Population connectivity of fan-shaped sponge holobionts in the deep Cantabrian Sea

Kathrin Busch,Sergi Taboada,Ana Riesgo,Vasiliki Koutsouveli,Pilar Ríos,Javier Cristobo,Andre Franke,Klaus Getzlaff,Christina Schmidt,Arne Biastoch,Ute Hentschel

doi:10.1016/j.dsr.2020.103427

Abstract

Connectivity is a fundamental process driving the persistence of marine populations and their adaptation potential in response to environmental change. In this study, we analysed the population genetics of two morphologically highly similar deep-sea sponge clades (Phakellia hirondellei and the ‘Topsentia-and-Petromica’ clade, (hereafter referred to as ‘TaP clade’)) at three locations in the Cantabrian Sea and simultaneously assessed the corresponding host microbiome by 16S rRNA gene sequencing. A virtual particle tracking approach (Lagrangian modelling) was applied to assess oceanographic connectivity in the study area. We observed overall genetic uniformity for both sponge clades. Notably, subtle genetic differences were observed for sponges of the TaP clade and also their microbiomes between a canyon and bank location, < 100 km apart and with the same depth range. The Lagrangian model output suggests a strong retention of larvae in the study area with variable inter-annual connectivity via currents between the three sampling regions. We conclude that geologic features (canyons) and the prevailing ocean currents may dictate sponge holobiont connectivity and that differentiation can emerge even on small spatial scales.

Highlights

The ocean is the largest interconnected habitat on planet Earth (Ramvirez-Llodra et al, 2011)
Larval dispersal is difficult to observe directly in the field and in particular in the deep-sea. Indirect methods such as molecular markers and virtual particle tracking are commonly applied to analyse genetic connectivity between organ isms
In the c oxidase subunit I (COI) analysis, the ten individuals identified based on the spicule content as P. hirondellei (Topsent, 1890; Bubarida order) were grouped in a monophyletic clade showing relatively moderate support (Supple mentary Material S1B), with Phakellia robusta as sister clade (Supple mentary Material S1B)

Summary

Introduction

The ocean is the largest interconnected habitat on planet Earth (Ramvirez-Llodra et al, 2011). Understanding population- and ecosystem-connectivity in the ocean is crucial for the design of appro priate conservation measures, in particular for the design of marine protected area (MPA) networks (White et al, 2014; Gallego et al, 2017; Andrello et al, 2017; Kenchington et al, 2019). Larval dispersal is difficult to observe directly in the field and in particular in the deep-sea. Indirect methods such as molecular markers and virtual particle tracking are commonly applied to analyse genetic connectivity between organ isms (e.g. review by Cowen and Sponaugle, 2009; Baltazar-Soares et al, 2014; Breusing et al, 2016). To conduct virtual particle tracking, bio physical models based on a Lagrangian approach (i.e. individual particle tracking in space and time; Cowen and Sponaugle, 2009) are powerful

Methods

Results

Conclusion