Coasts, water levels, and climate change: A Great Lakes perspective

The North American Laurentian Great Lakes hold nearly 20 % of the earth’s unfrozen fresh surface water and have a length of coastline, and a coastal population, comparable to frequently-studied marine coasts. The surface water elevations of the Great Lakes, in particular, are an ideal metric for understanding impacts of climate change on large hydrologic systems, and for assessing adaption measures for absorbing those impacts. In light of the importance of the Great Lakes to the North American and global economies, the Great Lakes and the surrounding region also serve as an important benchmark for hydroclimate research, and offer an example of successful adaptive management under changing climate conditions. Here, we communicate some of the important lessons to be learned from the Great Lakes by examining how the coastline, water level, and water budget dynamics of the Great Lakes relate to other large coastal systems, along with implications for water resource management strategies and climate scenario-derived projections of future conditions. This improved understanding fills a critical gap in freshwater and marine global coastal research.     

Chemical studies of copper-organic complexes isolated from estuarine waters using C18 reverse-phase liquid chromatography

Dissolved organic matter (DOM) and dissolved copper-organic complexes were isolated from the estuarine waters of Narragansett Bay, RI, using reverse-phase liquid chromatography employing C₁₈ Sep-Pak cartridges (Waters Associates). The cartridges were found to have a constant retention efficiency for processing ? 1-l volumes of seawater. Fractionation of the isolated material, by sequential elution of the Sep-Pak with water: methanol mixtures of increasing organic solvent concentration, yielded a fraction of the organic matter with a specific copper activity six times greater than the overall activity for the isolated DOM. Analysis of this fraction by high performance liquid chromatography suggested that the organic components are of intermediate polarity and have appreciable aromatic character.An investigation of the protonation characteristics of the isolated complexes indicated that most of the copper is associated with a broad range of acidic sites on the DOM. Analysis by electron paramagnetic resonance spectroscopy confirmed the organic association of the isolated copper and also suggested the presence of several types of binding sites which probably involve oxygen donor ligands.Studies of the exchange of ⁶⁴Cu with these binding sites on the isolated DOM indicated that 70% of the sites undergo rapid exchange with copper in seawater while 20% of these sites did not exchange in a 24-h time period.     

Isolation of dissolved organic matter and copper-organic complexes from estuarine waters using reverse-phase liquid chromatography

Reverse-phase liquid chromatography was used for the isolation of dissolved organic matter and dissolved copper-organic complexes from the estuarine waters of Narragansett Bay, Rhode Island. The procedure isolates 10–30% of the organic matter and up to 50% of the total dissolved copper from various bay samples. Chromatograms obtained by high-performance liquid chromatography of the isolated organic matter showed qualitative differences between sampling stations progressing from the Providence River in the upper bay to the lower bay.     

Chemical comparison of dissolved organic matter isolated from different oceanic environments

Dissolved organic matter was isolated from coastal and open-ocean surface waters having a wide range of biological productivities, and from seawater of intermediate depths. Approximately 50% of the organic matter was recovered by the use of activated-charcoal chromatography. The organic matter isolated from different types of water masses exhibited varying spectroscopic characteristics, and stable carbon-isotope compositions. The ability of the isolated organic matter to interact with copper ions also varied, but over a relatively narrow range which was not exceeded by more than a factor of two by similarly isolated terrigenous organic matter.     

Ice in the Southern Coalsack

To better understand the conditions under which ice mantles form on grains in molecular clouds, three globules in the Southern Coalsack have been searched for the presence of H₂O ice. Given the total lack of star formation in the Coalsack, it is an ideal site for studying unprocessed icy molecular mantles. In our sample of eight field stars lying behind the Coalsack we detect strong H₂O ice absorption in the lines of sight to two stars and possible weak absorption in four others. We estimate H₂O ice column densities or upper limits for these lines of sight. Compared to dark clouds such as Taurus, the Coalsack H₂O ice column densities are lower than expected given the quiescent nature of the Coalsack region. It is possible that the chemical evolution of the Coalsack may simply be at too early a stage for significant ice mantles to appear on the grains, except perhaps in the densest parts of some of the globules. Alternatively, the presence or absence of ice absorption may be related to the distribution of dust along each line of sight, specifically, the relative contributions of dense globules and a more extended diffuse component. For example, our observations are consistent with an ice threshold extinction similar to that observed in the Taurus dark cloud if extinction amounting to   A _V∼5  towards Globules 2 and 3 arises in the extended component. Globule 1 appears to have no extended component.