- About
- Affiliates
- Join
- Publications
- Estuaries and Coasts
- CERF's Up! Quarterly Bulletin
- Coastal & Estuarine Science News (CESN)
- CERF-Lit
- Advertising
- Programs & Events
- Inclusive Culture
- Communities
CESN Main PageCoastal & Estuarine Science News (CESN)Coastal & Estuarine Science News (CESN) is an electronic publication providing brief summaries of select articles from the journal Estuaries & Coasts that emphasize management applications of scientific findings. It is a free electronic newsletter delivered to subscribers on a bimonthly basis. February 2007ContentsIn Chesapeake, Benthic Community Shows that Where Development is Up, Estuarine Health is Down In Chesapeake, Benthic Community Shows that Where Development is Up, Estuarine Health is DownDecades of research and monitoring have established that coastal development is often accompanied by impacts such as hypoxia, algal blooms, and decreased biodiversity. One set of tools that has proven useful in quantifying the links between development and environmental health are easily-interpretable benthic indices based on macroinvertebrate community composition. Two such indices, B-IBIN and the W-value, were used in an extensive two-year study of 23 Chesapeake Bay sub-watersheds to assess the condition of nearshore tidal habitats. After calculating the benthic indices for all sites and accounting for variable environmental conditions, the indices were then correlated with land use categories to determine the impact of development on estuarine health. The highest benthic index scores (indicating the healthiest sites) were associated with forested watersheds, while the lowest were found in developed watersheds. Further, the authors identified shoreline and watershed land use thresholds above which degradation consistently occurred: areas in which more than 10-12% of the land is developed were likely to exhibit degraded ecological conditions. Telling the Phragmites Twins Apart: Native Prefers No Salt and Little NitrogenMost studies of the common reed, Phragmites australis, focus on its invasive nature and the ecological and management implications of its takeover of disturbed aquatic ecosystems. But there is a non-invasive native Phragmites haplotype (genetically distinct lineage) as well, which has largely been displaced by the invasive haplotype in many areas. A recent study of the two haplotypes along Virginia’s Rappahannock River revealed some interesting differences between the relatives, which may have important management implications. The native Phragmites was found only at sites where the salinity was 0, while the invasive plant exhibited a much wider range of salinity tolerance, from 0-11. The invasive haplotype was generally found in a monoculture in ecologically disturbed areas (near highway bridges, development, etc.) while the native Phragmites was found in small patches interspersed with a mix of other wetland plants. Finally, nitrogen concentrations in non-native haplotype leaves were significantly higher than the native plants, while carbon concentrations were lower, perhaps indicating that the invasives have a higher N requirement. Fish Index Proves Useful in Taking the Pulse of South African EstuariesIndices of environmental quality that integrate multiple measures of ecological condition serve many purposes: they elucidate the effects of multiple environmental stressors, and they can serve as effective communications tools to convert complex information about a system’s health into an easily understood metric for policy makers and the general public. One such condition index was developed and tested in a recent survey of South African estuaries. The Estuarine Fish Community Index (EFCI) integrates 14 metrics representing four aspects of fish communities and ecology: species diversity and composition, species abundance, nursery function, and trophic integrity. The South African survey examined 190 estuaries encompassing a broad spectrum of biogeographic regions and morphological estuary types. After calculating the EFCI value for each estuary using data from extensive field surveys, the index was used to classify the health of each system, ranging from “very poor” to “very good.” Results indicated that the more degraded estuaries tended to be smaller systems with restricted mouths. Bioenergetics Study Reveals Tough Choice for Invasive Crabs: Get Eaten or Use Excess EnergyThe European green crab, Carcinus maenas, gets around. Native to the northeast Atlantic, it has made itself at home around the world, establishing itself as one of the most successful marine invasive species. In Washington’s Willapa Bay, where the crab has been found since 1998, monitoring data indicate that the crabs favor intertidal areas during the summer, especially extensive Spartina meadows. Researchers set out to determine whether there is a particular energetic incentive for the crabs to seek out these habitats, using a bioenergetics framework. This approach is based on the simple premise that, energetically speaking, what goes in must go out. In other words, consumption of food (“energy in”) is equal to the sum of energetic expenditures: respiration, growth, egestion, and excretion. In order to determine if the Willapa Bay green crabs were making the “right” habitat choice from an energetics standpoint, a commonly-used bioenergetic model was parameterized using literature values derived from previous studies of C. maenas and related species. Ground-truthing of actual crab habitat use was carried out in conjunction with ongoing monitoring surveys. |