J. N. Am. Benthol. Soc., 2001, 20(3):432–447
q 2001 by The North American Benthological Society
Trophic basis of invertebrate production in 2 streams at the
Hubbard Brook Experimental Forest
ROBERT O. HALL, JR.1, GENE E. LIKENS,
AND
HEATHER M. MALCOM
Institute of Ecosystem Studies, Box AB, Millbrook, New York 12545 USA
Abstract. Many forest stream food webs have leaf litter as the primary food resource, but instream
primary production can also be quantitatively important, in part because it is more easily assimilated.
We estimated the trophic basis of invertebrate production in 2 streams at Hubbard Brook Experimental Forest: Bear Brook (BB), a 2nd-order closed canopy stream, and Main Hubbard Brook (HB),
a 5th-order open-canopy stream. We combined secondary production measurements for 1 y with gut
content analyses to estimate the fraction of total secondary production derived from various food
sources. Secondary production was low in both streams: 4.2 g ash-free dry mass (AFDM) m22 y21 in
BB and 3.0 g AFDM m22 y21 in HB. The amount of primary consumer secondary production derived
from algae was 5% in BB and 28% in HB, with the remainder derived from organic detritus. Higher
algal availability and lower benthic organic matter storage resulted in a higher fraction of algal
consumption in HB relative to BB. Predators consumed ;72 to 92% of total secondary production,
producing high predatory losses of insect production. Algal production was not a large food source
in either stream because of low availability, possibly caused by shading in BB and possibly nutrient
limitation in both streams.
Key words: secondary production, food webs, algae, detritus, organic matter flow, macroinvertebrates, Hubbard Brook Experimental Forest.
Aquatic ecosystems, and especially forest
streams, are often heavily subsidized by allochthonous C inputs (e.g., Likens 1972, Fisher
and Likens 1973, Hynes 1975, Polis et al. 1997,
Wallace et al. 1997b). This C can be a major energy source to the stream, and has been shown
experimentally to regulate secondary production (Wallace et al. 1997b, 1999) and foodweb
structure (Hall et al. 2000). However, allochthonous C is not the only C source in a stream; autochthonous algal production can also be important in streams, especially ones with open
canopies (Minshall 1978, Hill and Harvey 1990,
Lamberti 1996). Many studies have examined
relative C inputs to streams using annual C
budgets (Fisher and Likens 1973, Webster and
Meyer 1997). Few, however, have examined the
inputs of C relative to the food base of the
stream (Rosenfeld and Mackay 1987).
Carbon budgets and measures of metabolism
may not adequately represent use of C by animals in stream food webs. Leaf material is recalcitrant to consumers relative to algae; hence,
algal C might be more important to animals
than predicted by its inputs. However, it is much
more difficult to measure C use by a food web
1
Present address: Department of Zoology and
Physiology, University of Wyoming, Laramie, Wyoming 82071 USA. E-mail: [email protected]
compared with metabolism or C budgets for a
stream. To do so requires estimates of food consumption by the dominant invertebrates in the
food web at a time scale of ;1 y. This requirement means that secondary production of the
invertebrate assemblage must be measured as
well as the fraction of this production derived
from allochthonous vs autochthonous C. This
distinction cannot be made from assignments of
functional feeding groups because these groups
may not represent what an animal actually is
eating (Mihuc 1997). Instead we must directly
examine food in animal guts or else use an isotopic tracer approach. Each approach has its pitfalls; gut contents may not accurately represent
assimilation and gut contents may be difficult
to classify. Estimates from C isotopes are possible only if a distinct separation between allochthonous and autochthonous 13C ratios exists in
nature and is maintained through time.
Bear Brook (BB) in Hubbard Brook Experimental Forest (HBEF) is a classic example of a
stream dominated by inputs of allochthonous C;
Fisher and Likens (1973) considered algal production to be nil in this stream, with nearly all
energy flow being driven by allochthonous inputs. Subsequently, Mayer and Likens (1987)
showed that algae were quantitatively important in the diet of the caddisfly Neophylax, sug-
432
2001]
TROPHIC
BASIS OF INVERTEBRATE PRODUCTION
gesting that the assumption of negligible algal
production in BB may not be true or may have
changed with time. However, the importance of
algae to one algivorous insect is not indicative
of the stream food web as a whole. In our study,
we estimated relative use of algal and detrital
organic matter for all of the energetically important members of the stream food web, using
the trophic basis of production method (Benke
and Wallace 1980, 1997) to estimate flow of allochthonous and autochthonous organic matter
to consumers. We performed this analysis in 2
sites to maximize differences in possible algae
use; the 1st site was BB to compare with Fisher
and Likens (1973) and Mayer and Likens (1987).
The 2nd site was Main Hubbard Brook (HB)
(use of ‘‘Main’’ distinguishes the stream from
the experimental forest as a whole), which is an
open-canopy stream where we expected algae
production to be much more important to the
stream food web than in BB. In addition, we
addressed the control of secondary production
in each of these streams by examining standing
stocks of detrital and algal food resources.
Study Sites
The HBEF is in the White Mountains of New
Hampshire, USA (lat 43856‘N, long 75845‘W),
and has a cool, continental climate with ;⅓ of
annual precipitation occurring as snow. The basin is forested primarily by American beech (Fagus grandifolia), sugar maple (Acer saccharum),
and yellow birch (Betula alleghaniensis).
Bear Brook is a 2nd-order forest stream that
has been used for many other stream studies at
HBEF (e.g., Fisher and Likens 1973, Meyer and
Likens 1979, Mayer and Likens 1987). It is heavily shaded in the summer, open during spring
and late autumn, and bridged with a deep snow
pack in winter. We sampled a 400-m reach immediately downstream of the main road (near
Fisher and Likens 1973 site 6). This section has
a complete forest canopy and the baseflow wetted stream width was ;2.7 m. Baseflow discharge was ;5 to 10 L/s. The study reach consisted of step pools with substratum sizes ranging from gravel to boulder. There were only a
few large organic debris dams in this reach relative to undisturbed, small, 1st-order watersheds at HBEF.
Main Hubbard Brook is a 5th-order stream
that is the main drainage for the valley, and has
433
received relatively little study at HBEF. This
stream is much wider (10.2 m) than BB, and
thus receives more sunlight during summer.
Like BB, this stream is bridged with a snow
pack during winter. We sampled in a 200-m
reach immediately upstream from where the
main road crosses the stream. Substratum was
relatively uniform cobbles and boulders, and
was primarily riffle habitat. There were no organic debris dams. Baseflow discharge was ;50
to 100 L/s.
Methods
Secondary production
We sampled invertebrates approximately
monthly from 6 December 1996 to 25 November
1997. We did not sample during January or February because of a heavy snow pack. In early
March, there were a few openings in the snow
pack to allow sampling. We collected 4 samples
from riffle–pool (cobble and gravel substratum)
habitats in BB using a Hess sampler with 250mm mesh net. Within boulder–cascade habitats
that prohibited Hess sampling, we scraped a
measured area of substratum into a 0.5-m wide
zooplankton net (150-mm mesh) pressed to the
rock surface. Three of these samples were collected at each sampling date. The approximate
ratio of riffle–pool area relative to boulder–cascade area was 4:3 based on measurements prior
to sampling; hence, we simply averaged invertebrate numbers in Hess and cascade samples to
estimate invertebrate abundance. We collected 6
samples from HB on each date. Because HB had
a uniform cobble substratum we only used the
Hess sampler. Because of blizzard conditions
during March sampling we collected only Hess
samples from BB.
Samples were preserved in 95% ethanol,
stained with rose bengal, and separated into a
.1-mm size fraction and a 250-mm to 1-mm
size fraction for sorting. All invertebrates were
picked from the .1-mm size fraction, whereas
we subsampled the 250-mm to 1-mm size fraction prior to sorting with a stereomicroscope.
Samples were evenly distributed on a 250-mm
sieve and a fraction (⅛ to ½) of this material was
removed for sorting and counting. Most insects
were identified to genus. Chironomids were
identified as tanypodine (predator) or non-tanypodine (collector-gatherer). Non-insect inver-
434
R. O. HALL
tebrates were identified to order or higher.
Lengths of all animals were measured to the
nearest mm and converted to biomass using
length–mass regressions from Benke et al.
(1999).
We estimated secondary production for common taxa using the size-frequency method corrected for cohort production interval (CPI) (Benke 1984). In BB, this method was applied to 56%
of taxa, which accounted for 98% of total production; in HB, this method was applied to 60%
of taxa (96% of total production). The CPIs were
estimated by examining size distributions of invertebrates through the 1-y sampling period
and by examining emergence patterns found by
Fiance (1979) and K. H. Macneale (Cornell University, personal communication). For rare taxa,
we multiplied biomass by an assumed P/B ratio
of 5 (for univoltine taxa that composed most of
rare taxa) or 2.5 (for some rare semivoltine taxa
with life cycles .1 y) (Waters 1977). For taxa
with unknown life-cycle lengths (e.g., oligochaetes), we multiplied biomass by a P/B ratio
of 5. Errors from calculating production for rare
taxa by using this method should be small because we only used it for 2% of production in
BB and 4% of production in HB. Non-tanypodine chironomid production was estimated using the assemblage-level instantaneous growth
method, and correcting for larval size and water
temperature (Huryn 1990). We used regression
equations in Huryn (1990) to estimate growth
rates, which were multiplied by monthly chironomid biomass. This method was developed
originally for forested streams in North Carolina, and may not be suitable for HBEF. However,
for our paper, we assumed these equations were
valid because they were developed for chironomid assemblages that spanned a range of species, and because type and quality of food are
similar between HBEF and Coweeta streams.
Water temperature was measured with a mercury thermometer approximately weekly in BB
and monthly in HB.
Trophic basis of production estimates
We used 2 approaches to assess the resource
base of the stream food webs. We used diet
analyses to estimate consumption of various
food sources and we measured standing stocks
of algae and leaf litter to examine food availability. We attempted to use variation in natural
ET AL.
[Volume 20
abundance of 13C (McCutchan 1999), but this approach failed in these streams (see Results). We
collected filamentous algae and abscised leaves
for isotope analysis. We sampled filamentous algae because they represent relatively pure algal
C; epilithon may contain substantial terrestrial
detritus. We collected filamentous algae by
scraping rocks from HB 3 times during 1997: 12
June, 31 July, and 27 September. We collected filamentous algae in BB only on 12 June because
they were not found at other times. We collected
leaves in litter traps during autumn because leaf
detritus collected from streams is often colonized by algae (Mayer and Likens 1987). Algal
and leaf material were dried at 508C, ground,
and analyzed for 13C/12C and 15N/14N by combusting samples in an elemental analyzer connected to a continuous-flow mass spectrometer
at Cornell Laboratory for Stable Isotope Analysis, Ithaca, New York. Standard deviation for
replicate measurements was ,0.1‰.
We analyzed gut contents of common taxa
(those .1% of total invertebrate production)
from each stream during 3 seasons, spring
(March–May), summer (June–Sept.), and autumn (Oct.–Dec.). We dissected guts of 1 to 4
individual animals, suspended the contents in
distilled water, filtered the contents onto a
membrane filter, placed them onto a microscope
slide, and cleared them with immersion oil. We
made 3 to 4 slides for each common detritivore/
herbivore taxon in each season. We quantified
gut contents by measuring the relative areas of
7 diet categories on the filters (Cummins 1973)
using a compound microscope at 4003
equipped with a video image analyzer (amorphous detritus, leaf detritus, wood detritus, diatoms, filamentous algae, fungal hyphae, and
animal material). We did not examine gut contents of predators, but assumed that they ate exclusively animal prey (Hall et al. 2000). However, omnivorous caddisflies (e.g., hydropsychids, some shredders) can eat animals and detritus, so we quantified gut contents of
hydropsychids.
We used the trophic basis of production method (Benke and Wallace 1980, 1997, Hall et al.
2000) to estimate both the fraction of invertebrate production derived from these various
food sources and to calculate organic matter
flows. We calculated the fraction of invertebrate
production derived from food type i (Bi) by dividing the fraction of area in the gut by the as-
2001]
TROPHIC
BASIS OF INVERTEBRATE PRODUCTION
435
FIG. 1. Mean (61 SE, n 5 3) d13C and d15N values of leaf litter and filamentous algae from Main Hubbard
Brook (HB) and Bear Brook (BB). Hollow points labeled with dates are for 3 different filamentous algae collections in HB; solid points are other materials that were collected on one date.
similation efficiency for that food type, and dividing again by the areal sum of all food types
in the gut. Using secondary production of the
taxa and Bi, we calculated organic matter flow
from each food type i to consumer j (Fij in mg
ash-free dry mass [AFDM] m22 y–1) as:
Fij 5 (Bi Pj)/(AEi NPE)
where Pj is production of consumer j in mg
AFDM m22 y21, AEi is assimilation efficiency of
consumer j for food type i, and NPE is net production efficiency, which is assumed to be 0.4
(Benke and Wallace 1980). We used the following literature values (Benke and Wallace 1980,
Slansky and Scriber 1982, Wotton 1994) for assimilation efficiencies for all taxa: 10% for leaves,
wood, and amorphous detritus; 30% for diatoms
and filamentous algae, 50% for fungi, and 80%
for animals. We calculated the trophic basis of
production for the entire invertebrate assemblage, which is the production-weighted average
of Bi for all taxa.
Organic matter, chlorophyll, and metabolism
We measured leaf detritus standing stock in
the same Hess and zooplankton net samples
used to collect invertebrates during the monthly
invertebrate sampling. After sorting invertebrates from the organic detritus, we removed
leaf material, dried it at 508C,weighed it, ashed
it for 4 h at 5008C, and reweighed it to estimate
AFDM/m2.
We extracted chlorophyll a from 6 rocks collected each month in each stream (except Nov.
1997) by soaking them overnight in 90% alkaline acetone. We estimated chlorophyll a concen-
tration fluorometrically (Wetzel and Likens
2000). We measured whole-stream gross primary production and community respiration on
one date (27 June 1997) for each stream using
the open-channel method of Marzolf et al.
(1994), with corrections given by Young and Huryn (1998).
Results
C isotope analysis
The d13C of filamentous algae varied with
time, and was similar to leaf d13C in HB (Fig. 1).
Hence, we could not use a mixing model to estimate the fraction of invertebrate C derived
from algae because the algae endpoint could either be higher or lower than that of leaves. We
only had one filamentous algae sample from BB,
collected just prior to canopy closure in June.
Secondary production and diet analyses
Total macroinvertebrate production was 40%
higher in BB (4.2 g m22 y21) than in HB (3.0 g
m22 y21) (Table 1). We estimated production for
59 taxa in BB and 57 taxa in HB (Appendix 1).
Secondary production in these streams was approximately log-normally distributed among
taxa so that few taxa contributed most of the
production (Fig. 2). The 3 dominant taxa in BB
were Leuctra, Chironomidae, and Epeorus. In HB,
the dominant taxa were Chironomidae, Epeorus,
and Hydropsyche (Appendix 1). The top 3 taxa
in each stream accounted for 35% of production
in BB and 45% of production in HB. This
skewed distribution of production enabled us to
436
R. O. HALL
ET AL.
[Volume 20
TABLE 1. Biomass and secondary production of functional feeding groups in Bear Brook (BB) and Main
Hubbard Brook (HB). Values in parentheses in production column represent % of total production in that
functional feeding group. P/B is the production : biomass ratio and is the biomass-specific growth rate of the
assemblage scaled to 1 y.
BB
Functional
feeding group
Scrapers
Filterers
Gatherers
Shredders
Predators
Total
Biomass
(mg/m2)
100
70
110
272
243
795
Production
(mg m22 y21)
738
431
609
1450
937
4170
(18)
(10)
(15)
(35)
(22)
(100)
HB
P/B
(1/y)
Biomass
(mg/m2)
7.38
6.11
5.54
5.33
3.86
5.25
142
112
55
52
156
517
FIG. 2. Size distribution of production in Bear
Brook (A) and Main Hubbard Brook (B). Each point
represents secondary production of one taxon ordered
from largest to smallest. Lines are random data drawn
from a normal distribution with the same mean and
SD of the logarithm of the production estimates, and
are used to compare the size distribution of organic
matter flows with that of a log-normal distribution.
Production
(mg m22 y21)
1024
555
595
359
464
3000
(34)
(18)
(20)
(12)
(15)
(100)
P/B
(1/y)
7.21
4.96
10.7
6.97
2.97
5.80
estimate diets of 93% (16 taxa) of nonpredator
production in BB and 92% (14 taxa) in HB. Thus,
we accounted for most organic matter flow in
each food web. Shredder production was 4
times higher in BB than HB, whereas scraper
production was 1.4 times higher in HB (Table 1).
Leaf detritus, amorphous detritus, and animal prey accounted for 90% of invertebrate secondary production in BB (Table 2). In contrast,
autochthonous production directly fueled only
4% of invertebrate production (5% of primary
consumer production). No taxa in BB derived
.15% of their production from algae (Appendix
2). The 2 taxa with the highest fraction of production derived from algae were Psilotreta
(shredder caddisfly, 15%) and Simulium (filterer
black fly, 14%) (Appendix 2). The dominant
scraper in BB (based on production), Epeorus,
derived only 4% of its production from algae.
In HB, autochthonous food sources provided the
base for 22% of invertebrate production (28% of
primary consumer production) (Table 2). Half of
the taxa derived .35% of their production from
algae (Appendix 2). This increase in autochthonous food sources relative to BB was primarily
because of increased diatom consumption by invertebrates rather than increased consumption
of filamentous algae (Table 2). The fraction of
secondary production derived from animal prey
was higher than the fraction of production by
predators in each stream (Tables 1, 2) because
taxa in other functional feeding groups were
also predatory, mostly hydropsychid caddisflies.
The largest organic matter flows to consumers were from leaf detritus and amorphous detritus (Table 2). These food sources have low assimilation efficiency, but constitute a large frac-
2001]
TROPHIC
437
BASIS OF INVERTEBRATE PRODUCTION
TABLE 2. Fraction of production and total organic matter flow from various food sources to the invertebrate
assemblage. Values in parentheses represent only primary consumer production, i.e., predation is excluded.
Fraction of production
derived from food sources
Food type
Amorphous detritus
Leaf detritus
Wood detritus
Fungal hyphae
Filamentous algae
Diatoms
Animal prey
Bear Brook
0.25
0.38
0.00
0.06
0.03
0.01
0.27
Main Hubbard
Brook
(0.34)
(0.52)
(0.00)
(0.08)
(0.04)
(0.01)
tion of the trophic base of the food web. Organic
matter flows from algae were much higher in
HB than BB, despite lower invertebrate production in HB. Flows from animal prey were small
relative to other flows, but large relative to total
secondary production in each stream. In BB,
consumption of animal prey (Table 2) was 92%
of total secondary production (Table 1), and in
HB 73% of secondary production was consumed by predators.
0.22
0.28
0.00
0.05
0.03
0.19
0.22
(0.28)
(0.36)
(0.00)
(0.06)
(0.04)
(0.24)
Total flows from food sources
(mg m22 y21)
Bear Brook
Main Hubbard
Brook
24,000
37,900
356
1150
946
322
3840
15,700
19,400
272
721
760
4530
2170
Leaf litter and algae availability
Leaf litter standing stock in both streams was
highest just after autumn leaf fall in November
and lowest during summer months of June to
September, but average leaf litter standing stock
was lower in HB (27 g AFDM/m2) than in BB
(74 g AFDM/m2) (Fig. 3). Average epilithic chlorophyll a was lower in HB (3.1 mg/m2) than in
BB (9.0 mg/m2). Gross primary production
FIG. 3. Mean (61 SE) standing stock of leaves in Bear Brook (A, n 5 7) and Main Hubbard Brook (B, n 5
6) from December 1996 to November 1997.
438
R. O. HALL
(GPP) measured on 1 d was higher in HB (1.5
g O2 m22 d21) than in BB (0.2 g O2 m22 d21);
however, community respiration (CR) was
slightly lower in HB (4.0 g O2 m22 d21) than in
BB (5.3 g O2 m22 d21). The GPP/CR ratio was
0.38 in HB and 0.04 in BB. Chlorophyll standing
crops just 5 d prior to metabolism measurements were 3.1 mg/m2 in HB and 6.1 mg/m2
in BB.
Discussion
Food base of the streams
Macroinvertebrate production in these 2
streams was supported largely by detrital inputs as has been shown for macroinvertebrates
in other forest streams (Hall et al. 2000) and for
guilds of mayflies and caddisflies in blackwater
rivers (Benke and Jacobi 1994, Benke and Wallace 1997). Consumption of algae was higher in
HB than in BB and this algae was primarily diatoms (Table 2). Diatoms supported a larger
fraction of invertebrate production in HB, as expected given that this site was wider and had
an open canopy.
The importance of algae to stream consumers
has been addressed by examining food sources
for many taxa (Coffman et al. 1971, Wallace et
al. 1987), but only a few studies (McCutchan
1999, Hall et al. 2000) have calculated a production-weighted estimate for the entire invertebrate assemblage. Some studies examined food
use by individual taxa using gut contents or C
isotopes (Rounick and Winterbourn 1986, Rosenfeld and Roff 1992), but even if most taxa
have high algal consumption the food web as a
whole may not show high reliance upon algae
because taxa that consume algae may be energetically unimportant. In our study, ½ of primary consumer taxa in HB derived .35% of
their production from algae, yet when weighted
by production, only 28% of primary consumer
production was supported by algae. Many studies have examined whole-stream energy budgets by measuring ratio of autochthonous input
to allochthonous input (e.g., Fisher and Likens
1973, Minshall 1978, Lamberti and Steinman
1997), but these studies may underestimate the
role of algae because algae are more easily assimilated than benthic detritus (Slansky and
Scriber 1982). Inputs to streams also may not be
indicative of available food because of export
ET AL.
[Volume 20
(see below). As suggested by Mihuc (1997), classification into functional feeding groups does
not allow assessment of the trophic base for a
stream because stream invertebrates are trophic
generalists and functional groups do not indicate food consumption. We probably misclassified functional feeding groups for certain taxa
(e.g., chironomids, possibly mayflies), but because we measured gut contents we have a
more accurate estimation of food resource use
than can be found by applying functional feeding group classifications alone.
McCutchan (1999) used stable C isotopes and
secondary production estimates (as done here)
to estimate the food base for macroinvertebrates
in a Colorado mountain stream. Algal production supported ;35 to 50% of invertebrate production in forested montane and subalpine
stream reaches and 60 to 80% of invertebrate
production in more open alpine and foothill
stream reaches (McCutchan 1999). These values
were higher than ours from HBEF, which could
be from error in gut content analyses (see below) or because terrestrial organic matter from
coniferous trees from his study is of lower food
quality or more easily exported from the reach.
In addition McCutchan’s streams may be less
shaded than HBEF streams. Stream food webs
of the boreal forest also showed greater reliance
on algae by invertebrates than what we reported
here (Junger and Planas 1994). Using stable isotopes and weighting by invertebrate biomass,
Junger and Planas (1994) found that a 2nd-order
stream food web derived 25% of C from autochthonous production and a 4th-order stream
food web derived 60%, although their estimates
were from only one date and may not represent
annual food consumption.
The fraction of production derived from algae
in BB and HB may be underestimated. Algae
produce copious amounts of noncellular exopolymers (Decho 1990), which coat rocks with a
noticeable slime layer, and would be readily assimilated by benthic invertebrates (Decho and
Moriarty 1990, Couch et al. 1996). This exopolymer would not be recognized as algal material
under a microscope, but rather would be classified as amorphous detritus. Thus, it is unclear
what fraction of amorphous detritus was derived from algae. Given the low ingestion of algae in BB, we expect that ingested amorphous
detritus was derived from mostly allochthonous
inputs. However, even if ½ of amorphous detri-
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TROPHIC
BASIS OF INVERTEBRATE PRODUCTION
FIG. 4. Relationship between annual average leaf
litter standing stock and annual secondary production
in 3 streams. Solid dots are data for stream C55 at
Coweeta Hydrologic Laboratory (Wallace et al. 1999).
Hollow points are for Bear Brook (BB) and main Hubbard Brook (HB) (this study). Line is a least-squares
fit linear regression (y 5 0.04x 1 2.34, r2 5 0.92) using
only the C55 data.
tus were algal-derived, then primary consumers
would have obtained 21% of their production
from algae, and the food web would still be predominantly based on allochthonous food consumption.
Errors from misclassification of exopolymers
and from assumptions of assimilation efficiencies would have been alleviated by using stable
C isotope analyses. Because 13C ratios of a consumer represent assimilated rather than ingested C, our estimates of the fraction of invertebrate C derived from algae would probably
have been more accurate. Algal C must be purified (Hamilton and Lewis 1992, McCutchan
1999) so that it is not contaminated with detrital
C. We sampled filamentous algae as our pure
algae source, whereas invertebrates consumed
mostly diatoms. It is unknown if diatoms have
the same d13C as filamentous algae, though we
expect the temporal patterns in d13C to stay the
same. Algal d13C must consistently differ from
detrital d13C to use C isotopes to determine resource use; in our study, algal d13C changed
with time to be both higher and lower than detrital d13C. There was good separation between
leaves and algae in BB, but we measured algal
d13C only once. In a Colorado mountain stream,
algal d13C changed with time, but usually remained more enriched than leaf litter (McCutchan and Lewis, in press). This shift in d13C
439
underscores the need to sample algae over a
time span similar to the turnover time of invertebrate C. If we had used data from one date as
our algal endpoint, then we would have erred
in interpreting the fraction of invertebrate C derived from algae.
Mayer and Likens (1987) found that algae
were the dominant organic matter source for
Neophylax aniqua in BB, and they hypothesized
that algae could be important for other invertebrates in the food web. In our study, Neophylax
derived only 9% of its production from algae
(Appendix 2). This species was rarer than reported by Mayer and Likens (1987), who estimated an April to July biomass of 20 mg/m (20
mg/m2 given a stream width of 1 m in that section). In our study, Neophylax biomass was only
1.4 mg/m2 during the same months. Moreover,
there were no other taxa in BB that derived
.15% of their production from algae (Appendix
2).
The BB reach had higher chlorophyll standing
crops than HB, although consumption of algae
was lower in BB than HB. Chlorophyll values
were low in each stream, typical of low-nutrient
streams (Biggs 1995). Higher chlorophyll may
simply be a physiological response to low light
(Darley 1982), with biomass not being much different. Turnover of algae was probably higher
in HB than BB because GPP was higher in HB.
Although we only have one measurement from
each stream, it is interesting that GPP/CR ratios
(0.04 in BB, 0.38 in HB) were similar to the fraction of primary consumer production derived
from algae (0.05 in BB, 0.28 in HB). This relationship suggests that the availability of algal C
determined its importance to the food web.
Standing stocks of leaf litter in the 2 streams
were ;10% of annual inputs of leaves; ;600 g
AFDM/m2 is added to BB each year (Findlay et
al. 1997). Our standing stock estimates are ;5
to 12% of those from Fisher and Likens (1973)
because these authors defined the stream area
as the active channel of BB rather than the wetted channel, which only occupies 20% of the active channel. Leaf standing stocks were .2-fold
higher in BB than in HB (Figs 3, 4) probably
because increased channel complexity (boulders, debris dams, pools, etc.) can hold and trap
leaves during floods.
Secondary production
Invertebrate production in BB and HB was
low. Of the 58 production estimates reported by
440
R. O. HALL
Benke (1993), 86% were higher than estimates
for BB and 95% were higher than estimates for
HB. Production estimated by Fisher and Likens
(1973) for BB (4.3 g AFDM m22 y21), was close
to our measurement showing low variability between the 2 studies. A large fraction of invertebrate secondary production was consumed by
predators, which has been noted in other small
streams (Coffman et al. 1971, Huryn 1996, Wallace et al. 1999). It is likely that predators were
food limited in both BB and HB, and given that
they consumed nearly all prey production (Table 2), they may limit production of certain prey.
There were many taxa in these streams but most
of the production was attributed to a few taxa
as was observed for patterns of organic matter
flows (Hall et al. 2000). Indeed, the distribution
of production values was approximately lognormal as has been shown for species abundances (Preston 1962).
Why was production low in these 2 streams?
One possibility is physical disturbance from
floods, which can reduce invertebrate fauna in
some streams (Fisher et al. 1982, Flecker and Feifarek 1994). The flooding regime in streams at
HBEF is extremely flashy (Hall and Likens, in
press), which might be expected to regulate invertebrate production. However, the largest
flood of the year occurred on 15 July 1997, just
prior to our July sampling date, and this flood
did not affect invertebrate populations in BB
(Hall and Likens, in press). Likewise, both biomass and abundance in HB were higher in July
than June, suggesting that floods did not directly decrease invertebrate populations in that
stream.
Alternatively, invertebrate production can be
limited by food resources, which has been experimentally demonstrated for algae (e.g., Peterson et al. 1993) and for detritus (Wallace et al.
1999). Wallace et al. (1999) used long-term secondary production data, coupled with an experiment lowering detrital resources, to show a
strong positive relationship between leaf litter
standing stock and secondary production in a
forested stream at Coweeta Hydrologic Laboratory, North Carolina (Fig. 4). Using mean annual standing stock of leaf-litter and secondary
production estimates in our study, BB and HB
production estimates fell close to the line estimated by Wallace et al. (1999) (Fig. 4), suggesting that production in our streams may be limited by availability of leaf detritus, especially
ET AL.
[Volume 20
given that algal consumption is low in both
streams. Leaf standing stocks in BB and HB
were lower than all but the litter exclusion treatment in the Coweeta stream, despite similar leaf
litter inputs to streams at Coweeta and HBEF
(Findlay et al. 1997, Wallace et al. 1997a). HBEF
streams contain low leaf standing stocks in the
wetted channel because of their flashy nature
(Hall and Likens, in press). Leaves accumulate
in the stream during leaf fall until floods push
them out of the wetted channel (Fig. 3). Leaves
become unavailable to most stream biota but are
still in the active channel. This phenomenon has
been noted for other streams; e.g., export of
leaves is a function of peak annual discharge at
Coweeta (Wallace et al. 1995). We suggest that
production in these streams is low because animals are limited by food resources of which
detritus is an important component.
Higher secondary production in BB relative to
HB may be caused by the increased standing
stock of leaf detritus in BB. Annual consumption of leaf material is a small % of input to BB
(6%), but a large % of leaf litter standing stock
(51% for BB and 72% for HB). We do not have
estimates of leaf turnover in the channel, but after autumn standing stocks were relatively constant with time (Fig. 3). It is notable that higher
algal consumption in HB did not lead to production rates that were equal to or higher than
those in BB. HB was oligotrophic with NH4 ,4
mg N/L, NO3 20–40 mg N/L, and PO4 ,2 mg
P/L (E. S. Bernhardt, Cornell University, Ithaca,
New York, and R. O. Hall, unpublished data),
and there is experimental evidence for strong
nutrient limitation of periphyton in this stream
(E. S. Bernhardt, unpublished data). Thus, despite that fact that secondary production in both
streams is likely limited by algae production, we
suggest that higher production in BB is caused
by higher detritus availability there.
We suggest that despite low detrital standing
stocks in BB, allochthonous inputs provide most
of the base of the food web because of low algal
production caused by either light or nutrient
limitation. In HB, algae supported a larger fraction of invertebrate production, but nonetheless
allochthonous material was still the dominant
food source. We hypothesize that higher nutrient supply to this stream would increase both
algal and invertebrate production as was found
by Peterson et al. (1993). Because of the low detrital standing stock we emphasize that export
2001]
TROPHIC
BASIS OF INVERTEBRATE PRODUCTION
of allochthonous (or autochthonous) C be considered along with inputs of litterfall and net
primary production to understand control of the
available food base for macroinvertebrates.
Our secondary production estimates and gutcontent analysis provided a means to quantitatively estimate the resource base of a food web,
which can facilitate understanding of how intrinsic or extrinsic processes can alter ecosystem
dynamics (Polis et al. 1997). We showed that allochthonous inputs likely control foodweb dynamics, similar to other streams (e.g., Wallace et
al. 1999, Hall et al. 2000). Other stream food
webs, however, will be driven more by autochthonous inputs and will be functionally different. With the ability to quantify the food base
in streams using this method or others (e.g.,
McCutchan 1999) we can begin to address how
within-stream and outside-stream processes
combine to determine community and ecosystem dynamics.
Acknowledgements
E. Evans assisted with sorting invertebrates.
M. Carmona and K. Macneale braved winter
field sampling. Thanks to M. Paul and P. Mulholland who supplied metabolism data for HB
and BB, respectively. J. B. Wallace provided data
for Fig. 4. Comments from M. Marshall, K. Macneale, J. McCutchan, J. Feminella, and 2 anonymous reviewers improved early drafts of the
manuscript. This paper is a contribution to the
Hubbard Brook Ecosystem Study and to the
program of the Institute of Ecosystem Studies.
The Northeastern Research Station, USDA Forest Service, operates and maintains HBEF. Financial support was provided by the Andrew
W. Mellon Foundation to G. E. Likens.
Literature Cited
BENKE, A. C. 1984. Secondary production of aquatic
insects. Pages 289–322 in V. H. Resh and D. M.
Rosenberg (editors). The ecology of aquatic insects. Praeger Publishers, New York.
BENKE, A. C. 1993. Concepts and patterns of invertebrate production in running waters. Verhandlungen der Internationalen Vereinigung für theoretische und angewandte Limnologie 25:15–38.
BENKE, A. C., A. D. HURYN, L. A. SMOCK, AND J. B.
WALLACE. 1999. Length-mass relationships for
freshwater invertebrates in North America with
particular reference to the southeastern United
441
States. Journal of the North American Benthological Society 18:308–343.
BENKE, A. C., AND D. I. JACOBI. 1994. Production dynamics and resource utilization of snag-dwelling
mayflies in a blackwater river. Ecology 75:1219–
1232.
BENKE, A. C., AND J. B. WALLACE. 1980. Trophic basis
of production among net-spinning caddisflies in
a southern Appalachian stream. Ecology 61:108–
118.
BENKE, A. C., AND J. B. WALLACE. 1997. Trophic basis
of production among riverine caddisflies: implications for food web analysis. Ecology 78:1132–
1145.
BIGGS, B. J. F. 1995. The contribution of disturbance,
catchment geology and land use to the habitat
template of periphyton in stream ecosystems.
Freshwater Biology 33:419–438.
COFFMAN, W. P., K. W. CUMMINS, AND J. C. WUYCHECK. 1971. Energy flow in a woodland stream
ecosystem. I. Tissue support trophic structure of
the autumnal community. Achiv für Hydrobiologie 68:232–276.
COUCH, C. A., J. L. MEYER, AND R. O. HALL. 1996.
Incorporation of bacterial extracellular polysaccharide by black fly larvae (Simuliidae). Journal of
the North American Benthological Society 15:
289–299.
CUMMINS, K. W. 1973. Trophic relations of aquatic insects. Annual Review of Entomology 18:183–206.
DARLEY, W. M. 1982. Algal biology, a physiological
approach. Blackwell, Oxford, UK.
DECHO, A. W. 1990. Microbial exopolymer secretions
in ocean environments: their role(s) in food webs
and marine processes. Oceanography and Marine
Biology Annual Review 28:73–153.
DECHO, A. W., AND D. J. W. MORIARTY. 1990. Investigation of bacterial mucus-exopolymer utilization
by marine animals: methodology and results using harpacticoid copepods. Limnology and
Oceanography 35:1039–1049.
FIANCE, S. B. 1979. Effects of lowered pH on the composition and structure of stream invertebrate
communities. PhD Dissertation, Cornell University, Ithaca, New York.
FINDLAY, S., G. E. LIKENS, L. HEDIN, S. G. FISHER, AND
W. H. MCDOWELL. 1997. Organic matter dynamics in Bear Brook, Hubbard Brook Experimental
Forest, New Hampshire, USA. Pages 43–46 in J.
R. Webster and J. L. Meyer (editors). Stream organic matter budgets. Journal of the North American Benthological Society 16.
FISHER, S. G., L. GRAY, N. GRIMM, AND D. BUSCH. 1982.
Temporal succession in a desert stream ecosystem
following flash flooding. Ecological Monographs
52:93–110.
FISHER, S. G., AND G. E. LIKENS. 1973. Energy flow in
Bear Brook, New Hampshire: an integrative ap-
442
R. O. HALL
proach to stream ecosystem metabolism. Ecological Monographs 43:421–439.
FLECKER, A. S., AND B. FEIFAREK. 1994. Disturbance
and the temporal variability of invertebrate assemblages in two Andean streams. Freshwater
Biology 31:131–142.
HALL, R. O., AND G. E. LIKENS. Ecological implications
of high discharge variability in streams of the
Hubbard Brook Experimental Forest. Verhandlungen der Internationalen Vereinigung für theoretische und angewandte Limnologie (in press).
HALL, R. O., J. B. WALLACE, AND S. L. EGGERT. 2000.
Patterns of organic matter flow in stream food
webs with reduced detrital resource base. Ecology 81:3445–3463.
HAMILTON, S. K., AND W. M. LEWIS, JR. 1992. Stable
carbon and nitrogen isotopes in algae and detritus from the Orinoco River floodplain, Venezuela.
Geochimica et Cosmochimica Acta 56:4237–4246.
HILL, W. R., AND B. C. HARVEY. 1990. Periphyton response to higher trophic levels and light in a
shaded stream. Canadian Journal of Fisheries and
Aquatic Sciences 47:2307–2314.
HURYN, A. D. 1990. Growth and voltinism of lotic
midge larvae: patterns across an Appalachian
Mountain basin. Limnology and Oceanography
35:339–351.
HURYN, A. D. 1996. An appraisal of the Allen paradox
in a New Zealand trout stream. Limnology and
Oceanography 41:243–252.
HYNES, H. B. N. 1975. The stream and its valley. Verhandlungen der Internationalen Vereinigung für
theoretische und angewandte Limnologie 19:1–
15.
JUNGER, M., AND D. PLANAS. 1994. Quantitative use of
stable carbon isotope analysis to determine the
trophic base of invertebrate communities in a boreal forest lotic system. Canadian Journal of Fisheries and Aquatic Sciences 51:52–61.
LAMBERTI, G. A. 1996. The role of periphyton in benthic food webs. Pages 533–572 in R. J. Stevenson,
M. L. Bothwell, and R. L. Lowe (editors). Algal
ecology. Academic Press, San Diego.
LAMBERTI, G. A., AND A. D. STEINMAN. 1997. A comparison of primary production in stream ecosystems. Pages 95–104 in J. R. Webster and J. L. Meyer (editors). Stream organic matter budgets. Journal of the North American Benthological Society
16.
LIKENS, G. E. 1972. Eutrophication and aquatic ecosystems. Pages 3–13 in G. E. Likens (editor). Nutrients and eutrophication. Special Symposia Volume 1. American Society of Limnology and
Oceanography, Allen Press, Lawrence, Kansas.
MARZOLF, E. R., P. J. MULHOLLAND, AND A. D. STEINMAN. 1994. Improvements to the diurnal upstream-downstream dissolved oxygen change
technique for determining whole-stream metab-
ET AL.
[Volume 20
olism in small streams. Canadian Journal of Fisheries and Aquatic Sciences 51:1591–1599.
MAYER, M. S., AND G. E. LIKENS. 1987. The importance
of algae in a shaded headwater stream as food
for an abundant caddisfly. Journal of the North
American Benthological Society 6:262–269.
MCCUTCHAN, J. H. 1999. Carbon sources for macroinvertebrates in St. Vrain Creek, Colorado. PhD
Dissertation, University of Colorado, Boulder,
Colorado.
MCCUTCHAN, J. H., AND W. M. LEWIS, JR. Seasonal variation in stable isotope ratios of stream algae. Verhandlungen der Internationalen Vereinigung für
theoretische und angewandte Limnologie (in
press).
MEYER, J. L., AND G. E. LIKENS. 1979. Transport and
transformation of phosphorus in a forest stream
ecosystem. Ecology 60:1255–1269.
MIHUC, T. B. 1997. The functional trophic role of lotic
primary consumers: generalist vs. specialist strategies. Freshwater Biology 37:455–462.
MINSHALL, G. W. 1978. Autotrophy in stream ecosystems. BioScience 28:767–771.
PETERSON, B. J., L. A. DEEGAN, J. HELFRICH, J. E. HOBBIE, M. HULLAR, B. MOLLER, T. E. FORD, A. HERSHEY, A. HILTNER, G. KIPPHUT, M. A. LOCK, D. M.
FIEBIG, V. MCKINLEY, M. C. MILLER, J. R. VESTAL,
R. VENTULLO, AND G. VOLK. 1993. Biological responses of a tundra river to fertilization. Ecology
74:653–672.
POLIS, G. A., W. B. ANDERSON, AND R. D. HOLT. 1997.
Towards an integration of landscape and food
web ecology: the dynamics of spatially subsidized food webs. Annual Review of Ecology and
Systematics 28:289–316.
PRESTON, F. W. 1962. The canonical distribution of
commoness and rarity: part I. Ecology 43:185–
215, 431–432.
ROSENFELD, J. S., AND R. J. MACKAY 1987. Assessing
the food base of stream ecosystems: alternatives
to the P/R ratio. Oikos 50:141–147.
ROSENFELD, J. S., AND J. C. ROFF. 1992. Examination of
the carbon base in southern Ontario streams using stable isotopes. Journal of the North American
Benthological Society 11:1–10.
ROUNICK, J. S., AND M. J. WINTERBOURN. 1986. Stable
carbon isotopes and carbon flow in ecosystems.
BioScience 36:171–177.
SLANSKY, F., AND J. M. SCRIBER. 1982. Selected bibliography and summary of quantitative food utilization by immature insects. Bulletin of the Entomological Society of America 28:43–55.
WALLACE, J. B., A. C. BENKE, A. H. LINGLE, AND K.
PARSONS. 1987. Trophic pathways of macroinvertebrate primary consumers in subtropical blackwater streams. Archiv für Hydrobiologie Supplement 74:423–451.
WALLACE, J. B., T. F. CUFFNEY, S. L. EGGERT, AND M.
2001]
TROPHIC
BASIS OF INVERTEBRATE PRODUCTION
R. WHILES. 1997a. Stream organic matter inputs,
storage, and export for Satellite Branch at Coweeta Hydrologic Laboratory, North Carolina,
USA. Pages 67–74 in J. R. Webster and J. L. Meyer
(editors). Stream organic matter budgets. Journal
of the North American Benthological Society 16.
WALLACE, J. B., S. L. EGGERT, J. L. MEYER, AND J. R.
WEBSTER. 1997b. Multiple trophic levels of a forest
stream linked to terrestrial litter inputs. Science
277:102–104.
WALLACE, J. B., S. L. EGGERT, J. L. MEYER, AND J. R.
WEBSTER. 1999. Effects of resource limitation on a
detrital-based ecosystem. Ecological Monographs
69:409–442.
WALLACE, J. B., M. R. WHILES, S. EGGERT, T. F. CUFFNEY, G. J. LUGTHART, AND K. CHUNG. 1995. Longterm dynamics of coarse particulate organic matter in three Appalachian Mountain streams. Journal of the North American Benthological Society
14:217–232.
443
WATERS, T. F. 1977. Secondary production in inland
waters. Advances in Ecological Research 10:91–
164.
WEBSTER, J. R., AND J. L. MEYER (EDITORS). 1997.
Stream organic matter budgets. Journal of the
North American Benthological Society 16:3–161.
WETZEL, R. G., AND G. E. LIKENS. 2000. Limnological
analyses. 3rd edition. Springer-Verlag, New York.
WOTTON, R. S. 1994. Particulate and dissolved organic
matter as food. Pages 235–288 in R. S. Wotton (editor). Biology of particles in aquatic systems. CRC
Press, Boca Raton, Florida.
YOUNG, R. G., AND A. D. HURYN. 1998. Comment: improvements to the diurnal upstream-downstream
dissolved oxygen change technique for determining whole-stream metabolism in small streams.
Canadian Journal of Fisheries and Aquatic Sciences 55:1784–1785.
Received: 9 May 2000
Accepted: 22 March 2001
Ephemeroptera
Sum filterers
Eurylophella
Habrophlebia
Ephemerella
Drunella
Ameletus
Sum scrapers
Wormaldia
Dolophilodes
Polycentropus
Diplectrona
Hydropsyche
Arctopsyche
Parapsyche
Micrasema
Prosimulium
Simulium
Stegopterna
Dixa
Epeorus
Stenonema
Heptagenia
Stenacron
Baetis
Glossosoma
Neophylax
Paleagapetus
Oulimnius
Promoresia
Dryopidae
Taxon
24
21
10
8
3
12
24
21
11
12
10
21
10
21
11
5
20
11
12
12
648
200
27
0.2
0
9.5
1007
2.4
60.4
9
7.3
4.4
0
28.6
0.2
421
103
5.6
6
243
0
14.9
0
631
0.5
59.5
13.2
43.1
0.7
0
Abundance
(ind./m2)
70.5
37.9
2.31
0.03
0
3.86
100
1.11
12.4
3.95
0.54
0.43
0
32.5
0.07
15.3
3.82
0.04
0.21
64.8
0
3.57
0
24.2
0.03
4.31
1.34
1.69
0.09
0
Biomass
(mg/m2)
431
119
12.5
0.2a
0
11.9
738
5.6a
68.9
20.3
2.7a
2.1a
0
89.2
0.4a
154
86.5
0.4a
1.0a
422
0
16.1a
0
266
0.4a
18.2
8
7.2
0.5a
0
Production
(mg
m22y21)
6.1
3.1
5.4
5.0
0
3.1
7.4
5.0
5.6
5.1
5.0
5.0
0
2.7
5.0
10.1
22.6
10.0
5.0
6.5
0
4.5
0
11.0
12.4
4.2
6.0
4.3
5.0
0
P/B
(1/y)
666
15.9
46.4
4.5
0.2
6.3
927
0
57.6
12.9
0
47.6
11.8
0
3.6
387
145
0.8
0
388
46.3
14.9
1.4
304
64.8
2.7
0
83.4
21.3
0.2
112
1.64
2.17
1.38
0.14
2.23
142
0
15.5
8.41
0
42.4
30.2
0
0.5
9.42
5.74
0.07
0
63.5
31.1
13.7
3.96
12.3
11.7
0.6
0
2.42
2.04
1.05
Abundance Biomass
(ind./m2) (mg/m2)
555
5.7
19.4
6.9a
0.7a
5.2
1024
0
80.9
20.3
0
209
54.4
0
2.5a
80.7
107
0.5a
0
564
119
62
11.9a
98.6
145
2.4
0
12.9
8.1
0
Production
(mg
m22y21)
5.0
3.4
8.9
5.0
5.0
2.4
7.2
0
5.2
2.4
0
4.9
1.8
0
5.0
8.6
18.7
9.0
0
8.9
3.8
4.5
3.0
8.0
12.4
4.0
0
5.3
3.9
0
P/B
(1/y)
ET AL.
Gatherer
Diptera
Trichoptera
Coleoptera
Trichoptera
Ephemeroptera
Order
CPI
(mo)
HB
R. O. HALL
Filterer
Scraper
Functional
group
BB
APPENDIX 1. Annual average abundance, biomass, and production of all taxa from Bear Brook (BB) and Main Hubbard Brook (HB), Hubbard Brook Experimental Forest, New Hampshire. CPI is cohort production interval and is reported for all taxa for which the size-frequency method was used to calculate production.
P/B is production to biomass ratio and thus a specific growth rate with units of 1/y.
444
[Volume 20
Predator
Plecoptera
Odonata
Diptera
Trichoptera
Plecoptera
Copepodab
Oligochaetab
Diptera
Order
Sum shredders
Boyeria
Lanthus
Sweltsa
Alloperla
Isoperla
Acroneuria
Agnetina
20
21
11
24
34
12
9
11
23
12
9
1710
0
0.2
146
0.3
28.2
0
0
10,200
1110
69.4
0
22.5
217
3.5
10.2
7.5
0.2
0.3
205
24.3
0
45.6
2.5
1
Sum gatherers
Leuctra
Paracapnia
Allocapnia
Tallaperla
Amphinemura
Soyedina
Ostrocerca
Strophopteryx
Oemopteryx
Taeniopteryx
Lepidostoma
Pycnopsyche
Apatania
Psilotreta
Tipula
Molophilus
10
8
9820
1.7
1
56.7
82.1
Abundance
(ind./m2)
Chironomidae
Nymphomyia
Sciaridae
Taxon
CPI
(mo)
272
0
0.2
49.3
0.13
45.7
0
0
110
55.7
3.44
0
24.6
10.7
1.5
1.82
1.74
0.14
0.12
19
43.4
0
75.3
33.8
0.34
62.6
0
0.11
0.15
2.89
Biomass
(mg/m2)
1450
0
0.5a
161
0.3a
236
0
0
609
571
33.9
0
95.6
94
7.5a
9.1a
8.7a
0.7a
0.7a
163
172
0
167
125
1.7a
449
0.01a
0.5a
1.5a
14.4a
Production
(mg
m22y21)
5.3
0
2.5
3.3
2.3
5.2
0
0
5.5
10.3
9.9
0
3.9
8.8
5.0
5.0
5.0
5.0
5.7
8.6
4.0
0
2.2
3.7
5.0
7.2
5.0
5.0
10.0
5.0
P/B
(1/y)
911
0.4
0.4
101
22.5
5.3
2.4
0.2
6480
386
50.4
220
4.7
88.5
0.2
2.2
57.7
0
16.9
81.2
0
2.2
1.4
0
0
6320
16.6
0
9.7
60.4
51.5
2.41
0.87
19.9
20.1
4.11
1.03
0.03
55.4
23.5
3.64
0.69
2.15
3.65
0.15
0.06
0.43
0
5.94
10.4
0
0.6
0.28
0
0
46.3
0.02
0
0.03
1.48
Abundance Biomass
(ind./m2) (mg/m2)
HB
359
7.2a
2.6a
62.7
45.2
16.7
3.1a
0.1a
595
179
29.7
3.5a
7.9a
31.3
0.8a
0.3a
2.2a
0
34.1
66
0
3.0a
0.8a
0
0
549
0.1
0
0.3a
7.4a
Production
(mg
m22y21)
7.0
3.0
3.0
3.2
2.3
4.1
3.0
3.0
10.7
7.6
8.2
5.0
3.7
8.6
5.0
5.0
5.0
0
5.7
6.4
0
5.0
3.0
0
0
11.9
5.0
0
10.0
5.0
P/B
(1/y)
TROPHIC
Shredder
Functional
group
BB
APPENDIX 1. Continued.
2001]
BASIS OF INVERTEBRATE PRODUCTION
445
b
13,814.7
Sum all groups
0.2
118
0.2
527
43.1
23.8
191
1.1
0.2
0
0
14.2
5.7
142
3.6
1245
12
12
24
12
12
12
12
22
Sum predators
Nigronia
Rhyacophila
Molanna
Tanypodinae
Ceratopogonidae
Hexatoma
Dicranota
Pedicia
Cryptolabis
Atherix
Dolichipodidae
Chelifera
Oreogeton
Hydrachnidia
Eurycea
Taxon
Abundance
(ind./m2)
795.2
243.3
0.74
28.1
0.05
7.06
4.59
45.4
16.3
1.52
0.02
0
0
0.47
1.58
0.38
41.7
Biomass
(mg/m2)
Production was calculated from an assumed P/B and not using size-frequency method
Class
Acariformes
Urodela
Diptera
Megaloptera
Trichoptera
Order
CPI
(mo)
4170
937
1.3a
114
0.3a
42.9
26.7
119
87.5
7.6a
0.1a
0
0
2.5
7
1.9a
129
Production
(mg
m22y21)
5.2
3.9
1.7
4.1
5.0
6.1
5.8
2.6
5.4
5.0
5.0
0
0
5.3
4.4
5.0
3.1
P/B
(1/y)
9692.3
705.2
4.3
13.7
0
217
30.5
13.9
48.5
0
0
7.3
0.2
29.6
0
208
0.8
517.8
156.3
21.6
8.51
0
3.55
5.45
35.4
13.1
0
0
9.46
0.03
2.78
0
0.55
7.41
Abundance Biomass
(ind./m2) (mg/m2)
HB
2997.2
463.7
36.0a
25
0
18.5
25
98.8
66.7
0
0
11.2
0.2a
19.7
0
2.8a
22.2a
Production
(mg
m22y21)
5.8
3.0
1.7
2.9
0
5.2
4.6
2.8
5.1
0
0
1.2
5.0
5.0
0
5.0
3.0
P/B
(1/y)
R. O. HALL
a
Functional
group
BB
APPENDIX 1. Continued.
446
ET AL.
[Volume 20
0.486
0.483
0.478
0.056
0.125
0.353
0.078
0.210
0.187
0.060
0.100
0.221
0.120
0.166
Main Hubbard Brook
Ephemeroptera
Baetis
Epeorus
Habrophlebia
Heptagenia
Stenonema
Plecoptera
Leuctra
Trichoptera
Arctopsyche
Dolophilodes
Glossosoma
Hydropsyche
Lepidostoma
Diptera
Chironomidae
Prosimulium
Simulium
Diptera
0.185
0.355
0.301
0.112
0.231
0.400
0.268
0.131
0.240
0.179
0.847
0.420
0.234
0.414
0.422
0.406
0.644
0.528
0.515
0.417
0.756
0.649
0.553
0.196
0.391
0.552
0.439
0.539
0.585
0.801
0.000
0.000
0.000
0.000
0.000
0.012
0.000
0.015
0.024
0.003
0.050
0.000
0.000
0.000
0.009
0.003
0.000
0.001
0.000
0.000
0.000
0.000
0.000
0.019
0.000
0.037
0.006
0.000
0.000
0.000
0.000
0.020
0.129
0.028
0.111
0.048
0.073
0.028
0.161
0.041
0.000
0.106
0.111
0.017
0.067
0.201
0.009
0.062
0.056
0.000
0.128
0.048
0.000
0.028
0.013
0.087
0.050
0.044
0.089
0.092
0.130
0.016
0.039
0.001
0.017
0.041
0.030
0.093
0.000
0.027
0.000
0.023
0.024
0.279
0.062
0.023
0.047
0.056
0.003
0.006
0.015
0.058
0.088
0.007
0.079
0.070
0.018
0.100
0.136
0.006
0.199
0.127
0.053
0.803
0.515
0.146
0.551
0.522
0.389
0.019
0.004
0.230
0.511
0.124
0.012
0.019
0.012
0.001
0.001
0.000
0.005
0.005
0.000
0.022
0.073
0.005
0.010
0.012
0.009
0.012
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.671
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.006
0.021
0.000
0.710
0.400
0.001
0.000
0.001
0.054
0.000
1199
6810
231
87
374
1580
107
425
677
311
165
3034
242
444
2844
3676
854
826
6061
489
217
894
164
45
183
1072
5342
1174
274
275
457
5010
146
173
690
1790
364
264
869
933
1398
5768
473
1110
2805
4286
1911
1240
7347
354
1806
2647
253
436
1627
2378
4931
2081
1266
2500
0
0
0
0
0
55
0
31
87
18
82
0
0
0
62
27
0
3
0
0
0
0
0
42
0
160
62
0
0
0
0
56
12
9
66
43
20
12
116
43
0
290
45
9
89
423
5
29
161
0
61
39
0
12
11
75
113
34
39
58
106
75
6
1
17
61
14
63
0
46
0
106
16
249
138
81
47
44
14
2
12
79
13
5
109
100
69
129
98
6
163
596
9
415
513
218
250
352
470
34
2
1052
343
110
27
68
12
1
5
0
4
7
0
16
102
7
39
15
6
13
0
0
0
0
0
0
0
0
0
501
0
0
0
0
0
0
0
0
0
0
2
12
0
226
238
1
0
0
17
0
TROPHIC
Trichoptera
Plecoptera
0.428
0.348
0.288
0.351
0.425
0.576
0.091
0.219
0.359
0.020
0.044
0.249
0.476
0.304
0.127
0.088
Taxon
Baetis
Epeorus
Eurylophella
Amphinemura
Leuctra
Paracapnia
Tallaperla
Lepidostoma
Neophylax
Parapsyche
Psilotreta
Pycnopsyche
Chironomidae
Prosimulium
Simulium
Tipula
Bear Brook
Ephemeroptera
Order
Organic matter flows
FilaAmorFilamenAmorWood
menphous
Leaf
Wood Fungal
tous
Animal phous
Leaf detri- Fungal tous
Animal
detritus detritus detritus hyphae algae Diatoms prey
detritus detritus tus hyphae algae Diatoms prey
Fraction of production
APPENDIX 2. Fraction of invertebrate production and organic matter flows (mg m22 y21) derived from various food sources.
2001]
BASIS OF INVERTEBRATE PRODUCTION
447