Michaelmas and Upolu Cays is a national park in Queensland

Queensland

Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, 1409 km northwest of Brisbane

Brisbane

Brisbane is the capital and most populous city in the Australian state of Queensland and the third most populous city in Australia. Brisbane's metropolitan area has a population of over 2 million, and the South East Queensland urban conurbation, centred around Brisbane, encompasses a population of...

 and 33 km east of Cairns. It comprises two small cay

Cay

A cay , also spelled caye or key, is a small, low-elevation, sandy island formed on the surface of coral reefs. Cays occur in tropical environments throughout the Pacific, Atlantic and Indian Oceans , where they provide habitable and agricultural land for hundreds of thousands of people...

s on Michaelmas Reef, which forms the north-eastern section of the Arlington reef complex, within the Great Barrier Reef

Great Barrier Reef

The Great Barrier Reef is the world'slargest reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometres over an area of approximately...

.

Plants

The vegetation on Michaelmas Cay is characteristic of cays found on the outer barrier reef. Low-growing, it consists of Beach Spinifex, Stalky Grass, Goatsfoot

Ipomoea pes-caprae

Ipomoea pes-caprae, also known as Beach Morning Glory or Goat's Foot, is a common pantropical creeping vine belonging to the family Convolvulaceae. It grows on the upper parts of beaches and endures salted air. It is one of the most common and most widely distributed salt tolerant plants and...

, Bulls-head Vine, Sea Purslane

Sesuvium portulacastrum

Sesuvium portulacastrum, commonly known as shoreline purslane or "sea purslane", is a sprawling perennial herb that grows in coastal areas throughout much of the world.-Description:...

 and Tar Vine

Boerhavia diffusa

Boerhavia diffusa is a species of flowering plant in the four o'clock family which is commonly known as tar vine, punarnava meaning that which rejuvenates or renews the body, or red spiderling. It is taken in herbal medicine for pain relief and other uses. The leaves of Boerhavia diffusa are often...

. Nutrients fertilising the vegetation come from seabird

Seabird

Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...

 droppings and carcasses. The smaller Upolu Cay is unvegetated.

Animals

Michaelmas Cay is important as a breeding site for several species of tern

Tern

Terns are seabirds in the family Sternidae, previously considered a subfamily of the gull family Laridae . They form a lineage with the gulls and skimmers which in turn is related to skuas and auks...

s. It has been identified by BirdLife International

BirdLife International

BirdLife International is a global Partnership of conservation organisations that strives to conserve birds, their habitats and global biodiversity, working with people towards sustainability in the use of natural resources...

 as an Important Bird Area

Important Bird Area

An Important Bird Area is an area recognized as being globally important habitat for the conservation of bird populations. Currently there are about 10,000 IBAs worldwide. The program was developed and sites are identified by BirdLife International...

 (IBA) because it supports over 1% of the world populations of Greater

Greater Crested Tern

The Greater Crested Tern , also called Crested Tern or Swift Tern, is a seabird in the tern family which nests in dense colonies on coastlines and islands in the tropical and subtropical Old World...

 and Lesser Crested Tern

Lesser Crested Tern

The Lesser Crested Tern is a seabird of the tern family Sternidae...

s. Sooty Tern

Sooty Tern

The Sooty Tern, Onychoprion fuscatus , is a seabird of the tern family . It is a bird of the tropical oceans, breeding on islands throughout the equatorial zone. Colloquially, it is known as the Wideawake Tern or just wideawake...

s and Common Noddies also breed there. Other terns that have nested on the cay in the past include Roseate

Roseate Tern

The Roseate Tern is a seabird of the tern family Sternidae. This bird has a number of geographical races, differing mainly in bill colour and minor plumage details....

 and Black-naped Tern

Black-naped Tern

The Black-naped Tern is an oceanic tern mostly found in tropical and subtropical areas of the Pacific and Indian Oceans. It is rarely found inland....

s.

Green Turtles sometimes nest on the cays. The surrounding reefs have a rich marine fauna, including Giant Clam

Giant clam

The giant clam, Tridacna gigas , is the largest living bivalve mollusc. T. gigas is one of the most endangered clam species. It was mentioned as early as 1825 in scientific reports...

s.