Headwater Stream Communities Research Articles

Leaf litter decomposition and macroinvertebrate communities in headwater streams draining pine and hardwood catchments

Benthic invertebrates, litter decomposition, andlitterbag invertebrates were examined in streamsdraining pine monoculture and undisturbed hardwoodcatchments at the Coweeta Hydrologic Laboratory in thesouthern Appalachian Mountains, USA. Bimonthlybenthic samples were collected from a stream draininga pine catchment at Coweeta during 1992, and comparedto previously collected (1989–1990) benthic data froma stream draining an adjacent hardwood catchment. Litter decomposition and litterbag invertebrates wereexamined by placing litterbags filled with pine ormaple litter in streams draining pine catchments andhardwood catchments during 1992–1993 and 1993–1994. Total benthic invertebrate abundance and biomass inthe pine stream was ca. 57% and 74% that of thehardwood stream, respectively. Shredder biomass wasalso lower in the pine stream but, as a result ofhigher Leuctra spp. abundance, shredderabundance was higher in the pine stream than thehardwood stream. Decomposition rates of both pine andred maple litter were significantly faster in pinestreams than adjacent hardwood streams (p<0.05). Total shredder abundance, biomass, and production weresimilar in maple bags from pine and hardwood streams. However, trichopteran shredder abundance and biomass,and production of some trichopteran taxa such asLepidostoma spp., were significantly higher in maplelitterbags from pine streams than hardwood streams(p<0.05). In contrast, plecopteran shredders(mainly Tallaperla sp.) were more important inmaple litterbags from hardwood streams. Shredderswere well represented in pine litterbags from pinestreams, but low shredder values were obtained frompine litterbags in hardwood streams. Resultssuggest conversion of hardwood forest to pinemonoculture influences taxonomic composition of streaminvertebrates and litter decomposition dynamics. Although the impact of this landscape-leveldisturbance on invertebrate shredder communitiesappeared somewhat subtle, significant differences indecomposition dynamics indicate vital ecosystem-levelprocesses are altered in streams draining pinecatchments.

The use of Percent Model Affinity to assess the effects of agriculture on benthic invertebrate communities in headwater streams of southern Ontario, Canada

1. Benthic invertebrates were surveyed in 213 headwater streams in southern Ontario to test the utility of Percent Model Affinity (PMA) for assessing the relative impact of agriculture on invertebrate communities. Qualitative samples were collected from reference (= forested, sixty‐nine samples) and agricultural (195 samples) streams between May 1990 and August 1993. The percentage composition of samples from reference streams was averaged by season and type of substratum, and the most homogeneous groupings were used as expected communities for the calculation of PMA.2. The lower confidence limit about the mean PMA for each expected community was calculated as for a one‐tailed t‐test comparing a single observation with the mean of a sample. Samples from agricultural streams whose PMA scores were outside these confidence limits were judged to indicate significant impact.3. The sensitivity of PMA to differences in land use increased with taxonomic resolution: 40% of agricultural sites were significantly different from reference communities at the ordinal level, 79.5% were significantly different at the lowest practical taxonomic level. Most of the increase in discrimination between reference and agricultural sites was due to Chironomidae. Identification to species, rather than genus, yielded only a small increase in discrimination between reference and agricultural sites, largely because of taxonomic difficulties and because most members of several diverse genera were very similar in their distributions.4. All of the samples from streams which drained orchards and vinyards (n = 7) were significantly different from the expected communities, as were 89% of those from streams draining corn (n = 94). A larger percentage of streams draining hay (78%, n = 26) were impacted than were streams bordered by pasture (66%, n = 51), but the average magnitude of impact was greater in pasture streams. Only six of eleven samples from streams draining tobacco indicated significant impact.5. The effect of land use adjacent to the sampling site was greatest early in the growing season. Comparison of natural channels and ditches draining agricultural land suggests that channelization and subsurface tile drainage eliminate most of the benefits of riparian buffer strips and magnify the effects of farming practices on the benthic fauna.

Periphyton Communities in Headwater Streams of Different Water Chemistry in the Central Appalachian Mountains

Abstract To examine impacts of acidification, we studied periphyton communities in three West Virginia streams whose mean pH varied from 4.2 to 7.8. We measured algal composition, cell densities, chlorophyll a, ash free dry weight, and areal and chlorophyll-specific production in the winter and spring of 1993 and 1994. The most acidic stream had the lowest species richness and few diatoms and was dominated by a green-alga. The most alkaline stream had the highest species richness and was dominated by Chlamydomonas. Chlorophyll a and ash free dry weight were significantly lower in the most acidic stream. Areal production was not different between streams, whereas chlorophyll-specific production was highest in the acidic stream.

Macroinvertebrate Communities in Headwater Streams Affected by Acidic Precipitation in the Central Appalachians

AbstractWe collected quantitative macroinvertebrate samples monthly from September 1989 to October 1990 from four streams on the Allegheny Plateau of West Virginia that were characterized by different bedrock geology and streamwater pH. Mean pH was 4.3, 6.1, 6.0, and 7.5 in the four streams. We compared species and functional group composition of the benthic macroinvertebrate community in these streams to choose taxa that could be used as indicator species for differences in pH in bioassessment studies. The streams differed in species composition and abundance and several species were found that could be used as indicators for each of the levels of pH. Higher densities of Amphinemura sp., Leuctra sp., Euryophella funeralis, and Paracapnia angulata were characteristic of the stream with a pH of 4.3. Higher densities of Peltoperla arcuata and Wormaldia moesta were found in the streams with a pH of about 6.0. Gammarus minus, Baetis sp., Ephemerella dorothea, and Sweltsa sp. were found at higher densities in the stream with a pH of 7.5.

Effects of Whole-Tree Harvest on Epilithic Algal Communities in Headwater Streams

ABSTRACT The effects of whole tree harvest on the stream algal community within the Hubbard Brook Experimental Forest, New Hampshire were studied by comparing harvested streams with reference streams and by experimental manipulations of light, acidity and nitrate levels. The most marked effect was a large increase in algal standing crop in the summer in the streams of the harvested area. Light plays a key role in this increase, but other factors such as pH, nutrients, and water flow are probably also important.

Ecological Interactions Among Predators in Experimental Stream Communities

Field observations on the effect of brook trout on an assemblage (sometimes described as a guild) of predatory salamanders suggest that the interactions among predators in small, headwater streams may be important in determining the structure of this assemblage of predators and thereby, the predation pressure felt by species at lower trophic levels. The interactions among predators and the potential role of those interactions in headwater stream communities was examined in 16 replicated experimental streams. I examined the ecological interactions among four species of co—occurring predators, adult Salvelinus fontinalis (98—122 mm standard length [SL]), larval Gyrinophilus porphyriticus (36—58 mm snout—vent length [SVL]), larval Eurycea bislineata (13—21 mm SVL), and Cambarus bartonii (6—17 mm carapace length [CL]), in an experiment that began in mid—June and ran for 3 mo. Brook trout affected both survival and growth of the larger salamander species, Gyrinophilus, and Salvelinus and Gyrinophilus affected the growth of the smaller salamander Eurycea and the crayfish Cambarus. The presence of Gyrinophilus had no effect on relative condition or fecundity of Salvelinus. Larger predators caused Cambarus and Eurycea to alter their activity levels and habitat, but Gyrinophilus made no adjustments to the presence of Salvelinus. Results demonstrate that Gyrinophilus is vulnerable to predation/aggression from brook trout, but that Eurycea Cambarus are able to behaviorally avoid predation by both large predators at a significant cost to growth. The effect of brook trout on the two species of salamander in the experimental streams parallels the observed differences between salamanders in trout and trout—free waters in the field. Thus, interactions among predators in headwater streams directly and indirectly influence population dynamics of the interacting species by affecting survival, growth, behavior, and habitat use. The interactions among these predators can determine, in part, the predation environment experienced by individuals at lower trophic levels.

Measuring Epilithic Bacterial Production In Streams

Techniques are presented for the measurement of bacterial production (by the rate of 3H-TdR incorporation into DNA), isotope dilution, time course of incorporation of nucleoside, and disturbance artifacts in natural epilithic (on rock) communities of headwater streams. The epilithon in riffles was subsampled by carefully chipping upper rock surfaces. Chips were placed in test tubes and incubated in situ. Test tubes were rotated to reduce the formation of artificial diffusion barriers to TdR transport. DNA was isolated using a double filtration technique. Summertime production had a range of 1.3–51 mg C∙m−2∙h−1 in five southern Ontario streams. Precursors to DNA synthesis, which diluted 3H-TdR, had a range of 63–440 nM. Incorporation of 3H-TdR was linear for at least 1 h. Disturbance artifacts did not appear from rock chipping or from extended sample rotation. The techniques can be applied to other microbial groups from various aquatic hard substrata.

Diel and Seasonal Drift of Zooplankton in a Headwater Stream

Diel periodicity of zooplankton drift was examined in a third order reach of the Illinois River, Arkansas. Quantitative samples were taken every 2 h for a 24-h period during June and January, to determine if zooplankton drifted in greater numbers at night. Significantly more zooplankton (P < 0.05, Wilcoxon) were collected at night during both sampling periods. Day-night densities also were significant for total Copepoda and nauplii in June and January, Euchlanis dilatata in June, and Rotatoria and immature Cladocera (Bosmina and Daphnia) in January. Apparent but nonsignificant differences were observed for Cladocera in June and January, and Rotatoria in June. Maximum densities during June were recorded from 2000-2200 h for all major groups. Maximum rotifer density was strongly influenced by distinct peaks of bdelloids and E. dilatata at 2000 and 2200 h, respectively. January samples were more variable, but maximum densities for Copepoda and total zooplankton were recorded from 2100-0100 h, and Rotatoria from 2300-0100 h. Cladocera maximum densities occurred at 1900 and 0300 h coinciding with distinct peaks for Bosmina longirostris. Drift of Keratella cochlearis, an abundant rotifer, peaked at 2300 h. Greater densities (ca. 7 x) of drifting zooplankton were recorded in January than in June. Diel pulses of drifting zooplankton at night increased the animal component of the seston. Zooplankton may significantly influence the trophic dynamics and activity patterns of filterfeeding macroinvertebrates and planktivorous fish in headwater stream communities. INTRODUCTION Although the literature is seemingly replete with studies of downstream drift by stream invertebrates (e.g., see Waters, 1965, 1972; Elliot, 1967, 1973; Muller, 1974; O'Hop and Wallace, 1983; Allan et al., 1986; and literature cited therein), relatively few have reported occurrence of drifting zooplankton in headwater reaches (but see Williams and Hynes, 1976; Williams, 1977). Yet, zooplankton (defined sensu Pennak, 1966) may play a pivotal role in the trophic dynamics and community structure of stream ecosystems by regulating the flow of essential biochemicals through the food chain. Most stream macroinvertebrates and fish drift downstream at sometime during their life history with distinct diel periodicity with far greater numbers drifting at night (Waters, 1972; Brown and Armstrong, 1985). Although other plausible explanations for the nocturnal drift pattern have been presented (e.g., Wiley and Kohler, 1980, 1984; Allan et al., 1986), some invertebrates and fish may drift downstream as a result of their feeding activities (Ploskey and Brown, 1980; Armstrong and Brown, 1983). Zooplankton in lakes and reservoirs exhibit a similar rhythmic diel activity pattern by migrating nearer the surface at night (Pennak, 1944, 1949; Cushing, 1951; McNaught and Hasler, 1963; George and Fernando, 1969; Short, 1977). Similar vertical migration periodicity has been observed for zooplankton in large rivers (e.g., Volga River; see Hynes, 1970). If zooplankton in headwater streams exhibit the same diel migratory behavior, as suggested by Brown et al. (1989), then I Present address: Department of Biological Sciences, Murray State University, Murray, Kentucky 42071 2 Present address: Department of Wildlife and Fisheries, P.O. Drawer LW, Mississippi State University, Mississippi State, Mississippi 39762

Suppression of Native Fish Populations by Green Sunfish in First-Order Streams of Piedmont North Carolina

Abstract The effects of introduced green sunfish Lepomis cyanellus on native fish communities in headwater streams of North Carolina's Piedmont region were assessed from stream surveys and removal experiments. Green sunfish occurred in most first-order tributaries; when they were present, their abundance and biomass almost always exceeded that of any other coexisting species. Green sunfish also occurred in all second- and third-order streams surveyed, but they never dominated the fish community by numbers or weight in those situations. When green sunfish were removed from three first-order streams, most native species increased in numbers and biomass; in two streams the increase more than made up (within 2 years) the biomass that had been lost by removing green sunfish. These removal experiments indicate that green sunfish suppress native fish populations in Piedmont headwaters. Predation on the young of other species is one likely means by which they do this. Received July 12, 1984 Accepted April 24, 1985