Private links to watch again previous seminars can be given upon request, if authorized by the speakers, at early_career@dsbsoc.org.
15 September 2026 – Abyssal/Hadal seafloor biodiversity
Alfredo Marchio (Minderoo-University of Western Australia Deep-Sea Research Centre)
A morphological classification of glass sponges (Porifera: Hexactinellida) for image-based assessments of deep-sea assemblages
Abstract: Glass sponges are key components of benthic deep-sea communities, but their diversity and distribution remain poorly known in abyssal and hadal environments. Here, we used observations collected over a decade to create a standardized morphological classification system, comprising 11 morphological categories and designed for annotation of glass sponges by non-taxonomists. We assessed our system against taxonomic descriptions, ensuring that each genus could be assigned to at least one morphological category; only three poorly described genera remained of uncertain morphology. We then applied the system to our own dataset of observations, recording glass sponge assemblages from the eastern Pacific Ocean, the Nova Canton Through, the Tonga Trench, and the South Shetland Trench, covering the bathymetric range 2000 – 7000 m. The dataset comprised almost 3000 glass sponges and 190 morphotypes. For each observation, substrate type and slope were annotated, providing a descriptive assessment of seafloor-morphology relations. The highest number of sponges was recorded in a single dive over a nodule field, on the eastern Pacific abyssal plains between 4200 and 4400, with observations markedly decreasing below 5000m. By contrast, morphological diversity peaked on rocky substrates, distributed across a broader portion of the surveyed bathymetric range. Laminar sponges were the most common in our dataset, dominating the East Pacific nodule field, but were notably absent from most of the other dives. Stalked sponges, the second most frequently observed morphology, were more geographically widespread, whereas less common morphologies were unevenly distributed in the four regions. These results show how a taxonomy-based classification system can be used to describe patterns of glass sponge morphological diversity from video material without intensive taxonomic training. Although physical specimens are still required for taxonomic identification, our framework allows non-taxonomists to annotate video material consistently in poorly studied regions, where baseline knowledge of the local biodiversity is limited or absent.
Erika Gress (Hong Kong Baptist University)
A deep dive into Antipatharians (black corals): Diversity, taxonomy, and evolution in the deep sea
Abstract: Antipatharians (black corals) remain one of the least studied coral groups, with major gaps in our understanding of their diversity and evolution. In this seminar, I will first provide a brief introduction to antipatharians and the challenges surrounding their taxonomy and systematics. I will then present recent advances in Antipatharia systematics using an integrative approach combining morphology, phylogenomics, and genomic distance analyses. Focusing on deep-sea specimens from the North Pacific high seas and New Zealand, I will discuss the description of a distinctive lineage of black corals that grows in association with hexactinellid sponges, resulting in the establishment of a new family, a new genus, and two new species. I will also introduce the first genomic distance framework developed for Antipatharia and discuss how these approaches can improve our understanding of diversity, species boundaries, and evolutionary history within the order.
