ORCC: Marine predator and prey response to climate change: Synthesis of Acoustics, Physiology, Prey, and Habitat In a Rapidly changing Environment (SAPPHIRE)

Oceans are experiencing significant impacts of climate change, yet the effects on marine organisms remain largely unknown. It is critical to understand how rapid environmental changes will impact the availability and quality of prey species, and consequently how these changes will impact predator health and population resilience. This project identifies and describes the impacts of environmental variation on a crucial marine prey species (krill) and one of its primary predators (blue whale).

The project examines how changing ocean conditions affect the availability and quality of krill, and how this then impacts blue whale body condition, hormone levels, and foraging and reproductive effort. The focus on prey and predator physiology and fitness will inform the development of novel Species Health Models (SHM), which will advance the understanding of prey-predator co-responses to changing climatic conditions and the influence of species health on population resilience.

SHM will provide a way to monitor and predict species response to climate change by shifting the focus of management efforts toward thresholds based on health, which could enable mitigation measures before population-level declines occur. Furthermore, understanding krill response to variable environmental conditions will inform management of marine prey and predator response to climate change broadly, while public attention on the iconic blue whale can enhance societal awareness and motivate behavioral change.

Species resilience to climate change over shorter timescales will be determined by fitness and fecundity of individuals mediated through behavioral and physiological response pathways. This project aims to describe the co-response of marine prey (krill; Nyctiphanes australis) and predator (blue whale; Balaenoptera musculus brevicauda) health to environmental variation at individual and population levels, enabling a comprehensive understanding of impacts on species fitness under climate change conditions.

Data will be collected on krill and blue whale ecology and physiology in the South Taranaki Bight of New Zealand during three consecutive years (2024-2026). Controlled experiments will determine effects of temperature on krill metabolic rates, energy requirements, and body condition (bioenergetic and biochemical responses). The availability of prey to foraging blue whales will be assessed through net tows and active acoustics to determine krill energetic content, distribution, and density.

Impacts of changes in prey and environmental conditions on individual whale physiology will be quantified through Unoccupied Aircraft Systems assessments of body condition to document nutritive state, and biopsy sampling of skin and blubber tissue to quantify stress (glucocorticoids), nutrition (thyroid, leptin) and reproductive (progesterone, testosterone) hormone levels. At the population level, hydrophones will record blue whale vocalizations to quantify changes in foraging and breeding effort relative to changes in prey and environmental conditions.

These data streams will be integrated through multivariate analyses and development of Species Health Models to understand prey and predator co-response to environmental change, predict species health impacts and fitness consequences, and identify thresholds in prey and predator population resilience.

This award was co-funded through the GEO/OCE Biological Oceanography Program and the BIO/IOS Organismal Responses to Climate Change Program.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.