Settlement of juvenile glass sponges and other invertebrate cryptofauna on the Hecate Strait glass sponge reefs

Abstract

Glass sponge reefs are endemic to the continental shelf waters of British Columbia and Alaska, where they form complex three-dimensional habitats used by a variety of commercially important fish and invertebrate species. The Hecate Strait and Queen Charlotte Sound Glass Sponge Reefs Marine Protected Area (HSQCS-MPA) was designated in February 2017 to protect 2,410 km 2 of reef habitat. Efforts to establish baseline information regarding reef-associated taxa in the new MPA have documented the diversity of megafauna in detail, but little is understood of the cryptic epifauna inhabiting hidden crevices within the reefs, and even less is understood of larval recruitment, the key reproductive process maintaining long-term reef health and stability. We collected specimens of a reef-building glass sponge, Farrea occa, from the HSQCS-MPA and described the diversity of their epifauna. Five hundred and two organisms from six phyla were documented, including 84 sponges from three classes. We found several glass sponges: known juvenile reef builders (two Aphrocallistes vastus and two Heterochone calyx); the lyssacine sponge Leucopsacus scoliodocus, previously known in Canadian waters only from Jervis Inlet; and an unidentified dictyonine sponge previously unknown to waters of British Columbia. Also present were the carnivorous sponge Lycopodina occidentalis, 11 individuals of Desmacella austini, evidence for a new species in the subgenus Haliclona (Flagellia), and a clathrinid calcareous sponge. The growth stages we observed suggest multiple settlement events by glass sponge larvae between February and early March. Of the 502 invertebrates, 460 were attached to dead sponge skeleton despite live tissue being much more available as substrate. This study highlights trends in recruitment at sponge reefs, explores factors that may affect larval settlement, describes new sponge associations, and provides the first description of the range of macrofauna found on glass sponges, acting as a baseline for continued monitoring of the MPA. K E Y W O R D S glass sponge reef, Hexactinellida, marine protected area, Porifera, recruitment

Sponge Density and Distribution Constrained by Fluid Forcing in the Deep Sea

“…The reduction in flow speed at the sea floor due to the boundary layer could potentially lead to an increase in larvae deposition and recruitment (Abelson and Denny, 1997). The deposition and retention of larvae in the sponge ground should increase with lower flow speeds, and larvae attachment rates should also increase due to reduced flow stress (Mariani et al, 2006; Guillas et al, 2019). An increase in larvae deposition and retention impacts the recruitment of new individuals within the sponge grounds and should increase its ability to grow and recover from damage.…”