Neural net modeling of estuarine indicators: Hindcasting phytoplankton biomass and net ecosystem production in the Neuse (North Carolina) and Trout (Florida) Rivers, USA

Phytoplankton biomass, as chlorophyll (Chl) a, and net ecosystem production (NEP), were modeled using artificial neural networks (ANNs). Chl a varied seasonally and along a saline gradient throughout the Neuse River (North Carolina). NEP was extremely dynamic in the Trout River (Florida), with phototrophic or heterotrophic conditions occurring over short-term intervals. Physical and chemical variables, arising from meteorological and hydrological conditions, created spatial and/or temporal gradients in both systems and served as interacting predictors for the trends/patterns of Chl a and NEP. ANNs outperformed comparable linear regression models and reliably modeled Chl a concentrations less than 20 μg L-1 and NEP values, denoting the apparent non-linear interactions among abiotic and indicator variables. ANNs underestimated Chl a concentrations greater than 20 μg L-1, likely due to the periodicity of data acquisition not being sufficient to generalize system variability, the designated 'lag' effect for variables not being adequate to portray estuarine flow dynamics, the exclusion of (one or more) variables that would have improved prediction, and/or an unrealistic expectation of network performance. Variables indicative of meteorological and hydrological forcing and/or proxy measurements of phytoplankton had the greatest relative impact on prediction of Chl a and NEP. Except for their predictive capability, ANNs might appear to be of limited value for ecological applications and problem solving; interpreting the absolute impact of and/or interacting relationships among network variables is intrinsically difficult. Statistical methods or 'rule extraction' algorithms that convey comprehensible network interpretation are needed prior to the routine use of ANNs in programs assessing and/or forecasting the response of biotic indicators to perturbation or for a means to discern estuarine function

Effects of trichlorobenzene on natural phytoplankton populations

Natural phytoplankton assemblages from an offshore station in Lake Michigan were exposed to individual isomers of trichlorobenzene (TCB) and incubated in situ for a 24 h period. One set of exposures was initiated with a lake assemblage collected at 0330 h from 30 m and the TCB isomers added at 0400 h. The second exposure experiment was initiated with an assemblage from 30 m collected at 1530 h and the TCB isomers added at 1600 h.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44445/1/10646_2004_Article_BF00368534.pd

Shopper Security and the City Centre Shopping Environment: The Cases of Swansea and Cardiff

The Context In recent years many British city centres have experienced competition from out-of-town facilities. This has resulted in the contraction or decline of their retail status. The effects of competition have been exacerbated by accessibility problems and a decline of the residential population of the inner city. However, work in retail geography, the geography of crime and environmental criminology suggest that the deficiencies in security in city centres is a significant, and sometimes major contributor to the emerging malaise, and a potentially important component of a further spiral decline in status. Concern has focused on actual and perceived physical threats to shoppers, and on car theft or vandalism. Likewise, ram raids against stores, and intermittent terrorist activities and security alerts have necessitated security measures which frequently detract from the convivial atmosphere of city centres, and in extreme cases can create a "fortress" effect. Issues for Research Due to a fear of attacks against the person and a concern about car theft, it is possible that a growing proportion of the regional population is now avoiding city centres. Those who still visit the centre may try to avoid certain parts of the central business district at differing times of the day or week. This temporal/spatial inequality of use needs to be redressed. A vibrant city centre needs to be viewed as both attractive and safe at any hour of the day or night, if the area is to remain a thriving focus of activity and an asset to the whole regional population. Many people naturally avoid areas that they consider dangerous, and in so doing make such areas even more hazardous due to fewer people using the area. In the retail environment this is recognised as having a detrimental effect on trade and so needs to be researched as part of the process of revitalising city centres. Even if parts of the city centre become "no go" areas only after dark, this reputation might be extended in the minds of shoppers to the day and, consequently undermine the status of the centre. There is also the issue of equality of access for different social sub-groups, primarily women and the elderly. Some are particularly inclined to avoid certain parts of the city centre, especially after dark. This issue will also be examined. Aims of the Research Project: 1. To investigate both the nature and frequency of visits to the city centre retail district by the shopping public. (Swansea and Cardiff) 2. To identify those people who are discouraged from visiting the city centre through concerns over personal safety and car theft, together with a recognition that some have easy access to alternative retail centres. (Swansea) 3. To establish whether or not perceptions of personal safety and a concern over car theft influence shoppers' spatial and temporal behaviour within the city centre, and whether this has any effect on the retail trade of different parts of the central retail district. (Swansea and Cardiff) 4. To determine the actual pattern of crime incidents across the city centres of Swansea and Cardiff through the detailed analysis of police data for a full year. 5. To examine the relationship between shopper perceptions of security problems and actual crime incidents. 6. To integrate the findings from the questionnaire surveys, environmental audits and police data analyses, in order to contribute to the development of optimal design and management policies for a "viable and vibrant" city centre in the future

The Growth Dynamics of \u3ci\u3eKarenia brevis\u3c/i\u3e Within Discrete Blooms on the West Florida Shelf

As part of the ECOHAB: Florida Program, we studied three large blooms of the harmful bloom forming dinoflagellate Karenia brevis. These blooms formed on the West Florida Shelf during Fall of 2000 off Panama City, and during Fall 2001 and Fall 2002 off the coastline between Tampa Bay and Charlotte Harbor. We suggest that these blooms represent two different stages of development, with the 2000 and 2001 blooms in an active growth or maintenance phase and the 2002 bloom in the early bloom initiation phase. Each bloom was highly productive with vertically integrated primary production values of 0.47-0.61, 0.39-1.33 and 0.65 g C m(-2) d(-1) for the 2000, 2001 and 2002 K brevis blooms, respectively. Carbon specific growth rates were low during each of these blooms with values remaining fairly uniform with depth corresponding to generation times of 3-5 days. Nitrogen assimilation by K. brevis was highest during 2001 with values ranging from 0.15 to 2.14 mu mol N L-1 d(-1) and lower generally for 2000 and 2002 (0.01-0.64 and 0.66-0.76 mu mol N L-1 d(-1) for 2000 and 2002, respectively). The highest K. brevis cell densities occurred during the 2001 bloom and ranged from 400 to 800 cells mL(-1). Cell densities were lower for each of the 2000 and 2002 blooms relative to those for 2001 with densities ranging from 100 to 500 cells mL-1. The 2000 and 2001 blooms were dominated by K brevis in terms of its contribution to the total chlorophyll a (chl a) pool with K brevis accounting generally for \u3e 70% of the observed chl a. For those populations that were dominated by K brevis (e.g. 2000 and 2001), phytoplankton C biomass (C-p,C-o) constituted \u3c 30% of the total particulate organic carbon (POC). However, in 2002 when diatoms and K brevis each contributed about the same to the total chl a, C-p,C-o was \u3e 72% of the POC. The fraction of the total chl a that could be attributed to K. brevis was most highly correlated with POC, chl a and salinity. Nitrogen assimilation rate and primary production were highly correlated with a greater correlation coefficient than all other comparisons. (c) 2007 Elsevier Ltd. All rights reserved