What’s ashore? A fresh look at Kāpiti Intertidal

Department of Conservation —  29/07/2020

The intertidal rocky reefs of Kāpiti Island are full of life.  Last surveyed in 1968, these reefs have long deserved a fresh look, and recently we finally got the chance.

The sampling team gazes out from Rangatira Point on Kāpiti Island.
📷: GWRC/ Salt Ecology

Emma Hill and Megan Oliver explain how the shores of the Kāpiti Marine Reserve are as healthy as ever.

Intertidal rocky reefs are places of astounding biodiversity. The plants and animals that live there are used to changing conditions – they have evolved to cope with the heat of the sun, the powerful surge of waves, and the ebb and flow of food carried on the tides.

On Rangatira Point, two researchers run a transect line. This lets them count species numbers reliably across an area.
📷: GWRC/ Salt Ecology

Of New Zealand’s 15,000 kilometres of coastline, about two thirds are rocky reefs. Like subtidal reefs, intertidal rocky shores are very important. They generate food for many animals, provide shelter and habitat, and help regulate our climate. 

“Keeping intertidal reefs healthy is an important part of protecting our marine environment,” explains Emma. “It’s been fifty years since the rocky shores of Kāpiti Island were last investigated, and in 2019 we finally managed to survey them again.”

The recent surveys covered intertidal areas on Kāpiti and Mana Islands. The work was part of a collaborative project between the Greater Wellington Regional Council and DOC. The work was supported by DOC’s Marine Sentinel Sites Programme funded by Air New Zealand.

“Through ecological surveys, we can check reef health,” continues Emma. “The species we find tell us about changes in health over time. We can also compare remote reefs like those at Kāpiti to reefs nearer Wellington which are influenced by runoff from land.”

Intertidal rocky reefs are well understood. Decline in the number and variety of animals can warn us that human activities are harming the marine environment. Threats to reefs include fishing, trampling, pollution (from land runoff), invasive species, and the changing climate.

The Kāpiti Marine Reserve has been in place for almost 30 years and the surveys showed little difference between sites within and outside the marine reserve.

Dr Megan Oliver examines macroalgae (seaweed) coverage. Using a quadrant helps researched count accurately.
📷: GWRC/ Salt Ecology

“This reflects how healthy the area is,” explains Dr Megan Oliver, Marine and Freshwater Team Leader at GWRC. “Because the islands are remote, they are not impacted by human activities like development on land, stormwater run-off, or trampling by thousands of visitors. The 2019 surveys show similar plants and animals as those of 1968, which means the shore is still as healthy as it was 50 years ago. This is a great sign that despite ongoing development in the wider region, these offshore islands are still pristine.”

“As a result of these findings, we will continue to monitor these sites into the future as part of the GWRC coastal monitoring program. This will help us to understand how climate change impacts the distribution of plants and animals on intertidal rocky shores”.

The shore of Wharekohu Bay is home to these snails and many other invertebrates, and a stunning variety of seaweeds.
📷: GWRC/ Salt Ecology