COLONIZATION OF RAISED SUBSTRATE BY EPIBENTHIC FORAMINIFERA IN SEEP AND ADJACENT OFF-SEEP LOCATIONS OF HYDRATE RIDGE, OR

After one year on the seafloor at Hydrate Ridge in the Pacific, plastic coated wire was colonized by almost a thousand Cibicidoides wuellerstorfi. Interestingly, the wooden rod directly attached to the plastic coated wire that was heavily colonized was devoid of any epibenthic foraminifera. In the deep-sea, dense faunal assemblages have been observed colonizing biogenic structures that protrude from the sediment into the benthic boundary layer. It is thought that this behavior provides a hard substrate from which suspension feeders can attach. However, most understanding of colonization rates and patterns of benthic foraminifera come from shallow water experiments due to the ease of sampling and replication in the laboratory. The results of this study provide us with one of the only sources of information regarding colonization of raised substrates in the deep sea during a known time frame. Colonization cages within active methane seep habitats at Hydrate Ridge contained almost half (395 on four cages) as many individuals as those in adjacent off-seep sites (584 on three cages). This density difference may be due to differences in the habitat, including presumably difficult conditions that exist during active seepage events, or increased predation and displacement as a result of more abundant macro and meiofauna at active seep locations. Preliminary results suggest very similar values between seep and adjacent off-seep materials. Stable carbon isotopes from seep substrates range from 0.26‰ to -0.56‰ with an average of 0.03‰ while δ¹³C from off-seep substrates range from 0.39‰ to -0.26‰ with an average of 0.12‰. Stable oxygen isotopes of foraminiferal carbonate from seep substrates range from 2.70‰ to 2.03‰ with an average of 2.41‰ and 2.65‰ to 2.29‰ with an average of 2.40‰ at adjacent off-seep sites.