introduction		Storm barrens were discovered by Dr Anthoni in an extensive habitat survey done in 1993, work that has not been disproved. But please note that mainstream scientists are not supportive of this idea (yet).
rules for storm barrens		Because storm barrens are caused by a physical process, we can define a number of rules about them. This helps in further understanding the marine environment.
other barren areas		Barren zones or areas are places where large seaweeds cannot grow because storms remove them. We must not confuse them with places where there is not enough light or where there is extraordinary surface wave action.
ecology of the storm barrens		What are the main grazers of New Zealand's storm barrens?
examples		Examples of storm barrens in northern New Zealand and the Kermadec Islands
references		References to scientific journals.
Related chapters		Related chapters on this web site: Hauraki Gulf Survey 1993: our measurements of habitat zoning after the kelpbed death of 1993, leading to many discoveries. The snapper-urchin-kelp myth: how scientists misinterpreted the disappearance of the urchin barrens, a major scandal. Scientific research in NZ debunked: a critical dissection of some marine research done in NZ relating to urchin barrens. Introduction to marine habitats: what it means to live in the sea. Images of stalked kelp and its ecology.

-- Seafriends home -- marine environment index - marine habitat index -- updated:20070330,20070728,20090416,20120513,

After one such major event, a massive plankton bloom at the end of 1992, the kelp forest in a large area died and was successively removed by a tropical cyclone (hurricane) in January 1993. After the storm we did a preliminary survey and found good reasons to follow it up with a more thorough one in the (southern) winter of 1993 (See Hauraki Marine Survey 1993). Because we looked at many factors, we also made many discoveries, such as the full extent of the kelpbed death. For every site we recorded habitat boundaries along a vertical transect down the shore. This led to the first record of actually measured habitat boundaries (they were previously guessed at).

For some time we suspected that the depth of the sand bottom restricts waves as wave theory predicts, such that the maximum strength of the worst storm waves is proportional to the depth of the sand bottom. Hurricane waves are typically spaced over 400m apart, extending to a depth of 200m. When they arrive at the continental shelf, they are hindered by the sand bottom which becomes shallower as the waves approach land, draining their energy accordingly. So, by sorting the transects by their bottom depth, we could place them in order of worst wave exposure, and a consistent zoning diagram emerged.
 
 

From left to right wave exposure from exposed to sheltered (no scale possible). From top to bottom, water depth. The top two zones are taken by stringy Carpophyllum seaweeds which give way abruptly to a barren zone (pink), bordering the kelp forest. The kelp forest is bordered by the sand bottom with occasionally a narrow fringe of sponges. Above right a three-dimensional view with typical shore profiles plotted. Please note that the urchin barrens (pink) end when the bottom is shallower than 15m, and that a tough seaweed like the featherweed (Carpophyllum plumosum) takes over. Note that this diagram could be extended further into the sheltered shallows, but this was not the purpose of our survey. We also didn't record zoning on shaded shores. Note also that exposed shores become steeper as they become deeper.

Barrens without urchins To our surprise, we discovered that some barrens were not populated by urchins. Some of these were grazed by the strong grazing Cook's turban snail (Cookia sulcata) and some by the rainbow paua (Haliotis iris) but there were also some that had no grazers at all. Instead the barrens (that are devoid of kelps or macroalgae), were populated by colourful communities of turfing calcareous algae (pink turf), sponges and anemones. When we plotted these against the depth of the sand bottom, they followed a straight line. Note that sites 24 and 22 were located in very strong currents, known to erode the sand bottom as they shear past headlands (which moves their positions to the right in the diagram). These barrens without urchins vindicated our hypothesis that the barrens are indeed caused by storms. Because these discoveries were made in 1993 and have since not been proved wrong by mainstream science, we will introduce the word storm barrens for the general case. Urchin barrens are a special case when urchins are their main grazers.

• Here in New Zealand the top of the kelp forest is located at one quarter of the depth of the sand bottom. Worldwide, this boundary depends on the strength of the local kelp (or coral).
• Where storm barrens are grazed, this boundary may extend further down, and when the coast slopes gently while no deeper than 20m, there may not be a kelp forest at all due to grazing.
• The maximum strength of storm waves is limited by a gently sloping continental shelf, but where such a shelf does not exist (as in Niue and the Kermadec Islands), storm waves arrive with maximum strength, capable of changing all zones into a single barren zone extending from the surface down to 40-80m.
• When the sand bottom is shallower than 15m, there cannot be a barren zone (in NZ). This explains why there are no storm barrens along New Zealand's west coast where the sand bottom is 5-10m deep at the bottom of a rocky shore.
• Storm barrens are usually contiguous zones but can be patchy as they are created first on rocks extending out above their surroundings. They are likely to be patchy in border cases.
• Storm barrens are absent on sheltered coasts, regardless of their depths.
• Vertical storm barrens are difficult for major grazers like sea urchins and snails, reason for their absence.

This diagram shows how loss of light due to murky water creates a barren area where normally none would be expected. On left a healthy situation with shallow stringy seaweeds (fucalia), an urchin-grazed storm barren, a kelp forest (laminaria) and a deep reef habitat with sponges. When the water is clear and healthy, there is standing room only in an environment which is rich in variety. But degrading water quality pulls the lower light boundary up, while also diminishing density and diversity. Eventually the whole shore becomes barren, devoid of the species one would have expected there. In the end also crustose coralline algae (pink paint) disappear.

f033810: due to murky water, the kelp boundary has moved up and these grey sponges are infested and dying. The whole barren area extends from 6m down. Martins Bay. Note how the pink paint has become patchy. Note also that one cannot take overview photos due to severely limited visibility.

f036804: the kelp forest is dying even though there is enough light. There are no young plants (recruits) and there are no sea urchins. This becomes a barren zone caused by degradation of water quality. Arid Island.

f043124: a diver swims into Rikoriko cave at the Poor Knights, where the barrens are densely populated but where seaweeds cannot grow due to weak light. Notice the large purple urchins. These barrens are caused by lack of light. f020032: life inside an archway can be very rich because the current brings food. But plants can't grow here. Notice the purple urchin in the foreground. Apparently it can live from animal life. Poor Knights.

f030621: purple urchins have carved out a barren patch in a sheltered place. This is not a storm barren. Poor Knights.

f029902: purple urchins (Centrostephanus rodgersi) and their local barren. Notice the many sockets in the rocks, carved by generations of urchins. Poor Knights.

f036012: strong grazers like sea urchins and large snails can easily fall off steep rock faces, reason why they are easily bared. This is a boundary case of a storm barren. Deadmans fingers Alcyonium sp. Mimiwhangata.

f033926: a storm cleared a high patch on a boulder and urchins occupy its sheltered side, which has been cleared completely compared to the exposed side. Note that urchins do not need to graze because they can catch broken seaweeds. Mayor Island.

f007213: a storm cleared a high boulder and sea urchins are grazing it further. Notice how they are penned into their patch by the steep sides of the boulder. By staying closely together, they resist attacks from predating starfish, whelks and fish.

The main grazers of the storm barrens in NZ are:

• green or common urchin (Evechinus chloroticus): the main tree feller and clearer of the barrens, always hungry, prolific spawner, partly roaming, partly homing to its socket.
• purple urchin (Centrostephanus rodgersi): mainly outer islands, strong grazer but sensitive to waves, patchy, homing.
• rainbow paua (Haliotis iris): maintains very smooth patches, clears larger seaweeds, hungry, homing, becoming rare.
• Cook's turban snail (Cookia sulcata): strong grazer, takes over where urchins leave, systematic, roaming.
• trochid top snails (Trochus viridis): minor grazer but common, does most of the small work, erratic, roaming.
• catseye snail (Turbo smaragdus): not a strong grazer; picks the 'low-hanging fruit', not systematic, hungry, roaming.
• radiate limpet (Cellana radians), ribbed limpet (Cellana denticulata): slow feeders, sleep a lot, systematic, prolific spawner, homing.

f001319: urchins do the ground work by night while they shelter inside their sockets by day. Large Cook's turban shells do some rough grazing whereas the finer work is done by smaller catseyes, top shells and limpets. Goat Island.

f001932: a cluster of sea urchins at the sheltered side of a protruding rock. The habitat is barren as far as the eye can see. Goat Island marine reserve Waterfall Reef June 1995. Note that the kelp has not yet invaded this habitat, contrary to what scientists claim!

f035721: detail of overlapping fronds of pink paint. The whitish spots are dead because some organism once grew there (sponges, kelp). Dark red patches are a different species.

f036235: the Cook's turban snail (Cookia sulcata) is a powerful grazer but sea urchins need to do the clearing first. A variable triplefin sits on its shell. The shell's rate of growth (and health) is revealed by a band of bare shell.

f006828: a lonely sea urchin about to clear-fell the last kelp tree on its patch. Once the plant is bleeding, other urchins are attracted. Mayor Island.

f033937: a marblefish has also made use of a barren patch by meticulously trimming a stand of sea lettuce, thereby encouraging it to grow very densely. No other grazers allowed here! Mayor Island.

f007210: a lot of food in the form of sea lettuce is found above the urchin zone but it is too risky to go there. This shows the subtle difference between urchin barren (below) and storm barren (above). Mayor Island.

f045604: the urchin barrens support a highly productive and diverse community. In the photo the green sea urchin (Evechinus chloroticus), top shells (Trochus viridis), a stellar limpet above (Cellana stellifera), an unidentified limpet perhaps (Cellana radians), and a host of tiny snails. Notice the various forms of crustose calcareous algae (Lithothamnion spp.). Mimiwhangata.

f049611: detail of some little actors on the urchin barrens. Notice the rough terrain created by some crustose calcareous algae possibly Corallina officinalis. Cavalli Islands.

f022424: Demoiselles to lay their nests of eggs, need barren rock as shown here. The blue males guard the eggs while the green females feed in the currents. Demoiselles keep the rock face free from small snails and they even prod sea urchins along. Poor Knights.

f048302: demoiselles have cleared their rocks from grazers, but are thereby allowing the sea lettuce to invade. Poor Knights.

f017317: as the kelp boundary moved up due to increasing murkiness of the water, it left behind a barren area where sponges fight deposition by mud. Martins Bay.

f017316: sponges in a degrading environment enjoying the cleaning services of sea cucumbers (Stichopus mollis). Martins Bay.

f036001: a colourful storm barren with isolated shrubs of tangleweed (Carpophyllum flexuosum). The tangle weed has been trimmed by storms and it is too tough for sea urchins to eat. Notice the many white sea anemones. Mimiwhangata.

f045827: urchins in a diverse storm barren with red carpet sponges, large grey sponges, white anemones, tangle weed and pink coralline algae. Apparently the carpets can repair themselves rapidly. Notice how all urchins sit on pink paint patches. Guess who's eating the sponge carpets? Mimiwhangata.

f051809: a storm barren covered in encrusting sponges (Crella incrustans) that survive the gnawing from sea urchins as the only grazers. Cuvier Island.No macroalgae at this depth

f020605: short red seaweeds (Champia spp) and a flat tough green seaweed (Gigartina sp) surviving in a storm barren where urchins can't. Poor Knights.

f051822: turfing calcareous algae dominating in a very exposed storm barren. Cuvier Island.

f020915: detail of turfing calcareous algae in a storm barren. Hahei.

f036520: detail of turfing calcareous algae in a storm barren. Cape Brett.

f034100: detail of one of the toughest calcareous algae in a storm barren. Mayor Island.

f036523: detail of a most varied storm barren coralline garden - standing room only. These plants made from bits of stone hinged together, are able to survive the most exposed conditions. Cape Brett.

f049016: a storm baren covered in jewel anemones and encrusting sponges. No unoccupied space left. Truelove Reef Cavalli Islands.

f028104: a sheer storm barren cannot be populated by urchins,  for once they fall down, they cannot make it back up again. Cape Brett Pearcy Island.

f051912: a very rich storm barren at a very exposed pinnacle. In the distance nothing but storm barrens. Never Fail Rock, Mercury Islands.

f051900: detail of the storm barrens around Never Fail Rock. Huge diversity. Standing room only. No urchins.

f031419: storm barrens on a basalt bommy at Raoul Island, Kermadecs. Two kinds of urchin and a large snail in the foreground. Note that there are no large seaweeds (kelps) at the Kermadecs, possibly because the storm barrens extend over the whole photic (light-) zone.

f031804: storm barrens populated by large urchins (Centrostephanus rodgersi) a far as the eye can see. McDonald's Rock, Kermadecs.

f047302: Because Niue island does not have a continental shelf, hurricane waves can arrive with exceptional strength, creating storm barrens from the surface down  to 80m deep, where no branching corals can survive. See Niue ecology

f047110: At night millions of sea urchins appear from their dens and tunnels in the soft rock, to graze the film of algae. Notice their scrape marks. Molluscs like seashells also join in.All have safe dens against storms.

You may now be interested in the extensive rebuttal of the urchin barrens myth, the ecology of the Kermadec Islands and that of Niue. Perhaps also in why marine reserves in NZ are disappointing.

• Babcock R C, R G Cole: The extent of die-back of the kelp Ecklonia radiata  in the Cape Rodney to Okakari Pt Marine Reserve  Advice to the Department of Conservation, June 1993
• Babcock R  C, Shane Kelly et al: Changes in community structure in temperate marine reserves   Mar Ecol Prog Ser 189:125-134 (1999)
• Chang F H, Shimizu Y, et al.: Three recently recorded Ostreopsis spp. (Dinophyceae) in New Zealand: temporal and regional distribution in the upper North Island from 1995 to 1997. New Zealand Journal of Marine and Freshwater Research, 2000, Vol. 34: 29-39
• Rhodes L, Adamson J, et al.: Toxic marine epiphytic dinoflagellates, Ostreopsis siamensis and Coolia monotis (Dinophyceae), in New Zealand. New Zealand Journal of Marine and Freshwater Research, 2000, Vol. 34: 371-383
• Schiel David R, Michael J H Hickford (2001): Biological structure of nearshore rocky subtidal habitats in southern New Zealand. Science for Conservation SFC182, Dept of Conservation, New Zealand (available free on the web)
• Shears Nick T, Russell C Babcock: Marine reserves demonstrate top-down control of community structure on temperate reefs  Springer Verlag May 2002.
• Shears NT, Babcock R C (2004): Indirect effects of marine reserve protection on New Zealand's rocky coastal marine communities.  DOC Science Internal Series DSIS192. (free on the web)