NIWA mud-sand survey

Transects traversing mud-sand interfaces were sampled in 19 northern North Island estuaries/harbours (including Whitianga, Manaia and Kawhia) for macrofauna and sediment characteristics. This data is used to develop species-specific models to predict probability of occurrence relative to sediment mud content for 13 common macrofaunal species, as well as the distribution of maximum density along the gradient from mud to sand as another indicator of a species' preference. Purpose: To help forecast the response of macrofaunal species to long-term changes in sediment type.

12 locations on the Coromandel (Manaia and Whitianga) and 6 locations at Kawhia are sampled for macrofauna, sediment particle size, organic matter, chlorophyll a, shear stress, penetrability, and elevation.

Ahuriri, Bowentown, Kawhia, Koutou (Hokianga), Manaia, Mangawhai, Wiroa Island (Manukau), Matakana, Mangonui, Ngunguru, Ohiwa, Otamatea (Kaipara), Porangau, Te Puna (Tauranga), Awaawaroa Bay (Waiheke), Waiotahi, Whangape, Waikopua (Whitford), Whitianga.

Kawhia – E2668841 N6344609, NZMG, 1:25000, AREA Manaia – E2729391 N6480968, NZMG, 1:50000, AREA Whitianga – E2750534 N6477849, NZMG, 1:50000, AREA

October and December 2000

One transect over the mud-to-sand sediment interface within an intertidal habitat at each locality was sampled. Each transect was divided into 12 strata each containing haphazardly chosen sample locations. At each sampling position, two 13cm diameter x 15cm deep cores separated by about 1m were taken. The core samples were sieved through a 1 mm mesh. Sediment geotechnical properties were measured using a penetrometer and shear vane. 0.25 m2 quadrats were photographed to quantify crab burrow density. A core (1.5 cm diameter x 2 cm deep) was collected for sediment particle size and organic matter, and another core to assess benthic chlorophyll a. Frequency of collection: One off study

A potential confounding factor for single surveys is major recruitment or post-settlement movement events. To dampen the potential effects of such temporal variability only large macrofauna were sampled. Predictive models reasonably general in their ability to forecast the distribution and abundance of species associated with habitat changes that are mediated through changes in sediment particle size due to: used only macrofauna, sampling design that restricted the potential for other factors to confound the analysis but facilitated the rapid collection of data over a reasonably wide geographic and oceanographic extent. Gaps in collection: Not reported Data quality: Not reported Attribute accuracy: Not reported Completeness: Not reported

report, electronic

Ecological predictive models Land management

See NIWA Sensitivity/Confidentiality: See NIWA

Finished