Inter-tidal Ecology at Narrow Neck Reef — DELLOW 
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Carpophyllum flexuosum (d) 
Sargassum undulatum (f) 
Sargassum sinclairii (f) 
Cy stop bora torulosa (f) 
Ectocarpus indicus (f) (summer) 
Glossophora kunthii (la) (summer) 
Pterocladia lucida (1) 
Myrio gramme gatty ana (1) 
Zonaria subarticulata (o) 
Cyst op bora retro flexa (o) 
Cladbymenia oblongifolia (o) 
Acrosorium decumbens (o) 
Scbizymenia novae-zelandiae (r) 
Grateloupia polymorpha (r) 
Myrio gramme oviformis (f) (summer) 
The present account is intended to deal 
only with communities of the inter-tidal re- 
gion; but since the dominant species in the 
sublittoral fringe (i.e., between 0.6 and 0.0 
feet) include those of the Carpophyllum — 
Ecklonia association, it will be discussed here. 
An association in the sublittoral region 
dominated by one or more species of Carpo- 
phyllum is characteristic of rocky districts of 
the east coast of New Zealand (Oliver, 1923). 
Narrow Neck is no exception. The only New 
Zealand species not present is C. elongatum, 
the chief ecological requirement of which 
is deep, transparent water (Cranwell and 
Moore, 1938). At Narrow Neck, Carpo- 
phyllum and Ecklonia are present almost 
everywhere within their bathymetric limits. 
C. plumosum dominates in shallower and 
more sheltered habitats, and is especially com- 
mon on the protected western fringe of the 
Main Reef (Fig. 1). C. maschalocarpum is by 
far the most abundant of the three species of 
Carpophyllum in the locality. It extends al- 
most continuously from the base of the tide 
pole on Crab Island, round the seaward face 
of the latter, and along both sides of the 
Main Reef ( Fig. 1 ) . In the shallower chan- 
nel between reef and shore C. plumosum and 
Ecklonia radiata are more physiognomic. The 
latter is equally abundant on both eastern 
and western fringes of the reef. In general, 
C. flexuosum is more typical of deeper water 
than C. maschalocarpum and C. plumosum, 
though all three flourish about A.H.B. 
Datum. 
The upper limit of the association is re- 
markably constant. There appears to be a 
gradation in length of thallus which increases 
with depth at which the holdfasts are at- 
tached. This may be a response of the indi- 
vidual plants in connection with the optimum 
depth of water for photosynthesis. 
A heavy epiphytic flora and fauna is sup- 
ported by mature thalli of the large brown 
algae, and is composed mainly of diatoms, 
hydroids, and delicate red algae such as Myri- 
ogramme oviformis and Acrosorium decum- 
bens. The abundance of diatoms is enhanced 
by the relatively slack tidal currents and the 
prevailing turbidity of the water. 
Seasonal Communities 
Porphyra umbilicalis and Bangia vermi- 
cularis form a winter aspect society on ex- 
posed ledges between M.H.W.N. and M.H. 
W.S. Bangia usually persists until summer. 
About the level of M.L.W.N., spring and 
summer communities of Myrio gloia lindauerii 
and Helminthocladia australis may be found. 
Both species are influenced adversely by sand. 
Towards the lower limit of the balanoid 
association, Splachnidium rugosum grows in 
dense or isolated patches in late summer and 
autumn, dying away with the onset of winter. 
Seasonal species do not, as a rule, reappear 
the following year in exactly the same situa- 
tion as in the previous one. 
Several points which require further com- 
mentary arise out of this discussion of the 
different associations: 
1. The upper and lower limits given in 
feet represent the average for each as- 
sociation concerned, and do not imply 
that the dominant species cannot live 
at other levels. For instance, the lower 
limit of the balanoid association is 3.6 
