Colonization by lake benthos of hard substrata in the water column versus on the bottom

1998 ◽  
Vol 49 (2) ◽  
pp. 157 ◽  
Author(s):  
G. P. Quinn ◽  
P. S. Lake ◽  
E. S. G. Schreiber
Keyword(s):  
Water Column ◽  
Benthic Macroinvertebrates ◽  
Open Water ◽  
Almost All ◽  
Benthic Animals ◽  
Hard Substrata

Little work has been done on colonization by lake benthos, particularly onto hard substrata. This study experimentally compared the rates of colonization of hard substrata (bricks) in a lake by benthic macroinvertebrates from two sources — the water column and the bottom. Colonization onto bricks (as mimics of stones) placed on the bottom of the lake was compared with colonization onto bricks suspended in the water column, where they could not be reached by crawling fauna. Almost all taxa colonizing bottom bricks also colonized suspended bricks, including taxa usually considered benthic (e.g. gastropods, mites, oligochaetes and planarians). Water-column samples confirmed the presence of these taxa in open water. These results suggest that many benthic animals in lakes may move through the water column more readily than previously considered; constant movement by lake benthos may be in response to shortage of resources.

Subglacial brine flow and wind-induced internal waves in Lake Bonney, Antarctica

2020 ◽  
Vol 32 (3) ◽  
pp. 223-237
Author(s):  
Jade P. Lawrence ◽  
Peter T. Doran ◽  
Luke A. Winslow ◽  
John C. Priscu
Keyword(s):  
Water Column ◽  
Internal Waves ◽  
Open Water ◽  
Surface Discharge ◽  
Katabatic Wind ◽  
Neutral Buoyancy ◽  
Cold Temperatures ◽  
Glacier Terminus ◽  
Wind Events ◽  
Taylor Glacier

AbstractBrine beneath Taylor Glacier has been proposed to enter the proglacial west lobe of Lake Bonney (WLB) as well as from Blood Falls, a surface discharge point at the Taylor Glacier terminus. The brine strongly influences the geochemistry of the water column of WLB. Year-round measurements from this study are the first to definitively identify brine intrusions from a subglacial entry point into WLB. Furthermore, we excluded input from Blood Falls by focusing on winter dynamics when the absence of an open water moat prevents surface brine entry. Due to the extremely high salinities below the chemocline in WLB, density stratification is dominated by salinity, and temperature can be used as a passive tracer. Cold brine intrusions enter WLB at the glacier face and intrude into the water column at the depth of neutral buoyancy, where they can be identified by anomalously cold temperatures at that depth. High-resolution measurements also reveal under-ice internal waves associated with katabatic wind events, a novel finding that challenges long-held assumptions about the stability of the WLB water column.

Phosphorus Budgets and Stoichiometry during the Open-Water Season in Two Unmanipulated Lakes in the Experimental Lakes Area, Northwestern Ontario

1994 ◽  
Vol 51 (12) ◽  
pp. 2739-2755 ◽  
Author(s):  
P. Campbell
Keyword(s):  
Water Column ◽  
Bottom Sediments ◽  
Open Water ◽  
Short Term ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Phosphorus Budgets ◽  
Mass Balance Approach ◽  
Primary And Secondary Producers ◽  
Column Total

A comparative mass-balance approach is used to describe and quantify phosphorus (P) cycles during the open-water season in two unmanipulated Experimental Lakes Area (ELA) lakes. A bimodal cycle generally prevailed, in which water-column total phosphorus (TP = total dissolved P plus sestonic particulate P) peaked just after ice-out and again late in the summer. Changes in mass of water-column TP were often much larger than corresponding net external inputs. Shifts of P to and from either zooplankton or fish in the water column do not explain the P residuals. Rather, the bottom sediments must have been adding P to the water column. Short-term regeneration of P from the bottom sediments also probably occurs in artificially eutrophied ELA lakes. The mechanism of regeneration is probably biological. Other aspects of P cycling and P stoichiometry are discussed, particularly in relation to nutrient control of population structure and the function of primary and secondary producers.

Colonization of depopulated crinoids by symbionts: who comes from the bottom and who from the water column?

2015 ◽  
Vol 95 (8) ◽  
pp. 1607-1612 ◽  
Author(s):  
E.S. Mekhova ◽  
P.Y. Dgebuadze ◽  
V.N. Mikheev ◽  
T.A. Britayev
Keyword(s):  
Water Column ◽  
Field Experiments ◽  
Dispersal Ability ◽  
Long Distance ◽  
Sandy Substrate ◽  
Limited Dispersal ◽  
Set Up ◽  
Almost All ◽  
High Degree

Previous experiments with the comatulid Himerometra robustipinna (Carpenter, 1881) demonstrated intensive host-to-host migration processes for almost all symbiotic species both within host aggregations and among hosts separated by several metres. The aim of this study was to check the ability of symbionts to complete long-distance migrations, by means of two in situ experiments which depopulated the crinoid host. Two different sets of field experiments were set up: exposure of depopulated crinoids (set 1) on stony ‘islands’ isolated from native crinoid assemblages by sandy substrate, and (set 2) in cages suspended in the water column. Hosts from set 1 were exposed for 1, 2, 3 and 4 weeks to assess whether substrate has an influence on the symbionts' long-distance migrations. In set 2 cages were exposed for 10–11 days, aiming to check whether symbionts were able to disperse through the water column with currents. These experiments allow the conclusion that post-settled symbionts can actively migrate among their hosts. Symbionts are able to reach their hosts by employing two different ‘transport corridors’, by drifting or swimming in water column, and by moving on the bottom. Comparison of experimental results allows the division of symbionts into two conventional groups according to the dispersal ability of their post-settled stages: (1) species able to complete long-distance migrations, (2) species unable to migrate or having limited dispersal ability. The finding of the free-living shrimp Periclimenes diversipes Kemp, 1922 in set 2 raises the question about the factors that affect such a high degree of specialization of crinoid assemblages.

Influence of extended water column mixing during the first 2 years of hypolimnetic oxygenation on the phytoplankton community of Amisk Lake, Alberta

1997 ◽  
Vol 54 (9) ◽  
pp. 2133-2145 ◽  
Author(s):  
D J Webb ◽  
R D Robarts ◽  
E E Prepas
Keyword(s):  
Water Column ◽  
Trophic Status ◽  
Phytoplankton Community ◽  
Euphotic Zone ◽  
Open Water ◽  
Eutrophic Lake ◽  
Cyanobacterial Blooms ◽  
Chl A ◽  
Hypolimnetic Oxygenation ◽  
Physical Variables

The phytoplankton community, physical variables, and nutrient and chlorophyll a (Chl a) concentrations were monitored during the first two of six open-water seasons of hypolimnetic oxygenation in double-basined Amisk Lake, Alberta. Deep mixing of the water column in the treated basin (Zmax = 34 m) in spring was enhanced by hypolimnetic oxygenation. Oxygenation began in June 1988, when stratification was likely already established, but subsequent year-round treatment favoured an extended spring diatom bloom (Asterionella formosa and Cyclotella spp.), followed by a delay in the development of, and reduction in the severity of, cyanobacterial blooms (Aphanizomenon flos-aquae and Anabaena flos-aquae) in 1989. Historically, mean summer Chl a and total phosphorus (TP) concentrations in the euphotic zone (0-6 m) of the treated basin were 15.9 ± 1.6 and 33.5 ± 1.5 µg ·L-1, respectively, indicating a eutrophic lake. In 1988 and 1989, mean summer Chl a (10.0 ± 0.6 and 8.1 ± 0.7 µg ·L-1, respectively) and TP concentrations (29.0 ± 0.5 and 22.5 ± 0.9 µg ·L-1, respectively) in this stratum were lower than historic values (P < 0.05), indicating that the trophic status of Amisk Lake had shifted towards mesotrophy.

Characterization of the photoautotrophic algal and bacterial communities in a large, shallow, subtropical lake using HPLC-PDA based pigment analysis

1998 ◽  
Vol 55 (1) ◽  
pp. 206-219 ◽  
Author(s):  
Alan D Steinman ◽  
Karl E Havens ◽  
J William Louda ◽  
Nancy M Winfree ◽  
Earl W Baker
Keyword(s):  
Water Column ◽  
Chlorophyll A ◽  
High Performance ◽  
Principal Component ◽  
Open Water ◽  
High Performance Liquid Chromatographic ◽  
Lake Okeechobee ◽  
Pheophytin A ◽  
Pigment Analysis ◽  
Liquid Chromatographic

Pigment abundances of the oxygenic and anoxygenic photoautotrophic communities from sediments and the water column in Lake Okeechobee, Florida, were estimated using reverse-phase high-performance liquid chromatographic (RP-HPLC) and photodiode array (PDA) UV/VIS (350-800 nm) spectrophotometric analyses. Thirty lipophilic pigments were identified and measured in the samples, with the most abundant overall (sediment and open-water samples combined) being chlorophyll a (38.1%), fucoxanthin (12.6%), pheophytin a (7.6%), zeaxanthin (6.6%), and pyropheophytin a (3.6%). Relative abundance of chlorophyll a was greater in the water column than in the sediments (58.3 versus 24.3% of all pigments) whereas pheophytin a comprised 9.1% of the total pigments in the sediments but only 3.7% of the total pigments in the water column. Principal component analysis (PCA) separated the sediment samples from those collected in the water column; this discrimination appears to be a function of pigment integrity in that sediment assemblages had much greater relative abundances of degraded pigments. Different regions of the lake were weakly separated by PCA based on pigments. The relatively weak degree of separation may reflect the overwhelming abundance of chlorophyll a at all sites. Overall, the pigment assemblage in Lake Okeechobee suggests cyanobacteria-diatom dominance. Out of 65 sampling events, pigments from anoxygenic photoautotrophs (e.g., bacteriochlorophylls) were detected 17 times but accounted for >20% of total chlorophyll only five times. Bacteriochlorophylls were observed only in the sediments and were most abundant during June and September, when winds were calm and temperatures warm, and at relatively shallow sites.

scholarly journals Using Convolutional Neural Networks for Detection and Morphometric Analysis of Carolina Bays from Publicly Available Digital Elevation Models

2021 ◽  
Vol 13 (18) ◽  
pp. 3770
Author(s):  
Mark A. Lundine ◽  
Arthur C. Trembanis
Keyword(s):  
Neural Networks ◽  
Convolutional Neural Networks ◽  
Feature Detection ◽  
Digital Elevation Models ◽  
Open Water ◽  
Atlantic Coastal Plain ◽  
Detection Scheme ◽  
Carolina Bays ◽  
Digital Elevation ◽  
Almost All

Carolina Bays are oriented and sandy-rimmed depressions that are ubiquitous throughout the Atlantic Coastal Plain (ACP). Their origin has been a highly debated topic since the 1800s and remains unsolved. Past population estimates of Carolina Bays have varied vastly, ranging between as few as 10,000 to as many as 500,000. With such a large uncertainty around the actual population size, mapping these enigmatic features is a problem that requires an automated detection scheme. Using publicly available LiDAR-derived digital elevation models (DEMs) of the ACP as training images, various types of convolutional neural networks (CNNs) were trained to detect Carolina bays. The detection results were assessed for accuracy and scalability, as well as analyzed for various morphologic, land-use and land cover, and hydrologic characteristics. Overall, the detector found over 23,000 Carolina Bays from southern New Jersey to northern Florida, with highest densities along interfluves. Carolina Bays in Delmarva were found to be smaller and shallower than Bays in the southeastern ACP. At least a third of Carolina Bays have been converted to agricultural lands and almost half of all Carolina Bays are forested. Few Carolina Bays are classified as open water basins, yet almost all of the detected Bays were within 2 km of a water body. In addition, field investigations based upon detection results were performed to describe the sedimentology of Carolina Bays. Sedimentological investigations showed that Bays typically have 1.5 m to 2.5 m thick sand rims that show a gradient in texture, with coarser sand at the bottom and finer sand and silt towards the top. Their basins were found to be 0.5 m to 2 m thick and showed a mix of clayey, silty, and sandy deposits. Last, the results compiled during this study were compared to similar depressional features (i.e., playa-lunette systems) to pinpoint any similarities in origin processes. Altogether, this study shows that CNNs are valuable tools for automated geomorphic feature detection and can lead to new insights when coupled with various forms of remotely sensed and field-based datasets.

Late Pleistocene deposits at Wretton, Norfolk. I. Ipswichian interglacial deposits

1970 ◽  
Vol 258 (818) ◽  
pp. 1-30 ◽  
Keyword(s):  
Sea Level ◽  
Local Development ◽  
Open Water ◽  
Wide Distribution ◽  
Meandering River ◽  
Satisfactory Analysis ◽  
Marine Influence ◽  
Zone Ii ◽  
Almost All ◽  
Eemian Interglacial

Interglacial deposits found in the low terrace at Wretton, Norfolk, were formed in the zones II and III of the Ipswichian interglacial. The variety of sediments found is associated with the fluviatile environments of a meandering river. During zone II there was a regional mixed oak forest, with the local development of alder carr, fen, reedswamp and open water communities. During zone III the regional vegetation was more open and Carpinus became an important woodland tree. Locally, fen, reedswamp and open-water communities persisted, but alder carr was absent. The plants give some indication that the climate may have been more continental than at present, a number of species occurring which are not native to the British post-glacial flora but which have a wide distribution on the Continent. A brief comparison of the vegetational history is made with that of other Ipswichian interglacial sites in England and with the correlative Eemian interglacial on the Continent. The interglacial sections at Wretton form one of the richest Ipswichian sites for non-marine Mollusca so far found in England. The presence of a few more southern or more continental species, not now living in England, confirms that the climate was probably slightly warmer than at present, at least in summer. Numbers are large enough for satisfactory analysis in almost all sections, so that the environmental conclusion they suggest can be checked against those deduced from the plants. In general, these conclusions match and indicate a series of deposits laid down by a plant-rich Fenland river, a true ancestor of the present river Wissey, in its channel and neighbouring parts of its floodplain. The occurrence of brackish water species of Mollusca allows levels of marine influence to be clearly integrated with the vegetational history. Brackish horizons occur between — 1.95 m and + 0.45 m O.D. in zone II b deposits, giving an indication of sea-level at this stage. The zone III deposits, although at a lower level, show no trace of brackish influences and a possible oscillation of sea-level is inferred.

scholarly journals Isotope fractionation between dissolved and suspended particulate Fe in the oxic and anoxic water column of the Baltic Sea

2013 ◽  
Vol 10 (1) ◽  
pp. 233-245 ◽  
Author(s):  
M. Staubwasser ◽  
R. Schoenberg ◽  
F. von Blanckenburg ◽  
S. Krüger ◽  
C. Pohl
Keyword(s):  
Baltic Sea ◽  
Water Column ◽  
Isotope Composition ◽  
Open Water ◽  
Deep Basin ◽  
Strong Concentration ◽  
Suspended Particulate ◽  
Oxidative Precipitation ◽  
The Difference ◽  
The Baltic

Abstract. Fe isotope ratios and concentrations of dissolved Fe (Fedis, < 0.45 μm) and of suspended particulate Fe (FeSPM) were analyzed from a depth profile through the anoxic Eastern Gotland Basin water column, Baltic Sea. Results show a sharp gradient in δ56Fedis across the ferruginous layer with δ56Fedis = −0.4‰ in the euxinic deep basin and δ56Fedis = &amp;plus;0.3‰ in the oxic upper water column. The isotopic gradient overlaps with a strong concentration gradient of Fedis, a concentration maximum in FeSPM and lower δ56FeSPM values than δ56Fedis. These features indicate preferential loss of light Fe isotopes from solution to suspended iron-oxyhydroxides (FeIOH) during typical oxidative precipitation across the redox interface. The sign of the overall fractionation, Δ56FeIOH-Fe(II)(aq) < 0‰, is in contrast to similar, mostly non-marine redox environments, where Δ56FeIOH-Fe(II)(aq) > 0‰. The difference appears to be the result of isotope exchange dominated by reaction kinetics in the marine water column, rather than equilibrium fractionation generally inferred for oxidative Fe precipitation elsewhere. High residual δ56Fedis immediately above the oxic–ferruginous interface and throughout the oxic water column suggests that any potential dissolved Fe export from marine reducing waters into the oxic open water column is enriched in the heavy isotopes. In the deep, mildly euxinic water column above the level of Fe sulfide saturation, a decreasing δ56FeSPM trend with depth and a generally low δ56Fedis are comparable to trends generally observed in marine anoxic sediment profiles where microbial reductive Fe dissolution occurs. The isotope composition of the redox-cycled Fe inventory in anoxic marine basins mainly reflects the balance between external fluxes, driving the composition towards crustal δ56Fe values, and intensity of internal recycling, driving δ56Fe towards negative values.

scholarly journals Effects of loss of perennial lake ice on mixing and phytoplankton dynamics: insights from High Arctic Canada

2010 ◽  
Vol 51 (56) ◽  
pp. 56-70 ◽  
Author(s):  
Julie Veillette ◽  
Marie-Josée Martineau ◽  
Dermot Antoniades ◽  
Denis Sarrazin ◽  
Warwick F. Vincent
Keyword(s):  
Water Column ◽  
Open Water ◽  
Fold Increase ◽  
Ice Cover ◽  
High Arctic ◽  
Meromictic Lakes ◽  
Lake Ice ◽  
Wind Speeds ◽  
Arctic Climate Change ◽  
Perennial Ice

AbstractPerennially ice-covered lakes are well known from Antarctica and also occur in the extreme High Arctic. Climate change has many implications for these lakes, including the thinning and disappearance of their perennial ice cover. The goal of this study was to consider the effects of transition to seasonal ice cover by way of limnological observations on a series of meromictic lakes along the northern coastline of Ellesmere Island, Nunavut, Canada. Conductivity-temperature profiles during a rare period of ice-free conditions (August 2008) in these lakes suggested effects of wind-induced mixing of their surface freshwater layers and the onset of entrainment of water at the halocline. Sampling of the mixed layer of one of these meromictic lakes in May and August 2008 revealed a pronounced vertical structure in phytoplankton pigments and species composition, with dominance by cyanobacteria, green algae, chrysophytes, cryptophytes and dinoflagellates, and a conspicuous absence of diatoms. The loss of ice cover resulted in an 80-fold increase in water column irradiance and apparent mixing of the upper water column during a period of higher wind speeds. Zeaxanthin, a pigment found in cyanobacteria, was entirely restricted to the <3μm cell fraction at all depths and increased by a factor of 2–17, with the greatest increases in the upper halocline region subject to mixing. Consistent with the pigment data, picocyanobacterial populations increased by a factor of 3, with the highest concentration (1.65 × 108 cells L−1) in the upper halocline. Chlorophyll a concentrations and the relative importance of phytoplankton groups differed among the four lakes during the open-water period, implying lake-specific differences in phytoplankton community structure under ice-free conditions.

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