DISSERTATION Diversity and distribution patterns of deep-sea polychaetes (Annelida) in the tropical Atlantic Theresa Guggolz Diversity and distribution patterns of deep-sea polychaetes (Annelida) in the tropical Atlantic DISSERTATION With the aim of achieving a doctoral degree (Dr. rer. nat.) at the Faculty of Mathematics, Informatics and Natural Sciences Department Biology of the Universität Hamburg submitted by Theresa Margarete Guggolz Hamburg 2019 First supervisor: Prof. Dr. Matthias Glaubrecht Second supervisor: Prof. Dr. Angelika Brandt Disputation: 12. August 2019 CONTENTS Contents CHAPTER 1 Introduction................................................................. 1 I. The deep sea ..................................................... 1 II. Diversity in the deep sea .......................................... 3 III. Distribution patterns in the deep sea ............................... 4 IV. Deep-sea polychaetes ............................................. 6 V. Challenges in the identification of deep-sea polychaetes ............ 9 VI. Aims and hypotheses ............................................ 10 VII. Summary ....................................................... 11 CHAPTER 2 Composition of abyssal macrofauna along the Vema Fracture Zone and the hadal Puerto Rico Trench, northern tropical Atlantic ....................... 14 CHAPTER 3 Biodiversity and distribution of polynoid and spionid polychaetes (Annelida) in the Vema Fracture Zone, tropical North Atlantic ........................... 26 CHAPTER 4 Diversity and distribution of Laonice species (Annelida: Spionidae) in the tropi- cal North Atlantic and Puerto Rico Trench ................................. 38 CHAPTER 5 High diversity and pan-oceanic distribution of deep-sea polychaetes: Prionospio and Aurospio (Annelida: Spionidae) in the Atlantic and Pacific Ocean .................................................................... 52 CHAPTER 6 Diversity, pan-oceanic and vertical distribution of deep-sea scale worms (An- nelida: Polynoidae: Bathypolaria) ......................................... 72 Theresa Guggolz CHAPTER 7 General Discussion ...................................................... 86 I. Biodiversity of deep-sea polychaetes ............................. 86 II. Rare species in the deep sea ..................................... 91 III. Distribution patterns in the tropical Atlantic ........................ 93 IV. Pan-oceanic distribution patterns ................................. 98 V. Importance of differentiation of polychaete species ............... 100 VI. Conclusion .................................................... 101 Acknowledgements ................................................... 104 Affirmation in lieu of oath..............................................105 Author contributions statement.........................................106 References ........................................................... 108 CHAPTER 1 Introduction CHAPTER 1: Introduction Introduction I. The deep sea For a long time, the deep sea was considered to be a monotonous environ- ment, with no light and most probably uninhabitable for any life (e.g. McClain and Hardy 2010, Ramirez-Llodra et al. 2010). This general view did not fun- damentally change until the early nineteenth century (Snelgrove and Smith 2002), followed by the first systematic sampling of this unexplored ecosystem initiated about 147 years ago with the Challenger Expedition (Gage and Ty- ler 1992). Decades of improving and refining sampling techniques and meth- ods drastically changed the original assumptions towards recognizing that the deep sea is the largest ecosystem on earth with high faunal diversity and a complex ecology (e.g. Hessler and Sanders 1967, Sanders and Hessler 1969, Grassle and Maciolek 1992, Snelgrove and Smith 2002, Rex and Etter 2010). The deep sea constitutes around 90 % of the oceans covering two thirds of the plan- et’s surface (Ramirez-Llodra et al. 2010, Harris et al. 2014). Despite the vast expanse of the deep sea, only a small proportion (< 0.1 %) has been studied and sampled to date (e.g. Ramirez-Llodra et al. 2010, Rex and Etter 2010, Danovaro et al. 2017). In general, the parts of the oceans starting at the edge of the continental margins and lying below 200 m depth are defined as deep sea (Gage and Tyler 1992). This area again is divided in three depth zones, the bathyal (~200 – 4,000 m), the abyssal (4,000 – 6,000 m) and the hadal (> 6,000 m) (Jamieson 2015). The benthic bathyal accounts for around 15 % of the World Ocean area (Harris et al. 2014) and comprises continental slopes and rises, but also seamounts and mid-ocean ridges (Zezina 1997). The bathyal zone is described to be heteroge- neous regarding factors like sediments, hydrostatic pressure, temperature and food-supply, mainly caused by the steepness of the habitat, decreasing towards the abyssal (Thistle 2003, Ramirez-Llodra et al. 2010, Harris et al. 2014). Almost independently from processes taking place in the benthic zones, the bathypelag- ic represents an ecosystem, covering a large proportion of the deep ocean vol- ume (~75 %) (Robison 2004, Ramirez-Llodra et al. 2010). The deepest parts of the ocean, the hadal, is represented almost exclusively by trenches (Jamieson et al. 2010, Jamieson 2015) and accounts for less than 1 % of global benthic deep- sea areas (Harris et al. 2014). Usually, hadal trenches are V-shaped, very nar- row with steep slopes up to 45° or more (Ramirez-Llodra et al. 2010, Jamieson 1 Theresa Guggolz 2015) and an extreme topographic complexity (Beliaev and Brueggeman 1989), resulting in a heterogeneous environment. Sediment, plant debris and surface derived material is transported downwards the steep slopes, accumulating along the trench axis (Danovaro et al. 2003, Romankevich et al. 2009), with the trench acting like a sedimentation tank, physically capturing the material at these depths and resulting in high sedimentation rates (Jamieson et al. 2010, Jamieson 2015). Despite the heterogeneous environment, factors like temperature are described to be stable (Beliaev and Brueggeman 1989), mainly affected by the hydrostat- ic pressure that is one of the most important factors in such depths (Jamieson 2015). The largest component of the deep sea are the abyssal basins (~85 % of global ocean’s surface area, Harris et al. 2014), mainly represented by extensive abyssal plains (Ebbe et al. 2010, Ramirez-Llodra et al. 2010). These abyssal plains are interconnected and remarkably flat, on average with less than 1 m change in heights over a distance of 1 km, with a thick layer of fine, soft sediment covering most of the underlying topography (Smith et al. 2008, Ramirez-Llodra et al. 2010, Harris 2012). Although it has to be considered that the abyssal soft sed- iment is derived from terrigenous particles (weathering rocks), which are trans- ported into the ocean through rivers and wind resulting in a decreasing rate of supply and particle size with increasing distance from land (Thistle 2003). Even though the abyssal appears monotonous, it is a dynamic environment, experi- encing regular and episodic disturbances like tidal currents and benthic storms (e.g. Tyler 1988, Ebbe et al. 2010, McClain and Hardy 2010, Ramirez-Llodra et al. 2010). The abyssal plains are interrupted by geological features like mid- ocean ridges, seamounts and abyssal hills, formed by geologically active zones (e.g. Harris 2012). These geological features are representing among others (e.g. manganese nodules, mollusc shells, mussel beds and corals) hard-bottom habitats (Thistle 2003, Young 2009, Ramirez-Llodra et al. 2010). One main factor all three zones of the deep sea have in common is the absence of light for photo- synthesis, resulting in heterotrophic environments (Thistle 2003, Ramirez-Llodra et al. 2010). Accordingly, energy in the deep sea is extremely limited and de- pendent on primary production in the euphotic zone, with some exceptions like hydrothermal vents (Thistle 2003, Smith et al. 2008, Ramirez-Llodra et al. 2010). The so-called particulate organic carbon flux is thought to be mainly responsible for the food availability in the abyss, compromising a complex mixture of organic material and detritus (e.g. Smith and Demopoulos 2003, Buesseler et al. 2007, Smith et al. 2008). Other abiotic factors are relatively constant. The water in the deep sea is lying under a thermocline and temperatures are slightly varying around 2 °C with some exceptions, the salinity is almost always ~35‰ and in 2 CHAPTER 1: Introduction areas with constant circulating currents the dissolved oxygen is near saturation (5–6 ml l-1) (Thistle 2003, Ramirez-Llodra et al. 2010, Jamieson 2015). The hydrostatic pressure is increasing linear with depth (1 atmosphere for every 10 m depth), representing a continuous gradient essentially influencing adaptions to the deep sea (Thistle 2003, Ramirez-Llodra et al. 2010, Jamieson 2015). Unique habitats that are essentially differing to these common deep-sea habi- tats are chemosynthetic systems like hydrothermal vents and cold seeps. They are usually found along active mid-ocean ridges, continental margins and back- arc spreading centres (Van Dover 2002, Tunnicliffe et al. 2003, Govenar 2010, Ramirez-Llodra et al. 2010). The energy sources of these ecosystems are mainly influenced by chemical reactions of very hot (up to 407 °C) or cold fluids, originating from geological processes, with seawater. During these reactions, chemicals that are charged in the leaking fluids like sulphide,