A radiative transfer modeling approach for accurate interpretation of PAM fluorometry experiments in suspended algal cultures

The results of a numerical study on the simulation of pulse amplitude modulated (PAM) fluorometry within dense suspensions of photosynthetic microorganisms are presented. The Monte Carlo method was used to solve the radiative transfer equation in an algae‐filled cuvette, taking into account absorption, anisotropic scattering, and fluorescence, as well as Fresnel reflections at interfaces. This method was used to simulate the transport of excitation and fluorescence light in a common laboratory fluorometer. In this fluorometer, detected fluorescence originates from a multitude of locations within the algal suspension, which can be exposed to very different fluence rates. The fluorescence‐weighted fluence rate is reported, which is the local fluence rate of actinic light, averaged over all locations from which detected fluorescence originated. A methodology is reported for recovering the fluorescence‐weighted fluence rate as a function of the transmittance of measuring light and actinic light through the sample, which are easily measured with common laboratory fluorometers. The fluorescence‐weighted fluence rate can in turn be used as a correction factor for recovering intrinsic physiological parameters, such as the functional cross section of Photosystem II, from apparent (experimental) values. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1601–1615, 2016     

The diversity, distribution and ecology of diatoms from Antarctic inland waters

Diatoms are abundant and diverse in many Antarctic freshwaters, with a general trend of decreasing diversity moving southwards. They form an important component of many benthic algal communities in streams and standing waters but are generally less common in the phytoplankton. Diatoms are excellent ecological indicator species and, because their remains are preserved in many sedimentary environments, there appears to be a great potential for palaeoenvironmental reconstruction and the examination of past diversity. A lack of taxonomic precision and consistency, coupled with the insufficient collection from some geographical areas, makes the estimation of the number of Antarctic diatom species problematic.     

Copepod nauplii from the barrier reef of Belize

A study of areal distribution of the copepod nauplii near mangrove covered cays on the barrier reef of Belize was begun in the summer of 1989 and continued in the spring of 1990 with the collection of twenty samples from four locations. At distances in the order of 100 of meters to 1000 from the mangrove prop roots there were thousands of nauplii m^–3. In the samples from Twin Cays where the plankton tows were made 15 m from the prop roots or less the average was 387 nauplii m^–3. Copepod nauplii compose 60% of the metazoan plankton abundance in all of the samples. Harpacticoid nauplii were the largest single component of the plankton in every sample; they account for 42% to 76% of the copepod nauplii. Cyclopoid nauplii represent 13 to 40% and are second to the harpacticoid nauplii. Calanoid nauplii account for 2% to 23% of the copepod nauplii.     

COPTOCLAVID BEETLES (COLEOPTERA: ADEPHAGA) FROM THE LOWER CRETACEOUS OF SPAIN: A NEW FEEDING STRATEGY IN BEETLES

Abstract:  Currently the beetle family Coptoclavidae consists of four subfamilies known from the Upper Triassic–Lower Cretaceous (Aptian). We describe two new subfamilies, three new genera and five new species from the Las Hoyas (Cuenca Province) and El Montsec (Lleida Province) localities of Barremian (Early Cretaceous) age from Spain: the first new subfamily, Hispanoclavinae, is from Las Hoyas and comprises one new genus, Hispanoclavina , and two new species, H. diazromerali and H. gratshevi ; the second, Coptoclaviscinae, is represented at El Montsec by one new species of Coptoclavella ( C. inexpecta ). In addition, at Las Hoyas the subfamilies Necronectinae and Coptoclavinae are each represented by one new genus and species: Ovonectes pilosum and Hoyaclava buscalionae , respectively. All beetles previously assigned to the family Coptoclavidae have been interpreted as active hunters. However, we consider Hispanoclavina and Hoyaclava to be filter-feeding, with forelegs adapted for filtering plankton (probably zooplankton because other members of the family are carnivorous) on and beneath the water surface. This represents a new feeding strategy in beetles (extant and extinct). The five new species extend the known geographical distribution of the Coptoclavidae into the western part of European Barremian deposits. The Las Hoyas locality now has the highest known diversity of coptoclavid species.     

背角无齿蚌(Anodonta woodiana)对浅水系统底栖和浮游藻类竞争关系的影响

底栖藻类和浮游藻类之间的竞争关系对浅水生态系统的结构、功能具有重要的影响,双壳类可通过滤食控制浮游藻类,从而改变底栖藻类与浮游藻类之间的竞争结果。论文通过比较放养背角无齿蚌(Anodonta woodiana)(蚌处理组)与不放养背角无齿蚌(对照组)系统中底栖藻类、浮游藻类的生物量和优势种等的变化,研究了滤食性双壳类对底栖藻类和浮游藻类间竞争的影响。结果表明,背角无齿蚌可显著降低浮游藻类生物量,提高水体透明度和沉积物表面光照条件,从而显著提高底栖藻类的生物量;背角无齿蚌也改变了浮游藻类的优势种,使优势种由蓝藻转变成硅藻。因此,滤食性双壳类有利于促进浅水生态系统从混水态向清水态转变,本研究结果对富营养化浅水湖泊修复与管理具有一定的参考意义。     

海南岛西北沿岸海域浮游桡足类的分布及群落特征

为了解昌江沿岸海域生态系统的现状, 探讨海域环境因素对浮游动物的生存环境造成的影响。本文根据2008年11月至2009年7月在海南西部昌江沿岸水域21个测站、4个季度月调查所获的浮游桡足类样品数据, 对该海域浮游桡足类群落结构、分布、季节变化及影响因素进行了分析。本调查共鉴定出桡足类44种, 隶属4目17科24属, 其中秋季25种, 冬季23种, 春季22种, 夏季23种。本次调查共发现优势种6种, 分别是微刺哲水蚤(Canthocalanus pauper)、亚强次真哲水蚤(Subeucalanus subcrassus)、锥形宽水蚤(Temora turbinata)、刺尾纺锤水蚤(Acartia spinicauda)、椭形长足水蚤(Calanopia elliptica)和精致真刺水蚤(Euchaeta concinna), 优势种以近岸暖水种居多。浮游桡足类丰度季节变化明显: 冬季最高, 达409 ind./m³; 秋季次之, 为144 ind./m³, 春季为55 ind./m³, 夏季最低仅为17 ind./m³。其丰度的平面分布显示: 秋、冬季节分别在海区中部和南部形成明显密集区, 春、夏季节则大致呈现由外海向近岸逐渐递减的趋势。浮游桡足类的多样性指数(H')表现为夏季>春季>秋季>冬季, 春、夏季的均匀度指数(J')明显高于秋、冬季。本调查反映出该海区的桡足类群落具有热带—亚热带区系特征, 种类组成季节更替明显, 桡足类种群受海域水温和硅藻的影响明显, 受盐度影响不明显。     

Light/Dark Cycle and Temperature-Their Impact on Phosphate-Limited Growth of Oscillatoria redekei VAN GOOR in Semicontinuous Culture

Phosphate-limited growth of Oscillatoria redekei in semicontinuous culture has been studied under conditions of continuous illumination at 20 °C as well as in a 12/12 hours light-dark cycle at temperatures between 5 °C and 20 °C. The subsistence quota (q₀) amounted to 0.052 μmol mm⁻³ under all conditions, when the phosphate quota was expressed on the basis of cell volume. The interaction between temperature and phosphate quota and its impact on growth rate are described by the following model: Parameter values are t_opt=24.5 °C, t_min=0.95 °C, μ_max =0.873 d⁻¹. The maximum phosphate quota was found to depend on temperature and to increase along with declining temperature.     

Physiological studies of the Pediococcus pentosaceus biofilm

Pediococcus pentosaceus, a bacterium recently used in human and animal probiotics, was used in combination with supports made from polylactic acid composite soybean meal was used to study biofilm formation, and it was found that dense biofilms developed by Day 1. Proteomic comparison between planktonic and biofilm cultures of P. pentosaceus showed distinct expression patterns of intracellular and extracellular proteins. Type I glyceraldehyde-3-phosphate dehydrogenase was upregulated in biofilm cultures and mediated cell adhesion and encouraged biofilm production. GMP synthase, which regulates GMP synthesis and acts as an intracellular signal molecule to control cell mechanisms and has been exploited in the development of new therapeutic agents, was also upregulated in the biofilm mode of growth. The present work serves as a basis for future studies examining the complex network of systems that regulate lactic acid bacterial (LAB) biofilm formation and can serve as a framework for studies of production of therapeutic agents from LAB.