The primary production of phytoplankton in the restored Maltañski Reservoir in Poland

Patterns in composition, abundance and diversity of the annelid fauna (Polychaeta and Oligochaeta) in 22 sandy beaches in Iceland were explored. The effect of exposure on annelid distribution was studied. A total of 5651 annelids were recorded from 160 core samples. Oligochaetes (chiefly Tubificidae) dominated the annelid assemblage whereas polychaetes represented a minor fraction. Polychaetes were relatively more abundant in exposed than in sheltered beaches, contrary to oligochaetes. Meiofaunal polychaete species were also more abundant in exposed than in sheltered beaches. Southwest beaches seemed more diverse in annelid species than northern ones. Annelid diversity did not differ between sheltered and exposed sites, but higher diversity was attained in fine sands at sheltered areas. Cluster analysis revealed large differences between beaches in the annelid community composition. The general patterns found suggest that beach exposure is a major factor conditioning macro- and meiofaunal polychaete and oligochaete distribution along the Icelandic coast.     

The spring development of phytoplankton in Lake Erken: species composition,biomass, primary production and nutrient conditions — a review

Relative abundance and within-lake distributions of three fishes, northern redbelly dace (Phoxinus eos), finescale dace (Phoxinus neogaeus), and central mudminnow (Umbra limi), were examined using minnow traps in Tuesday Lake, a small bog lake in the Upper Peninsula, Michigan. For these species, catches in minnow traps placed at the perimeter of the lake were 21 to 52 times higher than catches in midlake traps. Variance: mean ratios of perimeter trap catches indicated that both dace species were highly aggregated while the distribution of mudminnows was less aggregated or random. Over an 11 day period during which all fish caught were removed from the lake, catch per unit effort (CPUE) of both dace species declined in response to fish removal. In contrast, CPUE for mudminnows was low initially, increased to an asymptote and then declined only in the last 5 days of the fish removal. The patterns of CPUE for mudminnows indicated that mudminnow trapability and/or activity was reduced in the presence of high densities of dace. The low abundance of dace in traps with many mudminnows suggested mudminnows avoided traps already containing dace. Throughout the removal period, CPUE provided an accurate index of dace abundance, whereas this was true for mudmnnows only after dace populations had been reduced drastically. Therefore, in any use of minnow traps to estimate populations, both spatial distributions and relative species abundance of small fishes must be taken into account.     

Rapid immobilization of applied nitrogen in saline–alkaline soils

The dynamics of inorganic N are important in soil, and this applies particularly to the saline–alkaline soils of the former lake Texcoco in Mexico with high pH and salinity where a forestation program was started in the 1970s. In soils of lake Texcoco, in Mexico, more than 50% of applied N could not be accounted for one day after application of 200 mg kg^–1 soil along with glucose amendment. It was not clear whether this was due to abiotic or biotic processes, the form of inorganic N applied or the result of applying an easily decomposable substrate. We investigated this by adding glucose and 200 mg kg^–1 soil as (NH₄)₂SO₄-N or KNO₃-N to sterilized and unsterilized soil. The changes in inorganic and ninhydrin N, microbial biomass C and production of CO₂ were then monitored. Between the time of applying N and extraction with 0.5 M K₂SO₄, i.e., after ca 2 h, approximately 110 mg NH₄ ⁺-N kg^–1 dry soil could not be accounted for in the unsterilized and sterilized soil and that remained so for the entire incubation in the sterilized soil. After 1 day this increased to 140 mg NH₄ ⁺-N kg^–1 dry soil in the unsterilized control and 170 mg NH₄ ⁺-N kg^–1 dry soil in C amended soil. Volatilization of NH₃ accounted for 56 mg NH₄ ⁺-N kg^–1 so the rest appeared to be adsorbed on the soil matrix. The NH₃ volatilization and NH₄ ⁺ fixed in the soil matrix remained constant over time and no oxidation to NO₂ ^– or NO₃ ^– had occurred, so unaccounted N in unsterilized soil was probably incorporated into the microbial biomass in excess of what was required for metabolic activity. The unaccounted N was ca 70 mg NO₃ ^––N in nitrate amended soil after 3 days and 138 NO₃ ^––N when glucose was additionally added. Losses through abiotic processes were absent as inferred from changes in sterilized soil and the aerobic incubation inhibited possible losses through denitrification. It was inferred that NO₃ ^– that could not be accounted for was taken up by micro-organisms in excess of what was required for metabolic activity.     

The response of soil respiration to different N compounds addition in a saline–alkaline grassland of northern China

不同形态氮化合物添加对中国北方盐渍化草地土壤呼吸的影响持续增加的氮沉降在提高陆地生态系统生产力的同时也会对土壤微生物产生显著影响;土壤呼吸由植物根系呼吸和土壤微生物呼吸组成,因此影响植物生产力和微生物的因子都会影响到土壤呼吸。以往氮富集对土壤呼吸的研究主要在土壤中性的草地生态系统开展,而对于盐渍化草地土壤呼吸是如何响应氮沉降的研究尚不多见,这限制了全球变化陆地生态系统土壤呼吸模型预测的准确性和完整性。本研究以中国北方农牧交错带盐渍化草地为研究对象,通过3年(2017–2019年)野外监测土壤呼吸及相关生物和非生物因子的变化,探讨了不同形态氮化合物添加(NH₄NO₃、(NH₄)₂SO₄和NH₄HCO₃)对盐渍化草地土壤呼吸的影响及其调控机制。结果表明：(i)土壤呼吸受大气温度、土壤温度及降水的调控,呈现双峰的季节动态变化趋势和显著的年际差异。(ii)与对照相比,经过3年的处理,土壤呼吸在NH₄NO₃、(NH₄)₂SO₄和NH₄HCO₃添加处理下分别提高了19.9%、13.0%和16.6%。(iii)NH₄NO₃添加对土壤呼吸较高的促进作用与较高的地上生物量、地下生物量以及土壤NO₃⁻含量有关。(iv)在NH₄HCO₃ 添加处理下,土壤碳排放(土壤呼吸)显著增加而碳输入(净生产力)无显著改变,表明NH₄HCO₃添加会降低土壤碳的固持。(v)净地下生产力(BNPP)是盐渍化草地土壤呼吸的最主要调控因子,并且土壤阳离子浓度和pH值通过影响土壤微生物间接影响土壤呼吸。上述研究结果表明,草地添加NH₄NO₃的研究高估了氮沉降对土壤呼吸的影响,并且在碳循环预测模型中应充分考虑盐渍化草地土壤碳动态。     

Ecological studies in the plankton of certain freshwater ponds of hyderabad — India II,phytoplankton —1

Summary The paper discusses the distribution and periodicity of Volvocales, Chlorococcales, Desmids, Euglenineae and phytoplankton in general occurring in three freshwater ponds. It is observed that the polluted pond harboured densest phytoplankton population comprising of Volvocales, Chlorococcales, Myxophyceae and Euglenineae. Bluegreens were particularly abundant in alkaline waters (pH 8.69) which were rich in nitrates (12.58) and dissolved oxygen (5.5). The ponds harbouring diatoms and desmids were less polluted. It is emphasized that ecological behaviour of several species does not fall in harmony with the behaviour of the taxonomic group or class of which they are members. Therefore, attention was paid to the ecology of individual species as far as possible.In their seasonal fluctuations different algal groups were apparently favoured by the ecological conditions given below.     

The ‘island mass’ effect on the phytoplankton and primary production of the Hawaiian Islands

A 170 station oceanographic reconnaissance in the nearshore waters of the Hawaiian Islands has emphasized the ‘island mass’ effect in increasing primary production and chlorophyll a standing crop as well as in altering community assimilation ratios. The distribution of oceanographic parameters and micronutrients indicate that one of the enriching mechanisms is turbulence and vertical mixing in island channels.The species composition of the net phytoplankton communities characteristic of inshore, offshore, and oceanic stations is given and the relative importance of the nannoplankton component discussed. The nannoplankton dominated in all regions, with a tendency for the net/nannoplankton ratio to increase toward the base of the euphotic zone. The net phytoplankton consisted chiefly of open ocean diatom species with neritic species restricted to a narrow inshore environment.     

The diversity,biomass and production of zooplankton in Lake Inarijärvi

About 650 zooplankton samples were collected from Lake Inarijärvi in 1977–1979 from the littoral and pelagial zones of the lake. One hundred and twenty-three zooplankton taxa were found and most of them can be considered euplanktonic.The most important species were Holopedium gibberum, Daphnia cristata, Cyclops spp. and Eudiaptomus spp. Mean pelagial zooplankton biomass was 0.29 g m^–3 in the 0–5 m depth zone, 0.17 g m^–3 in 5–10 m and 0.11 g m^–3 in 10–20 m.The zooplankton biomass at a sandy shore was about 0.09 g m^–3, at a stony shore 0.05 g m^–3 and at a vegetated shore 0.76 g m^–3. About 70% of the whole zooplankton production consisted of crustaceans.The sum of herbivore and carnivore zooplankton production in the pelagial area during the summer was 210–330 kg ha^–1 × 3 months.     

Variability of phytoplankton distribution and primary production around Elephant Island,Antarctica, during 1990–1993

The distribution and abundance of phytoplankton within a sampling grid of 50×10³ km² around Elephant Island were determined from early January to mid-March of 4 successive years, 1990–1993. The number of stations where physical-optical-biological data were obtained from the surface to a maximum of 750 m ranged from 74 in 1990 to 206 in 1993. Contour maps of chlorophyll-a (chl-a) concentrations showed marked mesoscale patchiness that varied from month to month and also interannually. The distribution patterns for chl-a were similar when plotting surface concentrations or integrated values to 100 m. Three major zones could be distinguished that differed in both physical and biological characteristics. Stations in the northwest portion of the grid (Drake Passage waters) and in the southeast portion of the grid (Bransfield Strait waters) showed the most pronounced interannual variations, with phytoplankton biomass and rates of primary production being considerably higher in 1990–91 than in 1992–93. The central portion of the sampling grid, which included the major frontal system north of Elephant Island, showed the smallest interannual variations in both biological and physical parameters and the highest rates of primary production. Phytoplankton biomass and rates of primary production were correlated with depth of the upper mixed layer (UML), which in turn was correlated with the measured wind stress. The mean depth of the UML was 50 m, while the mean depth of the euphotic zone was 90 m. Using the measured mean surface solar irradiance (550 Einsteins m^–2 s^–1), the mean irradiance experienced by cells in the UML of 50 m would be around 105 E m^–2 s^–1, which is similar to the measured I_k (light saturation) value for photosynthesis (101 Em^–2 s^–1). The mean value from all cruises for chl-a in surface waters was 0.7 mg m^–3, while the mean rate of primary production was 374 mg Cm^–2 day^–1.     

Strength of phytoplankton–nutrient relationship: evidence from 13 biomanipulated ponds

Phytoplankton biomass–nutrient relationship is widely used by lake managers to assess the eutrophication impact and to set the nutrient targets. Submerged vegetation and large zooplankton grazing have long been identified as factors weakening the relationship by decoupling phytoplankton from nutrients. Proving this decoupling unambiguously is difficult because, in natural systems, many factors act together, blurring each other’s effect. In this article, we present the results of continuous monitoring of 13 ponds where the effects of submerged vegetation and zooplankton grazing were enhanced by biomanipulation (fish removal). The monitoring allowed these effects to be assessed and compared with the pre-biomanipulation situations when phytoplankton biomass was mainly nutrient driven. The comparison showed a strong weakening effect of submerged vegetation and large zooplankton grazing on the chlorophyll a–total phosphorus relationship suggesting that a considerable degree of ecological quality of ponds affected by eutrophication can be restored even when nutrient-loading reduction is not feasible.     

Composition and biomass of summer metazoan plankton in the 0–200 m layer of the Atlantic sector of the Antarctic

Composition of the metazoan plankton was studied during R.V. Dmitry Mendeleev cruise 43 (February to April, 1989) in the Atlantic sector of the Southern Ocean. Samples were collected from ten stations at six locations. Four of the locations were in open oceanic waters along the 15° W longitude. Two others were in the Bransfield Strait and in inshore waters near Elephant Island. At three locations at 15° W sampling was conducted twice or thrice. At all stations three different sampling gears were used to collect different size groups of Zooplankton: series of hauls were performed by 2001 water-bottle, mesoplankton net and macroplankton trawl for depths from 200 m to the surface. The average biomass of Zooplankton in open oceanic waters was 20.55 g · m^–2 wet weight. Copepoda Calanoida dominated composing 54.8% of the total plankton, followed by Euphausiacea (19.8%), Ctenophora (9.7%) and Copepoda Cyclopoida (7.2%). Biomass of any other taxonomic group was less than 1g·m^–2. The relative biomass of Calanoida had a tendency to decrease southward along 15°W from 86.1 to 68.1% in February and from 81.8 to 23.6% in March–April. The relative biomass of Euphausiacea increased in the same manner from 2.3 to 17.8% in February and from 3.7 to 41.6% in March–April. The average biomass of calanoids from February to March–April decreased from 77.3 to 31.2% and that of euphausiids increased from 6.2 to 33.8%. The contribution of copepods and euphausiids to the production of the plankton community in the Antarctic is discussed.     

Microbial population index and community structure in saline–alkaline soil using gene targeted metagenomics

Population indices of bacteria and archaea were investigated from saline–alkaline soil and a possible microbe–environment pattern was established using gene targeted metagenomics. Clone libraries were constructed using 16S rRNA and functional gene(s) involved in carbon fixation (cbbL), nitrogen fixation (nifH), ammonia oxidation (amoA) and sulfur metabolism (apsA). Molecular phylogeny revealed the dominance of Actinobacteria, Firmicutes and Proteobacteria along with archaeal members of Halobacteraceae. The library consisted of novel bacterial (20%) and archaeal (38%) genera showing ≤95% similarity to previously retrieved sequences. Phylogenetic analysis indicated ability of inhabitant to survive in stress condition. The 16S rRNA gene libraries contained novel gene sequences and were distantly homologous with cultured bacteria. Functional gene libraries were found unique and most of the clones were distantly related to Proteobacteria, while clones of nifH gene library also showed homology with Cyanobacteria and Firmicutes. Quantitative real-time PCR exhibited that bacterial abundance was two orders of magnitude higher than archaeal. The gene(s) quantification indicated the size of the functional guilds harboring relevant key genes. The study provides insights on microbial ecology and different metabolic interactions occurring in saline–alkaline soil, possessing phylogenetically diverse groups of bacteria and archaea, which may be explored further for gene cataloging and metabolic profiling.     

The contribution of small individuals to density–body size relationships

The relationship between density and body size is central to our understanding of species assemblages. The greatest challenge in sampling complete assemblages is obtaining reliable estimates of all taxa regardless of body size. We therefore examined the density-body size relationship in a coral reef fish assemblage using a novel sampling method which permits reliable quantification of the small/cryptic reef fish fauna. We found a negative linear relationship between density and adult body size. This is in marked contrast to the polygonal relationship previously described for other local scale assemblage studies. Our linear relationship may be a consequence of the larger differences in body size among taxa. Spanning over five orders of magnitude, the range of body sizes appears to be an important factor in shaping density-body size relationships.     

Length–biomass equations to allow rapid assessment of semi-aquatic bug biomass in tropical streams

Length–biomass equations are relatively easy and cost-effective for deriving insect biomass. However, the exact relationship can vary between taxa and geographical regions. Semi-aquatic bugs are abundant and are indicators of freshwater quality, but there are no studies investigating the effect of habitat disturbance on their biomass, although it is useful in assessing ecological processes. We identified the best-fit length–biomass models to predict the biomass of semi-aquatic bugs (Hemiptera, Gerromorpha) collected from streams in Sabah, Malaysia. We used 259 juvenile and adult semi-aquatic bugs to compare a range of plausible length–biomass functions, and to assess whether relationships differed across the following families and body forms: (1) Cylindrostethinae, Gerrinae, and Ptilomerinae, which are subfamilies within Gerridae consisting of small-to-large bugs that have long and slender bodies, (2) Halobatinae, a subfamily within Gerridae, consisting of small-to-medium bugs with wide heads and thoraxes as well as short abdomens, and (3) Veliidae, which are small bugs with stout bodies. Estimation used five fitting functions – linear regression, polynomial regression order 2, 3, and 4, and power regression – on the following groupings: three body forms combined; each body form with life stages (juvenile and adult) combined; and each body form with life stages separated. Power regressions were the best fit in predicting the biomass of semi-aquatic bugs across life stages and body forms, and the predictive power of models was higher when the biomass of different body forms was calculated separately (specifically for Halobatinae and Veliidae). Splitting by life stages did not always result in additional improvement. The equations from this study expand the scope of possible future ecological research on semi-aquatic bugs, particularly in Southeast Asia, by allowing more studies to consider biomass-related questions.     

Seasonal dynamics of macrophytes and phytoplankton in shallow lakes: a eutrophication‐driven pathway from plants to plankton?

1. Seasonal relationships between macrophyte and phytoplankton populations may alter considerably as lakes undergo eutrophication. Understanding of these changes may be key to the interpretation of ecological processes operating over longer (decadal‐centennial) timescales. 2. We explore the seasonal dynamics of macrophytes (measured twice in June and August) and phytoplankton (measured monthly May–September) populations in 39 shallow lakes (29 in the U.K. and 10 in Denmark) covering broad gradients for nutrients and plant abundance. 3. Three site groups were identified based on macrophyte seasonality; 16 lakes where macrophyte abundance was perennially low and the water generally turbid (‘turbid lakes’); 7 where macrophyte abundance was high in June but low in August (‘crashing’ lakes); and 12 where macrophyte abundance was high in both June and August (‘stable’ lakes). The seasonal behaviour of the crashing and turbid lakes was extremely similar with a consistent increase in nutrient concentrations and chlorophyll‐a over May–September. By contrast in the stable lakes, seasonal changes were dampened with chlorophyll‐a consistently low (<10–15 μg L^?1) over the entire summer. The crashing lakes were dominated by one or a combination of Potamogeton pusillus, Potamogeton pectinatus and Zannichellia palustris, whereas Ceratophyllum demersum and Chara spp. were more abundant in the stable lakes. 4. A long‐term loss of macrophyte species diversity has occurred in many shallow lakes affected by eutrophication. One common pathway is from a species‐rich plant community with charophytes to a species‐poor community dominated by P. pusillus, P. pectinatus and Z. palustris. Such compositional changes may often be accompanied by a substantial reduction in the seasonal duration of plant dominance and a greater tendency for incursions by phytoplankton. We hypothesise a slow‐enacting (10–100 s years) feedback loop in nutrient‐enriched shallow lakes whereby increases in algal abundance are associated with losses of macrophyte species and hence different plant seasonal strategies. In turn such changes may favour increased phytoplankton production thus placing further pressure on remaining macrophytes. This study blurs the distinction between so‐called turbid phytoplankton‐dominated and clear plant‐dominated shallow lakes and suggests that plant loss from them may be a gradual process.     

Combinatorial strategy of sorbitol feeding and low-temperature induction leads to high-level production of alkaline β-mannanase in Pichia pastoris

A process for efficient production of an alkaline β-mannanases from Bacillus sp. N16-5 was established by heterologous expression using Pichia pastoris. A high producing strain was generated by removing the native β-mannanases signal peptide and increasing the copy number of the mature β-mannanases gene. High cell density fermentation of this strain in 1-L bioreactor led to a production level of 4164 U/mL after 96 h of induction. Sorbitol co-feeding and temperature-lowering strategies both increased the β-mannanase production levels. Combined usage of these two strategies achieved the most effective result—the enzyme level reached 6336 U/mL within 84 h, which to our best knowledge is the highest production level reported for the expression of extreme β-mannanase thus far. The strategy described in this work can also be adapted to express other important industrial enzymes with extreme properties.     

The contribution of island populations to in situ genetic conservation

Genetic variation is often lower within island populations, however islands may also harbor divergent genetic variation. The likelihood that insular populations are genetically diverse or divergent should be influenced by island size and isolation. We tested this assumption by comparing patterns of genetic variation across all major island song sparrow populations along the Pacific North American coast. Allelic richness was moderately lowered even on islands which are close to large, potential sources. The most significant differences in allelic richness occurred on very small or highly remote islands. Gene diversity was significantly lower only on remote or very small islands. We found that island populations contribute to regional genetic variation through both the amount of genetic variation and the uniqueness of that variation. The partitioning of this contribution was associated with the size and isolation of the island populations.     

Physical and chemical characters,phytoplankton and primary production of Ezequiel Ramos Mexía Reservoir (Argentina)

We describe the distribution in space and time of a series of physical and chemical variables, phyto-plankton, and primary production in Ezequiel Ramos Mexía Reservoir (Argentina). Its waters are soft, poor in nutrients and with a low transparency that greatly depresses primary production. Phytoplankton data indicate the presence of 79 taxa with Bacillariophyceae, Cyanophyta and Chlorophyta alternatively dominant. Chlorophyll a was always low and never exceeded 3 mg m⁻³. Based on these results, the trophic status of this ecosystem is discussed.     

Abiostress resistance and cellulose degradation abilities of haloalkaliphilic fungi: applications for saline–alkaline remediation

Extremophiles - Soda saline–alkaline lands are significantly harmful to agriculture; thus, effective strategies to remediate such soil are urgently needed. Multiple negative factors exist in...