Blog Archives

Krill

Euphausia superba

There are around 85 krill species, ranging in size from 1cm to 14cm. The dominant species in the southern polar waters is the Antarctic krill (Euphausia superba), a small shrimp-like crustacean which plays a key role in the Antarctic food web. Krill is considered to be a keystone species, as it is the staple food of many fish, birds and mammals in the Southern Ocean. They are exclusively marine and have a life span of about 5 to 10 years. They are one of the most abundant and successful animal species on the planet. The total biomass of krill exceeds that of the human race. Put another way, the combined weight of the planet’s krill population is greater than the combined weight of every man, woman and child on earth...

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Well established, diverse sponge assemblages

Porifera

With more than 5000 species known across the world, sponges, (Porifera) come in an incredible variety of colors and an amazing array of shapes, ranging from a few millimetres to two metres across. They are predominantly marine and are found in virtually all aquatic habitats, although approximately 150 species are found in freshwater. The phylum name Porifera means porebearing, reflecting the perforated surfaces of the sponge’s tissue.

Sponge shape and size is affected to some degree by the environmental conditions they inhabit – strong currents, differing substrata and so forth lead to a great diversity even amongst the same species. Sponges are primitive multi cellular animals whose porous body is supported by a fibrous skeletal framework...

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Erect bryozoans

In spite of there being a large number of living species – around 5000 – bryozoa remain relatively unknown. The name literally means ‘moss animals’, after the bushy, moss-like appearance of some species. The two main types are encrusting bryozoans and erect bryozoans.

These aquatic – principally marine – animals exist for the most part as colonies of interconnected individuals called zooids. Colonies may consist of just a few zooids, or many millions. Some species encrust rocky surfaces, shells and algae. Other species form lacy or fan-like colonies. Individual zooids are rarely larger than a millimetre, but colonies can range in size from just a few millimetres to several metres.

Because of the colony forming nature of bryozoans, and because they are highly varied in...

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Brachiopods

Brachiopods mimic clams in appearance, but are anatomically quite different and are not related to the bivalve mollusc. They are filter feeding marine animals belonging to their own phylum (Brachiopoda) of the animal kingdom. Modern brachiopods occupy a variety of seabed habitats ranging from the Tropics to cold Polar waters, especially Antarctic waters. They are lophophorates, one of the major groups within the animal kingdom and so are related to the Bryozoa and Phoronida. In turn, the Lophotrochozoa belong to a larger group within the Kingdom Animalia called the Bilateria, so named because they are bilaterally symmetrical with a left and a right side to their bodies.

They look like clams, at least in the sense that they have two shells...

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Large reef fish

Blue Moki, Butterfish, Blue Cod, Trumpeter

In July 2003, The Earth Policy Institute and others reported that a recent review of marine fisheries, carried out by Ransom Myers and Boris Worm at Canada’s Dalhousie University, had concluded that a startling 90 percent of the world’s large predatory fish stocks, including tuna, swordfish, cod, halibut and flounder, have disappeared in the past 50 years. The study was carried out over a tenyear period, and attributed the decline to a growing demand for seafood, coupled with an expanding global fleet of technologically efficient boats. In addition to numerical decline, the review also concluded that the surviving members of the reef fish population are only one-fifth to one-half the size of earlier individuals.

With the capacity o...

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Paua

Haliotis iris

Whilst abalones are to be found in all of the world’s temperate and tropical seas, the New Zealand blackfoot abalone, or Paua (Haliotis iris), is unique  the waters around New Zealand. This univalve marine mollusc eats seaweed and inhabits rocky, coastal areas at depths between one and fifteen metres. It grazes on seaweed and ranges in size from 7-14cm at maturity, but can grow to a maximum of 18cm.

The cooler South Island waters enable the paua to grow larger here than they do in the warmer north. As a result, most wild paua are harvested from the South, the Chatham and Stewart Islands and from the southern coast of the North Island.

There are two other locally occurring abalone species, also known by the collective Maori name, paua (pronounced pah-wah)...

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Japanese wakame seaweed

The Japanese wakame seaweed, Undaria pinnatifida, which has established itself in several New Zealand locations, is a brown macroalga, and typically grows to 1-3m in length. It is an opportunistic species that forms dense forests and has the potential to outcompete and displace native species of algae.

It has been established since late 1980s in Australia and New Zealand, where it is highly invasive, forming dense forests that change the structure of ecosystems and displace native macroalgal communities. Like other kelp species, wakame consists of a holdfast, a stem (or stipe) and a blade. The central stem grows to 10cm wide and extends for the length of the plant. The blade may be up to 1m wide and extends from the tip of the plant for half to three-quarters the length of the plant...

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Lobsters

Lobsters, like shrimps and crabs, are decapods – literally meaning 10 legs – and can be found in all of the world’s tropical and sub-tropical seas as well as more temperate waters. They are predatory, nocturnal animals with a vividly decorated coat. They are often numerous locally; they linger in crevices (with their long antennae sticking out) during the day and hunt small benthic organisms at night, but they also feed on organic detritus whenever they happen across it. As with all crustaceans, the lobster moults or sheds its shell to grow.

Lobsters have recently suffered a dramatic demographic decline; intensive fishing has annihilated entire populations, especially where tourism abounds.

The lobster families that you may encounter are the spiny rock lobsters, Palinurida...

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Rock barren habitats

The marine habitats in which marine communities live are many and varied and are created, or caused, by a number of physical factors. These factors combine to determine which animal and plant communities can co-exist within a particular habitat, with the interplay of the communities themselves playing a large determining factor.

The physical factors include elements such as temperature, depth, tides and currents, relative salinity, wave action, light or shade, sea-bottom substrate, aspect and inclination. Extreme physical factors, such as a rise in sea temperature can have a significant and sudden impact on habitats, such as the El Nino effect on the coral reefs in the Maldives, where a small rise in sea temperature caused widespread coral bleaching.

In addition to the physical fact...

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Horse mussel

The horse or fan mussel (Atrina zelandica) is an endemic, filter-feeding bivalve mollusc that is particularly conspicuous because of its size and abundance. It often lives in groups that occupy 10 sq m or more, mainly on muddy-sand substrates of sheltered waters. It is widespread in the lowest intertidal and subtidal waters, including estuaries and harbours, but is also found in deeper waters of up to 50 metres off open coasts.

This filter-feeding bivalve produces waste biodeposits that are rich in organic matter and support animal aggregations that are distinctly different from, and more diverse than, those further away. Horse mussels therefore play an important role in enhancing habitat food supply and fuelling metabolism.

The horse mussel further enhances biodiversity on soft se...

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