A 2013 workshop Future proofing New Zealand’s shellfish aquaculture: Monitoring and adaptation to ocean acidification, brought together experts from government, the aquaculture industry and science organizations from the US and NZ to raise awareness of ocean acidification within the NZ aquaculture community, identify ways to protect the aquaculture industry and develop US-NZ scientific cooperation to address OA. Papers presented at the workshop and points raised during discussion are summarised.

Increasingly frequent and intense extreme weather events such as Cyclone Gabrielle are likely to impact seafloor marine ecosystems by accelerating soil erosion and sediment transport to the ocean by rivers.

The objective of this project was to understand sediment impacts from the February 2023 Cyclone Gabrielle event on marine environments of the Hawke’s Bay and Gisborne regions to enable rapid fisheries management decisions.

We conducted two vessel surveys in June and October 2023 focusing on offshore seabed environments deeper than 15 metres. As part of these surveys we mapped selected areas of the seafloor, surveyed life on the seabed using a towed underwater camera, and obtained sediment core samples.

An ocean current and sediment transport model was designed and implemented to investigate the transport and deposition of sediments after Cyclone Gabrielle. Concentrations of suspended sediments and other parameters in the surface ocean along the east coast of the North Island were estimated from satellite images. This satellite information was used to inform the sediment transport model and to characterise the spatial extent and longevity of the offshore sediment plumes generated by Cyclone Gabrielle. A Seafloor model was used to explore impacts and recovery of seafloor ecosystems following the cyclone.

The analysis of satellite images suggest that the influence of Cyclone Gabrielle lasted approximately two to three months across the Hawke’s Bay and Gisborne coastal marine areas, with surface ocean parameters largely returning to normal by May. The concentrations of suspended sediment at the ocean surface in February were significantly elevated, but they did not exceed values typical of winter months.
Seabed mapping revealed areas of significant sediment erosion, and deposition up to about one metre in thickness, at Pania Reef, Tangoio Reef and Clive outfall area in Hawke Bay. Elsewhere, sediment core observations suggested the presence of fresh muddy deposits of up to about 15 centimetres. Swell waves were resuspending muddy sediments at shallow locations for several months after the cyclone, as was evident by the low underwater visibility during camera deployments.

The abundance and diversity of the sediment fauna sampled in Hawke’s Bay and Gisborne before (2010) and after Cyclone Gabrielle (June and October 2023) tended to increase away from the shore and into deeper waters. Sediment fauna were less abundant in June 2023 when compared with 2010, but appeared to be recovering by October 2023.

Seafloor animal and plant communities are highly likely to have been impacted by sediments at 11 of the 36 locations we surveyed using the towed underwater camera, as assessed by observations including (1) fresh mud layer on the seafloor, (2) animal/plant life in poor condition, and/or (3) absence of seaweed at shallow depths. However, for most of these locations a direct link to Cyclone Gabrielle cannot be demonstrated because no information on the distribution of seafloor organisms is available from before the cyclone. The likely exception is Wairoa Hard in Hawke Bay, where available information shows that kelp and sponges were present before the cyclone but were almost completely or completely absent after the cyclone. Whether this loss of habitat has led to reductions in associated fish populations is unclear.

Although limited by the availability of data, the ocean current and sediment transport model produced realistic predictions of suspended sediment concentrations and deposition at the seafloor. In the days following the cyclone, sedimentation in Hawke Bay was predicted to occur mainly close to shore in the western and central parts of the bay. In the Gisborne region, there was deposition of up to about 10 centimetres of sediments offshore of Poverty Bay and along a narrow band of the coast to the north near Tokomaru and Tolaga bays. These model predictions are broadly consistent with observations from the sediment core samples.

The Seafloor model showed small declines in structure-forming organisms such as sponges for Hawke’s Bay following Cyclone Gabrielle. These declines were not substantial, most likely because the region is already impacted by decades of fishing and increased sedimentation. The Seafloor model predicted weaker cyclone impacts for Gisborne than Hawke’s Bay and indicated that continued trawling may slow down recovery of seafloor communities following extreme weather events.

The lack of pre-cyclone information was a major obstacle in assessing the potential impacts of the cyclone on seabed ecosystems. Information collected as part of this project now form a valuable baseline that will inform future impact assessments in the region. Another limitation is the inability to use towed cameras to survey inshore habitats for extended periods because of poor underwater visibility. A precautionary approach could be warranted in the period following an extreme weather event until key habitats and ecosystems can be surveyed, and fish stocks and catch levels should be carefully monitored in the years following the event.

Sediment transport modelling is a promising tool for rapidly identifying areas most at risk from sedimentation following extreme weather events. However targeted sampling of sediment and water parameters under normal and flood conditions would help improve the accuracy and reliability of model predictions. The Seafloor model could be used to explore how spatial changes in fishing effort could enhance recovery following extreme weather events and could be improved through better information on the distribution of seafloor sediment and reefs and their associated animal and plant communities, particularly in the Gisborne region.

The impact of extreme weather events is made worse by decades of increased sedimentation in New Zealand’s marine environments. Addressing the long-term issue of sedimentation in marine ecosystems and the impacts of extreme weather events will require addressing the factors that have made New Zealand’s catchments more prone to erosion.

With projected increases in temperature and incidences of droughts and floods, pastures are likely to become more vulnerable to weeds and poor pasture persistence to become an increasingly significant issue. This on-farm study investigates whether increasing the diversity of sown pasture species can increase the pasture resilience and resistance to weeds under different climatic conditions. Thirty paddocks were selected in Northland, Waikato, Taranaki and North Canterbury.

Traditionally, New Zealand pastoral farmers have adapted their farming systems in response to extreme climatic events. This project will research these responses to provide information on how farmers could (and should) adapt to the extreme climatic events that may result from climate change.

Traditionally, New Zealand pastoral farmers have adapted their farming systems in response to extreme climatic events. This project will research these responses to provide information on how farmers could (and should) adapt to the extreme climatic events that may result from climate change.

Traditionally, New Zealand pastoral farmers have adapted their farming systems in response to extreme climatic events. This project will research these responses to provide information on how farmers could (and should) adapt to the extreme climatic events that may result from climate change.

The goal of this report it to provide a platform for capacity development and action on adapting to climate change throughout New Zealand by developing case studies in the kiwifruit industry.

To establish end-user requirements for information and advice on how climate change is likely to affect drought and agricultural production in New Zealand and to establish methodologies and timelines required to develop appropriate updated analyses based on the latest climate change scenarios.

Note, while this document is marked 'confidential', it has since been approved for public release.

This report identifies the major opportunities that climate change brings to extend the growing season and increase forage crop yields through radical changes in forage germplasm and management.

Note, while this document is marked 'confidential', it has since been approved for public release.

This report gathers new above-and below-ground biomass and wood density data for Eucalyptus fastigata for carbon model development, required under NZ’s obligations to the Kyoto Protocol. The biomass work was done in conjunction with a survey of wood density and soil nitrogen fertility undertaken in trials of various ages throughout New Zealand. The entire data set will be used to develop a national carbon growth model for Eucalyptus fastigata in New Zealand.

One of a series of case studies called adapting to a changing climate. The report summarises the study entitled Learning from past adaptations to extreme climatic events: A case study of drought which looks at historical adaptation to two of the most serious droughts in the North Otago/South Canterbury region. Outlines the drought resistant strategies that dryland farmers have developed over many years in response to drought events.

The Greenshell mussel (GSM) is a commercially, ecologically and culturally significant species to New Zealand. Summer die-offs, spat retention issues and a severe decline in GSM spat settlement have been reported in the Marlborough Sounds. The causes of these effects are unknown but preliminary evidence indicates that pressure from anthropogenic activities could contribute. The aims of this study were to

(1) test the toxicity of water and sediment extracts on early life stages of the GSM to identify potential sources of stressors affecting GSM recruitment, and

(2) investigate the effects of temperature on the toxicity of these stressors to help understand the potential impact of climate change and pollution on GSM.

Data from two surveys to characterise biogenic habitats identified through Local Ecological Knowledge interviews are reported. The results demonstrate that New Zealand’s continental shelf supports a diverse range of habitats and species, many of which have not yet been formally described by science. At selected sites, the key habitat-forming species were identified, and the invertebrate species composition and associated fish communities described over localized spatial scales, and depth ranges.

This report presents an assessment of the orange roughy stock off the west coast of the South Island (ORH 7B) in 2020. There was a fishery from 1985 to 1992, with the TACC peaking at 1708 t between 1989 and 1995, and the fishery was closed from October 2007. The assessment used two acoustic biomass estimates (2017, 2019) and a 2019 age frequency, completely rejecting the assumptions used in previous assessments that CPUE was directly proportional to biomass and that recruitment followed the assumed recruitment curve. This assessment is considered preliminary as work was stopped due to the conclusion that the acoustic surveys had probably missed a substantial proportion of the spawning biomass.