This research was undertaken to investigate changes in assemblages of tropical benthic foraminifera along natural CO2 gradients at CO2 seeps in Milne Bay Province, Papua New Guinea.
Samples were collected during trips taken to seeps sites in August 2010 and April 2011. Locations included three seeps at Esa’Ala, Upa-Upasina, Dobu Island and as well as control sites at each location.
50 sediment samples were collected at various distances from the seeps, at depths of 4 to 15 meters. At each site, three haphazard samples were taken of the top 1cm of sediment, and pooled into one sample. Sediment was analysed for total carbon and nitrogen content, as well as arsenic concentrations.
Foraminifera were collected from the subsamples until 200 specimens per sample were obtained. For samples collected near the seep sites, this yield could not be obtained and all available sediment was searched. Foraminiferal taxa and abundances were determined for total density and diversity. A subsample of foraminifera was observed via Scanning Electron Microscopy (SEM) to identify signs of corrosion.
Temperature loggers were deployed at each site from April 2011 to April 2012. Seawater samples were collected in May and December 2012, and analysed for Arsenic and heavy metal pollutants.
Relationships between sediment chemistry variables, and foraminiferal total density and diversity, and density and diversity of individual groups were determined through linear models. Further methods of analysis included distance based redundancy and single factor permutational multivariate analysis of variance for patterns in assemblage composition and location, and significance of differences.
