Methane seeps as refugia during ash falls in the Late Cretaceous Western Interior Seaway of North America

Methane seeps host rich biotic communities, forming patchy yet highly productive ecosystems across the global ocean. Persistent hydrocarbon emissions fuel chemosynthetic food webs at seeps. Methane seeps were abundant in the Western Interior Seaway of North America during the Late Cretaceous. This area also experienced intermittent ash falls, which negatively impacted the marine fauna. We propose that methane seeps acted as refugia during these environmental perturbations. We report a laterally continuous bentonite within the upper Campanian Baculites compressus Zone of the Pierre Shale in southwestern South Dakota (USA) that fortuitously cuts across a methane seep deposit. We compare the macroinvertebrate record below and above the bentonite at seep and non-seep sites. Our results reveal that the paleocommunity (measured by abundance and diversity) was largely unaffected by the ash fall at the seep site, whereas it was significantly altered at the non-seep site. Thus, methane seeps in the Western Interior Seaway may have provided refuges or served as oases in the aftermath of severe environmental perturbations.

The occurrence of the parasitic amphipod Trischizostoma crosnieri Lowry & Stoddart, 1993 (Amphipoda: Amphilochidea: Lysianassida) in a methane seep site in the southeastern Pacific

The genus Trischizostoma Boeck, 1861 is a cosmopolitan group of parasitic and symbiotic aristoidean amphipods whose distribution is poorly known, with scarce specimens reported principally from pelagic environments until 3655 m depth. In this note, Trischizostoma crosnieri Lowry & Stoddart,1993, a species described for the southwest Pacific, is recorded for the first time in the southeast Pacific. The species was known previously only from a female specimen, described from the Philippines, with two additional unpublished records from the east coast of Australia and Tasmania. The specimens studied herein were obtained at 874 m depth, 36 nm to the northwest of Concepción, Biobío Region, in a methane seep site. However, the relationship between this species with this particular habitat is still uncertain. The genus Trischizostoma has been cited for the Nazca and Salas y Gómez ridges; nevertheless, our finding constitutes the first record of a species at the continental margin off Chile, raising to four the known species of the genus for Chilean waters.

Life-Long Coral Skeletal Acclimatization at CO2 Vents in Papua New Guinea Reveals Species- and Environment-Specific Effects

The responses of corals and other marine calcifying organisms to ocean acidification (OA) are variable and span from no effect to severe responses. Here we investigated the effect of long-term exposure to OA on skeletal parameters of four tropical zooxanthellate corals living at two CO2 vents in Papua New Guinea, namely in Dobu and Upa Upasina. The skeletal porosity of Galaxea fascicularis, Acropora millepora, and Pocillopora damicornis was higher (from 17% to 38%, depending on the species) at the seep site compared to the control only at Upa Upasina. Massive Porites showed no differences at any of the locations. Pocillopora damicornis also showed a ~ 7% decrease of micro-density and an increase of the volume fraction of the larger pores, a decrease of the intraskeletal organic matrix content with an increase of the intraskeletal water content, and no variation in the organic matrix related strain and crystallite size. The fact that the skeletal parameters varied only at one of the two seep sites suggests that other local environmental conditions interact with OA to modify the coral skeletal parameters. This might also contribute to explain the great deal of responses to OA reported for corals and other marine calcifying organisms.