Biology subjects

Garzke, J.

Publications and source records attributed to Garzke, J..

4 recordsLinked to original sources

bioRxiv2022

C.R.E.A.T.E'ing shifts in first year students' science efficacy that are independent of instructor rank and experience in a large, multi-section online introductory course

With a primary objective to engage students in the process of science online, we transformed a long-standing laboratory course for first-year science students into a more accessible, immersive experience of current biological research using a narrow and focused set of primary literature and the CREATE pedagogy. The efficacy of the CREATE approach has been demonstrated in a diversity of higher education settings and courses. It is, however, not yet known if CREATE can be successfully implemented online with a large, diverse team of faculty untrained in the CREATE pedagogy. Here, we present the transformation of a large-enrollment, multi-section, multi-instructor course for first-year students in which instructors follow different biological research questions but work together to reach shared goals and outcomes. We assessed students: (1) science self-efficacy and (2) epistemological beliefs about science throughout an academic year of instruction fully administered online as a result of ongoing threats posed by COVID-19. Our findings demonstrate that novice CREATE instructors with varying levels of teaching experience and ranks can achieve comparable outcomes and improvements in students science efficacy in the virtual classroom as a teaching team. This study extends the use of the CREATE strategy to large, team-taught, multi-section courses and shows its utility in the online teaching and learning environment.

scientific communication and education↗

bioRxiv2022

Food quantity does not compensate for poor food quality in fitness of juvenile Chinook salmon (Oncorhynchus tshawytscha)

The global temperature increase due to global change is predicted to be between 3.3 - 5.7{degrees}C by 2100 leading to changes at the base of the marine food web in species composition, abundance, and quality at the base of the marine food web leading to flow-on effects of higher trophic levels such as fish and humans. Changes in marine prey availability and nutritional quality can affect juvenile salmon conditions (i.e., growth, condition, and mortality) during the early marine phase. There is limited knowledge of the interplay between prey availability and prey quality and the importance of food quality under food-satiated conditions. Here, a three-phase feeding experiment measured the effects of nutritional quality (fatty acid composition and ratios) on juvenile Chinook salmon (Oncorhynchus tshawytscha) condition. Experimental diets represented the present three different climate scenarios with a present-day diet (Euphausia pacifica), a control diet (commercial aquaculture diet), and a predicted IPCC worst-case scenario diet with low essential fatty acid concentrations (IPCC SSP5-8.5). We tested how potential future low quality food affects growth rates, body condition, fatty acid composition and mortality rates in juvenile Chinook salmon compared to present-quality prey. Fatty acids were incorporated into the salmon muscle at varying rates but, on average, reflected dietary concentrations. High dietary concentrations of DHA, EPA and high DHA:EPA ratios resulted in increased fish growth and condition. In contrast, low concentrations of DHA and EPA and low DHA:EPA ratios in the diets were not compensated for by increased food quantity. This result highlights the importance of considering food quality when assessing fish response to changing ocean conditions. HighlightsO_LIClimate change may decrease the quality of salmon prey through changes in the fatty acid composition. C_LIO_LILow dietary essential fatty acid levels reduce growth and condition and increase mortality rates in juvenile Chinook salmon. C_LIO_LIFood quality changes within zooplankton species but also by changes between species. C_LIO_LIResults suggest potential cascading effects on higher trophic levels when zooplankton species composition shifts to lower quality species. C_LIO_LIHigher food intake cannot compensate for low food quality. C_LI

ecology↗

bioRxiv2022

Dynamic coastal pelagic habitat drives rapid changes in growth and condition of juvenile sockeye salmon (Oncorhynchus nerka) during early marine migration

Migrating marine taxa encounter diverse habitats that differ environmentally and in foraging conditions over a range of spatial scales. We examined body (RNA/DNA, length-weight residuals) and nutritional (fatty acid composition) condition of juvenile sockeye salmon (Oncorhynchus nerka) in British Columbia, while migrating through varied oceanographically waters. Fish were sampled in the stratified northern Strait of Georgia (NSoG); the highly mixed Johnstone Strait (JS); and the transitional zone of Queen Charlotte Strait (QCS). In 2015, body and nutritional condition were high in the NSoG and responded rapidly to reach lowest levels in JS with its low prey availability, and showing signs of compensatory growth in QCS. In 2016, juvenile salmon had significantly lower condition in the NSoG than in 2015, although zooplankton biomass was similar, condition remained low in JS, and no compensatory growth was observed in QCS. We provide evidence that differences in juvenile salmon condition between the two years being due to changes in the food quality available to juvenile fish. Further, we propose that the TGH needs to be extended to incorporate food quality as a parameter to understand changes in fish condition and survival between years.

ecology↗

bioRxiv2017

A temperature dependent trophic cascade modifies temperature dependence of ecosystem function

Ecological communities and their ecosystem functions are sensitive to temperature, and aquatic habitats worldwide continue to experience unprecedented warming. Understanding ecological effects of warming requires linking empirical evidence to theories that allow projection to unobserved conditions. Metabolic scaling theory and its tests suggest that warming accelerates ecosystem functions (e.g., oxygen flux), yet this prediction apparently contradicts community-level studies suggesting warming is a stressor that can reduce ecosystem function. We sought to reconcile these predictions with an experimental test of the hypothesis that cascading trophic interactions modify the temperature-dependence of community structure and ecosystem fluxes. In a series of independent freshwater ecosystems exposed to a thermal gradient, we found that warmer temperatures strengthened the trophic cascade increased and indirectly changed community structure by altering grazer species composition and phytoplankton biomass. Temperature-driven community shifts only modestly affected the temperature dependence of net ecosystem oxygen fluxes. Over the 10 {degrees}C thermal gradient, NPP and ER increased [~]2.7-fold among ecosystems, while standing phytoplankton biomass declined by 85-95%. The exponential increase in oxygen flux over the thermal gradient, as well as monotonic declines in phytoplankton standing stock, suggested no threshold effects of warming across systems. We also observed temperature variation over time, within ecosystems. For phytoplankton biomass, temporal variation had the opposite effect to spatial variation, suggesting that within-community temporal change in community structure was not predicted by space-for-time substitution. We conclude that food chain length can modify effects of temperature on ecosystem fluxes, but that temperature can still have continuous and positive effects on ecosystem fluxes, consistent with patterns based on large-scale, macroecological comparisons. Changes in community structure, including temperature dependent trophic cascades, may be compatible with prevailing and predictable effects of temperature on ecosystem functions related to fundamental effects of temperature on metabolism.\n\nStatement of authorshipJG & MIO designed the study, MIO & US provided materials, JG & SJC performed research and collected data, JG performed zooplankton analysis, SJC performed phytoplankton analysis, JG & MIO performed modeling work, analyzed data output, and wrote the first draft, and all authors contributed substantially to reviews

ecology↗