Restoration and Urban Ecology Posters
Presiding: E Marti, Centre d'Estudis Avancats de Blanes (CSIC); C Hoagstrom, South Dakota State University
NB33K-01 1330h
Macroinvertebrate Communities in Restored and Natural Slough Wetlands: Evaluation of Restoration Practices in the Central Platte River Valley.
Wetlands in the central Platte River basin of Nebraska provide numerous ecosystem services, but these systems have been degraded through drainage for agriculture and increasing river regulation. Restoration is currently a common means of increasing wetland area in this region, but little is known about the success of these restorations. We quantified macroinvertebrate abundance, biomass, and community structure in restored wetlands ranging in age from 5-11yrs old and compared them with proximal natural systems to assess success. Analyses of seasonal samples showed that total macroinvertebrate abundance, biomass, richness, and diversity were similar between restored and natural wetlands. However, biomass values reflected some differences in community and functional structure. Whereas insects constituted most biomass in natural systems (55%), mollusks, mostly Physella and Fossaria, dominated biomass (61%) in restorations. In natural wetlands, collector-gatherers and predators contributed most to mean biomass (~29% each), followed by a relatively even distribution of herbivores, collector-filterers, and scrapers. In contrast, collector-gatherers contributed most to mean biomass in restored wetlands (47%), followed by scrapers (43%) and predators (13%). Although total values and most abundance-based metrics suggested that macroinvertebrate communities had recovered in restored wetlands, biomass patterns indicate that recovery of communities and function is not complete.
NB33K-02 1330h
Effects of Channel and Riparian Zone Rehabilitation on Invertebrate Taxa Richness and Diversity in a Mississippi Hill Land Stream
Invertebrate community and physical habitat information was recorded 1 year before, after 2 years, and 10 years after rehabilitation of an incised, degraded stream, and compared to a nearby similar non-rehabilitated stream. A one-kilometer reach of Goodwin Creek, located in the loess hills of north central Mississippi, was modified with small weirs and spur dikes of quarried limestone (D50=20cm) to stabilize stream banks/bed, increase water depth and produce riffle-run-pool sequences. Sand banks were stabilized with black willow. The non-rehabilitated stream lacked adequate bed controls and flow dampening structure, and thus remained shallow with a frequently vacillating sand bed that was regularly scoured by runoff. Ten years after rehabilitation, base flow average water width and aquatic habitat volume in Goodwin Creek were, respectively, 86% and 118% greater than at the untreated creek, and average depth in Goodwin was 36 cm, but only 19 cm in the untreated creek. While invertebrate communities in the two creeks were very similar before rehabilitation, both Morisita-Horn and Bray-Curtis community similarity indices indicated moderate differences 2 years after treatment and high dissimilarity after 10 years. A suite of seven species richness estimators and three common diversity indices were all much higher for Goodwin Creek after rehabilitation.
NB33K-03 1330h
Can We Restore Periphyton Assemblages Using Coarse Woody Debris Additions in Disturbed Streams?
We examined response of periphyton and diatom assemblages to experimental debris dam additions (restoration) within disturbed coastal plains streams at Fort Benning, GA. Prior to restoration, we quantified periphyton and physicochemical variables for 1 y from sand (episammic) habitats in 10 streams that varied in degree of disturbance from land management and military training. In November 2003, we added large woody debris dams (10/stream, 120-m reach) to 4 disturbed streams (=restored streams) and left 4 disturbed streams unrestored (=controls), and quantified periphyton and diatom variables for 1 y. Increases in periphyton biomass (as chlorophyll a) in restored streams were higher than in unrestored streams during the first 3 to 6 mo after restoration (p=0.05), although biomass differences were not significant by 9 to 12 mo. Unlike periphyton biomass, diatom assemblages did not immediately respond to restoration; however the proportion of cells in the genus Eunotia, which composes >90% of episammic assemblages in low-disturbance streams, significantly increased in 2 of the 4 restored streams after 9 mo. These data suggest that debris dam additions may benefit periphyton in disturbed coastal plains streams, possibly by increasing bed stability, although the timing, duration, and consistency of such positive effects may be limited.
NB33K-04 1330h
Developing Reference Conditions and Biological Indicators for Urban Streams
There are two objectives of this project: 1) developing biological indicators that characterize urban stressors, and 2) establishing reference conditions for urban systems. Our dataset was assembled from multiple, routine biological monitoring programs in Baltimore, MD/Washington, DC, Cleveland, OH, and San Jose, CA, representing data from approximately 2500 stream sites. We propose that increased sensitivity of biological indicators in urban systems can be attained only with detailed description of stressor conditions. A stressor gradient composed of multiple abiotic parameters representing landscape and instream physical, chemical, and hydrologic conditions was assembled. An ArcView and Excel-driven hydrologic model was developed that produced site-specific daily flow data which were reduced to hydrologic indicator values. These indicators showed significant correlations with urban land use (e.g., flood frequency [R2=0.36], flashiness [R2=0.37]) and were a substantial component of the gradient. Biological indicators were selected based on their responsiveness to the stressor gradient. In urban systems, restoration to pristine conditions is impossible; therefore, we developed reference conditions that represented "best attainable" conditions, given the extent of urbanization. This approach should provide an understanding of the capacity for ecological restoration in urban systems, and a basis for adaptation of urban streams to a tiered aquatic life use framework.
NB33K-05 1330h
The San Marcos River Habitat Conservation Plan: Using HCP's as a Tool for Ecological Restoration
The San Marcos River in San Marcos, Hays County, Texas is a biologically unique system with several listed species found in the headwaters. Flowing from the Edwards Aquifer and the second largest spring system in Texas, the water is clear and thermally constant. The physical and biological character of the habitat within and surrounding the river has been severely degraded by human activity. As a means of dealing with the continued disturbance and finding a balance between human needs and conservation, the San Marcos River Habitat Conservation Plan was written as provided by Section 10(a) of the Endangered Species Act. The plan provides habitat mitigation for the fountain darter (Etheostoma fonticola), Comal Springs riffle beetle, (Heterelmis comalensis), and San Marcos salamander (Eurycea nana), while allowing for incidental take resulting from specific restoration and management projects. We used a science-based ecological/experimental approach to address some of the problems and optimize solutions, including restoration of stream banks damaged from overuse, planning for permanent access points and trails, removal of silt deposits caused by extensive flood control structures, wet-pond construction, managing flow, and the control of submerged and emergent non-native vegetation to improve habitat and enhance recreation.
NB33K-06 1330h
Recovery of Three Arctic Stream Reaches From Experimental Nutrient Enrichment.
We examined multi-year patterns in community recovery from experimental low-concentration nutrient (N+P and P only) enrichment in three reaches of two Arctic tundra streams (Kuparuk River and Oksrukuyik Creek) on the North Slope of Alaska (USA). Rates of recovery varied among community components and depended on duration of enrichment (2 to 13 consecutive growing seasons). Biomass and C:P ratio of epilithic algae returned to reference levels rapidly (within 2 years), regardless of enrichment duration. Bryophyte cover, which increased greatly after long-term enrichment (>8 years), recovered to reference levels only after 7 years, when a storm scoured most remnant moss in the recovering reach. Persistence of bryophytes slowed recovery rates of insect taxa that had either been positively (e.g., Ephemerella, most chironomid taxa) or negatively (e.g., Orthocladius rivulorum) affected by this shift in dominant primary producer and its consequence for benthic habitat. Growth of Arctic grayling (adults and young-of-year), the top predator, returned to reference rates within two years. Recovery of these Arctic stream ecosystems from nutrient enrichment was consequently controlled largely by interactions between duration of enrichment and physical disturbance, mediated through physical habitat shifts caused by bryophytes.
NB33K-07 1330h
Carbon Limited Heterotrophic Activity in an Urban Stream
Urban streams are characterized by flashy hydrographs, heavily incised channels, and scoured bed materials. Because of frequent scour, benthic organic matter in urban streams tends to be extremely low relative to nonurban streams. Recent research has related low organic matter availability to low rates of nitrogen uptake. We hypothesized that urban streams are carbon limited, and tested this hypothesis by adding a pulse of labile carbon (as potassium acetate) to the Stewart April tributary of Paint Branch, which drains a heavily urbanized watershed 73% impervious cover) in the suburbs of Washington, D.C. We predicted that the magnitude of the carbon effect on stream metabolism and N processing would be reduced as a result of litter inputs, and compared the stream response before and after peak litterfall. Adding labile dissolved organic carbon to the stream immediately increased metabolism in the stream channel during both additions, but this increase in heterotrophic activity did not lead to reductions in dissolved inorganic nitrogen concentrations. This indicates that while heterotrophs in this stream are carbon limited, the microbial community was not able to respond quickly enough to the pulse addition to appreciably reduce DIN concentrations in this eutrophic stream.
NB33K-08 1330h
Fisheries Assemblages and Road Stream Crossing Improvements on Manistee River Tributaries, Manistee County, Michigan
Sedimentation affects both stream physical and biological integrity. Our objective was to incorporate the small-scale, proximate effects of sediment restoration and the larger-scale, ultimate effects that can occur from headwaters to mouth before and after restoration efforts. Electrofishing was conducted during Spring and Fall 2004. A total of 29 electrofishing reaches comprised the longitudinal gradient analysis along with 5 construction sites. Species richness ranged from 15 in Bear Creek (3rd order) to 8.1 in Sickle (1st). Pine Creek (2nd) was intermediate (9.3). Shannon's diversity index ranged from 0.78 in Bear to 0.61 and 0.51 in Pine and Sickle Creeks, respectively. Simpson's dominance index ranged from 0.46 in Sickle, where mottled sculpin were dominant, to 0.35 in Pine and 0.27 in Bear. Of the salmonids, relative abundance (%) of brook trout was highest in Sickle (2.31); brown trout were most abundant in Pine (7.58), and rainbow trout were most abundant in Bear (8.77). Initial results suggest that recovery should be most rapid in the more diverse and larger Bear Creek and that the restoration of a perched culvert in Sickle Creek could cause a decline in the native brook trout when brown trout are able to move upstream.
NB33K-09 1330h
Effectiveness of Road-Stream Crossing Improvements and Bank Stabilization in the Manistee River Watershed, MI: Response of the Benthic Macroinvertebrates
The Manistee River Watershed is a unique resource used by many individuals including the Little River Band of Ottawa Indians (LRBOI). However, the presence of excessive sediment from continued erosion of stream banks and poorly designed road-stream crossings threaten habitat quality. The U.S. EPA has recently awarded a grant to the LRBOI to improve road-stream crossings and stabilize stream banks. Our objective is to determine how these improvements affect the physical habitat of the stream and the response of macroinvertebrate assemblages. Initial results from a subset of 10 sites indicate that immediately below a restoration site, there was a decline in abundance and family richness post-restoration. Likely this was due to construction-related deposition of sand, which particularly impacted the Diptera (Simuliidae spp. and Chironomidae spp.). In contrast, fall sampling of sites further from the construction zone exhibited an increase in benthic abundance (from 204 to 816 individuals/m2). The extent to which the construction-generated sand will have impacted reaches further from the restoration site are continuing to be monitored. Although the short-term effects appear to be negative, we believe the ongoing monitoring will document an eventual improvement in the macroinvertebrate community and in overall stream ecosystem integrity.