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Coastal wetlands are known to be efficient carbon sinks due to high rates of primary productivity, carbon burial by mineral sediments, and low rates of sediment organic matter decomposition. Of the three coastal wetland types: tidal marshes, tidal forests, and seagrass meadows, carbon burial by seagrasses is relatively under-studied, and reported rates range widely from 45 to 190 g C m-2 yr-1. Additionally, most of these seagrass rates are biased toward tropical and subtropical species, particularly Posidonia oceanica, with few focused on Zostera marina, the most widespread species in the northern hemisphere. We measured sediment organic content, carbon content, and long-term accretion rates to estimate organic carbon stocks and sequestration rates for a Z.marina meadow in Padilla Bay, a National Estuarine Research Reserve in Washington. We found rates of carbon sequestration to be quite low relative to commonly reported values, averaging 9 to 11 g C m-2 yr-1. We attribute this to both low sediment organic content and low rates of accretion. We postulate here that Padilla Bay's low carbon sequestration capacity may be representative of healthy Z.marina meadows rather than an anomaly, and that Z.marina meadows have an inherently low carbon sequestration capacity because of the species' low tolerance for suspended sediment (which limits light availability) and sediment organic content (which leads to toxic sulfide levels). Further research should focus on measuring carbon sequestration rates from other Z.marina meadows, particularly from sites that exhibit, a priori, the potential for higher rates of carbon sequestration.
We studied long-term trends in catches per unit effort (CPUE; fish h-1) of four sport fish taxa in the Flathead River, Montana, following changes in hydroelectric operations at the Sliš Ksanka Qisp Project (SKQP; formerly Kerr Dam). Prior to 1997 SKQP operations caused frequent, unnatural flow fluctuations. In 1997 the dam was changed from a power-peaking and load-following facility to a base-load facility. The new operations included seasonal minimum flows and ramping rates that greatly reduced flow fluctuations. Autumn trends in CPUEs of two size classes (substock and stock) of northern pike (Esox lucius), Oncorhynchus spp., brown trout (Salmo trutta), and smallmouth bass (Micropterus dolomieu) were monitored using nighttime electrofishing during 1984–86 before operational changes and again at the onset of operational changes in 1998 and continuing through 2008. We observed little difference in CPUEs between 1984–86 and 1998, the first year after changes, but we documented strong increasing trends in CPUEs of both sizes of all taxa, except stock northern pike, over the long term following operational changes. We also examined long-term patterns in the size structure (total length; TL mm) of fishes following operational changes. All taxa had either initial downward shifts in median TL, decreases in minimum sizes of fish captured, or both, a pattern consistent with enhanced recruitment and survival of smaller fishes. We conclude that modifications in dam operations were associated with increases of four sport fish taxa in the Flathead River and that similar normative flow applications might benefit riverine fish populations elsewhere.
Ecosystem modification driven by anthropogenic land-use and land-cover change is one of the leading drivers of global biodiversity declines. Simultaneously, ongoing climate change is modifying ecosystems and will have far-reaching impacts on the structure and function of ecological communities. Rising surface temperatures are predicted to have negative effects on plants and animals, but such predictions are typically broad and poorly matched to the spatial scale at which most organisms experience the environment. Microclimate thermal regimes are often moderated by land-cover, and intensive forest management practices have the potential to either ameliorate or exacerbate climate change effects on biota. In this study, we examined the degree to which air temperature varied across an experimental gradient of herbicide application intensity within early-seral forests in the Coast Range mountains of western Oregon. We evaluated stand-level air temperatures in regenerating stands subjected to light, moderate, and intensive herbicide treatments, as well as a no-spray control. We examined whether daily temperature measurements (minimum, mean, and maximum) and their associated coefficients of variation were influenced by herbicide treatments. We found that herbicide treatments had some influence on mean and maximum air temperatures, but not on minimum temperature or on measures of temperature variability. However, temperature effects were small (< 0.5 °C), the direction of these effects were inconsistent, and pairwise contrasts often failed to detect significant differences after accounting for multiple comparisons. Our results suggest that post-harvest vegetation management has limited impacts on fine-scale air temperatures and is unlikely to either amplify or buffer the projected effects of climate change within early-seral forests.
Native bees are declining worldwide, but conserving or restoring their habitat requires a better understanding of bee-flower associations. High quality bee habitat includes flowers that provide pollen and nectar preferred by bees. However, little data exist about which plants are commonly used by bees in the Pacific Northwest, or whether bees prefer certain plant characteristics over others. We examined bee and plant communities in an Oregon riparian ecosystem. Our purpose was to describe bee-plant associations, determine which plants are most frequently visited by bees, identify plants that may be preferred by bees, and examine how a plant's native status, flower color, and floral morphology affect the types of bees visiting it. We found that many blooming plants received a diverse set of bee visitors, but some plants had a higher number and species richness of visiting bees than others. No plant species seemed limited to visitation by a small set of specialist bees. The number and type of visiting bees were not influenced by the plant's native status. However, flower morphology (but not color) significantly affected types of bees visiting plants. Bilaterally symmetrical and medium tubular flowers, with nectar and pollen typically more difficult to reach, were associated with larger bees with longer tongues, while smaller, easily accessible flowers attracted smaller bees with shorter tongues. Our results suggest that certain plants are particularly useful for supporting abundant and diverse bee communities, and increasing diversity in the morphology of blooming plants is a key factor to consider when restoring riparian areas for bee pollinators.
Resource managers have been attempting to recover the kokanee (Oncorhynchus nerka) population in Lake Pend Oreille, Idaho for more than three decades using an annual stocking program and an experimental water-level management strategy. This study evaluated the effect of both management actions on kokanee recruitment. A bootstrap-based generalized Ricker model was used to test if wild kokanee recruitment was significantly influenced by water-level management, while accounting for error due to sampling variability and differential survival of wild- and hatchery-origin fish within age-classes. Wild kokanee exhibited a compensatory stock-recruitment relationship, whereas hatchery recruitment was positively and linearly related to stocking. The model did not identify a significant relationship between water level and wild kokanee recruitment. Density dependence and variable stocking appeared to explain the synchronized and cyclic recruitment of wild and hatchery fry.
The smallmouth bass (Micropterus dolomieu) is a cool-water fish species native to central North America. Widespread introductions and secondary spread outside of its historical range have led to new recreational fisheries and associated economic benefits in western United States, but have also resulted in a number of ecological impacts to recipient ecosystems, including threats to Pacific salmon. Management of introduced smallmouth bass populations, now and into the future, relies on accurate detection and monitoring of this species. To address this need, we developed an environmental DNA assay that can detect smallmouth bass DNA extracted from filtered water samples in concentrations as low as 2 mtDNA copies per reaction. Field testing demonstrated that eDNA sampling produced results largely consistent with snorkel surveys, a traditional visual assessment, and gained a few additional positive detections. While this assay is robust against non-target detection, including the only other Micropterus in Pacific Northwest streams, largemouth bass (M. salmoides), the high genetic similarity within the sunfish family Centrarchidae made it unable to distinguish smallmouth bass from spotted bass (M. punctulatus) and some Guadalupe bass (M. treculii). The high sensitivity of this method and assay will be particularly useful for identifying the location of non-native smallmouth bass in the Pacific Northwest, quantifying its rate of spread, and aiding management actions.
Bats are being impacted by many threats (e.g., human disturbance of maternity roost sites and white-nose syndrome). Bat maternity roosts are a limited resource, and bats exhibit strong fidelity to these sites; therefore, identifying these features and conserving the surrounding habitat are important for bat management. Southern Idaho consists of the largest, contiguous volcanic pseudokarst area in the U.S., which provides important cave habitat for bats, but little is known about bat maternity roosts in this area. We compiled data spanning 36 years in southern Idaho to identify caves used by maternity colonies. From June 1980 to August 2016, researchers surveyed 313 caves. We documented 11 caves used by maternity colonies of Townsend's big-eared bats (Corynorhinus townsendii), and 10 caves that were potentially used by maternity colonies. In the 11 caves used as maternity roosts, the median number of Townsend's big-eared bats was 38, and the mean number was 49 individuals (SD = 47.1, range = 8 to 160 bats). Our data highlight southern Idaho as an important maternity roosting area for bats in Idaho and western North America, and provide baseline information of maternity caves prior to the arrival of white-nose syndrome, which can help managers during land-use planning in this area.