline in DO into the summer than did other stations.  Turbidity was lowest in January and highest in March runoff.   This variable may be less seasonal and more responsive to local rainfall patterns.  Several sites were very turbid following rains preceding the September survey.

The most striking story among the variables studied was pH, shown in Figure 03-4.  In both early summer and mid-fall samples taken over the past decade, little variation from a pH range of about 7.3 to 8.3 has been noted.  This year-round survey however revealed a marked difference associated with the immediately post-snowmelt period in March as pH readings at nearly all sites fell to the 5.0-5.5 unit range.  Almost surely these acidic readings were associated with a pulse of accumulated snowmelt waters, made acid by regional acid deposition.  At LB2, we observed a strong vertical pH gradient from ca. 7.0 in the surface inch of water to mid-5’s at 6 inches depth.  This marked the contrast between the cold, dense, acidic snowmelt waters overlain by more recent (and perhaps more typical) precipitation that lacked the opportunity to build up such strong acidity.  It is likely that this phenomenon was particularly obvious during this unusually heavy snow year.  Nonetheless, it is clear that macroinvertebrate communities can periodically be inundated by water 100 times more acidic than is typical of their surroundings.  Apparently the impact of this acidic pulse on macroinvertebrates was minimal however.  As will be seen in the next section of this report, most communities in the watershed not only survived this acid rinse but actually improved in quality (in spite of it?).

The range in quality among the five streams draining the Great Swamp watershed is apparent in this bimonthly series of environmental observations.  The overall ranges of conditions that macroinvertebrate communities must endure widen in a pattern paralleling a gradient of increasing human influence (seen in total dissolved substances (Figure 03-2.), dissolved oxygen (Figure 03-3.), and pH (Figure 03-4.)).  Some distinctive conditions appear to be associated with sites such as LB2, GB3, GB5, PB3, and PR1 that occur immediately below impoundments.  Their temperatures are somewhat elevated and their pH values are a bit higher than at nearby sites--both logical consequences of stalling the flow of water in productive circumstances.  However, the most striking variations in pattern occur at sites BB2 (below the Chatham sewage treatment plant), LB3 (below the Morris Township sewage treatment plant).  These treatment plant sites show dramatically elevated cold weather temperatures, generally narrow ranges in pH, elevated levels of total dissolved substances (although the origins of TDS at LB3 apparently lie upstream from the treatment plant), and a comparatively restricted range of dissolved oxygen.   The GB4 site is noteworthy as well.  It occurs in sluggish flow that passes downstream from GB5 (at Foote’s Pond) through a residential area, then roughly paralleling Interstate route 287 amongst a scrubby forested stretch.  This site shows a peculiarly wide range in total dissolved substances and depressed oxygen values from May through November.  Causes of these conditions may be related to potentially significant sources of deicing road salt from both nearby roadways and parking lots.  Very high levels of total dissolved substances have been observed in a detention pond that empties into Great Brook just upstream from GB4 (Karen Patterson, Great Swamp Watershed Association, personal communication).  There are interestingly similar patterns in temperature, TDS, DO, and pH between GB4 and LB4, another site under investigation as possibly impacted by upstream detention pond sources of deicing salt accumulation.

Macroinvertebrate Survey
Spring and early-summer brought rainfall amounts that finally appear to have relieved the drought conditions that have prevailed for the past couple of years.  With it came improvements in overall species richness in watershed sampling sites, i.e., a total of 132 species observed compared to 99 species in June, 2002 (compare Appendix 03-2 to Pollock (2002) Appendix 02-1).  Adjusted Beck Index values for June, 2003 are compared to previous years in Table 03-3.  Individual site B-IBI results from June, 2003 are plotted against Beck Index values in Figure 03-5.  Several of the departures between these indices in which the Beck Index scored communities significantly higher occurred at sites noted above to have conspicuously increased sedimentation this year, i.e., LB1, GB3, PR2.  In fact during the past 4 years, the Beck Index has consistently ranked sediment stress sites such as LB1, GB2, GB3, and GB4 higher than the B-IBI.  The focus of Beck’s Index on organic pollutants appears to be less sensitive to this non-point source of sediment stress, which is more common in the Great Swamp Watershed. 

B-IBI values from June, 2003 are compared to values from 2000 to the present in Figure 03-6.  In only 2 instances, i.e., GB5 and PR2, did macroinvertebrate communities decline even slightly (by 2 points) between June, 2002 (Pollock, 2002) and June, 2003.    Reasons for these and other changes can be identified from among the eight components used to calculate the B-IBI value in Table 03-4.  It may be easier to visualize these specific differences by referring to summary Table 03-5.  Using these three sources of information, significant changes in the watershed’s macroinvertebrate communities will be discussed below.

Because of the composition of the B-IBI, the minimum change in score that can occur is 2 points.  It has been our practice to consider changes of 4 or more points at individual sites as being noteworthy.  By this standard, six sites, BB1, LB1, LB2, PB1, PB2 and PB3, all hosted significantly higher quality communities in 2003, likely as a result of a return to more normal (i.e., non-drought) rainfall conditions.  Eight sites, including these five, showed substantially increased total taxa – an average increase of 6.8 species and a high of 16 species at LB2, as compared to 2002 (Pollock, 2002).  In the highest quality stream, Primrose Brook, and in the lowest quality stream, Black Brook, B-IBI values exceeded scores from 2002. 

The alarmingly steep decline in the macroinvertebrate community at LB2 noted over recent years was reversed in 2003 by a significant increase in community richness (23 species vs.  7 in 2002), with better elements, e.g., caddisfly larvae, replacing stress-tolerant types.  Profuse algal growth, obvious in recent years, was absent in June, 2003, although impoundment related high temperature and the mysteriously high TDS levels remained.  It is likely that heavier rainfall and stream "flushing" helped the macroinvertebrates at this site turn around, elevating it to the "poor" category.  LB1 improved substantially (+4 points) in total taxa, which included fewer stress-tolerant types.  Nonetheless, the increase in runoff related sedimentation at this site was visually obvious.  Conspicuously increased silting was also noted at BB1, GB3, GB5, and PR2 – again, presumably related to increased precipitation and runoff early in 2003.

Both Black Brook sites improved in score but remained in the "very poor" category in 2003.  Better flow through BB1 this June probably influenced its greater species richness and reduced dominance.  The amphipod crustaceans that overran, BB2 in 2002, (93% dominance) were entirely absent in 2003.  Last year, I speculated that these hardy animals may fare better in periods of variable, severe drought conditions, and that the decline at BB2 may well be reversible with a return to more normal weather conditions.  This appears to be the case. 

All 3 Primrose brook sites improved substantially in score, by +4 (PB1,PB3) and +6 (PB2) points.  Increased taxa present at both PB1 and PB2 (e.g., at PB 1, 31 species vs.  21 in 2002) improved dominance factors as well as percent predators.  PB2 also hosted more stoneflies and fewer stress tolerant species.  PB3 also had fewer stress tolerant species and also gained slightly in trichopteran fauna.   Despite modest annual shifts up and down in B-IBI values, Primrose Brook remains overall the highest quality stream in the watershed from the macroinvertebrate standpoint. 

The high-quality upper Passaic River produced scores essentially matching those of June, 2002.  Although its species richness improved (23 species vs.  13 in 2002), PR1 remained low with environmental conditions reflecting the modifying influence of upstream Osbourn Pond (higher temperatures and TDS, lower dissolved oxygen).  Its gradient is particularly low as well.   Limiting conditions at PR2 are associated with sediment loading in this stretch of the Passaic River along with possible influences from an I-287 crossing just upstream.  PR2 slipped slightly but enough in B-IBI score to move to the "poor" category.  The pristine PR3 site maintained its high quality score, although the community appeared to be lower in density than in the past.  Particularly fast-flow water flushing, resulting from increased spring rainfall, could have been responsible.

Combining Habitat Assessment and Biotic Metrics
Correlation Analysis
The results of correlation analysis between biotic metrics and stream site conditions in June, 2003 are found in Table 03-6.  Correlation coefficients (r) display the degree to which changes in the measured level of each habitat variable at the 17 sites study matches biotic metric value calculated on the basis of the macroinvertebrate community found at these locations. 

In Table 03-6, I have used a box and bold type to highlight statistically significant correlations (coefficients > +/- 0.482 at df = 15, p<0.05) between the two biotic indexes calculated here, Beck and B-IBI, and environmental variables monitored on June 11, 2003.  First, it is reassuring that the metrics are highly correlated with one another ( r = 0.934).  But they also both show matching correlations with most other variables.  The measures show high correlation with changes in most of the various habitat assessments, including their Totals and subtotal Habitat Values.   Strong negative correlation is also seen between B-IBI measures and variables such as total dissolved substances (TDS) and temperature, while the correlation with dissolved oxygen is positive.  Perhaps as interesting here is the observation that variations B-IBI values are not correlated with estimates of channel alteration, extent of riparian cover, turbidity, pH, and stream order.  In fact, stream order and pH show little variation among the 17 sites.  Turbidity tends to follow gradients from lower to higher values as one travels downstream and from west to east across the watershed.  However enough local exceptions occur to lower correlation values.  The lack of correlation between riparian cover and all but one variable observed seems odd and appears to underrate its significance to stream water quality and thus to macroinvertebrate organisms.

As described above, bimonthly environmental measures were made at all sites from January through November, 2003.  In part, we wished to see whether community quality, as measured by B-IBI score, was any more strongly correlated with conditions expressed as annual means, maximal values encountered, minimal values encountered, or to the range of conditions experienced rather than simply to the variables measured at the mid-June sampling period. 

Results displaying correlation coefficients relating June B-IBI and maximum, mean, minimum, and range of values from bimonthly environmental observations are found in Appendix 03-3.  These results are summarized in Table 03-7, in which the level of significance between B-IBI values and each bimonthly environmental measure is indicated by ns (not significant), * (p<0.05), ** (p<0.01), or *** (p<0.001).  The negative correlation between macroinvertebrate community scores (B-IBI) and total dissolved substances was strong in all categories, but especially with June 2003 and with maximal and mean bimonthly annual observations.  Likewise, the subjective habitat quality estimates correlated positively and strongly with community quality, especially with June 2003 and with mean and minimal bimonthly estimates.  While these relationships are not necessarily causal, it does seem likely that macroinvertebrate communities within the Great Swamp watershed respond positively to the quality of substrate-habitat available, the degree of sedimentation, and negatively to the concentration of chemicals dissolved in stream waters.  Average levels of dissolved oxygen, temperature, and turbidity also produced positive correlations.   No correlations was seen with any estimate of pH exposure, probably because, with the exception of snow-melt lows mentioned above, pH in all Great Swamp streams falls within a narrow, "normal" 7-8 unit range.  The range of variables faced does not correlate well with community quality.

While June values showed the highest correlation in 4 of 9 variable comparisons, they still reflected strong significance for 4 of the remaining 5 variables.  (Only in the case of highly variable turbidity did June estimates fail to correlate with B-IBI values while annual average values did).  All in all, these observations appear to validate our use of single-date June observations to characterize patterns of available environmental conditions.

Useful patterns underlying correlation values can be seen by plotting variables, such as mean Habitat Values (Jan.- Nov., 2003), against B-IBI values (June, 2003) as in the x-y plot in Figure 03-7.    A linear regression line has been added, along with lines representing +/- 1 standard error of the Y estimates.   The most conspicuous "out-lier" in this relationship is GB3 which has fundamentally good habitat characteristics but hosts an unexpectedly  poor macroinvertebrate community – one still recovering from a major perturbation from the dredging of Silver Lake, just upstream, in 1998-1999 (just as it was in the comparable analysis from last year, Pollock, 2002).  In addition, very poor upstream macroinvertebrate communities do not serve well as potential recruitment sources to restore the GB3 community.

The relationship between June B-IBI values and mean dissolved oxygen for the year is shown in Figure 03-8.  Two distinct patterns emerge here.  Increasing dissolved oxygen from 8.5 gm/L to about 11 mg/L corresponds positively to a gradual increase in community quality (note: trend line in Fig.  03-8 has been visually fitted).  At levels of dissolved oxygen in excess of ca.  11 mg/L, a wide range in community quality is seen.  Beyond a high dissolved threshold (e.g., annual mean > 11 mg/L), increased dissolved oxygen appears to make little difference to community quality.  Presumably factors other than dissolved oxygen are involved in distinguishing among these better quality communities.  Small, sluggish stream sites (LB3, BB1, LB4, GB4) held lowest average levels of dissolved oxygen. 

A similar situation pertains with regard to mean total dissolved substances (Figure 03-9 – trend line visually fit).  In this case, averages greater than ca.  180 ppm TDS help to distinguish among poorer quality sites, but only very modestly given the gradual slope of the trend line.  The spread in B-IBI community quality points is only from 10-16 over a range of TDS values from 150-800 ppm.  The Loantaka Brook TDS problem is clear on this graph, as is the elevated TDS source at GB4.  TDS values less than 150 ppm no longer appear to influence community quality.  In Figure 03-10 (trend line visually fit), average temperatures greater than ca.  11.5 C correlate negatively with community quality.  Temperatures in less than 11.5 C appear to make little difference among higher quality communities.   Sewage treatment plant sites, LB3 and BB2, have highest average temperatures, followed by sites just downstream from impoundments, LB2, GB5, PR1, GB3, and BB1.   Especially for the higher quality sites that appear to be beyond June-threshold limits for dissolved oxygen and total dissolved substances, i.e., PB1, PB2, PB3, PR2, PR3, IG1, it requires the Habitat Value ( Figure 03-7) comparisons to reveal their relationships.   All of these variables appears to correlate at least to some degree with poorer communities, i.e., BB1, BB2, LB1, LB2, LB3, LB4, GB2, GB3, GB4, GB5, and PR1. 

Stream Summaries
For the most part, macroinvertebrate communities reviewed during the 2003 sampling fell into higher (i.e., better) portions of patterns familiar from the previous seasons of study.  Results from both B-IBI and Beck Index analyses (see Table 03-6) agree well with one another (correlation coefficient = 0.938).  The range in environmental conditions and in macroinvertebrate communities continues to be very wide in the Great Swamp watershed, underscoring the challenges before us in improving the stressed streams toward the east side and in preventing the deterioration of those more pristine sites to the west side of the watershed.  A snowy winter followed by a particularly wet spring relieved the drought conditions that have prevailed for the past few years.  The macroinvertebrate community appears to have responded positively to this change.
Indian Grave Brook (B-IBI rating was "good"):
This reference site continued in fine shape producing high B-IBI and Beck values.  Environmental conditions here are close to ideal and this year the site included 44 species (compared to 35 in 2002).
Passaic River (The PR1 & PR2 sites rated "poor"; PR3 rated "good"):
This higher-quality stream produced scores essentially matching those of June, 2002.  Although its species richness improved (23 species vs.  13 in 2002), PR1 remained low with environmental conditions reflecting the modifying influence of upstream Osbourn Pond (higher temperatures and TDS, lower dissolved oxygen).  Its gradient is particularly low as well.   Fair conditions at PR2 are associated with sediment loading in this stretch of the Passaic River along with possible influences from an I-287 crossing just upstream.  The pristine PR3 site maintained its high quality score, although the community appeared to be lower in density than in the past.  Particularly fast-flow water flushing could have been responsible.
Primrose Brook (PB1 scored "fair"; PB2 & PB3 scored in the "good" category):
PB3 bettered further its improved score noted in June, 2002.  Both PB1 and especially PB2 improved substantially in score.  Despite modest annual shifts up and down in B-IBI values, Primrose Brook remains overall the highest quality stream in the watershed from the macroinvertebrate standpoint. 
Great Brook (GB3 & GB4 remained in the "very poor" range; GB2 & GB5 were "poor"):
GB5 showed marked improvement in 2002 but slipped somewhat in 2003.  It probably reflects the changeable influence of an impoundment just above it.  It showed visual evidence of increased sedimentation, undoubtedly related to recent rains.  GB5 consistently shows the highest temperature of all sites.  Higher species numbers (20 species vs.  10 in 2002), especially including caddisfly larvae, led GB4 to a substantial score improvement, although its sluggish flow and possible impact from a nearby detention pond continues to leave it lowest in dissolved oxygen level but high in total dissolved substances.   GB2 improved slightly in score over 2002 by adding stress-intolerant mayflies while some stress-tolerant types declined. 
Loantaka Brook (LB1, LB3, & LB4 were "very poor"; LB2 was "poor")
Overwhelming dominance (93%) by enchytraid worms helped bring LB3 score down.  Significantly increased sedimentation was obvious at "very poor" LB1, although a modest increase in total taxa, including fewer stress-tolerant types, brought the site a 4 point B-IBI improvement.  The alarmingly steep decline in the macroinvertebrate community at LB2 noted over recent years was reversed in 2003 by a significant increase in community richness (23 species vs.  7 in 2002), with better elements, e.g., caddisfly larvae, replacing stress-tolerant types.  Profuse algal growth, obvious there in recent years, was absent in June, 2003, although empoundment related high temperature and the consistently high TDS levels remained.  It is likely that heavier rainfall and stream "flushing" helped the macroinvertebrates at this site turn around.    Upstream sites, LB3 & LB4, remained constant relative to 2002 scores.  Severely limited habitat quality make dramatic improvements in macroinvertebrate communities unlikely at these two locations.
Black Brook ("poor" overall B-IBI rating):
Both Black Brook sites improved in score, but remained in the "very poor" category in 2003.  Better flow through BB1 this June probably influenced its greater species richness and reduced dominance.  The amphipod crustaceans that overran, BB2 in 2002, (93% dominance) were entirely absent in 2003.  Last year, I speculated that these hardy animals may fare better in periods of variable, severe drought conditions, and that the decline at BB2 may well be reversible with a return to more normal weather conditions.  This appears to be the case. 
The June 2003 Great Swamp Watershed Study:  Recommendations
  1. Monitoring of these 17 sampling sites should be continued.  The longer the run of data regarding these key locations throughout the watershed, the more clearly we will be able to discern the difference between "normal" variations and those indicating significant change.  I will submit a proposal for the extension of this monitoring program to the Ten Towns Great Swamp Watershed Management Committee.
  2. In addition to perennial "troublesome" sites just below sewage treatment plants (BB2, LB3) or impoundments (LB2, GB3, GB5, PR1), the possible connection between unusually high total dissolved substances and low mid-year oxygen readings at site GB4 and a nearby detention basin warrant further investigation. 
  3. Following a snowy winter and rainy spring this year, visually conspicuous sediment buildup was observed at LB1, GB3, PB1, and PR2.  Comparatively rich sources of sediments from watershed and/or stream bank erosion must be evident upstream from these sites and controlling them in some way would certainly be beneficial.
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.

Pollock, L.W.  2000.  The Macroinvertebrate Communities of the Great Swamp Watershed.  A Report to the Ten Towns Great Swamp Management Committee.  General Introduction and Methods: 2000 and Subsequent.  12 pp., Tables & Figures.

Pollock, L.W.  2002.  The Macroinvertebrate Communities of the Great Swamp Watershed, June, 2002: Results.  A Report to the Ten Towns Great Swamp Management Committee.  11 pp, 6 Tables, 6 Figures.

SCS Water Quality Indicators Guide: Surface Waters.

Acknowledgments
I wish to express my appreciation for the Ten Towns Great Swamp Watershed Management Committee's understanding of the value of using macroinvertebrate communities to document water quality conditions throughout the watershed.   In particular, I am grateful for their funding of this 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 Lauren DeStefano, my Drew student assistant during this project, for being such a careful worker and such good company during this sampling season.  And finally, my thanks goes to Mr.  Gene Fox who volunteered his valuable help during portions of the field sampling in June, and especially during many of the (sometimes unpleasantly cold) bimonthly environmental monitoring sessions.
Figures
Figure 03-1.  Annual patterns of temperature change measured bimonthly at sampling sites during 2003.

Figure 03-2.  Annual patterns of change in Total Dissolved Substances (TDS) measured bimonthly at sampling sites during 2003.

Figure 03-3.  Annual patterns of change in dissolved oxygen measured bimonthly at sampling sites during 2003.

Figure 03-4.  Annual patterns of change in pH measured bimonthly at sampling sites during 2003.

Figure 03-5.  Comparison of Beck Index and B-IBI values for 17 sampling sites within the Great Swamp watershed, June, 2003.  Descriptive terms and limits shown refer to B-IBI values. 

Figure 03-6.  B-IBI values for 17 sampling sites within the Great Swamp watershed, June, 2000 through June, 2003.  

Figure 03-7.  Composite "Habitat Values" are plotted against B-IBI value for each of the 17 sampling sites based on mean values taken in bimonthly sampling in 2003.  A regression line and lines representing +/- 1 standard error of the Y estimates are also shown.

Figure 03-8.  Mean values for dissolved oxygen value for each site are plotted against B-IBI values based on bimonthly sampling in 2003.   The dotted vertical line approximates apparent threshold values of dissolved oxygen.  A trend line for remaining points has been added by estimation.  See text for further explanation. 

Figure 03-9.  Mean values for total dissolved substances values for each site are plotted against B-IBI values based on bimonthly sampling in 2003.  The dotted line approximates apparent threshold values of total dissolved substances.  A trend line for remaining points has been added by estimation.  See text for further explanation. 

Figure 03-10.  Mean temperature values for each site are plotted against B-IBI values based on bimonthly sampling in 2003.  The dotted line approximates apparent threshold values of temperature.  A trend line for remaining points has been added by estimation.  See text for further explanation. 

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Macroinvertebrate Sampling Study - 2003