27 research outputs found
Water quality and planktonic microbial assemblages of isolated wetlands in an agricultural landscape
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Wetlands 31 (2011): 885-894, doi:10.1007/s13157-011-0203-6.Wetlands provide ecosystem services including flood protection, water quality
enhancement, food chain support, carbon sequestration, and support regional biodiversity.
Wetlands occur in human-altered landscapes, and the ongoing ability of these wetlands to
provide ecosystem services is lacking. Additionally, the apparent lack of connection of some
wetlands, termed geographically isolated, to permanent waters has resulted in little regulatory
recognition. We examined the influence of intensive agriculture on water quality and planktonic
microbial assemblages of intermittently inundated wetlands. We sampled 10 reference and 10
agriculturally altered wetlands in the Gulf Coastal Plain of Georgia. Water quality measures
included pH, alkalinity, dissolved organic carbon, nutrients (nitrate, ammonium, and phosphate),
and filterable solids (dry mass and ash-free dry mass). We measured abundance and relative size
distribution of the planktonic microbial assemblage (< 45 ÎĽm) using flow cytometry. Water
quality in agricultural wetlands was characterized by elevated nutrients, pH, and suspended
solids. Autotrophic microbial cells were largely absent from both wetland types. Heterotrophic microbial abundance was influenced by nutrients and suspended matter concentration.
Agriculture caused changes in microbial assemblages forming the base of wetland food webs.
Yet, these wetlands potentially support important ecological services in a highly altered
landscape.Funding was provided by the Joseph W.
Jones Ecological Research Center.2012-07-2
Massive mortality of invasive bivalves as a potential resource subsidy for the adjacent terrestrial food web
Large-scale mortality of invasive bivalves
was observed in the River Danube basin in the autumn
of 2011 due to a particularly low water discharge. The
aim of this study was to quantify and compare the
biomass of invasive and native bivalve die-offs
amongst eight different sites and to assess the potential
role of invasive bivalve die-offs as a resource subsidy
for the adjacent terrestrial food web. Invasive bivalve
die-offs dominated half of the study sites and their
highest density and biomass were recorded at the
warm water effluent. The density and biomass values
recorded in this study are amongst the highest values
recorded for aquatic ecosystems and show that a
habitat affected by heated water can sustain an extremely high biomass of invasive bivalves. These
mortalities highlight invasive bivalves as a major
resource subsidy, possibly contributing remarkable
amounts of nutrients and energy to the adjacent
terrestrial ecosystem. Given the widespread occurrence
of these invasive bivalves and the predicted
increase in the frequency and intensity of extreme
climatic events, the ecological impacts generated by
their massive mortalities should be taken into account
in other geographical areas as well.The authors are grateful to David Strayer for valuable comments on a previous version of the manuscript. Special thanks to the Danube-Ipoly National Park for the help in field work. Ronaldo Sousa was supported by the project "ECOIAS" funded by the Portuguese Foundation for the Science and the Technology and COMPETE funds (contract: PTDC/AAC-AMB/116685/2010)
Elevated aluminium concentration in acidified headwater streams lowers aquatic hyphomycete diversity and impairs leaf-litter breakdown.
Aquatic hyphomycetes play an essential role in the decomposition of allochthonous organic matter which is a fundamental process driving the functioning of forested headwater streams. We studied the effect of anthropogenic acidification on aquatic hyphomycetes associated with decaying leaves of Fagus sylvatica in six forested headwater streams (pH range, 4.3-7.1). Non-metric multidimensional scaling revealed marked differences in aquatic hyphomycete assemblages between acidified and reference streams. We found strong relationships between aquatic hyphomycete richness and mean Al concentration (r = -0.998, p < 0.0001) and mean pH (r = 0.962, p < 0.002), meaning that fungal diversity was severely depleted in acidified streams. By contrast, mean fungal biomass was not related to acidity. Leaf breakdown rate was drastically reduced under acidic conditions raising the issue of whether the functioning of headwater ecosystems could be impaired by a loss of aquatic hyphomycete species
Flood, drought and the inter-annual variation to the number and size of ponds and small wetlands in an English lowland landscape over three years of weather extremes
Coarse woody debris in temperate littoral zones: implications for biodiversity, food webs and lake management
The temporal dynamics of temporary pond macroinvertebrate communities over a 10-year period
Ponds support a rich biodiversity. This arises in part because of the number and heterogeneity of ponds spatially throughout the landscape. Studies of ponds suggest that distinct communities develop within individual ponds but most examples are based on shortterm 1- or 2-year surveys which cannot identify the effects of historic events upon contemporary communities. This study reports the development and turnover of the early summer macroinvertebrate communities in thirty small temporary ponds fromtheir creation in 1994 over 10 years to 2004. Distinct pioneer communities established in the first year of the ponds’ creation, the first 3 years dominated by a fauna associated with long summer dry phases. Then a sustained period of inundation lasting 27 months from summer 1997–1999 resulted in establishment of many taxa associated with permanent ponds and loss of some temporary pond species. The re-establishment of summer dry phases in 1999 was associated with the loss of some but not all of the permanent water taxa and re-colonisation by some temporary water species creating new communities combining these different elements. The communities were not a linear successional sequence; the communities that re-assembled following resumption of dry phases reflected the contingent history of each pond and the effects of historic events. The longer term nature of the study showed that the characteristic heterogeneity of pond invertebrate communities occurs through time as well as spatially and that the richness and variety of contemporary communities, which is often hard to explain fromsnap-shot studies, is partly the result of historic events