AbstractSome phytoplankton are able to use various forms of dissolved organic nitrogen without initial transport into the cell. Instead, these phytoplankton utilize cell-surface enzymes to degrade these forms of nitrogen to NH4+ and several byproducts. Only the NH4+ is then taken up. In the case of the cell-surface amino acid or amine oxidases, the by-products are hydrogen peroxide and an α-keto acid or aldehyde, respectively. The characteristics of these enzymes are discussed along with their possible importance in marine environments.
The reproductive and population biology of the deep-sea elasipodid holothurian families Psychropotidae and Deimatidae from the North Atlantic is described. In the psychropotid species the ovary is a large thick-walled nodular structure containing oocytes with an interspecific maximum size of 1.2 mm to 3 mm. In the deimatid species the ovaries consist of thin-walled elongate tubules containing oocytes up to a maximum diameter of 900 μm. In the psychropotids all the oocytes undergo vitellogenesis whereas in the deimatids some could act as nurse cells for those oocytes continuing to grow. Fecundity is low in both families. The soluble lipid content of the ovary in all species is high when compared to other tissues. The calorific content of the whole ovary varies from 25.46 to 28.08 Jmg−1 AFDW. There is no evidence for any reproductive periodicity in any of the species examined.In the psychropotids the testes are well-developed structures packed with spermatozoa except in those specimens that are infe...
Engineering considerations for selecting components for sampling zooplankton with pumps involve interactions of required capacity, hose size, hose length, hose friction, pump type, pump motor power, and overall system configuration. Systems can be classed as hose-on-suction-side (pump on deck) and hose-on-output-side (submersible pump). Each class has distinct advantages and drawbacks. High capacity systems of each class have been developed by us. A suction-side system produces 800 liters min−1 for depths to 85 m with a diesel-driven centrifugal pump and 10.2 cm ID, suction hose. An output-side system produces from 1,380 liters min−1 at the sea surface to 803 liters min−1 at 90 m with a modified sewage sump pump and 10.2 cm ID, collapsible, discharge hose.
Large spatial and temporal differences in both trace metal concentrations and chemical speciation in the sea have led to wide variations in biological availability of metals and their effects on phytoplankton. Trace metals are usually taken up by algae via the formation of coordination complexes with specialized transport ligands in their outer membranes, and metal uptake is determined by the interplay between redox, complexation, or oxide dissolution reactions of metals in seawater and ligand-exchange reactions at these sites. Some metals, such as copper and zinc, are heavily chelated by organic ligands in seawater, and their biological availability is determined by the concentrations of free metal ions or of kinetically labile inorganic species (free ions plus inorganic complexes). Once inside cells, trace metals influence metabolism primarily as a consequence of the role of many of these metals (Fe, Mn, Zn, Cu, Co, Mo, Ni) as essential cofactors in metalloenzymes. Trace metals may also inhibit ...
An examination of the knowledge about sampling Loligo opalescens populations leads to two general conclusions regarding the assessment of their abundance. First, it is suggested that studies concentrate on spawning ground organisms, since they aggregate during spawning, are commercially fished at this time, and their numbers can be assessed using a combination of data from market catch, adult and egg case densities, acoustic sensing, and perhaps larval densities. Second, it is suggested that large-scale acoustic surveys coupled with large midwater trawling activities be used to qualitatively assess adult organisms off the spawning grounds.
The carotenoid composition of Chrysochromulina sp. clone NEPCC 186 (herdlensis) was examined, and 19′—hexanoyloxyfucoxanthin was found to be the major carotenoid. The quantitative carotenoid composition resembles that of the recently examined Chrysochromulina polylepis. Both Chrysochromulina spp. belong to the second pigment type of the Prymnesiophyceae, producing 19′—acyloxyfucoxanthins and fucoxanthin as well as acetylenic carotenoids, now numbering about 6 species.
The oceans are the largest natural source of organic sulfur compounds, primarily dimethyl sulfide (DMS), a potentially important factor in the global climate. Significant production of dimethylsulfoniopropionate (DMSP), the precursor of DMS, is confined to a few classes of phytoplankton, primarily the Dinophyceae (dinoflagellates) and Prymnesiophyceae (which includes coccolithophores). Because of this taxonomic relationship and the spatial and temporal heterogenity of these forms of algae, DMS emissions will vary according to their presence. Current values of DMS production may be considerably underestimated due to sampling inadequacies and a lack of information about biological parameters that affected rate of production.
AbstractTwenty-four repeated samples were collected using an RMT (1+8) M sampler from a depth of 1,000m in the vicinity of 42°N, 17°W in May 1978, most within a single 36h period. Data for 194 species belonging to eight micronektonic and planktonic groups were analyzed. Variability in standing crops of both micronekton and plankton and the numerical abundance of individual species showed that single sample estimates at such depths are within a factor of two or three of the mean estimates from repeated samples. Only one species, a myctophid fish Notoscopelus elongatus kroyeri, showed the cyclic changes in abundance that would be expected from diel vertical migration. Discussed is the possible significance of this lack of diel vertical migration at depths below 1,000m, as compared to plankton biomass and the high relative abundance of micronekton, to our understanding of the fluxes of organic matter to deep-living population.
The identifiable phytoplankton species between New Zealand and Hawaii can be divided into the fraction that grows readily under improved conditions, composed of diatom species plus Coccolithus huxleyi and Gephyrocapsa oceanica, and the complementary fraction of other species that do not so grow. Samples containing a higher proportion of the first fraction of cells have a higher growth capacity. The phytoplankton between New Zealand and Hawaii having varying proportions of the two fractions has a varying growth capacity. The phytoplankton is the single entity that is controlled both by its own variable growth capacity and a variable oceanic nutrient concentration between New Zealand and Hawaii. The phytoplankton is a single but scattered, concrete object; growth capacity is a single, abstract entity. The two together do not control nutrient concentrations since they are powerless to prevent large, excess amounts of nutrient about the equator. Instead, then, growth capacity and nutrient concentratio...
Lampanyctus alatus is an abundant myctophid in subtropical waters of the eastern Gulf of Mexico. The population has been estimated at 85–140 × 103 fish per km2 of sea surface, with most of the population biomass (>60%) in individuals larger than 35 mm. This species concentrates in the 80175 m zone at night and at 550–750 m during the day. The diet is essentially crustacean (>98%), with over 60 prey species having been identified. Seventy-three percent of the number and 44% of the biomass of the diet are copepods. Euphausiids rank first in biomass and are particularly important in the diet of larger fishes. Lampanyctus alatus is selective for prey >1 mm and for the copepod genus Pleuromamma.A diel feeding cycle is apparent, stomachs being fullest in the period 0100–0500 h. Daily ration is estimated at 2–4% of body weight and decreases proportionately with increasing fish size. It is estimated that one-fifth of respiration and less than one-tenth of the daily ration is utilized in diel vertical migr...
This is a study of larval abundance and distributional pattern of the winter population of the Japanese common squid, Todarodes pacificus Steenstrup, based on plankton net collections made by the R/V Soyo-Maru during January to March (1959–1976) in the seas extending from the south of Kyushu to the Pacific coast of central and eastern Honshu. The larval abundance index (LI) was compared with CPUE (catch per boat day), an index of recruitment of adult stock size.The main spawning ground of this population is located to the southwest of Kyushu. The larvae (rhynchoteuthion) grow while they are advected by the Kuroshio Current to the northeast. Hence early larvae are more abundant in the west, while advanced larvae are more abundant in the east. Mortality seems to be highest for stages up to several millimeters DML than for later stages.The stock size of the Pacific winter population has fluctuated greatly. It declined since the peak 1960 year class to very low levels. The decrease of the stock size t...
