![Thumbnail: [Volume 81, 1953 page 196]](/journals/rsnz/images/rsnz_81/thumbnails/rsnz_81_02_0295_0196_ac_02.gif)
Flora
Cystophora scalaris. Range: E.L.W.N. to below E.L.W.S.; 25% to 0.0% exposure.
This species is characteristic of the infralittoral fringe in sheltered to semi–exposed situations. Where wave action is strong it is absent. It is also absent on the rocky shore adjacent the sandy beach where there is considerable scour. Its upper limit is rather well defined, an occasional plant only being found above E.L.W.N. Above this level, however, it colonizes rock pools, especially on level platforms sheltered from direct wave action. Here, mixed with Carpophyllum maschalocarpum, it forms a dense fringe round the edge of the pools.
Carpophyllum maschalocarpum. Range: E.L.W.N. to below E.L.W.S.; 25% to 0.0% exposure.
The distribution of this species is very similar to that of C. scalaris, the two species being generally found together with C. maschalocarpum numerically more important. It is somewhat more tolerant of exposure to surf than C. scalaris, and is found on very exposed coasts where the main force of the waves is broken by rocks and ledges. The presence of a stony beach, subject to movement, in many localities prevents the development of both species.
Where the Carpophyllum zone is well developed the upper limit is rather sharply defined at E.L.W.N., with an occasional plant higher up. On outer coasts, sheltered from direct wave action, but subject to a strong surge, the upper limit of the zone may be elevated several feet. The lower limit lies below E.L.W.S., never reaching more than two feet below.
Macrocystis pyrifera. Range: M.L.W.N. to below E.L.W.S.; 10% to 0. 0% exposure.
The presence of this brown kelp is a characteristic feature of the stretch of coast studied. A Macrocystis zone is usually well developed except, (a) on outer very exposed coasts, (b) on vertical more or less wave beaten faces and (c) where the rock is replaced by sand near the low water mark. Relatively deep water is required for the development of the species, the holdfasts occurring up to 50 feet below E.L.W.S. The floating fronds form a conspicuous band stretching up to 250 feet out from the low water mark. Its upper limit is well marked at M.L.W.N. and the best development occurs from M.L.W.S down. Unlike the other local kelps (Cystophora, Carpophyllum, Durvillea willana and D. antarctica) Macrocystis is tolerant of a wide range of conditions of exposure to wave action, being common in the most sheltered situations where the water is deep enough. Under such conditions, where there is very little swell, the upper limit does not extend above M.L.W.S.
Durvillea willana and Durvillea antarctica. Range: M.L.W.N. −0.5 ft. to below E.L.W.S.; 15.0% to 0.0% exposure.
On the outer exposed coast these are the best developed of the kelps, being indicators of localities subject to strong wave action. In such localities there is usually a band of Durvillea from M.L.W.N. down, unless the rocks end in steep plunging cliffs. Thick growths occur where the rock surface is sloped, the plants being absent from level platforms. Optimum development is found on the rocky broken points of exposed headlands. Fairly deep water immediately offshore is necessary for the growth of Durvillea as it is absent where there is sand near the low water mark.
![Thumbnail: [Volume 81, 1953 page 197]](/journals/rsnz/images/rsnz_81/thumbnails/rsnz_81_02_0296_0197_ac_02.gif)
The upper limit of the Durvillea zone is generally clearly defined at M.L.W.N. In situations where there is a strong surge the upper limit may extend up to 1.5 feet above this level. The lower limit is also clearly defined, lying just below E.L.W.S. Where Durvillea is growing on smooth, steep slopes it is often the single dominant species with a poor underflora consisting almost entirely of “Lithothamnion”. In semi–exposed situations the “Lithothamnion” is replaced by species of Corallina, Gigartina, other red algae and Halopteris. Where the rock is rough and broken Durvillea is co-dominant with Mytilus canaliculus, with which it competes for space, the spaces between the holdfasts having a dense carpet of mussels.
Both species of Durvillea may occur together or one species may be locally dominant. D. antarctica appears to be somewhat more tolerant of wave action than D. willana. The type of substrata also has an effect on the development of these species, D. willana being absent from steep, smooth faces where D. antarctica occurs in abundance. Where the species occur together they may be mixed throughout their vertical range, or D. willana may form a band on the seaward side of D. antarctica. This separation of the two species into two distinct sub-zones is particularly noticeable where flat rocks occur in the region of M.L.W.S.
Codium adhaerens var. convolutum. Range: E.H.W.N. −1.0 ft. to M.L.W.N. −0.3 ft.; 60% to 10% exposure.
The distribution of this species is rather scattered, being determined by the amount of shade and the degree of exposure to wave action. It does not grow on faces exposed to direct sunlight, being well developed on the west shaded side of the bay. On faces that do not receive any direct sunlight the upper limit of the species is elevated to M.H.W.N. C. adhaerens does not tolerate strong wave action, being confined mainly to sheltered situations, with local occurrence in regions of moderate exposure. The flattened, fleshy growths of this species are best developed on more or less vertical faces and grow well on smooth surfaces. Where the patches of Codium spread over the rock surface all other plants and animals are excluded, apart from epiphytic algae such as Colpomenia and the herbivorous gastropods, Onchidella patelloides, Lunella smaragada, Rizellopsis varia and Siphonaria australis. Often a bare area of rock surrounds the radiating growths of this species. Dellow (1950) states that at Narrow Neck Codium grows over the sandy Sabellid and calcareous Pomatoceros tubes. At Taylor's Mistake no such growth has been observed on the Pomatoceros tubes.
Bostrychia arbuscula. Range: M.H.W.S. to M.H.W.N.; 98% to 82% exposure.
This is another shade loving species attaining its best development on the west shaded side of the bay, where it forms a conspicuous band above the main barnacle growth. In moist shaded crevices the upper limit may extend up to 1.5 feet above M.H.W.S. The lower limit appears to be relatively constant, occurring above the “Barnacle-line”, where the main growth of Chamaesipho columna ends. Scattered specimens of barnacles may occur in the Bostrychia band. This alga does not tolerate direct wave action, being found only in sheltered and semi-sheltered situations. It is tolerant of freshwater seepage from above.
Corallina officinalis. Range: M.H.W.N. −0.3 ft. to below E.L.W.S.; of 75% to 0.0% exposure.
This cosmopolitan species is extremely tolerant with regard to intensity of
![Thumbnail: [Volume 81, 1953 page 198]](/journals/rsnz/images/rsnz_81/thumbnails/rsnz_81_02_0297_0198_ac_02.gif)
surf action and the nature of the substratum. It occurs in pools at all levels up to E.H.W.S., forming a dense fringe round the edges of the deep pools on the lower half of the shore and covering the bottoms of the shallower ones. The upper limit of the species is rather variable, depending on the degree of exposure to wave action and the type of substrate. In sheltered areas it may extend up to E.H.W.N., growing on the barnacle encrusted rock; but on the open shore, as found by Evans (1947a), it is more characteristic of the levels below M. T. L. At Taylor's Mistake, as at Cardigan Bay, Wales, it is one of the most tolerant of the littoral algae with regard to wave action. On steep, exposed, vertical faces it may often be the only alga present, forming a turf of short plants from the lower limit of the barnacles down to E.L.W.S., and extending into the infralittoral.
On the open coast Corallina may also form the main species of the underflora of the Durvillea zone, extending as a thick carpet on the rock surface below Cystophora and Carpophyllum in the less exposed areas. It is also present in the most sheltered situations and extends to the rocks near the sandy beach, being tolerant of periodic coverage by sand. It grows equally well on all types of substrate, including soft red scoria on which other species are absent. Where patches of this rock occur the upper limit of Corallina zone may be several feet higher than on the adjacent basalt rocks.