Nektonic invertebrate abundance and distribution at the emergent vegetation-open water interface in the Delta Marsh, Manitoba, Canada

Abstract

Water temperatures were constant across the interface through much of the year. By mid-summer, hypoxic conditions prevailed within the water column in the cattail stand. Algae levels were similar across the interface throughout much of the year, with peaks occurring just inside the interface in June and July. Early in the season, there was a trend for higher nektonic invertebrate numbers within the cattail stands of both bays. By late August, there were similar total invertebrate numbers across the interface. Cladocera and ostracod numbers were higher within the cattail stands during June and July; during the same periods, corixid levels were higher in the open water sites. The low oxygen levels within the cattail stands during the summer may reduce predation by fish and other predators that cannot tolerate low oxygen levels. This may explain the higher numbers of prey species like cladocerans and ostracods within the cattail stands during mid-summer. The presence of algal or detrital food resources seemed to have little influence on invertebrate abundance across the interface during this study. Peaks in invertebrate abundance did not occur at the emergent vegetation-open water interface during any of the sampling periods in this study. The high invertebrate diversity and abundance in interspersed wetland habitat may be related more to the mixture of habitat types rather than the amount of interface present.

Impacts of Environmental Variables on a Phytoplankton Community: A Case Study of the Tributaries of a Subtropical River, Southern China

“…Studying the succession of a phytoplankton community has important theoretical and practical significance. Numerous research studies in different rivers have showed that temperature, light and nutrients are important factors impacting the succession of the phytoplankton community [2][3][4]. In natural water bodies, these factors often simultaneously determine the succession of the phytoplankton community.…”

“…The aims of our research were (1) to verify differences in the trophic states and phytoplankton community structures in three tributaries of the Dongjiang River; (2) to examine how the phytoplankton community variation is influenced by environmental factors; and (3) to summarize the seasonal variation in the phytoplankton communities of the three rivers.…”

Seasonal and diurnal hydro-chemical variations in a recreated reed bed

“…Seybold et al, 2002 andMurkin et al, 1992) and shallow lakes (e.g. Ansa-Asare et al, 1999), few studies have been conducted on the increasing number of re-created wetland environments where rapid development of habitat and active management are key characteristics.…”

Migrating and breeding bird use of restored shallow lakes in Iowa

“…The importance of emergent vegetation has been well documented for waterbirds that use wetlands during migration and breeding . Emergent vegetation provides shelter and a substrate for invertebrates (Murkin et al 1992), and there is evidence that invertebrate abundance is greater when open water is interspersed with emergent vegetation (Voigts 1976). Indeed, waterbird abundance and species richness tend to be greatest when emergent vegetation and open water is present at a 1:1 ratio , Kaminski and Prince 1984.…”

“…With prolonged flooding, the invertebrate community changes, submergent vegetation proliferates, and the emergent vegetation may eventually begin to die back and become more patchily distributed due to inundation and muskrat activity Davis 1978, Murkin and. Overall, this results in habitat that is favored by nesting by marsh birds, particularly during this degenerating phase when openings in the robust vegetation become numerous (Murkin et al 1992, Murkin and Ross 1999. Yellow-headed Blackbirds and Marsh Wrens, obligate wetland breeders, build nests using robust vegetation , Twedt and Crawford 1995.…”