L. Gordon Goldsborough

The primary productivity of benthic and planktonic algae in a prairie wetland under controlled water-level regimes

There have been few measurements of primary productivity by benthic (periphytic) and planktonic algae in prairie wetlands so their quantitative importance relative to other primary producers is largely unknown. We measured the daily productivity (inorganic carbon assimilation per m2 of wetland area) of phytoplankton, epipelon, epiphyton, and metaphyton in ten wetland cells in Delta Marsh, Manitoba over a five-year period. Water levels in the cells were manipulated so that some cells had normal water levels for the wetland, while water depths increased 30 cm or 60 cm in other treatments. With increasing water depth, phytoplankton productivity increased while that of epipelon, epiphyton, and metaphyton decreased. Metaphyton was the largest contributor to total algal productivity (70%), followed by epiphyton (23%), phytoplankton (6%), and epipelon (1%). Phytoplankton had the highest photosynthetic efficiency (C assimilated per unit chlorophyll), despite being a minor contributor to total productivity. Variations in P-I parameters (α, β, Ik, and Pmax) were considerable, possibly due to temporal and spatial fluctuation in the abiotic environment. Algal productivity was comparable to that of submersed and emergent macrophytes, suggesting that algae are probably important resources in supporting food webs in prairie wetlands.

Response of benthic and planktonic algal biomass to experimental water-level manipulation in a prairie lakeshore wetland

The quantitative contribution of benthic (periphytic) and planktonic algae to primary production in prairie wetlands is largely unknown, as is their response to the fluctuations in water level that characterize such systems. We measured the biomass (chlorophyll-a m−2 of wetland area) of phytoplankton, epipelon, epiphyton, and metaphyton in Delta Marsh, Manitoba as part of a five-year study in which diked, drawn down cells were reflooded to the normal level of the wetland, or to a depth 30 cm or 60 cm deeper. Our objective was to investigate the effects of flooding depth on algal biomass and the relative contributions by each of the four algal assemblages. Floating metaphyton mats flourished in all cells after flooding, contributing about 87% of total algal biomass. Epiphytes contributed 11% of biomass, and epipelon and phytoplankton each contributed 1%. Emergent macrophyte density was reduced by flooding, leading to increases in open water area. The wetland cells changed gradually over the study period from an early “open wetland” to a “sheltered wetland.” In late stages of the study, phytoplankton became more abundant as the cells proceeded to a “lake wetland” state.

Interactions Between Algae (Selenastrum capricornutum) and Pesticides: Implications for Managing Constructed Wetlands for Pesticide Removal

This laboratory study examined the interactions between an algal species found in wetlands (Selenastrum capricornutum) and two agricultural pesticides (atrazine and lindane). Pesticide additions had a positive effect on the chlorophyll a concentrations of the treatments. The presence of algae decreased the aqueous persistence of both pesticides. It is speculated that the algae either provided sites for pesticide sorption or facilitated pesticide degradation.

Boreal diatom ponds: A rare wetland associated with nesting whooping cranes

This paper documents and characterizes a rare form of boreal wetland associated with the nests of whooping cranes, an endangered species. Diatom ponds are found in wetlands in association with bulrush marshes. They are shallow (<50 cm deep) and vary in size from 10 to >1000 m in diameter, may evaporate down to diatom muck by late summer, are strongly influenced by dissolution of gypsum, and are circumneutral to alkaline and high in sulphates. Aquatic macrophytes are few. Pond waters are clear, and the predominant primary producers are a benthic diatom community that gives the ponds a characteristic yellow color (viewed from the air). As the diatom ponds dry, they change color from yellow to pink (when water table is at the surface) to cream (due to a dried diatom and sulphate crust). Diatomaceous earth or sedimentary peat underlies the ponds, which exist in a dynamic relationship with bulrush marshes, wet meadows, fens, and bogs. In the U.S. wetland classification system, diatom ponds fit most nearly within the palustrine, unconsolidated bottom, aquatic bed type. In the Canadian wetland classification system, the diatom ponds might fit in the marsh/shallow open water complex, with a new distinction at the type level. The association between nesting cranes and diatom ponds may be due to a combination of factors such as long sight lines for detection of predators, the proximity of bulrush (their favored nesting material), and use of the ponds for feeding.