Coastal British Columbia Research Articles

Archaeological and Contemporary Evidence Indicates Low Sea Otter Prevalence on the Pacific Northwest Coast During the Late Holocene

The historic extirpation and subsequent recovery of sea otters (Enhydra lutris) have profoundly changed coastal social-ecological systems across the northeastern Pacific. Today, the conservation status of sea otters is informed by estimates of population carrying capacity or growth rates independent of human impacts. However, archaeological and ethnographic evidence suggests that for millennia, complex hunting and management protocols by Indigenous communities limited sea otter abundance near human settlements to reduce the negative impacts of this keystone predator on shared shellfish prey. To assess relative sea otter prevalence in the Holocene, we compared the size structure of ancient California mussels (Mytilus californianus) from six archaeological sites in two regions on the Pacific Northwest Coast, to modern California mussels at locations with and without sea otters. We also quantified modern mussel size distributions from eight locations on the Central Coast of British Columbia, Canada, varying in sea otter occupation time. Comparisons of mussel size spectra revealed that ancient mussel size distributions are consistently more similar to modern size distributions at locations with a prolonged absence of sea otters. This indicates that late Holocene sea otters were maintained well below carrying capacity near human settlements as a result of human intervention. These findings illuminate the conditions under which sea otters and humans persisted over millennia prior to the Pacific maritime fur trade and raise important questions about contemporary conservation objectives for an iconic marine mammal and the social-ecological system in which it is embedded.

New and interesting seaweed records from the Hakai area of the central coast of British Columbia, Canada: Chlorophyta

Abstract Since 2011 we have been documenting seaweed diversity and abundance along a poorly studied area of the central coast of British Columbia, Canada. This first installment focuses on the Chlorophyta. To date, 42 species have been recorded, and we have obtained DNA sequences for most. Although most of these species reportedly have wide distributions along the west coast of North America, others appear to represent new northern or southern records or possible introductions, and a number have yet to be described. New southern limits are recorded for Acrosiphonia sonderi, Acrosiphonia sp., Protomonostroma undulatum, and Ulva pouliotii sp. nov., and new northern records are documented for Ulva expansa, U. stenophylla, and another undescribed species of Ulva. Among species of Cladophoraceae, we obtained a sequence only for Cladophora opaca, a Japanese species not previously recorded from North America, and an undetermined species of Rhizoclonium. We sequenced three species of Derbesia, none of which is D. marina, the currently recognized species for this area; all three require taxonomic treatment. A sequence for a shell-boring species, which is tentatively identified as Eugomontia sacculata, was also obtained. These findings extend our understanding of the diversity and biogeography of green macroalgae in the northeast Pacific.

An Earthquake Early Warning System for Southwestern British Columbia

Southwestern British Columbia (BC) is exposed to the highest seismic hazard in Canada. Ocean Networks Canada (ONC) has developed an Earthquake Early Warning (EEW) system for the region. The system successfully utilizes offshore cabled seismic instruments in addition to land-based seismic sensors and integrates displacement data from Global Navigation Satellite Systems (GNSS). The seismic and geodetic data are processed in real-time onsite at 40 different stations along the coast of BC. The processing utilizes P-wave and S-wave detection algorithms for epicentre calculations as well as incorporation of geodetic and seismic displacement data into a Kalman filter to provide magnitude estimates. The system is currently in its commissioning phase and has successfully detected over 60 earthquakes since being deployed in October 2018. To increase the coverage of the EEW system, we are in the process of incorporating detection parameters from neighbouring networks (e.g., the Pacific Northwest Seismic Network (PNSN)) to provide additional information for future event notifications.

Salmon subsidies predict territory size and habitat selection of an avian insectivore.

The annual migration and spawning event of Pacific salmon (Oncorhynchus spp.) can lead to cross-boundary delivery of marine-derived nutrients from their carcasses into adjacent terrestrial ecosystems. The densities of some passerine species, including Pacific wrens (Troglodytes pacificus), have been shown to be positively correlated with salmon abundance along streams in Alaska and British Columbia, but mechanisms maintaining these densities remain poorly understood. Riparian areas near salmon streams could provide higher quality habitat for birds through greater food availability and more suitable vegetation structure for foraging and breeding, resulting in wrens maintaining smaller territories. We examined relationships between salmon biomass and Pacific wren territory size, competition, and habitat selection along 11 streams on the coast of British Columbia, Canada. We show that male wren densities increase and territory sizes decrease as salmon-spawning biomass increases. Higher densities result in higher rates of competition as male wrens countersing more frequently to defend their territories along streams with more salmon. Wrens were also more selective of the habitats they defended along streams with higher salmon biomass; they were 68% less likely to select low-quality habitat on streams with salmon compared with 46% less likely at streams without salmon. This suggests a potential trade-off between available high-quality habitat and the cost of competition that structures habitat selection. Thus, the marine-nutrient subsidies provided by salmon carcasses to forests lead to higher densities of wrens while shifting the economics of territorial defence toward smaller territories being defended more vigorously in higher quality habitats.

Chemical identification of microplastics ingested by Red Phalaropes (Phalaropus fulicarius) using Fourier Transform Infrared spectroscopy

Chemical characterization of plastics ingested by wildlife helps identify sources of plastic pollution in nature and informs assessments of exposure risk to contaminants. In 2016, Red Phalaropes (Phalaropus fulicarius) were found dead on the north coast of British Columbia, Canada, during their southward migration. Previously, ingested particles suspected to be plastics were reported upon gut examination in all carcasses collected, which likely contributed to mortality. Here, we provide chemical identification of the ingested particles using Fourier Transform Infrared (FTIR) spectroscopy. Polymer identification was successful for 41 of the 52 analysed particles (79%): 41 (79%) were confirmed as plastics, 6 (11%) were not plastics, and 5 (10%) could not be identified. The most commonly ingested plastics were polyethylene (42%) and polypropylene (23%), both of which are known to float in the marine environment. Our study highlights the vulnerability of surface foraging seabirds to plastic pollution in the marine environment.

Exploring GPS Observations of Postseismic Deformation Following the 2012 MW7.8 Haida Gwaii and 2013 MW7.5 Craig, Alaska Earthquakes: Implications for Viscoelastic Earth Structure

AbstractThe Queen Charlotte‐Fairweather Fault (QC‐FF) system off the coast of British Columbia and southeast Alaska is a highly active dextral strike‐slip plate boundary that accommodates ∼50 mm/yr of relative motion between the Pacific and North America plates. Nine MW ≥ 6.7 earthquakes have occurred along the QC‐FF system since 1910, including a MS(G‐R)8.1 event in 1949. Two recent earthquakes, the October 28, 2012 Haida Gwaii (MW7.8) and January 5, 2013 Craig, Alaska (MW7.5) events, produced postseismic transient deformation that was recorded in the motions of 25 nearby continuous Global Positioning System (cGPS) stations. Here, we use 5+ yr of cGPS measurements to characterize the underlying mechanisms of postseismic deformation and to constrain the viscosity structure of the upper mantle surrounding the QC‐FF. We construct forward models of viscoelastic deformation driven by coseismic stress changes from these two earthquakes and explore a large set of laterally heterogeneous viscosity structures that incorporate a relatively weak back‐arc domain; we then evaluate each model based on its fit to the postseismic signals in our cGPS data. In determining best‐fit model structures, we additionally incorporate the effects of afterslip following the 2012 event. Our results indicate the occurrence of a combination of temporally decaying afterslip and vigorous viscoelastic relaxation of the mantle asthenosphere. In addition, our best‐fit viscosity structure (transient viscosity of 1.4–2.0 × 1018 Pa s; steady‐state viscosity of 1019 Pa s) is consistent with the range of upper mantle viscosities determined in previous studies of glacial isostatic rebound and postseismic deformation.

Pedological trends and implications for forest productivity in a Holocene soil chronosequence, Calvert Island, British Columbia, Canada

Chronosequence studies of soil formation and ecosystem development provide important insights into the pathways and rates of change occurring on centennial and millennial time scales. In cool or temperate humid environments, Podzols are the predominant soil type formed under coniferous forests in coarse-textured parent material and have been a major focus of chronosequence studies. This study examined the rate and mechanisms of Podzol development and related forest productivity in a sand dune chronosequence in a hypermaritime climate in coastal British Columbia (BC). The sequence spans 10 760 ± 864 yr over eight sites and is the first documented chronosequence in coastal BC to span most of the Holocene Epoch. Soil samples from each genetic horizon were analyzed for bulk density, pH and concentrations of total carbon (C), pyrophosphate- and oxalate-extractable aluminum (Al) and iron (Fe), and total elements. Within ∼3500 yr, a mature Podzol had formed, with cemented horizons (ortstein and placic) present. Organo-metallic complexation appeared to be the dominant mechanism involved in podzolization. Despite a mild, moist climate conducive to chemical weathering, all soils had similarly low values for the chemical index of alteration, suggesting that congruent dissolution of primary minerals may be occurring. Ecosystem retrogression is apparent in the latter stages of the chronosequence — a phenomenon not previously documented in coastal BC. Further research is needed to examine the interactions of nutrient limitation, soil physical barriers, and other possible drivers of ecosystem retrogression.

In situ microcosms deployed at the coast of British Columbia (Canada) to study dilbit weathering and associated microbial communities under marine conditions.

ABSTRACTDouglas Channel and the adjacent Hecate Strait (British Columbia, Canada) are part of a proposed route to ship diluted bitumen (dilbit). This study presents how two types of dilbit naturally degrade in this environment by using an in situ microcosm design based on dilbit-coated beads. We show that dilbit-associated n-alkanes were microbially biodegraded with estimated half-lives of 57–69 days. n-Alkanes appeared to be primarily degraded using the aerobic alkB, ladA and CYP153 pathways. The loss of dilbit polycyclic aromatic hydrocarbons (PAHs) was slower than of n-alkanes, with half-lives of 89–439 days. A biodegradation of PAHs could not be conclusively determined, although a significant enrichment of the phnAc gene (a marker for aerobic PAH biodegradation) was observed. PAH degradation appeared to be slower in Hecate Strait than in Douglas Channel. Microcosm-associated microbial communities were shaped by the presence of dilbit, deployment location and incubation time but not by dilbit type. Metagenome-assembled genomes of putative dilbit-degraders were obtained and could be divided into populations of early, late and continuous degraders. The majority of the identified MAGs could be assigned to the orders Flavobacteriales, Methylococcales, Pseudomonadales and Rhodobacterales. A high proportion of the MAGs represent currently unknown lineages or lineages with currently no cultured representative.

Season‐specific survival rates and densities of coastal cutthroat trout across stream sizes in southwestern British Columbia

AbstractVariation in seasonal survival rates, densities and growth rates of coastal cutthroat trout (Oncorhynchus clarkii clarkii) were assessed across a size gradient of small, forested streams in the Pacific Northwest. We used a robust, mark‐recapture study, stratified seasonally to estimate monthly survival rates of trout in coastal British Columbia (not including young‐of‐the‐year). Survival estimates showed that the summer season had the lowest monthly survival rates (0.907) across all streams in our study (0.927 remainder of year). Within the size range of the seven small streams studied, low‐flow habitat availability (defined by residual pool depth in summer) was the best predictor of mean monthly survival rates, supporting the hypothesis that trout survival increases with the quantity of aquatic habitat, particularly depths of residual pools. In addition, there was an asymptotic relation between water depth and survival rates, where beyond ~20 cm of residual pool depth, greater depth did not confer greater rates of trout survival. Growth rates in all but the largest stream were also lowest during summer. While densities tended to be higher in streams with greater residual depth, this was not significant. Body mass in a given season was a good predictor of survival to the next sampling period. The distribution and success of resident cutthroat trout populations in small streams appear to be constrained by summer low‐flow periods and specific geomorphologies that support deeper pools.

Black bear colour polymorphism through a fragmented Snell’s window

Abstract The white colour morph of the black bear (Ursus americanus kermodei) occurring on islands on the coast of British Columbia, western Canada, captures more salmon (Oncorhynchus spp.) than does the black morph and is hypothesized to have reduced contrast against the sky from the visual perspective of the salmon. We tested this hypothesis in a natural salmon stream by recording the number and proximity of chum salmon (Oncorhynchus keta) approaches (N = 1617 fish, 91 trials) towards life-size bear models differing in body and leg coloration under a mixed forest-sky canopy. Although salmon approached the white models at a much higher rate than black models, consistent with camouflage, we found greater abrupt evasions to the black models, largely independent of their contrast against the above-surface or below-surface backgrounds. Upward-facing sub-surface video-imaging through the rippled water-air interface indicated major visual fragmentation of the model’s integrity. We suggest that increased evasiveness to black models reflects an evolutionary response due to 3+ million years of trophic interaction between salmon and bears, and that the major differences between calm vs. rippled conditions through the optical cone (Snell’s window) at the water-air interface remains a largely unexplored theme in assessing foraging preferences and adaptive coloration within and among species using the water-air interface.

The Kwakshua Watersheds Observatory, central coast of British Columbia, Canada

AbstractThe Kwakshua Watersheds Observatory (KWO) is an integrative watersheds observatory on the coastal margin of a rain‐dominated bog‐forest landscape in British Columbia (BC), Canada. Established in 2013, the goal of the KWO is to understand and model the flux of terrestrial materials from land to sea – the origins, pathways, processes and ecosystem consequences – in the context of long‐term environmental change. The KWO consists of seven gauged watersheds and a network of observation sites spanning from land to sea and along drainage gradients within catchments. Time‐series datasets include year‐round measurements of weather, soil hydrology, streamflow, aquatic biogeochemistry, microbial ecology and nearshore oceanographic conditions. Sensor measurements are recorded every 5 min and water samples are collected approximately monthly. Additional observations are made during high‐flow conditions. We used remote sensing to map watershed terrain, drainage networks, soils and terrestrial ecosystems. The watersheds range in size from 3.2 to 12.8 km2, with varying catchment characteristics that influence hydrological and biogeochemical responses. Despite local variation, the overall study area is a global hotspot for yields of dissolved organic carbon, dissolved organic nitrogen and dissolved iron at the coastal margin. This observatory helps fill an important gap in the global network of observatories, in terms of spatial location (central coast of BC), climate (temperate oceanic), hydrology (very high runoff, pluvial regime), geology (igneous intrusive, glacially scoured), vegetation (bog rainforest) and soils (large stores of organic carbon).

Behavioral context of echolocation and prey-handling sounds produced by killer whales (Orcinus orca) during pursuit and capture of Pacific salmon (Oncorhynchus spp.).

Availability of preferred salmonid prey and a sufficiently quiet acoustic environment in which to forage are critical to the survival of resident killer whales (Orcinus orca) in the northeastern Pacific. Although piscivorous killer whales rely on echolocation to locate and track prey, the relationship between echolocation, movement, and prey capture during foraging by wild individuals is poorly understood. We used acoustic biologging tags to relate echolocation behavior to prey pursuit and capture during successful feeding dives by fish‐eating killer whales in coastal British Columbia, Canada. The significantly higher incidence and rate of echolocation prior to fish captures compared to afterward confirms its importance in prey detection and tracking. Extremely rapid click sequences (buzzes) were produced before or concurrent with captures of salmon at depths typically exceeding 50 m, and were likely used by killer whales for close‐range prey targeting, as in other odontocetes. Distinctive crunching and tearing sounds indicative of prey‐handling behavior occurred at relatively shallow depths following fish captures, matching concurrent observations that whales surfaced with fish prior to consumption and often shared prey. Buzzes and prey‐handling sounds are potentially useful acoustic signals for estimating foraging efficiency and determining if resident killer whales are meeting their energetic requirements.

Rain-fed streams dilute inorganic nutrients but subsidise organic-matter-associated nutrients in coastal waters of the northeast Pacific Ocean

Abstract. In coastal regions, rivers and streams may be important sources of nutrients limiting to primary production in marine waters; however, sampling is still rarely conducted across the land-to-ocean aquatic continuum, precluding conclusions from being drawn about connectivity between freshwater and marine systems. Here we use a more-than-4-year dataset (2014–2018) of nutrients (nitrogen, phosphorus, silica, iron) and dissolved organic carbon spanning streams draining coastal watersheds and nearshore marine surface waters along the Central Coast of British Columbia, Canada, at the heart of the North Pacific coastal temperate rainforest region. Mean freshwater and surface marine N:Si:P ratios were 5:20:1 (P:Fe = 1:67) and 6:11:1, respectively, showing relative consistency across the land–ocean interface but deviation from the extended Redfield ratio. Inorganic nutrient concentrations (NO3-+NO2-, PO43-, Si(OH)4) in fresh waters were less than in the receiving marine environment, indicating that freshwater nutrient inputs in this region were of little importance to – or even diluted – the pool of readily available inorganic nutrients in nearshore waters. Conversely, fresh waters increased the pool of organic-matter-associated nutrients, namely dissolved organic nitrogen and iron. The organic-matter-rich landscapes of the region yielded globally significant quantities of dissolved organic nitrogen (304–381 kg km−2 yr−1) and iron (463–596 kg km−2 yr−1), thus acting as important sources of potentially limiting nutrients to both nearshore and offshore waters. These exports may subsidise heterotrophic microbial communities capable of directly consuming and remineralising these nutrients, potentially compensating for the dilution of inorganic nutrients by freshwater inputs. We highlight the need to better understand nutrient limitation in coastal waters and for concerted research efforts to study the spatial and temporal dynamism at the land–ocean interface along the northeast Pacific coast.

Ecological predictors of lateral line asymmetry in stickleback (Gasterosteus aculeatus)

Threespine stickleback exhibit a row of superficial neuromasts that project through the bony plates on each side of the trunk and which constitute an important sensory modality for detection of near-field water motion. Previously, we have shown that numbers of neuromasts on each structural plate are highly variable among populations. In the current paper, we expand this study to evaluate the extent of deviation from bilateral symmetry of 4344 fish in 57 natural and three transplant populations of threespine stickleback from lakes, streams and oceanic habitats of coastal British Columbia, predicting that neuromasts would be largely bilaterally symmetrical for optimal detection of external stimuli. In contrast, we found asymmetry in all populations, the greatest amount occurring on the anterior buttressing lateral plates and on populations with the fewest neuromasts. We found no consistent trends of signed (directional) asymmetry (SA) among the populations while relative absolute asymmetry (RAA) is lower in dystrophic (stained) habitats than in clearwater habitats (p < 0.001), except for fish with few neuromasts. Sexual dimorphism in RAA is also greater in dystrophic habitats (p < 0.001). Transplants from stained lakes to unstained ponds resulted in a 0.1% to 14% difference in RAA from the source population in less than 12 generations but varied in direction among experiments. Our data suggest a widespread tendency for populations exposed to reduced photic information to exhibit reduced asymmetry in their lateral line system, which can change rapidly in response to a new environment.

Old‐growth forest structure in a low‐productivity hypermaritime rainforest in coastal British Columbia, Canada

AbstractDendrochronological analyses were conducted across a gradient of productivity and soil drainage quality characterizing four vegetation types in a low‐productivity hypermaritime (perhumid) temperate rainforest on the Central Coast of British Columbia, Canada. We examined the structure, composition, and stand dynamics of trees growing in 400 m2 plots located in blanket bog, bog woodland, bog forest, and zonal forest vegetation types. We sampled over 2500 trees and 1500 seedlings and saplings and our dendrochronological reconstruction of six tree species revealed establishment ages extending to 660 A.D. (1350 yr). All forest plots contained numerous old trees (&gt;250 yr) and the zonal forest and bog forest vegetation types contained significantly taller trees and also had the greatest amount of suppressed, shade‐tolerant tree species. The bog woodland vegetation type contained more seedlings and saplings than the other three vegetation types combined. The bog forest vegetation type had the highest density of dead standing trees (~530 per hectare). Blanket bogs contained an open structure with very few old trees (&gt;250 yr). Significant differences in the ages of trees existed between forested vegetation types and the more open blanket bog vegetation type. Several trees exceeded 1000 yr in age and were situated in lower‐productivity bog forest and bog woodland sites. We found no evidence of widespread tree cohort establishment, indicating that small‐scale disturbances such as individual tree mortality and gap‐forming dynamics are likely the most frequent disturbance in the study area.

Geographic Response Strategies on Canada's West Coast

Abstract In 2012, Western Canada Marine Response Corporation (WCMRC) began developing site specific shoreline protection strategies, known at Geographic Response Strategies (GRS) for the entire coast of British Columbia (B.C.). The project started in Vancouver Harbour and has since spread along the Salish Sea and Strait of Juan de Fuca, as well as into Prince Rupert and Kitimat on the northern B.C. coast. Recognizing that B.C. has approximately 27,000 km of coastline (~16,777 miles) and with 450 strategies already developed only within a few hundred kilometres, WCMRC saw a need to automate the GRS development process from data collection all the way to the final GRS output. In conjunction with a local environmental consulting company, WCMRC developed a new sensitivity model. This new model can help the Response Readiness Team quickly assess intertidal sensitivity to oiling based on shoreline type, oil residency index, biological, archaeological, and/or socio-economic features of the shoreline, as well as operational protection feasibility. Now, using ESRI GIS web tools, a GRS can be developed automatically as a geo-referenced PDF, easily exportable to mobile devices for operational use. Overall, the automated enhancements have provided WCMRC with the tools necessary to manage the GRS program for B.C.'s entire coast. This means that more coastline can be assessed far more quickly and GRS's can be developed using fewer human resources. Additionally, if a spill occurs in a more remote area that has not yet had GRS's developed, they can be created within minutes based on the information from the Environment Unit in the Incident Command Post, or initial assessments by responders.

Contrasting root and shoot cold tolerance of a conifer with indeterminate growth

Yellow-cedar (Callitropsis nootkatensis (D. Don) D.P. Little), a conifer in the Cupressaceae with indeterminate growth, is undergoing severe decline and mortality in southeast Alaska and the coast of northern and central British Columbia. This decline is attributed to cold damage to roots associated with climate warming and reduced snowpack. The cold tolerance of indeterminate conifer species is little studied, and less is known about root cold tolerance, as most studies focus on shoots. We compared the seasonal cycle of cold hardiness in roots and shoots of yellow-cedar seedlings from high- and low-elevation populations over 1 year. Freezing tolerance of shoots followed a typical seasonal cycle, with low levels of cold tolerance observed from April to October and moderate levels of cold tolerance observed in mid-winter. Differences in shoot cold tolerance among populations were consistent with the latitude and elevation of origin. In contrast, at the same freezing temperatures, roots of all seedlings had consistent, high levels of cold damage throughout the year.

Use of Multi-Temporal LiDAR to Quantify Fertilization Effects on Stand Volume and Biomass in Late-Rotation Coastal Douglas-Fir Forests

Forest fertilization is common in coastal British Columbia as a means to increase wood production and potentially enhance carbon sequestration. Generally, the effects of fertilization are determined by measuring sample plots pre- and post-treatment, resulting in fertilization effects being determined for a limited portion of the treatment area. Applications of remote sensing-based enhanced forest inventories have allowed for estimations to expand to the wider forested area. However, these applications have not focused on monitoring the effects of silvicultural treatments. The objective of this research was to examine if a multi-temporal application of the LiDAR area-based method can be used to detect the fertilization effects on volume, biomass, and height in a second-growth Douglas-fir (Pseudotsuga menziesii) stand. The study area on Vancouver Island was fertilized in January 2007, and sample plots were established in 2011. LiDAR acquisitions were made in 2004, prior to fertilization, and in 2008, 2011, and 2016, covering both treated and untreated areas. A total of 29 paired LiDAR blocks, comprised of four 20 m resolution raster cells, were selected on either side of the fertilization boundary for analysis of the effects across several different stand types differing in the percentage of Douglas-fir, site index, and age. Random forest (RF) plot-level models were developed to estimate total stem volume and total stem biomass for each year of LiDAR acquisition using an area-based approach. Plot level results showed an increase in stem volume by 13% fertilized over control from 2005 to 2011, which was similar to a 14% increase in above-ground carbon stocks estimated using a tree-ring stand reconstruction approach. Plot-level RF models showed R2 values of 0.86 (volume) and 0.92 (biomass) with relative cross-validated root mean square errors of 12.5% (volume) and 11.9% (biomass). For both the sample plots and LiDAR blocks, statistical results indicated no significant differences in volume or biomass between treatments. However, significant differences in height increments were detected between treatments in LiDAR blocks. The results from this research highlight the promising potential for the use of enhanced forest inventory methods to rapidly expand the assessment of treatment effects beyond sample plots to the stand, block, or landscape level.

Forest Management Impacts on Greenhouse Gas Fluxes from Riparian Soils Along Headwater Streams

Increasing concentrations of atmospheric greenhouse gases (GHGs; CO2, CH4, N2O) cause climate change. Depending on the conditions, soils have the potential to store carbon or to be a source of GHGs to the atmosphere. Riparian soils in particular have high potential to store carbon, but also to be sources of CH4 and N2O. Headwater streams make up a large proportion of stream length in a drainage network, and their riparian zones have valuable ecosystem functions. In parallel, the riparian zones of headwater streams are particularly vulnerable to forest harvest. Studies of GHG fluxes from these unique ecosystems remain limited. Our objective was to quantify the effects of forestry practices and groundwater discharge (DIS) areas on GHG emissions from riparian forest soils in coastal British Columbia. We compared nine sites with three different forest management protocols: (1) harvesting with a riparian buffer, (2) no buffer, and (3) reference sites without harvesting. We measured gas fluxes, soil temperature, soil moisture and depth to the groundwater table alongside headwater streams monthly over one growing season. We found that CH4 uptake rates were 65% lower at the no buffer sites, and N2O emission rates were 52% lower at the no buffer sites, when compared to the reference sites. Additionally, CH4 uptake was 54% lower at DIS areas than in non-DIS areas. The results of our research help inform forest management by demonstrating that maintaining riparian buffers can be effective in protecting the ecosystem functions contributing to soil GHG fluxes.

Endangered predators and endangered prey: Seasonal diet of Southern Resident killer whales.

Understanding diet is critical for conservation of endangered predators. Southern Resident killer whales (SRKW) (Orcinus orca) are an endangered population occurring primarily along the outer coast and inland waters of Washington and British Columbia. Insufficient prey has been identified as a factor limiting their recovery, so a clear understanding of their seasonal diet is a high conservation priority. Previous studies have shown that their summer diet in inland waters consists primarily of Chinook salmon (Oncorhynchus tshawytscha), despite that species' rarity compared to some other salmonids. During other times of the year, when occurrence patterns include other portions of their range, their diet remains largely unknown. To address this data gap, we collected feces and prey remains from October to May 2004-2017 in both the Salish Sea and outer coast waters. Using visual and genetic species identification for prey remains and genetic approaches for fecal samples, we characterized the diet of the SRKWs in fall, winter, and spring. Chinook salmon were identified as an important prey item year-round, averaging ~50% of their diet in the fall, increasing to 70-80% in the mid-winter/early spring, and increasing to nearly 100% in the spring. Other salmon species and non-salmonid fishes, also made substantial dietary contributions. The relatively high species diversity in winter suggested a possible lack of Chinook salmon, probably due to seasonally lower densities, based on SRKW's proclivity to selectively consume this species in other seasons. A wide diversity of Chinook salmon stocks were consumed, many of which are also at risk. Although outer coast Chinook samples included 14 stocks, four rivers systems accounted for over 90% of samples, predominantly the Columbia River. Increasing the abundance of Chinook salmon stocks that inhabit the whales' winter range may be an effective conservation strategy for this population.