Ecosystem response to elevated arsenic concentration

The shallow-water submarine hot springs near Ambitle Island, Papua New Guinea afford an ideal opportunity to investigate the response of benthic diversity, activity, and biogeochemistry of microorganisms, foraminifera, and infaunal invertebrates to arsenic.

The aim of the proposed research is to sample and analyze vent fluid, seawater, and sediment on Ambitle Island from sites of high and low arsenic concentrations over a 4-year period. Analyses will include an extensive suite of inorganic aqueous species, isotopes and dissolved organic carbon from pore fluids and the water column. In addition, microbial, foraminiferan, meiofaunal, and macrofaunal invertebrate diversities and community structures will be investigated in the sediments using morphological, isotopic and PCR-based molecular methods.

The goal of this study seeks to answer seven first-order questions with respect to arsenic cycling in the hydrothermal system at Ambitle Island:

• What is the source for the arsenic and what conditions lead to its accumulation in the sediment?

• Is the arsenic in Tutum Bay sediments available for biological processes?

• How diverse are the microbial community structures at the sites, and how do these correlate with variations in chemical composition, especially arsenic levels?

• What are the growth characteristics of arsenic-tolerant or arsenic-metabolizing mesophiles and thermophiles in Tutum Bay, and how to geochemical energy sources constrain their activity?

• What effect do elevated arsenic values have on taxonomic diversity of benthic fauna in Tutum Bay sediments?

• What are the major geochemical and biotic differences between the dry and wet season?

• Can we mathematically describe and predict benthic diversities relative to arsenic concentrations in Tutum Bay?