The Salt Meadow at Ngakuta Bay

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Ngakuta Bay at low tide exposes a large low-lying intertidal area which is rich in plants and animals that are especially adapted for salty conditions. In the foreground is a thick carpet of water pimpernel, Maakoako Samolus repens. Other plants an animals in this fascinating area are illustrated and described below. Wherever possible photos are taken at Ngakuta Bay.

Water pimpernel, Maakoako Samolus repens. This plant is quite common on the foreshore at Ngakuta Bay. It grows initially as a rosette and then develops prostrate branches. It has a high tolerance to waterlogging and salinity, and is therefore good at colonising salt marshes. Photo Foss Leach, identification Patrick Brownsey Te Papa. Enlarge

A patch of water pimpernel during flowering, Xmas day 2008. These flowers are tiny and barely noticeable whn wandering along the foreshore, but stoop down and take a look closer up; it is quite beautiful. Photo Foss Leach. Enlarge

Glasswort or Salicornia, Ureure Sarcocornia quinqueflora, formerly Salicornia australis. This slow growing succulent plant is common on salt marshes and there are many patches of it along the foreshore east of the trailer park. They are very tolerant of salt condition including immersion in seawater. The leaves are very small like scales, and give the appearance of being without leaves, a little like some of our alpine Hebe spp. The colour varies from reddish tinges to bright green (next photo). Photo Foss Leach. Enlarge

Another patch of bright green Salicornia. The leaves are edible, and as a special treat English fishmongers used to give it away with fish. Cook it in the same way as asparagus (without salt). Three minutes in boiling water will do it, then refresh it in ice-cold water before adding to a dish or eating it as a standalone dish, with a bit of olive oil, or butter, and lemon juice. Of special interest to me is the fact that this plant uses the C4 pathway for photosynthesise and is a useful marker in archaeology. . Photo Foss Leach. Enlarge

Native ice-plant, Horokaka, Disphyma australe. This native plant is quite rare at Ngakuta Bay. It has a very small pink flower compared to the more common variety of ice-plant, Carpobrotus edulis, introduced from Sth Africa. The two hydridise. Photo Foss Leach, identification Barry Sneddon Te Papa. Enlarge

Jointed wire rush, Oioi, Apodasmia similis, formerly Leptocarpus similis. Found throughout New Zealand in coastal marshlands and estuaries. It spreads slowly from a creeping rhizome. Separate plants have either male or female flowers. Photo Foss Leach, identification Barry Sneddon Te Papa. Enlarge

Sea rush, Wiwi, Juncus kraussii subsp. australiensis. This grows readily in damp coastal areas and is the most common rush along the foreshore at Ngakuta Bay, Photo Foss Leach, identification Barry Sneddon Te Papa. Enlarge

Native sea celery, Tutae Koau, probably Apium prostratum rather than A. australe/. This plant is widespread in many habitats and is salt tolerant. This native celery is an excellent alternative to the Euopean variety and is easy to grow from seeds or by transplanting. Photo Foss Leach, identification Barry Sneddon Te Papa. Enlarge

Orache or Fat-hen, no Maori name Atriplex prostrata. This introduced plant, like most chenopods, is edible when cooked. The more common garden fat-hen which can be a nuisance in vegetable gardens was collected for food when I was a boy. Orcache is common around the margins of saline areas, and the salt marsh at Ngakuta Bay is no exception. Photo Foss Leach, identification Barry Sneddon Te Papa. Enlarge

Swamp Weed, Remuremu or Rekoreko Selliera radicans. This small salt tolerant plant forms a tight mat of groundcover with small bright green fleshy leaves and tiny white scented flowers. It grows in damp conditions and is sometimes used for lawns that never need mowing. This patch has Samolus repens in the front of it and Sarcocornia quinquiflora behind it. Photo Foss Leach, identification Barry Sneddon Te Papa. Enlarge

Closer view of Selliera radicans. Photo Foss Leach, identification Barry Sneddon Te Papa. Enlarge

On the areas exosed at low tide are found numerous bunches of this Red seaweed or algae, commonly known as Agar, Maori name unknown, Gracilaria sordida (syn. chilensis)§4. This species and Pterocladia lucida are hand-gathered along the shorelines of New Zealand for extracting agar which is used for growing bacterial cultures and as a gel in the meat-canning industry. Gracilaria chilensis has also been found to be a preferred food by paua in acquaculture. Photo Foss Leach, identification Jennifer Dalen Te Papa and Wendy Nelson NIWA. §4 Nelson, W.A. 1987. The New Zealand species of Gracilaria Greville (Rhodophyta, Gigartinales), New Zealand Journal of Botany, 25(1): 87-98. Enlarge

Sea Lettuce, Karengo (generic), Ulva compressa. There are several plants known as sea lettuce, and there are nearly 100 species in the Ulva genus. The long fronds of this seaweed are actually elongated tubes with walls just one cell thick and dotted with air bladders. It is usually abundant in very shallow water close to shore and thrives from nutrient-rich runoff from the land, especially of dissolved inorganic nitrogen and phosphorus. Like the seaweed species above, Gracilaria chilensis, this seaweed attached itself to a cockle shell for anchorage, and sometimes the two species will be found together on the same shell. The dry powder found in instant cup noodles in Japan is ground up sea-lettuce. Photo Foss Leach, identification Jennifer Dalen Te Papa. Enlarge

Eel-grass or Sea-grass or Zostera, Rimurehia, Zostera capricorni. This marine perennial flowering plant carried out its entire life cycle under water. It grows by budding stems and leaves from a creeping root system and entire bed can consist of only one interconnected plant. This repeated clonal growth pattern means that any one plant can live to great age. A single clone of the European species Zostera marina has been dated at 3,000 years using molecular techniques (Borum. et al. 2004: 26§1). Photo Foss Leach. §1Borum,J., Duarte,C.M., Krause-Jensen, D., and Greve, T.M. 2004. European seagrasses: an introduction to monitoring and management. ISBN: 87-89143-21-3 Enlarge

A closer view of eel-grass. This plant plays an important multipurpose role in the ecology of Ngakuta Bay, and as with many parts of New Zealand is in danger from high sediment loads from run-off and polution. These beds have the effect of trapping and stabilising bottom sediments, and provide the habitat for a wide variety of plant and animal species, including invertebrates, fish and birds. This entrapment of fine particles directly improves water clarity in the Bay and thus enhances the environment for other aquatic plants such as algae and also plankton. Photo Foss Leach. Enlarge

An aerial view of the foreshoire of Ngakuta Bay showing the present extent of patches of eel-grass. Last year's winter storm greatly reduced the size of eel-grass beds in the bay. These beds are important nurseries for juvenile fish, and deserve a protective approach when walking over the exposed flats at low tide. Enlarge

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This is adapted from Figure 2 from Hayward 1979^§2, and neatly illustrates just a few of the a few of the most common animals which inhabit beds of eel-grass. Close examination of any of the beds at Ngakuta Bay will reveal these animals. Not illustrated are the various species of juvenile fish that live here. Tiny flounders are all but invisible on the sandy bottom in these beds and make their presence known only when they move.

^§2Hayward, B.W. 1979. An intertidal Zostera pool community at Kawerau, Northland and its foraminiferal microfauna. Tane, 25:173-186.

Tiny crabs (species yet to be identified) living on single strands of eel-grass. They are very shy and at the slightest movement of an observer will take for cover underneath a leaf, only to reappear when you stand still. Enlarge

Hairy-Handed crab, Papaka Huruhuru, Hemigrapsus crenulatus. This crab can live in quite brackish water and doed not burrow. It is found under rocks or sand and mud and lives up to five years. It is a great scavenger and falls prey to small fish. It is usually not concerned by humans andwill carry on its business while being watched. Photo Foss Leach, identification Elliot Dawson. Enlarge

Stalk-eyed mud crab, Maori name unknown, Macrophthalmus hirtipes. This is a small male specimen of crab that burrows into the surface of mud-flats to make a tunnel in which it escapes from predators. This species mainly active at night. This crab grows up to 30-40 mm in size and has a greenish hue. The slightest movement of human observers it will scuttle into its burrow. Photo Foss Leach, identification Elliot Dawson. Enlarge

Tunnelling mud crab, Kairau, Helice crassa, This tiny crab dominates the upper tidal zone and is found in large numbers in small burrows on the exposed mud-flats at Ngakuta Bay. Like the former larger crab it retreats into a burrow as soon as it detects movemen. Kairau scoops up mud with its nippers and uses its mouth parts to locate organic matter. Enlarge

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Glass shrimp or Common shrimp, Koeke or Tarawera, Palaemon affinis. These animals range in size from about 13-54 mm and can be seen darting about in eel-grass beds and elsewhere. They have a semi-transparent body marked with lines of red and green, and conspicuous spots of orange and black on its leg joints and at the base of its tail. Although they have photophores they are probably not the main species responsible for the phosphorescence which is often visible at night in the waters of Ngakuta Bay. They are not easy to photograph because of their transparancy. Photo with bottom neon lighting from a light box by Melchor Ruiz, identification Elliot Dawson. Enlarge

Another photo, this time with top natural lighting. Accoring to Day (2001§3) the peak abundance of these shrimps appears to be during the winter months, and its maximum activity is at night and during the high tide. It is a carnivore, consuming a wide range of species but mainly amphipods. Photo Foss Leach, identification Elliot Dawson. §3Day, C.A. 2001. An introduction to the ecology anbd behaviour of the prawn, Palaemon affinis Milne-Edwards, 1837 (crustaces: Decapoda: Natantia). MSc thesis Zoology, University of Canterbury. Enlarge

Mud snail, Titiko, Amphibola crenata. This shellfish and others that live on mudflats are sometimes referred to as the 'lawnmowers of the mudflats' which aptly describes their role in the ecology of salt-marshes. They graze on brown and green algae in mud and leave a trail behind them as they move about the mud flat. The muddy foreshore at Ngakuta Bay is covered in these shells at low tide. Photo Foss Leach. Enlarge

A close up view of the mud-snail. Usually the shell is covered in mud, but when cleaned up is quite colourful. As they become older, the shell becomes thicker and helps to protect the animal from the sun and drying out at low tide. They retreat into the shell when exposed to the sun and wait until the flats become flooded again. These shellfish are pulmonates and have a lung rather than gills and can therefore survive out of water. They are edible, but rather muddy in flavour and not highly rated as food. Photo Foss Leach. Enlarge

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