Macroinvertebrate groups on deep-sea volcanic habitats in the Galapagos Marine Reserve in the Eastern Tropical Pacific Ocean: Mollusca

Study Extent

In June 2015, the EV Nautilus conducted a 10-day collaborative research expedition (NA064) between the Ocean Exploration Trust (OET), the Charles Darwin Foundation (CDF), and the Galapagos National Park Directorate (GNPD) to explore the deep-sea environments of the GMR. All methods were carried out in accordance with relevant guidelines and regulations by the GNPD under research permits PC-26-15 & PC-45-15. All experimental protocols were reviewed and approved by a GNPD’s committee that evaluates animal care during research activities. We conducted a total of six exploratory dives to the north, west, and central part of the Galapagos archipelago.

Sampling

ROV dives began at the base of each feature, and conducted a general upslope transect, following sonar and visual surveys along this transect. Dives H1435, H1436, and H1440 explored three seamounts around the most northern islands of the archipelago, which are part of the Wolf-Darwin volcanic lineament that extends to the Galapagos Spreading Center (Harpp and Geist 2002). All seamounts located in this area are conically shaped with small summit craters and relatively flat tops. These are also the youngest seamounts of the Galapagos platform estimated to be less than 1 million years old (Sinton et al. 1996; Harpp and Geist 2002). The deepest ROV transects were conducted during dives H1441 and H1442, which targeted the lava flows and abyssal plains to the west of Fernandina Island. These lava flows are part of the hotspot found beneath the island where the largest and most active volcano of the Galapagos platform is located (Sinton et al. 1996). The final dive, H1443, explored two small conically-shaped shallow seamounts located in the central part of the Archipelago, between the islands of Santiago, Isabela, and Santa Cruz. Seamounts from this part of the platform were once centred over the hotspot and are estimated to be between 5 to 6 million years old (Sinton et al. 1996; Harpp and Geist 2002).

Method steps

1. Each ROV dive ranged in duration from 11 to 18 hours. For the subsequent review of supposed morphospecies, each dive was split into 2-hour segments. In situ images of organisms were captured and extracted from video transects analyses using VLC software (Version 3.0.4) by “non-expert analysts”. To avoid reviewer bias in capturing unique morphospecies, “non-expert analysts” were assigned random video segments from all 6 ROV dives. Only organisms that appear to be larger than 3 cm were captured and considered for further identification. All images were then tentatively classified under their common names (i.e. squid, octupus etc.) and only images that appeared in sufficient detail to be determined beyond phyla were sent to taxonomic experts for further identification. The Open nomenclature identification qualifiers used are modified from Sigovini et al. (2016).

This dataset focuses on deep-sea molluscs found from 400 to 3400 m of depth within the Galapagos Marine Reserve.

1. Animalia
   rank: kingdom
2. Mollusca
   rank: phylum
3. Bivalvia
   rank: class
4. Cephalopoda
   rank: class
5. Gastropoda
   rank: class
6. Polyplacophora
   rank: class

This dataset focuses on deep-sea species found in the Galapagos Marine Reserve, which covers ~ 138,000 km2 and was established in 1998 to protect the archipelago’s marine biodiversity by banning large-scale commercial exploitation of marine resources (Henry et al., 2017).