COMPOSITION OF EXTRACELLULAR POLYMERIC SUBSTANCES FROM PERIPHYTON ASSEMBLAGES IN THE FLORIDA EVERGLADES1

In wetland habitats, periphyton is a common component of open‐water areas with species assemblage determined by local water quality. Extracellular polymeric substances (EPS) secreted by algae and bacteria give structure to periphyton, and differences in EPS chemistry affect the functional roles of these polymers. The Florida Everglades provide a unique opportunity to study compositional differences of EPS from distinctive algal assemblages that characterize areas of differing water chemistry. Water conservation area (WCA)‐1 is a soft‐water impoundment; periphyton was loosely associated with Utricularia stems and amorphous in structure, with a diverse desmid and diatom assemblage, and varying cyanobacterial abundance. Extracellular polymers were abundant and were loosely cell‐associated sheaths and slime layers in addition to tightly cell‐associated capsules. The EPS were complex heteropolysaccharides with significant saccharide residues of glucose, xylose, arabinose, and fucose. Carboxylic acids were also prominent, while ester sulfates and proteins were small components. Structured, cohesive cyanobacteria‐dominated periphyton was observed in WCA‐2A, a minerotrophic impoundment, and filaments were heavily encrusted with calcium carbonate and detrital matter. EPS were primarily cell‐associated sheaths, and polymer residues were dominated by glucose, xylose, fucose, and galactose, with uronic acids also a significant component of the polymers. Principal components analysis revealed that periphyton community assemblage determined the monosaccharide composition of EPS, which ultimately determines a range of biogeochemical processes within the periphyton.     

NONPHOSPHORUS LIPIDS IN PERIPHYTON REFLECT AVAILABLE NUTRIENTS IN THE FLORIDA EVERGLADES,USA1

Algal and plant production of nonphosphorus lipids in place of phospholipids is a physiological response to low phosphorus (P) availability. This response has been shown in culture and in marine plankton studies, but examples from freshwater algae remain minimal. Herein, we analyzed the nutrient contents and lipid composition of periphyton communities across the Florida Everglades ecosystem. We hypothesized that in phosphate‐poor areas, periphyton in high‐ and low‐sulfate waters would vary the proportion of sulfolipids (SLs) and betaine lipids (BLs), respectively. In phosphate‐enriched areas, periphyton would produce more phospholipids (PLs). We observed that at low‐P sites, PLs were a minor lipid component. In cyanobacteria‐dominated periphyton where sulfate was abundant, BLs were only slightly more abundant than SLs. However, in the low‐P, low‐sulfate area, periphyton were comprised to a greater degree green algae and diatoms, and BLs represented the majority of the total lipids. Even in a P‐rich area, PLs were a small component of periphyton lipid profiles. Despite the phosphorus limitations of the Everglades, periphyton can develop tremendous biomass. Our results suggest a physiological response by periphyton to oligotrophic conditions whereby periphyton increase abundances of nonphosphorus lipids and have reduced proportions of PLs.     

SPECIES COMPOSITION,BIOMASS, AND NUTRIENT CONTENT OF PERIPHYTON IN THE FLORIDA EVERGLADES1

Periphyton biomass, nutrient dynamics in the biomass, and species composition were studied in two Florida Everglades sloughs from August 1991 to August 1992. Periphyton biomass on macrophytes was strongly season-dependent. Maximum biomasses, 1180, 161, and 59 g dry mass.m^?2 on Eleocharis vivipara, E. cellulosa, and Nymphaea odorata, respectively, occurred in summer and early autumn; winter and spring periphyton biomass was very low (practically not measurable). Periphyton was dominated by blue-green algae (cyanobacteria) during the summer and autumn; diatoms dominated during the winter and spring. Green algae occurred mostly during the summer and autumn, but their growth was sparse and did not contribute significantly to periphyton biomass. Nitrogen-to-phosphorus ratios in the periphyton were very high (59–121:1), suggesting phosphorus limitation of periphyton growth. The periphyton contained large concentrations of calcium (up to 22.3% on dry mass basis) especially in late summer and autumn.     

PRESENCE AND DIVERSITY OF ALGAL TOXINS IN SUBTROPICAL PEATLAND PERIPHYTON: THE FLORIDA EVERGLADES,USA1

Production of toxic secondary metabolites by cyanobacteria, collectively referred to as cyanotoxins, has been well described for eutrophied water bodies around the world. However, cohesive cyanobacterial mats also comprise a significant amount of biomass in subtropical oligotrophic wetlands. As these habitats generally do not support much secondary production, cyanotoxins, coupled with other physiological attributes of cyanobacteria, may be contributing to the minimized consumer biomass. Periphyton from the Florida Everglades has a diverse and abundant cyanobacterial assemblage whose species produce toxic metabolites; therefore, by screening periphyton representative of the greater Everglades ecosystem, six different cyanotoxins and one toxin (domoic acid) produced by diatoms were identified, ranging in content from 3 × 10^?9 to 1.3 × 10^?6 (g · g^?1), with saxitoxin, microcystin, and anatoxin‐a being the most common. While content of toxins were generally low, when coupled with the tremendous periphyton biomass (3–3,000 g · m^?2), a significant amount of cyanotoxins may be present. While the direct effects of the toxins identified here on the local grazing community need to be determined, the screening process utilized proved effective in showing the broad potential of periphyton to produce a variety of toxins.     

DICHOTOMOSIPHON IN FLORIDA SPRINGS1

Dichotomosiphon tuberosus occurs abundantly in the outflows, pools, and streams of at least 5 hard, freshwater springs of north central Florida. This tubular alga produces extensive bright green mats which harbor epiphytes, unicellular algae, ciliates, and amphipods. Within the spring, most tubes remain in the vegetative condition. After 12–15 days under certain laboratory conditions, the tubes produce highly characteristic, sex organs and akinetes.     

祁连山3种典型生态系统土壤微生物活性和生物量碳氮含量

 测定分析了祁连山高寒草甸、山地森林和干草原土壤中微生物活性、生物量碳氮含量。结果显示：就土壤微生物生物量碳含量,森林比干草原和高寒草甸中分别高60%和120%以上,干草原比高寒草甸中高40%以上(p<0.05)。就土壤微生物生物量氮含量,0～5 cm土层,森林比高寒草甸和干草原中分别高64%和111%以上,高寒草甸比干草原中高29%;5～15 cm土层,森林比干草原和高寒草甸中分别高7%和191%以上,干草原比高寒草甸中高171% 以上(p<0.05)。森林和干草原中土壤微生物生物量碳比例比高寒草甸中高32%以上,0～5和5～15 cm土层,森林和干草原中土壤微生物生物量氮比例比高寒草甸中高150%以上（p<0.05）。就土壤微生物活性,0～5和5～15 cm土层,森林和高寒草甸比干草原中高26%以上;15～35 cm土层,森林比干草原和高寒草甸中高28%以上 (p<0.05)。土壤微生物生物量碳氮含量与有机碳含量及微生物生物量氮含量和比例与微生物生物量碳含量和比例呈现正相关（r²>0.30,p<0.000 1）。土壤微生物生物量氮含量、微生物生物量碳氮含量比例、微生物活性与土壤pH值呈显著负相关,土壤微生物生物量碳氮含量及其比例、微生物活性与土壤湿度呈正相关。说明祁连山3种生态系统土壤中微生物生物量和活性受气候要素、植被、有机碳、pH值和湿度等因素 的共同影响。     

微生物麦角甾醇的研究进展

麦角甾醇是真菌细胞膜的重要组成部分,是脂溶性维生素D2的前体,也是重要的医药化工原料.就微生物高产麦角甾醇菌株的选育及麦角甾醇生物合成的研究进展作了综述.     

SPATIAL ORDER IN MICROBIAL ECOSYSTEMS

(1) It is suggested that microbiologists are concentrating too much at present on homogeneous laboratory models such as the chemostat to simulate natural microbial ecosystems, which are not usually homogeneous but structured in time and space. (2) Natural microbial ecosystems that are spatially heterogeneous are reviewed and discussed. (3) Microbial interactions are briefly discussed in so far as they are relevant to spatially organized ecosystems. (4) Concepts such as ‘niche’ and ‘habitat’ are defined and discussed in terms of their applicability to microorganisms growing at specific points in solute gradient systems. The definitions currently accepted lack precision because they do not take into account the importance of spatial and temporal coordinates. Use of the words ‘compartment’ and ‘domain’ is advocated. The former corresponds to a cell, the latter to a region around it where the compartment has some influence, acting either as a source or as a sink for particular solutes. The terms ‘niche’ and ‘habitat’ are redefined for the activity domains of a compartment and the habitat domains of the ecosystem. The importance of the vectorial flow of solutes is stressed. (5) Current methodology in microbial ecology is briefly reviewed. (6) Methods specifically designed for investigating heterogeneous ecosystems are described, These include: (i) The gradostat, a system of interlinked culture vessels allowing the establishment of steady-state bidirectional solute gradients. (ii) Percolating columns. (iii) Capillary methods. (iv.) The thin film fermenter. (v) The use of two-dimensional diffusion plates or stopped time-dependent gradient plates. (vi) Gel-stabilized diffusion models established vertically in glass containers such as beakers. (vii) The use of one-dimensional gradient-plate techniques to determine the habitat characteristics of different microbial species. (viii) Investigations into naturally structured systems such as the bacterial colony.     

REPRODUCTION IN FEMALE MANATEES OBSERVED IN SARASOTA BAY, FLORIDA

Resightings of recognizable individual Florida manatees, Trichechus manatus latirostris , in Sarasota Bay provided information on life history and reproductive parameters. These parameters have been documented at winter aggregation sites, but few data existed for Florida's west coast at non-winter sites. Life history data are needed to estimate annual reproduction and survival rates and construct population models for manatees along west central Florida. Observations of 113 recognizable manatees of known sex sighted between 1993 and 1997 indicated a 1: 1 sex ratio. Fifty-three females produced at least 55 calves during five years of observation. Two large, presumably sexually mature females were never observed with calves in over five years of monitoring. Not surprisingly, several reproductive parameters matched those measured in previous studies at winter sites with a mean of 1.8 seasons of calf dependence, 2.2 seasons between births, and age of sexual maturity at 3–4 yr. Birth rates, fecundity, and proportions of females with calves varied only slightly among investigations.     

OBSERVATIONS ON FEEDING METHODS IN SOME FLORIDA ASCOGLOSSANS

Feeding methods are described for 12 Florida ascoglossans. Relationshipsbetween size and shape of radular teethand dimensions of foodalgae are analysed. Feeding in a diatom-eating species (Eylsiaevelinae) is described for the first time. The suctorial feedingof Ascobulla ulla and the structure of its radula and alimentarysystem clearly reveal that it is an ascoglossan, not a cephalaspid.The very complicated method of feeding in Oxynoe spp. is consideredan evolutionary "dead end", and the branching of the digestivegland and position of pharyngeal appendices seem to indicatethat the Elysiidae did not evolve from the Oxynoidae. New anddetailed observations on feeding in Elysia ornata, Placida kingstoni,and Ercolania funerea show that after cell sap has been suckedinto the pharynx, it is returned to the algal filament. Thisprocess may be repeated once or twice before the cell sap iseventually pumped into the stomach. Cell sap is probably mixedwith saliva in the pharynx to reduce its viscosity, and thepharyngeal regurgitation facilitates withdrawal of the remainingsap. ^*Present address: Ellebjergvej 22, 1 t.h., DK-2450 CopenhagenSV, Denmark. (Received 9 June 1980;     

植物残体与泥炭和泥炭矿体分类的初步探讨

泥炭植物残体是泥炭和泥炭矿体的主要组分。泥炭的植物组成与泥炭的分解度和营养状况密切相关。在进行泥炭分类时,植物残体组成是其重要依据。各泥炭矿体特征间“质”的差异也反映在泥炭植物残体组成成分的不同上。因此,在进行泥炭矿体分类时,可将矿层的植物残体组分作其依据。本文拟将我国的泥炭矿体分为富营养、中营养、贫营养和混合四个泥炭矿体型;并续分出十一个泥炭矿体组。     

HABITAT SELECTION BY MANATEES IN SARASOTA BAY, FLORIDA

Habitat selection by Florida manatees ( Trichechus manatus latirostris ) is influenced by, among other things, availability of food, thermal, and freshwater resources. However, habitat selection by females with dependent calves may differ from that of other demographic groups with regard to the relative importance of these factors. Additional factors that may influence habitat selection for females with dependent calves include ambient noise, strong currents, or increased foraging requirements. We examined distributional data for manatees from aerial surveys of the coastal waters near Sarasota, Florida, between 1994 and 2004 to determine whether habitat selection by groups of manatees that included calves differed from that of other groups. We characterized groups according to their location within seven habitat types. Enclosed bays not traversed by the Intracoastal Waterway had the highest proportions of groups with calves. Groups with calves used a No Entry refuge (from which almost all human use is barred) to a greater extent than did other groups. Overall, groups with calves exhibited significantly different habitat selection from groups without calves ( P < 0.001, χ²= 43.0, df = 6), but this was not consistent across seasons. During the winter and spring, thermal requirements influenced manatees to such an extent that all demographic groups selected habitat similarly.