Anthony G. Miller

Infrared spectrum of carbon dioxide in aqueous solution

Abstract We have studied the infrared absorption band due to the antisymmetric stretching fundamental, ν 3 , of carbon dioxide in water at 2342.9 cm −1 for 12 CO 2 and 2277.7 cm −1 for 13 CO 2 , from the point of view of structural and analytical chemistry. The position of this band is shifted by only 6 cm −1 from the vapour value, indicating the absence of hydrogen bonding between water molecules and the dissolved carbon dioxide. The ν 3 band has good analytical potential and may be used for the determination of carbon dioxide in water. We have also examined the analytical use of the infrared bands of aqueous carbonate and bicarbonate ions.

Photosynthetic metabolism of cyanate by the cyanobacterium Synechococcus UTEX 625

Intact cells of the unicellular cyanobacterium Synechococcus UTEX 625 degraded exogenously supplied cyanate (as KOCN) to CO2 and NH3 in a light-dependent reaction. NH3 release to the medium was as high as 80 μmol(mgChl)-1h-1 and increased 1.7-fold in the presence of methionine sulfoximine, a glutamine synthetase inhibitor. Cyanate also supporte photosynthetic O2 evolution to a maximum rate of 188 μmol O2(mgChl)-1h-1 at pH 8 and 30°C. Cyanate decomposition in cell-free extracts, measured by mass spectrometry as 13CO2 production from KO13CN, occurred in the soluble enzyme fraction, but not in the thylakoid/carboxysome fraction, and was enhanced by HCO3− and inhibited by the dianion oxalate. CO2, rather, than HCO3−, was a product of cyanate decomposition. The ability to decompose cyanate was not dependent upon pre-exposure of cells to cyanate to induce activity. The collective results indicate that Synechococcus UTEX 625 possesses a constitutive, cytosolic cyanase (EC 4.3.99.1), similar in mechanism to that found in some species of heterotrophic bacteria. The reaction catalyzed was: OCN+HCO3+2H+→2CO2+NH3. In intact cells, the CO2 produced by the action of cyanase on OCN- was either directly fixed by the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, leading to O2 evolution, or leaked into the medium where it was returned to the cell by the active CO2/HCO3− transport systems for fixation. However, leakage of CO2 from air-grown cells was only observed when the active CO2 transport system was inhibited by darkness or the CO2 analogue carbon oxysulfide.

Decline of Canada geese (Branta canadensis) and common goldeneye (Bucephala clangula) associated with a collapse of eelgrass (Zostera marina) in a Nova Scotia estuary

Abstract. Mean numbers of migrant Canada geese (Branta canadensis) in Antigonish Harbour in the southern Gulf of St. Lawrence (Canada) during October to December were similar (approx. 450–500 birds) for the period 1998–2000. Similarly, during this period, geese used two foraging sites. However, in 2001, the average number of birds decreased by half and the primary foraging sites were used only rarely. This coincided with a decline of about 95% in the biomass of roots and rhizomes of eelgrass (Zostera marina) that occurred between October 2000 and 2001. Eelgrass is the principal food of geese in this estuary. In addition, there was a reduction of around 50% in the numbers of common goldeneye (Bucephala clangula), which feed on invertebrates associated with eelgrass. Lower than usual weekly abundances of geese and goldeneye are probably the result of an unusually short residence time in the estuary, rather than a decline in the total number of visiting migrants. We attribute these changes in the distribution and abundance of geese and goldeneyes to the dramatic decline in eelgrass.

Characterization of the non-photochemical quenching of chlorophyll fluorescence that occurs during the active accumulation of inorganic carbon in the cyanobacterium Synechococcus PCC 7942

Previous work has shown that the maximum fluorescence yield from PS 2 of Synechococcus PCC 7942 occurs when the cells are at the CO2 compensation point. The addition of inorganic carbon (Ci), as CO2 or HCO3−, causes a lowering of the fluorescence yield due to both photochemical (qp) and non-photochemical (qN) quenching. In this paper, we characterize the qN that is induced by Ci addition to cells grown at high light intensities (500 μmol photons m−2 s−1). The Ci-induced qN was considerably greater in these cells than in cells grown at low light intensities (50 μmol photons m−2 s−1), when assayed at a white light (WL) intensity of 250 μmol photons m−2 s−1. In high-light grown cells we measured qN values as high as 70%, while in low-light grown cells the qN was about 16%. The qN was relieved when cells regained the CO2 compensation point, when cells were illuminated by supplemental far-red light (FRL) absorbed mainly by PS 1, or when cells were illuminated with increased WL intensities. These characteristics indicate that the qN was not a form of energy quenching (qE). Supplemental FRL illumination caused significant enhancement of photosynthetic O2 evolution that could be correlated with the changes in qp and qN. The increases in qp induced by Ci addition represent increases in the effective quantum yield of PS 2 due to increased levels of oxidized QA. The increase in qN induced by Ci represents a decrease in PS 2 activity related to decreases in the potential quantum yield. The lack of diagnostic changes in the 77 K fluorescence emission spectrum argue against qN being related to classical state transitions, in which the decrease in potential quantum yield of PS 2 is due either to a decrease in absorption cross-section or by increased ‘spill-over’ of excitation energy to PS 1. Both the Ci-induced qp (t0.5<0.5 s) and qN (t0.5≃1.6 s) were rapidly relieved by the addition of DCMU. The two time constants give further support for two separate quenching mechanisms. We have thus characterized a novel form of qN in cyanobacteria, not related to state transitions or energy quenching, which is induced by the addition of Ci to cells at the CO2-compensation point.

Distribution and salinity tolerance of intertidal mosses from Nova Scotian salt marshes

Abstract Five moss species were found in the high intertidal zone of salt marshes in Nova Scotia, eastern Canada. This is the first report of bryophytes from salt marshes from North America. In each of the salt marshes where mosses occurred, one to three moss species occurred in monospecific or mixed species assemblages. Campylium stellatum and Bryum capillare were the most common species, followed by Didymodon rigidulus, Mnium hornum and Amblystegium serpens in decreasing abundance. All mosses were present below the litter line and occurred in association with Juncus arcticus and J. gerardii, although some collections were also made in association with Spartina pectinata and S. patens. The mosses were exposed in situ to seawater of > 20 ppt. In a laboratory experiment, mats of C. stellatum were exposed to a range of salinities (0, 8, 16, 32 ppt); plants survived 24 h of immersion in seawater of 32 ppt followed by four days in which mats were fully saturated with seawater. There was a slight reduction in effective quantum yield of photosystem II (ΦPSII ) in the 32 ppt treatment relative to 0 and 8 ppt. Following four subsequent days of desiccation, the full-seawater- and 16-ppt-treated plants had significant reduction in quantum yield. This experiment is consistent with field observations and shows considerable physiological tolerance to salinity in salt marsh mosses.

Dynamics of the growth, life history transformation and photosynthetic capacity of Oophila amblystomatis (Chlorophyceae), a green algal symbiont associated with embryos of the northeastern yellow spotted salamander Ambystoma maculatum (Amphibia)

The recent discovery that the unicellular green alga Oophila amblystomatis, invades embryonic tissues and cells of the salamander Ambystoma maculatum prompted us to investigate the growth and life history transformations of the algal symbionts in egg capsules. During embryonic development, symbionts were first detected microscopically as a cohesive population of swimming cells in the vicinity of the blastopore around embryonic stage 17. This population of cells grew and at embryonic stage 25, a fraction of the population began to affix to the inside of the egg capsule. Cells then underwent syngamy, lost flagella, and transformed into non-motile cells. We observed a linear increase in the accumulation of such capsule-associated cells from embryonic stage 25 to 40. The population of zoospores did not grow over this period and showed a declining trend between stage 39 and 40. We verified the population growth by measuring relative chlorophyll a content and also measured quantum yield (QY) of photosystem II (PS II) using pulse amplitude modulated (PAM) fluorometry. The population, but not the cell size, of non-motile capsule membrane-bound cells increased modestly during a one-month period after hatching, and continued to contain high levels of chlorophyll a and photosynthetic capacity. We conclude that O. amblystomatis undergoes a life history transition in egg capsules and speculate that many of these symbionts become zygotes, rather than invading the embryo.

Metabolism and ecology of the water mould, Leptomitus lacteus (Oomycota), blooming in winter in a Nova Scotia stream

The water mould Leptomitus lacteus bloomed in a small stream in northern Nova Scotia, Canada, for at least four months from December through March when water temperatures were near 0 °C and the stream was fre- quently ice-covered. The bloom occupied much of the substratum along 1.5 km of stream below the effl uent outfall from a composting facility. A true fungus, Saprochaete saccharophila, was a minor component of the bloom. L. lacteus colonies appeared robust against freezing and regrew quickly after scouring fl oods. L. lacteus preferred rif- fl es and fast-fl owing water, evidently because of a high oxygen requirement. In mid-winter, the standing crop of L. lacteus approached 2.5 kg m -2 fresh mass, or 2000 kg along the whole length of stream. The bloom ended abruptly in April when water temperatures rose above 5 °C. In the laboratory, clumps of L. lacteus demonstrated vigorous oxygen consumption near 0 °C. Oxidative metabolism was largely confi ned to the outer 6 mm of the colonies, interior to which (O2) declined precipitously. Evidence suggests that L. lacteus blooms in winter to take advantage of a rich food source and high (O2) while avoiding competition. Similar blooms of L. lacteus elsewhere may be overlooked because winter weather and ice cover discourage investigations.

Coronilla varia L. (Fabaceae): AN INVADER OF A COASTAL BARRIER BEACH IN NOVA SCOTIA, CANADA

C Coronilla varia L. (crown vetch) is described as an invasive plant on a coastal sand dune system (Mahoneys Beach) in Nova Scotia facing the southern Gulf of St. Lawrence. This is the first time that C. varia has been shown as invasive in Atlantic Canada, and the first time it has been characterized as invasive on coastal sand dunes. Accordingly, colonies of C. varia forming more than 90% of the plant cover occupy 8% of the total dune system and account for 32% of the area in the vegetation zone where C. varia has become abundant. C. varia can achieve high percentage cover, with all of the major dune plants, i.e., Ammophila breviligulata, Lathyrus japonicus, Toxicodendron radicans and Myrica pensylvanica. Where C. varia achieves maximum abundance (i.e., >80% cover and ca. 200 shoots m2), it has seemingly replaced A. breviligulata and L. japonicus. We do not know when C. varia first colonized Mahoneys Beach, but conspicuous colonies were recorded there by 2005, and a colony was found on the adjacent dune system (Dunns Beach) for the first time in 2010. Key Words: Coronilla varia, crown vetch, Fabaceae, invasive species, Nova Scotia, sand dunes