SEASONAL GROWTH,BIOMASS, AND REPRODUCTIVE BEHAVIOR OF THREE SPECIES OF RED ALGAE IN GODAVARI ESTUARY,INDIA1

Growth and different phases in the life histories of Bos-trychia tenella (Vohl.) J. Ag., Caloglossa leprieurii (Mont.) J. Ag., and Catenella impudica (Mont.) J. Ag. were estimated for 23 months from January 1986 to December 1987 in the Gautami Godavari estuary of lndia. Seasonal data on hydrographical conditions, biomass, and plant length were collected from three stations in this estuary. Biomass was minimum in August and September and maximum in January and February, as was frond length of tetrasporic and vegetative plants. Temperatures of 24°–27°C and salinities of 5–20 ppt coincided with optimal growth for all three algae. In all three species, tetrasporophytes were present in all months of the year without any seasonal periodicity, and nearly 50% of the plants were tetrasporophytes. The gametophytes of B. tenella and C. leprieurii and cystocarpic plants of C. impudica occurred from October to May, with greatest abundance in January. The abundance of spermatangial and cystocarpic plants in the populations of B. tenella and C. leprieurii ranged from 3 to 15%. Spermatangial plants of Catenella impudica could not be identified, and the abundance of cystocarpic plants was very low.     

EFFECTS OF SALINITY ON THE DISTRIBUTION OF CALOGLOSSA LEPRIEURII (RHODOPHYTA) IN THE BRISBANE RIVER,AUSTRALIA1

The role of salinity as a factor determining the distribution of two red algal taxa, Caloglossa leprieurii (Mont.) J. Ag. var. leprieurii and Caloglossa leprieurii var. angusta Jao, along the course of the Brisbane River, Queensland, Australia, was investigated. In the field, C. leprieurii var. angusta tolerated a narrower salinity range (mean salinity = 0.0–18.9) than C. leprieurii var. leprieurii (mean salinity = 2.0–33.8) and occupied areas of lower salinity (salinity expressed according to the Practical Salinity Scale of 1978). Both taxa coexisted for a distance of 23 km along the middle reaches of the river. Cell measurements of specimens of both taxa collected along the river showed an increase in cell sizes upstream from the mouth. Results of a reciprocal transplant experiment and growth responses in a series of laboratory culture studies of the two taxa in a range of salinities are presented. These could be correlated with the field distribution of the algae, demonstrating their euryhalinity and the presence of distinct salinity ecotypes.     

RESPONSE TO SALINITY AND HEAT STRESS IN TWO HALOTOLERANT CHLOROPHYTE ALGAE1

Two new isolates of halotolerant chlorophyte algae from the Salt Plains National Wildlife Refuge in Oklahoma, USA, tentatively identified as Dunaliella sp. Teodoresco and Nannochloris sp. Naumann, were characterized with respect to interaction between growth salinity and short‐term heat tolerance. Cells were cultured at 23–25° C over a wide range of salinity. In both species, salinity alone had little effect on maximum photochemical yield (measured by pulse modulated fluorescence) and integrity of the light harvesting system (77 K fluorescence emission spectra). In contrast, Nannochloris exhibited decreasing growth rate (μ), light‐saturated photosynthetic capacity (P^cell_max), respiration (R_d), light‐harvesting efficiency (α^cell), and chl content with increasing salinity. Cultures were heated for 2 h near their upper temperature limits (41.5° C for Dunaliella and 45° C for Nannochloris grown at 50 psu). Dunaliella was progressively more heat‐tolerant with increasing salinity. Photochemical yield of cells at 100 and 50 psu was inhibited by about 15% and 40%, respectively, and largely recovered within 30 min after return to 23° C. Thermal inhibition of photochemical yield in Nannochloris was about 45% at both 50 and 100 psu, but recovery was slower at 100 psu. At 20 psu, both species were almost 90% inhibited by high temperature and required more than a day to recover. In both species, 2 h of heating increased the PSI:PSII fluorescence emission ratio (714:690 nm) at all salinities. This ratio largely recovered within 24 h in Dunaliella at 50 and 100 psu and partially recovered in Nannochloris at 100 psu, but cells of both species heated at 20 psu were chlorotic the next day.     

FLUORESCENCE INDUCTION AND PHOTOSYNTHETIC RESPONSES OF ARCTIC ICE ALGAE TO SAMPLE TREATMENT AND SALINITY1

The measurement of Photosynthetic rates of algae growing on the undersurface of 1. 7 m thick ice in the Canadian Arctic (Resolute Passage. N.W.T.) presents several problems. During the preparation of samples for physiological measurements, the ice algae may he exposed to salinity and temperature shocks. Fluorescence induction (the rise in in vivo Chl a fluorescence intensity during a period of millineconds) and photosynthesis-irradiance (PI) experiments examined the potential effects of salinity and temperature on the physiology of ice algae. Experimental suspensions were routinely prepared by scraping one part ire crystals (11–14%₀ salinity) and attached algae from the bottom ice into four parts filtered seawater (32%₀ salinity). giving a final salinity of 28–31%₀. Post-dilution of melted ice scrapings with seawater suppressed photosynthetic ¹⁴C-fixation and decreased A_DCMU (the area above the fluorescence induction curve measured in the presence of the inhibitor DCMC: an estimate of photosynthetic capacity) by a factor of 3–16. due to the low salinity of the melted ice scrapings. Fluorescence induction and PI experiments showed that the ice algae had a salinity optimum near 30%₀, close to the ambient seawater salinity, Experiments in which the Chl a concentration was manipulated showed that A_DCMU, P^a_m (Chl a-normalized rate of photosynthesis at light saturation), and a (photosynthetic efficiency) declined with increasing Chl a concentration. Ice algae tolerated heating (l.5°C-min^-1) up to 17° C, above which A_DCMU’decreased with sample temperature.     

DISTRIBUTION AND SYSTEMATICS OF FRESHWATER CERAMIALES (RHODOPHYTA) IN NORTH AMERICA1

Twenty-five freshwater populations of Ceramiales were collected in North America, 24 of which were from the tropical rainforest region of Central America and the Caribbean. The streams tended to be moderate in mean current velocity (X?= 23.3 cm·S^?1) and maximum width (X?= 6.3 m) but high in temperature (X?= 23.1°C), pH (X?= 7.9), and specific conductance (X?= 320 μS·cm^?1). Three Bostrychia species were restricted to the Caribbean islands: B. moritziana (Sonder ex Kütz.) J. Ag. (syn. B. cornigera Mont. and B. radicans f. moliforme Post), with ecorticate indeterminate axes, monosiphonous ultimate branches, and cladohaptera; B. radicans (Mont.) Mont. (syn. B. leprieurii Mont and B. rivularis Harv.), with ecorticate and polysiphonous axes throughout and cladophaptera; and B. tenella (Lamour.) J. Ag., with corticate indeterminate axes, monosiphonous ultimate branches, and peripherohaptera. Ballia prieurii Kütz. was found in Belize and Costa Rica and was characterized by rebranched determinate laterals, opposite branching, and long apical cells (X?= 61 μm) and axial cells (X?= 43 μm). Caloglossa leprieurii (Mont.) J. Ag. was localized in Puerto Rico while. C. ogasawaerensis Okam. was collected only in Costa Rica. The two species were separated by site of branching (midrib vs. margin) and blade width (X?= 384 vs. 861 μm). Polysiphonia subtilissima Mont. from Florida and Jamaica had four pericentral cells, no cortication, rhizoids arising from pericentral cells, and branches initiated at trichoblast scars.     

SEASONAL PRODUCTIVITY OF TWO RED ALGAE IN A CENTRAL CALIFORNIA KELP FOREST1

The in situ productivity of Botryocladia pseudodichotoma (Farl.) Kyl. and Rhodymenia californica var. californica Kyl., two common understory macrophytes in Macrocystis pyrifera (L.) C. Ag. forests, was determined once per month for one year. Gross productivity for B. pseudodichotoma was highest in October (1.23 mgC · g dry wt.^?1· h^?1), but rates were generally greater in spring and lower in summer. Respiration was variable throughout the year, especially in proportion to gross productivity. Gross productivity for R. californica var. californica was also highest in October (4.62 mgC · g dry wt.^?1· h^?1), and lowest in summer. Respiration was highly variable throughout the year. Deep (11 m) populations o/B. pseudodichotoma had 50% higher productivity than shallow (3 m) populations when incubated in shallow water, and 45% higher productivity when incubated in deep water. Populations of B. pseudodichotoma growing in shade at 3 m had 77% higher productivity than populations growing in sun at the same depth when incubated in a sun exposed location at 3 m. Respiration of the shade-adapted plants was only one-half that of the sun-adapted plants. In comparison with similar studies in other sub-tidal communities, net productivity of these two understory red algae is somewhat lower. Lack of strong seasonal productivity patterns and the highly variable underwater light regime suggests that understory algae may be adapted for rapid growth during short periods of high light, regardless of the time of year.     

THE EVOLUTION OF PARASITES FROM THEIR HOSTS: A CASE STUDY IN THE PARASITIC RED ALGAE

Morphological similarities of many parasites and their hosts have led to speculation that some groups of plant, animal, fungal, and algal parasites may have evolved directly from their hosts. These parasites, which have been termed adelphoparasites in the botanical literature, and more recently, agastoparasites in the insect literature, may evolve monophyletically from one host and radiate secondarily to other hosts or, these parasites may arise polyphyletically, each arising from its own host. In this study we compare the internal transcribed spacer regions of the nuclear ribosomal repeats of species and formae specialis (host races) included in the red algal parasite genus Asterocolax with its hosts, which all belong to the Phycodrys group of the Delesseriaceae and with closely related nonhost taxa of the Delesseriaceae. These analyses reveal that species of Asterocolax have evolved polyphyletically. Asterocolax erythroglossi from the North Atlantic host Erythroglossum laciniatum appears to have evolved from its host, whereas taxa included in the north Pacific species Asterocolax gardneri have had two independent origins. Asterocolax gardneri from the host Polyneura latissima probably arose directly from this host. In contrast, all other A. gardneri formae specialis appear to have originated from either Phycodrys setchellii or P. isabelliae and radiated secondarily onto other closely related taxa of the Phycodrys group, including Nienburgia andersoniana and Anisocladella pacifica. Gamete crossing experiments confirm that A. gardneri from each host is genetically isolated from both its host, and from other A. gardneri and their hosts. Cross-infection experiments reveal that A. gardneri develops normally only on its natural host, although some abberrant growth may occur on alternate hosts. The ability of red algal parasites to radiate secondarily to other red algal taxa, where they may become isolated genetically and speciate, suggests that this process of speciation is not a “genetic dead end” but one that may give rise to related clusters of parasite species.     

NUTRITIONAL STUDIES OF TWO RED ALGAE. II. KINETICS OF AMMONIUM AND NITRATE UPTAKE1, 2

Similar NH₄₊ and NO₃^?.uptake kinetic patterns were observed in Neoagardhiella baileyi (Harvey ex Kiitzing) Wyinne & Taylor and Gracilaria foliifera (Forssk?l) Borgesen. NO₃^? was taken up in a rate-sturating fashion described by the Michaelis-Menten equation. NH₄₊ uptake was multicomponent: a saturable component was accompanied by a diffusive or a high K component showing no evidence of saturation (at ≤50 μM [NH₄₊]). Nitrogen starved plantsi(C/N atom ratios > ca. 10) showed higher transient rates of NH₄₊ uptake at a given concentration than plants not N-Iimited. Only plants with high N content exhibited diel changes inNH₄₊ uptake rates, and showed transient rates of NH₄₊ accumulation which did not greatly exceed the capacity to incorporate N in steady-state growth. NH₄₊ was preferred over NO_3?even in plants preconditioned on NO_3?as the sole N. source, NO_3? uptake was suppressed at 5μM [NH₄₊], but simultaneous uptake occurred at unsurpressed rates at lower concentrations. Potential for N accumulation was greater via NH₄₊uptake than via NO_3?uptake. Changing capacity for NH₄₊ uptake with N content appears to be a mechanism whereby excessive accumulation of N was avoided by N-.satiated plants but a large accumulation was possible for N-depleted plants.     

POPULATION STRUCTURE AND PHYSIOLOGICAL DIFFERENTIATION OF HAPLOTYPES OF CALOGLOSSA LEPRIEURII (RHODOPHYTA) IN A MANGROVE INTERTIDAL ZONE

Zonation of macroalgae in the intertidal zone has been well documented. However, studies of zonation of macroalgae have predominantly examined the distribution of different species rather than the distribution of variants within a species. This study investigated the spatial variation of plastid haplotypes of the mangrove red alga Caloglossa leprieurii (Montagne) J. Agardh at a site in eastern Australia and tests for physiological differences (growth, photosynthesis) between those haplotypes. RUBISCO spacer plastid haplotypes were scored using single-stranded comformational polymorphism, and the population structure at two sites was examined using a nested sampling design comparing between sites, among transects within sites, and among quadrats within transects. Growth rates at various salinities and light intensities and the photosynthesis–irradiance curves of the three main haplotypes were compared. The two sites showed a high degree of genetic differentiation across a short distance, suggesting limited gene flow. The distribution of haplotypes was patchy and did not reflect a zonation pattern along the intertidal gradient. The three haplotypes were physiologically differentiated with haplotype A, with a lower growth rate and a lower photosynthetic efficiency at higher light intensities. There is some evidence of physiological differentiation between life history phases in C. leprieurii with sporophytes having a higher growth rate than females under most conditions. Our results suggest a correlation between our culture results and our population data. Haplotypes (haplotype A) and life history phases (gametophytes) with lower performance (growth and photosynthetic efficiency) under our culture conditions were correlated with a minor representation in the field. This is the first study to integrate population-level data with physiological parameters toward an understanding of the distribution and relative abundance of red algal genetic variants.     

THE EVOLUTION OF PARASITISM IN RED ALGAE: CELLULAR INTERACTIONS OF ADELPHOPARASITES AND THEIR HOSTS1

In the initial stages of cell–cell interactions (spore germination and host penetration), the adelphoparasites Gardneriella tuberifera Kyl. and Gracilariophila oryzoides Setch. & Wilson form infection rhizoids that fuse directly with underlying host epidermal or cortical cells. In so doing, parasite nuclei and other organelles enter the cytoplasm of the host. The resulting heterokaryon may fuse with adjacent host cells either directly, via secondary pit connections, or by the dissolution or dislodgment of pit plugs from existing pit connections. The cell fusion events result in a heterokaryotic syncytium in which parasite nuclei replicate. In Gardneriella, formation of the syncytium induces surrounding host tissues to divide to form a photosynthetic callus. The internalized syncytium forms conjunctor and rhizoidal cells that fuse with host callus, eventually transforming the host callus into cells containing parasite nuclei. Gracilariophila does not induce surrounding host tissue to divide. Rather, division of the initial heterokaryotic tissue gives rise to the colorless mantle that protrudes from the host and forms reproductive structures. The heterokaryotic tissue also fuses with underlying host cells, thereby spreading parasite nuclei throughout adjacent host cells. In both these adelphoparasites, transformation of host cells by parasite nuclear invasion results in plastid dedifferentiation, an increase in mitochondria, autolysis of organelles, and accumulation of large amounts of floridean starch. The development and physiology of these parasites is similar to normal post-fertilization processes in the hosts that give rise to carposporophytes and suggests that these adelphoparasites may have originated from perturbations of developmental pathways involved in their host's post-fertilization development.     

A QUALITATIVE AND QUANTITATIVE STUDY OF PLASTOQUINONE A IN TWO THERMOPHILIC BLUE-GREEN ALGAE1

The thermophilic blue-green alga Synechococcus lividus strain Y52 was shown to have plastoquinone (PQ) types A, B, and C. The values PQA per cell and chlorophyll a per cell are presented with the changes in the ratio of PQA to chlorophyll a for cells grown at different light intensities.     

THE UTILITY OF PROTEOMICS IN ALGAL TAXONOMY: BOSTRYCHIA RADICANS/B. MORITZIANA (RHODOMELACEAE,RHODOPHYTA) AS A MODEL STUDY1

A comparison of the proteome of eight genetically well‐characterized isolates of the Bostrychia radicans (Mont.) Mont./B. moritziana (Sond. ex Kütz.) J. Agardh species complex was undertaken to establish if genetic relationships among them can be determined using proteome data. Genetic distances were calculated on the basis of common and distinct spots in two‐dimensional gel electrophoresis (2‐DE). Proteomes of the male and female plants of each population were compared to analyze the range of genetic difference within an isolate. Haploid male and female plants of the same species had 3.7%–7.1% sex‐specific proteins. The degree of similarity of the proteome was consistent with previous DNA sequence data and sexual compatibility studies between the isolates. Two sexually compatible isolates from Venezuela showed a pair‐wise distance ranging from 0.14 to 0.21. The isolates from Mexico and Venezuela, which were partially compatible, showed a maximum pair‐wise distance of 0.26. A high level of genetic difference was found among isolates that were sexually incompatible. The isolate from Brazil was reproductively isolated from the Mexico and Venezuela isolates and showed a maximum pair‐wise distance of 0.65 and 0.58, respectively. Comparative proteomics may be helpful for studying genetic distances among algal samples, if intraisolate variation (gene expression) can be minimized or tested.     

PHOTOSYNTHETIC AND GROWTH RESPONSES TO SALINITY IN A MARINE ISOLATE OF NANNOCHLORIS BACILLARIS (CHLOROPHYCEAE)1

A marine unicellular alga, Nannochloris bacillaris Naumann, was studied with respect to growth, viability and photosynthesis during the steady-state and also subsequent to changes in the concentration of artificial seawater medium. Cells grew exponentially over the range of 2% to 300% artificial seawater, but more rapidly at lower salinities. In contrast to growth, photosynthesis as measured by both oxygen evolution and bicarbonate photoassimilation was not obviously inhibited for cells adapted within the range of 7% to 200% artificial seawater. In 300% artificial seawater, photosynthesis, especially bicarbonate photoassimilation, was inhibited. Osmotic shocks caused by transferring cells from 200% to 7% artificial seawater had little if any effect on growth, viability or photosynthesis. However, equal shocks in the upward direction (from 7% to 200% artificial seawater) caused long lag phases in growth, totally inhibited photosynthesis and very often led to cell death. Intermediate upward shocks were less deleterious, but did result in lags in growth.     

PHYSIOLOGICAL ECOTYPES IN THE MARINE ALGA BOSTRYCHIA RADICANS (CERAMIALES,RHODOPHYTA) FROM THE EAST COAST OF THE U.S.A1

The comparative ecophysiology of nine culture isolates of the eulittoral red alga Bostrychia radicans (Montagne) Montague collected at sites from seven states along the east coast of the U.S.A. was investigated. The growth response in relation to different salinity and light conditions as well as photosynthesis-irradiance curves were studied. In addition, the effect of salt treatment on the content of the isomeric polyols d -sorbitol and d -dulcitol was also studied. All isolates grew between salinities of 5.3 and 70 ppt but with quite different optima and maxima. The isolates were all adapted to low light levels, i.e. growth was already recorded at 2.5 μmol photons·m^?2·s^?1, and growth rates peaked between 40 and 60 μmol photons·m^?2·s_-1. These low-light requirements were also reflected by the photosynthesis-irradiance curves: all plants had low light compensation points (2.5–9.7 μmol photons ·m^?2·^?1) and low photon fluence rates for initial saturation of photosynthesis (38.1–84.7 μmol photons·m^?2·s^?1, indicating that these isolates are “shade-adapted.” Isolates from Florida and Georgia synthesized and accumulated both the osmolytes d -sorbitol and d -dulcitol in increasing salinities, whereas only d -sorbitol was present in plants from North Carolina north to Connecticut. d -sorbitol was always strongly involved in osmotic acclimation. In various isolates from the same location in South Carolina, both polyol patterns were found, i.e. d -sorbitol plus d -dulcitol and d -sorbitol only. All data indicate that B. radicans exhibits a broad salinity tolerance and a low-light preference, which explain the successful colonization of this alga on various intertidal and shaded substrates. The data also clearly indicate intraspecific differences among the nine isolates, which is interpreted as development of different physiological ecotypes.     

GROWTH OF COLPOMENIA PEREGRINA (PHAEOPHYCEAE) IN CULTURE: EFFECTS OF SALINITY,TEMPERATURE AND DAYLENGTH1

Increases in size of Colpomenia peregrina (Sauv.) Hamel microthalli were determined at six different combinations of salinity and temperature under laboratory conditions. Microthalli grown at low salinity (15%) did not have a growth rate significantly different from microthalli grown at high salinity (30%). However, more macrothalli were produced in higher salinity media. Fewer macrothalli were produced at lower temperatures. Growth of C. peregrina microthalli was also determined at six different combinations of daylength and temperature. Microthalli under 15:9 h (LD cycle) did not have a growth rate significantly different from microthalli under 9:15 h LD. However, more macrothalli were produced under long day conditions. Of the three different temperatures utilized (5, 13 and 20° C) only 5° C produced significantly different growth rates. Low temperature reduced growth to such an extent that macrothalli of a size that could be recognized in the field took approximately two months to produce in culture. These results may explain the seasonal presence/absence of the delophycean phase of C. peregrina in the field. Zoospore survivorship and macrothallus production of C. peregrina in culture indicated that both PES and an artificial medium were suitable for the laboratory cultivation of this plant.     

THE EVOLUTION OF PARASITISM IN THE RED ALGAE: MOLECULAR COMPARISONS OF ADELPHOPARASITES AND THEIR HOSTS1

In several groups of parasites including insect, flowering plant, fungal, and red algal parasites, morphological similarities of the parasites and their specific hosts have led to hypotheses that these parasites evolved from their hosts. But these conclusions have been criticized because the morphological features shared by parasite and host may be the result of convergent evolution. In this study, we examine the hypothesis, originally put forth by Setchell, that adelphoparasitic red algae, that is, parasitic red algae that are morphologically very similar to their hosts, evolved from their specific red algal hosts. Rather than comparing morphological features of parasites and hosts, small-subunit 18S nuclear ribosomal DNA and the internal transcribed spacer regions (ITSs) of the nuclear ribosomal repeat are compared for five parasites, their hosts, and related nonhosts from four red algal orders. These comparisons reveal that each of these adelphoparasites has evolved either directly from the host on which it is currently found, or it evolved from some other taxon that is closely related to the modern host. The parasites Gardneriella tuberifera, Rhodymeniocolax botryoides, and probably Gracilariophila oryzoides evolved from their respective hosts Sarcodiotheca gaudichaudii, Rhodymenia pacifica, and Gracilariopsis lemaneiformis, respectively. The parasite Faucheocolax attenuata evolved from either Fauchea laciniata or Fauchea fryeana and subsequently radiated onto the other host species. Presently this parasite is found on both hosts. Lastly, some parasitic genera such as Plocamiocolax are polyphyletic in their origins. A species of Plocamiocolax from an Antarctic Plocamium cartilagineum appears to have evolved from its host whereas the common Plocamiocolax pulvinata that occurs along the west coast of North America likely evolved from Plocamium violaceum and radiated secondarily onto its present day host, Plocamium cartilagineum.     

DISTRIBUTION AND SALINITY ADAPTATIONS OF BANGIA ATROPURPUREA (RHODOPHYTA), A PUTATIVE MIGRANT INTO THE LAURENTIAN GREAT LAKES1

In a survey of the distribution of Bangia atropurpurea (Roth) Ag. along the north and east shorelines of the Laurentian Great Lakes, it was observed that this species was concentrated in the lower lakes. Asexual reproduction by monospore formation was the only form of reproduction in these populations. First generation germlings derived from these spores grew in a wide range of salinities from 1 to 26‰, but the rate was inversely proportional to salinity. In addition, acclimation of parent plants to freshwater or marine media prior to sporulation affected growth rates of first generation germlings placed into a series of salinities. By the second and third generation, germlings with a lineage of seawater showed a preference for the higher salinities, 19 and 26‰ Plants collected in Lake Ontario exhibited no decline in photosynthetic rate as salinity was raised by 13‰ for 15 min. At 26‰ the rate was reduced by half and thylakoids were disrupted in the region of the pyrenoid. On the other hand, third generation plants with a history of seawater attained maximum photosynthetic rates at 26‰ and contained a normal thylakoid organization. Three chromosomes were observed in these plants, which agrees with some of the previous findings for marine Bangia. Origins and taxonomic status of Bangia growing In the Great Lakes are discussed in light of these findings.     

INTERACTIVE EFFECTS OF SALINITY AND TEMPERATURE ON PLANOZYGOTE AND CYST FORMATION OF ALEXANDRIUM MINUTUM (DINOPHYCEAE) IN CULTURE1

The factors regulating dinoflagellate life‐cycle transitions are poorly understood. However, their identification is essential to unravel the causes promoting the outbreaks of harmful algal blooms (HABs) because these blooms are often associated with the formation and germination of sexual cysts. Nevertheless, there is a lack of knowledge on the factors regulating planozygote‐cyst transitions in dinoflagellates due to the difficulties of differentiating planozygotes from vegetative stages. In the present study, two different approaches were used to clarify the relevance of environmental factors on planozygote and cyst formation of the toxic dinoflagellate Alexandrium minutum Halim. First, the effects of changes in initial phosphate (P) and nitrate (N) concentrations in the medium on the percentage of planozygotes formed were examined using flow cytometry. Second, two factorial designs were used to determine how salinity (S), temperature (T), and the density of the initial cell inoculum (I) affect planozygote and resting‐cyst formation. These experiments led to the following conclusions: 1. Low P/N ratios seem to induce gamete expression because the percentage of planozygotes recorded in the absence of added phosphate (‐P) was significantly higher than that obtained in the absence of added nitrogen (‐N), or when the concentrations of both nitrogen and phosphate were 20 times lower (N/20 + P/20). 2. Salinity (S) and temperature (T) strongly affected both planozygote and cyst formation, as sexuality in the population increased significantly as salinity decreased and temperatures increased. S, T combinations that resulted in no significant cyst formation were, however, favorable for vegetative growth, ruling out the possibility of negative effects on cell physiology. 3. The initial cell density is thought to be important for sexual cyst formation by determining the chances of gamete contact. However, the inoculum concentrations tested did not explain either planozygote formation or the appearance of resting cysts.     

HABITAT MATTERS FOR INORGANIC CARBON ACQUISITION IN 38 SPECIES OF RED MACROALGAE (RHODOPHYTA) FROM PUGET SOUND,WASHINGTON, USA1

Measurements of pH drift were used to assess the ability of 38 red algal seaweeds to use bicarbonate and to deplete the dissolved inorganic carbon pool (DIC) from seawater medium. Subtidal algae were typically restricted to the use of DIC in the form of dissolved CO₂, reducing the initial DIC by only 9%. Intertidal species used both dissolved CO₂ and bicarbonate and reduced initial DIC by as much as 70%. DIC reductions and pH compensation points for the intertidal species tested were strongly correlated with their vertical zonation on the rocky shoreline (analysis of variance). DIC acquisition efficiency increased with tidal height, but species from the upper edge of the intertidal demonstrated a reversal of this trend. This general pattern associated with tidal height was observed not only among intertidal red algae in general, but also among four species of the genus Porphyra (P. torta V. Krishnamurthy, P. papenfussii Krishnamurthy, P. perforata J. Agardh, P. fucicola Krishnamurthy) and among four populations of the broadly distributed species Mastocarpus papillatus (C. Agardh). The Mastocarpus observations suggest either that individuals of this species may be able to express alternate strategies for carbon acquisition or that intertidal height may select for survivorship of genotypes with different carbon acquisition strategies. Taken together, these data suggest that the carbon acquisition strategy of intertidal red algae may be an important physiological set of adaptations that is under active evolutionary selection. These physiological differences were not related to phylogeny, tested as membership in red algal families and orders.     

PRIMARY PRODUCTION OF CRUSTOSE CORALLINE RED ALGAE IN A HIGH ARCTIC FJORD1

Crustose coralline algae occupied ～1%–2% (occasionally up to 7%) of the sea floor within their depth range of 15–50 m, and they were the dominant encrusting organisms and macroalgae beyond 20 m depth in Young Sound, NE Greenland. In the laboratory, oxygen microelectrodes were used to measure net photosynthesis (P) versus downwelling irradiance (E_d) and season for the two dominant corallines [Phymatolithon foecundum (Kjellman) Düwel et Wegeberg 1996 and Phymatolithon tenue (Rosenvinge) Düwel et Wegeberg 1996] representing> 90% of coralline cover. Differences in P‐E_d curves between the two species, the ice‐covered and open‐water seasons, or between specimens from 17 and 36 m depth were insignificant. The corallines were low light adapted, with compensation irradiances (E_c) averaging 0.7–1.8 μmol photons·m ^{? 2}·s ^{? 1} and light adaptation (E_k) indices averaging 7–17 μmol photons·m ^{? 2}·s ^{? 1}. Slight photoinhibition was evident in most plants at irradiances up to 160 μmol photons·m ^{? 2}·s ^{? 1}. Photosynthetic capacity (P_m) was low, averaging 43–67 mmol O₂·m ^{? 2} thallus·d ^{? 1} (～250–400 g C·m ^{? 2} thallus·yr ^{? 1}). Dark respiration rates averaged ～5 mmol O₂·m ^{? 2} thallus·d ^{? 1}. In ice covered periods, E_d at 20 m depth averaged ～1 μmol photons·m ^{? 2}·s ^{? 1}, with daily maxima of 2–3 μmol photons·m ^{? 2}·s ^{? 1}. During the open water season, E_d at 20 m depth averaged ～7 μmol photons·m ^{? 2}·s ^{? 1} with daily maxima of ～30 μmol photons·m ^{? 2}·s ^{? 1}. Significant net primary production of corallines was apparently limited to the 2–3 months with open water, and the small contribution of corallines to primary production seems due to low P_m values, low in situ irradiance, and their relatively low abundance in Young Sound.