The response of a boreal deep-sea sponge holobiont to acute thermal stress

R Strand,T Kutti,H M Luter,J K H Fang,R J Bannister,N S Webster,S Whalan

doi:10.1038/s41598-017-01091-x

R Strand, T Kutti + Show 5 more

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https://doi.org/10.1038/s41598-017-01091-x

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Abstract

Effects of elevated seawater temperatures on deep-water benthos has been poorly studied, despite reports of increased seawater temperature (up to 4 °C over 24 hrs) coinciding with mass mortality events of the sponge Geodia barretti at Tisler Reef, Norway. While the mechanisms driving these mortality events are unclear, manipulative laboratory experiments were conducted to quantify the effects of elevated temperature (up to 5 °C, above ambient levels) on the ecophysiology (respiration rate, nutrient uptake, cellular integrity and sponge microbiome) of G. barretti. No visible signs of stress (tissue necrosis or discolouration) were evident across experimental treatments; however, significant interactive effects of time and treatment on respiration, nutrient production and cellular stress were detected. Respiration rates and nitrogen effluxes doubled in responses to elevated temperatures (11 °C & 12 °C) compared to control temperatures (7 °C). Cellular stress, as measured through lysosomal destabilisation, was 2–5 times higher at elevated temperatures than for control temperatures. However, the microbiome of G. barretti remained stable throughout the experiment, irrespective of temperature treatment. Mortality was not evident and respiration rates returned to pre-experimental levels during recovery. These results suggest other environmental processes, either alone or in combination with elevated temperature, contributed to the mortality of G. barretti at Tisler reef.

Highlights

A changing global climate is predicted to significantly impact marine environments[1,2,3] and well-studied shallow tropical coral reefs provide evidence of the sensitivity of marine ecosystems to increases in sea surface temperature (SST)[4]
A significant interaction between the main effects of temperature and duration of exposure were responsible for the differences in respiration rates of G. barretti under the experimental treatments (P < 0.001, Table 1, Fig. 1)
Of interest in the interaction are the trends at exposure temperatures of 11 °C and 12 °C, where marginal means for G. barretti individuals were consistently higher, at each sampling time point, than the marginal means for G. barretti individuals exposed to 7 °C and 9 °C

Summary

Introduction

A changing global climate is predicted to significantly impact marine environments[1,2,3] and well-studied shallow tropical coral reefs provide evidence of the sensitivity of marine ecosystems to increases in sea surface temperature (SST)[4]. These climate effects are evident for sessile invertebrate species, which often exhibit narrow ranges of thermal tolerance[5,6,7]. Other studies have reported sponge tolerance to future predicted climate change conditions with survival, growth, and secondary metabolite biosynthesis of some species unaffected by SST elevated 3 °C above present-day summer-maxima[40, 41]

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