Description: Gelatinous and soft-bodied zooplankton (GZ) have long been considered to have low energetic value and are insufficient to sustain higher trophic levels. However, the nutritional composition of GZ is often poorly known for entire groups, ignoring species-, size- and stage-specific differences. Organic matter and elemental composition (carbon and nitrogen) were measured for more than 1000 specimens from 34 GZ species collected in the Northeast Pacific between 2014-2020 using a variety of nets (CanTrawl250, Bongo net, Juday net, Multinet Medi, Dip net, Midwater trawl, Neuston net). Size-dependent variability was shown for several species. Differences in organic content and elemental composition by development stage were observed in a salp and scyphomedusa species, highlighting the need to consider life cycle stages separately.

Description: Pacific salmon stocks are in decline with climate change named as a contributing factor. The North Pacific coast of British Columbia is characterized by strong temporal and spatial heterogeneity in ocean conditions with upwelling events elevating CO2 levels up to 10-fold those of pre-industrial global averages. Early life stages of pink salmon have been shown to be affected by these CO2 levels, and juveniles naturally migrate through regions of high CO2 during the energetically costly phase of smoltification. To investigate the physiological response of out-migrating wild juvenile pink salmon to these naturally occurring elevated CO2 levels, we captured fish in Georgia Strait, British Columbia and transported them to a marine lab (Hakai Institute, Quadra Island) where fish were exposed to one of three CO2 levels (850, 1500 and 2000 μatm CO2) for 2 weeks. At 1/2, 1 and 2 weeks of exposure, we measured their weight and length to calculate condition factor (Fulton's K), as well as haematocrit and plasma [Cl-]. At each of these times, two additional stressors were imposed (hypoxia and temperature) to provide further insight into their physiological condition. Juvenile pink salmon were largely robust to elevated CO2 concentrations up to 2000 μatm CO2, with no mortality or change in condition factor over the 2-week exposure duration. After 1 week of exposure, temperature and hypoxia tolerance were significantly reduced in high CO2, an effect that did not persist to 2 weeks of exposure. Haematocrit was increased by 20% after 2 weeks in the CO2 treatments relative to the initial measurements, while plasma [Cl-] was not significantly different. Taken together, these data indicate that juvenile pink salmon are quite resilient to naturally occurring high CO2 levels during their ocean outmigration.

Description: Climate change and anthropogenic disturbances, among other factors, can change the seawater stoichiometry (C/N/P) and consequently elemental ratios of phytoplankton. This change in prey stoichiometry may not be tolerated by all grazer/predator species. Gelatinous and soft-bodied zooplankton (GZ) are suggested to be more resilient to such changes. We sampled GZ species (12 taxa in total) in the Northeast Pacific off British Columbia (Canada), determined their phosphorus (P) content and elemental ratios (C/P, N/P), and analysed intraspecific variability associated with size and ontogeny. P was determined as orthophosphate after acidic oxidative hydrolysis with 5 % H2SO4 according to Grasshoff et al. (1999). Carbon (C) and nitrogen (N) data were taken from Lüskow et al. (2021). P % DW (dry weight) decreased with size for Aequorea sp., Aurelia labiata, Cyanea capillata, and Salpa aspera (species with sufficient sample sizes). P % DW differed significantly for two development stages of the salp S. aspera. C/P and N/P were mostly size- and stage-independent. C/P values of GZ were generally higher than values of crustacean zooplankton.

Description: Ocean acidification can negatively impact the early life-stages of marine fish, due to energetic costs incurred by the maintenance of acid–base homeostasis, leaving less energy available for growth and development. The embryos of intertidally spawning fishes, such as Pacific herring, are often air exposed for hours. We hypothesized that air exposure would be beneficial to the developing embryo due to a higher oxygen availability (and thus reduced metabolic costs to secure adequate oxygen) and permitting excess CO2 associated with ocean acidification to be off-gassed during emersion. To investigate this, we reared Pacific herring (Clupea pallasii) embryos under three tidal regimes (subtidal: fully immersed, low intertidal: 2 * 2 h air exposure, and high intertidal: 5 + 9 h air exposure) fully crossed with three aquatic CO2 levels (400, 1500 and 3200 µatm) at a water temperature of 9.5 °C and naturally fluctuating air temperature during air exposure. We measured the effects on embryonic development and hatch, as well as carry-over effects on larval development and survival. Air exposure during embryonic development had significant positive effects on growth, condition and survival in larval Pacific herring, with some interactive effects with CO2. Interestingly, CO2 by itself in the fully immersed treatment had no effect, but had significant interactions with air exposure. Our research suggests that air exposure during low tide can be highly beneficial to intertidally spawning fishes and needs to be taken into account in climate change studies and modeling.

Description: Polar marine ecosystems are particularly vulnerable to the effects of climate change. Warming temperatures, freshening seawater, and disruption to sea-ice formation potentially all have cascading effects on food webs. New approaches are needed to better understand spatiotemporal interactions among biogeochemical processes at the base of Southern Ocean food webs. In marine systems, isoscapes (models of the spatial variation in the stable isotopic composition) of carbon and nitrogen have proven useful in identifying spatial variation in a range of biogeochemical processes, such as nutrient utilization by phytoplankton. Isoscapes provide a baseline for interpreting stable isotope compositions of higher trophic level animals in movement, migration, and diet research. Here, we produce carbon and nitrogen isoscapes across the entire Southern Ocean (〉40°S) using surface particulate organic matter isotope data, collected over the past 50 years. We use Integrated Nested Laplace Approximation-based approaches to predict mean annual isoscapes and four seasonal isoscapes using a suite of environmental data as predictor variables. Clear spatial gradients in δ13C and δ15N values were predicted across the Southern Ocean, consistent with previous statistical and mechanistic views of isotopic variability in this region. We identify strong seasonal variability in both carbon and nitrogen isoscapes, with key implications for the use of static or annual average isoscape baselines in animal studies attempting to document seasonal migratory or foraging behaviors.