Current Research

Our work spans a range of areas, some major themes are listed below.

Impacts of Warming

Understanding the impacts of climate change on aquatic organisms and ecosystems is a major motivation to our research. We are working on how the physiology, vital rates and morphology of organisms respond to temperature. Ectotherms near universally follow the Temperature-Size Rule, maturing at a smaller size when reared in warmer conditions. We are investigating mechanisms and drivers of this rule. A recent topic of research has been to quantify and compare clines in body size of species with latitude, altitude and over seasons, in order to better appreciate how these are inter-related and the degree to which these share common drivers. We are NERC funded to explore how climate warming impacts the size of animals, including plankton and fish, and to develop mitigation approaches for aquaculture. This is a major collaboration between the Universities of Liverpool and Sterling and the Scottish Association of Marine Sciences.

Recent papers:

Horne CR, Hirst AG, Atkinson D, Almeda R, Kiørboe T (2019) Rapid shifts in the thermal sensitivity of growth but not development rate causes temperature-size response variability during ontogeny in arthropods. Oikos https://doi.org/10.1111/oik.06016

Evans LE, Hirst AG, Kratina P, Beaugrand G (2019) Temperature-mediated changes in zooplankton body size: large scale temporal and spatial analysis. Ecography doi.org/10.1111/ecog.04631

Horne CR, Hirst AG, Atkinson D (2018) Insect temperature-body size trends common to laboratory,  latitudinal and seasonal gradients are not found  across altitudes. Functional Ecology https://doi.org/10.1111/1365-2435.13031

Horne CR, Hirst AG, Atkinson D (2017) Seasonal body size reductions with warming co-vary with major body size gradients in arthropod species. Proceedings of the Royal Society B 284: 20170238. http://dx.doi.org/10.1098/rspb.2017.0238

Horne CR, Hirst AG, Atkinson D, Neves A, Kiørboe T (2016) A global synthesis of seasonal temperature-size responses in copepods. Global Ecology and Biogeography 25: 988-999. doi: 10.1111/geb.12460

Horne CR, Hirst AG, Atkinson D (2015) Temperature-size responses match latitudinal-size clines in arthropods, revealing critical differences between aquatic and terrestrial species. Ecology Letters 18: 327-335doi: 10.1111/ele.12413

Forster J, Hirst AG, Esteban G (2013) Achieving temperature-size changes in a unicellular organism. The ISME Journal 7: 28-36. doi: 10.1038/ismej.2012.76

Forster J, Hirst AG, Atkinson D (2012) Warming induced reductions in body size are greater in aquatic than terrestrial species. Proceedings of the National Academy of Sciences USA 109: 19310-19314. doi: 10.1073/pnas.1210460109

Forster J, Hirst AG (2012) The temperature-size rule emerges from ontogenetic differences between growth and development rates. Functional Ecology 26: 483-492

Forster J, Hirst AG, Woodward G (2011) Growth and development rates have different thermal responses. The American Naturalist 178: 668-678

Forster J, Hirst AG, Atkinson D (2011) How do organisms change size with changing temperature? The importance of reproductive method and ontogenetic timing. Functional Ecology 25: 1024-1031

Body-Size Dependence of Biological Rates

How biological rates relate to body size has fascinated scientists  for over a century, in part because the relationships are very strong, yet the causes remain enigmatic. We have been examining how rates of energy use (metabolism) relate to body size (commonly termed scaling) in diverse aquatic animals. By combining new theoretical predictions with data syntheses, we are developing a new surface area-dependent model of metabolic scaling. This research includes collaboration with David Atkinson (University of Liverpool), Doug Glazier (Junita College, USA) , Thomas Kiørboe (DTU Copenhagen) and many other researchers.

Recent papers:

Tan H, Hirst AG, Glazier D, Atkinson D (2019) Ecological pressures, and the contrasting scaling of metabolism and body shape in coexisting taxa: cephalopods versus teleost fish. Philosophical Transactions of the Royal Society B 374: 20180543. http://dx.doi.org/10.1098/rstb.2018.0543

Hirst AG, Lilley MKS, Glazier DS, Atkinson D (2016) Ontogenetic body-mass scaling of nitrogen excretion relates to body surface area in diverse pelagic invertebrates. Limnology and Oceanography 62: 311-319. doi: 10.1002/lno.10396

Glazier DS, Hirst AG, Atkinson D (2015) Shape shifting predicts ontogenetic changes in metabolic scaling in diverse aquatic invertebrates. Proceedings of the Royal Society B 282: 20142302. doi: 10.1098/rspb.2014.2302

Hirst AG, Glazier D, Atkinson D (2014) Body shape shifting during growth permits tests that distinguish between competing geometric theories of metabolic scalingEcology Letters 17: 1274-1281. doi: 10.1111/ele.12334

Kiørboe T, Hirst AG. (2014)  Shifts in mass-scaling of respiration, feeding, and growth rates across life-form transitions in marine pelagic organisms. The American Naturalist 183: E118-E130. doi: 10.1086/675241

Hirst AG, Forster J (2013) When growth models are not universal: evidence from marine invertebrates. Proceedings of the Royal Society B 280: 20131546. doi: 10.1098/rspb.2013.1546

Ocean Biogeochemistry and Role of Zooplankton

We are working on plankton dynamics and ocean biogeochemistry. This includes collaborations with Corinne Le Quéré (Présidente Haut Conseil pour le climat), Angus Atkinson (Plymouth Marine Laboratories) and many international scientists. Highlights include producing the first quantitative global accounts of zooplankton mortality, fecundity and growth, and correcting the equations used to determine their productivity.

Recent papers:

Le Quéré C, Buitenhuis ET, Moriarty R, Alvain S, Aumont O , Bopp L, Chollet S, Enright C, Franklin DJ, Geider RJ, Harrison SP, Hirst A, Larsen S, Legendre L, Platt T, Prentice IC, Rivkin RB, Sathyendranath S, Stephens N, Vogt M (2016) Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles. Biogeosciences13: 4111–4133. doi: 10.5194/bg-13-4111-2016

Maud J, Atkinson A, Hirst AG, Lindeque PK, Widdicombe CE, Harmer RA, McEvoy AJ, Cummings DC (2015) How does Calanus helgolandicus maintain its population in a variable environment? Analysis of a 25-year time series from the English Channel. Progress in Oceanography 137: 513-523. doi:10.1016/j.pocean.2015.04.028

Hirst AG, Keister JE, Richardson AJ, Ward P, Shreeve RS, Escribano RV (2014) Re-assessing copepod growth using the Moult Rate Method. Journal of Plankton Research 36: 1224-1232. doi: 10.1093/plankt/fbu045

Sex-Based Differences (Ecology and Evolution)

Recently we have been exploring differences between males and females of species, addressing the questions as to what drives sex ratios, longevity and size at maturity differences (including work on insects, plankton and fish). We are developing sex-based fitness models.

Recent papers:

Horne CR, Hirst AG, Atkinson D (2020) Selection for increased male size predicts variation in sexual size dimorphism among fish species. Proceedings of the Royal Society B 287: 20192640. http://dx.doi.org/10.1098/rspb.2019.2640

Horne CR, Hirst AG, Atkinson D (2019) A synthesis of major environmental-body size clines of the sexes within arthropod species. Oecologia 190: 343–353

Maud JL, Hirst AG, Atkinson A, Lindeque PK, McEvoy AJ (2018) Mortality of Calanus helgolandicus: sources, differences between the sexes and consumptive and non-consumptive processes. Limnology & Oceanography. doi: 10.1002/lno.10805

Hirst AG, Horne CR, Atkinson D (2015) Equal temperature-size responses of the sexes are widespread within arthropod species. Proceedings of the Royal Society B 282: 20152475. doi: 10.1098/rspb.2015.2475

Hirst AG, Kiørboe T (2014) Macroevolutionary patterns of sexual size dimorphism in copepods. Proceedings of the Royal Society B 281: 20140739. doi:10.1098/rspb.2014.0739

FitzGeorge-Balfour T, Hirst AG, Lucas CH, Craggs J (2013) Influence of copepod size and behaviour on vulnerability to predation by the scyphomedusa Aurelia aurita. Journal of Plankton Research 36: 77-90. doi: 10.1093/plankt/fbt077

Hirst AG, Bonnet D, Conway DVP, Kiørboe T (2013) Female-biased sex ratios in marine pelagic copepods: Comment on Gusmão et al (2013). Marine Ecology Progress Series 489: 297-298

Hirst AG, Bonnet D, Conway DVP, Kiørboe T (2010) Does predation control adult sex ratios and longevities in marine pelagic copepods? Limnology & Oceanography 55: 2193-2206

Aquatic ecosystems have a profound impact on humankind and the biosphere, and can provide critical insight into biological questions. Using marine and freshwater organisms our research aims to mechanistically understand and predict rules of physiology and ecology. We examine physiology, vital rates and ocean biogeochemistry, including assessing the impacts of climate change. In our work we use diverse approaches including meta-analysis, experimentation, fieldwork and modelling.