Steven P. Plesh’s research while affiliated with Southern Illinois University Carbondale and other places

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Publications (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.
Study area in lowland tundra near Utqiaġvik, Alaska, USA
Map developed using 2002 Quickbird imagery from the National Snow and Ice Data Center [30].
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.
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.
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.

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Organic matter sources and flows in tundra wetland food webs
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May 2023

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Steven P. Plesh

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Arctic lowland tundra is often dominated by wetlands. As numbers and types of these wetlands change with climate warming, their invertebrate biomass and assemblages may also be affected. Increased influx of nutrients and dissolved organic matter (DOM) from thawing peat may alter the relative availability of organic matter (OM) sources, differentially affecting taxa with disparate dependence on those sources. In five shallow wetland types (<40 to 110 cm deep) and in littoral zones of deeper lakes (>150 cm), we used stable isotopes (δ¹³C, δ¹⁵N) to compare contributions of four OM sources (periphytic microalgae, cyanobacteria, macrophytes, peat) to the diets of nine macroinvertebrate taxa. Living macrophytes were not distinguishable isotopically from peat that likely contributed most DOM. Within invertebrate taxa, relative OM contributions were similar among all wetland types except deeper lakes. Physidae snails consumed substantial amounts of OM from cyanobacteria. However, for all other taxa examined, microalgae were the dominant or a major OM source (39–82%, mean 59%) in all wetland types except deeper lakes (20‒62%, mean 31%). Macrophytes and macrophyte-derived peat, likely consumed mostly indirectly as DOM-supported bacteria, ranged from 18‒61% (mean 41%) of ultimate OM sources in all wetland types except deeper lakes (38–80%, mean 69%). Invertebrate consumption of microalgal C may often have involved bacterial intermediates, or a mix of algae with bacteria consuming peat-derived OM. High production of periphyton with very low δ¹³C values were favored by continuous daylight illuminating shallow depths, high N and P levels, and high CO2 concentrations from bacterial respiration of peat-derived DOM. Although relative OM sources were similar across wetland types except deeper lakes, total invertebrate biomass was much higher in shallow wetlands with emergent vegetation. Impacts of warming on the availability of invertebrate prey to waterbirds will likely depend not on shifts in OM sources, but more on changes in overall number or area of shallow emergent wetlands.

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