Download in important in the economy of subtidal communities, greatly

in important in the economy of subtidal communities, greatly influencing the
distribution of seaweeds, including Ecklonia radiata (Ayling 1974a; Dromgoole
1964), and making available bare space for the settlement of invertebrate larvae
(Ayling 1974b).
X. Chaetognatha. Sagitta serratodentata and Pterosagitta draco are known from
the Jellicoe Channel (Jillet 1966, 1971). Unidentified arrow-worms from
plankton tows in the Goat Island channel probably belong to these species.
Y. Hemichordata. No hemichordate is known from the Reserve, but Saccoglossus otagoensis might be expected to occur in Glycymeris shell gravel. It
occurs in this habitat at Whangarei Heads.
Z. Chordata. Three species each of larvaceans and thaliaceans are components of
the plankton in the Jellicoe Channel (Jillet 1966, 1971) and probably occur in
the Marine Reserve. Ascidiaceans are represented by 40 species (Croxall 1972),
and Dr R.A. Cloney (pers. comm. 1976). Aspects of the feeding, growth rates,
settlement seasons of and predation pressure upon several species have been
studied by Croxall (1971). Ascidians generally occur in the same biotopes as
bryozoans and sponges where they may vie for space and food. Compound
species (e.g. Sigillinaria arenosa) may attain 43.2g/m on flat surfaces at 6m with
solitary Cenmidocarpa bicornuata producing 348g/m dry weight in the same
locality (Ayling 1968b). Biomass of both solitary and compound species appears
greater on flat surfaces than on slopes although this is variable.
The New Zealand lancelet Epigonichthys hectori occurs in sand off Goat
Island.
2
2
ZOOPLANKTON
The Zooplankton of the Hauraki Gulf and northern New Zealand has a
strong subtropical affinity, with decreasing numbers of species in common with
south-east Australia, South Africa, Great Barrier Reef, equatorial Pacific and
southern New Zealand. The Gulf zooplankton has been characterised by Jillet
(1966, 1971), who added considerably to the small amount of information that
previously existed (Kramer 1894, Fuller 1950, 1953), while Grace (1968)
further considered vertical distribution and diurnal migration of Gulf species.
The northern boundary of the outer Gulf is regarded as a line from Cape
Rodney to Cape Colville, with waters beyond this line as the Hauraki Gulf
Approaches (Taylor 1973) (q.v. section on Hydrology). Jillet's sampling station,
about 14km from Cape Rodney, was in the Approaches near the outer Gulf
boundary (in the Jellicoe Channel). His findings probably apply to the waters of
the Marine Reserve, since the species composition of the Jellicoe Channel is
strikingly similar to that of the Bay of Islands and open ocean. Only three
studies in the Reserve have contributed information on local zooplankton, viz.
those of Luckens (1966, 1970, 1975a), Foster (1965, 1967) and Barker (1971,
1976) with data on the identification, seasonal abundance and distribution of
barnacle nauplii.
Copepods represent the commonest holoplanktonic group (63% of the
44
catch by numbers), with larvaceans 12%, cladocerans 7%, salps 7%, euphausids
2% and hydromedusae, ctenophores, chaetognaths, pteropods and heteropods
making up the remainder. Of the 35 species of copepods from the Jellicoe
Channel, the seven commonest are Paracalanus parvus, Corycaeus aucklandicus,
Acartia clausi, Temora turbinata, Oithona similis, Euterpina acutifrons and
Oithona nana.
Meroplanktonic forms include larvae of amphioxus and ascidians, plutei
(ophio and echino), auriculariae, gastropod and bivalve veligers, cyphonautes,
actinotrochs, polychaete larvae, barnacle nauplii and cyprids and decapod zoaeae
together representing <7% of the average catch.
There are seasonal variations in the proportions of the various components. In
spring copepods are most abundant, especially Paracalanus, Acartia and Temora,
as well as Oikopleura and polychaete larvae. Copepods are scarcer in summer and
are dominated by Oikopleura, Penilia and Nyctiphanes. In autumn there are
invasions of salps, with high numbers of Temora, Oikopleura, Nyctiphanes,
Penilia, veligers, auricularians, plutei and Sagitta serratodentata. In winter there
are peaks of Paracalanus, Nyctiphanes, Oikopleura and Acartia, with Pleurobrachia well represented.
The data obtained by Jillet were gathered in 1964 and 1965. There are
differences between years in the seasonal and average annual catches, evidently
related to variations in sea temperatures and salinity, in turn related to long and
short-term variations in air temperature and rainfall (see sections on Hydrology
and Climate).
MARINE FLORA
The past decade has seen an increased knowledge of the diversity of marine
algae of local waters from the intertidal studies of Dellow (1955), Bergquist
(1957, 1959, 1960), Crossland (1965), Morton & Chapman (1968), Levis
(1975), Don (1975) and the plankton work of Cassie (1959, 1960, 1961, 1966),
Taylor (1969, 1970, 1973, 1974a,b) and his students (Lanigan 1972a,b, James
1972). There are more than 450 species of macroalgae and microalgae (including
cyanophytes) in local waters (including the Jellicoe Channel and Little Barrier
Island), but not a single species of the known marine fungi has yet been
identified. The importance of many of the species in an ecological framework
has been demonstrated in a number of works, especially those of Ayling (1968b,
1974a,b, 1975a,d), Starling (1967, 1968), Morton & Chapman (1968) and
O'Keefe (1969). Information on the occurrence, distribution and taxonomy of
many species can be gleaned from the algal herbarium and species lists at the
Leigh Laboratory and unpublished research data.
The following discussion treats macroalgae and microalgae separately.
Estimates of species numbers refer to an area bounded by Okakari Point, Little
Barrier Island and Matheson Bay.
Macroalgae
A. Taxonomy. Species numbers for the major groups of macroalgae are as
45