Maureen D. Keller

MEDIA FOR THE CULTURE OF OCEANIC ULTRAPHYTOPLANKTON

A medium (K) developed for culturing fastidious oceanic phytoplankton has been tested using recently isolated ultraphytoplankton clones representing at least seven different algal classes. The medium was designed to satisfy as completely as possible the nutritional requirements of this diverse group of phytoplankters. Important aspects are the addition of selenium, the inclusion of both nitrate and ammonium, an increased level of chelation and a moderate level of pH buffering. The seawater‐based version of this medium has been tested on 200 clones of which 186 grew reliably. A synthetic counterpart (AK) was tested on 40 of the more difficult clones and 27 grew well; 13 grew not all. While neither medium meets the exacting nutritional needs of all the ultraphytoplankton forms tested, they are excellent for most oceanic clones and are very successful for the isolation and establishment in culture of new oceanic phytoplankton clones.

A comparison of HPLC pigment signatures and electron microscopic observations for oligotrophic waters of the North Atlantic and Pacific Oceans

Abstract The use of HPLC pigment analysis has become a primary tool for investigating the taxonomic composition of natural phytoplankton populations. In this study, we compare, for the first time, the taxonomic composition based upon HPLC pigment signatures with direct electron microscopic taxonomic identifications from two sets of open ocean oligotrophic field samples. Electron microscopic observations at sites in the Atlantic and Pacific Oceans (Hydrostation S and Station ALOHA, respectively) agree with taxonomic partitioning based upon HPLC algorithms in the, upper water-column samples, but there is increasing disagreement between the two methods in deeper water samples. This disparity probably results from depth-dependent changes in cellular pigment content and accessory pigment-to-chlorophyll ratios. At both locations, the eukaryotic ultraplankton was similar in taxonomic composition, at least at the class level, and the Prymnesiophyceae and the newly described Pelagophyceae were the two most abundant groups of eukaryotes.

Dimethylsulfide in a large-scale coccolithophore bloom in the Gulf of Maine

Abstract Blooms of the coccolithophore, Emiliania huxleyi , are common phenomena in the Gulf of Maine in early summer, as revealed by AVHRR imagery. It is known from laboratory cultures and some field studies that the production of the important volatile sulfur compound, DMS, and its precursor, DMSP, are confined largely to a few classes of phytoplankton, specifically the Dinophyceae and the Prymnesiophyceae, which includes the coccolithophores. In the Gulf of Maine, concentrations of DMS and DMSP were as much as an order of magnitude higher within a E. huxleyi bloom than at stations outside the bloom area, including stations with high phytoplankton biomass of other taxa. Values of both DMS and DMSP were highest in the mixed layer, with depth maxima associated with the chlorophyll maxima, generally at 10–15 m. In addition, higher levels of DMS and dissolved DMSP were associated with older parts of the bloom, as determined by numbers of loose coccoliths. This is the first example in nature where DMS production is related, not only to a given species of algae, but also to the stage of the bloom.

Microwave treatment for sterilization of phytoplankton culture media

Abstract A standard microwave oven for the sterilization of phytoplankton culture media and apparatus was tested. Elimination of bacterial, algal, and fungal contaminants is achieved in

The effects of light quality and intensity on photosynthesis and growth of marine eukaryotic and prokaryotic phytoplankton clones

Abstract The aim of this work was to assess the relative efficiency of different phytoplankton groups growing under various spectral light fields commonly found in the marine environment. Using neritic and oceanic clones of cyanobacteria (prokaryotic) of the genus Synechococcus and various sized eukaryotic algae representing diverse pigment groups, we compared absorption and fluorescence excitation/emission spectra. Colored filters and neutral density screens were used to simulate oceanic and coastal water-types and rates of photosynthesis and growth were measured under variable conditions of light intensity and quality. Relative photosynthetic efficiencies were determined by comparing light-limited slopes of photosynthesis-irradiance curves in green, blue, and blue-violet light with those in white light. The relative quantum efficiency for photosynthesis was related to both size and pigment composition of the phytoplankter. Independent of light color, smaller algal species were photosynthetically more efficient than larger algae from the same pigment group. In general, the ratio of in vivo cholorophyll intensity fluorescence at the red emission maximum induced by 530 nm excitation to that produced by 470 nm excitation was better than absorption spectra in predicting the ability of organisms from different pigment groups in using various light qualities. Within the ultraplankton size range, algae photosynthesized and grew most efficiently in low intensity blue-violet and blue light, while phycoerythrin-rich Synechococcus clones were most efficient in dim green light. Even though some ultraplankton algal clones, such as the diatom 13−1 and the cryptomonad ID2, contained large quantities of fucoxanthin and phycoerythrin, respectively, their photosynthetic and growth efficiencies in green light were much lower than those of phycoerythrin-rich Synechococcus clones. Moreover, the presence of phycourobilin chromophores in the phycoerythrin of some Synechococcus clones, apparently increased the ability of these cyanobacteria to photosynthesize in low intensity blue light. We conclude that Synechococcus clones containing phycourobilin chromophores could out-compete other Synechococcus clones at depth. However, oceanic ultraplanktonic algae may have a competitive advantage over larger algae and Synechococcus spp. at the base of the photic zone, because these small algae would be more efficient in using the available dim blue-violet light.

Coccoid eukaryotic marine ultraplankters with four different HPLC pigment signatures

Pigment compositions of 16 coccoid eukaryotic ultraplanktonic clones isolated from coastal and oceanic waters were investigated by high‐performance liquid chromatography (HPLC). Four distinct pigment signatures were observed, and clones were classified into subgroups based on the presence or absence and relative abundances of selected chlorphylls and carotenoids. The first subgroup (5 clones) was pigmented like chlorophyll b‐containing higher plants and resembled true chlorophycean algae. The second subgroup (3 clones) contained chlorophyll b and relatively high levels of prasinoxanthin, a carotenoid characteristic of certain members of the Prasinophyceae (sometimes grouped as the Micromonadophyceae). The third subgroup (5 clones) was pigmented in a similar fashion but had a twofold lower prasinoxanthin‐to‐chlorophyll a ratio and an unidentified carotenoid. The fourth subgroup (3 clones) lacked chlorophyll b and was pigmented like certain members of the Chrysophyceae (e. g. 19′‐butanoyloxyfucoxanthin‐containing Pelagococcus subviridis Norris) Online diode array spectral analysis of selected clonal extracts revealed the presence of Mg 2,4‐divinylphaeoporphyrin a5 monomethyl ester‐like and chlorophyll c‐like pigments in representatives of the prasinophyte‐like and chrysophyte like clones, respectively. These findings plus the occurrence of chlorophyll b, prasinoxanthin and 19′‐butanoyloxyfucoxanthin in the North Atlantic Ocean suggest that chrysophyte‐ and prasinophyte‐like organisms can be important biomass components of marine phytoplankton.

Blooms of the coccolithophore Emiliania huxleyi with respect to hydrography in the Gulf of Maine

Abstract We present results of oceanographic surveys of visually turbid blooms of the coccolithophore Emiliania huxleyi in the Gulf of Maine during the summers of 1988, 1989 and 1990. In each year, hydrographic stations within the blooms could be distinguished from non-bloom stations on a temperature-salinity diagram. In 1988 and 1989 the blooms were confined to the surface waters of the central western Gulf of Maine; T-S analyses showed they occurred in higher salinity surface waters at stations characterized by a well-defined upper mixed layer overriding a sharp pycnocline. Nutrients (not measured in 1988) were near depletion in the surface waters of both bloom and non-bloom stations in 1989, with surface phosphate being lower in the bloom waters (0.02–0.16 μM in the top 15 m) than in non-bloom waters (0.21–0.49 μM). Phosphate was not as low in the surface waters of the 1990 bloom. The bloom that year was much smaller in areal extent than in 1988 or 1989, and was limited to the northern part of the Great South Channel and western Georges Bank area of the Gulf of Maine. T-S analyses indicated significant mixing of different water masses in the area of the bloom in 1990, with the bloom being confined to those stations having less dense surface waters, of lower salinity, than the non-bloom stations. There also was evidence of a subsurface salinity minimum beneath the bloom waters in 1990. Blooms of E. huxleyi with surface expressions of visually turbid waters do not occur every year in the Gulf of Maine, and we discuss possible causative factors, specifically as related to the age or maturity of surface waters and macro- and micro-nutrient levels, that could facilitate bloom formation and which could vary between years.

Seasonal variations in the production and consumption of amino acids by coastal microplankton

Abstract A seasonal study on coastal microplankton was conducted in surface waters near Boothbay Harbor, Maine. Phytoplankton biomass, particulate production and extracellular organic release were examined in conjunction with microheterotrophic biomass and the uptake and respiration of amino acids. In situ dissolved free amino acid (DFAA) concentrations were also determined. Several phytoplankton blooms occurred throughout the year, in mid-summer, late autumn and in mid-winter. Heterotrophic activity and biomass paralleled phytoplankton extracellular release more closely than either phytoplankton particulate production or biomass. DFAA concentrations were not wholly dependent on extracellular release. Heterotrophic uptake did not appear to be dependent on DFAA concentrations but rather on rates of production of DOC by phytoplankton.

WIDESPREAD OCCURRENCE OF THE OCEANIC ULTRAPLANKTER, PRASINOCOCCUS CAPSULATUS (PRASINOPHYCEAE), THE DIAGNOSTIC “GOLGI‐DECAPORE COMPLEX” AND THE NEWLY DESCRIBED POLYSACCHARIDE “CAPSULAN”

A nonmotile green nanoalga was isolated from the waters over the Cayman Trench in March 1979 and has been maintained in culture as clone URI 266G (CCMP 1202). It was observed to form a copious polysaccharide capsule that presumably originated in the Golgi body and was secreted through a crown of 10 pores in the cell wall, the “decapore.” This multilaminate apical area, lying adjacent to the Golgi, underwent structural changes during morphogenesis. The polysaccharide precursors that coalesced to form the capsule apparently became stainable and visible as they exited the decapore when they cross‐linked with divalent ions in seawater. Cell wall precursors, or a cell wall lamina, surrounded the daughter cells both during synchronous binary fission and after cell separation, with the maternal capsule perhaps acting as a template. Similar prasinophyte isolates have been obtained from widespread areas of the North Atlantic and were divided into two subgroups on the basis of their pigment complement (Hooks et al. 1988). One subgroup, typified by clone Ω 48‐23 (CCMP 1203), was described by Guillard et al. (1991) as Pycnococcus provasolii Guillard within a new family, the Pycnococcaceae. The other subgroup, typified by clone URI 266G (CCMP 1202), contained two unique carotenoids, one of which was uriolide (Foss et al. 1986). Subsequently, Miyashita et al. (1993) described an alga from the western Pacific Ocean that is indistinguishable from URI 266G in both pigment composition and ultrastructure that they named Prasinococcus capsulatus Miyashita et Chihara and placed tentatively in the Pycnococcaceae. They described a curious asexual budding fission. Here we suggest an alternative form of cell division analogous to that observed in the other described Pycnococcaceae. We used theultrastructure of cells in exponential and stationary phases of growth to illustrate synchronous asexual binary fission, the “Golgi‐decapore complex,” and its apparent role in capsule formation. A unique sulfated and carboxylated polyanionic polysaccharide named capsulan is released from this complex.

Methylaminotrophic Bacteria in Xenic Nanoalgal Cultures: Incidence, Significance, and Role of Methylated Algal Osmoprotectants

AbstractBacteria that oxidize methylated amines are ubiquitous in the sea. The likely source of these C1 substrates is the quaternary ammonium osmoprotectant, glycine betaine, which degrades to release trimethylamine (TMA), dimethylamine (DMA), and monomethylamine (MMA). Each of these compounds are successively oxidized to yield formaldehyde, formate, and CO2. The release of methylamines from nanoalgae was determined indirectly by the presence of MMA-oxidizing bacteria in cultures of oceanic algae. Of 19 xenic and axenic pairs of unidentified nanoalgal clones, 6 xenic clones (31.6%) as well as one of the “axenic” counterparts contained methylaminotrophs. A larger survey of 70 algal clones from seven algal classes, revealed 43% as positive, while a group of 78 unidentified clones had a similar methylaminotroph incidence of 41%. When 147 of the clones tested were grouped according to their area of isolation, those from presumably less stratified waters had a relatively low incidence of MMA-oxidizing bacteri...