Filling Biodiversity Knowledge Gaps: Sponges (Porifera: Demospongiae) Recorded off San Jorge Gulf (Argentina), SW Atlantic Ocean

In Argentina, our knowledge on the biodiversity of marine Porifera is closely related to the concentration of the sampling effort. Coastal areas such as Buenos Aires and Tierra del Fuego have several records, while the majority of the continental shelf have few or no records at all. In December 2020, the RV “Victor Angelescu” performed a regular stock assessment expedition in order to evaluate the population of the Argentinean squid Illex argentinus off San Jorge Gulf (44°S-46°S, 84m-114m). Sampling was designed using bottom trawls. At 23 random sampling sites, the invertebrate by-catch was preserved frozen and studied at the Benthos Laboratory of the INIDEP. According to our knowledge, there are no specific records of sponge species in this area, only sparse mentions as a general group in technical reports. Our results showed that sponges were conspicuous and abundant components in the benthic communities of the area. They represented up to 40% of the total invertebrate bycatch (with an average value of ~130 kg.mn² per site). Surprisingly, the species Tedania (Tedaniopsis) mucosa Thiele, 1905 was found to be dominant in the area and was recorded in 22 sites, reaching up to 34 % of the wet biomass (average of ~100 kg.nm²). Other recorded species belong to the genera Isodictya, Iophon, Clathria, Haliclona, Tedania and Siphonochalina. The results of this study contribute to fill in the gaps on the distribution of the sponges in the continental shelf of Argentina.