Auckland Museum’s herbarium has over 5000 seaweed specimens from the Auckland Region.

Ranging from microscopic algae to the massive bull kelp, Auckland has a diverse range of seaweeds with over 400 documented species; this is due to Auckland’s varied coastline ranging from sheltered mangrove estuaries, exposed sandy beaches, to cliffs and reefs of varied geology.

Many of the Museum’s earliest Auckland seaweed specimens were collected by Lucy Cranwell, Botany curator from 1929 -1944. Lucy was an avid seaweed collector and added almost a thousand seaweeds to the collection. 

Following on from Lucy’s work, Museum Research Associate Mike Wilcox undertook the mammoth task of collecting and recording distributions and habitats for all of Auckland’s seaweeds. 

Mike has now added over 3500 seaweed specimens to Auckland Museum’s herbarium. Mike has also just published a book, called Seaweeds of Auckland, where you can learn more about Auckland’s seaweeds.

There are three main groups of macro seaweeds: green, red and brown. You can find numerous representatives of these groups around Auckland’s coasts. 

Here are some of the seaweeds that you might come across this summer.

Photo: Mike Wilcox and Dhahara Ranatunga © J Geux

Green sea fingers
Codium fragile subsp. fragile

This distinctive green seaweed is one of several introduced seaweeds in Auckland. Native to Japan it has now spread throughout Auckland and is regarded as one of the most invasive seaweeds in the world! It’s often found on sheltered harbour sites on the east coast of Auckland usually attached to small stones or cockle shells. It’s sometimes known as green sea fingers or my personal favourite ‘felty fingers’ which describes its appearance well. 

Green sea fingers / Codium fragile © J Geux

Red seaweed
Hummbrella hydra

This eye catching native red is a favourite for many seaweed enthusiasts but few see it in the wild. Found around the Hauraki Gulf islands and Great Barrier Island, Hummbrella hydra is subtidal found at depths of 10 - 15m. It grows at the rock/sand interface beyond the edge of the kelp forest. When pressed this delicate seaweed looks more like an animal than a plant! The herbarium specimen shown here was collected in Tiritiri Matangi. 

Hummbrella hydra, AK333030, © Auckland Museum CC BY

Neptune’s necklace
Hormosira banksii

One of our most recognisable seaweeds, you can find Neptune’s necklace along the rocky shore and in mangrove estuaries. Widespread throughout Auckland this seaweed is characterised by strings of olive brown hollow beads. The beads help the seaweed float and stop it from drying out in the sun. Neptune’s necklace is native to New Zealand, and also Australia. Keep an eye out for Neptune’s necklace on your next rocky shore fossick. 

Neptune’s necklace, Hormosira banksii © J Geux


Seaweeds of Auckland by Mike Wilcox is a new book about the seaweed flora of Auckland’s extensive and varied coastline. The marine habitats of these shores range from protected inner reaches of harbours and estuaries to severely exposed rocky shores of the west coast, and from the upper intertidal to the subtidal zone. The collections of Auckland seaweeds in the Auckland Museum Herbarium (AK) are listed in the book.

Proceeds from the sale of this book will go to the Auckland Botanical Society’s Lucy Cranwell Student Grant to support botanical research, including ongoing studies of seaweeds.

Seaweeds of Auckland is available for purchase at the Museum Shop.

Citation: Seaweeds of Auckland, Dhahara Ranatunga, Collection Manager, Natural Sciences