Background to the Rumble III seamount survey

Background to the Rumble III seamount survey

Seamounts are prominent features of underwater topography in the New Zealand region. They are often sites of high productivity, and the focus of important commercial fisheries. Research to date has been mainly directed at measuring the biodiversity of benthic invertebrate fauna on a variety of seamounts spread throughout the EEZ or investigation of the effects of bottom trawling (e.g. the Graveyard survey).

However, this trip will change focus and examine some of the processes associated with seamount function and ask questions such as:

• What effect does the seamount have on the water column?
• What effect does the seamount have on the plankton assemblages?

Seamounts can have complex effects on ocean current circulation. These are often poorly understood because of the large variety of seamount sizes, shapes, distribution (e.g. chains or isolated), and highly variable current flow and water column stratification. Seamounts can deflect large scale currents, but also have localized effects such as the formation of trapped waves, reflection, amplification or distortion of internal waves, and amplification of internal tides – all of which can affect local animals.

This trip will focus on only one seamount but examine it in great detail. Our research vessel Tangaroa will visit Rumble III seamount, situated at the southern end of the Kermadec Ridge, about 160 n.miles NE of the port of Tauranga. It is an elongated seamount with the main cone comprising a peak and a caldera to the northwest. Its summit is about 200 m water depth, and hydrothermal vent activity has been recorded from the cone area through both plume detection and through sampling of hydrothermal vent animals.

To understand more fully the dynamics of Rumble III we will use a variety of techniques throughout the trip. These will be discussed in greater detail by the scientists on board the Tangaroa - by the end of the trip you will know your MOCNESS from your ADCP moorings as well as how to sample the water column from 10 m to 3000m.