Spectral Irradiance and Phytoplankton Community Composition in a Blackwater-Dominated Estuary,Winyah Bay,South Carolina,USA     

Evelyn Lawrenz  James L. Pinckney  Melissa L. Ranhofer  Hugh L. MacIntyre  Tammi L. Richardson 《Estuaries and Coasts》2010,33(5):1186-1201

We investigated spatial and temporal relationships between spectral irradiance and phytoplankton community composition in the blackwater-influenced estuary Winyah Bay, South Carolina. Upstream, high concentrations of chromophoric dissolved organic matter (CDOM) absorbed blue wavelengths, resulting in a predominantly red light field. Green light prevailed downstream near the lower-CDOM coastal ocean, and phytoplankton community composition was distinct from upstream and mid-estuarine communities. Diatoms were abundant throughout the estuary in January, August, and October, cryptophytes dominated in July, and chlorophytes were abundant in December 2006. Only diatoms and chlorophytes showed significant covariation with the spectral attenuation coefficient (k(λ)): Chlorophytes showed positive relationships with k(442) (blue light) while diatoms were negatively correlated with k(442) and k(490) (violet to blue). Phytoplankton community composition in Winyah Bay appears to be driven by strong horizontal flow rather than gradients in spectral irradiance, but results indicate that water color is likely to play a greater role in blackwater-influenced estuaries with longer residence times.  相似文献   

Distribution of Diatoms and Development of Diatom-Based Models for Inferring Salinity and Nutrient Concentrations in Florida Bay and Adjacent Coastal Wetlands of South Florida (USA)     

Anna Wachnicka  Evelyn Gaiser  Laurel Collins  Thomas Frankovich  Joseph Boyer 《Estuaries and Coasts》2010,33(5):1080-1098

The composition and distribution of diatom algae inhabiting estuaries and coasts of the subtropical Americas are poorly documented, especially relative to the central role diatoms play in coastal food webs and to their potential utility as sentinels of environmental change in these threatened ecosystems. Here, we document the distribution of diatoms among the diverse habitat types and long environmental gradients represented by the shallow topographic relief of the South Florida, USA, coastline. A total of 592 species were encountered from 38 freshwater, mangrove, and marine locations in the Everglades wetland and Florida Bay during two seasonal collections, with the highest diversity occurring at sites of high salinity and low water column organic carbon concentration (WTOC). Freshwater, mangrove, and estuarine assemblages were compositionally distinct, but seasonal differences were only detected in mangrove and estuarine sites where solute concentration differed greatly between wet and dry seasons. Epiphytic, planktonic, and sediment assemblages were compositionally similar, implying a high degree of mixing along the shallow, tidal, and storm-prone coast. The relationships between diatom taxa and salinity, water total phosphorus (WTP), water total nitrogen (WTN), and WTOC concentrations were determined and incorporated into weighted averaging partial least squares regression models. Salinity was the most influential variable, resulting in a highly predictive model (r _apparent² = 0.97, r _jackknife² = 0.95) that can be used in the future to infer changes in coastal freshwater delivery or sea-level rise in South Florida and compositionally similar environments. Models predicting WTN (r _apparent² = 0.75, r _jackknife² = 0.46), WTP (r _apparent² = 0.75, r _jackknife² = 0.49), and WTOC (r _apparent² = 0.79, r _jackknife² = 0.57) were also strong, suggesting that diatoms can provide reliable inferences of changes in solute delivery to the coastal ecosystem.  相似文献   

Coastal management challenges from a community perspective: The problem of ‘stealth privatization’ in a Canadian fishery     

Melanie G. Wiber  Murray A. Rudd  Evelyn Pinkerton  Anthony T. Charles  Arthur Bull 《Marine Policy》2010,34(3):598-605

Intertidal clam fisheries seem ideal candidates for the devolution of management authority from government to local stakeholders. In St. Mary's Bay, Nova Scotia, a private firm recently applied for a 10-year renewal of a large (1,627 ha) lease for quahog clam aquaculture. This case study examines the challenges of implementing community-based natural resource management (CBNRM) in rural fisheries within a broad integrated coastal management (ICM) institutional environment that favours corporate stakeholders. The challenges facing clam harvesters in rural Digby Neck, Nova Scotia arise from poor communication and coordination within government and between government and communities, as well as higher-level policy conflicts. The most important challenge arises from ‘stealth privatization’ of clam beaches. A single firm was granted rights of first refusal to depurate all clams harvested from closed (polluted) beaches in the region, resulting in the de facto privatization of all (polluted and unpolluted) clam beaches. Experiences in other parts of Canada suggest there may be community-based governance approaches that avoid the pitfalls associated with corporate management of clam beaches. New thinking is required about how to moderate the ‘privatization paradigm’ so prevalent within senior levels of government in order to ensure environmental and social sustainability in rural fishing communities.  相似文献   

Geographic Naming in New Zealand: The Role of the New Zealand Geographic Board   总被引：1，自引：0，他引：1  

Evelyn Stokes 《New Zealand geographer》1994,50(2):51-54

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Nitrogen pools in Georgia coastal waters     

Evelyn B. Haines 《Estuaries and Coasts》1979,2(1):34-39

The amount of nitrogen present as ammonia, nitrate, nitrite, dissolved organic nitrogen, and particulate nitrogen was determined for nearshore Georgia shelf waters and for tidal water inundating a 0.5 hectare dikedSpartina alterniflora salt marsh in the adjacent estuary. Concentrations of ammonia, nitrate, and nitrite were comparatively low in offshore water (<2.2 μg-at N/1), and in high tide water in the marsh (<9.9 μg-at N/1). High concentrations of ammonia, up to 73.4 μg-at N/1, were measured in low tide water draining from marsh. The largest pools of nitrogen in offshore water and in high tide water in the marsh creek were dissolved organic nitrogen (DON) (2.5 to 20.4 μg-at N/1) and particulate nitrogen (PN) (0.1 to 30.0 μg-at N/1). Concentrations in marsh creek water at low tide were higher, ranging from 4.4 to 38.0 μg-at N/1 for DON and from 13.0 to 239.0 μg-at N/1 for PN. Comparisons of the average concentrations of dissolved and particulate forms of nitrogen in the marsh tidal creek during flood and during ebb tide suggested no net movement of the inorganic nitrogen nutrients, a net influx of PN to the marsh, and a net outflux of DON from the marsh.  相似文献   

Growth dynamics of cordgrass,Spartina alterniflora loisel., on control and sewage sludge fertilized plots in a Georgia salt marsh     

Evelyn B. Haines 《Estuaries and Coasts》1979,2(1):50-53

Seasonal plant growth dynamics were followed for a year in undisturbed plots of tall and short formSpartina alterniflora Loisel. and in plots of short formS. alterniflora which were enriched with sewage sludge at a rate of 100 g dry sludge m^?2wk^?1, corresponding to a nitrogen enrichment of 2 g N m^?2wk^?1. Monthly determinations of aboveground live and dead biomass, density of live stems, the ratio of number of young shoots to total number of shoots, and belowground mass of macro-organic matter to a depth of 30 cm were made for each area. Sludge fertilization increased the live biomass of the short formS. alterniflora by up to 150% of the control live biomass, but had little effect on the dead biomass, stem density, or proportion of young shoots. There was a trend of increased amount of belowground macro-organic matter in fertilized compared to control plots during the last 6 months of the study. In all areas, there was a marked decrease in the proportion of young shoots from winter to early summer, followed by a rapid increase in the percent of young shoots from late summer to fall. Sampling of plots 7 and 20 months after termination of sludge enrichment showed higher plant biomass and % N content in surface soils, but no difference in N content of live plant tissue, in fertilized compared to unfertilized marsh. After 20 months, about half of the sludge nitrogen remaining in the soils of the fertilized plots had disappeared.  相似文献   

Spatial variability of soil nutrients in disturbed riverine mangrove forests at different stages of regeneration in the San Juan River estuary,Venezuela     

Victor?H.?Rivera-MonroyEmail author  Robert?R.?Twilley  Ernesto?Medina  E.?Barry?Moser  Leonor?Botero  Ana?Marta?Francisco  Evelyn?Bullard 《Estuaries and Coasts》2004,27(1):44-57

Geostatistical analysis of selected soil properties were performed in two mangrove sites (B7 and B9) dominated by the mangrove speciesRhizophora mangle along the San Juan River, Venezuela, to evaluate the effect of forest disturbance on nutrient spatial distributions. Plots within area B7 were clear-cut in 1972–1973 and in area B9 in 1982–1983. Four plots within each area were systematically selected and represented natural (2) and regenerated (2) forests. Individual plots were 1.5 ha in B7 and 1.25 ha in B9 and sampled at a resolution of 25 m. Soil samples were obtained at the intersection of an aligned grid with 90 points in B7 and 78 points in B9. Measured soil properties included salinity, total nitrogen, total carbon, total phosphorus, osmolality, and pore water cation concentrations (potassium, calcium, magnesium, and sodium). Sites were sampled in May 1996 and 1997, although spatial analysis was performed only for the data obtained in May 1997. Geostatistical analysis showed that most of the variables tested were spatially auto-correlated within each area and that there were no differences between regenerated and natural plots. Structural variance as a proportion of sample variance ranged from 55–99% for most of the properties. The significant spatial dependence observed for most of the variables in natural and regenerated plots, despite management schedules, indicates that clear-cutting did not have an effect on modifying the distribution of nutrient concentrations. These results suggest that after 15 and 25 yr following forest disturbance nutrient distributions were reestablished either there was not a net effect on patterns of element loss or tidal input was stronger than plant modifications of soils.  相似文献   

Impact of elevated ammonium on reproduction in two Hawaiian scleractinian corals with different life history patterns     

Cox EF  Ward S 《Marine pollution bulletin》2002,44(11):1230-1235

Elevated nutrients have the potential to disrupt reproduction in scleractinian corals, with consequent impacts on population dynamics. Reproduction in broadcast spawning (Montipora capitata) and brooding (Pocillopora damicornis) species was assessed following exposure to elevated ammonium in a microcosm experiment. Planulation in P. damicornis ceased following 4 months of ammonium exposure and did not recover until 3 months after termination of nutrient enrichment. Larval settlement and survivorship were not affected by ammonium enrichment. Few significant changes were found for reproductive parameters of M. capitata. There was a significant but small decrease in egg size (430 microm in control eggs to 408 microm in eggs from ammonium enrichment treatments), but no differences in total fecundity or fertilization success. This may be related to the presence of zooxanthellae in the eggs of M. capitata, in contrast to changes in reproduction previously reported in Acropora species, whose eggs do not contain zooxanthellae.  相似文献   

Distribution of diatoms among intermittent ponds on the Atlantic Coastal Plain: development of a model to preduct drought periodicity from surface-sediment assemblages     

Evelyn E. Gaiser  Thomas E. Philippi  Barbara E. Taylor 《Journal of Paleolimnology》1998,20(1):71-90

Inferences of past climate from the fossil record in lakes rely on the accurate quantification of a relationship of fossilizing organisms to their environment. Whereas the relationship of diatoms to water chemistry parameters has been modeled in many systems, few studies adequately address the relationship of diatoms to physical properties, such as water depth or hydrology, that may be more directly tied to climate. We examined the composition of modern diatoms in surface sediments of 75 isolated ponds (mostly Carolina bays) of the Atlantic Coastal Plain to: (1) assess the influence of physical and chemical variables on the distribution of diatoms among ponds of the region, and (2) develop a model that predicts hydroperiod (a measure of pond permanence) from diatom assemblages. We constructed two hydroperiod calibration models: the first infers hydroperiod from the weighted-average optima and tolerances of taxa along the hydroperiod gradient, the second bases inferences on the hydroperiod estimates of compositionally similar samples. Both approaches incorporate a-priori and post-hoc tests of assumptions often inherent in the construction of transfer functions. Diatom assemblage composition had strong, approximately linear relationships to hydroperiod, water depth, and calcium concentration in non-metric multidimensional ordination space; effects of other variables, including pH, were non-linear or ambiguous. Overall, the assemblages reflected the dilute, acidic chemical characteristics of bays. The assemblages contained differing abundances of euterrestrial, benthic and planktonic taxa, depending on a pond's susceptibility to drying. A weighted-averaging regression model based on taxon-specific hydroperiod optima generated adequate, unbiased hydroperiod inferences from diatom species composition (r² = 0.81). This model may be used to infer past drought episodes from fossil diatom assemblages at appropriate sites on the Atlantic Coastal Plain.  相似文献   

Case 21 water level and strain changes preceding and following the August 4, 1985 Kettleman Hills, California, earthquake     

Evelyn Roeloffs  Eddie Quilty  C. H. Scholtz 《Pure and Applied Geophysics》1997,149(1):21-60

Two of the four wells monitored near Parkfield, California, during 1985 showed water level rises beginning three days before theM _w 6.1 Kettleman Hills earthquake. In one of these wells, the 3.0 cm rise was nearly unique in five years of water level data. However, in the other well, which showed a 3.8 cm rise, many other changes of comparable size have been observed. Both wells that did not display pre-earthquake rises tap partially confined aquifers that cannot sustain pressure changes due to tectonic strain having periods longer than several days. We evaluate the effect of partial aquifer confinement on the ability of these four wells to display water level changes in response to aquifer strain. Although the vertical hydraulic diffusivities cannot be determined uniquely, we can find a value of diffusivity for each site that is consistent with the site's tidal and barometric responses as well as with the rate of partial recovery of the coseismic water level drops. Furthermore, the diffusivity for one well is high enough to explain why the preseismic rise could not have been detected there. For the fourth well, the diffusivity is high enough to have reduced the size of the preseismic signal as much as 50%, although it should still have been detectable. Imperfect confinement cannot explain the persistent water level changes in the two partially confined aquifers, but it does show that they were not due to volume strain. The pre-earthquake water level rises may have been precursors to the Kettleman Hills earthquake. If so, they probably were not caused by accelerating slip over the part of the fault plane that ruptured in that earthquake because they are of opposite sign to the observed coseismic water level drops.  相似文献