Northwest Science - Accepted Articles and Notes
Northwest Science 98(2)
Intertidal and subtidal marine succession rates on new rock armor in Chiniak Bay, Kodiak, Alaska - E. Leyla Arsan, Tom Lance, Kelly Krueger, Rebecca Shaftel
Alaska has 33,904 miles of coastline and most coastal infrastructure in the state is armored for erosion protection, yet little is known about colonization or recolonization rates post-disturbance in high northern latitudes. This study quantifies the recruitment and colonization of new armor rock at the Kodiak Airport and documents algal and sessile invertebrate species abundance and assemblage (percent cover) at the airport and at reference sites with similar substrates, salinity, wave exposure, and depth. Over four years of annual intertidal and subtidal monitoring, average percent cover by algae and invertebrates at study sites ranged from 13 % to 100 %. Study sites showed extensive cover by early colonizing algae and invertebrates in both the intertidal and subtidal at 15 months post-construction silt curtain removal (Year 1). Prominent biobanks of monospecies (e.g., bay mussels [Mytilus trossulus]) observed in Year 1 largely changed to barnacles (Balanus sp.) and algal species by Year 4. Both algal cover and number of species increased over time at study sites; total cover and number of species were similar to reference sites by Year 4. The colonization rate of rock armor and the successional timeframe to develop full ecological functions are important because of the potential effects of rock armor on aquatic habitats, at both local and landscape scales. This study illustrates that colonization of new armor rock in southcentral Alaska can be rapid (can average 80.8% cover of intertidal and subtidal substrates after 1 year) and that interannual variability of species abundance may occur throughout the successional cycle.
The complete pre-print version of this article is available here.
Food habits of nonnative Smallmouth Bass in Coeur d’Alene Lake, Idaho - Michael C. Quist, John D. Walrath, Jon A. Firehammer
Smallmouth Bass, Micropterus dolomieu, has been widely introduced beyond its native distribution where interactions with other organisms are largely unknown. We examined the food habits of Smallmouth Bass in Coeur d’Alene Lake, Idaho. Smallmouth Bass were sampled monthly from March 2012 to May 2013 using short-duration (1–2 hr sets) gill netting and electrofishing. In total, food habits were evaluated from 904 Smallmouth Bass varying in total length from 39–492 mm using gastric lavage. Diet composition varied by season and age. Smallmouth Bass less than 100 mm had diets dominated by invertebrates, particularly Ephemeroptera, Odonata, and Diptera. Fishes were increasingly important in the diet of Smallmouth Bass longer than 100 mm. Interestingly, crayfish (Decapoda) were virtually absent in Smallmouth Bass stomachs; only eight Smallmouth Bass had crayfish in their diet. Native vertebrates were also rare in Smallmouth Bass diets. Rather, kokanee, Oncorhynchus nerka, a nonnative species, was generally the most commonly consumed fish prey item (present in 5-15 % across seasons). Kokanee contributed the highest percentage of total energy (~45 % of all energy) of any prey item. Results of this study suggest that native fishes of conservation concern are a minor component of Smallmouth Bass diets and that kokanee is important in meeting the energy demands of nonnative Smallmouth Bass. Further research on the distribution and abundance of crayfish in the system and on the population-level effects of Smallmouth Bass predation on kokanee would be insightful and help guide management actions in Coeur d’Alene Lake and similar systems in western North America.
Physical and biological factors constraining the growth and persistence of a Pacific Northwest fringing eelgrass bed - David L. Cowles, M. Justin Hylarides, Erica Franklin
In this study we examined a small, fringing Zostera marina eelgrass bed in Rosario Bay, WA to determine the factors limiting its growth and persistence. The bed is less than 1 ha and entirely subtidal, with around two meters depth difference between the shallow and deep margins of the bed. Substrate within and seaward of the bed is silty sand, while shoreward and to the north are gravel and rocks. The bay is periodically exposed to heavy wave action which causes disturbance down to eelgrass depth, and light attenuation and large tidal changes limit light levels. Nevertheless, light usually reaches saturation levels for a limited time in all seasons. Sediment nutrient and organic content seem adequate for eelgrass growth within the beds, but not in the gravels on the shoreward side. Lack of adequate light is the most likely limiting factor along the deeper edge of the bed, sediment disturbance by waves along the shoreward margin, and incompatible substrate plus competition with macroalgae along the northern margin. The shallowest depth imposed by wave turbulence appears to be close to the deepest depth imposed by light limitation, so maintenance of low light attenuation in the water column appears to be one of the most important factors contributing to the persistence of this bed. In addition, a previously unreported amensal interaction with anchored but motile Nereocystis kelp may create patches of damage throughout the bed during storms.
A characterization of hyporheic temperatures with applications for salmon habitat restoration in a thermally impaired river - Sydney Jantsch, James M. Helfield, Leo Bodensteiner, Kathryn L. Sobocinski, Andrew G. Bunn
Elevated stream temperatures represent an important stress affecting Pacific salmon (Oncorhynchus spp.). In thermally-impaired streams, upwellings of shallow subsurface (i.e., hyporheic) water have the potential to create patches of cool-water refuge that allow salmon to persist in otherwise unsuitable water temperatures. Since patterns of hyporheic upwelling are influenced by variations in streambed topography, habitat restoration actions such as engineered log jam construction may be used to preserve or promote upwellings. This strategy requires that hyporheic flows remain cooler in summer, relative to the overlying surface stream, but this might not always be the case. Here we characterize the relationship between hyporheic and overlying surface temperatures during a summer low-flow season in a restored reach of the South Fork Nooksack River. Among six sampling sites, we found that one had hyporheic temperatures that were consistently colder than the overlying surface stream, two had hyporheic temperatures that were variable but more moderate than those of the overlying surface stream, and three had hyporheic temperatures that were not cooler or more stable than those of the overlying surface stream. Habitat mapping suggests that thermally stable hyporheic flow paths may be associated with specific combinations of channel geomorphic units, which influence flow path length, depth and discharge. These findings may be used to identify potential areas of cool-water refuge and guide the design and placement of habitat restoration actions to promote climate adaptation for salmon populations in thermally-impaired streams.
The complete pre-print version of this article is available here.