Fig 1.
Conceptual model of carbon flow through tundra wetland food webs.
The figure includes bacterial respiration of labile peat-derived DOC (dissolved organic carbon) leached from the active layer and adjacent thawing permafrost (region bounded by thick gray line). Resulting CO2 facilitates production of microalgae (“algae”, mostly periphyton) with no limitation by nutrients (N, P) or photoperiod.
Fig 2.
Study area in lowland tundra near Utqiaġvik, Alaska, USA.
Map developed using 2002 Quickbird imagery from the National Snow and Ice Data Center [30].
Table 1.
Means and SE of stable isotope values (δ13C, δ15N) of endmembers for organic matter sources used in mixing models, based on measured and reported values (S1 Table).
Fig 3.
Stable isotope scatterplots for each wetland type.
Endmembers for organic matter sources with trophic discrimination factors applied (Table 2) are also plotted (yellow circles). (A) Shallow Arctophila, (B) Deep Arctophila, (C) Shallow Carex, (D) Deep Carex, (E) Streams, and (F) Deep Open Lakes.
Table 2.
Trophic discrimination factors (TDFs, Δ13C, Δ15N) for macroinvertebrate consumers relative to organic matter sources (endmembers), and trophic route involved in the fractionation, in tundra wetlands.
Literature survey for the TDFs is in S2 Table. Values in parentheses are for endmembers (Table 1) plus the corresponding TDFs; resulting values are plotted in Fig 3.
Fig 4.
Relative contributions (mean percentages) of periphytic microalgae and of peat and macrophytes combined to diets of invertebrates across six wetland types.
For data values see S6 Table. Acar = Acari, Crus = Crustacea, Chir = Chironomidae, Plec = Plecoptera, Tric = Trichoptera, Tipu = Tipulidae, Cole = Coleoptera, Olig = Oligochaeta, Phys = Physidae). (A) Shallow Arctophila (n = 34), (B) Deep Arctophila (n = 26), (C) Shallow Carex (n = 36), (D) Deep Carex (n = 40), (E) Streams (n = 11), and (F) Deep Open Lakes. Asterisks (*) indicate taxa that were not detected in a given wetland type.
Fig 5.
Mean ± SE of invertebrate biomass (mg C m‒2) in benthic cores across six wetland types.
(Acar = Acari, Crus = Crustacea, Chir = Chironomidae, Plec = Plecoptera, Tric = Trichoptera, Cole = Coleoptera, Phys = Physidae,). (A) Shallow Arctophila (n = 14), (B) Deep Arctophila (n = 10), (C) Shallow Carex (n = 11), (D) Deep Carex (n = 7), (E) Streams (n = 6), and (F) Deep Open Lakes (n = 4). Total biomass of all invertebrates is annotated in each panel. Numerical values and results of statistical tests are in S7 Table.
Fig 6.
Mean ± SE of invertebrate biomass (mg C m‒3) in net sweeps through emergent vegetation across six wetland types.
Acar = Acari, Crus = Crustacea, Chir = Chironomidae, Plec = Plecoptera, Tric = Trichoptera, Cole = Coleoptera, Phys = Physidae). (A) Shallow Arctophila (n = 12), (B) Deep Arctophila (n = 10), (C) Shallow Carex (n = 11), (D) Deep Carex (n = 7), (E) Streams (n = 6), and (F) Deep Open Lakes (n = 4). Total biomass of all invertebrates is annotated in each panel. Numerical values and results of statistical tests are in S8 Table.