Stable isotopes reveal trophic plasticity of the bushy scleractinian coral Stylophora pistillata

10 15 20 25 30 35 23.0 °C North

Stable isotopes reveal trophic plasticity of the bushy scleractinian

coral Stylophora pistillata

Sturaro Nicolas

_{, Hsieh Yun Li Eric}

_{, Liu Ling-Wen}

_{, Wang Pei-Ling}

_{and Denis Vianney}

1_{Institute of Oceanography, National Taiwan University, Taipei 106, Taiwan}

2_{Current address: Laboratory of Oceanology, FOCUS, University of Liège, 4000 Liège, Belgium}

Most scleractinian corals can derive nutrition either autotrophically or heterotrophically, which allows them to use diverse trophic pathways. Therefore, when facing environmental changes, these organisms are expected to demonstrate an ability to acclimatise through trophic plasticity. This study proposed to assess the trophic plasticity of the bushy scleractinian coral Stylophora pistillata

by investigating the spatial and temporal variations in δ13_{C and δ}15_{N values of host tissues and their symbionts.}

Acknowledgements

▪ Isotopic analyses suggest that Stylophora pistillata present a certain degree of trophic plasticity and has the ability to change trophic mode according to variable environmental conditions

Assessment of trophic plasticity

Taiwan

▪ No overlap of isotopic niches for the host and symbiont from the two locations

supported by different sources of C and N assimilated by symbionts and/or corals

▪ Similar ranges of N-enrichment with the change in trophic position between the host and symbiont

equivalent degree of heterotrophy;

or similar mechanisms by which the sources are fractionated in the two locations

▪ The area of the standard ellipse of northern colonies is larger than those from the South East

suggest a certain trophic plasticity that may be linked to more variable environmental conditions in the North

*Data source: monthly average sea surface temperatures are from the Central Weather Bureau, Taiwan (www.cwb.gov.tw). The northern coast (1998-2013) and the eastern coast (2002-2013). Annual mean (red dashed line). Monthly maximum and minimum (grey shaded area). Light attenuation (Photosynthetic Active Radiation, PAR, in %) were measured in Green Island (South East) in April 2016. Picture of Stylophora pistillata: www.aquaportail.com.

Coral nutrition

1

2

Exploring intraspecific isotopic niche variation

3

Take home message

Heterotrophy

Autotrophy

Carbohydrates, free amino acids and urea

Inorganic compounds

Inorganic compounds

Taiwan

North

South East

Jan July Dec

▪ Comparison of two locations characterised by contrasted environmental conditions :

temperature (collection from high to low latitudes; in summer and winter 2017) light levels (collection from shallow ~10m to mesophotic waters ~40m) -20 -19 -18 -17 -16 1 2 3 4 5 6 δ13_{C (‰)}

South East North

δ 15N (‰) Symbiont (n=25) Host (n=25) Symbiont (n=12) Host (n=12) 0 1 2 3 4 5 6 Mo d e l-e s tima te d St a n d a rd El lip s e Are a (‰ 2 ) Host North Host South East Corrected SEA

This research was supported by the Ministry Of Science and Technology (Taiwan, no. 106-2611-M-002-008). NS was funded by a National Taiwan University postdoctoral fellowship (Taiwan, no. 106R4000) and is currently funded by a Research Project of the Fund for Scientific Research (Belgium, PDR 31240620). Authors would like to thank Q. Chen, Y.T.V. Lin and J.W. Chen for help during fieldwork, as well as M. Pinzone, L. N. Michel and B. Lebourg for their help in niche isotopic analyses and interpretation.

10 15 20 25 30 35 Jan July 25.4 °C Dec South East Se a su rf ace t em p er atu re ( °C )

*Additional information on data

▪ Evaluation of intraspecific trophic variability by comparing coral isotopic niches Se a su rfa ce te m p er atu re ( °C ) Green Island

▪ Analyses of additional species and locations will provide essential insights into the trophic plasticity of scleractinian corals and how these species might adjust their nutrition in response to environmental changes

Euphotic area PAR (%) 100 50 0 South East D ep th (m ) 60 30 15 0 Mesophotic area