The effect of nutrient enrichment on nitrogen fixation activity in the Bay of Quinte,Lake Ontario

Nitrogen fixation was measured in situ by the ¹⁵N tracer technique in the Bay of Quinte, Lake Ontario, and three lake enclosures with different nutrient enrichment. The fixation rates in the Bay were low but detectable during the summer season. The fixation activities were found to be correlated with the presence of nitrogen-fixing blue-green algae and the distribution of the algal species in the water was affected by nitrate enrichment. The study showed that, with the addition of nitrate, species not able to fix atmospheric nitrogen became predominant. However, in the absence of external nitrogen (i.e., nitrate), species able to fix nitrogen became dominant. Phosphorus enrichment alone did result in higher N-fixation rates in the water and, without the addition of phosphorus, the fixation rates are lower and fluctuate throughout the season, presumably dependent on the availability of phosphorus in the water.A comparison between the ¹⁵N-isotopic method and the acetylene reduction method is reported and the factors involved in the variations between these two methods are discussed.     

Complex seasonality observed amongst diverse phytoplankton viruses in the Bay of Quinte,an embayment of Lake Ontario

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Role of algae in the diet of Chironomus plumosus F. semireductus from the Bay of Quinte,Lake Ontario

The importance of algae and different algal species to the chironomid diet was investigated through examination of the guts of chironomids taken from 5 locations in Big Bay (Bay of Quinte, Lake Ontario) at 6 times during the ice-free period. A comparison of the density and condition of algal cells at the two ends of the gut provided information on the digestibility of each algal species and the algal biomass assimilated by the chironomids. Diatoms and two species of green algae were assimilated over much of the summer, but the blue green algae were digested only late in the season when their populations were aged and/or dying. In terms of energy contribution, diatoms, especially Stephanodiscus spp. and Melosira spp., were most important in May (99% of all algal biomass assimilated), August (98%), and Octobr (92%), while the blue green species, Microcystis aeruginosa, was predominant in September (76%). Only a few small greens were assimilated in June and July. The contribution of algae as a food source to chironomid energetics was small, and reached a maximum in August and September (15%–34%). It is postulated that bacteria are a more important food source.     

Heavy Metal Contents in Tissues of Dominant Species of the Benthos and in Bottom Sediments of Zolotoi Rog Bay, Sea of Japan

Data on heavy metal contents in polychaetes and free-living nematodes inhabiting the bottom sediments of Zolotoi Rog Bay near the port of Vladivostok are reported. Chronically high contents of heavy metals (Fe, Cu, Zn, and Cd) were found in the bottom sediments and in the infauna. The levels of some toxic elements in tissues of the polychaete Dorvillea (Schistomeringos) japonica inhabiting polluted sediments of Zolotoi Rog Bay were higher than in worms of this species from relatively clean areas of the Sea of Japan. Similar high concentrations of Fe were found in the polychaete Capitella capitata and the nematode Oncholaimium ramosum. The highest concentrations of Fe, Zn, Cu, and Cd were found in tissues of the free-living nematode O. ramosum. Chronic heavy pollution of the bottom sediments leads to a decrease in the biodiversity of the infauna and to specific metal-tolerant communities.Original Russian Text Copyright © 2005 by Biologiya Morya, Davydkova, Fadeeva, Kovekovdova, Fadeev.     

Seasonality and distribution of epilithic diatoms,macroalgae and macrophytes in a spring-fed stream system in Ontario,Canada

A study of the epilithic diatom, macroalgal and macrophyte communities from a spring-fed stream in Ontario, Canada was undertaken from September 1996 to July 1997. The relative abundance of the epilithic diatom flora, percent cover of macroalgal and macrophyte taxa, and several physical and chemical stream conditions were monitored along a 20-m stretch at each of four sites, approximately every 2 months. Several stream conditions were relatively constant over the sampling period (pH, maximum width and maximum depth), while others exhibited a distinct seasonal pattern (water temperature, specific conductance and daylength) and some fluctuated strongly with no discernable seasonal pattern (turbidity, current velocity). A total of 124 taxa were identified from the four sites, including 79 epilithic diatoms, three macroalgal diatom species (large gelatinous masses), one cyanobacterium, two red algae, eight green algae, one chrysophyte alga, one tribophyte alga, three mosses, three horsetails and 23 angiosperm taxa. Species richness was positively correlated to stream channel maximum width and depth, indicating that the total number of species tends to increase in a downstream direction. Distribution of several diatom and macroalgal species was significantly correlated to stream conditions (e.g. Gomphonema parvulum and Phormidium subfuscum with current velocity); however, the vast majority of species did not display seasonal variation in abundance that could be explained by changes in stream conditions. Many of the taxa identified from Blue Springs Creek are common elsewhere in North America.     

Biogenic silica record in the sediments of Little Round Lake,Ontario

The biogenic silica (BSi) record has been determined in the sediments of Little Round Lake, Ontario in order to review its postglacial development and study the relationship between BSi and diatoms. BSi concentrations in the sediment stratigraphy were found to correspond for the most part to the trophic history of Little Round Lake. Calculation of accumulation rates for BSi improved the correspondence of the BSi profile to the trophic history. Thus, BSi is a valuable paleoindicator when concentration and flux profiles are considered concurrently. Regression analysis of BSi and diatoms revealed that the concentration of BSi in the sediments was not a simple function of diatom numbers or biovolume, but that factors such as a correction for the rate of dissolution and abundance of chrysophycean scales and cysts were also important.     

Application of the index of marsh bird community integrity to coastal wetlands of Georgian Bay and Lake Ontario,Canada

Ecological indicators have gained increasing attention within the scientific community over the past 40 years. Several taxonomic groups have been used successfully as indicators including most prominently fish, invertebrates, plants, and birds because of their ability to indicate environmental changes. In the Laurentian Great Lakes region, there has been recent concern over the applicability of using indicators on a basin-wide scale due to species range restrictions and lake-based differences. The objective of this study was to determine the ability of the Index of Marsh Bird Community Integrity (IMBCI) to indicate land use disturbance surrounding coastal marshes of Georgian Bay and Lake Ontario. To meet this objective, we surveyed birds and vegetation at 14 marshes in Georgian Bay (low land use disturbance) and Lake Ontario (high land use disturbance). Even though Lake Ontario marshes were surrounded by significantly more altered land than Georgian Bay marshes, and had poorer water quality, we found significantly fewer birds in Georgian Bay marshes (mean = 8.2) compared to Lake Ontario (mean = 13.7) and no significant difference in IMBCI scores. This inconsistency could be due to vegetation differences affecting the strength of the index, because Georgian Bay wetlands had significantly more bulrush (Schoenoplectus spp.) and floating vegetation, while Lake Ontario wetland vegetation was taller and cattail-dominated (Typha spp.). These findings suggest that the IMBCI may not be useful on a basin-wide scale in the Great Lakes region in detecting human disturbance surrounding wetlands.     

Whole-lake lead burdens in sediments of lakes in southern Ontario,Canada

The anthropogenic stable lead content of the sediments of eight softwater Precambrian lakes in southern Ontario was measured at 34–92 sites per lake. Whole-lake anthropogenic lead burdens varied between only 610 and 770 mg m^–2. There was no relationship between lead burden and either water replenishment time of the lake (T_W) or the ratio of watershed area to lake area (Ad/A₀), which varied by factors of 4 and 12 respectively. These results can be explained if a) the lead deposition in this region is uniform, and b) the only significant input of lead to the lakes is via deposition from the atmosphere directly on the lakes' surfaces. Therefore spatial differences in anthropogenic lead within a lake represent the redistribution or focusing pattern of the sediments.     

Spatial and temporal trends of target organic and inorganic micropollutants in Lake Maggiore and Lake Lugano (Italian-Swiss water bodies): contamination in sediments and biota

DDx, PCBs, PBDEs, Hg, and As contamination in sediments and aquatic organisms of different trophic levels (zooplankton, mussel, fish) were analyzed in Lake Maggiore and Lake Lugano, two large deep perialpine lakes. In the period 2001–2015, we analyzed the spatial and temporal trends of the considered pollutants to detect potential contamination sources and to compare concentrations with Sediment Quality Guidelines (SQGs) or existing Quality Standards (QSs). DDx and Hg contamination deriving from past industrial activities in the Pallanza Basin still exceeded SQGs in sediments and QSs in fish, with potential risks for the ecosystem. Banned in Europe in 1985, PCBs showed low residual values, while recent PBDE peaks resulted in the exceedance of the QSs for biota in both lakes, probably due to current industrial activities. Arsenic mainly derives from geochemical origin. The analysis of the biomagnification of toxicants in a pelagic food chain in Lake Maggiore (zooplankton–fish) according to a stable isotope approach is also presented, according to both the Trophic Magnification Factor and the Trophic Level-adjusted BioMagnification Factor: the importance of seasonality and a Hg > DDx ≈ PBDEs biomagnification capacity were observed. Low PCB bioaccumulation was detected in biota, probably because equilibrium was not reached yet in young fish.     

Temperature and light: The determining factors in maximum depth distribution of aquatic macrophytes in Ontario,Canada

In stratified lakes with high light penetration, the maximum depth at which macrophytes occur is frequently limited by temperature. At this depth a variety of species may be found. On the other hand, when the clarity of water limits the light penetration and the temperature at depth is sufficient for good plant growth, the plants occurring at greatest depth are ones that do not require photosynthetic oxygen for root growth. Such plants include the Charales, Isoetes, Utricularia and Ceratophyllum.     

微波消解-FAAS法分析并比较旱芹(Apium graveolens L.)不同部位八种金属元素的含量

采用微波消解法处理旱芹根、茎、叶,并用火焰原子吸收法测定其中的Na、K、Ca、Mg、Fe、Mn、Zn、Cu 8种金属元素的含量。结果表明:旱芹中富含人体必需的Na、K、Mg、Fe、Ca等元素,各元素在不同部位含量有一定差异。Fe元素在旱芹根中含量为883.57μg.g-1,明显高于茎和叶;Ca、Zn和Mn元素在旱芹叶中的含量分别为11 103.74,214.04,88.07μg.g-1,明显高于茎和根;K、Na和Mg元素在旱芹茎中的含量高于根和叶中,Cu元素含量在各部位差异不大。方法的加标回收率为96.8%～105.8%,相对标准偏差(RSD)≤3.36%。     

Community collocation of four submerged macrophytes on two kinds of sediments in Lake Taihu, China

To explore a method for rapid restoration and artificial regulation of submerged macrophytes in large-scale restoration of eutrophic lakes, the succession and the biodiversity changes of four communities composed of four native, common submerged macrophytes, Hydrilla verticillata, Potamogeton malaianus, Vallisneria spiralis and Najas marina, on two kinds of sediments were investigated. Under low light intensity (reduced by 99%), the plant biomass changed with seasonal changes, plant competition, and environmental stress. The competitive capability for light differed in the four species due to different shoot height and tiller number. After 405 days of transplantation, H. verticillata became dominant in all communities. The biomass of H. verticillata, with strong ability to endure low water light environment, accounted for more than 90% of the total community biomass, and P. malaianus had only weak growth, while V. spiralis and N. marina almost disappeared. Based on livability and biomass of submerged macrophytes on two sediment types, brown clay sediment appeared to be more favorable for the settlement of the plants, while fertile sludge sediment was suitable for vegetative growth. In conclusion, the improvement of habitats and the selection of appropriate plant species are of the greatest importance for ecological restoration of the aquatic ecosystem.     

Nutrient release rates from the sediments of Saginaw Bay,Lake Huron

Direct measurements of net production rates and pore water profiles of solutes in the fine-grained sediments of Saginaw Bay, imply corresponding steady-state fluxes to the overlying water of 1.1–1.3 (I), 450–1010 (NH₄ ⁺), 1250–2650 (Si(OH)₄), 3000–3400 (Ca²⁺), 440–1330 (Mg²⁺), 1.5–728 (Fe²⁺), and 179–281 (Mn²⁺) moles/m²/day and 11.0–11.8 (alkalinity) meq/m²/day at 17.5 °C. Silica production rates in sediments apparently follow first order kinetics with a rate coefficient of 0.09/day and a steady-state silica concentration of 1.2 mM at 23.5°C. The remaining solutes follow kinetics approximately independent of solute concentration over the range of concentrations observed. Measured solute production rates are consistent with observed solute profiles only if lateral diffusion gradients are maintained in the sediments by the burrowing and irrigation activity of benthic organisms such asChironomous, the dominant burrower in Saginaw Bay. Assuming that solute fluxes from Saginaw Bay are representative of all of the post-glacial sediments of Lake Huron, the iodine flux from sediments is comparable to the total fluvial input of iodine. The extrapolated silica fluxes from Lake Huron sediments balance the estimated biogenic silica flux to the sediments.     

Distribution of Iron-Oxidizing Bacteria in the Nordic Uranium Tailings Deposit, Elliot Lake, Ontario, Canada

Iron-oxidizing bacteria are present within the top 2 m (but not always at the surface) and near the water table-capillary fringe of the vegetated Nordic uranium deposit, Elliot Lake, Ontario, Canada. They are distributed uniformly in the top 0.5 m of unvegetated tailings. The locations of these bacteria correlate with zones of pyrite oxidation as delineated in previous studies by the formation of soluble iron and sulfate. Heterotrophic bacteria are also present in the tailings, with greatest concentrations at the surface and near the water table-capillary fringe. Sulfate-reducing bacteria were detected in the soil and peat at the base of the tailings. The results of this study suggest that the establishment of vegetation directly upon the tailings surface does not arrest bacterial pyrite oxidation.     

Sediment Composition,Mud-water Interchanges and the Role of Macrophytes in Dal Lake,Kashmir

The particulate phase of lake sediments showed a marked reduction in the concentration of N, P, K and C during late spring and summer. Larger amounts of these elements were found towards the autumn, and these higher levels were maintained through winter until early spring. The reduction in the concentration of these mineral nutrients was greatest during the growing season of the macrophytes.     

Examination of the role of dreissenids and macrophytes in the phosphorus dynamics of Lake Simcoe,Ontario, Canada

Our study examines the relative importance of the causal linkages between exogenous total phosphorus (TP) loading and internal nutrient recycling with the water quality conditions in Lake Simcoe, Ontario, Canada. We enhance the mechanistic foundation of a simple TP mass-balance model, originally developed to guide the eutrophication management in the system. The structural improvements include the incorporation of macrophyte dynamics, the explicit representation of the role of dreissenids in the system, and the improved portrayal of the interplay between water column and sediments. Our model provides good agreement with the observed TP variability in the system during the study period (1999–2007). Consistent with empirical evidence, our model predicts that macrophyte uptake from the interstitial waters is responsible for a significant loss of P from the sediments. Our model also suggests that dreissenids filter a considerable amount of particulate P from the water column, but the effective clearance rate is significantly lower with a substantial amount of the filtered particles (> 85%) returned into the water column as faeces, pseudofeces or other metabolic excreta. P diffusive fluxes from the sediments account for about 30–35% of the exogenous P loading in Lake Simcoe. The sediments in the main basin are mostly driven by fast diagenetic processes of settling organic matter from the epilimnion, suggesting an internal P loading of 9.2 tonnes yr^− 1. Finally, our study attempts to explain the lack of distinct decreasing trends in ice-free TP concentrations after the invasion of dreissenid mussels, suggesting that the presence of active nutrient recycling pathways, potentially magnified by the particular morphological features and hydrodynamic patterns of Lake Simcoe, could counterbalance the direct effects of dreissenid filtration.