摘要:

ABSTRACTThe kinetics of phosphate transport bySynechococcus leopoliensis(Racih.) Komarek was investigated. Deviations from Michaelis‐Menten kinetics were observed at law concentrations of phosphate and the deviations were consistent with diffusion limitation of transport. Activation energy analysis of the transport process at two concentrations, one at carrier saturation and the other at zero added phosphate yielded activation energies of 11.9 and 5.6 kcal/mole respectively at 25° C. The first is consistent with an enzyme limited process and the second with diffusion limitation through the unstirred lay

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00177.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThe non‐photosynthetic, phagotrophic dinoflagellate,Gymnodinium fungiformeAnissimova is attracted to a variety of amino acids and other organic compounds. Glycine, taurine and serine attracted the dinoflagellates at a threshold detection level of 10−8M fallowed by dextrose (10−7M) and alanine, proline and threonine (10−6M). Glycine, taurine and alanine are three of the most abundant free amino acids found in invertebrates and protozoa which are major food sources of this dinoflagellate. Three additional species of cultured heterotrophic dinoflagellates were exposed to the water soluble fraction of a shrimp extract known to attractG. fungiforme.All three species responded to the extract, but one species,Oxyrrhis marina, did so only after changing its food source. It is suggested that chemosensory behavior may be suppressed or expressed depending on culture con

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00181.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTChironomid retreats, constructed out of sand grains upon submerged wood debris, increase the surface area available for diatom colonization. The three dimensional substratum afforded by chironomid tubes supports up to twelve times the diatom biavolume found upon adjacent, unmodified substratum in a northern Michigan stream. Diatom enumeration within scrapings from small defined areas on artificial substrata, combined with examination of intact natural substrata through scanning electron microscopy (SEM), reveals distinct, microdistribution patterns. The larval retreats of two major taxa of tube‐dwelling chironomid's(Micropsectrasp. andPseudodiamesacf.pertinaxGarrett) display significantly different diatom communities relative to adjacent masonite substratum. Substratum without chironomid tubes is primarily colonized byAchnanthes minutissimaKütz. andCocconeis placentulaEhr., exhibiting the lowest species diversity of microhabitats examined. The diatom flora upon sand tubes ofMicropsectrasp. is dominated byOpephora martyiHerib., as is the flora of sand grains collected from the stream sediment load. These two micro‐habitats exhibit a high community similarity (SIMI). The SIMI index also suggests that the flora ofP. pertinaxtubes is highly similar to that of sand grains. Diversity, however, is almost three times greater onP. pertinaxtubes and SEM observations reveal that this microhabitat is characterized by a more spatially complex flora; NitzschiaandNaviculaspp. dominate the upperstory, andO. martyiis located on underlying sand grains. Results indicate that tube‐building chironomids in Carp Creek affect diatom microdistribution by: (1) stabilizing sand grains and associated flora within their retreats, (2) providing a ‘refugium’ for upperstory diatom taxa from the mayfly grazer,Baetis vagansMcDunnough (Insecta: Ephemeroptera), and (3) through local nutrient

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00185.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTBuoyancy of the gas‐vacuolate algaAnabaena flosaquaeBrébisson was measured under various levels of light, NH4+, and CO2. At high irradiance (50 μE · m−2·−1) the alga was non‐buoyant regardless of the availability of CO2and NH4+. At low irradiance (≤10 μE · m−2· s−1) buoyancy was controlled by the availability of NH4+and CO2. When NH4+was abundant, algal buoyancy was high over a wide range of CO2concentrations. In the absence of NH4+, algal buoyancy was reduced at high CO2concentrations, however as the CO2concentration declined below about 5 μmol · L−1, algal buoyancy increased. These results help explain why gas vacuolate, nitrogen‐fixing blue‐green algae often form surfa

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00194.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTSexual reproduction and encystment of the marine dinoflagellateGyrodinium uncatenumHulburt were induced in nitrogen and phosphorus‐limited batch cultures. Sexuality did not occur under nutrient‐replete conditions even when growth rate was reduced by non‐optimal temperatures. Growth was optimal over a broader temperature range than encystment and virtually no cysts were produced at some low and high temperatures where growth occurred.Most cells initiated sexuality as intracellular pools of each limiting nutrient reached minimum or subsistence levels as much as four days after extracellular nutrients were exhausted. High nitrogen cell quotas during the phosphorus experiment indicate that sexuality was induced by a shortage of phosphorus and not by an indirect effect on nitrogen uptake.Total cyst yield corresponded to successful encystment of 9–13% of the motile populations, yet 60–85% of the plateau‐phase motile cells were planozygotes (swimming zygotes formed from fusing gametes). Batch culture studies monitoring total cyst yield may thus seriously underestimate the extent of sexuality. More importantly, the number of cysts produced in a dinoflagellate population may be significantly reduced by environmental factors acting on the cells after sexual induction

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00200.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTUsing scanning electron and light, microscopy, several hundred specimens ofCampylostylus normanianus(Grev.) Gerloff,Licmophora abbreviataAgardh,L. gracilisvar.anglica(Kütz) Per. et Per., andL. flabellata(Carm.) Agardh were examined to elucidate their valve morphology. These species were found to be heterovalvar with respect to the presence of the labiate process in the basal apices of the cell, although one was always present at the head pole of each valve. This form of heterovalvar may be one basis for partitioning the large and variable family Diatomaceae. Because of the similar valve morphologies exhibited byC. normanianusandLicmophoraspecies examined, it is recommended thatCampylostylus normanianusbe placed in the older genusLicmophora, asL. normaniana(Grev.) Wahrer

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00206.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTCadmium and copper inhibition of nutrient uptake by the green algaScenedesmus quadricaudais highly pH dependent in an inorganic medium; both metals are less toxic at low pH. The alga was grown in chemostats with both N and P approaching limiting levels; it was then possible to study metal toxicity to the nitrate, ammonium, and phosphate uptake systems of algae in an identical physiological state. When the logarithm of the Cd concentration causing 25% inhibition of nitrate, ammonium, and phosphate uptake was regressed against pH almost perfect linear relationships were obtained. This was also true at the 50% inhibition level, except for a smaller than predicted increase in Cd toxicity to ammonium uptake at pH 8, which may be due to the beginning of Cd precipitation at this pH. Cu2+toxicity was linearly related to pH for ammonium and phosphate uptake and although, its toxicity for nitrate uptake also increased with pH, the increase was not perfectly linear. The toxicity of total Cu showed no linear relationship to pH. Cd2+and Cu2+toxicity increased by up to four orders of magnitude from pH 5 to 8. Competition between free metal and hydrogen ions for uptake sites on the cell surface is suggested as a mechanism increasing the toxicity of free metal, ions as the hydrogen ion content decreases (i.e. at higher pH).

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00217.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTNostoc parmelioidescolonies housing dipteran larvae(Cricotopus)had higher rates of weight specific photosynthesis than colonies without the larvae. A change in colony shape, which allowed the alga to be exposed to higher light intensities, occurred, in the presence of the larvae. This change in morphology together with potential nutrient additions by the larvae and other effects may have caused the increase in photosynthetic rates.Nostoccolonies were typically found in open areas of small streams in western Oregon mountains where the ability to respond to high light would be advantageous in supporting the metabolically expensive process of nitrogen fixation.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00223.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTUlothrix zonata(Weber and Mohr) Kütz. is an unbranched filamentous green alga found in rocky littoral areas of many northern lakes. Field observations of its seasonal and spatial distribution indicated that it should have a low temperature and a high irradiance optimum for net photosynthesis, and at temperatures above 10°C it should show an increasingly unfavorable energy balance. Measurements of net photosynthesis and respiration were made at 56 combinations of light and temperature. Optimum conditions were 5°C and 1100 μE·m−2·s−1at which net photosynthesis was 16.8 mg O2·g−1·h−1. As temperature increased above 5° C optimum irradiance decreased to 125 μE·m−2·s−1at 30°C. Respiration rates increased with both temperature and prior irradiance. Light‐enhanced respiration rates were significantly greater than dark respiration rates following irradiance exposures of 125 μE·m−2·s−1or greater. Polynomials were fitted to the data to generate response surfaces. Polynomial equations represent statistical models which can accurately predict photosynthesis and respiration

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00228.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTIn many lakes in the northern United States and Canada the filamentous green algaUlothrix zonata(Weber and Mohr) Kütz grows abundantly in early spring in shallow waters. Asexual reproduction occurs by formation of quadriflagellate zoospores which disrupt, the integrity of the cells upon release causing the filament to disintegrate. Study of the effects of 100 different combinations of irradiance, temperature and photoperiod revealed that zoospore formation is favored by high temperatures near 20°C, high light levels of 520 μE·m−2·s−1and photoperiods of either short day (8:16 h light‐dark) or long day cycles (16:8 h light‐dark). Zoospore formation is minimal under conditions of low temperature (5°C), low irradiance (32.5 μE·m−2·s−1) and neutral day‐lengths (12:12 h light‐dark). These observations explain the decline inU. zonatabiomass when water temperatures rise above 10° C. The combined effect of rising water temperatures and increasing daylengths causes progressively more filaments to switch from vegetable growth to zoospore production resulting in an i

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00235.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY