Casey J. Huckins

Effects of six chemical deicers on larval wood frogs (Rana sylvatica)

Widespread and intensive application of road deicers, primarily road salt (NaCl), in North America threatens water quality and the health of freshwater ecosystems. Intensive use of NaCl can be harmful to sensitive members of freshwater ecosystems such as amphibians. Detection of negative effects of NaCl application has prompted the search for alternative chemical deicers with lower environmental impacts. We conducted a series of 96-h acute toxicity tests to determine the negative sensitivity of larval wood frogs (Rana [Lithobates] sylvatica) to six deicing chemicals: urea (CH(4) N(2) O), sodium chloride (NaCl), magnesium chloride (MgCl(2) ), potassium acetate (CH(3) COOK), calcium chloride (CaCl(2) ), and calcium magnesium acetate (C(8) H(12) CaMgO(8) ). Acetates are sometimes touted as environmentally friendly alternatives to NaCl but have not been examined in enough detail to warrant this designation. When exposed to a range of environmentally realistic concentrations of these chemicals, larvae were least sensitive (i.e., had the lowest mortality rate) to CH(4) N(2) O, NaCl, and MgCl(2) and most sensitive to acetates (C(8) H(12) CaMgO(8) , CH(3) COOK) and CaCl(2) . Our observed median lethal concentration estimates (LC50(96-h) ) for NaCl were over two times higher than values presented in previous studies, which suggests variability in tolerance among R. sylvatica populations. The deicers varied greatly in their toxicity, and further research is warranted to examine the differential effects of this suite of deicers on other species.

Ecology and Life History of Coaster Brook Trout and Potential Bottlenecks in Their Rehabilitation

Abstract Lake Superior once supported abundant lake-dwelling brook trout Salvelinus fontinalis called coasters; however, only scattered remnant populations remained by the early 20th century. Owing to their early decline, there is little information about their ecology and life history, yet such information is vital for the ecologically based rehabilitation and management of coasters. This study reviews the ecology of coaster brook trout from a life history perspective and presents quantitative data on the biology and status of the few populations that have been studied. Within the Lake Superior basin, some brook trout are stream residents while others are lacustrine or adfluvial. Although the variation in migratory behavior may be related to individual energetics, the role of evolution and the proximate factors triggering specific life histories remain uncertain. Comparisons of recent biological data from populations in the Lake Superior basin show that the northern populations have longer lengths at age...

RIPARIAN AND UPLAND BREEDING-BIRD ASSEMBLAGES ALONG HEADWATER STREAMS IN MICHIGAN'S UPPER PENINSULA

Abstract Comparative studies of riparian and upland bird communities have focused primarily on larger streams (greater than second order). We examined breeding-bird assemblages in relation to their proximity to small head-water streams in northern hardwood forests of the Otter River watershed in Michigans Upper Peninsula, USA. At 10 study sites, we used fixed-radius point counts to survey bird assemblages and measure forest habitat characteristics along riparian and upland transects. Forest structure and composition differed between riparian and upland areas, with more conifer stems and higher conifer basal area on riparian transects. We detected 46 bird species during 1999 and 2000. During each year, total bird abundance was similar for riparian and upland areas, whereas bird species richness and evenness was higher in riparian areas. When we pooled bird species by foraging guild, we found that foliage-gleaning birds were more abundant in riparian areas. We found 12 bird species exclusively in riparian areas and only 2 species exclusively in the uplands. The northern parula (Parula americana) and Black-burnian warbler (Dendroica fusca) were among 5 species more abundant on riparian transects, whereas the least flycatcher (Empidonax minimus) and red-eyed vireo (Vireo olivaceus) were among 5 species more abundant on upland transects. Although the vegetative gradient between riparian and upland habitat was subtle along these first- and second-order streams, breeding-bird assemblages differed between riparian and upland forests. This suggests that individual bird species respond to vegetative features of even narrow riparian areas. Managers working in northern and mixed-hardwood forests therefore should consider maintaining habitat diversity in the form of native conifers, even on the smallest first-order streams.

Migrations and Biological Characteristics of Adfluvial Coaster Brook Trout in a South Shore Lake Superior Tributary

Abstract We used fish traps and electrofishing surveys to characterize the biology, life history traits, and potential biotic interactors important to the rehabilitation of native, adfluvial coaster brook trout Salvelinus fontinalis in Lake Superior. This study focused on the Salmon Trout River, Michigan, which is the site of the last known remnant population of adfluvial brook trout on the south shore of Lake Superior. The brook trout captured in passive traps (weirs) in the river ranged from 56 to 554 mm in total length (TL) and from 0 (young of the year) to 6 years of age. This population displayed a protracted 5-month migration into the river but one that included relatively few fish. Coaster brook trout in this population appear to initiate adfluvial migrations near age 3 and 300 mm TL. Relative weight values increased with fish length and therefore reproductive life stage, possibly indicating the shift from river to lake habitats. This population of coaster brook trout is small and subject to potent...

Associations among Selection Logging History, Brook Trout, Macroinvertebrates, and Habitat in Northern Michigan Headwater Streams

Abstract Selection logging is a dominant forest management technique in mixed-hardwood forests of the Laurentian Great Lakes region, yet little is known about its potential effects on neighboring streams and their communities. We surveyed nine headwater streams of the Otter River watershed in Michigans Upper Peninsula for which the adjacent forest had undergone selection logging in the previous 2 to 30 years to examine whether the abundance of brook trout Salvelinus fontinalis was related to the logging history, stream habitat conditions, or aquatic macroinvertebrate composition. Mean abundances of age-1 and older brook trout were estimated by electrofishing replicate 100-m sections of each stream in 1999 and 2000. Aquatic macroinvertebrates were surveyed in 1999, and stream habitat was surveyed in 2000. Correlation models showed that brook trout density and biomass were substantially lower in streams bordering more recently logged forests. Brook trout abundance was also positively correlated with the re...

Water resources management in a homogenizing world: Averting the Growth and Underinvestment trajectory

Biotic homogenization, a de facto symptom of a global biodiversity crisis, underscores the urgency of reforming water resources management to focus on the health and viability of ecosystems. Global population and economic growth, coupled with inadequate investment in maintenance of ecological systems, threaten to degrade environmental integrity and ecosystem services that support the global socioeconomic system, indicative of a system governed by the Growth and Underinvestment (G&U) archetype. Water resources management is linked to biotic homogenization and degradation of system integrity through alteration of water systems, ecosystem dynamics, and composition of the biota. Consistent with the G&U archetype, water resources planning primarily treats ecological considerations as exogenous constraints rather than integral, dynamic, and responsive parts of the system. It is essential that the ecological considerations be made objectives of water resources development plans to facilitate the analysis of feedbacks and potential trade-offs between socioeconomic gains and ecological losses. We call for expediting a shift to ecosystem-based management of water resources, which requires a better understanding of the dynamics and links between water resources management actions, ecological side-effects, and associated long-term ramifications for sustainability. To address existing knowledge gaps, models that include dynamics and estimated thresholds for regime shifts or ecosystem degradation need to be developed. Policy levers for implementation of ecosystem-based water resources management include shifting away from growth-oriented supply management, better demand management, increased public awareness, and institutional reform that promotes adaptive and transdisciplinary management approaches.

Estimation of Streambed Groundwater Fluxes Associated with Coaster Brook Trout Spawning Habitat

We hypothesized that the spatial distribution of groundwater inflows through river bottom sediments is a critical factor associated with the distribution of coaster brook trout (a life history variant of Salvelinus fontinalis) spawning redds. An 80-m reach of the Salmon Trout River, in the Huron Mountains of the upper peninsula of Michigan, was selected to test the hypothesis based on long-term documentation of coaster brook trout spawning at this site. A monitoring well system consisting of 22 wells was installed in the riverbed to measure surface and subsurface temperatures over a 13-month period. The array of monitoring wells was positioned to span areas where spawning has and has not been observed. Over 200,000 total temperature measurements were collected from five depths within each monitoring well. Temperatures in the substrate beneath the spawning area were generally less variable than river temperatures, whereas temperatures under the nonspawning area were generally more variable and closely tracked temporal variations in river temperatures. Temperature data were inverted to obtain subsurface groundwater velocities using a numerical approximation of the heat transfer equation. Approximately 45,000 estimates of groundwater velocities were obtained. Estimated groundwater velocities in the spawning area were primarily in the upward direction and were generally greater in magnitude than velocities in the nonspawning area. Both the temperature and velocity results confirm the hypothesis that spawning sites correspond to areas of significant groundwater flux into the river bed.

Spatial Distribution of Riparian Zone Coarse Woody Debris in a Managed Northern Temperate Watershed

ABSTRACT Coarse woody debris is an important structural component of both terrestrial and aquatic ecosystems. We investigated coarse woody debris size-structure, decay class composition and distribution within the interface between second growth mixed conifer-hardwood forests and perennial streams in a catchment of the Lake Superior watershed on the Keweenaw Peninsula, Michigan. Down dead wood accumulation was nonlinearly distributed along transects perpendicular to streams and reached a peak between 30 and 50 m away from the wetted stream channels. Variability in the abundance of standing snags displayed a significant increase with distance. The coarse wood accumulations we observed were consistent with levels reported for upland, second-growth forests and were low compared to old-growth forest remnants in the region. Large (>40 cm diam) down dead wood will probably be the slowest pool to recover from logging and land clearing activities that occurred in the watershed prior to the turn of the 19th Century. Nevertheless, the large woody debris, especially highly-decayed wood, at the sites we examined was relict white pine (Pinus strobus) stumps, a persistent legacy of those same historic anthropogenic disturbances. Unlike dead wood, we detected no similar spatial distributions of living woody biomass. The small diameter of the existing standing wood suggests there will be a lag in the recruitment of new large dead wood into this ecosystem.

Resolving within- and between-population variation in feeding ecology with a biomechanical model

Studies of phenotypic plasticity have emphasized the effect of the environment on the phenotype, but plasticity can also be used as a tool to study the functional significance of key traits. By inducing variation in phenotypes and testing quantitative models that predict performance based on biological mechanisms, we can develop functionally general models of performance. Pumpkinseed sunfish from lakes with high snail availability have large levator posterior muscles (which are used to crush snail shells), whereas fish from lakes with few snails have relatively small muscles. Here we: (1) quantify differences in the feeding ability of an ontogenetic series of pumpkinseed from two populations; and (2) evaluate whether a biomechanical model can resolve the observed ontogenetic and between-population variation in feeding ecology. Mass, but not length, of the levator posterior muscle in fish from Three Lakes (a lake rich in snails) was greater than for comparably sized fish from Wintergreen Lake (a lake with few snails). Handling times were shorter, crushing strengths were 71% greater, and foraging rate (snail tissue mass consumed per time) and the fraction of thick-shelled snails in the diet were approximately 100% greater for fish from Three Lakes compared to comparably sized fish from Wintergreen. These between-lake differences were not significant after adjusting for variation in pharyngeal morphology, suggesting that the biomechanical model of snail crushing resolved observed ontogenetic and population-level variation in the feeding ecology of pumpkinseed.

Applicability and Interpretation of Fish Indices of Biotic Integrity (IBI) for Bioassessment in the Upper Midwest

AbstractMultiple fish-based indices of biotic integrity (IBIs) and biological condition gradient models have been developed and validated to assess ecological integrity in the Laurentian Great Lakes region. We evaluated the applicability and effectiveness of using fish community indices for assessing site integrity in central Great Lakes streams, which have diverse temperature regimes and can be classified as warmwater, coolwater, or coldwater. Sites with different thermal regimes require different assessment tools to ensure comparability. Streams in the Big Manistee River watershed, Michigan, are near thermal thresholds for classification as coolwater or coldwater. We evaluated two coolwater and three coldwater indices developed for Upper Midwest streams. Output from coolwater indices were not correlated with coldwater index outputs and did not discriminate among the stream systems we evaluated. In monitoring temporal patterns over time (2002–2010), we found that coldwater indices showed similar patterns...