The Coltrane (Copepod Life history Traits and Adaptation to New Environments) model is a mathematical framework for layering multiple levels of mesozooplankton biology on top of oceanographic models. It resolves 1) individual life history (strategy traits controlling growth, development, and size, diagnosed from a broad review of lab studies); 2) population dynamics (the time-dependent energy balance between growth, egg production, and predation mortality); and 3) community composition (the envelope of viable trait combinations under particular annual cycles of prey and temperature). It combines ideas from the “optimal annual routine” tradition in animal ecology with the more recent “emergent communities” tradition in marine plankton modelling.
The project springs from the hypothesis that the impact of future climate change on high-latitude planktivores, such as seabirds, fish, and bowhead whales, will come as much through changes in their prey quality (individual size and lipid content) as through changes in their prey biomass: Coltrane is intended to serve as a “translation layer” between oceanographic projections and higher-trophic-level impacts.
This poster from the 2017 workshop on Trait-Based Approaches to Marine Life (Bergen, Norway) gives an overview of work to date and work in progress.
- The model rests on a review of 45 lab studies of copepod growth and development, which identified two species-specific strategy traits that control body size and to a large extent life history: a relative development rate (“does this species reach maturity slowly or quickly, relative to other copepods with the same thermal optimum?”) and a relative growth rate (Does this species grow slowly or quickly for its size?”). You can read all about it in Banas and Campbell (2016), Mar. Ecol. Prog. Ser. 558:21-33 (open access).
- Banas et al. (2016), Front. Mar. Res. 3:225 (open access) gives the full description of Coltrane 1.0 and shows that it can reproduce a variety of observed patterns: * In an idealized biogeography experiment, it correctly predicts life strategies in large Calanus spp. ranging from multiple generations per year to multiple years per generation. * In a Bering Sea testbed, the model replicates the dramatic variability in the abundance of C. glacialis/marshallae observed between warm and cold years of the 2000s. * In a Disko Bay, West Greenland testbed, the model predicts trait correlations along a body size spectrum that closely matches local populations of C. finmarchicus, C. glacialis, and C. hyperboreus: income breeders with a adult size ∼100 μgC reproducing once per year through capital breeders with an adult size >1000 μgC with a multiple-year life cycle. (The poster above extends these results to small copepods, predicting patterns from Oithona spp. to C. hyperboreus).
Applications in progress
- Why is it that C. glacialis/marshallae all but disappear from the Bering Sea in warm years, while C. marshallae are able to do just fine in the Northern California Current in typical years? The Front. Mar. Res. paper above contains some preliminary results that suggest a resolution to this puzzle in terms of prey phenology, which we are following up on using a synthesis of satellite observations from southern California to the Bering Sea by postdoc Sofia Ferreira. (With Julie Keister, Carin Ashjian, and Bob Campbell. This work and the initial model development are supported by the US National Science Foundation.)
- As ice retreats from the Atlantic Arctic, we expect to see large, long-lived, slow-turnover copepods like C. hyperboreus replaced by small, shorter-lived, higher-turnover species like C. finmarchicus. From the point of view of planktivores, which effect is larger in this scenario, the decrease in individual size and energy content, or the increase in population-level productivity? Preliminary results can be found in the workshop poster above. (With Paul Renaud, Malin Daase, and others).
- As a joint venture of Arctic ABC and the NERC Arctic PRIZE programme (2017-21), we are combining Coltrane with moored acoustic observations to examine how the bottom-up and top-down effects of changing light availability shape copepod strategy and productivity. This work is led by postdoc Laura Hobbs. (With Finlo Cottier, Kim Last, Jon Cohen, and Øystein Varpe.)
- In the NERC DIAPOD programme (2017-21), we are using Coltrane to make pan-Arctic projections of range expansion and contraction in C. finmarchicus, C. glacialis, and C. hyperboreus in the rapidly changing Arctic. (With Aidan Hunter, Dougie Speirs, Mike Heath, Jinlun Zhang, Ingrid Ellingsen, and Andy Yool.)
- As part of DIAPOD, PhD student Euan McRae is extending Coltrane to apply to small and large krill and testbeds in the Southern Ocean. (With Geraint Tarling, Eugene Murphy, and Dougie Speirs.)
- Add your project here! Coltrane is open source, has a small but active user community, and we welcome visitors and long-distance collaborators who would like to spin up new case studies.