13. Rocky coast seagrass habitats
Map ID Number: 13
Location: East Coast of North Island between East Cape and Cape Turnagain. (South of Cape Turnagain the rock platforms tend to be lower on the shore, often at or just below low water and consequently they generally do not support extensive beds of seagrass (Zostera capricorni)).
Approximate area: 811km2
Description of area:
A series of extensive siltstone intertidal platforms between about 70-120m wide, interrupted by extensive sand and gravel beaches in Poverty Bay, Hawke Bay, and at Porangahau. Each platform is typically backed by steep coastal hills of Tertiary siltstone, and topped by a narrow sand or boulder beach. All of the platforms are dotted with fissures, channels, and pools ranging up to more than 1,500m2 surface area. In some places the seaward edges of the platforms are higher than the mid-sections.
Biological attributes:
These platforms are characterised by extensive turfs of coralline algae (Corallina officinalis), Neptune’s necklace (Hormosira banksii), large beds of seagrass (Zostera capricorni), and the golden limpet (Cellana flava). These reef populations may form important connections for seagrasses in the isolated estuaries along this coast, and are important feeding areas for variable oystercatcher (Haematopus unicolor), whitefaced heron (Ardea novaehollandiae), and bar-tailed godwit (Limosa lapponica).
Criteria applied:
Extremities of range and adaptation to environment; representation (i.e. across physical types).
Status and management:
No exploitation, but some seagrass populations close to the high tide sand/ gravel shelf are vulnerable to the increasing vehicular traffic on coastal reefs. Driving vehicles onto the platforms between Kairakau and Blackhead Point in Central Hawke’s Bay is prohibited under the Hawke’s Bay Regional Coastal Plan. Populations are protected within the Te Tapuwae o Rongokako Marine Reserve north of Gisborne and Te Angiangi Marine Reserve south of Cape Kidnappers.
State of information:
Seagrass populations in these habitats are generally poorly described or understood.
References and further reading:
Central Fishery Management Planning Team (1987), Creswell and Warren (1990), Department of Conservation (1994), Glassey (2002), Haddon (1993), Haddon and Anderlini (1993), Henriques et al. (1990), Morton and Miller (1968).