Geology topics

Spencer T. Gardner

Publications and source records attributed to Spencer T. Gardner.

3 recordsLinked to original sources

USGS2026

Adaptive capacity of freshwater organisms in North America: Current understanding and future applications

Freshwater species are increasingly threatened by climate change, yet our ability to assess their vulnerability remains incomplete. Typically, climate change vulnerability assessments (CCVAs) evaluate three components: exposure, sensitivity, and adaptive capacity. Adaptive capacity, defined as the ability of a species to adjust to changing conditions, provides critical insight into how species may persist under future scenarios and can strengthen conservation planning by highlighting opportunities for resilience and targeted management strategies. Trait-based approaches offer a promising path for managers to operationalize adaptive capacity by identifying measurable biological and ecological traits that influence climate change response strategies. However, these insights are rarely integrated into broader vulnerability frameworks that support conservation decision making. We build on previous research to synthesize current understanding of adaptive capacity for three freshwater taxa in North America: fishes, mussels, and crayfishes. Our objectives were to: (1) assess the relevance of adaptive capacity factors for fishes, mussels, and crayfishes; (2) identify key opportunities and gaps in linking trait-based information into adaptive capacity assessments; and (3) illustrate how incorporating adaptive capacity can enhance management decisions for freshwater species under climate change. We used an expert workshop, literature review, and case studies to identify relevant adaptive capacity factors, assess available information, and evaluate inclusion in management contexts. We found that all three taxa had sufficient information to inform adaptive capacity assessments. In addition to existing adaptive capacity factors, we identified Morphology as an important yet underutilized cross-cutting diagnostic category when information was limited. By explicitly linking trait-based approaches with adaptive capacity frameworks, we offer practical guidance for improving climate adaptation strategies and prioritizing management actions for freshwater biodiversity under accelerating global change.

Global Change Biology Communications↗

USGS2024

Climate-influenced phenology of larval fish transport in a large lake

Elucidating physical transport phenologies in large lakes can aid understanding of larval recruitment dynamics. Here, we integrate a series of climate, hydrodynamic, biogeochemical, and Lagrangian particle dispersion models to: (1) simulate hatch and transport of fish larvae throughout an illustrative large lake, (2) evaluate patterns of historic and potential future climate-induced larval transport, and (3) consider consequences for overlap with suitable temperatures and prey. Simulations demonstrate that relative offshore transport increases seasonally, with shifts toward offshore transport occurring earlier during relatively warm historic and future simulations. Intra- and inter-annual trends in transport were robust to assumed pelagic larval duration and precise location and timing of hatching. Larvae retained nearshore generally encountered more favorable temperatures and zooplankton densities compared to larvae transported offshore. Larval exploitation of nearshore resources under climate change may depend on a concomitant shift to earlier spawning and hatch times in advance of earlier offshore transport.

Lake Michigan↗

USGS2024

Understanding and forecasting potential recruitment of Lake Michigan fishes by modeling growth and survival of larval stages with coupled climate, biophysical, and bioenergetics models

Individual adult fish can produce huge numbers of small offspring, but most die in the first weeks of life. Environmental changes that lead to even small changes in early life survival can have a disproportionate impact on the number of fish that survive and ultimately support fisheries. Lake Michigan supports valuable recreational and commercial fisheries that can fluctuate with how well fish survive in early life. Statistical models have revealed linkages between survival and climate characteristics, such as water temperature, but the exact mechanisms remain unclear and how future climate will affect the survival of young fish is highly uncertain. We integrated a series of models to investigate how climate variability may explain historical variation in the survival of young alewife and yellow perch, two fish populations that support key fisheries either directly or indirectly, while also projecting their future survival in the mid-21st century under different scenarios informed by consultation with fishery managers. Our model results revealed how spring and summer water temperatures in Lake Michigan can affect the environment in which young alewife and yellow perch grow and survive. Specifically, in years when lake warming is rapid, young fish are more likely to be transported from their natal, productive, nearshore environments to cooler and less productive offshore environments, unless adults also spawn earlier in these warm years. Furthermore, model predictions of prey abundance for young fish in the mid-21st century indicate less favorable conditions for growth and survival compared to predictions based solely on warming temperatures. With completion of the final products in the coming year, including predicted growth and survival of young fish under different future scenarios, fishery managers will have more information to share with stakeholders regarding how expectations may need to be modified regarding alewife and yellow perch productivity.

Lake Michigan↗