Functional Changes in Littoral Macroinvertebrate Communities in Response to Watershed-Level Anthropogenic Stress

Watershed-scale anthropogenic stressors have profound effects on aquatic communities. Although several functional traits of stream macroinvertebrates change predictably in response to land development and urbanization, little is known about macroinvertebrate functional responses in lakes. We assessed functional community structure, functional diversity (Rao’s quadratic entropy) and voltinism in macroinvertebrate communities sampled across the full gradient of anthropogenic stress in Laurentian Great Lakes coastal wetlands. Functional diversity and voltinism significantly decreased with increasing development, whereas agriculture had smaller or non-significant effects. Functional community structure was affected by watershed-scale development, as demonstrated by an ordination analysis followed by regression. Because functional community structure affects energy flow and ecosystem function, and functional diversity is known to have important implications for ecosystem resilience to further environmental change, these results highlight the necessity of finding ways to remediate or at least ameliorate these effects

The [Beta] and [Beta]-delayed neutron decay studies of 75CU and 77CU

β decay studies of nuclei at the limits of stability are essential in evaluating the physical aspects behind the structural changes, particle configurations and interactions in neutronor proton-rich systems. Isobarically purified beams were used at the Holifeld Radioactive Ion Beam Facility at Oak Ridge National Laboratory to study the β decays of 75Cu and 77Cu. Two different experiments were performed. In the first study, only concernig the decay of 77Cu, the 25-MV tandem accelerated ions were time-tagged using a micro-channel plate detector, passed through a six-segment ion chamber, and implanted on the tape of a moving tape collector. The passage through an ion chamber insured the ion identification by energy loss in the six segments. The Low Energy Radioactive Ion Beam Spectroscopy Station consisting of a universal detector support with four Ge clover detectors, two â detectors and a moving tape collector, was used in the second experiment. Bypassing of the tandem accelerator gave a factor of 10 gain in beam intensity for both 75Cu and 77Cu. These experiments resulted in considerable information on the previously unknown level structure of 75Zn with some 120 γ-ray transitions placed in a level scheme containing 59 levels including two above the neutron separation energy. We have also identified the previously unknown 1/2− isomeric state at 127 keV. A total of 64 γ rays were placed in a level scheme for 77Zn containing 35 excited states including one state above the neutron separation energy, while two γ rays were observed for the βn branch to states in 76Zn. The growth and decay curves of some prominent γ rays indicate a single β-decaying state with a half-life of 480(9) ms. The decay pattern for 77Cu, with observed feeding of 8(3)% to the 7/2+ 77Zng and 6(3)% to the 1/2− 77Znm, in contrast to the large feeding observed for decay of πp3/2 73Cug to 1/2− 73Zng, strongly suggests a πf5/2 ground state for the studied 77Cu activity. Results will be presented and the prospects for future possible studies will also be discussed

Macroinvertebrate functional diversity (Rao’s Q) as a function of development and agricultural stress in the watershed.

<p>Note that maximum values of the functional trait are observed mostly below a certain proportion of development (around mid-point of the y-axis, corresponding to 10% untransformed % development), indicating the over-riding contribution of that stressor; and if high values are observed at the higher levels of development, those occur only at sites with minimal agriculture. *[figure footnote] Contour lines divide the figure into a region where values are higher than they are on the contour line itself and a region where they are lower; values change across the line but not along the contour line, and the gradient is larger where contour lines are packed closer together.</p

A map of the study sites in the coastal wetlands of the Laurentian Great Lakes, overlaid with the land-use stressor gradient for a) agriculture and b) development.

<p>A map of the study sites in the coastal wetlands of the Laurentian Great Lakes, overlaid with the land-use stressor gradient for a) agriculture and b) development.</p

Relative abundance of long-lived taxa (uni-, semi- and merovoltine) as a function of development and agricultural stress in the watershed.

<p>Relative abundance of long-lived taxa (uni-, semi- and merovoltine) as a function of development and agricultural stress in the watershed.</p

Relative importance of the two watershed stressors and latitude in explaining variation in the functional attributes of macroinvertebrate communities, as proportional <i>lmg</i> contribution.

<p>Note the overriding importance of development over agricultural stress and the lack of significant geographic confounding. Asterisks indicate predictors that were significant in the multiple regression (p<0.05).</p