The secrets of the Poor Knights Sponges

The Victoria University of Wellington Sponge Ecology Group, led by Associate Professor James Bell, recently visited the Poor Knights Islands Marine Reserve to uncover the secret life of sponges in New Zealand water environments.

research vessel in poor knights island

In collaboration with local tourist operators Dive! Tutukaka, and with permissions from the Department of Conservation and the Ngatiwai Trust, the group conducted a series of dives around the reserve recording the diversity and abundance of more than 60 different sponge species.

“The Poor Knights Marine Reserve has been described as having a very high diversity of sponges, but nothing was known about their ecology or how they contribute the way shallow water environments in New Zealand function,” says Associate Professor Bell.

The group found that sponges occupy over 50 percent of the available rock in some areas of the reserve, which is high in comparison to areas the group has previously studied on Wellington’s South Coast.

Associate Professor Bell says that the contribution that sponges make to the overall seabed ecosystems is New Zealand is likely to be vastly underestimated, especially in the areas below 30-40 meters where there is no light to support algae which compete with sponges.

“Sponges are some of the most primitive organisms, and in the waters around New Zealand they pump vast volumes of water through their body, stripping food particles and nutrients, having a major influence on energy flow.

“To understand how our coastal ecosystems work and how to protect them we need to understand the contributions made by all the different organisms, and how they interact with each other. Our research is focused on filling these gaps for sponges.”

Dive! Tutukaka provided one-of-a-kind access to dive sites and shared their vast knowledge of the local area with the team, helping them to understand the role that sponges play in the coastal environments of New Zealand.

A series of physiological experiments of the sponges were also conducted to understand how seasonal changes in water temperature affect the sponges, in order to predict how they might respond to climate change.

This work is part of a larger research programme led by Associate Professor Bell which investigates the impact of environmental change on sponges.

Victoria hosts one of the largest sponge ecology groups in the world and the team will be making further trip to the Poor Knights Islands Marine Reserve in coming years.

Associate Professor Bell is a keynote speaker at the World International Sponge Conference in Ireland in June.