Surface and subsurface flows of nutrients in natural and human impacted lake catchments on Broknes, Larsemann Hills, Antarctica

Abstract

Abstract:This study aimed to use nutrients in lake inflows as proxies for assessing human impact and separating this from natural transformations of material in the soil active layer. Nutrients, conductivity and δ 18 O were monitored in surface and subsurface (using ceramic tipped piezometers) lake inflows during summer in near natural and human impacted catchments. The nutrient levels were highly variable but generally higher during the last weeks of the flow, in both subsurface waters and in human impacted catchments. Up to 2000 µgN l -1 subsurface dissolved inorganic nitrogen (DIN) was measured in human impacted catchments but only 315 µg N l -1 in natural catchments. Subsurface levels of dissolved reactive phosphorus (DRP) were up to 310 µgP l -1 in natural catchments and up to 108 µgP l -1 in human impacted catchments. The maximum levels of both DIN and DRP in surface inflows were much higher in human impacted than in natural catchments. Conductivity and δ 18 O data showed general enrichment of snowbank meltwater presumably through evaporation from the active layer. This combined with fluctuating nutrient levels in catchment waters indicated that soil brines and decaying organic matter of natural and human origin were possible sources for nutrients and other salts. Marked salinization and substantially increased DIN levels near the research stations indicated that lake waters were receiving nutrients generated by humans.

Abundant and Rare Bacterioplankton in Freshwater Lakes Subjected to Different Levels of Tourism Disturbances

“…Besides, one study recently assessed the influence of tourism on surface-water quality and reported that activities related to tourism in a river resulted in higher concentrations of TN and TP in the midstream and downstream areas than upstream [12]. Although natural processes may contribute to increased nutrient levels within aquatic systems [58], the moderate-and high-anthropogenic-disturbance lakes involved in our study indicated that anthropogenically derived sources were responsible for a significant proportion of total nutrient input. The high-anthropogenic-disturbance lakes in our study may be suffering from considerably serious environmental degradation.…”

Freshwater fluxes in the Weddell Gyre: results from δ 18 O

“…For SIM (figure 4c), highest percentages are visible in the surface layers associated with the recent seasonal decrease in sea-ice extent (approx. stations [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85]. This reaches a maximum of 1.8% at station 84, equivalent to 0.8 m of sea-ice derived freshwater in an 85 m thick Surface Water (neutral density γ n < 27.55) layer.…”

Evidence for a lacustrine faunal refuge in the Larsemann Hills, East Antarctica, during the Last Glacial Maximum

“…The lake is brackish, covered with ice for 10 months of the year and seasonally stratified (Kaup & Burgess, 2002). The lake becomes completely anoxic during winter, but oxygenated after ice melt out during summer mixing (Kaup & Burgess, 2002), while conductivity is considerably higher than other Larsemann Hills lakes (9160 μ S cm −1 cf. <4200 μ S cm −1 ) (Hodgson et al.…”