Uptake and release of phosphorus by phytoplankton in the Chesapeake Bay estuary,USA

The phytoplankton uptake and release rates for inorganic phosphate, dissolved organic phosphate and polyphosphate were estimated during 5 cruises on the Chesapeake Bay over a 9-month period. Phosphorus in all pools turned over in several minutes to 100 h, and each soluble pool appeared to contain fractions which were metabolically useful to the phytoplankton. Maximal uptake rates (V _m ) for orthophosphate ranged from 0.02 to 2.95 μg-at P (1.h)^-1 with half saturation constants (K _s ) between 0.09 and 1.72 μg-at P l^-1. At low soluble reactive phosphorus concentrations, the uptake rate of trace ³²P orthophosphate was initially rapid, but declined after 15 to 60 min incubation. The data suggest that the initial uptake phase was dominated by exchange of ³²PO₄ ^≡ for ³¹PO₄ ^≡ in the membrane transport systems whereas the subsequent phase represented the net incorporation of orthophosphate into phytoplankton cells.     

Age-specific social dominance affects habitat use by breeding American redstarts (Setophaga ruticilla): a removal experiment

Summary By removing older males from their breeding territories, we tested the hypothesis that age-related dominance behavior influenced the pattern of habitat selection by breeding American redstarts Setophaga ruticilla (Aves: Parulinae). Fifteen older male redstarts removed in five experimental replicates during three breeding seasons were replaced by ten yearling and five older males; no redstart males of either age colonized the control sites during the same time periods, although two yearlings disappeared. Significantly more yearling males (67%, n=9) colonized the vacated areas than were present in the redstart population at large (26.8%, n=209). We reject the alternative hypothesis that yearling male redstarts occupy different habitats from older males because of age-related (innate) habitat preferences. Redstarts that colonized the territories made vacant by our removals (i.e., floaters) were a behaviorally heterogeneous group of animals. The presence of both yearling and older male floaters indicates that suitable habitat is limiting for this species and that intraspecific competitive interactions are important in habitat distribution, and potentially in population regulation.     

Contaminant Concentrations in the Atmosphere of Los Angeles County

Sampling for nitrogen and sulfur dioxides was initiated at several National Air Sampling Network stations in 1959 using a sampler developed for that purpose. In 1961 the Gas Sampling Network was expanded to its maximum of 49 stations. Sampling equipment and collecting solutions are supplied and chemical analyses performed by the network laboratories. Sampling and analysis procedures are described briefly. Average and maximum 24-hour concentrations of nitrogen dioxide and sulfur dioxide observed at 48 stations during 1961-1963 are presented.     

Schedule of Technical Sessions

Peroxyacyl nitrates are a family of compounds which result from photochemical reactions between contaminants released to the atmosphere by combustion of organic fuels. Peroxyacetyl nitrate (PAN) is the most abundant member of this family and is responsible for serious plant injury in some polluted areas. Plant injury has been recognized in at least 19 states and several foreign countries but economic loss has caused greatest concern in California. Characteristically, injury from PAN appears as glazing or bronzing of the lower leaf surface but the symptom syndrome may also include tissue collapse, chlorosis, and leaf drop. PAN inhibits activity of several enzyme systems by attacking the sulfhydryl group when enzyme extracts are fumigated in vitro, PAN may produce visible symptoms when sensitive plants are exposed for 4 hours to about 14 ppb. Other chemical members of the family are more toxic than PAN. Concentrations of 20 to 30 ppb PAN occur frequently at Riverside, Calif, and a maximum peak of 58 ppb was measured for one 2-hour period. Peaks as high as 54 ppb were reported at Salt Lake City, and 210 ppb at Los Angeles, Calif.     

Quantifying species recovery and conservation success to develop an IUCN Green List of Species

Stopping declines in biodiversity is critically important, but it is only a first step toward achieving more ambitious conservation goals. The absence of an objective and practical definition of species recovery that is applicable across taxonomic groups leads to inconsistent targets in recovery plans and frustrates reporting and maximization of conservation impact. We devised a framework for comprehensively assessing species recovery and conservation success. We propose a definition of a fully recovered species that emphasizes viability, ecological functionality, and representation; and use counterfactual approaches to quantify degree of recovery. This allowed us to calculate a set of 4 conservation metrics that demonstrate impacts of conservation efforts to date (conservation legacy); identify dependence of a species on conservation actions (conservation dependence); quantify expected gains resulting from conservation action in the medium term (conservation gain); and specify requirements to achieve maximum plausible recovery over the long term (recovery potential). These metrics can incentivize the establishment and achievement of ambitious conservation targets. We illustrate their use by applying the framework to a vertebrate, an invertebrate, and a woody and an herbaceous plant. Our approach is a preliminary framework for an International Union for Conservation of Nature (IUCN) Green List of Species, which was mandated by a resolution of IUCN members in 2012. Although there are several challenges in applying our proposed framework to a wide range of species, we believe its further development, implementation, and integration with the IUCN Red List of Threatened Species will help catalyze a positive and ambitious vision for conservation that will drive sustained conservation action.     

Long-term individual identification and site fidelity of white sharks, <Emphasis Type="Italic">Carcharodon carcharias</Emphasis>, off California using dorsal fins

Mark-recapture techniques can be used to estimate white shark (Carcharodon carcharias) population abundance. These frameworks are based on assumptions that marks are conserved and animals are present at the sampling location over the entire duration of the study. Though these assumptions have been validated across short-time scales for white sharks, long-term studies of population trends are dependent on these assumptions being valid across longer periods. We use 22 years of photographic data from aggregation sites in central California to support the use of dorsal fin morphology as long-term individual identifiers. We identified five individuals over 16–22 years, which support the use of dorsal fins as long-time individual identifiers, illustrate strong yearly site fidelity to coastal aggregation sites across extended time periods (decades), and provide the first empirical validation of white shark longevity >22 years. These findings support the use of fin morphology in mark-recapture frameworks for white sharks.