This review of existing information describes the current state of knowledge on soft-sediment marine assemblages around New Zealand; it identifies hotspots of biodiversity; highlights threats to, and the vulnerability of, assemblages; discusses knowledge gaps; and recommends areas or assemblages that could be the subject of directed future research. The review is supported by The Marine Soft Sediment Biodiversity Bibliographic Database which houses over 700 references.

Rhodolith beds in New Zealand harboured high diversity of associated macroalgae and invertebrates, undescribed taxa as well new records and range extensions of known species. Subtidal beds were investigated, examining structure and physical characteristics at two locations in the Bay of Islands, and characterising two species, Lithothamnion crispatum and Sporolithon durum. Responses of these rhodolith species to environmental stressors were also investigated both in the field and in culture.

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.

The purpose of this report is to draw out key lessons on how science and environmental knowledge have been used in the past to achieve desired environmental outcomes. Phase Three covers the final stage and is an account of observations made during the process of discussing the research findings with the key stakeholders. three topic areas of soil erosion, pest control and nitrogen management.

This report examines the psychological, social and other factors that determine farmers' different responses to environmental change. In particular, it is designed to explain why some farmers implement environmental strategies but others remain intransigent and resistant to change.

A paper discussing biocontrol systems as a mainstream pest management tool for the productive and environmental sectors in the light of adapting to changing climate.

The goal of this research is to determine whether additional evidence supports the initial observation that New Zealand's pastoral production systems may have a substantially reduced ability to cope with environmental stress under elevated CO2 conditions likely to be encountered with global change.

An increasing concentration of carbon dioxide (CO2) in the atmosphere is the most predictable of the global changes that will alter the environment for our biological industries. Predicted temperature changes for New Zealand are lower than the global average prediction (Niwa, 2011) but, because atmospheric CO2 is relatively well mixed, the rate of change in CO2 will be the same as experienced across the globe. CO2 is rising because of the burning of previously sequestered fossil fuels and changes in land use, in particular the conversion of old growth forest to cropland. Predicting future CO2 concentrations is important because of the direct impact of atmospheric CO2 concentration on terrestrial ecosystems and because CO2 is the most abundant anthropogenic greenhouse gas and thus directly influences potential changes in climate.

The impact of floods on the primary sector was first assessed nationally and then for the Awanui River Catchment in Northland. The analyses focused on the impacts of flooding on the primary sector, including changes in land uses as an adaption response to floods with climate change and subsequent changes in economic and environmental indicators. The specific objectives of the analysis are to:

1 quantify New Zealand’s primary sector exposure to flood hazards.

2 quantify the primary sector’s exposure and financial losses from floods in one catchment – the Awanui catchment.

3 analyse the impacts of flooding on land-use change and economic and environmental indicators.

4 evaluate economic and social welfare changes from floods-induced land-use change.

Tuck, I.D.; Hewitt, J.E.; Bulmer, R.H. (2019). Monitoring Recovery of Benthic Fauna in Spirits Bay.

New Zealand Aquatic Environment and Biodiversity Report No. 206. 74 p.

This report describes changes in the benthic communities of Spirits Bay related to fishing pressure and environmental factors. Survey data were analysed from 2006, 2010 and 2017. Epifaunal and infaunal communities consistently identified year, habitat, depth and fishing effects. Weaker fishing effects were detected from recent surveys, where fishing effort was lower. Species identified as sensitive to fishing were previously identified as sensitive on the basis of life history and morphology.

D’Archino, R.; Neill, K.F.; Nelson, W.A.; Fachon, E.; Peat, C. (2019). New Zealand Macroalgae: Distribution and Potential as National Scale Ecological Indicators.

New Zealand Aquatic Environment and Biodiversity Report No.207. 217 p.

Canopy-forming macroalgae are internationally recognised as critical components of coastal ecosystems as primary producers, coastal buffers and provision of habitat. This report evaluates the use of large brown macroalgae as indicators of ecosystem health by: summarising the international and national literature; testing the responses of key species to stressors in culture; investigating a range of approaches to mapping and monitoring, including the use of drones and machine learning to analyse underwater videos.

New Zealand Aquatic Environment and Biodiversity Report No. 214. 168 p.
(Manuscript 3334)

A spatial risk assessment of threats was undertaken for Hector’s and Māui dolphins, to inform a revised Threat Management Plan (TMP) for the species. A Bayesian risk model was developed using the spatially-explicit fisheries risk assessment (SEFRA) approach, incorporating revised estimates of Hector’s and Māui dolphin spatial density and intrinsic population growth rate. The risk model was used to estimate spatial overlap, annual deaths and risk for commercial fisheries and lethal non-fishery threats, including toxoplasmosis. Spatial overlap was estimated for other threats.

New Zealand Aquatic Environment and Biodiversity Report No. 215. 18 p.

A Bayesian Māui dolphin population model was developed integrating information from genetic “mark-recapture” and population size estimates. Model runs incorporated estimates of historical annual deaths from commercial fisheries and toxoplasmosis obtained from a separate spatial risk assessment. These models were then used to simulate the effects of estimated threat-specific mortality rates on future population growth.

New Zealand Aquatic Environment and Biodiversity Report No. 217. 62 p.

This study provides an indicative assessment of vessel traffic and seismic survey related noise. Vessel AIS data for the year of July 2014 to June 2015 was used to determine density and speed grids by vessel category. JASCO’s cumulative vessel noise model was used to model the sound from 15 vessel categories and two marine seismic surveys during representative summer and winter months in 1-minute time steps. Results are presented as maps, animations and plots of sound levels at static locations.