Studies of Marine Planktonic Diatoms: I. Cyclotella Nana Hustedt, and Detonula Confervacea (Cleve) Gran.

Abstract

Bacteria-free clo~les of the small centric diatom Cyclotella 71ana Hustedt were isolated, three from estuarine localities, one from Continental Shelf waters, and one from the Sargasso Sea. Detonzrla confervacea was isolated from Narragansett Bay. WIorphology of all clones was studiedwith the light andelectron microscopes. Morphological differences between clones of C. nawa do not at present warrant separating any as distinct species.Clones of C. nalza require only vitamin B I~; D. co,zJervacea has no vitamin req~~irement.Growth of the estuarine clones of C. nana was unaffected by salinity down to 0.5yoO and increased with temperature to 2S0 C. The Shelf clone grew more rapidly a t salinities above 8yoO and at temperatures between 10" and 20" C. The Sirgasso Sea clone did not survive below 15" C or 17 .5yoO, while D. colzjervacea did not survive a t temperatures above 15" or a t sdinities below 8%0. 'The physiological differences between clones correspond roughly to the conditions obtaining in nature where each was collected.'Manuscript bloon~s. T h e quantity and species composition of the phytoplankton has an important bearing on the usefulness of the bays for shellfish production and for recreation. T h e ecology of blooms of green algae (recorded since 1922) was discussed by Ryther (19) ; such algae dominated the waters of the bays during bloom periods until 1953. In 1957, however, the bloo~ns in a tributary of NIoriches Bay consisted chiefly of centric diatoms-Ckaetoceros simplex, Tlzadassiosira nana, and Skeletonenza costatz~m (20). Also present, though in smaller nunlbers, were Cyclotella caspia, a Cyclotella species resembling C. rneneghiniana (see ref. 12), and C. nana. ('These three species were determinecl by light and electron lnicroscopc exa~llinatio~l of frustules from preserved material.) C. nana became the chief component of blooms in both bays during the summer of 1958; samples a t 23 stations in late summer had from 10.' t o 2 XlO~cells/rnl. By micl-winter the species was scarce in the plankton, b u t it reappeared in the summer of 1959, though in smaller numbers than in 1958 (unpublished data). D. confervacea has been present in the phytop1anl;ton of these bays only in winter, as it is in Narragansett Bay (15). Physiological stuclies with cultures of D. confervacea and estuarine clones of C. nana were made t o compare with the field observations. Materials and Methods ilforphology and TaxonomyLiving and preservcd cells were observecl with the light ~nicroscope (including phase contrast) a t magnifications up to 1875 diameters. Cultures a n d preserved plankton samples were concentrated b y sedimentation, treated with hot or cold 50y0 nitric acid or hydrogen peroxide, and ~vaslied by sedimentation or centrifugation. Frustules were mounted in Hyrax for light microscopy ancl settled onto formvar films over grids for electron microscopy.

Effect of TDA‐producing Phaeobacter inhibens on the fish pathogen Vibrio anguillarum in non‐axenic algae and copepod systems

“…A R. salina K‐1487 stock culture was maintained in f/2 medium (Guillard and Ryther, 1962; Guillard, 1975) without Na 2 SiO 3 but with 5 mM NH 4 Cl in 3% IO (Instant Ocean salts, Aquarium Systems Inc.) (f/2‐Si+NH 4 ) at 18°C and 24 μmol photons m −2  s −1 , photosynthetically active radiation (PAR). The algal density was determined by counting in a Neubauer‐improved counting chamber, and the culture was adjusted to approx.…”

Re-classification of Pheopolykrikos hartmannii as Polykrikos (Dinophyceae) based partly on the ultrastructure of complex extrusomes

“…Cells were visualized through a dissecting microscope and individually picked using a mouthpipette. After three washing steps, specimens were placed in 15 psu f/2-medium (Guillard and Ryther 1962) charged with 5% soil extract and grown at medium light conditions (cool-white fluorescent lamps, $100 mmol photons * m À2 * s À1 ) at 17 1C (at UBC) or 20 1C (in MD).…”

Limits to productivity of the algaPleurochrysis carterae(Haptophyta) grown in outdoor raceway ponds

“…Cultures were maintained in modified f/2 medium (Guillard and Ryther, 1962) as outlined in Moheimani and Borowitzka (2006). The culture medium for the ponds was chemically sterilized by adding 1 mL 12.5% sodium hypochlorite to 20 L seawater.…”