Waikato Regional Estuary Monitoring - sediments

Estuaries have been identified in the Waikato State of the Environment Report as one of the coastal areas most at risk from human activities in the Region and have been identified as priority areas for ecological monitoring. Long-term monitoring of selected estuaries will enable changes in physical, chemical and biological sediment characteristics, and help to identify natural or anthropogenic variation. Estuaries currently being monitored are Whaingaroa (Raglan) and the southern Firth of Thames. Purpose: Sediment information is collected as part of the Regional Estuary Monitoring Programme to monitor the state of estuaries in the Waikato Region. On of the main potential effects of catchment activities on estuarine and coastal areas is a change in the sediment regime in these areas as a result of sediment washed down from the catchment. Any increases in sediment run-off from a catchment can result in an increase in the rate of sedimentation and changes in the textural character of the surface sediments in a estuary. Previous studies have established that in the past, catchment activities have had considerably impacts on the sediments (large increases in the rates of sedimentation and changes in the character of the sediments in estuaries in the Waikato Region. Changes in the sediments in the southern Firth of Thames and Whaingaroa Harbour are being monitored as changes in the particle size composition of the surface sediments. Changes in turbidity, sedimentation rates and/or in the nature of sediments can be accompanied by ecological changes, as many species have strict sediment particle size preferences. Organic matter represents an important energy source for microbial decomposer organisms in the sediment and for benthic animals that feed on detritus and the associated microbes.

Sediment grain size data for estuary monitoring sites in the Firth of Thames and (Whaingaroa) Raglan Harbour. Sediment total organic carbon and total nitrogen also measured.

Raglan Harbour and the southern Firth of Thames

Kaiaua (NZMS 260-S12 150510), Miranda (NZMS 260-S12 180435), Thames (NZMS 260-T12 350465), Kuranui Bay (NZMS 260-T12 345505) and Te Puru (NZMS 260-T12 345580) in the southern Firth of Thames Whatitirinui Island (NZMS 260-R14 795805), Te Puna Point (NZMS 260-R14 790790), Okete Bay (NZMS 260-R14 790770), Haroto Bay (NZMS 260-R14 815775) and Ponganui Creek (NZMS 260-R14 755780) in Whaingaroa Harbour.

Monitoring began at all five sites in the southern Firth of Thames and at four of the sites in Whaingaroa Harbour in April 2001. Monitoring began at the fifth site (Ponganui Creek) in Whaingaroa Harbour in October 2001.

Five composite sediment samples are taken at each site at each sampling time. Samples are taken from the upper 1 cm of the sediment. Each sample is processed to remove organic and carbonate material. Following processing, samples are analysed for particle size using NIWA's Galai laser sediment particle analyser. Frequency of collection: Monitoring is undertaken at 3-monthly intervals in January, April, July and October at Miranda and Kuranui Bay in the southern Firth of Thames and at Whatitirinui Island and Okete Bay in Whaingaroa Harbour. The other sites in each estuary are monitored at 6-monthly intervals in April and October.

Gaps in collection: No gaps in data for organics. Chlorophyll and phaeophytin missing data from January 2002 and April 2003. Completeness: Collection of samples is ongoing as described above. No samples are missing from the time period described above.

spreadsheets, charts, reports Digital Format: MS Excel, MS Word, PRIMER

Consent conditions Catchment management

Publicly available Sensitivity/Confidentiality: Not confidential

Data and reports updated annually.

Turner et al 2000 provides a comprehensive overview of the information that we have for the Region's estuaries. This information has been used to prioritize the estuaries to be included in the Estuaries Monitoring Programme for the Waikato Region. Information available for each estuary is split into the following headings: Estuary characteristics, Area of estuary, Catchment characteristics, Major habitat types, Significant biological communities/species, Maori significance, Community significance, Existing information, Catchment monitoring, Other issues.