Most of Council’s biodiversity monitoring in the coastal environment involves broad-scale mapping of habitats in estuaries and 200m coastal terrestrial margin as well as fine-scale assessments of muddy environments in estuaries. More recently Council has partnered with Birds NZ to produce reports about shorebird communities of Tasman’s coast.
This report was completed in February 2022 and is a baseline survey of the indigenous bird values of the Tasman district coastline.
The coastal ecological risk assessment monitoring report was completed in 2012, this report includes broad-scale habitat maps and detailed risk assessments within estuaries, beaches and dunes, rocky shores and terrestrial margins. The area covered includes the majority of Tasman’s coastline, but excludes the coasts of Farewell Spit and Abel Tasman National Park (few resource management issues exist in these areas).
This report includes significant new information from fieldwork carried out in 2010-11 but also integrates information from all previous studies in Tasman District’s coastal environment.
Tasman District’s coast is ecologically diverse with a broad range of habitat types. It is a place of high biological diversity and high economic value. Despite these high values the vulnerability assessment identified a number of key issues:
In general, the state of mud/sand tidal flats in the majority of Tasman’s estuaries is good to moderate. The condition of the remaining saltmarsh habitat is good, although a very large proportion of this habitat has been lost over the last 100 years to create farmland, roads or industrial areas. The concentration of disease-causing organisms in estuarine shellfish where there is intensive urban or pastoral land use is high and within the water the concentration is moderate or high during and after rain. Concentrations of nutrients and toxic chemicals are low.
An overall analysis of the condition, or state, of estuaries in the district was undertaken in 2009 and is available via the link below. This report also included analysis of data collected by the Department of Conservation on the Wanganui inlet.
The Motueka Delta estuary is a shallow tidal river mouth estuary that discharges onto a broad delta (750ha). It is highly used and valued for its aesthetic appeal, rich biodiversity, shellfish, assimilation of wastewater, bathing, duck shooting, whitebaiting, fishing, walking, and scientfic appeal.
Much of the Motueka estuary/Delta is shallow, will flushed, has a very high freshwater inflow (particularly during rainfall events), and short residence time and consequently is not very susceptible to having water and sediment quality problems.
Much of the estuary is in good condition but fine sediments do tend to settle in some 'at-risk' areas where soft muddy conditions exist (e.g. in the Kumara area and on the Motueka delta towards the Riwaka River Mouth) and localised nuisance algal blooms near the Motueka Sewage Treatment Plant.
Moderate macro-algal and phyto-plankton blooms probably due to high nutrient levels coming from the Motupipi River (the dominant inflow). About 35 hectares of saltmarsh and intertidal areas have been lost to reclamation but large areas of saltmarsh still remain.
This estuary is valued for its aesthetic appeal, its rich biodiversity, shellfish collection, swimming, duck shooting, whitebaiting, fishing, boating, walking and scientific appeal.
Because Motupipi is a small tidal-lagoon estuary, dilution of incoming freshwater is limited, which makes it more susceptible to water and sediment quality problems, particularly in the western arm (close to the input from the Motupipi River).
Much of the Motupipi Estuary is in good condition (particularly the eastern arm), but the western arm (upper, mid and lower) is subject to algal blooms, shellfish health risk and sedimentation. The upper estuary experiences periodic phytoplankton blooms and low dissolved oxygen. Elevated nutrients, sediment and disease-causing organisms enter the estuary from catchment run-off. As is the case with all estuaries, sea level rise will remove saltmarsh habitat and the invasion of pests and weeds is an ever-present threat.
Moutere estuary is valued for its aesthetic appeal, its rich biodiversity, shellfish gathering, swimming, water-skiing, waste assimilation, fishing, boating, walking and scientific appeal. A small commercial port and marina are located at the northern entrance.
Elevated nutrients, sediment, disease-causing organisms and possibly toxicants entre the estuary from catchment run-off. A fish-processing, fishmeal and icecream factory discharge at Port Motueka. Other stressors include the presence of seawalls, causeways, culverts, stormwater. As is the case with all estuaries sea level rise will remove saltmarsh habitat and the invasion of pests and weeds is ever-present.
Ruataniwha Inlet is a moderate-sized (863ha) shallow tidal lagoon estuary that has a broad entrance mouth. It is located at the delta of the Aorere River. Large barrier spits project southward creating a relatively stable area in the north of the inlet. About 48 hectares of saltmarsh and intertidal habitat has been lost through conversion to pasture.
Ruataniwha estuary is valued for its aesthetic appeal, its rich biodiversity, shellfish gathering, swimming, duck shooting, fishing, boating, walking and scientific appeal. A small port is located at the northern entrance.
The Waimea Inlet is the largest enclosed estuary in the South Island. It is 3,455 ha in area, with an internal coastline of 65 km. Episodes of heavy sedimentation occurred in the 1960s and 70s affecting some of the more enclosed parts of the estuary.
Approximately 170 hectares of intertidal habitat has been lost to reclamation, most of which occurred prior to 1980. During periods of high rainfall, elevated levels of disease-causing organisms can be flushed into the estuary. The historic effect of toxins from various industries and landfills is localised e.g. the Richmond industrial area and the now-remediated Fruitgrowers Chemical Co. site at Mapua.
There are ten islands in the inlet, with Rabbit Island forming an outer barrier that influences river and tide flows and sediment distribution. The Waimea River flows out to the two estuary mouths each end of Rabbit Island. It is shallow and well-flushed. The inlet is a large open space beside fast-growing urban centres.
The inlet is of international significance for migratory bird species and is of national significance for other endangered or threatened species. These include birds such as bar-tailed godwit, white heron, royal spoonbill, little egret, Australasian bittern, and banded rail, and plants such as coastal peppercress and grey salt bush.
Estuarine monitoring of potential environmental effects from the now-remediated former Fruitgrowers Chemical Company site in Mapua has been ongoing since 1999 and more intensively since 2009. Such monitoring included sediment and biota (particularly cockles and snails) analysis at sites near the old FCC site, and at two reference sites.
The reports on the sedimant and biota monitoring are available:
The Former Fruit Growers Chemical Company Site at Mapua - Sediment and Biota Reports
Habitat intactness and diversity is high with almost all its intertidal vegetation intact. Large areas of sea grass (42% of the estuary) and saltmarsh (5% of the estuary) exist creating valuable habitat for marine and freshwater fish.
This estuary is generally valued for its aesthetic appeal, its rich biodiversity, duck shooting, whitebaiting, fishing, boating, walking and scientific appeal. The estuary is protected in the southern third by the Westhaven (Te Tai Tapu) marine reserve, and the remaining two-thirds to the north is the Westhaven (Whanganui Inlet) wildlife management area. Towards the south eastern end there is the small Mangarakau wharf.
This estuary currently has relatively few threats. As is the case with all estuaries sea level rise will remove saltmarsh habitat and the invasion of pests and weeds is ever-present.
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