New development in the MOCNESS,an apparatus for sampling zooplankton and micronekton

Four variants of the Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) have been constructed to sample a broad size spectrum of oceanic animals from microzooplankton to micronekton. The systems differ in mouth opening dimensions (ranging from 1/4 to 20 m²), the number of nets carried (from 5 to 20), and the mesh size of the netting (from 64 m to 3.0 mm). A new electronics package enables an operator to send commands down a single conductor, armored cable to open/close the nets and provides 12-bit resolution for the environmental (temperature, depth, conductivity) and net operation data (flow, net-frame angle, net-bar release), which are transmitted up the cable to the deck unit at 2-s intervals. A microcomputer system, interfaced to the deck unit, calculates salinity, volume filtered by a net, net trajectory velocity, and vertical velocity. The data are printed out and stored on disc, and profiles of temperature and salinity versus depth are plotted during the course of the tow. Analysis of the relationship between the geometry of the MOCNESS under tow and the past and present methods used to estimate the water filtered by a net revealed that significant bias is introduced when the ascent or descent angle of a net is disregarded. The bias is a function of the ratio of vertical velocity to net trajectory velocity and results in an underestimate of volume filtered while shooting a net and an overestimate while hauling.     

Glycolate metabolism by Pseudomonas sp., strain S227, isolated from a coastal marine sediment

Glycolate excreted by phytoplankton is a potentially important nutrient for bacteria in coastal and estuarine environments. The metabolism of glycolate by Pseudomonas sp., strain S227, originally isolated from the New York Bight Apex, has been studied. The specific growth rate for this strain on glycolate is 0.156 doublings h^-1. The apparent V_max and K_m for glycolate uptake are 83.6 nmol min^-1 mg cell protein^-1 and 7.4x10^-8 M, respectively. The preferential respiration of the carboxyl carbon (C-1) and the incroporation of the hydroxymethyl carbon (C-2) suggest that the glycerate pathway is used for growth on glycolate. Alternatively, another pathway can be utilized which results in the complete catabolism of glycolate. Glycolate and lactate metabolism are also closely linked either by a common metabolic pathway or a common transport system other than the monocarboxylate transport system. The magnesium ion concentration is also important in glycolate metabolism. The characteristics of glycolate metabolism observed in Pseudomonas sp., strain S227, are advantageous in coastal and estuarine environments where glycolate production is intermittent, and the concentrations are low.     

Ultrastructural alterations on chloride cells of the yellowtail Seriola quinqueradiata,following exposure to the red tide species Chattonella antiqua

By means of scanning and transmission electron microscopy, the influence of the red tide species Chattonella antiqua was examined with respect to the surface ultrastructures of chloride cells of the yellowtail Seriola quinqueradiata. Conspicuous ultrastructural alterations occurred on the apical surface of these cells. The majority of chloride cells in the control gills showed an apical surface with numerous cellular extensions, while more than half the chloride cells affected by red tide organisms exhibited an apical surface with fewer and smaller extensions, a wrinkled apical surface, or a protruded apical surface. These ultrastructural alterations of chloride cell surface may be due to the partial disturbance of salinity by C. antiqua, and reflect the changes of the ion-transport function in yellowtail gills exposed to red tide water.     

Prodigiosin metabolites of a marine Pseudomonas species

The major pigment of a marine micro-organism was identified as prodigiosin on the basis of analytical and spectral data. Two minor pigments were tentatively assigned structures, from thin-layer chromatography (TLC) and mass spectral data, as prodigiosin homologs with 3-n-hexyl and 3-n-heptyl side-chains. The micro-organism was classified as a new Pseudomonas species on the basis of its morphological and biochemical characteristics. It was named Pseudomonas magnesiorubra (ATCC No. 21856).     

Effect of zinc on the settlement of the oyster Crassostrea gigas

The influence of zinc upon the pattern and success of settlement was examined in the oyster Crassostrea gigas. Late larvae were more tolerant of zinc than embryos. A delay in settlement was recorded in treatments containing zinc as low as 125 μg/l, and numbers of larvae settling was reduced in the presence of zinc. Larvae subjected to zinc immediately prior to settlement showed evidence of slowing in behavioural development. Those larvae which settled in the presence of zinc, however, when ongrown in clean water were as viable as controls. Zinc at concentrations of 250 and 500 μg/l suppressed spat growth, but recovery was rapid upon subsequent on-growing in clean water conditions.     

Some factors affecting the colonization of a dredged channel

Standing crop, population size, and species diversity of the macrobenthic organisms in an estuarine channel were studied before and after dredging. A new suction-corer which sampled an area 0.1 m² to a depth of 30 cm was used in order to insure the inclusion of large, deep-dwelling animals. Eleven months after dredging, biomass and number of species and specimens had not recovered to pre-dredging levels. Colonization began with relatively large, swiftly moving forms such as the errant polychaete Nereis succinea and the crab Neopanope texana sayi. Stations in silt and mud regions recovered more slowly than those in sandier sediments. Most of the dominant and subdominant species had not recovered 11 months after dredging, and the previously abundant polychaetes Notomastus latericeus and Clymenella torquata had virtually disappeared. Only relatively uncommon lamellibranchs such as Tellina agilis, Lyonsia hyalina and Mulinia lateralis increased after dredging. Distribution of sediment types changed as the result of modified tidal velocities in the channel. Mud and silt were removed by the dredge, exposing the sand underneath, and sandy stations became muddier as the result of lowered current velocities. Marked changes in species composition reflected this change in sediment character. Eleven months after dredging no evidence of succession was found, but colonization had begun. Values of all three parameters studied were reduced to small fractions of pre-dredging levels, although species diversity in sandy sediments exceeded pre-dredging levels.     

Studies on reef corals. III. Fine structural changes of calicoblast cells in Pocillopora damicornis during settling and calcification

The site of reef-coral calcification has been studied in the branching coral Pocillopora damicornis Lamarck. Electron microscopy and X-ray microprobe analysis were performed on the calicoblast epidermis of newly settled larval stages and of adult coral. During settling, the heterogeneous columnar cell composition of the planktonic larva epidermis is replaced by a simple epithelium consisting of a single cell type, the calicoblast cell. Metamorphosis appears tightly linked to settling, with cell changes occurring within hours after attachment, and is marked by the appearance of a new secretory cell. The calicoblast cell of the adult coral is extremely flattened, and interdigitates extensively with adjacent calicoblast cells. This cell possesses a featureless plasma membrane lacking microvilli or flagella. It characteristically contains large membrane-bound vesicles with homogeneously fine granular contents. Preliminary microprobe analysis indicated a higher calcium content in these vesicles than in surrounding tissue; however, not in concentrations suggesting calcium-carbonate precipitation. They may represent sites of organic matrix synthesis. The calicoblast epidermis is separated from the underlying coral skeleton by a narrow gap. This gap appeared devoid of substructure, either organic or inorganic. The coral soft tissues are attached to the skeleton by mesogleal attachment processes, the desmoidal processes. These consist of a complex fibrous network originating in the mesoglea, and inserting onto the skeleton via specialized attachment regions consisting of electron-opaque membranous plaques. Skeletogenesis in reef-corals probably occurs extra-cellularly, external to the calicoblast epidermis, by simple overgrowth of the skeleton.     

Uptake and assimilation of 15NH 4 + by a variety of corals

Corals from the Swain Reefs of the Great Barrier Reef were exposed to ¹⁵NH ₄ ⁺ in sea water, and the disappearance of NH ₄ ⁺ from the medium and the appearance of ¹⁵N in the corals was followed. Disappearance of NH ₄ ⁺ usually followed a reasonably smooth curve with rate of disappearance decreasing as the concentration of NH ₄ ⁺ decreased; the decrease in rate was not the result of damage to the corals. The rate of uptake of ¹⁵NH ₄ ⁺ vs concentration did not describe a normal substrate saturation curve, as uptake may have been diffusion limited. ¹⁵N was assimilated into the corals in the form of stable organic nitrogenous compounds. Its assimilation usually exhibited an initial lag. An ahermatypic coral did not remove NH ₄ ⁺ from the medium. Differences in NH ₄ ⁺ uptake with a 1-h cycle of light and dark were minor. Isolated zooxanthellae assimilated ¹⁵NH ₄ ⁺ as indicated by accumulation of ¹⁵N with no lag.     

Density and distribution patterns of the temperate marine fish Cheilodactylus spectabilis (Cheilodactylidae) in a reef environment

Cheilodactylus spectabilis (Hutton) is common over shallow reefs in north-eastern New Zealand. Replicated transect between-area differences in density and in size frequency. C. spectabilis is not nocturnally active. The between-area differences in density and size frequency remained constant over daylight hours, demonstrating that C. spectabilis does not undergo any systematic feeding migrations. Topographic complexity was shown to have a significant positive influence on fish density. Mean size was related to water depth at 5 localities investigated, with small (<200 mm standard length, SL) individuals being restricted to shallow water. All sizes of C. spectabilis examined had fed on small invertebrates, with gammarid amphipods predominating. No evidence of size-related differentiation in feeding patterns was observed, although small individuals spent significantly more time feeding than large ones. Small (<200 mm SL) individuals occupied feeding areas and shelter sites from which they excluded other small C. spectabilis. Large individuals showed no site-associated aggression, covered a greater area during daily movements and overlapped with other large and small C. spectabilis while feeding. No evidence of dawn or dusk peaks of feeding activity or movement was collected.