scholarly journals Promotion of the Development of Sentinel Species in the Water Column: Example Using Body Size and Fecundity of the Egg-Bearing Calanoid Copepod Eurytemora affinis

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1442
Author(s):  
Sami Souissi ◽  
Anissa Souissi
Keyword(s):  
Water Column ◽  
Aquatic Ecosystems ◽  
Regression Line ◽  
Good Condition ◽  
Sudden Change ◽  
Sentinel Species ◽  
Late Winter ◽  
Ecological Indicator ◽  
Calanoid Copepods ◽  
Eurytemora Affinis

The development of sentinel species in aquatic ecosystems is mostly based on benthic organisms; however, organisms living in water column such as zooplankton have received less attention, except for some cladocerans. In this paper, a new ecological indicator based on simple measurements of the size and fecundity of egg-bearing calanoid copepods is developed. The well-studied estuarine copepod Eurytemora affinis is used to illustrate this new framework. A large database obtained from laboratory experiments developed under different conditions is used to define a reference regression line between clutch size (CS) and prosome length (PL). The same database allowed one to confirm that the coefficient of variation (CV) of CS is an adequate estimator of the accumulated stress at population level. The CV of PL shows very little variability in all experimental and field conditions. The values of CS and PL obtained from the Seine, Loire, Gironde, Scheldt and Elbe estuaries in Europe are compared to the reference regression line. A quality index (QI) is calculated as a percentage of difference between the observed and the predicted CS. The QI classified 19 samples collected in the Seine estuary between 2004 and 2010 into four classes according to the physiological condition of the copepod female. A single sampling from June 2004 (5.26%) showed a very good condition, whereas 57.9% of the sampling dates confirmed good conditions. On the other hand, four sampling dates were associated to very bad conditions and three sampling dates indicated bad conditions. Seven additional samples obtained from other European estuaries between 2006 and 2009 were also used. Females showing poor conditions were observed in the early spring of 2005 and 2008 as well as during the month of November. These years were characterized by very strong climatic anomalies with a very cold late winter in 2005 and a warm winter in 2008. Therefore, it seems that the QI perfectly reflected the strong stress caused by the sudden change in hydro-climatic conditions that have certainly affected the physiology of copepod females and probably the availability of food. The new indicator is very simple to calculate and can be generalised to several aquatic ecosystems (fresh water and brackish water) by targeting the dominating egg-bearing calanoid copepods. As in the case of E. affinis, the development of sentinel species based on copepods or cladocerans can enrich ecological and ecotoxicological studies given their capacity to integrate the variability of their habitats’ quality at the individual and population levels.

Extracellular enzymatic activities in the aquatic ecosystems of the Danube Delta. 2. Alkaline phosphatase activity

2021 ◽  
Vol 26 (1) ◽  
pp. 2269-2274
Author(s):  
IOAN PĂCEŞILĂ ◽  
EMILIA RADU
Keyword(s):  
Alkaline Phosphatase ◽  
Water Column ◽  
Aquatic Ecosystems ◽  
Temporal Dynamics ◽  
Extracellular Enzyme ◽  
Danube Delta ◽  
Phytoplankton Communities ◽  
Extracellular Enzymatic Activities ◽  
Adjacent Channels ◽  
Hydrolysis Of

Phosphorus is one of the most important inorganic nutrients in aquatic ecosystems, the development and functioning of the phytoplankton communities being often correlated with the degree of availability in assimilable forms of this element. Alkaline phosphatase (AP) is an extracellular enzyme with nonspecific activity that catalyses the hydrolysis of a large variety of organic phosphate esters and release orthophosphates. During 2011-2013, AP Activity (APA) was assessed in the water column and sediments of several aquatic ecosystems from Danube Delta: Roșu Lake, Mândra Lake and their adjacent channels – Roșu-Împuțita and Roșu-Puiu. The intensity of APA widely fluctuated, ranging between 230-2578 nmol p-nitrophenol L-1h-1 in the water column and 2104-15631 nmol p-nitrophenol g-1h-1 in sediment. Along the entire period of the study, APA was the most intense in Roșu-Împuțita channel, for both water and sediment samples. Temporal dynamics revealed its highest values in summer for the water column and in autumn for sediment. Statistical analysis showed significant seasonal diferences of the APA dynamics in spring vs. summer and autumn for the water column, and any relevant diferences for sediment.

scholarly journals Seasonal and interannual variability of physical and biological dynamics at the Shelfbreak Front of the Middle Atlantic Bight: nutrient supply mechanisms

2011 ◽  
Vol 8 (1) ◽  
pp. 1555-1590 ◽  
Author(s):  
R. He ◽  
K. Chen ◽  
K. Fennel ◽  
G. G. Gawarkiewicz ◽  
Keyword(s):  
Interannual Variability ◽  
Water Column ◽  
Circulation Model ◽  
Deep Ocean ◽  
Nutrient Supply ◽  
Early Summer ◽  
Late Winter ◽  
Middle Atlantic Bight ◽  
Seasonal And Interannual Variability ◽  
Middle Atlantic

Abstract. A size-structured ecosystem model is coupled to a 3-dimensional, high-resolution circulation model to investigate the seasonal and interannual variability of physical and biological states and their driving mechanisms at the shelfbreak front of the Middle Atlantic Bight (MAB). Simulated surface chlorophyll fields compare favorably to the satellite observations and capture the shelfbreak biomass enhancement, which is one of the essential biological features of the region. The domain-wide upper water column nutrient content peaks in late winter-early spring. The phytoplankton spring bloom starts 1–2 months later, followed by a zooplankton bloom in early summer. Seasonal and interannual variability in hindcast shelfbreak nutrient supply is controlled by three processes: (1) local mixing that deepens the mixed layer and injects deep ocean nutrients into the upper water column; (2) alongshore nutrient transport by the shelfbreak jet and associated currents; and (3) nutrient upwelling associated with shelfbreak bottom boundary layer convergence. Interannual variability of physical and biological processes are highlighted by cross-shelf nutrient budget diagnostics for spring 2004 and 2007, which show not only complex vertical structure of various dynamical terms, but also significant variations in magnitude between the two years.

scholarly journals Critical multi-stranded approach for determining the ecological values of diatoms in unique aquatic ecosystems of anthropogenic origin

2019 ◽  
Author(s):  
Rafał M. Olszyński ◽  
Ewelina Szczepocka ◽  
Joanna Żelazna-Wieczorek
Keyword(s):  
Surface Waters ◽  
Environmental Conditions ◽  
Aquatic Ecosystems ◽  
Ecological Indicator ◽  
Indicator Values ◽  
Chemical Parameters ◽  
Physical And Chemical Parameters ◽  
Characteristic Species ◽  
Physical And Chemical ◽  
Ecological Indicator Values

Background. The ecological state of surface waters is typically assessed by a multi-aspect approach based on a determination of its chemical and physical parameters, by hydromorphology and the use of indicator organisms such as benthic diatoms. By assigning ecological indicator values, it is possible to create diatom indices which serve as the basic tool in assessing the ecological status of surface waters. These ecological indicator values are set according to classification systems, such as the Van Dam et al. 1994 system, which classifies species of diatoms according to seven different ecological factors. However, recent studies on the autecology of diatoms have shown the need to verify and establish new ecological indicator values. To this end, aquatic ecosystems are good environments to observe the range of tolerance of benthic diatoms to environmental conditions due to their unique physical and chemical parameters. The aim of the present study was to propose the establishment of new, or altered, ecological indicator values, according to Van Dam et al. classification, of species of diatoms characteristic of three post-mining aquatic ecosystems. Methods. In total, 36 species were identified that were characteristic of three waterbodies: a salt aquatic complex (water outflow, a drainage ditch and a pond), a mined iron ore reservoir and a mined lignite reservoir. Their ecological indicator values were calculated using OMNIDIA software, and the environmental conditions prevailing in the studied ecosystems were determined. Of the 36 characteristic species, 16 lacking at least one assigned ecological indicator value were analysed further. The analysis identified three groups of selected characteristic species which showed a correlation, or lack of such, to the tested physical and chemical parameters. Results. Based on this multistage study of the autecology of characteristic diatoms, comprising an analysis of environmental conditions, literature analysis and reference ecological indicator values of other species, it is proposed that 32 ecological indicator values be established or adjusted for 16 species, and that Planothidium frequentissimum be excluded from water quality assessments.

scholarly journals Diatoms in Paleoenvironmental Studies of Peatlands

Quaternary ◽  
2020 ◽  
Vol 3 (2) ◽  
pp. 10
Author(s):  
Rafael Carballeira ◽  
Xabier Pontevedra-Pombal
Keyword(s):  
Water Chemistry ◽  
High Latitude ◽  
Aquatic Ecosystems ◽  
Good Condition ◽  
Southern Europe ◽  
Considerable Evidence ◽  
Close Relationship

The great diversity of diatoms in aquatic ecosystems and their close relationship with water chemistry make them one of the most informative and widely used biological proxies in paleoenvironmental studies of wetlands, except for peatland ecosystems. Currently, significant controversy still exists over the preservation of diatoms in peat. However, considerable evidence indicates that diatoms remain in good condition in minerotrophic peatlands, and they have been successfully used in paleoenvironmental studies in high-latitude regions and especially in Southern Europe.

scholarly journals Factors influencing the diets of four morphologically divergent fish species in nearshore marine waters

2004 ◽  
Vol 84 (4) ◽  
pp. 805-817 ◽  
Author(s):  
M. Hourston ◽  
M.E. Platell ◽  
F.J. Valesini ◽  
I.C. Potter
Keyword(s):  
Water Column ◽  
Fish Species ◽  
West Coast ◽  
Substrate Surface ◽  
Abundant Species ◽  
Calanoid Copepods ◽  
Cryptic Coloration ◽  
Small Crustacean ◽  
Competition For Food ◽  
Small Mouth

The dietary compositions of Atherinomorus ogilbyi (Atherinidae), Sillago schomburgkii (Sillaginidae), Lesueurina platycephala (Leptoscopidae) and Ammotretis elongatus (Pleuronectidae) in three nearshore habitats on the lower west coast of Australia, which varied in their exposure to wave energy and the extent to which they contain sea grass, have been determined. The dietary compositions of these four abundant teleosts differed, reflecting marked differences between the location in the water column, head and mouth morphology and feeding behaviour of these species. Atherinomorus ogilbyi, which has a relatively high and large mouth, fed mainly on planktonic invertebrates in the water column, while S. schomburgkii ingested predominantly benthic prey, such as polychaetes and bivalves, which it extracted from the sediment using its downward-protruding mouth. Lesueurina platycephala employed its large mouth, cryptic coloration and ambush feeding to target relatively large teleosts and invertebrates, while the small mouth and flattened body of Ammotretis elongatus facilitated the ingestion of small crustacean prey, e.g. cumaceans and amphipods, which live on the substrate surface. Atherinomorus ogilbyi consumed predominantly calanoid copepods, cladocerans and insects during the day and mainly amphipods at night, when the latter taxon became abundant in the water column. The dietary composition of each species underwent a similar pattern of size-related change, being most pronounced in L. platycephala during the day. The diets of A. ogilbyi and S. schomburgkii, the two species for which the data were most comprehensive, differed among habitats and seasons, reflecting differences in the densities of their main prey. Comparisons between the day-time diets of the above four species with those recorded previously for a further four abundant species in the same habitats during the day, show that food resources are well distributed among the main fish species in nearshore waters along the lower west coast of Australia. This feature, together with the size-related changes in the diets of the different species, reduces the potential for inter- and intraspecific competition for food by fish species in this environment.

Methylmercury biogeochemistry: a review with special reference to Arctic aquatic ecosystems

2014 ◽  
Vol 22 (3) ◽  
pp. 229-243 ◽  
Author(s):  
Igor Lehnherr
Keyword(s):  
Food Webs ◽  
Water Column ◽  
Human Health ◽  
Bottom Sediments ◽  
Aquatic Ecosystems ◽  
Marine Mammals ◽  
Primary Source ◽  
The Arctic ◽  
Arctic Biota

There has been increasing concern about mercury (Hg) levels in marine and freshwater organisms in the Arctic, due to the importance of traditional country foods such as fish and marine mammals to the diet of Northern Peoples. Due to its toxicity and ability to bioaccumulate and biomagnify in food webs, methylmercury (MeHg) is the form of Hg that is of greatest concern. The main sources of MeHg to Arctic aquatic ecosystems, the processes responsible for MeHg formation and degradation in the environment, MeHg bioaccumulation in Arctic biota and the human health implications for Northern Peoples are reviewed here. In Arctic marine ecosystems, Hg(II) methylation in the water column, rather than bottom sediments, is the primary source of MeHg, although a more quantitative understanding of the role of dimethylmercury (DMHg) as a MeHg source is needed. Because MeHg production in marine waters is limited by the availability of Hg(II), predicted increases in Hg(II) concentrations in oceans are likely to result in higher MeHg concentrations and increased exposure to Hg in humans and wildlife. In Arctic freshwaters, MeHg concentrations are a function of two antagonistic processes, net Hg(II) methylation in bottom sediments of ponds and lakes and MeHg photodemethylation in the water column. Hg(II) methylation is controlled by microbial activity and Hg(II) bioavailability, which in turn depend on interacting environmental factors (temperature, redox conditions, organic carbon, and sulfate) that induce nonlinear responses in MeHg production. Methylmercury bioaccumulation–biomagnification in Arctic aquatic food webs is a function of the MeHg reservoir in abiotic compartments, as well as ecological considerations such as food-chain length, growth rates, life-history characteristics, feeding behavior, and trophic interactions. Methylmercury concentrations in Arctic biota have increased significantly since the onset of the industrial age, and in some populations of fish, seabirds, and marine mammals toxicological thresholds are being exceeded. Due to the complex connection between Hg exposure and human health in Northern Peoples—arising from the dual role of country foods as both a potential Hg source and a nutritious, affordable food source with many physical and social health benefits—-reductions in anthropogenic Hg emissions are seen as the only viable long-term solution.

scholarly journals Depth-dependent molecular composition and photo-reactivity of dissolved organic matter in a boreal lake under winter and summer conditions

2013 ◽  
Vol 10 (11) ◽  
pp. 6945-6956 ◽  
Author(s):  
M. Gonsior ◽  
P. Schmitt-Kopplin ◽  
D. Bastviken
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Water Column ◽  
Early Spring ◽  
Boreal Lakes ◽  
Molecular Composition ◽  
Late Winter ◽  
Photochemical Degradation ◽  
Photo Degradation ◽  
Boreal Lake

Abstract. Transformations of dissolved organic matter (DOM) in boreal lakes lead to large greenhouse gas emissions as well as substantial carbon storage in sediments. Using novel molecular characterization approaches and photochemical degradation experiments we studied how seasonal patterns in water column stratification affected the DOM in a Swedish lake under early spring and summer conditions. Dissolved organic carbon (DOC) concentrations were consistently higher above the sediment when compared to surface waters throughout the sampling periods. Photobleaching alone could not explain this difference in DOC because the lake was covered by 40 cm-thick ice during late winter sampling and still showed the same DOC trend. The differences in the molecular diversity between surface DOM in winter and summer were consistent with ongoing photobleaching/decarboxylation and a possible bacterial consumption of photo-products. Additional photo-degradation experiments using simulated sunlight showed a production of highly oxidized organic molecules and low molecular weight compounds in all late winter samples and also in the deep water sample in summer. In the surface summer DOM sample, few such molecules were produced during the photo-degradation experiments, confirming that DOM was already photobleached prior to the experiments. This study suggests that photobleaching, and therefore also the ice cover during winter, plays a central role in surface DOM transformation, with important differences in the molecular composition of DOM between surface and deep boreal lake waters. The release of DOC from boreal lake sediments also contribute to this pattern. Photochemical degradation of DOM may be more extensive following ice-out and water column turnover when non-light exposed and thereby photosensitive DOM is photo-mineralized. Hence, the yearly DOM photo-mineralization may be greater than inferred from studies of recently light-exposed DOM.

Chemistry and stratification of Antarctic meltwater ponds II: Inland ponds in the McMurdo Dry Valleys, Victoria Land

2006 ◽  
Vol 18 (4) ◽  
pp. 525-533 ◽  
Author(s):  
M. Healy ◽  
J.G. Webster-Brown ◽  
K.L. Brown ◽  
V. Lane
Keyword(s):  
Water Column ◽  
Chemical Evolution ◽  
Late Winter ◽  
Dry Valleys ◽  
Vertical Profiles ◽  
Marine Aerosols ◽  
Biological Productivity ◽  
Gypsum Precipitation ◽  
Conductivity Increase ◽  
Victoria Land

Meltwater ponds in the Victoria Valley and in the Labyrinth at the head of the Wright Valley of Victoria Land were sampled in January (summer) and October (late winter) of 2004 to establish their geochemistry and stratification, and to compare this with that of coastal meltwater ponds at a similar latitude near Bratina Island. In summer, vertical profiles were measured in 14 ponds; 10 were thermally stratified (maximum ΔT = 11.5°C) and 12 demonstrated a conductivity increase (∼25x) in the lowest 10–20 cm of the water column. When 11 of these ponds were resampled in October, the ice columns were stratified with respect to conductivity and five ponds had highly saline (up to 148 mS cm−1), oxygenated basal brines present under the ice. Basal brines and summer melt waters were Na-Cl dominated, and Victoria Valley pond meltwaters were enriched in Ca relative to the Labyrinth ponds. Early gypsum precipitation directs the chemical evolution of residual brine during freezing. These ponds were enriched in NO3 relative to the coastal ponds at Bratina Island, due to dissolution of nitrate-bearing soil salts, and the reduced influence of marine aerosols and biological productivity on pond chemistry.

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