The speciation of Fe(II) and Fe(III) in natural waters

The interactions of Fe(II) and Fe(III) with the inorganic anions of natural waters have been examined using the specific interaction and ion pairing models. The specific interaction model as formulated by Pitzer is used to examine the interactions of the major components (Na⁺, Mg²⁺, Ca²⁺, K⁺, Sr²⁺, Cl⁻, SO₄⁻, HCO₃⁻, Br⁻, CO₃²⁻, B(OH)₄⁻, B(OH)₃ and CO₂) of seawater and the ion pairing model is used to account for the strong interaction of Fe(II) and Fe(III) with major and minor ligands (Cl⁻, SO₄²⁻, OH⁻, HCO₃⁻, CO₃²⁻ and HS⁻) in the waters. The model can be used to estimate the activity and speciation of iron in natural waters as a function of composition (major sea salts) and ionic strength (0 to 3 M). The measured stability constants (K_FeX^*) of Fe(II) and Fe(III) have been used to estimate the thermodynamic constants (K_FeX) and the activity coefficient of iron complexes (γ_FeX) with a number of inorganic ligands in NaClO₄ medium at various ionic strengths: In(K_FeX/γ_Feγ_X) = InK_FeX − In(γ_FeX) The activity coefficients for free ions (γ_Fe, γ_x) needed for this extrapolation have been estimated from the Pitzer equations. The activity coefficients of the ion pairs have been used to determine Pitzer parameters (B_FeX, B_FeX⁰, C_FeX^φ) for the iron complexes. These results make it possible to estimate the stability constants for the formation of Fe(II) and Fe(III) complexes over a wide range of ionic strengths and in different media. The model has been used to determine the solubility of Fe(III) in seawater as a function of pH. The results are in good agreement with the measurements of Byrne and Kester and Kuma et al. When the formation of Fe organic complexes is considered, the solubility of Fe(III) in seawater is increased by about 25%.     

Classification of juvenile flatfishes to estuarine and coastal habitats based on the elemental composition of otoliths

The elemental composition of otoliths from juvenile English sole Pleuronectes vetulus and speckled sanddab Citharichthys stigmaeus living in estuaries and sandy coastal habitats were compared to determine if a chemical habitat tag existed that could be used to differentiate fish living in the alternative juvenile habitats. Juveniles of both species were collected from seven estuaries and 11 coastal sites along 500 km of the central California coast. Collections occurred in three years: 1998, 1999 and 2000. The chemical composition of the otoliths was analyzed using solution-based inductively coupled plasma mass spectrometry. The multi-elemental composition (Sr, Li, Ba, Mn) of otoliths from estuarine and coastal fish differed significantly for all models (global, region and years models) examined in this study. For each species, discriminant function analysis (DFA) for the global model, which pooled juveniles collected from three regions over multiple years, classified fish into estuarine and coastal groups with close to 80% accuracy. The two main elements in the discriminant models, Sr and Li, differed consistently between habitats; Sr was higher and Li was lower in estuarine fish. Classification success was modestly improved by generating separate discriminant functions for each region (regions model) because of some regional differences in Sr and Li concentrations. Classification success also was improved in some cases by generating separate discriminant functions for each year (years model) because Ba and Mn differed between habitats in only some years. Despite this variability in the concentration of elements in some regions and years, a chemical habitat tag was present in each species that could be used to discriminate coastal and estuarine juveniles over a large geographic area and over three years with very different oceanographic conditions (e.g., El Niño, La Niña). In addition, I found that English sole and speckled sanddab had striking similarities in their chemical habitat tags and that, in some cases, one species could be used as a proxy to classify juveniles of the other species without compromising the accuracy of the habitat tag. The ability to use a proxy classification model would significantly reduce the number of juvenile fish that would need to be collected and analyzed in order to classify members of an ecologically similar species. The chemical habitat tags found in this study appears to be promising tools for identifying fish that have lived in alternative juvenile habitats and, ultimately, the proportional contribution of estuarine and coastal habitats to the central California populations of English sole and speckled sanddab.     

Clay-mineral suites,sources, and inferred dispersal routes: Southern California continental shelf

Clay mineralogy is useful in determining the distribution, sources, and dispersal routes of fine-grained sediments. In addition, clay minerals, especially smectite, may control the degree to which contaminants are adsorbed by the sediment. We analyzed 250 shelf sediment samples, 24 river-suspended-sediment samples, and 12 river-bed samples for clay-mineral contents in the Southern California Borderland from Point Conception to the Mexico border. In addition, six samples were analyzed from the Palos Verdes Headland in order to characterize the clay minerals contributed to the offshore from that point source. The <2 microm-size fraction was isolated, Mg-saturated, and glycolated before analysis by X-ray diffraction. Semi-quantitative percentages of smectite, illite, and kaolinite plus chlorite were calculated using peak areas and standard weighting factors. Most fine-grained sediment is supplied to the shelf by rivers during major winter storms, especially during El Ni?o years. The largest sediment fluxes to the region are from the Santa Ynez and Santa Clara Rivers, which drain the Transverse Ranges. The mean clay-mineral suite for the entire shelf sediment data set (26% smectite, 50% illite, 24% kaolinite+chlorite) is closely comparable to that for the mean of all the rivers (31% smectite, 49% illite, 20% kaolinite+chlorite), indicating that the main source of shelf fine-grained sediments is the adjacent rivers. However, regional variations do exist and the shelf is divided into four provinces with characteristic clay-mineral suites. The means of the clay-mineral suites of the two southernmost provinces are within analytical error of the mineral suites of adjacent rivers. The next province to the north includes Santa Monica Bay and has a suite of clay minerals derived from mixing of fine-grained sediments from several sources, both from the north and south. The northernmost province clay-mineral suite matches moderately well that of the adjacent rivers, but does indicate some mixing from sources in adjacent provinces.     

Temperature effects on asexual reproduction of the scyphozoan Aurelia aurita s.l.: differences between exotic (Baltic and Red seas) and native (Mediterranean Sea) populations

Massive occurrences of jellyfish can cause direct impacts on the economy, especially on tourism and commercial fisheries. Translocation of jellyfish species by humans has caused damaging blooms in new habitats. Aurelia aurita s.l. has been introduced in many locations around the world. To test the potential success of Au. aurita s.l. in various habitats, scyphistomae from different climatic locations (Mediterranean, Red and Baltic Seas) were cultured individually for 201 days at three temperatures (14, 21 and 28 °C) with the same salinity, food and light. We tested the null hypotheses that there were no differences in survival or asexual reproduction (budding and strobilation) amongst populations [native (Mediterranean) and exotic (Red and Baltic)]. Survival of the three scyphistoma populations did not differ significantly across temperatures; however, the Red Sea group had lower survival at all temperatures than did the other populations. Most individuals strobilated at 14 °C. Red Sea scyphistomae strobilated more quickly than Baltic and Mediterranean Sea scyphistomae and produced the fewest ephyrae, whereas Baltic Sea scyphistomae produced the most. Our results indicate that Au. aurita from the Baltic or Red Seas introduced into the Northwest Mediterranean Sea would potentially persist and successfully asexually reproduce there. A new invader could even have greater asexual production than the local Au. aurita s.l. Establishment of the invaders could increase genetic variation of subsequent generations and increase their adaptability to environmental changes. Our results suggest that introduction of exotic Au. aurita s.l. populations could increase jellyfish blooms in the Mediterranean Sea.     

Characteristics of Landfalling Tropical Cyclones in North Carolina

Trends in the Atlantic tropical cyclones and the cyclones that had tracks through North Carolina were analyzed for more than 100 years. From about 1970, there appears to be an increase in the mean number of storms developing. The number of storms affecting North Carolina each decade has been increasing since the 1960s. In the 1980s, 1990s, and into the 2000s, there was an increase in the number of landfalling storms in North Carolina. Although August and September are the most active months of the Atlantic hurricane season, the hurricane season for North Carolina peaks in September. Wind distribution and frictional convergence associated with landfalling hurricanes in North Carolina are discussed. Convection and precipitation patterns of landfalling hurricanes are presented. Two examples of the effect of spatial surface moisture distribution on intensification of tropical cyclones over land after landfall are discussed.     

Potential implications of global warming and barrier island degradation on future hurricane inundation,property damages,and population impacted

Hurricane flooding is a leading natural threat to coastal communities. Recent evidence of sea level rise coupled with potential future global warming indicate that sea level rise will accelerate and hurricanes may intensify over the coming decades. In regions fronted by barrier islands, the protective capacity of these islands may diminish as they are degraded by rising sea level. Here we present a hydrodynamic and geospatial analysis of the relative role of barrier island degradation on potential future hurricane flooding. For the City of Corpus Christi, Texas, USA, hurricane flooding is projected to rise between 20% and 70% by the 2030s, resulting in an increase in property damages and impacted population. These findings indicate that adaptive management strategies should be developed and adopted for mitigating loss of natural barrier islands when these islands act as protective features for populated bayside communities. Finally, this study illustrates a method for applying models to forecast future storm protection benefits of barrier island restoration projects.