Marine Phytoplankton Temperature versus Growth Responses from Polar to Tropical Waters – Outcome of a Scientific Community-Wide Study

Abstract

“It takes a village to finish (marine) science these days” Paraphrased from Curtis Huttenhower (the Human Microbiome project) The rapidity and complexity of climate change and its potential effects on ocean biota are challenging how ocean scientists conduct research. One way in which we can begin to better tackle these challenges is to conduct community-wide scientific studies. This study provides physiological datasets fundamental to understanding functional responses of phytoplankton growth rates to temperature. While physiological experiments are not new, our experiments were conducted in many laboratories using agreed upon protocols and 25 strains of eukaryotic and prokaryotic phytoplankton isolated across a wide range of marine environments from polar to tropical, and from nearshore waters to the open ocean. This community-wide approach provides both comprehensive and internally consistent datasets produced over considerably shorter time scales than conventional individual and often uncoordinated lab efforts. Such datasets can be used to parameterise global ocean model projections of environmental change and to provide initial insights into the magnitude of regional biogeographic change in ocean biota in the coming decades. Here, we compare our datasets with a compilation of literature data on phytoplankton growth responses to temperature. A comparison with prior published data suggests that the optimal temperatures of individual species and, to a lesser degree, thermal niches were similar across studies. However, a comparison of the maximum growth rate across studies revealed significant departures between this and previously collected datasets, which may be due to differences in the cultured isolates, temporal changes in the clonal isolates in cultures, and/or differences in culture conditions. Such methodological differences mean that using particular trait measurements from the prior literature might introduce unknown errors and bias into modelling projections. Using our community-wide approach we can reduce such protocol-driven variability in culture studies, and can begin to address more complex issues such as the effect of multiple environmental drivers on ocean biota.

Connecting thermal physiology and latitudinal niche partitioning in marine Synechococcus

“…The temperature vs growth curve of the WH8103 strain, isolated in the Sargasso Sea at 28.51N, exhibits a maximum at 28 1C (Moore et al, 1995) and thus supports this conclusion. Our observations support recent surveys which stated that optimum temperature for growth of marine phytoplankton strains is related to the latitude and temperature of their isolation site (Thomas et al, 2012;Boyd et al, 2013), and support field observations that the abundances of the Synechococcus of the 5.1 cluster fall to very low values in the polar oceans, of about hundred cells per ml (Gradinger and Lenz, 1995;Vincent 2000;Not et al, 2004;Cottrell and Kirchman, 2009;Vincent and Quesada, 2012).…”

Effects of elevated CO<sub>2</sub> and temperature on phytoplankton community biomass, species composition and photosynthesis during an experimentally induced autumn bloom in the western English Channel

“…The increased biomass and photosynthetic carbon fixation in this experimental community under elevated pCO 2 is due to the community shift to Phaeocystis spp. The increased biomass in the high-temperature treatment (where microzooplank- ton biomass remained stable between T17 and T36, though lower than the control) may be attributed to enhanced enzymatic activities, since algal growth commonly increases with temperature until after an optimal range (Boyd et al, 2013;Goldman and Carpenter, 1974;Savage et al, 2004). Optimum growth temperatures for marine phytoplankton are often several degrees higher than environmental temperatures (Eppley, 1972;Thomas et al, 2012).…”

“…Atmospheric temperature has been predicted to rise by a further 1.8 to 4 • C by the end of this century (Alley et al, 2007). Phytoplankton metabolic activity may be accelerated by increased temperature (Eppley, 1972), which can vary depending on the phytoplankton species and their physiological requirements (Beardall et al, 2009;Boyd et al, 2013). Long-term data sets already suggest that ongoing changes in coastal phytoplankton communities are likely due to climate shifts and other anthropogenic influences (Edwards et al, 2006;Smetacek and Cloern, 2008;Widdicombe et al, 2010).…”

Southern Ocean phytoplankton physiology in a changing climate

“…Studies of Antarctic phytoplankton indicate that a rise in temperature alone causes only a modest increase in their growth rate (e.g. Rose et al, 2009;Boyd et al, 2013Boyd et al, , 2015 and this increase is often overcompensated by the negative effects of increased temperature on abiotic and biotic stressors such as nutrient limitation and grazing (Caron and Hutchins, 2013;Lewandowska et al, 2014).…”