Photic zone rock wall suspension feeding assemblages
Map ID Number: Not mapped during the workshop
Location: Rock wall assemblages are widespread in northeast New Zealand, offshore islands, and Fiordland. Other examples along the rest of New Zealand’s coastline include rock stacks, pinnacles, and similar formations.
Approximate area: Not recorded during the workshop
Description of habitat type:
The photic zone, or the depth to which light penetrates, is up to 200m. Rock walls have a vertical relief or a very high gradient. They are typified by strong to moderate currents
Biological attributes:
Rock walls are home to many iconic taxa including black corals, red coral, and brachiopods. They have a high biomass and surface cover of benthic species and a high biomass of planktivorous fishes. Such biomass is sustained by energy transfer from the surrounding ocean ecosystem. The habitat is characterised by very high feeding upon pelagic energy sources – by benthic/demersal species such as sponges, tunicates and/or bryozoans, brachiopods, hydroids, soft and hard corals, and a variety of planktivorous fishes. The environment is also a carbonate sediment “factory” for surrounding soft bottoms (Nelson et al. 1988). Non-geniculate coralline algae are particularly important as they cover very large areas of rock walls and are implicated in invertebrate settlement and recruitment.
Criteria applied:
Species diversity; species richness; endemism; dependency for other species; trophic/ functional diversity; representation (i.e. across physical types)
Status and management:
Most species are not exploited or directly threatened. Rock walls have high human appeal (e.g. for scuba divers). Populations are protected in New Zealand’s marine reserves.
State of information:
Some rock wall sites are very well known, especially in northeast New Zealand and Fiordland. Other sites are only locally known. They are best known within SCUBA range, but other deeper rock walls are known to occur.
References and further reading:
Battershill and Stocker (1993), Grange (1986).