scholarly journals Zooplankton structure in two interconnected ponds: similarities and differences

2016 ◽  
Vol 74 (1) ◽  
pp. 6-13 ◽  
Author(s):  
Maria Špoljar ◽  
Tea Tomljanović ◽  
Tvrtko Dražina ◽  
Jasna Lajtner ◽  
Helena Štulec ◽  
...  
Keyword(s):  
Littoral Zone ◽  
Trophic Structure ◽  
Submerged Macrophytes ◽  
Fish Predation ◽  
Predation Pressure ◽  
Summer Period ◽  
Zooplankton Structure ◽  
Similarities And Differences ◽  
Abundance And Diversity ◽  
Interconnected Ponds

Abstract The research of zooplankton diversity, abundance and trophic structure was conducted during the summer period in pelagial zone on the longitudinal profile of the Sutla River Backwater. Investigated site consists of two interconnected basins: transparent Upper Basin with submerged macrophytes and turbid Lower Basin without macrophytes in the littoral zone. In the Upper Basin, abundance and diversity of zooplankton in the pelagial was higher in comparison to the Lower Basin, with prevailing species of genus Keratella as microfilter-feeder, and genera of Polyartha and Trihocerca as macrofilter-feeder rotifers. On the contrary, in the Lower Basin, crustaceans dominated in abundance. Microfilter-feeder cladoceran (Bosmina longirostris) and larval and adult stages of macrofilter-feeder copepod (Macrocyclops albidus) prevailed in the Lower Basin. Fish predation pressure was more pronounced in the pelagial of the Upper Basin, indicated by low cladoceran abundance in the surface layer. Although the studied basins were interconnected, results indicate significant (Mann-Whitney U test, p < 0.05) differences in the zooplankton structure as a potential result of the macrophyte impact on environmental conditions and fish predation pressure.

scholarly journals Brook trout (Salvelinus fontinalis) extinction in small boreal lakes revealed by ephippia pigmentation: a preliminary analysis

2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Alexandre Bérubé Tellier ◽  
Paul E. Drevnick ◽  
Andrea Bertolo
Keyword(s):  
Brook Trout ◽  
Fish Assemblages ◽  
Salvelinus Fontinalis ◽  
Sediment Cores ◽  
Experimental Studies ◽  
Cost Effective ◽  
Fish Predation ◽  
Boreal Lakes ◽  
Predation Pressure ◽  
Trout Population

<p>Ephippium pigmentation is a plastic trait which can be related to a trade-off between visual predation pressure and better protection of cladoceran eggs against different types of stress. Experimental studies showed that planktivorous fish exert a greater predation pressure on individuals carrying darker ephippia, but little is known about the variation of ephippium pigmentation along gradients of fish predation pressure in natural conditions. For this study, our experimental design included four small boreal lakes with known fish assemblages. Two of the lakes have viable brook trout (<em>Salvelinus fontinalis</em>) populations, whereas the other two lakes experienced brook trout extinctions during the 20<sup>th</sup> century. Cladoceran ephippia were extracted from sediment cores at layers corresponding to the documented post- extinction phase (1990's) and from an older layer (1950's) for which the brook trout population status is not known precisely. Our first objective was to determine whether brook trout extinction has a direct effect on both ephippium pigmentation and size. Our second objective was to give a preliminary assessment of the status of brook trout populations in the 1950's by comparing the variation in ephippia traits measured from this layer to those measured in the 1990's, for which the extinction patterns are well known. Cost-effective image analysis was used to assess variation in pigmentation levels in ephippia. This approach provided a proxy for the amount of melanin invested in each ephippium analysed. Our study clearly shows that ephippium pigmentation may represent a better indicator of the presence of fish predators than ephippium size, a trait that showed a less clear pattern of variation between lakes with and without fish. For the 1990's period, ephippia from fishless lakes were darker and showed a slight tendency to be larger than ephippia from lakes with brook trout. However, no clear differences in either ephippium size or pigmentation were observed between the 1990's and 1950's layers within each lake. This suggests that brook trout extinction already occurred before the 1950’s, or that brook trout population abundance was already extremely low before and after the 1990’s. Our preliminary study shows that ephippium pigmentation can be used as a tool to quickly assess present and past predation levels on zooplankton when only sediment samples are available.</p>

scholarly journals Temperature and Circulation Dynamics in a Small and Shallow Lake: Effects of Weak Stratification and Littoral Submerged Macrophytes

Water ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 128 ◽  
Author(s):  
Péter Torma ◽  
Chin Wu
Keyword(s):  
Velocity Profile ◽  
Shallow Lake ◽  
Littoral Zone ◽  
Submerged Macrophytes ◽  
Layer Structure ◽  
Maximum Velocity ◽  
Mean Flow ◽  
Circulation Patterns ◽  
Weak Stratification ◽  
Circulation Dynamics

In this paper, the effects of littoral submerged macrophytes on weak stratification conditions in a small and shallow lake are investigated. Diverse submerged macrophytes occupying a large portion of the littoral zone act as resistance to water motions and affect lake hydrodynamics. Strong solar radiation and mild wind forcing typically occurring during the summer season result in weak stratification characterized by a diurnal cycle with a temperature differential of 1–3 °C. Temperature and circulation dynamics of a small and shallow lake are depicted by extensive field measurements and a three-dimensional non-hydrostatic model with a generic length scale (GLS) approach for the turbulence closure and drag forces induced by macrophytes. Results show that the effects of macrophytes on velocity profiles are apparent. In the pelagic area, the circulation patterns with and without macrophytes are similar. The velocity profile is generally characterized by a two-layer structure with the maximum velocity at both the water surface and the mid-depth. In contrast, inside the littoral zone, the mean flow is retarded by macrophytes and the velocity profile is changed to only one maximum velocity at the surface with a steeper decrease until 2.0 m depth and another slight decrease to the lake bottom. From the whole lake perspective, littoral macrophytes dampen the horizontal water temperature difference between the upwind side and download side of the lake. Macrophytes promote a stronger temperature stratification by retarding mean flows and reducing vertical mixing. Overall, this study shows that the temperature structures and circulation patterns under weak stratification conditions in a small and shallow lake are strongly affected by littoral vegetation.

scholarly journals Methodology for Carrying out Measurements of the Tombolo Geomorphic Landform Using Unmanned Aerial and Surface Vehicles near Sopot Pier, Poland

2020 ◽  
Vol 8 (6) ◽  
pp. 384 ◽  
Author(s):  
Cezary Specht ◽  
Oktawia Lewicka ◽  
Mariusz Specht ◽  
Paweł Dąbrowski ◽  
Paweł Burdziakowski
Keyword(s):  
Littoral Zone ◽  
Summer Period ◽  
Reliable Determination ◽  
Debris Accumulation ◽  
Measuring Devices ◽  
Sea Currents ◽  
Spatio Temporal ◽  
Narrow Belt ◽  
Sand And Gravel

The human impact on the ecosystem has been particularly evident in the last century; it transforms the Earth’s surface on an unprecedented scale and brings about irreversible changes. One example is an oceanographic phenomenon known as a tombolo, i.e., a narrow belt connecting the mainland with an island lying near the shore formed as a result of sand and gravel being deposited by sea currents. The phenomenon contributes to an increase in the biogenic substance content in the littoral zone, which leads to increased cyanobacteria blooming in the summer period. Moreover, the debris accumulation in the littoral zone results in the mud formation, which makes the beach landscape less attractive. One of the main features of the tombolo phenomenon is its variability of shape, which includes the form of both the shore and the seabed adjacent to it. Therefore, to describe its size and spatio-temporal variability, it is necessary to apply methods for geodetic (the land) and hydrographic (the sea) measurements that can be carried out in different ways. The aim of the paper is to present the methodology for carrying out measurements of the tombolo oceanographic phenomenon using Unmanned Aerial Vehicles (UAV) and Unmanned Surface Vehicles (USV) on the example of a waterbody adjacent to the Sopot pier. It also presents the results of surveys carried out in November 2019 within this area. The study demonstrated that the integration of two measuring devices whose development began in the second decade of the 20th century, i.e., UAVs and USVs, enables accurate (even up to several centimeters) and reliable determination of the scale and variability of the phenomena occurring in the littoral zone.

Species Replacements among Orconectes Crayfishes in Wisconsin Lakes: The Role of Predation by Fish

1993 ◽  
Vol 50 (7) ◽  
pp. 1484-1488 ◽  
Author(s):  
Guy T. DiDonato ◽  
David M. Lodge
Keyword(s):  
Littoral Zone ◽  
Carapace Length ◽  
Fish Predation ◽  
Species Selection ◽  
Adult Size ◽  
Selective Predation ◽  
Native Fishes ◽  
Native Crayfish ◽  
Species Replacements

To test the role of size- and species-selective predation by fishes in species replacements among congeneric crayfishes in northern Wisconsin lakes, we tethered the same three sizes of each of three species of Orconectes at six sites in the littoral zone of Trout Lake, Vilas County, Wise. Small crayfish (15–18 mm carapace length) were removed by fish at significantly higher rates than medium (23–25 mm) and large (33–35 mm) crayfish. Orconectes virilis was removed at significantly higher rates than O. propinquus and O. rusticus. These species-selection results suggest that predation by native fishes contributes to the previously documented replacement of the native crayfish O. virilis by the exotic crayfishes O. propinquus and O. rusticus. In combination with the observations of others that adult size of O. rusticus is typically larger than that of O. propinquus in northern Wisconsin lakes, our size-selection results suggest that fish predation may also hasten the ongoing replacement of O. propinquus by O. rusticus. Thus, fish predation is probably an important mechanism driving the replacement of O. virilis by O. propinquus and the replacement of both congeners by O. rusticus.

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