Animals and plants in estuaries

Cord GrassPlants that survive in an

estuarine are called hydrophytes, because they live in water. The four types of cord grass, which is the most prominent vegetation in most estuarine wetlands, are smooth, common, dense-floweredand marsh-hay.

Mangrove trees

The mangrove is a small tree or shrub with a grey twisted trunk, leathery olive leaves and tiny yellow flowers.

Glasswort

Glasswort, a native herb of the wetland, is named for the breaking-glass sound it makes when stepped

on.

Salt meadows

Beyond salt marsh, where the land becomes drier, turf-forming plants are favoured and a salt meadow develops.

Harsh Habitat

The estuary is a hostile environment for most plants because salt dominates. A few grow further back on the shore, where they live in a fluctuating environment of sea water and fresh water.

Sea Grass

Small and dark green, with ribbon-like leaves, this plant takes root in sandy silts on tidal flats throughout the country.

Salt Marsh Plants

Salt marsh areas are found at the head of estuaries, landward of the sea grass and mangrove.

Great Blue Heron

The great blue heron must live by a marsh water source, where it nests among the grass and bushes.

Broad-Wing Hawk

The broad-wing hawk, common to wetlands, perches on the bushes and watches for prey. Unlike other raptors, this hawk migrates in flocks.

Muskrat

The muskrat is ideally suited for wet environments and prefers marshes because of the constant water level.

Mud worms

Known as mud worms or bristle worms, these small segmented creatures are related to earthworms, but are characterized by a pair of short bristly structures on each segment.

Cockles

The cockle or tuangi is a shallow-burrowing shellfish, found from subtidal to mid-tide levels. It is not related to the northern hemisphere cockle,

CrabsThree kinds of crab are

commonly encountered on tidal mudflats:

Kairau, the tunnelling mud crab dominates the upper tidal zone.

The mid-low tide zone is the realm of another tunnelling crab – the stalk-eyed mud crab.

The hairy handed crab is found throughout the intertidal zone.

Fish

Sand flounder Common sole

In New Zealand at least 30 types of fish use estuaries at significant Snappertimes in their life. Some, such as sand flounder, yellow-bellied flounder, common sole, kahawai, grey mullet and yellow-eyed mullet, move in and out of estuaries each day. Others – snapper, red cod and gurnard – are seasonal visitors.

Migrating Fish

Adult whitebait or come down rivers to lay their eggs among the plants of the upper estuaries in late summer and autumn, and then die.

Birds

Waybills Caspian tern

Tidal flats hold a bounty of food for wading birds, which gather there in large numbers to feed; for individuals, there is little protection on the exposed flats.