A Suspended Particle Rosette Sampler for Investigating Hydrothermal Plumes

Abstract

We have developed and are building a new oceanographic tool, a Suspended Particulate Rosette (SUPR) sampling system. The SUPR sampler is capable of rapidly filtering 25 large water volume samples (30 to 100 liters per sample) for suspended particulates during a single deployment. In addition, the SUPR sampler is designed to be compatible with in situ optical analysis methods. We are developing the SUPR sampler to investigate these fundamental questions, How do iron- and manganese-rich, hydrothermal plume particles affect seawater chemistry and to what extent do these particles fuel microbial activity in deep-sea hydrothermal plumes? While past studies have determined the average chemical composition of hydrothermal plumes we lack the detailed information we need to understand the complete formation process and to what extent plume particle chemistry is modified by reactions with seawater and chemosynthetic organisms. Key to answering these questions is understanding the spatial and temporal variability of plume particle composition and mineralogy. Examination of this complex system requires the collection of numerous, spatially-discrete particle samples from hydrothermal plumes. Existing systems collect only a single combined sample - this has been the major obstacle to addressing our research questions. The SUPR sampler is designed to address this sampling need. It consists of a custom filtering head capable of sequentially collecting 25 discrete samples or 10 replicate pairs. This filtering head is interfaced with an 8 to 30 liter per minute pumping system. It can be deployed on a CTD rosette for spatially-discrete tow-yo sampling of non-buoyant hydrothermal plumes, on an ROV (e.g. Jason) for sampling rising plumes, or mounted on a fixed mooring in a hydrothermal vent field for time series sampling. In addition the SUPR sampler is designed with a long-term perspective for seafloor observatory deployments where it can be used to collect particulate samples as time series and in response to tectonic (or other) events. We see an increasing demand for this capability - enabling both spatially-resolved and, importantly, temporally-resolved sampling of suspended particulates or microbes from a range of dynamic biogeochemical environments, not just hydrothermal systems. With such future applications in mind, and because many particle characteristics are short lived, the SUPR sampler has been designed to be compatible with in situ optical sensors based on visible and laser spectroscopy.