Sediment and seabed species

Experiments have begun investigating the effect of sedimentation from human activities on offshore seabed species.

In May, researchers on NIWA’s research vessel RV Kaharoa collected dog cockles from 40m depth off the Taranaki coast near Patea.

The cockles were transferred to tanks in NIWA’s Marine Environmental Manipulation Facility (MEMF) in Wellington, where running seawater and environmental conditions can be precisely controlled and varied.

The dog cockles have ‘settled in’ so the first experiment starts today (4 July), and lasts for 6 weeks. The team has prepared specially-designed and built equipment they can use to vary the sediment concentration and particle size, and will measure how these factors affect the study animals.

“It’s fantastic to have the experiment up and running,” said Malcolm Clark, Project Leader. “The team has put a lot of work into setting everything up, from building and testing the equipment to collecting the samples, settling the animals in and checking that they’re healthy. Everything so far is working as planned, and we should have the first set of results in a few weeks’ time.”

What’s it for?

This two-year project is investigating the effects of suspended sediment from human activities such as mining and fishing on the health and survival of dog cockles and sponges in the South Taranaki Bight.

These are important species for this deep-sea ecosystem – they are the most abundant animals in parts of the area, forming ‘beds’ or ‘mats’ that provide habitat for other species. They have a widespread distribution, so the results will be relevant to other locations in New Zealand.

The findings will be useful for key stakeholders such as Māori, industry and environmental managers in understanding the effects of sedimentation on benthic communities (species living on, in or near the seabed), and enable acceptable threshold levels of sediment load and other mitigation measures to be developed during any extraction activities.

‘Sediment tolerance and mortality thresholds of offshore benthos’ is a project in Dynamic Seas. It is led by NIWA, collaborating with Victoria University.