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The dynamics of phosphorus in lacustrine sediments : contents and fractions in relation to lake trophic state and chemical composition of bottom deposits

Rzepecki M.

Polish Journal of Ecology

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2010

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Vol. 58, nr 3

409-427

EN

Phosphorus is still recognized as the element driving the matter cycling in freshwater ecosystems. It is the key nutrient in productivity and eutrophication process of lakes and reservoirs. The bottom sediments cumulatively formed inside and in-shore of lakes play a crucial role in accumulation/sorption of phosphorus organic compounds, as well as in release/desorption of the compounds available for uptake by producers and microbial heterotrophs. These two opposite processes are dependent on the chemical composition of sediments and on the site conditions (like oxygen, pH) in over-bottom layers. About three hundred of the sediment surface layer samples were taken from the lacustrine habitats in a variety of lakes typical for postglacial landscape (Masurian Lakeland, Poland): profundal and littoral zones in lakes forming a trophic gradient including a humic lake, river/lake ecotone zone and wetland sites adjacent to lake shoreline. The contents of Ca, Fe, Mg, Mn and Al were analysed as well as the amount of total P (TP) and its three basic groups i.e. easily exchangeable, hardly exchangeable and non-exchangeable fractions. It was found that the sediments of humic lake had the most different, distinct chemical composition and contained very small amounts of Fe, Mn, Mg and Ca - nearly 30 times less than sediments of other, non-humic lakes. These sediments contained the most of organic matter and similar (as in non-humic lakes) amounts of TP whose dominant part (80%) consists of hardly exchangeable organic fraction. Sediments of lakes forming the trophic gradient along the small (15 km long) river (Jorka River) showed consistent changes in the chemical composition. Sediments of lakes situated up the river system (meso- and meso-eutrophic lakes) had higher content of organic matter and Ca but lower content of TP, Fe and Mg than sediments of lakes in the lower part of the river system (eutrophic and hypertrophic lakes). The content of these elements was also higherin profundal than in littoral sediments. Significantly higher content (40-70%) of non-exchangeable P was found in sediments of eutrophic and hypertrophic lakes than in sediments of meso- and meso-eutrophic lakes (30-60%) in both the littoral and profundal zones. Sediments of the river-lake-river ecotones (Krutynia River) showed also the consistent changes of element content along the river flow through the lake. The amount of TP was lower in riverine sediments down and upstream the lake than in lake sediments. Organic matter and Fe contents were lower and Ca, Mg, Mn and Al contents were higher in river-lake-river ecotones or similar to those in sediments of the lakes from the trophic gradient. Easily exchangeable phosphorus prevailed in lake sediments; TP in riverine sediments was dominated by hardly exchangeable and non-exchangeable forms and was similar to that found in littoral sediments of lakes from the trophic gradient. Inshore wetland sediments were characterized by a highcontent of organic matter - higher than in littoral and profundal sediments of lakes forming the trophic gradient. The content of Ca, Mg, Mn and Fe was two to five times lower than in sediments of lakes from the trophic gradient but similar to sediments of humic lake. They also contained less TP than profundal sediments from the trophic gradient and humic lakes but had similar content to littoral and riverine sediments. As in the case of profundal and riverine sediments, non-exchangeable and hardly exchangeable P fractions dominated TP content in wetland inshore sediments. Almost all phosphorus a ccumulated in these sediments is associated with a high organic matter deposition. The study results concern the basic types of lake and lacustrine habitats representative for the postglacial landscape of north and north-east Europe. A significant diversity of sediment origin, chemical composition and phosphorus amount and its potential mobility was found among the sediment types. The wetland and humic sediments appeared to be active in cumulation and stabilisation of P resources while sediment of nonhumic, trophic lakes (especially in profundal zoners) are the active sites for P release and sorption processes.

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The DGPS system improves survey of offshore depths

Banachowicz A., Dołgopołow A., Kozłowski Z., Wolski A., Wolski A.

Reports on Geodesy

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2006

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z. 1/76

275-279

EN

The article presents the results of research on possible applications of corrections from the reference DGPS station DGPS station at Dzwinow during measurements of depth changes in an offshore area.

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Formy osadu w strefie zmywu i najpłytszego przybrzeża na przykładzie wybrzeża Bałtyku między Mrzeżynem i Dźwirzynem

Kurowski L.

Przegląd Geologiczny

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2002

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Vol. 50, nr 5

458-464

PL

W czasie prowadzenia obserwacji stan Bałtyku, przy słonecznej pogodzie, wahał się między 0 a 3, co odpowiadało wiatrom o prędkości od 0,0-0,5 m/s (cisza) do 5,3-7,4 m/s (wiatr umiarkowany). Formy osadu generowane w strefie zmywu oraz przylegającym bezpośrednio do niej pasie przybrzeża najlepiej można było obserwować w czasie spokojnego morza (0-1), tzn. przy powiewach nie przekraczających prędkości 1,7 m/s. W tych warunkach powstawało wiele drobnych, najczęściej nietrwałych struktur, których genezę na stoku plaży można wiązać z erozyjno-akumulacyjną działalnością zmywu wstępującego i powrotnego, a w strefie przybrzeża z działalnością małych (oscylacyjnych lub translacyjnych) fal i słabych prądów wzdłużbrzegowych. W pracy tej, ze strefy zmywu, opisane zostały: lineacja prądowa, wałki falowe, ślady kropel, różne odmiany bruzd ściekowych i śladów opływania, a także bąble pogazowe. Ze strefy przybrzeża, natomiast opisano różne typy ripplemarków i poziomy bruku falowego. Praca zawiera także ciekawe przykłady erozji, występującego w obszarze badań pokładu torfu, w formie nisz erozyjnych powstających na poziomie dna przybrzeża i mis erozyjnych (eworsyjnych?) tworzących się na jego powierzchni. Nieustanne falowanie na granicy brzegu i przybrzeża ma ogromny wpływ na różnorodność i zmienność tworzących się tutaj form osadu. Każda następna fala docierająca do brzegu pozostawia na piasku swoisty "autograf". W związku z tym, bez względu na fakt czy opisane formy rozpoznajemy w osadach kopalnych , czy we współczesnych są one bardzo dobrymi wskaźnikami środowiska sedymentacji.

EN

The studies were carried out during sunny weather when the Baltic Sea state varied from 0 to 3, which corresponded to the wind force from 0.0-0.5 m/s (calm) to 5.3-7.4 m/s (moderate wind). Sediment forms generated in the swash zone and adjacent belt of the nearshore could be best observed when the sea was calm (0-1), i.e. when gusts of wind did not exceed 1.7 m/s. Under such conditions a certain number of small and usually undurable forms were generated. Their formation on the beach slope can be explained in terms of erosional and accumulative action of swash and backswash while their presence in the nearshore relates to the action of small waves (oscillatory or translatory) and weak longshore currents. The paper describes several forms from the swash zone, e.g. current lineation, swash marks, drop imprints, crescent marks, rill marks, air-escape pits. Some other forms, such as different types of ripple marks and wave pavements, were described from the nearshore. Also, unusual examples of the erosion of a peat seam (present in the study area) as erosion cavities and evorsion (?) bowls are discussed. Constant waving between the shore and the nearshore has a strong influence on the diversity and variety of sediment forms originated in this zone. Every next wave that reaches the shore leaves some sort of,, imprint" on the sand. That is why, no matter whether the described forms are recognized in rocks or in contemporary sediments, they are very good indicators of sedimentary environment.