Wairoa Embayment: benthic habitats, environmental status and potential future threats


Author:  
Drew Lohrer, Sarah Hailes, Katie Cartner, Sanjay Wadhwa, Scott Edhouse, NIWA
Source:  
Auckland Council, Research, Investigations and Monitoring Unit, RIMU
Publication date:  
2012
Topics:  
Environment

From the executive summary:

In 2000, the Auckland Regional Council (now the Auckland Council) commissioned NIWA to design a State of the Environment Monitoring Programme for the region’s marine ecological resources (Hewitt 2000). The first tier of the agreed upon approach entailed spatially constrained but temporally detailed (2-3 monthly) monitoring at sentinel sites in important harbours (Tier I). The second tier involved spatially intense sampling of intertidal and near-shore (<20 m) subtidal areas with the objective of defining geospatial patterns of habitats and describing the ecological communities present at particular points in time (Tier II).

Here we report on a Tier II investigation of the Wairoa Embayment, in the southeastern portion of Tamaki Strait, encompassing the intertidal and subtidal habitats along the inner coastline between the tips of Whakakaiwhara and Koherurahi Points. This relatively small (21.2 km2) and shallow (<4 m depth) embayment is protected from significant northeasterly swell by Pakihi and Ponui Islands to the northeast and Waiheke Island to the north. Water from a relatively large and predominantly rural catchment flows into the embayment via the Wairoa River. Suspended sediment concentrations in the Wairoa River appear to be high, and the lower Wairoa River channel has thick mangroves on both banks. Mangroves are present in other parts of the upper intertidal zone in the embayment also. There are several intertidal rocky reef outcrops, located mainly on the two flanks of the embayment (Whakakaiwhara and Koherurahi Points). There are extensive sand and shell-dominated intertidal flats in the embayment, particularly north of the Wairoa River channel, with slightly elevated muddiness in the southeastern portion. No seagrass habitat is apparent in the embayment at present.

Auckland Council technical report, TR2012/028.

July 2012