Ali Rhoades
Determining variation in biological community structure due to environmental stressors around hydrothermal vent systems of Brothers volcano, Kermadec Arc, New Zealand
Studies of hydrothermal systems have shown that their biological community structure is highly affected by physical and chemical ocean processes that are characteristic of hydrothermal vent environments. In the Southern Kermadec Arc, Brothers volcano contains two side-by-side vent sites with differing chemical concentrations and physical properties, making them ideal sites for assessing the effects these processes have on groups of fauna. In this study, a photographic survey of the biological communities within the two plume fields of Brothers was conducted, and manual and automated image analysis was performed, to determine whether groups of fauna differ in species density and composition between the two sites. Eight dominant types of organisms were tabulated, each of which were assessed for relationships with four potential environmental stressors: temperature, Eh levels (a substitute for chemical concentrations in the water column), salinity (salt content in the water column), and turbidity (suspended particles in the water column). Observed relationships suggest that three of the four factors significantly effect which species are able to live in particular areas. Temperature and Eh produced the same relative effects on vent specialized and non-vent specific organisms. Crustaceans (shrimp, crabs, and long-necked barnacles) were disproportionately found in strongly vent-influenced areas with high temperatures and low Eh levels. They were also associated with areas of high turbidity caused mainly by particles in vent fluid. Poriferans (sponges) and Hydrozoans (hydroids) were found at lower temperatures and higher Eh levels, properties generally found further from a vent source. Salinity did not appear to have major effects on groups of fauna. These environmental conditions are constantly changing, making hydrothermal vent systems extremely variable environments and requiring fauna inhabiting vent areas to be adaptable to these environmental stressors in order to survive in these extreme systems.