Biodiversity in the Bay of Plenty

Biodiversity is short for biological diversity. It refers to the number and variety of living things (animals, plants or microorganisms) found within a particular area. There are complex relationships between this variety of life. Marine biodiversity specifically refers to the variety of life in coastal and ocean environments.

Biodiversity includes:

• genetic diversity – the different genetic make-up among individuals of one species
• species diversity – the different species within a habitat such as the birds, worms, fish, bacteria, insects and molluscs that live within an estuary
• ecological diversity – the different ecosystem types (estuaries, oceans, forests, wetlands, grasslands, streams) and the communities within them.

Marine biodiversity

Marine species make up almost one-third of New Zealand’s total number of described native species. However, about seven new marine species are identified each fortnight – many more are yet to be discovered. Scientists estimate there could be as much as 80% of New Zealand’s biodiversity living in the sea.

A species inventory for New Zealand was developed over the last decade through a project called Species 2000: New Zealand. This project formally identified about 12,000 marine species in New Zealand’s waters, with another 3,550 known but not yet described. It is estimated that, at the present rate of description, it would take another 100 years to describe the remaining marine species.

Described species include:

• seabirds
• marine mammals
• fish
• molluscs (snails, shellfish and squid)
• sponges
• echinoderms (kina, sea stars (starfish))
• seaweeds (rimurimu)
• microalgae.

Examples of all of these are found in various Bay of Plenty habitats.

Life in the estuaries

The soft estuary bottom (consisting of sand and mud, including sediment carried down by rivers) supports a range of burrowing fauna such as worms, cockles and pipi. Most of these animals feed on accumulated debris and bacteria and algae films on the mud surface. Estuaries are ideal refuges for juvenile fish of many species and wading birds in search of fish and crustacea.

Life in the beach zone

Bay of Plenty beach zones support abundant species such as shellfish – pipi, tuatua, biscuit shell, dog cockle and triangle shell. Sandhoppers can often be found jumping around in the debris left by an outgoing tide, called the wrack line. Terns and gulls often pick through debris. Pieces of driftwood often contain oyster borers and other insects. Fragments of dead seaweed such as sea lettuce and kelp are also common in this area.

Life on the rocky shore

The rocky shores support a huge diversity of life. Life here is not easy. Salinity, water, wave action, competition and predation are all factors affecting survival chances of life on the rocky shore. However, examples of many marine organism groups can be found there. Some examples are sea anemone, kina, sea cucumber, sea slugs, sea stars, pāua, crabs, chitons, sponges, worms, shrimp, barnacles, sea squirts, seaweeds, crayfish, octopus, fish, oysters and mussels.

Life around the offshore islands

These mostly volcanic rocky shores exposed to warm ocean currents support a unique diversity of subtropical marine life. In addition to species found on most New Zealand rocky shores, these habitats include long-finned boarfish, clown toado, crimson cleanerfish, the colourful splendid perch, Sandagers wrasse, copper moki and, in the summer, turtles.

The importance of biodiversity

New Zealand’s marine biodiversity is ecologically important because it is unique and of international importance – many of our species are not found anywhere else on Earth. Biodiversity also has intrinsic value – the value of the variety of life itself – and creates ecosystems that allow organisms to flourish in an interdependent web of life. Some of these species have commercial value to us as food and sources of potential medicines. Our relatively unspoiled marine environment also has economic value for tourism and our fishing industry. Finally, of cultural significance is that Māori have a special affinity with the oceans in a non-material way, and this is recognised in the Treaty of Waitangi.