In an earlier paper (Boney, 1973) the skeletal variations, and their quantitative significance, were described for autumn collections of Dictyocha speculum obtained with a 600 m.p.i. tow-net from surface waters in the Fairlie Channel, Firth of Clyde, in 1970. It was shown that skeletal abnormalities constituted a very small number (1·78%) of the 6025 skeletons examined. In these same samples numerous double skeletons were observed. These are regarded as pre-division stages (Gemeinhardt, 1930; Hovasse, 1932; Marshall, 1934), in which the replica of the first skeleton usually has thinner tubular skeletal rods (Marshall, 1934). A detailed examination of these double skeletons was undertaken to determine whether true mirror-imaging occurred, and the extent to which a ‘normal’ skeleton was joined to a partner of aberrant form. The methods used to obtain slide preparations in glycerine jelly were described in the previous paper (Boney, 1973) and the terminology of the components of the skeletal unit are also the same (Fig. 1A–C).

A new species of Hymenomonas Stein, Hymenomonas lacuna sp.nov. from San Juan Island, Washington, U.S.A. is described using light and electron microscope techniques. The cells normally occur in non-motile clumps growing on the sides of the culture vessel. Each cell has a body covering composed of a single layer of coccoliths of unusual construction and several layers of circular unmineralized rimless scales. Occasional small elliptical scales are sometimes found.

The general cytology of the cells is discussed with special attention paid to the unusual pyrenoid and the role of the Golgi body in scale and coccolith production.

The relationship of this species to H. roseola Stein is discussed.

Since the appearance of the first documentation of marine algae from within the political boundaries of eastern Canada (South & Cardinal, 1970), a sufficiently large volume of new information has become available to warrant the revision presented here. Taxonomic and systematic changes, together with further additions, corrections and emendations are incorporated as far as possible. A total of 346 species, subspecies and varieties are listed, comprising 131 Rhodophyta, 127 Phaeophyta and 88 Chlorophyta. The treatment is largely restricted to macroscopic forms. Inclusion of microscopic species of Chlorophyta and representatives of other marine Phyla is planned for the future.

By the death on 14 December of Professor Sir James Gray, K.T., C.B.E., M.C., Criox de Guerre, M.A., Sc.D., LL.D., F.R.S., at the age of 84, both zoology and marine biology have lost one of their great figures. His connexion with the Marine Biological Association of the United Kingdom stretches from his first visit as a research worker to the Plymouth Laboratory in 1912, when he became a member of the Association, through his long service on the Council (first in 1920 and then continuously from 1928 to 1969), to his Presidency (1945–55) and his election as Vice-President in 1955 and Honorary Member in 1965. He was also a member of the Scottish M.B.A. since 1921 and served on its Council for six years (1960–66) and was elected a Vice-President in 1965.

The Preliminary Check-list of British Marine Algae (Parke, 1953), with three subsequent lists of additions and corrections (Parke, 1956,1957,1959), was superseded by the Revised Check-list of British Marine Algae (Parke & Dixon, 1964) and the Check-list of British Marine Algae - Second Revision (Parke & Dixon, 1968). Since the publication of the 1968 list, changes, both taxonomic and systematic, have been sufficiently numerous to warrant the present list incorporating further additions, corrections and emendations.

INTRODUCTION

Studies of established populations of Laminaria hyperborea (Gunn.) Fosl. have indicated that there is often less change of growth rate with depth than might be expected to result from the decrease in irradiance (Kain, 1967; Lüming, 1969; Jupp & Drew, 1974). This has been attributed to self-limitation by the canopy of Laminaria fronds (Lüning, 1969; Kain et al. 1976). The removal of this canopy can result in fast growth in shallow water (Kitching, 1941; Svendsen, 1972) and a marked differential in growth rate over a small depth range (Svendsen, personal communication). A series of rocky subtidal areas at two depths off the Isle of Man was cleared of vegetation at various times (Kain, 1975a). This provided an opportunity to make growth measurements on individuals of known age in the absence of a canopy formed by older plants.

The Celtic Sea extends from the south of Ireland and the St Georges Channel across the continental shelf, with the Bristol and English Channels as its eastern limits (Fig. 1) (Cooper, 1967). Although various investigations of the physical oceanography (Matthews, 1914; Cooper, 1967) and zooplankton (Russell, 1934, a, b, 1936; Corbin, 1947; and more recently Southward, 1962; Bary, 1963) of this area have been carried out, there is little or no information on seasonal changes in levels of chlorophyll ‘a’ and inorganic nutrients, and on the importance of tidal mixing in determining these distributions. Since the speeds of the tidal streams range from weak (∼ 0.5 knot) in the northern part of the Celtic Sea to strong (∼ 3 knots) around the Scilly Isles and Ushant (Fig. 2), the vertical stability of the water column as well as the duration of the seasonal thermocline (Pingree, 1975) are likely to be important factors in determining spatial and temporal variations of phytoplankton production. In this paper the influence of water-column stability on phytoplankton distributions (in spring, summer and autumn) in the Celtic Sea is described, using data for temperature, salinity, chlorophyll ‘a’ and inorganic nutrients obtained during seven cruises in 1975. An account of the red tide conditions that occurred in late July to the north-west of Ushant has already been published (Pingree, Pugh, HoUigan & Forster, 1975).

Population growth and concentration factors for 65Zn and 137Cs have been measured for Achnanthes brevipes Agardh, Carteria sp. Diesing, Chlamydomonas sp. Ehrenberg, Dunaliella salina Teod., Nannochloris atotnus Butcher, and Phaeodactylum tricornutum Lewin subjected to factorial combinations of eight temperatures (6–40 °C) and ten salinities (3.5–44.0 p.p.t.). Regression coefficients were calculated for polynomial models describing response surfaces for growth and radionuclide concentration. Salinity was more important than temperature in describing population growth for Carteria, Dunaliella, Nannochloris and Phaeodactylum. No independent variable was consistently of primary importance in describing 137Cs concentration factors, while temperature accounted for more variation in 65Zn concentration factors than salinity or population growth in all algae except Dunaliella. Concentration factors for 65Zn were uniformly higher than 137Cs concentration factors.

A new flagellate alga is described which has the flagellar apparatus characteristic of the genus Pavlova, but not the external particles on the cell body. The minute particles on the long flagellum contain acid polysaccharide. Paramylon and polyphosphate occur as vacuolar inclusions. A peroxide resistant layer is present in the superficial cisterna. The opposite membranes of the superficial cisterna differ considerably in structure. A diagnosis is given and taxonomic relationships are discussed.

INTRODUCTION

Pavlova gyrans Butcher, the type species of the genus, was described at the light microscope level in 1952 (Butcher, 1952). Since then this species has been re-investigated with the electron microscope (Green & Manton, 1970), a number of other species described from marine, brackish and freshwater habitats (for literature, see p. 600) and at least two new genera erected which appear to be closely related to Pavlova (Corcontochrysis Kalina, 1970;Exanthemachrysis Lepailleur, 1970).

INTRODUCTION

Little is known about the early growth history of solitary corals in relation to the substrates to which they are attached. An understanding of this relationship between coral and substrate, and of how it may change throughout the life of the coral, is particularly important in studies of the life history and ecology of solitary corals living in sand and other soft sediments. A knowledge of the variety of different substrates to which solitary corals are attached in the wide range of different environments in which they live is also of importance to the palaeontologist when attempting palaeoecological interpretation of transported coral debris.

A knowledge of the growth rates and feeding behaviour of planktonic copepods at natural food concentrations is important for an understanding of food-chain dynamics in the sea. In many areas of the open oceans average concentrations of particulate organic carbon rarely exceed 100 µ carbon 1-1, and even in coastal regions the maximum levels are probably only one or two orders of magnitude higher (Parsons, 1975). Thus, most herbivorous marine copepods live in a nutritionally dilute environment (Conover, 1968). In contrast to natural conditions, many laboratory investigations have been carried out at unnaturally high food concentrations, often more than one order of magnitude higher than those which might be expected in the sea.

A new member of the Haptophyceae, Corymbellus aureus gen. et sp.nov. is described. The cells of this species are aggregated into motile colonies which are more or less spherical at first, but which become annuloid as their size increases.

Individual cells are large and rather irregular in overall morphology with two heteroor homodynamic flagella and a short non-coiling haptonema arising from an anterior apical groove or furrow. Two types of oval body-scale are present; the larger, with upturned rim and a short central spine, are generally distributed, whilst the smaller, lacking such ornamentation, are confined to the apical groove.

INTRODUCTION

In the genus Laminaria the origin of the growth of the frond (blade, lamina) is known to be the meristematic transition zone between frond and stipe. Parke (1948) showed, by observing holes punched in the frond, that the fastest rate of growth in length in L. saccharina (L.) Lamour. was in the proximal 25 mm. However, during measurements of the rate of growth of fronds of plants of known age on previously cleared areas (Kain, 1976), it was noted that in L. hyperborea (Gunn.) Fosl. the maximum rate of elongation occurred at some distance from the transition zone. This led to an investigation of the whole pattern of growth, in terms of elongation, increase in area, decrease in thickness and change in cell size and numbers over the surface of the frond at different stages.

INTRODUCTION

Between 4 May 1973 and 29 March 1975 we did not visit Duckpool. Indeed after the 1973 visit (Wilson, 1974, pp. 429–30) the intention had been to discontinue observations on colony formation and growth, for it seemed unlikely that much more data of value were obtainable, and that is still true. However, at Easter 1975 Monsieur Yves Gruet, who has done much excellent work on Sabellaria associations on the coast of France (references in Wilson, 1974), visited Plymouth with his family and wished to see Duckpool. We went there on 29 March and arising out of that visit my wife and I were again there the following October, with one main object in view as explained below, and this in turn led to a further visit in November. This paper records observations made during those visits.

The majority of barnacles are sublittoral and limited to full strength sea water, but a number of thoracican species are amongst the most conspicuous and successful members of the littoral and brackish-water faunas. Salinity fluctuations are a feature of most littoral and brackish habitats, but the importance of salinity as a stress factor is variable. In many open coast situations, intertidal barnacles are likely to be subjected to lowered salinity levels only when emersion coincides with heavy rainfall or pronounced terrestrial run off. For these animals, behavioural adaptations to prevent irrigation of the mantle cavity by dangerously dilute sea water may be sufficient protection against an irregular, transient factor in their existence, overshadowed in importance by temperature fluctuations and the desiccating influence of aerial exposure.

In an earlier paper (Gibbs, 1973) it was shown that in populations of Golfingia elongata (Keferstein) in the Plymouth area, a significant proportion of individuals possess fewer retractor muscles than is typical for the species. These individuals have three or two retractors instead of the normal four (= subgenus Golfingia) but otherwise are typical G. elongata in all characters. A morphologically similar species G. rimicola Gibbs is also common in the area and this species differs in possessing only two retractor muscles (= subgenus Phascoloides). One possible reason for the presence of aberrant individuals with an intermediate number of retractor muscles is hybridization; if the spawning seasons of the two species overlap in time, then cross-fertilization could be a feasible explanation for this anomaly.

INTRODUCTION

A comparative survey on the capacity of several nitrogenous compounds to support marine phytoplankton growth showed urea as the best and D-glucosamine as the poorest supplier of organic-nitrogen at a concentration of 500 /g-at. N per litre (Antia et al., 1975a). The quality and degree of growth on glucosamine was always so inferior that the evidence appeared insufficient to establish whether this compound was actually being metabolized by the algae. By analogy with the substrate-utilization kinetics reported for growth of other micro-organisms such as yeast (e.g. Tseng & Wayman, 1975), the probability was considered that the glucosamine concentration used in the above survey may have been too low for adequate uptake under the test conditions chosen and that elevated concentrations, in facilitating such uptake, may provide unequivocal evidence of algal capacity for metabolism and utilization of this substrate. However, such concentration elevation would require to be below levels that may become inhibitory to growth, and these inhibitory levels may themselves vary from one species to another. Antia & Chorney (1968) reported 5 mM glucosamine to be toxic to growth of the cryptomonad Hemiselmis virescens, whereas McLachlan & Craigie (1966) observed growth of the diatoms Cyclotella cryptica and Thalassiosira fluviatilis on five times this level of concentration.

The specific growth rate of Dunaliella tertiolecta was unaffected by mercury II concentrations of at least 2.03 μg at/1. At 10 μg at/1, it was eventually reduced by 84% but growth continued, giving a final level of cell material only 13% below that in a mercuryfree control. At this concentration, however, growth was largely uncoupled from division and giant cells were produced, probably due to the effect of mercury upon the production of methionine which is known to be implicated in the process of cell division.

The basis of the mercury tolerance was investigated in terms of (1) mercury detoxication in the culture medium by complex or compound formation between the metal and metabolites produced by the cells, (2) the concentration of sulphydryl groups both within the cells as possible sequestration sites and in the cell membrane where any molecular disruption and permeability changes produced by the metal first occur, (3) the absence of cellular potassium leakage and (4) the resistance of the cell membrane to the uptake of mercury II ions. Where possible, the results were compared with those from determinations of the same properties of the mercury-sensitive species Isochrysis galbana. The experiments indicated that the mercury tolerance of D. tertiolecta is partly related to the slower rate of mercury accumulation by this species, but is largely due to the detoxication of the mercury within the cell possibly by the precipitation of a highly insoluble mercury compound

INTRODUCTION

Work on pumping and filtration rates of bivalve molluscs was initially concerned with the physiological concept of pumping water through the mantle cavity. Comprehensive reviews are given by Winter (1970) and Ali (1971). The methods are of two kinds; direct, in which the flow of exhaled water itself is measured, and indirect, in which the rate of clearance of food particles is used to calculate water flow through the gills.

There is a disadvantage in the indirect method when used to calculate volumes of water pumped because it involves the assumption that a fixed percentage (often 100% with large particles) of the particulate matter passing through the gill system is retained. Pumping rate is thus estimated as a function of the particle collecting properties of the latero-frontal cirri, whereas the water current is produced by the lateral cilia. Although the structure of the latero-frontal cirri is now well documented (Moore, 1971), their efficiency in particle retention can alter under certain conditions (Dral, 1967). There is need, therefore, for direct measurement of the quantity of water pumped. Recent advances in the understanding of branchial innervation and the control of lateral ciliary activity also reinforce this point (Aiello, 1960, 1962, 1970; Paparo, 1972, 1973).

The constant level chamber for direct measurement of pumping rate was devised by Galtsoff (1926), to ensure that separation of the exhalant water current from the bivalve was not interfered with by pressure differences produced by the process of separation. The apparatus has been used in various forms by Galtsoff (1926, 1928, 1946), Nelson (1935, 1936), Collier & Ray (1948), Loosanoff & Engle (1947), Loosanoff & Nomejko (1946) and more recently by Drinnan (1964) and Davids (1964).