Temperature Dependent Effects of Elevated CO2 on Shell Composition and Mechanical Properties of Hydroides elegans: Insights from a Multiple Stressor Experiment

Abstract

The majority of marine benthic invertebrates protect themselves from predators by producing calcareous tubes or shells that have remarkable mechanical strength. An elevation of CO2 or a decrease in pH in the environment can reduce intracellular pH at the site of calcification and thus interfere with animal’s ability to accrete CaCO3. In nature, decreased pH in combination with stressors associated with climate change may result in the animal producing severely damaged and mechanically weak tubes. This study investigated how the interaction of environmental drivers affects production of calcareous tubes by the serpulid tubeworm, Hydroides elegans. In a factorial manipulative experiment, we analyzed the effects of pH (8.1 and 7.8), salinity (34 and 27‰), and temperature (23°C and 29°C) on the biomineral composition, ultrastructure and mechanical properties of the tubes. At an elevated temperature of 29°C, the tube calcite/aragonite ratio and Mg/Ca ratio were both increased, the Sr/Ca ratio was decreased, and the amorphous CaCO3 content was reduced. Notably, at elevated temperature with decreased pH and reduced salinity, the constructed tubes had a more compact ultrastructure with enhanced hardness and elasticity compared to decreased pH at ambient temperature. Thus, elevated temperature rescued the decreased pH-induced tube impairments. This indicates that tubeworms are likely to thrive in early subtropical summer climate. In the context of climate change, tubeworms could be resilient to the projected near-future decreased pH or salinity as long as surface seawater temperature rise at least by 4°C.

Tube morphology, ultrastructures and mineralogy in recent Spirorbinae (Annelida: Polychaeta: Serpulidae). II. Tribe Spirorbini

“…An observation that amorphous matter content in Hydroides elegans shows negative correlation with temperature (Chan et al, 2013), generally agrees with our data on Spirorbini (IOP structure of warm-water Groups A and C has low cement content, while relatively coldwater Group B always demonstrates high cement content).…”

Effect of ocean acidification and elevated temperature on growth of calcifying tubeworm shells (<i>Spirorbis spirorbis</i>): An <i>in-situ</i> benthocosm approach

“…However, the tubes that are formed at lower CaCO 3 saturation may be more fragile. This is in line with results from cultured juvenile worm tubes of the tropical serpulid species Hydroides elegans, which showed reductions in shell hardness and wall thickness at lowered pH and CaCO 3 saturation states (Chan et al, 2012(Chan et al, , 2013Li et al, 2014).…”

“…Several recent ocean acidification experiments have included serpulid worms of a variety of species. Most studies focused on the tropical species Hydroides elegans (Lane et al, 2013;Chan et al, 2012Chan et al, , 2013Mukherjee et al, 2013;Li et al, 2014). The results indicated reduced growth, increased porosity and reduced mechanical strength of the worm tubes, as well as increased mortality of larvae at lowered pH (<7.9).…”

The Role of Temperature in Determining Species' Vulnerability to Ocean Acidification: A Case Study Using Mytilus galloprovincialis

“…For example, Chan et al (2013) found that elevated temperature offset the negative effects of reduced pH and salinity on the accretion and strength of calcareous tubes of tropical tubeworms [67]. Similarly, moderate warming was found to slightly ameliorate the negative effects of OA on the shell growth of larval oysters (although more extreme warming exacerbated the effects of OA) [68].…”