Biology subjects

Harley, C. D. G.

Publications and source records attributed to Harley, C. D. G..

3 recordsLinked to original sources

bioRxiv2023

The Prokaryotic and Eukaryotic Microbiome of Pacific Oyster Spat is Shaped by Ocean Warming but not Acidification

Pacific oysters (Magallana gigas, also known as Crassostrea gigas), the most widely farmed oysters, are under threat from climate change and emerging pathogens. In part, their resilience may be affected by their microbiome, which, in turn, may be influenced by ocean warming and acidification. Consequently, for three weeks, we exposed early-development Pacific oyster spat to different temperatures (18 and 24 {degrees}C) and pCO2 levels (800, 1600 and 2800 {micro}atm) in a fully crossed design. Under all conditions, the microbiome developed over time, with potentially pathogenic ciliates (Uronema marinum) greatly reduced in all treatments, suggesting that the spats microbiome undergoes adaptive shifts as the oysters age. The microbiome composition also differed significantly with temperature, but not acidification, indicating that M. gigas spat microbiomes can be altered by ocean warming but resilient to ocean acidification in our experiments. These findings highlight the spat microbiomes flexibility to environmental changes as well as its "protective" capability against potentially pathogenic microbes.

microbiology↗

bioRxiv2022

Temperature dependence of competitive ability differs from that of growth rate

The effect of climate warming on future community composition is expected to be contingent on competitive outcomes, yet we currently lack mechanistic ecological understanding of how temperature affects competitive ability. Here, we combine resource competition theory with metabolic scaling theory and test hypotheses about how the temperature dependence of competitive ability changes with temperature. We find that the minimum resource requirement for growth, R* - an inverse indicator of competitive ability in phytoplankton - changes with temperature following a U-shaped pattern in all four species tested. The shape of temperature-dependence of competitive ability is systematically different from the temperature-dependence of population growth rates, both in our experiments and in collated data from previous studies. Our results suggest that exploitative competitive success is highest at temperatures that are sub-optimal for growth, and declines rapidly at both cold and warm ends of the thermal performance curve.

ecology↗

bioRxiv2022

Ocean acidification increases susceptibility to sub-zero air temperatures in ecosystem engineers (Mytilus sp.): a limit to poleward range shifts

Ongoing climate change has caused rapidly increasing temperatures, and an unprecedented decline in seawater pH, known as ocean acidification. Increasing temperatures are redistributing species towards higher and cooler latitudes which are most affected by ocean acidification. Whilst the persistence of intertidal species in cold environments is related to their capacity to resist sub-zero air temperatures, studies have never considered the interacting impacts of ocean acidification and freeze stress on species survival and distribution. A full-factorial experiment was used to study whether ocean acidification increases mortality in Mytilus spp. following sub-zero air temperature exposure. We examined physiological processes behind variation in freeze tolerance using 1H NMR metabolomics, analyses of fatty acids, and amino acid composition. We show that low pH conditions (pH = 7.5) significantly decrease freeze tolerance in both intertidal and subtidal populations of Mytilus spp. Under current day pH conditions (pH = 7.9), intertidal M. trossulus were more freeze tolerant than subtidal M. trossulus and M. galloprovincialis. Opposite, under low pH conditions, subtidal M. trossulus was more freeze tolerant than the other groups. We observed a marked shift from negative to positive metabolite-metabolite correlations across species under low pH conditions, but there was no evidence that the concentration of individual metabolites or amino acids affected freeze tolerance. Finally, pH-induced changes in the composition of cell membrane phospholipid fatty acids had no effect on survival. These results suggest that ocean acidification can offset the poleward expanding facilitated by warming, and that reduced freeze tolerance could result in a niche squeeze if temperatures become lethal at the equatorward edge.

ecology↗