Assessing ecological effects of glacial meltwater on lakes fed by the Greenland Ice Sheet: The role of nutrient subsidies and turbidity

Figures & data

Table 1. Lake characteristics and sampling information. The only samples collected in 2016 were Chl a for the three indicated GF lakes and surface sediments from GL6. Surface sediments were used for both diatom counts and Psenner extractions

Lake	Type	Area (km^2)	Location (Deg Min Sec N & W)	Anchored depth (m)	Years Sampled	Surface Sediment Collection Location
GL4	GF	0.44	67°09ʹ28”, 50°08ʹ44”	28	2015, 2016	Shore
GL5	GF	0.13	67°09ʹ03”, 50°07ʹ26”	17	2015, 2016	Basin
GL6	GF	0.05	67°08ʹ43”, 50°07ʹ29”	5.5	2015, 2016	Basin
GL7	GF	0.08	67°09ʹ33”, 50°06ʹ18”	Sampled from shore	2015	Shore
SS901	SF	0.12	67°07ʹ52”, 50°14ʹ03”	14	2015	Basin
SS903	SF	0.36	67°07ʹ45”, 50°10ʹ19”	21.5	2015	Basin
SS906	SF	0.09	67°07ʹ09”, 50°15ʹ20”	18	2015	Basin
SS909	SF	0.06	67°07ʹ42”, 50°14ʹ59”	15	2015	Basin

Figure 1. Map of study area, showing the locations of lakes relative to the Greenland Ice Sheet. Glacially fed (GF) lakes are indicated in light blue, and snow- and groundwater-fed (SF) lakes are dark blue

Figure 2. Physical and chemical properties of glacially fed (GF) and snow- and groundwater-fed (SF) lakes. Significant differences are indicated by *** (p < 0.001), ** (p = 0.001–0.01), or * (p = 0.01–0.05)

Figure 3. Principal component analysis (PCA) plot of physical and chemical properties of glacially fed (GF) and snow- and groundwater-fed (SF) lakes. GF lakes are labeled in red, SF lakes in black, and environmental variables in blue

Figure 4. Sequential sediment extractions for aluminum (Al; A–E), iron (Fe; F–J), and phosphorus (P; K–O) from glacially fed (GF) and snow- and groundwater-fed (SF) lake sediments. Significant differences are indicated by *** (p < 0.001), ** (p = 0.001–0.01), or * (p = 0.01–0.05)

Figure 5. Ratios of glacially fed (GF) and snow- and groundwater-fed (SF) lake sediment extractions. Phosphorus (P) release from sediments during anoxia is predicted if aluminum to iron (Al:Fe_{NH4Cl+BD+NaOH}) is below 3 and if aluminum to phosphorus (Al_NaOH:P_NH4Cl+BD) is below 25

Figure 6. Principal component analysis (PCA) plot of sequential extractions from glacially fed (GF) and snow- and groundwater-fed (SF) lake sediments. GF lakes are labeled in red, SF lakes in black, and extraction variables in blue. Percent organic matter = %OM

Table 2. Microbial extracellular enzyme activities (EEAs) of glacially fed (GF) and snow- and groundwater-fed (SF) lakes. EEA units are μmol mL⁻¹ h⁻¹. Significant differences (p ≤ 0.05) between lake types are indicated by an asterisk (*)

Lake Type	BG	NAG + LAP	AP	BG:(NAG + LAP)	BG:AP
GF	<0.01*	<0.01*	0.17	0.05*	<0.01*
SF	0.01	0.23	0.19	0.41	0.48

Figure 7. Chlorophyll a (Chl a) as a measure of algal biomass (a) and average diatom species richness, determined by rarefaction analysis (b). Significant differences are indicated by *** (p < 0.001), ** (p = 0.001–0.01), or * (p = 0.01–0.05)

Figure 8. Canonical correspondence analysis (CCA) plot of diatom species distribution (right panel) across glacially fed (GF) and snow- and groundwater-fed (SF) lakes (left panel), determined by nutrient and turbidity variables (middle panel). Turb = turbidity and Cond = conductivity