Larval Settlement Project and Volunteer Divers 2020 by Sheila Byers

Larvae of the cloud sponge, Aphrocallistes vastus, the key reef-building species in Howe Sound (partnered with the fingered goblet sponge, Heterochone calyx), are known to disperse and mix genetically across the sponge reefs in the Salish Sea. But where are these larvae?

Not only are the larvae microscopic and difficult to see or find, little is known about sponge reproduction and recruitment in general. Unveiling some of these natural history mysteries of the cloud sponge are critical indicators of the conservation potential for the recovery of damaged sponges in the reefs. In 2016, MLSS initiated a collaborative project with research scientists from the Pacific Biological Station, Nanaimo to conduct a field experiment in hopes of throwing some light on the missing links.

The larval settlement plate ‘trees’ were installed in 2017 and the experiment ran for one year. Sadly, no hexactinellid sponge larvae settled on the plates although demospongia larvae did recruit. A total of 70 invertebrate taxa representing 10 phyla recruited to the settlement plates with four major phyla: marine worms, moss animals, colonial hydroids (relatives of sea jellies), bivalves and gastropods.

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The experiment provided the first report of invertebrate settlement on a sponge reef in the Salish Sea and the first settlement plate study at these depths in BC. The results provided a description of larval settlement timing in the Northeast Pacific for 17 taxa of the recruited species and elucidated the potential spawn time for 2 of the marine worm species. Important knowledge gaps influencing reef-building sponge recruitment in Howe Sound were revealed in this study that reinforces effective ecosystem-level conservation.

Divers involved with this project:

We would like to thank the MLSS and the UCBC divers who volunteered their time for this project:

 

Dive Team Leaders: Glen Dennison and Lora Tryon 

Team Photographers: Deirdre McCracken, Diane Reid, Chris Straub, Adam Taylor.

Installation and retrieval divers: Meagen Abele, Brendan Andresen, Fabiola Ruiz Aguilar, Philippe Beaudry, Bobby Chan, Scott Dowd, Marley Heron, Rahim Kaba, Cassandra Konecny, Viviana Lee, Lauren Liggan, Scott Meixner, Amy Morgan-Young, Tanya Prinzing, Bartek (Bart) Radziej, Joshua Teerling.

Find Canadian Field Naturalist 2020 publication here: https://doi.org/10.22621/cfn.v134i1.2297

Full-length video of MLSSBC and DFO – Settling Plate Project: https://youtu.be/PCih0RqqO3s

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