Overnight tipping points from a cataclysmic event: impacts, recovery and constraints on rocky reef ecosystems (innovation fund)

Kaikoura's coast was uplifted by the November 2016 earthquakes

The uplift of Kaikoura’s coastline due to the November 2016 earthquakes caused an unprecedented loss of kelp forests, which provide habitat and energy for other species. This project is investigating the long-term resilience of kelp thrust into shallow water in the subtidal zone, and the potential mechanisms affecting canopy expansion, colonisation and survival. This will help determine which kelp beds are likely to recover, the environmental conditions likely to promote recovery, and which beds are vulnerable to further decline.

Project leader: Leigh Tait, NIWA

Investigating the recovery of Kaikoura's coastal kelp forests

The November 2016 earthquake lifted around 50km of Kaikoura’s coastline, causing an unprecedented loss of kelp forests that provide habitat and energy for other species. This event will significantly affect nutrient cycling, primary productivity and overall functioning of nearshore ecosystems in what was one of New Zealand’s most productive coastal zones.

In New Zealand the recovery of kelp forests can be very slow, especially if disrupted by sediment and/or colonisation by turfing algae. Healthy kelp bed ecosystems maintain themselves through positive-feedback cycles that inhibit the growth of turfing algae and buffer sediment from being resuspended by wave action. However, negative feedback loops associated with turfing algae can develop if environmental conditions degrade, which can be triggered by kelp loss due to natural events such as storms.

Because extensive reef areas on Kaikoura’s coast are now devoid of kelp and dominated by turfing species, recovery of the habitat-forming kelp forests is threatened – especially in areas of high sedimentation.

We are assessing changes in how much light is penetrating the water in three regions along Kaikōura’s coast that have differing levels of sedimentation and varying populations of surviving kelp: southern region – Oaro to Hikurangi Marine Reserve; central region – Kaikōura Peninsula; northern region – Waipapa Bay and Okiwi Bay. This work complements what MPI is doing.

To assess how abundant – and healthy – the remaining kelp forests are, we are using novel equipment to measure the metabolism of the kelp forests, and protocolsto assess the long-term health and resilience of key species in the affected areas.

This will enable us to determine the long-term resilience of kelp thrust into shallow water in the subtidal zone, as well as determine the potential mechanisms affecting canopy expansion, colonisation and survival. We are:

  • Quantifying the effects of kelp loss on carbon cycling
  • Assessing differences in water clarity within and between areas, and the implications for kelp bed resilience and recovery
  • Estimating critical tipping point thresholds
    associated with reduced buffering due to kelp loss

This information will help determine which kelp beds are likely to recover, the environmental conditions likely to promote recovery, and which beds are vulnerable to further decline. Where mitigation is possible and practical we will recommend measures to limit further damage (eg, by restricting or changing human activities that contribute to sedimentation).

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