Waikato Regional Estuary Monitoring - intertidal soft-sediment benthic communities and 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. Waikato Regional Council’s Regional Estuary Monitoring Programme (REMP) was initiated in April 2001 to determine the current status and monitor the temporal changes in the state of selected estuaries in the region. The monitoring programme samples sediments and sediment-dwelling organism communities on intertidal mud- and sand flats in two the Firth of Thames, Raglan (Whaingaroa) Harbour and (recently) Tairua Harbour. Measurement s of sedimentation are also made. Long-term monitoring of selected estuaries will identify changes in intertidal benthic animal communities and the sediments they live in. This will help to identify natural or anthropogenic variation.

The following community attributes are calculated using standard Excel functions: total number of each species (from 10 cores) mean number of each species per core total number of species (from 10 cores) number of species per core mean number of species per core total number of individuals (from 10 cores) number of individuals per core mean number of individuals per core total numbers of each taxonomic group mean numbers of each taxonomic group percent community composition. Species Diversity measured by the Shannon-Wiener Index (H'). Species Evenness expressed as Pielou's Evenness Index (J'). Species Richness measured by Margalef's Index (d). Sediment grain size data for estuary monitoring sites in the Firth of Thames, Whaingaroa (Raglan) Harbour and Tairua Harbour. Sediment total organic carbon and total nitrogen also measured. Sedimentation rates are also estimated in the Firth of Thames and Raglan with measurements of sediment accumulation over buried plates. Results have been published in a series of technical reports and on the Council's website (see below).

Raglan Harbour, Tairua 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 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. Monitoring began at Tairua Harbour in 2013. Data has been collected since at varying frequencies.

A pilot study undertaken in April 2001, determined that 12 core samples (13 cm diameter, 15 cm deep) was the optimal number to collect. A more recent study determined that 10 core samples is sufficient. Detailed methodologies are availabe on the REMP website (see below) and in reports. Prior to 2008, two sites at each estuary (Thames and Raglan) were sampled quarterly. The other sites were sampled six-monthly. Since approx 2008, all sites have been sampled six monthly. From 2016 onwards, sites are sampled annually. Samples are sieved (500 µm mesh), and preserved with 70% isopropyl alcohol in seawater and stained with Rose Bengal. In the laboratory, macrofauna are sorted from the core samples, identified to the lowest practicable taxonomic level (generally species or species group), counted and stored in 50% isopropyl alcohol. The most cost-effective approach to monitoring macrofauna is to monitor a selection of species (or species groups) that are ecologically important, abundance reflects environmental change, represent a variety of taxonomic groups and feeding habits, and are relatively common. All non-indicator species are classified into major taxonomic groups (amphipods, bivalves, crabs, cumaceans, gastropods, isopods, ostracods, polychaetes, shrimps and "other"). 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 were analysed for particle size using NIWA's Galai laser sediment particle analyser in the early years of the programme. More recently the University of Waikato's Malvern Mastersizer is used. Tairua Harbour has recently been included in REMP (sampling commenced in August 2013), but there are many other (approximately 25) estuaries in the Waikato region, which cover a range of different types, containing a wide variety of habitats, and are exposed to a wide range of pressures. In the future, new sites may be introduced to the REMP by implementation of a nested monitoring design. All five sites will be monitored at each estuary for two years, after which just two sites will be monitored at each estuary for the next three years. During the years of reduced sampling efforts, the REMP can be expanded to other estuaries in the region.

Monitoring is only undertaken at three estuaries within the Waikato Region, due to resource limitations. It is not possible to identify at which point on a continuum of levels of environmental stress that any community exists on the basis of the values of any community attribute. Nor is it possible to identify what value might be expected for a benthic community at any site if the community were not subject to environmental stress. Differences in the values of the attributes of benthic community structure can thus best be assessed by comparison between sites along spatial gradients or over temporal gradients. Currently this indicator compares the measures of benthic community structure between the monitoring sites in each estuary. In the future we will be able to assess changes in these attributes over time. Currently there is no nationally agreed protocol, so we can not compare changes in the benthic communities of Waikato estuaries with those in other regions in New Zealand (or internationally). The Auckland Regional Council has implemented similar monitoring programmes in a number of estuaries in the Auckland Region. This will enable comparisons between changes in benthic communities in estuaries that may occur as a direct or indirect consequence of estuary and catchment management in the two Regions. Data quality: Presently there are no formal guidelines or standards available in New Zealand for assessing this data. 1) Sample Sorting – Re-sorting of samples is used for quality control of sorting. As a minimum re-sorting effort, a random selection of 10% of the samples from each site is completely re-sorted. An experienced sorter other than the original sorter conducts re-sorting. Percent sorting efficiency is: The minimum acceptable sorting efficiency is 95%. If sorting efficiency is greater than 95%, no action is required. If the sorting efficiency falls below 95%, all samples in the failed batch are re-sorted. 2) Species Identification and Counting – Re-identification and re-counting of samples is used for quality control of species identification and counting. As a minimum, a random selection of 10% of the samples from each site is completely re-identified and re-counted. This includes re-examination of any material left-over from each sorted sample. An experienced identifier other than the original identifier conducts re-identification and re-counting. Percent identification and enumeration efficiency is: The minimum acceptable identification and counting efficiency is 90%. If identification and counting efficiency is greater than 90%, no action is required. If the identification and counting efficiency falls below 90% level, the type of error is identified (e.g., identification error, counting error, unrecorded species, recording error, organisms overlooked) and the samples re-analysed for this error. 3) Data Management - All data is entered into the relevant databases immediately after collection. All input data is checked and verified against the field and laboratory data sheets. Checking and verification is undertaken by a person other than the original person responsible for data input, to identify mismatches and correct keypunching errors. A standard laboratory processing form is used for tracking each sample (DOCS671729). It includes the details of each sample (replicate number, site, date), the name of the sorter and identifier responsible, the time required for sorting and species identification and counting, and any additional comments. These are completed at each stage of the laboratory analysis of all the samples. All labelling adheres to a systematic numbering system to enable identification of individual samples, sampling occasions, sites and estuaries. Attribute accuracy: Not reported Completeness: Not reported

spreadsheets, charts, reports MS Excel, MS Word, PRIMER. GIS layer held by Waikato Regional Council - data catalogue see link below.

Consent conditions, state of the environment monitoring.

Publicly available - see link below. Data is now reported online rather than published reports.

Data updated regularly through web page and environmental indicator (see below).

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 prioritise 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. Additional comments: The monitoring programmes implemented in Waikato Region estuaries are based on similar programmes that have been developed by NIWA and which are used in many estuary monitoring programmes conducted by the Auckland Regional Council. As more information becomes available, analysis of changes in indicator species populations and benthic community characteristics at each monitoring site over time will be undertaken (e.g., time-series analysis, multivariate analysis).