Melosira Nummuloides Research Articles

A Possible Relationship BetweenEnteromorpha(Chlorophyta) andMelosira nummuloides(Chrysophyta: Bacillariales)

Abstract While investigating the effect of fluoride on the green alga, Enteromorpha, healthy chains of the centric diatom, Melosira nummuloides appeared in cultures containing a small piece of Enteromorpha, nutrient medium and all concentrations of fluoride, as Na2SiF6 to 160 p.p.m. Both the Melosira alone and the Enteromorpha, accompanied by Melosira, were transferred into a culture medium (germ intercepting filtrate, S=30g./kg. to which 0.4 ml./1. of the plant nutrient ‘Kerigrow’ was added) with a normal fluoride content; after three weeks the Melosira alone was present only in short, broken chains, whereas that in the presence of Enteromorpha had formed long, healthy chains.

Heterotrophic nutrition inMelosira nummuloides, a possible role in affecting distribution in the Clyde Estuary

The benthic centric diatom Melosira nummuloides dominated sites of heavy pollution on the Clyde Estuary, occurring in conditions conducive to heterotrophic growth—positive correlation with BOD and suspended solids and negative correlation against light penetration of the water. A clone (Renf-1) of the organism, isolated from a polluted site and rendered axenic grew in culture through a range of light intensities, with compensating light below 150 lx. Some initial growth occurred in the dark on medium enriched with site water. Growth was best at a salinity of 10‰. for samples adapted to 4, 10 and 12‰.. Addition of certain amino acids to the medium caused significant enhancement of growth, due to leucine, arginine and serine at 0 klx, leucine, arginine and glutamic acid at 0·1 klx and glutamic acid at 3·3 klx. Eight amino acids were accumulated by carrier mediated methods in the dark. Kinetics for arginine uptake were best (low K m) in the dark and at a salinity of 10‰, with a corresponding greater growth e...

Grazing Effects of Four Marine Intertidal Herbivores on the Microflora

The impact of 4 species of intertidal gastropods (3 limpets and 1 periwinkle) on microalgal species composition and biomass has been evaluated and the degree of overlap of grazer diets has been examined. A series of clay pipes set in a mud flat became artificial substrates for diatom assemblages; grazers were added to the outside of these pipes after an initial period during which the flora developed. The mud proved to be an effective barrier to both immigration and emigration. All 4 gastropods selectively removed 3 diatom species from the pipes: Melosira moniliformis, Melosira nummuloides, and Fragilaria striatula var. californica. These species consist of long chains of moderate—sized cells that form an overstory within the diatom mat; a total of 130 additional species may be found within the diatom community. Selective removal may be facilitated by the chain morphology, by the location of these diatoms in the outermost portion of the mat, and by loose adhesion of these species to the rock surface. Diatoms with potentially tighter adhesion such as the stalked Achnanthes spp. are less affected by grazers. The abundance of 3 species of blue—green algae was little changed by grazing. All 4 grazers had remarkably similar diets, apparently using the same resource in about the same way. Data on the amount of chlorophyll a per m2 on natural rock surface indicate that grazers greatly reduced microalgal standing crops. Differences in grazer zonation and use of macroalgae, coupled with increased food availability during reproductive seasons (winter and spring), allow continued coexistence of these very similar herbivores.

The taxonomy and classification of the diatom genusMelosiraC.Ag. I. The type speciesM. nummuloidesC.Ag.

Examination of specimens from the herbarium of C. A. Agardh at Lund in Sweden has resulted in the choice of a lectotype for Melosira nummuloides C.Ag., the type species of the genus. A specimen has been placed in the diatom collection at the British Museum (Natural History). The structure of the frustule of fresh and cultured material has been examined in detail and a revised description of the species is presented in anticipation of a wider study of the genus. The type of valve structure is discussed and the function of some of the siliceous structures is also considered.

A NUTRITIONAL ANALYSIS OF A SUBLITTORAL DIATOM ASSEMBLAGE EPIPHYTIC ONENTEROMORPHAFROM A LONG ISLAND SALT MARSH1,2

SUMMARYThe diatom population structure of a salt marsh epiphytic community growing onEnteromorpha intestinaliswas studied at one station throughout the summer. A total of 218 species or varieties were recognized. Six species— Fragilaria construens, Cocconeis scutellum, Cocconeis placentula, Achnanthes hauckianavarieties,Achnanthes pinnata, andAmphora coffeaeformis(var.acutiuscula)–dominated theEnteromorphaepiphytic community during the summer months and comprised ∼ 40% of the total populations.Melosira nummuloides, Opephora martyi, Synedra fasiculatavar.tabulata, S. affinis, Navicula platyventris, andN. pavillardiwere also very common species (13% of the total population). The distribution of many species in the community was seasonal. A series of differential media have been developed which are effective as tools for the isolation and nutritional characterization of the algae and bacteria from the community. Many diatom species can be recognized by their colony type or growth pattern on solidified media. A key and illustrated plates aid in identification. Changes in population structure of the community were reflected by changes in the nutritional patterns as judged by differences in the growth of diatoms and bacteria on the differential media tested. The nutritional requirements, selectivity, and rank order of media for individual species is given.Almost half of the colony types (32–33) grew on either unenriched seawater from the collection site or basal synthetic seawater. Erdschreiber was a poorer medium for the isolation of algae than seawater alone. Few algal colonies grew on either marine nutrient agar or trypticase soy agar. Nitrite inhibited algal growth. Media enriched with thiamine, biotin, or nitrate, phosphate, and B12were stimulatory. Soil extract or an acetone extract ofEnteromorphatripled growth; a complex vitamin mixture, or glycerol, or mannitol, or an autoclaved extract ofEnteromorphadoubled colony numbers. The greatest numbers of diatom types (43) and total colonies (655) were recovered on media enriched with acetone extract ofEnteromorpha, suggesting a possible nutritional relationship betweenEnteromorphaand its epiphytes.The representativeness of the isolations from the natural community as a function of time was also considered. Concentrations of selected dissolved potential growth‐stimulating nutrients were measured within and external toEnteromorphacommunities. We conclude that the algal assemblage growing epiphytically onEnteromorpha intestinalishas a diverse auxotrophic profile which contributes to the productivity and stability within this important component of the epiphytic community and that much of the organic substrates used by individual species originate within and are recycled among the community members.

The organic component of the cell wall of the marine diatomMelosira nummuloides(Dillw.) C. Ag

Organic material which may be several layers thick has been found beneath the siliceous cell wall of the marine centric diatom Melosira nummuloides (Dillw.) C. Ag. This supports the findings of Liebisch (1928, 1929). The organic component, thought to be polysaccharide, is deposited outside the plasmalemma after the siliceous component has been laid down. It exists as two distinct entities, one associated with each valve.

LABORATORY STUDIES OF ASSEMBLAGES OF ATTACHED ESTUARINE DIATOMS1

Effects of light intensity, exposure to desiccation, salinity, and heated water on the vertical distribution and growth of populations of attached estuarine diatoms were studied in a laboratory model ecosystem. Of the 35 most abundant diatom taxa found in 36 samples from the laboratory system, all but 8 were also abundant in samples obtained from Yaquina Bay and estuary. Vertical distribution of diatoms was more closely related to light intensity and period of exposure to desiccation in the summer experiments than in the winter experiments. A sudden, unseasonable decrease in salinity or increase in water temperature had a much greater effect on diatom assemblages exposed to 12,270 lux than on those that developed at either 1,030 or 4,710 lux; the most noticeable changes in community structure included a decrease in species diversity and a rapid growth of a population of Melosira nummuloides, a filamentous species. Primary productivity in diatom assemblages exposed to periods of desiccation was less under winter conditions than under corresponding conditions in summer. Primary productivity in assemblages not exposed to desiccation was strongly affected by light intensity during both summer and winter experiments, and the ratio primary productivity: chlorophyll a was greater during winter than summer.

UPTAKE SPECIFICITY FOR ORGANIC SUBSTRATES BY THE MARINE DIATOM MELOSIRA NUMMULOIDES(1).

Melosira nummuloides, clone Mel-3, shows a very high specificity with regard to its ability to take up organic substrates. Amino acids supplied in the medium at 1 X 10(-4) M are taken up at initial rates of the same order of magnitude as that of photoassirnilation of COj. However, sugars, sugar alcohols, or organic acids supplied at the same concentration are not taken up. The mechanism for uptake of amino acids appears to require energy, since tlie uptake of the amino acid analog α-aminoisobutyric acid is strongly inhibited by 2 f-dinitrophenul. The uptake mechanism does not appear to be inducible. The ability of M. numinuloides to utilize amino acids as a nitrogen source is quite restricted. Arginine, ghttamine, asparagine, proline, and glutamic acid were good nitrogen sources. Seventeen other amino acids, including α-aminoisobutyric acid, were unsatisfactory for growth, although they were rapidly taken up from the medium.

<i>Melosira nummuloides</i> (DILLW.) C. A. AGARDH の無菌培養について

In an experiment to obtain bacteria-free culture of the marine diatoms, a diatom species, Melosira nummuloides was treated with antibiotics. As C. P. SPENCER (1952) states, a short exposure to the considerable doses of Penicillin and Streptomycin seems to be very effective for this purpose. Bacteria-free culture has continued. Its sterility and normal living of that diatom in such a bacteria-free circumstance were ascertained.