Hydrodynamic habitat influences suspension feeding by unionid mussels in freshwater ecosystems

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Effects of desiccation and rewetting on the release and decomposition of dissolved organic carbon from benthic macroalgae

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Stoichiometric and growth responses of a freshwater filamentous green alga to varying nutrient supplies: slow and steady wins the race

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THE HORMESIS OF THE GREEN MACROALGA ULVA FASCIATA WITH LOW‐DOSE 60COBALT GAMMA RADIATION1

Homogenous germlings of the marine macroalga Ulva fasciata D. (synonym, Ulva lactuca L.) were used to study hormesis effects in macroalgae grown under a low dose of ⁶⁰Co γ‐ray radiation. The results of this study are the first to confirm the effects of macroalgal hormesis. Here it was demonstrated that growth of U. fasciata germlings was promoted substantially under 15 Gy of ⁶⁰Co γ‐ray radiation, with an average increase of algal biomass of 47.43%. The levels of polysaccharides and lipids varied among the tested material and showed no effects from the ⁶⁰Co γ‐ray radiation. However, the amount of protein was higher in the irradiated algae than in the control; the highest protein content of the irradiated algae was 3.958% (dry weight), in contrast to 2.318% in nonirradiated samples. This technique was applied to a field algal mass culture, which decreased the harvest time from 90 to 60 d. The mass culture approach may facilitate the production of macroalgae under unstable weather conditions such as typhoons in the summer or strong waves in the winter. The mass‐cultured macroalgae could be used as a source of bioenergy through the fermentation of algal simple sugars that derived from polysaccharides to produce ethanol.     

AN “ENVIRO‐INFORMATIC” ASSESSMENT OF SAGINAW BAY (LAKE HURON,USA) PHYTOPLANKTON: DATA‐DRIVEN CHARACTERIZATION AND MODELING OF MICROCYSTIS (CYANOPHYTA)1

Phytoplankton and Microcystis aeruginosa (Kütz.) Kütz. biovolumes were characterized and modeled, respectively, with regard to hydrological and meteorological variables during zebra mussel invasion in Saginaw Bay (1990–1996). Total phytoplankton and Microcystis biomass within the inner bay were one and one‐half and six times greater, respectively, than those of the outer bay. Following mussel invasion, mean total biomass in the inner bay decreased 84% but then returned to its approximate initial value. Microcystis was not present in the bay during 1990 and 1991 and thereafter occurred at/in 52% of sample sites/dates with the greatest biomass occurring in 1994–1996 and within months having water temperatures >19°C. With an overall relative biomass of 0.03 ± 0.01 (mean + SE), Microcystis had, at best, a marginal impact upon holistic compositional dynamics. Dynamics of the centric diatom Cyclotella ocellata Pant. and large pennate diatoms dominated compositional dissimilarities both inter‐ and intra‐annually. The environmental variables that corresponded with phytoplankton distributions were similar for the inner and outer bays, and together identified physical forcing and biotic utilization of nutrients as determinants of system‐level biomass patterns. Nonparametric models explained 70%–85% of the variability in Microcystis biovolumes and identified maximal biomass to occur at total phosphorus (TP) concentrations ranging from 40 to 45 μg · L^?1. From isometric projections depicting modeled Microcystis/environmental interactions, a TP concentration of <30 μg · L^?1 was identified as a desirable contemporary “target” for management efforts to ameliorate bloom potentials throughout mussel‐impacted bay waters.     

Ecological assessments with algae: a review and synthesis

Algae have been used for a century in environmental assessments of water bodies and are now used in countries around the world. This review synthesizes recent advances in the field around a framework for environmental assessment and management that can guide design of assessments, applications of phycology in assessments, and refinements of those applications to better support management decisions. Algae are critical parts of aquatic ecosystems that power food webs and biogeochemical cycling. Algae are also major sources of problems that threaten many ecosystems goods and services when abundances of nuisance and toxic taxa are high. Thus, algae can be used to indicate ecosystem goods and services, which complements how algal indicators are also used to assess levels of contaminants and habitat alterations (stressors). Understanding environmental managers' use of algal ecology, taxonomy, and physiology can guide our research and improve its application. Environmental assessments involve characterizing ecological condition and diagnosing causes and threats to ecosystems goods and services. Recent advances in characterizing condition include site‐specific models that account for natural variability among habitats to better estimate effects of humans. Relationships between algal assemblages and stressors caused by humans help diagnose stressors and establish targets for protection and restoration. Many algal responses to stressors have thresholds that are particularly important for developing stakeholder consensus for stressor management targets. Future research on the regional‐scale resilience of algal assemblages, the ecosystem goods and services they provide, and methods for monitoring and forecasting change will improve water resource management.     

棉花铃期与棉籽干物质积累模拟模型

基于不同熟性棉花品种的异地分期播种试验,综合量化品种特性、主要气象条件（温度、太阳辐射）和栽培措施（施氮量）对棉花铃期与棉籽干物质积累的影响,基于生理发育时间,建立棉花铃期模拟模型,并基于棉籽生长的“库限制”假设,建立棉籽干物质积累模拟模型.通过量化棉铃对位叶氮浓度的变化,为模型构建氮素效应函数.利用不同生态点的品种、播期和施氮量田间试验资料对模型进行检验,结果表明：德夏棉1号、科棉1号和美棉33B的铃期预测值与实测值的根均方差（RMSE）分别为2.25 d、2.61 d和2.75 d,科棉1号和美棉33B的棉籽干物质模拟值与实测值的RMSE分别为9.5 mg·seed^-1和8.2 mg·seed^-1.表明该模型预测精度较高.     

Nocturnal drift of mayfly nymphs as a post-contact antipredator mechanism

1. The predominantly nocturnal constrained drift of stream invertebrates is commonly regarded as a behaviour that avoids encounters with visually foraging fish in the water column. The alternative explanation, that drift peaks are caused by bottom-feeding, nocturnal predators, has rarely been tested.
2. We examined these hypotheses by collecting invertebrate drift in five streams in northern Finland: one with brown trout ( Salmo trutta , a drift-feeding fish), one with alpine bullhead ( Cottus poecilopus , a benthic fish), one with both species, and two fishless streams.
3. Drift by Baetis mayflies was aperiodic or slightly diurnal in both fishless streams on all sampling occasions. In contrast, drift was nocturnal in streams with trout and, to a lesser extent, in the stream with bullhead. Non-dipteran prey drifted mainly nocturnally in all streams with fish, whereas Diptera larvae were less responsive to the presence of fish.
4. In laboratory experiments, bullheads were night-active, causing a much higher frequency of drift by touching Baetis at night than during the day. Thus, increased nocturnal drift may serve to avoid both visual predators (a pre-contact response) and benthic fish (a post-contact response). In streams with bottom-feeding fish, nocturnal drift should be caused by increased drift by night rather than by reduced drift by day.     

Minimal models of top-down control of phytoplankton

1. A set of models describing the dynamics of top-down control of phytoplankton by Daphnia in lakes is reviewed. The basis of these models is a simple and well-known model that has been used, among other things, to demonstrate the paradox of enrichment.
2. We discuss minimal extensions that allow this model to mimic the effects of spatial heterogeneity, planktivory, seasonality and inedible algae.
3. These models generate hypotheses about mechanisms that may cause patterns observed in the field such as:

4. We discuss the way in which such very simple models may contribute to the building of theories about plankton dynamics in the field, and the caveats of interpreting wrongly the message from models.     

Feasibility of utilizing Rhizoclonium in pulping and papermaking

Material of Rhizoclonium from brackish water in Taiwan was investigated for its possible use in pulping and papermaking. After beating, this filamentous alga produced a pulp with a length to width ratio of about 10, much less than that of a typical wood pulp. Handsheets made from this pulp had a moderate breaking length of 4.02 km. Cooking pre-beaten pulp with a low chemical charge (5–25%NaOH) at a low cooking temperature (100 ^°C), and for a short time (30–120 min) gave high algal pulp yields (70–80%). This cooking process was sulfur-free, but the water requirement was high. After cooking and further caustic soda and bleaching treatments, wide-angle X-ray diffraction and FTIR spectroscopy showed that the crystallinity of the algal pulp increased substantially, but type I cellulose conformation was retained. The best pulp mechanical strengths (breaking length 5.23 km,zero-span tensile strength 79.2 Nm g^-1, bursting index of 2.2 kpa m² g^-1) were obtained after cooking for 1 h with 20% NaOH. Because of the morphological characteristics of the algal strands, the pulp generally lacked bursting, tearing and folding strengths, but proper blending with softwood pulp increased the tensile breaking length to8.40 km, the tearing index to 14.5 mNm² g^-1, the bursting index to 6.42 kpam² g^-1 and the folding endurance to 4299 double folds, i.e. levels comparable to a typical kraft pulp. The algal pulp thus showed clear potential as a supplement for traditional medium strength wood pulps. This revised version was published online in August 2006 with corrections to the Cover Date.