dissertation

Ph.D. Research in Ken Smith's Lab at Scripps Institution of Oceanography

The ecology of glass sponge "communities" in the abyssal NE Pacific

My research in the Smith lab focused on the relationship of suspension feeders to flow (and food supply) at an abyssal time-series station in the NE Pacific (Sta. M). My dissertation involved three main projects: 1) evaluating the diversity and vertical zonation of organisms living on stalked organisms (esp. the glass sponge Hyalonema) above the sediment surface; 2) examining the near-bottom flow; and 3) characterizing the near-bottom, suspended particulate matter as well as the phytodetritus aggregated on the sea floor at the abyssal station. I prepared a poster about my dissertation research for the 1999 DIALOG Symposium. You can read the abstract to my dissertation below. Full text of my dissertation is available at the University Microfilms website.

Publications related to my Ph.D. research:

· Beaulieu, S.E. (2001) Life on glass houses: sponge stalk communities in the deep sea. Marine Biology 138(4): 803-817. PDF

· Beaulieu, S.E. (2001) Colonization of habitat islands in the deep sea: recruitment to glass sponge stalks. Deep-Sea Research I 48(4): 1121-1137. PDF

· Winston, J.E. and S.E. Beaulieu. (1999) Striatodoma dorothea (Cheilostomatida), a new bryozoan from deep water off California. Proceedings of the Biological Society of Washington 112(2): 313-318.

· Beaulieu, S. and K.L. Smith Jr. (1998) Phytodetritus entering the benthic boundary layer and aggregated on the sea floor at an abyssal station in the NE Pacific: macro- and microscopic composition. Deep-Sea Research II 45(4-5): 781-815. PDF

· Beaulieu, S.E. and R.J. Baldwin (1998) Temporal variability in currents and the benthic boundary layer at an abyssal station off central California. Deep-Sea Research II 45(4-5): 587-615. PDF

In order to collect the "stalk communities" (i.e. the sponge stalks and associated epizoites) and the phytodetritus from the sea floor at 4100 m depth, we used the submersible Alvin:

In this photo, I am sitting atop the Alvin in its hangar on the research vessel Atlantis II. I am downloading data from a CTD (conductivity, temperature, and depth recording instrument) onto a notebook computer. In this photo, I am securing tube cores onto the Alvin basket prior to a dive.

Abstract of my dissertation:

The ecology of glass sponge "communities" in the abyssal NE Pacific

The stalks of hexactinellid sponges in the genus Hyalonema provide hard substrate in soft-bottom, deep-sea environments. The goal of this research was to describe the epifaunal communities of these "stalks" and their physical environment in the abyssal NE Pacific. Several projects were conducted to determine the biological and physical factors influencing the vertical distribution of attached fauna.

In photographic transects, stalks appeared to be covered with suspension feeders. Examination of stalks collected intact from the sea floor revealed that the communities were species-rich, with diverse trophic modes represented. Vertical distributions of most taxa extended over a wide range in height above the sea floor. The distributions of smaller, solitary fauna and certain functional groups of colonial organisms were restricted by sheet and mound-like colonial cnidarians that were dominant space competitors.

Results of an experimental study using artificial Hyalonema stalks indicated that the abundance of fauna in stalk communities is maintained by frequent recruitment of individuals in a few common taxa and infrequent recruitment of many rare taxa. Vertical distributions of foraminiferan recruits were skewed towards the top of the artificial stalks, likely due to behavior.

The physical environment of the stalk communities was examined in terms of the components of advective "food" flux: flow velocity and organic particle concentration. The gradient in the near-bottom flow environment was estimated from long-term records and measured directly with in situ flow visualization. Although the magnitude of flow at the level of the stalk communities was weak (on average < 2 cm s^-1), the average gradient in flow (calculated from log layer profiles) was such that flow at 50 cm would be twice that at 5 cm above the sea floor. Intact phytoplankton cells, potential food for members of the stalk communities, were found in phytodetritus entering the benthic boundary layer, suspended at ~1 m above bottom, and deposited on the sea floor, suggesting rapid transfer from surface waters to abyssal depths.

Overall, biological interactions appear to be most important in structuring the Hyalonema stalk communities. However, some patterns observed for suspension feeders are potentially a response to a gradient in advective food supply.

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Page revised 10 Mar 2006 by Stace Beaulieu