bluuebunny/crossref_metadata_2025 huggingface dataset:
RESPONSES OF THE PHYTOPLANKTON COMMUNITY GROWTH RATE TO NUTRIENT PULSES IN VARIABLE ESTUARINE ENVIRONMENTS
Authors: Pinckney James L. , Paerl Hans W. , Harrington Monica B.
Published: March 2003

In estuaries, phytoplankton are exposed to rapidly changing conditions that may have profound effects on community structure and function. In these experiments, we evaluated the growth, productivity, and compositional responses of natural phytoplankton communities exposed to limiting nutrient additions and incubation conditions typical of estuarine habitats. Mesocosm bioassays were used to measure the short‐term (2‐day) growth rate, primary productivity, and group‐specific biomass responses of the phytoplankton community in the Neuse River Estuary, North Carolina. A three‐factor (mixing, sediment addition, and nutrient addition) experimental design was applied using 55‐L mesocosm tanks. Growth rates were determined using the 14C photopigment radiolabeling method, and the abundance of algal groups was based on quantification of chemosystematic photopigments by HPLC. For Neuse River Estuary phytoplankton communities, stratified (nonmixed), turbid, and low‐nitrate conditions favored increases in cryptomonad biomass. Mixed, turbid, high‐nitrate conditions were favorable for increased primary productivity and chlorophytes, diatoms, and cyanobacteria. The highest community growth rates occurred under calm, high‐nitrate conditions. This approach provided an assessment of the community‐level phytoplankton responses and insights into the mechanisms driving blooms and bloom species in estuarine waters. The ability to rapidly alter growth rates to capitalize on conditions conducive for growth may play an important role in the timing, extent, and species involved with blooms in estuarine waters. Adaptive growth rate responses of individual species, as well as the community as a whole, further illustrate the sensitivity of estuarine ecosystems to excessive N inputs.
OPTICAL MONITORING AND FORECASTING SYSTEMS FOR HARMFUL ALGAL BLOOMS: POSSIBILITY OR PIPE DREAM?
Authors: Schofield Oscar , Grzymski Joe , Bissett W. Paul , Kirkpatrick Gary J. , Millie David F. , Moline Mark , Roesler Collin S.
Published: March 2003

Monitoring programs for harmful algal blooms (HABs) are currently reactive and provide little or no means for advance warning. Given this, the development of algal forecasting systems would be of great use because they could guide traditional monitoring programs and provide a proactive means for responding to HABs. Forecasting systems will require near real‐time observational capabilities and hydrodynamic/biological models designed to run in the forecast mode. These observational networks must detect and forecast over ecologically relevant spatial/ temporal scales. One solution is to incorporate a multiplatform optical approach utilizing remote sensing and in situ moored technologies. Recent advances in instrumentation and data‐assimilative modeling may provide the components necessary for building an algal forecasting system. This review will outline the utility and hurdles of optical approaches in HAB detection and monitoring. In all the approaches, the desired HAB information must be isolated and extracted from the measured bulk optical signals. Examples of strengths and weaknesses of the current approaches to deconvolve the bulk optical properties are illustrated. After the phytoplankton signal has been isolated, species‐recognition algorithms will be required, and we demonstrate one approach developed for Gymnodinium breve Davis. Pattern‐recognition algorithms will be species‐specific, reflecting the acclimation state of the HAB species of interest.Field data will provide inputs to optically based ecosystem models, which are fused to the observational networks through data‐assimilation methods. Potential model structure and data‐assimilation methods are reviewed.
EVIDENCE FOR INHIBITORS OF SPORANGIUM FORMATION IN LAMINARIA DIGITATA (PHAEOPHYCEAE) DURING THE SEASON OF RAPID GROWTH
Authors: Lüning Klaus , Wagner Andreas , Buchholz Cornelia
Published: March 2003

The pathway from the intercalary frond meristem to distal frond portions was blocked in experimental sporophytes of Laminaria digitata (Huds.) Lamour. in January by cutting 2 or 3 holes (15–25 mm diameter) 5 cm from the base of the frond. This procedure resulted in the formation of sori adjacent to the distal edge of the holes within 5–10 weeks. Frond portions that were cut at least 20 cm away from the stipe–frond transition readily formed sori within 5–7 weeks after isolation from the rest of the thallus. These findings suggest that the basal actively dividing and expanding part of the laminarian frond is the source of inhibitors of sporangium formation that move in a distal direction and keep the young frond free of sori during the season of rapid growth (i.e. during the first part of the year). The natural occurrence of sori during the season of slow growth (i.e. the second part of the year in the Northern Hemisphere) may be due to reduced synthesis and export of inhibitors of sporangium formation from the more or less resting basal meristem.
EFFECT OF NUTRIENT AVAILABILITY ON THE BIOCHEMICAL AND ELEMENTAL STOICHIOMETRY IN THE FRESHWATER DIATOM STEPHANODISCUS MINUTULUS (BACILLARIOPHYCEAE)*
Authors: Lynn Scott G. , Kilham Susan S. , Kreeger Daniel A. , Interlandi Sebastian J.
Published: March 2003

The objective of this study was to examine the differences in the biochemical and elemental stoichiometry of a freshwater centric diatom, Stephanodiscus minutulus (Grun.), under various nutrient regimes. Stephanodiscus minutulus was grown at μmax or 22% of μmax under limitation by silicon, nitrogen, or phosphorus. Cell sizes for nutrient‐limited cultures were significantly smaller than the non‐limited cell sizes, with N‐limited cells being significantly smaller than all other treatments. Compared with the nutrient‐replete treatment, both carbohydrates and lipids increased in Si‐ and P‐limited cells, whereas carbohydrates increased but proteins decreased in N‐limited cells. All of the growth‐limited cells showed an increase of carbohydrate and triglyceride, and a decrease of cell size and polar lipids as a percentage of total lipids. The non‐limited cells also had a significantly higher chl a concentration and galactolipids as a percentage of total lipids than any of the limited treatments, and the low‐Si and low‐P cells had significantly higher values than the low‐N cells. The particulate C concentrations showed significant differences between treatments, with the Si‐ and P‐limited treatments being significantly higher than the N‐ and non‐limited treatments. Particulate Si did not show a strong relationship with any of the parameters measured, and it was the only parameter with no differences between treatments. The low‐Si cells had a significantly higher P content (about two times more) than any other treatment, presumably owing to the luxury consumption of P, and a correspondingly high phospholipid concentration. The elemental data showed that S. minutulus had a high P demand with low optimum N:P (4) and Si:P (10) ratios and a C:N:P ratio of 109:16:2.3. The particulate C showed a positive relationship with POM (r = 0.93), dry weight (r = 0.88), lipid (r = 0.87) and protein (r = 0.84, all P < 0.0001). Particulate N showed a positive relationship with galactolipids (r = 0.95), protein (r = 0.90), dry weight (r = 0.78), lipid (r = 0.75), and cell volume (r = 0.64, all P < 0.0001). It is evident that nutrient limitation in the freshwater diatom S. minutulus has pronounced effects on its biochemical and elemental stoichiometry.
Nutrient uptake and alkaline phosphatase (ec 3:1:3:1) activity of emiliania huxleyi (PRYMNESIOPHYCEAE) during growth under n and p limitation in continuous cultures
Authors: Riegman Roel , Stolte Willem , Noordeloos Anna A. M. , Slezak Doris
Published: March 2003

Emiliania huxleyi (strain L) expressed an exceptional P assimilation capability. Under P limitation, the minimum cell P content was 2.6 fmol P·cell−1, and cell N remained constant at all growth rates at 100 fmol N·cell−1. Both, calcification of cells and the induction of the phosphate uptake system were inversely correlated with growth rate. The highest (cellular P based) maximum phosphate uptake rate (VmaxP) was 1400 times (i.e. 8.9 h−1) higher than the actual uptake rate. The affinity of the P‐uptake system (dV/dS) was 19.8 L·μmol−1·h−1 at μ = 0.14 d−1. This is the highest value ever reported for a phytoplankton species. Vmax and dV/dS for phosphate uptake were 48% and 15% lower in the dark than in the light at the lowest growth rates.

The half‐saturation constant for growth was 1.1 nM. The coefficient for luxury phosphate uptake (Qmaxt/Qmin) was 31. Under P limitation, E. huxleyi expressed two different types of alkaline phosphatase (APase) enzyme kinetics. One type was synthesized constitutively and possessed a Vmax and half‐saturation constant of 43 fmol MFP·cell−1·h−1 and 1.9 μM, respectively. The other, inducible type of APase expressed its highest activity at the lowest growth rates, with a Vmax and half‐saturation constant of 190 fmol MFP·cell−1·h−1 and 12.2 μM, respectively. Both APase systems were located in a lipid membrane close to the cell wall. Under N‐limiting growth conditions, the minimum N quotum was 43 fmol N·cell−1. The highest value for the cell N‐specific maximum nitrate uptake rate (VmaxN) was 0.075 h−1; for the affinity of nitrate uptake, 0.37 L·μmol−1·h−1. The uptake rate of nitrate in the dark was 70% lower than in the light. N‐limited cells were smaller than P‐limited cells and contained 50% less organic and inorganic carbon. In comparison with other algae, E. huxleyi is a poor competitor for nitrate under N limitation. As a consequence of its high affinity for inorganic phosphate, and the presence of two different types of APase in terms of kinetics, E. huxleyi is expected to perform well in P‐controlled ecosystems.
CELL AGGREGATION OF THE CYANOBACTERIUM SYNECHOCOCCUS ELONGATUS: ROLE OF THE ELECTRON TRANSPORT CHAIN
Authors: Koblížek Michal , Komenda Josef , Masojídek Jiří , Pechar Libor
Published: March 2003

Cell aggregation, the formation of irregular clusters of individual cells or filaments, is frequently observed in many cyanobacterial species. The mechanism(s) and potential causes of cell aggregation were studied in a thermophilic strain of the unicellular cyanobacterium Synechococcus elongatus Näg. We found that cell aggregation occured as the natural response of a healthy, well‐growing culture to a sudden increase in irradiance. We propose that aggregation represents a fast (time scale in minutes), light‐adapting mechanism, affected by both light quality and the presence of substances altering photosynthetic electron transfer. Our data suggest an involvement of electron transfer downstream of PSI, with reactive oxygen species triggering the signal. Aggregation was an ATP‐independent process and did not require de novo protein synthesis. We suggest a specific role of glutathione in this process based on its ability to induce aggregation in the dark.
Speciation withinblidingia minima(chlorophyta) in japan: evidence from morphology, ontogeny, and analyses of nuclear rdna its sequence
Authors: Woolcott Geoffrey W. , Iima Masafumi , King Robert J.
Published: March 2003

The genusBlidingiais a common, sometimes abundant, component of northern hemisphere temperate and subarctic shores. Species determination relies on characteristic differences in morphology and early ontogenic development. Within the speciesBlidingia minima(Naegeli ex Kuetzing) Kylin in Japan, however, there appear to be three distinct types, the F‐, D‐, and M‐types, which are differentiated in early ontogeny. The M‐type can be further categorized into three subtypes. Results of intensive field and culture studies supported the view that morphological characteristics do not reliably separate the F‐, D‐, and M‐types and that all three may potentially cross breed. The F‐type has characteristics in early ontogeny of the speciesB. chadefaudii(  J. Feldmann) Bliding in European waters and this, combined with the morphological and cross breeding studies, suggest thatB. chadefaudiishould be merged withB. minima.In this study, molecular analyses of nuclear rDNA from samples of the F‐ and D‐types indicated that both have a distinctive and characteristic identity. Sequence data also examined from two of the M‐type subtypes indicated that each of these also has a characteristic molecular identity clearly distinguished from that of the F‐ and D‐types. Analyses indicated that there is a close relationship between the D‐type and one of the M‐type subtypes, and that these are more closely related to the F‐type than to the other M‐type examined. Comparison with studies of this gene region in other ulvophytic algae indicated a wide range of variation withinB. minima.Such variation may be useful in assessing distribution patterns in Japanese waters of the developmental types within this species.
CARBON PARTITIONING WITHINPHAEOCYSTIS ANTARCTICA(PRYMNESIOPHYCEAE) COLONIES IN THE ROSS SEA, ANTARCTICA
Authors: Mathot Sylvie , Smith Walker O. , Carlson Craig A. , Garrison David L. , Gowing Marcia M. , Vickers Chrystal L.
Published: March 2003

The haptophytePhaeocystis antarcticaKarsten is a dominant species within the seasonal bloom in the Ross Sea. One of the unique characteristics of this form is that carbon is partitioned between the cells and the colonial matrix, a relationship that is poorly documented for this region. We combined particulate organic carbon measurements and microscopic analysis ofP. antarctica‐dominated samples to assess the contribution of single cells, colony‐associated cells, and mucilage to the carbon concentrations of waters withP. antarctica.Two cruises to the Ross Sea were completed, one in austral spring 1994 and one in summer 1995–1996. In 1994 the bloom was dominated by colonialP. antarcticathat contributed up to 96% of the total autotrophic carbon, whereas in 1995–1996 a mixture ofP. antarcticaand diatoms occurred.P. antarcticacolony volume (V ) was related to colonial cell number (NC) by the relationshipV= 417 ×NC1.67. Total colony carbon (CCOL) was calculated as the sum of cell carbon (CCC) and mucus‐related carbon (CM). We found the contribution of mucus carbon to be 213 ng C mm−3of colony volume. ForP. antarctica‐dominated assemblages sampled at the peak of the bloom, CMrepresented a minor fraction (14 ± 4%) of colony carbon, and during early summer conditions CMwas at most 33% of CCOL. This organism plays a cardinal role in the carbon cycle of many regions. These results constrain the partitioning of carbon between cellular material and the colony matrix, information that is necessary to accurately describe the biogeochemical cycles influenced by this species.
A ZYGOTE‐SPECIFIC PROTEIN WITH HYDROXYPROLINE‐RICH GLYCOPROTEIN DOMAINS AND LECTIN‐LIKE DOMAINS INVOLVED IN THE ASSEMBLY OF THE CELL WALL OF CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)
Authors: Suzuki Lena , Woessner Jeffrey P. , Uchida Hidenobu , Kuroiwa Haruko , Yuasa Yasuhito , Waffenschmidt Sabine , Goodenough Ursula W. , Kuroiwa Tsuneyoshi
Published: March 2003

The cell wall of Chlamydomonas reinhardtii zygotes, which forms rapidly after the fusion of wall‐free gametes, provides a tractable system for studying the properties and assembly of hydroxyproline‐rich glycoproteins, the major proteinaceous components of green algal and plant cell walls. We report the cloning of the zsp2 gene and the analysis of its ZSP‐2 product, a 58.9 kDa polypeptide that is synthesized exclusively by zygotes. The protein contains two (SP)x repeats, establishing it as a member of the cell wall hydroxyproline‐rich glycoproteins family. It also contains a 4‐fold iteration of an amino acid sequence centered around cysteine residues, a configuration found in both plant and animal lectins. Furthermore, we report four observations on pellicle composition and production. First, cell‐free preparations of the pellicle matrix are rich in hydroxyproline, arabinose, and galactose and contain bundles of very long fibrils. Second, glutathione blocks pellicle formation and results in the accumulation of long fibrils in the growth medium. Third, antibody to ZSP‐2 also blocks pellicle formation. Fourth, ZSP‐2 immunolocalizes to the boundary between the outer layers of the wall proper and the pellicle matrix. These observations are consistent with the possibility that the Cys‐rich (glutathione‐sensitive) lectin‐like domains of ZSP‐2 may bind to sugar residues on the long fibrils and anchor them to the cell wall, thereby initiating and maintaining pellicle formation.
Nanoscale uniformity of pore architecture in diatomaceous silica: a combined small and wide angle x‐ray scattering study
Authors: Vrieling Engel G. , Beelen Theo P. M. , Van Santen Rutger A. , Gieskes Winfried W. C.
Published: March 2003

Combined small and wide angle X‐ray scattering (SAXS and WAXS) analysis was applied to purified biogenic silica of cultured diatom frustules and of natural populations sampled on marine tidal flats. The overall WAXS patterns did not reveal crystalline phases (WAXS domain between 0.07 to 0.5 nm) in this biogenic silica, which is in line with previous reports on the amorphous character of the SiO2 matrix of diatom frustules. One exception was the silica of the pennate species Cylindrotheca fusiformis Reimann et Lewin, which revealed wide peaks in the WAXS spectra. These peaks either indicate the presence of a yet unknown crystalline phase with a repetitive distance (d‐value ≈0.06 nm) or are caused by the ordering of the fibrous silica fragments; numerous girdle bands. The SAXS spectra revealed the size range of pores (diameter d between 3.0 and 65 nm), the presence of distinct pores (slope transitions), and structure factors (oscillation of the spectra). All slopes varied in the range of −4.0 to −2.5, with two clear common regions among species: d < 10 nm (slopes –4, denoted as region I and also called the Porod region), and 10.0 < d < 40.0 nm (slopes −2.9 to −3.8, denoted as region II). The existence of these common regions suggests the presence of comparable form (region I) and structure (region II) factors, respectively the shape of the primary building units of the silica and the geometry of the pores. Contrast variation experiments using dibromomethane to fill pores in the SiO2 matrix showed that scattering was caused by pores rather than silica particles. Electron microscopic analysis confirmed the presence of circular, elliptical, and rectangular pores ranging in size from 3 to 65 nm, determining the structure factor. The fine architecture (length/width ratio of pore diameters) and distribution of the pores, however, seemed to be influenced by environmental factors, such as the salinity of and additions of AlCl3 to the growth medium. The results indicate that diatoms deposit silica with pores <50 nm in size and are highly homologous with respect to geometry. Consequently, it is suggested that in diatoms, whether pennate or centric, the formation of silica at a nanoscale level is a uniform process.
DEVELOPMENT OF PROTOPLASTS OFULVA FASCIATA(CHLOROPHYTA) FOR ALGAL SEED STOCK
Authors: Chen Yean‐Chang , Shih Hsiu‐Chuan
Published: March 2003

The aim of this study was to isolate and cultivate protoplasts of the green algaUlva fasciataDelile and subsequently induce them to form a microthallus suspension for algal seed stock. The protoplasts were covered with secreted mucilage following 6 h of culture when viewed with SEM. The mucilage fused to form thick layers during day 1 of culture. Microfibrillar cell walls were deposited into the thick layers of mucilage on the 5th day of culture. An average of about 10% of the freshly isolated protoplasts began to divide at 6–14 days. These protoplasts subsequently developed varied morphologies, depending on the time of collection during the year. Protoplasts isolated fromU. fasciatacollected in March to June developed frond thalli or microthalli when they were cultured in low or high densities (cells/area), respectively. The microthallus suspension was cultured for more than two years at 10–40μmol·m−2·s−1. Frond thalli formed when the suspension was cultivated at 100–160μmol·m−2·s−1. Therefore, microthallus suspension can serve as a seed stock ofU. fasciata.
Caloglossa intermedia, sp. nov. (Rhodophyta) from the western atlantic coast: molecular and morphological analyses with special reference to C. leprieurii and C. monosticha
Authors: Kamiya Mitsunobu , West John A. , Zuccarello Giuseppe C. , Kawai Hiroshi
Published: March 2003

Caloglossa intermedia, sp. nov. is described from estuaries and salt marshes of Atlantic North America. This species is related to C. leprieurii (Montagne) G. Martens based on the position of rhizoids, whereas it is more similar to C. monosticha Kamiya in the number of cell rows at the nodes. Rhizoidal development of this alga also shows an intermediate characteristic between C. leprieurii and C. monosticha. Crosses were successful between the strains of C. intermedia from Georgia and South Carolina, but neither strain was interfertile with morphologically related species. C. intermedia from Georgia, New Jersey, and South Carolina had identical DNA sequences in the Rubisco spacer and flanking regions of rbcL and rbcS. This alga was more closely related to C. leprieurii in a molecular phylogenetic analysis. The evolution of each morphological character is discussed.
NITRATE TRANSPORTER GENES FROM THE DIATOM CYLINDROTHECA FUSIFORMIS (BACILLARIOPHYCEAE): mRNA LEVELS CONTROLLED BY NITROGEN SOURCE AND BY THE CELL CYCLE
Authors: Hildebrand Mark , Dahlin Katherine
Published: March 2003

The molecular characterization of components involved in nitrate uptake and assimilation in phytoplankton is likely to provide new insights into these processes, their regulation, and their effect on primary production. We report the cloning and initial characterization of the first nitrate transporter genes in a marine organism, from the diatom Cylindrotheca fusiformis Reimann et Lewin. A clone isolated from a silicon‐responsive cDNA library was shown by sequence comparison to encode a homolog of high‐affinity nitrate transporters. The C. fusiformis nitrate transporter cDNA was named NAT (NitrAte Transporter). The NAT cDNA was used to isolate a genomic clone that contained two additional nitrate transporter genes, NAT1 and NAT2, arranged in tandem. The cDNA and two genomic sequences were highly conserved, and only 18 of 1446 nucleotides in the coding region differed. At least four copies of NAT genes were present in C. fusiformis and as shown by hybridization, multiple copies were present in other diatom species. The transcript abundance of NAT genes in cultures with different nitrogen sources was monitored by RNase protection assays. NAT mRNA levels were high in the presence of nitrate, at nearly the same level during nitrogen starvation, and also high in urea‐containing cultures. Lower mRNA levels occurred in nitrite‐grown cultures. NAT transcript levels were highly repressed with NH4Cl or NH4NO3 as the nitrogen source, although very low amounts were detected. These results suggested that monitoring NAT mRNA levels could serve as a marker for (1) nitrate uptake in nitrate medium, (2) nitrogen starvation, and (3) ammonium use by virtue of absence of expression. NAT mRNA levels were not directly regulated by light or dark, but were apparently related to cellular growth and protein synthesis. Using light/dark synchronized cultures to monitor cell cycle responses, NAT mRNA levels were high in early G1 phase, decreased through the remainder of G1, then increased during DNA synthesis in S phase and into G2, and finally decreased after M phase. In silicon‐starvation synchronized cultures, levels were high at the G1/S phase boundary, high throughout S and G2, and finally decreased after M phase. It was clear that NAT expression, and by inference nitrate uptake, did not occur at continuous levels throughout the cell cycle. The results of the RNase protection experiments suggested that transcriptional regulation is a major contributing factor in the control of diatom nitrate uptake. The cloning of the C. fusiformis nitrate transporter genes provides a new tool for investigating diatom nitrogen uptake and metabolism. In addition, the regulation of NAT expression by nitrogen source is likely to be useful in developing techniques to specifically control the expression of genes fused to NAT regulatory sequences in transgenic diatoms.
Affinities of the freshwater red algaAudouinella macrospora(Florideophyceae, Rhodophyta) and related forms based on ssu rrna gene sequence analysis and pit plug ultrastructure
Authors: Pueschel Curt M. , Saunders Gary W. , West John A.
Published: March 2003

Small subunit rDNA sequencing and transmission electron microscopy were performed to clarify the ordinal affinities ofAudouinella macrospora(Wood) Sheath et Burkholder isolates 3394, 3395, and 3603, as well asChantransiasp. isolate 3585. Culture 3603 is known to produce thalli ofBatrachospermum ‐like morphology under certain culture conditions. Sequence analyses unequivocally placed the threeAudouinella macrosporaisolates in a clade withBatrachospermum macrosporumMontagne of the Batrachospermales, andChantransiasp. was found to have affinities withB. louisianaeSkuja andB. virgato‐decaisneanumSirodot. The pit plugs of theAudouinella macrosporacultures 3394 and 3395 were nearly identical in size and structure, having thickened plug caps and no cap membranes. Both of these features agree with those of the Batrachospermaceae, with the latter feature showing batrachospermacean rather than acrochaetioid affinities. Pit plugs in the chantransia phase of 3603 were similar, but the plug caps were less well developed. TheBatrachospermumphase generated from 3603 had pit plugs that were variable in diameter, according to location in the thallus, thus reflecting the more variable cell size in this phase. Dome‐like outer caps, considered typical ofBatrachospermum, were present between cells of the determinate lateral filaments. The pit plugs ofChantransiasp. had prominent, dome‐like outer caps, but the plug cores were strikingly and consistently smaller in diameter than those of theA. macrosporachantransia cultures, suggesting that plug diameter may be of systematic value in some contexts.
GRACILARIA EDULIS (RHODOPHYTA) AS A BIOLOGICAL INDICATOR OF PULSED NUTRIENTS IN OLIGOTROPHIC WATERS
Authors: Costanzo Simon D. , O'donohue Mark J. , Dennison William C.
Published: March 2003

The response of the marine macroalga Gracilaria edulis (Gmelin) Silva to nutrient pulses of varying magnitude was investigated to test its applicability as a marine bioindicator at two oligotrophic locations. After exposure to nutrient pulses, algal amino acid, tissue nitrogen, and chlorophyll a content were assessed relative to algae incubated under control conditions (no nutrient enrichment). The smallest nutrient pulse involved a nutrient enrichment experiment conducted within a coral atoll, whereas two larger pulses resulted from sewage discharge to a tropical coastal bay. After exposure to the smallest nutrient pulse (10 × ambient), only changes in macroalgal amino acid concentration and composition were detected (mainly as increases in citrulline). At 100 × ambient concentrations, increases in tissue % nitrogen of the macroalgae were detected, in addition to responses in amino acids. Macroalgae exposed to the highest nutrient pulse (1000 × ambient) responded with increased chlorophyll a, tissue nitrogen, and amino acids within the three day incubation period. In contrast to these algal responses, analytical water sampling techniques failed to detect elevated nutrients when nutrient pulses were not occurring. The responses of this algal bioindicator to variable nutrient pulses may provide a useful tool for investigating the source and geographical extent of nutrients entering oligotrophic coastal waters.
PHYLOGENETIC POSITION OF THE OOCYSTACEAE (CHLOROPHYTA)
Authors: Hepperle Dominik , Hegewald Eberhard , Krienitz Lothar
Published: March 2003

The complete 18S rRNA gene sequences of three Oocystis A. Braun species (Oocystaceae) and three other chlorococcal algae, Tetrachlorella alternans (G. M. Smith) Korš. (Scenedesmaceae), Makinoella tosaensis Okada (Scenedesmaceae), and Amphikrikos cf. nanus (Fott & Heynig) Hind. (Chlorellaceae) were determined and subjected to four different phylogenetic analysis algorithms. Independent of the reconstruction method, these taxa clustered together as a monophyletic group (Oocystaceae) within the Trebouxiophyceae. This result was supported by high bootstrap values. A comparison of morphological data with the phylogenetic reconstructions indicated that the evolution of Oocystaceae was accompanied by a reduction in the number of plastids. This study fully supports the taxonomic assignment of the Oocystaceae as a distinct family. The diacritic criterion that the cell walls are composed of several cellulose layers with perpendicular fibril orientations is in accordance with the molecular data.
MOLECULAR SYSTEMATICS OF THE FLORIDEOPHYCEAE (RHODOPHYTA) USING NUCLEAR LARGE AND SMALL SUBUNIT rDNA SEQUENCE DATA
Authors: Harper James T. , Saunders Gary W.
Published: March 2003

Sequence data are presented for approximately 85% of the nuclear large subunit (LSU) rDNA gene for one member of the Bangiophyceae and 47 members of the Florideophyceae, the latter representing all but one of the currently recognized florideophyte orders. Distance, parsimony, and maximum likelihood analyses of these data were used to generate phylogenetic trees, and bootstrap resampling was implemented to infer robustness for distance and parsimony results. LSU phylogenies were congruent with published nuclear small subunit (SSU) rDNA results in that four higher level florideophyte lineages were resolved: lineage 1, containing the order Hildenbrandiales; lineage 2, recovered only under distance analysis, composed of the orders Acrochaetiales, Balliales, Batrachospermales, Corallinales, Nemaliales, Palmariales, and Rhodogorgonales; lineage 3, containing the Ahnfeltiales; and lineage 4, composed of the orders Bonnemaisoniales, Ceramiales, Gelidiales, Gigartinales, Gracilariales, Halymeniales, Plocamiales, and Rhodymeniales. Analyses were also performed on a combined LSU–SSU data set and an SSU‐only data set to account for differences in taxon sampling relative to published studies using this latter gene. Combined LSU–SSU analyses resulted in phylogenetic trees of similar topology and support to those obtained from LSU‐only analyses. Phylogenetic trees produced from SSU‐only analyses differed somewhat in particulars of branching within lineages 2 and 4 but overall were congruent with the LSU‐only and combined LSU–SSU results. We close with a discussion of the phylogenetic potential that the LSU has displayed thus far for resolving relationships within the Florideophyceae.
BIOGEOGRAPHY AND SPECIATION IN THEPANDORINA/VOLVULINA(CHLOROPHYTA) SUPERCLADE
Authors: Coleman Annette W.
Published: March 2003

Mating affinity, nuclear rDNA internal transcribed spacer (ITS) sequence, and geographic distribution of more than 100 isolates ofPandorina,Volvulina, andYamagishiellawere determined. Comparative analysis of ITS sequences reaffirmed the unity ofPandorina morumand its separation from all other species of Volvocaceae except those ofVolvulina.This latter genus, represented by four species, appears to represent only morphological variants of severalP. morumsubclades. TheP. morumclade (including also additional species such asP. smithiiandP. colemaniae) encompasses an evolutionary span, as determined by comparison of ITS, greater than either of the multispecies generaGoniumorEudorina.There are at least 30Pandorina/Volvulinasyngens, sexually isolated groups, so far as can be determined, among the current collection of strains. In addition, as in other volvocacaean genera, two clones are homothallic, capable of forming zygotes within a genetic clone. The existence of so many syngens suggests that considerable evolutionary diversification of the genes controlling gamete compatibility and intercross survival has occurred, unaccompanied by significant morphological change. Within each syngen, genetic distance increases with geographic distance between collection sites. At least half of the isolates studied must have been introduced northward since the Pleistocene. Although we probably know more about characters in this group of algae than any other algal group, in part because they are so easy to culture, we are still largely ignorant of what circumscribes their niche in nature. The study of all these organisms, distributed throughout the world presumably by the activities of shorebirds, emphasizes the evolutionary role of mating genes in the inevitable formation of new genetically isolated subclades in these eukaryotes and provides initial data on their rate of appearance versus their rate of distribution over the earth.
UNDERSTANDING MEMBRANE FUNCTION
Authors: Raven John A. , Brownlee Colin
Published: March 2003

Work on algae has had wide‐ranging impacts on our understanding of membrane function. Work on giant cells of freshwater and marine algae has been very important in defining and characterizing active transport systems for ions and other solutes and for studying other transport processes at the plasmalemma and tonoplast. Such work was particularly important in changing the focus of studies of higher plant membrane transport processes in the 1960s. Recent technical and genetic advances mean that studies formerly confined to large algal cells can now also be performed on higher plants and microalgae, but work on giant cells still makes important contributions. Studies on fucoid embryos continues to make significant contributions to our understanding of the role of transmembrane calcium fluxes in early development. This work has wide‐ranging implications for the development of other organisms.
MITOSIS INDUNALIELLA BIOCULATA(CHLOROPHYTA): CENTRIN BUT NOT BASAL BODIES ARE AT THE SPINDLE POLES
Authors: Grunow Andrea , Lechtreck Karl‐Ferdinand
Published: March 2003

Centrin, a 20 kDa calmodulin‐like protein, is located in various basal body‐associated fibers in protists. We used indirect immunofluorescence of isolated cytoskeletons or methanol‐fixed cells to analyze the distribution of centrin during mitosis of the biflagellate green algaDunaliella bioculata(Butcher). The distance between the nucleus and the basal apparatus decreased in late interphase, presumably caused by the contraction of the two centrin‐containing nucleus–basal body connectors (NBBCs). During prophase, centrin accumulated on the new basal bodies as shown by postembedding immunogold labeling of serial thin sections. The new basal bodies were in close contact with plaque‐like structures on the nuclear envelope. In mitotic cells, basal body pairs were separated and positioned at a considerable distance from the poles of the mitotic spindle. At this stage, we observed four separated centrin dots, two associated with the pairs of basal bodies and two located at the spindle poles as shown by double immunofluorescence, including anti‐tubulin staining. The latter signals corresponded to an accumulation of centrin between the plasma membrane and the nuclei, indicating that centrin could be involved in mitotic movements of the nuclei. In telophase, centrin was observed along the nuclear surface and one new NBBC developed in each cell half. Our results demonstrate that centrin is present at the acentriolar spindle poles ofDunaliellaindependently from its localization in the basal apparatus.
IMPACT OF ALGAL RESEARCH IN AQUACULTURE
Authors: Wikfors Gary H. , Ohno Masao
Published: March 2003

Algal aquaculture worldwide is estimated to be a $5–6 billion U.S. per year industry. The largest portion of this industry is represented by macroalgal production for human food in Asia, with increasing activity in South America and Africa. The technical foundation for a shift in the last half century from wild harvest to farming of seaweeds lies in scientific research elucidating life histories and growth characteristics of seaweeds with economic interest. In several notable cases, scientific breakthroughs enabling seaweed‐aquaculture advances were not motivated by aquaculture needs but rather by fundamental biological or ecological questions. After scientific breakthroughs, development of practical cultivation methods has been accomplished by both scientific and commercial‐cultivation interests. Microalgal aquaculture is much smaller in economic impact than seaweed cultivation but is the subject of much research. Microalgae are cultured for direct human consumption and for extractable chemicals, but current use and development of cultured microalgae is increasingly related to their use as feeds in marine animal aquaculture. The history of microalgal culture has followed two main paths, one focused on engineering of culture systems to respond to physical and physiological needs for growing microalgae and the other directed toward understanding the nutritional needs of animals—chiefly invertebrates such as mollusks and crustaceans—that feed upon microalgae. The challenge being addressed in current research on microalgae in aquaculture food chains is to combine engineering and nutritional principles so that effective and economical production of microalgal feed cultures can be accomplished to support an expanding marine animal aquaculture industry.
GENETICS AND SEXUAL BEHAVIOR OF THE PHEROMONE PRODUCER CHLAMYDOMONAS ALLENSWORTHII (CHLOROPHYCEAE)
Authors: Coleman Annette W. , Jaenicke Lothar , Starr Richard C.
Published: March 2003

Strains of Chlamydomonas allensworthii Starr, Marner, and Jaenike isolated from 13 sites worldwide in distribution were compared to assess the congruity of DNA similarity, sexual behavior, and pheromone response type. The isolates fell into two pheromone response categories. One of these included isolates of widespread distribution in the United States, and all appeared to be capable of forming zygotes inter se. The second group was larger and more complex, encompassing four mating groups as defined by zygote formation. Comparison of DNA sequences (internal transcribed spacers 1 and 2 of the nuclear rDNA repeats) fully supported the same subdivision of the isolates. Both selfing and outbreeding clones were among the isolates. The possibility that other Volvocales species might respond to these same pheromones remains to be tested.
SPATIAL PARADIGMS OF LOTIC DIATOM DISTRIBUTION: A LANDSCAPE ECOLOGY PERSPECTIVE
Authors: Passy Sophia I.
Published: March 2003

Spatial distributional patterns of benthic diatoms and their relation to current velocity were investigated in an unshaded cobble‐bottom reach of White Creek (Washington County, NY). On 27 August 1999, diatoms were sampled and current velocity and depth were measured on a regular square sampling grid with a grain size of 0.01 m2, interval of 0.5 m, and extent of 16 m2. The relative abundance of the 18 common diatom species enumerated in the 81 samples was subjected to detrended correspondence analysis (DCA). The first axis (DCA1) explained 51% of the variance in diatom data and separated the samples according to current regimes. The spatial autocorrelation of DCA1 sample scores in deposition and erosion regions of White Creek was determined by Moran's I statistic to indicate patch size. In White Creek the patch length of all diatom communities was more than 3.1 m, whereas the patch width was 1 m in the deposition region and 0.5 m in the erosion region. There were 5 dominant diatom taxa, Achnanthes minutissima Kütz. et vars, Fragilaria capucina Dezmazières et vars, F. crotonensis Kitt., Diatoma vulgaris Bory, and Synedra ulna (Nitz.) Ehr. et vars. The patch length of the dominant species varied from 1 to more than 4.1 m, whereas the patch width, if defined, was 0.5 m. Achnanthes minutissima and F. capucina, the two diatom species with the highest relative abundance, displayed spatially structured patches of low abundance and comparatively random patches of high abundance, suggesting broad scale abiotic control of species performance in low abundance regions and finer scale biotic control of high abundance areas. Another objective of this study was to test the hypothesis that higher current velocities, which generally impede immigration, would increase randomness and complexity (i.e. homogeneity of diatom distributional patterns). The spatial complexity in low versus high velocity transects was determined by calculating the respective fractal dimension (D) of DCA1 scores. D of DCA1 was higher in the higher current velocity transects, suggesting that spatial complexity and homogeneity of diatom communities increased in faster currents. Partial canonical correspondence analysis was conducted on diatom, environmental, and spatial data to assess how much of the variance in species distribution could be attributed to environmental (current velocity and depth) versus spatial factors. The variance of species data, explained by the environment (exclusively current velocity), was 38%; whereas space alone contributed only 10%, indicating that 1) current velocity was the major factor that controlled diatom distribution in streams and 2) there were other spatially dependent variables, most likely biotic, but their role in shaping diatom communities was minor.
NUTRIENT‐LIMITED GROWTH OF AUREOUMBRA LAGUNENSIS (PELAGOPHYCEAE), WITH IMPLICATIONS FOR ITS CAPABILITY TO OUTGROW OTHER PHYTOPLANKTON SPECIES IN PHOSPHATE‐LIMITED ENVIRONMENTS
Authors: Liu Hongbin , Laws Edward A. , Villareal Tracy A. , Buskey Edward J.
Published: March 2003

Growth and chemical compositional characteristics of the brown tide‐forming alga, Aureoumbra lagunensis Stockwell, DeYoe, Hargraves et Johnson, were studied through a series of nitrogen‐limited and phosphate‐limited continuous cultures over a range of growth rates. The specific growth rate of A. lagunensis was hyperbolically related to the cell quota of the limiting nutrient in ammonium‐limited cultures. In phosphate‐limited cultures, the relationship was best described by a straight line. The N cell quota of A. lagunensis ranges from about 20 fmol at zero growth rate under N‐limited conditions to a high of roughly 85 fmol under N‐replete conditions. Similarly, the P cell quota of A. lagunensis ranges from about 0.15 fmol at zero growth rate under P‐limited conditions to a high of 2 fmol under P‐replete conditions. Aureoumbra lagunensis has a very high N:P critical ratio (>100). The high N:P critical ratio, as well as the organism's apparent ability to use forms of phosphorus other than phosphate under severe phosphate deficiency, may partially explain its success in P‐limited environments, such as the Laguna Madre. In addition, a uniqe quadratic relationship between the productivity index (PI) and growth rate was discovered. Such a relationship supports an earlier argument that PI may not be a good indicator of nutritional status.
HEMOLYTIC ACTIVITY OF HETEROCAPSA CIRCULARISQUAMA (DINOPHYCEAE) AND ITS POSSIBLE INVOLVEMENT IN SHELLFISH TOXICITY
Authors: Oda Tatsuya , Sato Yoji , Kim Daekyung , Muramatsu Tsuyoshi , Matsuyama Yukihiko , Honjo Tsuneo
Published: March 2003

Heterocapsa circularisquama Horiguchi is lethal to shellfish, particularly bivalves such as pearl oysters (Pinctada fucata Gould). No detrimental effects of this flagellate on fish have been observed thus far. In this study, we found that H. circularisquama causes mammalian erythrocytes to lyse. Among the erythrocytes tested, rabbit erythrocytes showed the highest susceptibility, whereas erythrocytes from cattle, sheep, and human were relatively insensitive. Heterocapsa triquetra Stein, which is morphologically similar to H. circularisquama but not toxic to bivalves, showed no hemolytic activity toward rabbit erythrocytes. Culture supernatant or ultrasonic‐ruptured cells of H. circularisquama showed only weak hemolytic activity. Hemolytic activity was found in the ethanol extract of H. circularisquama cells, suggesting that the hemolytic agents may be more stable in ethanol than in aqueous solution. Both an intact flagellate cell suspension and the ethanol extract caused morphological changes and eventual collapse of unfertilized eggs of Pacific oyster. Furthermore, the ethanol extract was lethal to the microzooplankton rotifer Brachionus plicatilis Müller, which is highly sensitive to H. circularisquama. Our results suggest that a hemolytic toxin produced by H. circularisquama may be one of the causative agents responsible for the shellfish toxicity.
FLUORESCENCE‐BASED MAXIMAL QUANTUM YIELD FOR PSII AS A DIAGNOSTIC OF NUTRIENT STRESS
Authors: Parkhill Jean‐Paul , Maillet Gary , Cullen John J.
Published: March 2003

In biological oceanography, it has been widely accepted that the maximum quantum yield of photosynthesis is influenced by nutrient stress. A closely related parameter, the maximum quantum yield for stable charge separation of PSII, (φPSII)m, can be estimated by measuring the increase in fluorescence yield from dark‐adapted minimal fluorescence (Fo) to maximal fluorescence (Fm) associated with the closing of photosynthetic reaction centers with saturating light or with a photosynthetic inhibitor such as 3′‐(3,4‐dichlorophenyl)‐1′,1′‐dimethyl urea (DCMU). The ratio Fv/Fm (= (Fm− Fo)/Fm) is thus used as a diagnostic of nutrient stress. Published results indicate that Fv/Fm is depressed for nutrient‐stressed phytoplankton, both during nutrient starvation (unbalanced growth) and acclimated nutrient limitation (steady‐state or balanced growth). In contrast to published results, fluorescence measurements from our laboratory indicate that Fv/Fm is high and insensitive to nutrient limitation for cultures in steady state under a wide range of relative growth rates and irradiance levels. This discrepancy between results could be attributed to differences in measurement systems or to differences in growth conditions. To resolve the uncertainty about Fv/Fm as a diagnostic of nutrient stress, we grew the neritic diatom Thalassiosira pseudonana (Hustedt) Hasle et Heimdal under nutrient‐replete and nutrient‐stressed conditions, using replicate semicontinuous, batch, and continuous cultures. Fv/Fm was determined using a conventional fluorometer and DCMU and with a pulse amplitude modulated (PAM) fluorometer. Reduction of excitation irradiance in the conventional fluorometer eliminated overestimation of Fo in the DCMU methodology for cultures grown at lower light levels, and for a large range of growth conditions there was a strong correlation between the measurements of Fv/Fm with DCMU and PAM (r2 = 0.77, n = 460). Consistent with the literature, nutrient‐replete cultures showed consistently high Fv/Fm (∼0.65), independent of growth irradiance. Under nutrient‐starved (batch culture and perturbed steady state) conditions, Fv/Fm was significantly correlated to time without the limiting nutrient and to nutrient‐limited growth rate before starvation. In contrast to published results, our continuous culture experiments showed that Fv/Fm was not a good measure of nutrient limitation under balanced growth conditions and remained constant (∼0.65) and independent of nutrient‐limited growth rate under different irradiance levels. Because variable fluorescence can only be used as a diagnostic for nutrient‐starved unbalanced growth conditions, a robust measure of nutrient stressed oceanic waters is still required.