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The state of the California Current, 2001-2002: Will the California Current System keep its cool, or is El Niño looming?
This report summarizes physical and biological conditions in the California Current System (CCS), from Oregon to Baja California, in 2001 and 2002. The principal sources of the observations described here are the CalCOFI (California Cooperative Oceanic Fisheries Investigations), IMECOCAL (Investigaciones Mexicanas de la Corriente de California), and U.S. GLOBECLTOP (Global Ecosystems Long-term Observation Program) programs. Large-scale atmospheric and oceanic conditions in the Pacific point to a fourth consecutive La Niña-like year. This has contributed to generally stronger than normal upwelling and uncharacteristically cool waters in much of the CCS, a pattern that has persisted since late 1998. Biological productivity has been generally higher as well, particularly off Oregon. Within the observed interannual fluctuations of recent years, these conditions suggest a generally elevated production off California and Oregon, but cool conditions have led to lower than normal zooplankton biomass off Baja California. Although the tropical Pacific has exhibited some indications of a developing El Niño, it is not likely to impact the CCS during the productive upwelling season of 2002. These observations are continuing evidence that a regime shift may have occurred in 1998, resulting in substantial change in ecosystem structure in the CCS. Continued monitoring and analysis of the state of the CCS in this context is needed. We outline a plan for an integrated monitoring program for the entire region, through the creation of ACCEO (Alliance for California Current Ecosystem Observation)
Agglomeration and sedimentation of titanium dioxide nanoparticles (n-tio2) in synthetic and real waters
The recent detection of titanium dioxide nanoparticles (n-TiO2) in wastewaters raised concerns about its fate in the aquatic environment, which is related to its mobility through water bodies. Laboratory experiments of n-TiO2 (particle size distribution: 10–65 nm) dispersed into both synthetic and real
aqueous solutions under environmentally realistic
concentrations (0.01, 0.1, 1 and 10 mg/l) were
conducted over a time of 50 h to mimic duration of
ecotoxicological tests. Agglomeration and sedimentation
behaviour were measured under controlled conditions of salinity (0–35 %), ionic composition and strength, pH and dissolved organic carbon (DOC). Physico-chemical parameters and particle agglomeration
in the dispersions were investigated by transmission
electron microscopy, Brunauer, Emmett and
Teller method and dynamic light scattering. A fluorescence
spectrophotometer operating in the nephelometric mode was employed to obtain the sedimentation rates of n-TiO2. The overall results showed that agglomeration and sedimentation of n-TiO2 were affected mainly by
the initial concentration. Sedimentation data fitted
satisfactorily (R2 in the range of 0.74–0.98; average
R2: 0.90) with a first-order kinetic equation.The settling
rate constant, k, increased by approx. one order of magnitude by moving from the lowest to the highest concentration, resulting very similar especially for all
dispersions at 1(k = 8 9 10-6 s-1) and 10mg/l (k = 2 9 10-5 s-1) n-TiO2, regardless the ionic strength and composition of dispersions. The implication of these results on toxicological testing is discussed