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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