Simulating pesticide leaching and runoff in rice paddies with the RICEWQ-VADOFT model

There is a current need to simulate leaching and runoff of pesticide from rice (Oryza sativa L.) paddies for assessing environmental impacts on a valuable agricultural system. The objective of this study was to develop a model for determining predicted environmental concentration (PEC) in soil, runoff, and ground water through the linkage of two models, rice water quality model (RICEWQ) and vadose zone transport model (VADOFT), to simulate pesticide fate and transport within a rice paddy and underlying soil profile. Model performance was evaluated with a field data set obtained from a 2-yr field experiment in 1997 and 1998 in northern Italy. The predictions of amount of pesticide running off from the paddy field and accumulating in the paddy sediment were in agreement with measured values. Leaching into the vadose zone accounted for approximately 19% of the applied dose, but only a small amount of chemical (<0.1%) was predicted to reach ground water at a 5-m depth due to sorption and transformation in the soil. The permeability of the soil and the water management practices in the paddy field were shown to have a strong influence on pesticide fate. These factors need to be well characterized in the field if model predictions are to be successful. The combined model developed in this work is an effective tool for exposure assessments for soil, surface water, and ground water, in the particular conditions of rice cultivation.     

Perceived safety from crime in the urban environment

Two studies were conducted to test various aspects of Appleton's Prospect-Refuge Theory. Hypotheses derived from the theory predicted that observers would rate how safe from crime they would feel in specific urban environments on the basis of whether the environments offered visibility (light), prospect (open spaces) and unambiguous refuge (a place where a criminal would not see the intended victim, or where other, non-threatening people were likely to to be present). It was further hypothesized that women in general would feel less safe from crime than men. In Study 1, University students generated lists of environmental features relevant to safety. Light was the most frequently mentioned factor, followed by open space and unambiguous refuge. In Study 2, slides were presented in which these three characteristics were independently varied. The results supported all of the hypotheses.     

Multi-year observations on the gametogenic ecology of the Antarctic seastar <Emphasis Type="Italic">Odontaster validus</Emphasis>

This study reports the first multi-year observations on the reproductive patterns for an Antarctic predator/scavenger, Odontaster validus (Koehler 1912). Seastars were collected monthly from a shallow site (15–20 m depth) near the British Antarctic Survey (BAS) Rothera Research Station (Adelaide Island, 67°34′S 68°08′W) from July 1997 to January 2001. Reproductive condition, oocyte size frequencies and spermatogenesis were examined in at least ten seastars each month using histological and image analysis techniques. Gonad indices (GI) and pyloric caeca indices (PI) were also examined in the same samples. Female and male GIs varied seasonally, in parallel with a reduction in the proportion of large oocytes and mature sperm in the gonad in August to mid-October following winter spawning. Despite there being remarkable consistency in the timing of spawning from year to year, differences in the reproductive condition of individuals were apparent. Patterns in the digestive tissues also varied with season, peaking in December and reaching a minimum in February in two of the three study years. This weaker annual pattern may partly reflect the varied diet of this predator/scavenger species, which is not directly dependant on the timing and magnitude of the annual phytoplankton bloom. Pooled oocyte size distributions and residual analysis suggested that oogenesis progressed over 18–24 months, with the largest of the two size classes (maximum diameter = 183 μm) being spawned annually. This pattern of oocyte growth and spawning was previously reported in the early 1960s for an O. validus population from McMurdo Sound, which lies south of Rothera by 10° latitude. The extremely catholic diet of this predator/scavenger suggests the reproductive patterns of the seastar will be less susceptible to changes in food supply compared to polar suspension feeders or deposit feeders. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

High mortality in a copepod population caused by a parasitic dinoflagellate

Infection of copepods by parasitic dinoflagellates has been known for many years, but the ecological consequences of this parasitism have been largely neglected. We estimated mortality rates in the copepodParacalanus indicus Wolfenden due to parasitism by the dinoflagellateAtelodinium sp. by applying laboratory mortality rates to a field population of infected copepods in Port Phillip Bay, Australia, sampled in 1982–1985. Adult female copepods were most often infected, with an incidence of 0 to 28.5% (median 6.2%). Stage V female copepodites were less often infected, and males were never infected. The median mortality rate in females was about 7% d^–1, or about one-third of total mortality, and the maximum was 41% d^–1. The frequent occurrence of dinoflagellate parasitoids in some species of copepod implies an important, species-specific mechanism for the regulation of populations.     

MtDNA population structure and gene flow in lingcod (<Emphasis Type="Italic">Ophiodon elongatus</Emphasis>): limited connectivity despite long-lived pelagic larvae

Lingcod, Ophiodon elongatus Girard, have a 3-month pelagic larval stage and are an important recreational and commercial species on the west coast of North America. Cytochrome-c oxidase I sequences from tissue samples were used to characterize population structure and infer patterns of gene flow from California to Alaska. No significant genetic structure was found when estimates of Wright’s F _ST (i.e., Φ_ST) were generated among all populations sampled. Nesting populations within regions, however, indicated that the inner coast of Washington State is distinct, a result corroborating previous allozyme work. Coalescent-based estimates of gene flow indicate that although migration can be high from an evolutionary perspective, nearly half of all comparisons among populations showed no gene flow in at least one direction. From an ecological perspective, moderate migration rates (Nm < 10) among most populations provide surprisingly limited connectivity at large (∼ 1,000 km) and small (∼100 km) spatial scales. Coalescent-based estimates also show that gene flow between the inner and the outer coasts is asymmetric, a result consistent with prevailing surface currents. Because the expected inter-locus variances for coalescent-based estimates of gene flow are likely large, future work will benefit from analyses of nuclear DNA markers. However, limited demographic connectivity on large spatial scales may help explain why stock recovery has been uneven, with greater recovery in the northern (87% rebuilt) than in the southern (24% rebuilt) fishery region, supporting a regional management strategy. These results suggest that despite a 3-month pelagic larval stage, some areas may be effectively closed with respect to both population dynamics and fishery management issues.     

Novel degradation products of the herbicide oxasulfuron identified by capillary electrophoresis – mass spectrometry

Two new intermediates rising from the photolytic reaction of the sulfonylurea herbicide oxasulfuron have been identified in aqueous environment. The higher concentrations of the two derivatives oxetan-3-yl 2-(formilsulfamoyl) benzoate and N-(4,6-dimethyl-pyrimidin-2-yl) formamide were reached within 8 h of UV-irradiation. Here we demonstrate that an optimal separation and analysis of such compounds can be achieved by using a novel analytical method based on “non-aqueous” capillary electrophoresis (CE) system joined to an electrospray ionisation-mass spectrometry equipment. Using such a separation method and a particular electrophoretic solution a high reproducibility of migration times and peak areas can be obtained.     

Elasticity analyses of size-based red and white abalone matrix models: management and conservation.

Prospective elasticity analyses have been used to aid in the management of fished species and the conservation of endangered species. Elasticities were examined for deterministic size-based matrix models of red abalone, Haliotis rufescens, and white abalone, H. sorenseni, to evaluate which size classes influenced population growth (lambda) the most. In the red abalone matrix, growth transitions were determined from a tag recapture study and grouped into nine size classes. In the white abalone matrix, abalone growth was determined from a laboratory study and grouped into five size classes. Survivorship was estimated from tag recapture data for red abalone using a Jolly-Seber model with size as a covariate and used for both red and white abalone. Reproduction estimates for both models used averages of the number of mature eggs produced by female red and white abalone in each size class from four-year reproduction studies. Population growth rate (lambda) was set to 1.0, and the first-year survival (larval survival through to the first size class) was estimated by iteration. Survival elasticities were higher than fecundity elasticities in both the red and white matrix models. The sizes classes with the greatest survival elasticities, and therefore the most influence on population growth in the model, were the sublegal red abalone (150-178 mm) and the largest white abalone size class (140-175 mm). For red abalone, the existing minimum legal size (178 mm) protects the size class the model suggests is critical to population growth. Implementation of education programs for novice divers coupled with renewed enforcement may serve to minimize incidental mortality of the critical size class. For white abalone, conservation efforts directed at restoring adults may have more of an impact on population growth than efforts focusing on juveniles. Our work is an example of how prospective elasticity analyses of size-structured matrix models can be used to quantitatively evaluate research priorities, fishery management strategies, and conservation options.