ALBERT

Notes: Abstract Blooms of the toxic dinoflagellate Alexandrium tamarense Lebour have been nearly annual features along the coasts of southern Maine, New Hampshire and Massachusetts, USA, since 1972. In 1990 two hypotheses which have been used to explain the initiation of these blooms in the southwestern portion of the Gulf of Maine were tested using historical records of shellfish toxicity, wind, and river flow. The first hypothesis states that the blooms were initiated or advected to shore by wind-driven coastal upwelling. The second states that established blooms were advected from north to south alongshore in a coastally trapped buoyant plume of water. Of the eleven years examined (1979 to 1989), we found seven cases inconsistent with the wind-driven upwelling hypothesis, and only one case (1985) which contradicts the plume-advection hypothesis. 1985 was an unusual year in many respects, and we suggest that some other mechanism was responsible for the toxic outbreaks. In addition, the wind-driven upwelling hypothesis could not explain the observed north-to-south temporal progression of toxicity each year. The plume-advection hypothesis was found to best explain the datails of the timing and spread of shellfish toxicity in Gulf of Maine waters to the south of Penobscot Bay, Maine. These include the variable north-to-south progression with time, the presence of a toxin-free zone south of Cape Ann, Massachusetts, the sporadic nature of toxic outbreaks south of Massachusetts Bay, and the apparently rare occurrence of high toxicity levels well offshore on Nantucket Shoals and Georges Bank.

Notes: Abstract Life cycle changes that allow populations of the toxic dinoflagellate Gonyaulax tamarensis Lebour to inhabit the benthos and the plankton alternately are important factors regulationg the initiation and decline of blooms in restricted embavments. When the dynamics of these estuarine populations were monitored during “bloom” and “non bloom” years, it was shown that: (1) each year, germination of benthie cysts inoculated the overlying waters during the vernal warming period, but a large residual population remained in the sediments throughout the blooms; (2) the resulting planktonic population began growth under suboptimal temperature conditions; (3) the populations developed from this inoculum through asexual reproduction until sexuality (and cyst formation) were induced; (4) encystment was not linked to any obvious environmental cue and occurred under apparently optimal conditions; and (5) an increase in the number of non-mitotic swimming cells (planozygotes, the precursors to dormant cysts) accompanied the rapid decline of the planktonic population. Thus encystment, in combination with hypothesized losses due to advection and grazing, contributed substantiatly to the decline of the vegetative cell population. We conclude that the encystment/excystment cycle temporally restricts the occurrence of the vegetative population and may not be optimized for rapid or sustained vegetative growth and bloom formation in shallow embayments. The factors that distinguish “bloom” from “non-bloom” years thus appear to be operating on the growth of the planktonic population.

Notes: Abstract Relationships among dinoflagellates of the genus Alexandrium (=Protogonyaulax) from Long Island, New England, USA, and northeastern Canada were investigated between 1983 and 1987 using enzyme electrophoresis. A relative lack of heterogeneity among toxic isolates was observed despite large geographic separations of source populations. This observation is in marked contrast to observations on toxic members of this genus from the west coast of Canada and the United States. These different enzyme variability patterns support the proposal that dispersal of toxic strains in the east from a common source has occurred recently, presumably from established populations in northern Maine, USA, or Canada. Non-toxic strains from the study area were only distantly related to toxic isolates, consistent with their different morphology and separate species designations. One non-toxic isolate from a different region, that is conspecific with a number of the toxic strains, was more similar to these isolates than to other non-toxic clones.

Notes: Abstract We examined the mechanisms controlling blooms of the toxic dinoflagellate Alexandrium tamarense Lebour and the concomintant patterns of shellfish toxicity in the southwestern Gulf of Maine, USA. During a series of cruises from 1987 to 1989, hydrographic parameters were measured to elucidate the physical factors affecting the distribution and abundance of dinoflagellates along this coast. In 1988 and 1989 when toxicity was detected in the southern part of this region, A. tamarense cells were apparently transported into the area between Portsmouth, New Hampshire, and Cape Ann, Massachusetts, in a coastally trapped buoyant plume. This plume appears to have been formed by the outflow from the Androscoggin and Kennebec Rivers. Flow rates of these rivers, hydrographic sections, and satellite images led us to conclude that the plume persisted for about a month, and extended alongshore for several hundred kilometers. The distribution of cells followed the position of the plume as it was influenced by wind and topography. When winds were downwelling-favorable (to the southwest), cells were moved alongshore to the south, and were held to the coast; when winds were upwelling-favorable (to the northeast),the plume sometimes separated from the coast, advecting the cells offshore. In 1987 when no plume was present, A. tamarense cells were scarce, and no toxicity was recorded at the southern stations. The alongshore advection of toxic cells within a coastally trapped buoyant plume can explain the details of the temporal and spatial patterns of shellfish toxicity along the coast. We hypothesize that (1) the source of the A. tamarense populations is in the north, possibly associated with the Androscoggin and Kennebec estuaries, that (2) toxicity patterns follow a predictable relationship with river flow volume and timing of flow peaks and that (3) wind stresses directly influence the distribution of low salinity water and the dinoflagellate cells. Local, in situ growth of dinoflagellates can be an important factor initiating toxic dinoflagellate blooms. However, these data demonstrate the significant role of alongshore transport of established populations of A. tamarense in controlling the location and timing of paralytic shellfish poisoning (PSP) outbreaks in May and June along the southwestern coast of the Gulf of Maine.

Notes: Abstract Twenty-eight strains of toxic dinoflagellates in the genusAlexandrium from the northeastern United States and Canada were characterized on the basis of morphology, bioluminescence capacity, mating compatibility, and toxin composition. The distributions of these characters were evaluated in the context of regional patterns of paralytic shellfish poisoning (PSP) and coastal hydrography. Two morphospecies were identified-A. tamarense Lebour andA. fundyense Balech. The two are interspersed geographically though there are areas, such as the Gulf of Maine, where apparently onlyA. fundyense occurs. Southern waters (Cape Cod, Connecticut, and Long Island) have especially diverse populations. The two species are sexually compatible. Virtually all northern isolates are bioluminescent, whereas southern isolates include bioluminescent and non-bioluminescent strains. Cluster analyses, based on high performance liquid chromatography (HPLC) determinations of the suite of toxins produced by each isolate, revealed two and perhaps three distinct groups. One is comprised almost exclusively of northern strains, and the other of southern strains. A Cape Cod cluster may be separable from the southern group. These analyses explain a previously reported north-to-south trend of decreasing toxicity, as the northern isolates produce greater proportions of the more potent toxins than do southern forms. The overall perspective is that the biogeography of toxicAlexandrium spp. in the study region is not that of a single, widespread, homogeneous population, but rather is comprised of several sub-populations, each with its own physiological characteristics and history. Two scenarios are considered with respect to this regional biogeography. The first invokes recent and continuing dispersal of isolates to the south from a center of origin in the north, followed by recombination and strong selection. The second holds that the northern and southern populations diverged from a common ancestor (vicariance), but now represent localized populations with little mixing of genotypes. Neither hypothesis can be completely refuted by the data presented here, though the weight of the evidence favors the latter. The correct scenario may be a combination of both, with recent and continuous speading occuring within the Gulf of Maine and perphaps the Gulf of St. Laerence, but with endemic localized populations persisting without genetic exchange in most southern locations. These data also indicate that although morphological criteria separate toxicAlexandrim isolates from the study region into two morphospecies, these assignments do not coincide with clusterings based on toxin composition or allozyme electrophoresis, and they are further violated by mating results. A revision of taxon designations to the varietal level could be justified.

Notes: Abstract Toxin content (fmol cell−1) and a suite of elemental and macromolecular variables were measured in batch cultures of the dinoflagellatesAlexandrium fundyense, A. tamarense andAlexandrium sp. from the southern New England region, USA. A different perspective was provided by semicontinuous cultures which revealed sustained, steady-state physiological adaptations by cells to N and P limitation. Two types of variability were investigated. In batch culture, changes in nutrient availability with time caused growth stage variability in toxin content, which often peaked in mid-exponential growth. A second type of variability that could be superimposed on growth stage differences is best exemplified by the high toxin content of cells grown at suboptimal temperatures. Calculations of the net rate of toxin production (R tox ; fmol cell−1 d−1) for these different culture treatments and modes made it possible to separate the dynamics of toxin production from cell division. Over a wide range of growth rates, cells produced toxin at rates approximating those needed to replace “losses” to daughter cells during division. The exception to this direct proportionality was with P limitation, which was associated with a dramatic increase in the rate of toxin production as cells stopped dividing due to nutrient limitation in batch culture. Growth stage variability in batch culture thus reflects small imbalances (generally within a factor of two) between the specific rates of toxin production and cell division. N limitation and CO2 depletion both affect pathways involved in toxin synthesis before those needed for cell division; P limitation does the opposite. The patterns of toxin accumulation were the same as for major cellular metabolites or elemental pools. The highest rates of toxin production appear to result from an increased availability of arginine (Arg) within the cell, due to either a lack of competition for this amino acid from pathways involved in cell division or to increased de novo synthesis. There were no significant changes in toxin content with either acclimated growth at elevated salinity, or with short term increases or decreases of salinity. These results demonstrate that toxin production is a complex process which, under some conditions, is closely coupled to growth rate; under other conditions, these processes are completely uncoupled. Explanations for the observed variability probably relate to pool sizes of important metabolites and to the differential response of key biochemical reactions to these pool sizes and to environmental conditions.

Notes: Summary One of the scientific objectives of the Viking Mission to Mars was to accomplish an analysis of water in the Martian regolith. The analytical scheme originally envisioned was severly compromised in the latter stages of the Lander instrument package design. Nevertheless, a crude soil water analysis was accomplished. Samples from each of the two widely separated sites yielded roughly 1 to 3% water by weight when heated successively to several temperatures up to 500°C. A significant portion of this water was released in the 200° to 350°C interval indicating the presence of mineral hydrates of relatively low thermal stability, a finding in keeping with the low temperatures generally prevailing on Mars. The presence of a duricrust at one of the Lander sites is taken as possible evidence for the presence of hygroscopic minerals on Mars. The demonstrated presence of atmospheric water vapor and thermodynamic calculations lead to the belief that adsorbed water could provide a relatively favorable environment for endolithic organisms on Mars similar to types recently discovered in the dry antarctic deserts.

Notes: [Auszug] Records of temperature during the past two millennia provide clues to the natural variation we might expect in the future. They also support attempts to partition recent warming into natural and anthropogenic components, and to measure the sensitivity of climate to greenhouse gases in the ...

Notes: The influence of temperature and relative humidity (r.h.) on the efficacy of glufosinate ammonium was investigated in controlled environment growth chambers using a tolerant species, barley (Hordeum vulgare L. cv. ‘Samson’), and a susceptible species, green foxtail (Setaria viridis (L.) Beauv.). The shoot ammonia concentration and visual injury of plants treated with glufosinate-ammonium doses of 100 and 800 g ha−1 were compared at day/night temperature regimes of 8/5,15/10 and 22/17°C at 60% r.h. The effect of relative humidity levels of 40% and 95% on the shoot ammonia concentration, visual injury and dry weight accumulation of glufosinate-ammonium treated plants was tested at temperature regimes of 15/10 and 22/17°C, with both species treated with 800 g ha−1. In addition, green foxtail treated with 100 g ha−1. was tested at both r.h. levels at 22/17°C. As the temperature de creased, less ammonia was produced in treated green foxtail plants. However, ammonia levels were comparable at all temperature regimes for barley. Lowest temperatures resulted in delayed injury to both species, but only small differences in injury existed among temperature regimes 288 h after spraying. The activity of glufosinate ammonium on both species was significantly de creased by low r.h. For example, when grown at 22/17°C, green foxtail survived the potentially lethal dose of 100 g ha−1 at 40% r.h. and accumulated 70% of the dry weight of control plants, but was killed at 95% r.h. Of the two environmental factors examined, r.h. had the most significant effect on the phytotoxic action of glufosinate-ammonium. L'influence de la température et de I'humidité relative sur I'efficacité du glufosinate-ammonium L'influence de la température et de 1'humidité relative (hr) sur I'efficacité du glufosinate ammonium a étéétudiée en chambre climatique en utilisant une espéce d'orge tolérante (Hor deum vulgare L. cv ‘Samson’) et une espéce sensible la svtaire verte (Setaria viridis L. Beauv).La concentration en ammoniaque des pieds et les dégats visuels des plantes traitérs avec des doses de glufosinate ammonium de 100 et 800 g/ ha−1 ont été comparés pour des régimes de températures jour/nuit de 8/5, 15/10 et 22/17°C à 60% hr. L'effet de taux d'humidité relative de 40 et 95% sur la teneur en ammoniaque des pieds, les dégats visuels et (l'accumulation de matiére séche chez des plantes traitéres au glufosinate ammonium a été testéà des régimes de températures de 15/10 et 22/17°C, pour les 2 espéces traitées à 800 g ha−1. En outre, la sétaire verte traitée à 100 g hr−1 a été testée aux 2 hr à 22/17°C. Quand la température diminue, il y a moins d'ammoniaque produit chez les sétaires vertes trailérs. Cependant les taux d'ammon iaque ont été comparables à toutes les tempéra tures chez 1'orge. Les températures les plus basses ont abouti à un retard de phytotoxicité ches les 2 espéces, mais à peu de différences entre les régimes de températures 288 h après 1'application. L'activité du glufosinate ammon ium chez les deux espèces a été significative ment réduite par des faibles hr. Par exemple cul tivée à 22/17°C, la sétaire verte a survécu à des doses potentiellement léthales de 100 g ha−1à 40% d'hr et a accumulé 70% de la matière sèche des témoins mais a été détruite à 95% d'hr. Sur les 2 facteurs environnementaux étudiés, l'hr a l'effet le plus important sur l'activité phytotoxique du glufosinate ammonium. Einfluβ von Temperatur und relativer Feuchte auf die Wirksamkeit von Glufosinat-ammonium Der Einfluß von Temperatur und relativer Feuchte (rF) auf die Wirksamkeit von Glufosinat-ammonium wurde in Klimakammern anhand einer toleranten Art, der Gersten-Sorte ‘Samson’ (Hordeum vulgare L.), und einer empfindlichen Art, der Grünen Borstenhirse (Setaria viridis (L.) Beauv.), untersucht. Die Ammonium-Konzentration im Sproß und sichtbare Schädigungen der Pflanzen, die mit Dosen von 100 und 800 g ha−1 behandelt worden waren, wurden bei Tag/Nacht-Temperaturen von 8/5, 15/10 und 22/17 °C bei 60% rF verglichen. Die Wirkung von 40 oder 95% rF auf die Ammonium-Konzentrationen im Sproß, sichtbare Pflanzenschädigungen und die Trockenmassebildung wurde bei 15/10 und 22/17°C und bei 800 g ha−1 Glufosinat-ammonium untersucht. Zusätzlich wurde die Grüne Borstenhirse mit 100 g ha−1 behandelt und bei den beiden Feuchtegraden und 22/17 °C untersucht. Mit abnehmender Temperatur bildete die Grüne Borstenhirse weniger Ammonium, dessen Gehalt bei der Gerste jedoch bei allen Temperaturen gleich war. Geringere Temperaturen verzögerten bei beiden Arten die Schädigungen, doch ließen sich 288 h nach der Behandlung nur noch geringe Unterschiede bei den verschiedenen Temperaturen beobachten. Die Wirkung von Glufosinat-ammonium war bei niedriger rF bei beiden Arten signifikant schwächer. Z. B. überlebte die Grüne Borstenhirse die potentiell letale Dosis von 100 g ha−1 bei 22/17 °C und 40% rF und bildete 70% der Trockenmasse von Kontrollpflanzen, wurde jedoch bei 95% rF abgetötet. Die rF war von den beiden untersuchten Umweltfakoren der signkfikantere für die phytotoxische Wirkung des Glufosinat-ammoniums.