Annual Retention Rate Research Articles

Distribution and Retention Trends of Obstetricians and Gynecologists in Japan: A Longitudinal Study.

Introduction: This longitudinal study aimed to investigate the distribution and retention of obstetricians and gynecologists in Japan. Methods: I used descriptive statistics and multivariate logistic regression to analyze data from National Census surveys administered during 1996-2016. Results: Between 1996 and 2016, the number of obstetricians and gynecologists increased by 6% and urban physicians by 15%, whereas the number of rural physicians decreased by 25%. The annual retention rate, which was calculated using the square root of the biannual rates [the number of physicians still working as obstetricians and gynecologists at the time of the subsequent survey (e.g., in 1998) divided by the number of obstetricians and gynecologists in the original survey (e.g., in 1996)], was >90%. Obstetricians and gynecologists were less likely to continue to work as obstetricians and gynecologists after 30-44 years of experience (1996-2006 cohort: OR = 0.20, 95% CI = 0.17-0.25; 2006-2016 cohort: OR = 0.32, 95% CI = 0.25-0.41) and >45 years of experience (1996-2006 cohort: OR = 0.14, 95% CI = 0.11-0.17; 2006-2016 cohort: OR = 0.11, 95% CI = 0.08-0.15). The odds were lower for rural obstetricians and gynecologists (1996-2006 cohort: OR = 0.65, 95% CI = 0.51-0.82; 2006-2016 cohort: OR = 0.59, 95% CI = 0.43-0.80). As the number of female physicians increased, the number of practicing obstetricians and gynecologists also increased. In 2004, the mandatory postgraduate clinical training that was newly implemented caused a drop in the number of young doctors; however, this reversed in 2006. Rural to urban migration was steady, and the working hours were consistently long. To stabilize high retention rates, the working environments need to be improved. Conclusions: The present study clearly indicated the trend of the distribution of obstetricians and gynecologists in Japan. The result may be especially important for the health policy making in Japan.

Facility-Level Factors Associated With CNA Turnover and Retention: Lessons for the Long-Term Services Industry.

Certified nursing assistant (CNA) turnover and retention are critical aspects of facilities' ability to provide cost-effective, high-quality person-centered care. Previous studies and industry practice often treat turnover and retention as similar concepts, assuming that low turnover and high retention are synonymous. The study addressed the question of whether turnover and retention rates differ and if so, what those differences mean for nursing home practice, policy, and research. This study examines facility-level factors associated with CNA retention and turnover rates using 2015 data from the Ohio Biennial Survey of Long-Term Care Facilities, Ohio Medicaid Cost Reports, Certification and Survey Provider Enhanced Report, and the Area Health Resource File. Using bivariate tests and regression analysis, we compare rates and the factors associated with retention and turnover. The mean facility annual retention rate was 64% and the mean annual turnover rate was 55%. As expected, there was a statistically significant and negative correlation between the rates (r = -0.26). However, some facilities had both high retention and high turnover and some had low rates for both measures. Not all the variables that are associated with turnover are also associated with retention. CNA retention is not simply the absence of CNA turnover. Given the differences, nursing homes may need to use strategies and policies designed to target a particular stability measure.

Tempo-spatial and Retention Analysis of Total Phosphorus in the Three Gorges Reservoir

Phosphorus, as a limiting and vital macronutrient in water, circulates mainly with sediment through rivers. The construction and operation of large reservoirs can have a profound impact on the characteristics of phosphorus transportation and transformation. Based on measured hydrological and water quality data during 2008-2016 in the Three Gorges Reservoir (TGR), a statistical model of total phosphorus (TP) flux and sediment load in different periods was established. The formula of TP flux was established by analyzing the interpolation of unmeasured TP concentration, tempo-spatial characteristics, flux variation, and the retention effect of TP in the TGR. The results indicated that taking no account of the effects of TP inflows of tributaries, annual TP concentration in the TGR varied between 0.196 mg·L-1 and 0.290 mg·L-1 during 2008-2012, and inner-annual changes in TP concentration presented an "M" type with two obvious peaks. TP concentration decreased slowly from upstream to downstream of the TGR, and increased significantly from Cuntan to Qingxichang in some years. The average annual TP flux and retention rate of the TGR were 82300 t and 49.76% during 2008-2012, respectively. During 2013-2016, the average annual TP flux and retention rate decreased significantly, to about 47900 t and 12.03%, respectively.

Changes in the Characteristics of Rehabilitation Physicians over Two Decades: Analysis of National Physician Census Surveys in Japan.

ABSTRACTObjective:The aim of the study was to analyze the demographics of rehabilitation physicians and their retention trends, identify factors related to physician retention, and consider the policy implications. Methods:The individual data from 1996 to 2016 from a national census survey administered every two years by the national government of Japan were analyzed. The physician retention trends were then evaluated. Finally, a multivariable logistic regression analysis was performed to identify the factors related to the retention of rehabilitation physicians. Results:The total numbers of rehabilitation physicians in 1996 and 2016 were 902 (0.4% of all physicians) and 2484 (0.8% of all physicians), respectively, an increase of 175%. It should be noted that between 1996 and 2016 the number of physicians aged ≤39 years decreased, whereas the number of physicians aged ≥40 years greatly increased to 2118, accounting for 85.3% of all rehabilitation physicians in 2016. The overall annual retention rate of full-time rehabilitation physicians from 1996 to 2016 increased by 6.6%. The odds of continuing to practice as a rehabilitation physician were significantly higher for academic hospital physicians than for clinic physicians. Conclusion:The dramatic increase in the number of rehabilitation physicians in Japan has been prompted by policy measures and rapidly increasing demands for rehabilitation due to the aging of society. Ensuring the entry of younger physicians into this career path through efforts such as establishing rehabilitation medicine classes in every school of medicine is necessary to promote the development of specialist rehabilitation physicians in Japan.

DEVELOPMENT AND EVALUATION OF THE NURSES IMPROVING CARE FOR HEALTHSYSTEM ELDERS (NICHE) LONG-TERM CARE PROGRAM

Nurses Improving Care for Healthsystem Elders (NICHE) is a geriatric care model that positions nurses as leaders to address the unique care needs of older adults. From 2016 to 2019, we developed and piloted the NICHE-LTC program. NICHE-LTC program includes the three interrelated components of 1). the Geriatric Resource Nurse (GRN) and Geriatric Certified Nursing Assistant (GCNA) clinical leadership roles; 2) research-based clinical protocols and assessment tools; and 3). staff development, quality improvement (QI), and care coordination models to build clinician and organizational capacity in geriatrics. We report the results of a summative program evaluation of the NICHE-LTC program. We collected data on organizational and participant demographics, facility enrollment and retention, program completion rates, clinical quality improvement project plans, and participant satisfaction data from 369 individuals working in 79 facilities participating in NICHE-LTC program from January 2016 to February 2019. The majority of participants (80%) reported a positive learning outcome after completing NICHE-LTC program. Additionally, 80% reported they agreed or strongly agreed that their knowledge and ability to implement quality improvement initiatives in their facilities improved. The NICHE-LTC supported facilities ability to move from process-oriented QI priorities to patient-based outcome QI priorities such as falls, pain management, and managing behaviors of dementia. Over the three-year pilot period, NICHE-LTC program maintained an 89.4% annual retention rate. The high annual retention rate suggests that members value the program as an approach to address the clinical quality and nursing workforce development needs in LTC settings.

Trends in HIV Prevention, Treatment, and Incidence in a Hyperendemic Area of KwaZulu-Natal, South Africa

In Africa, the persistently high HIV incidence rate among young women is the major obstacle to achieving the goal of epidemic control. To determine trends in coverage of HIV prevention and treatment programs and HIV incidence. This cohort study consisted of 2 sequential, community-based longitudinal studies performed in the Vulindlela and Greater Edendale area in KwaZulu-Natal, South Africa. Participants enrolled from June 11, 2014, to June 22, 2015 (2014 survey), with a single follow-up visit from June 24, 2016, to April 3, 2017 (2016 cohort), or enrolled from July 8, 2015, to June 7, 2016 (2015 survey), with a single follow-up visit from November 7, 2016, to August 30, 2017 (2017 cohort). Men and women aged 15 to 49 years were enrolled in the 2014 and 2015 surveys, and HIV-seronegative participants aged 15 to 35 years were followed up in the 2016 and 2017 cohorts. Analysis was conducted from January 1 through December 31, 2018. HIV prevention and treatment programs in a real-world, nontrial setting. Trends in sex- and age-specific HIV incidence rates, condom use, voluntary medical male circumcision, knowledge of HIV-seropositive status, uptake of antiretroviral therapy, and viral suppression. A total of 9812 participants (6265 women [63.9%]; median age, 27 years [interquartile range, 20-36 years]) from 11 289 households were enrolled in the 2014 survey, and 10 236 participants (6341 women [61.9%]; median age, 27 years [interquartile range, 20-36 years]) from 12 247 households were enrolled in the 2015 survey. Of these, 3536 of 4539 (annual retention rate of 86.7%) completed follow-up in the 2016 cohort, and 3907 of 5307 (annual retention rate of 81.4%) completed follow-up in the 2017 cohort. From 2014 to 2015, condom use with last sex partner decreased by 10% from 24.0% (n = 644 of 3547) to 21.6% (n = 728 of 3895; P = .12) in men and by 17% from 19.6% (n = 1039 of 6265) to 16.2% (n = 871 of 6341; P = .002) in women. Voluntary medical male circumcision increased by 13% from 31.9% (1102 of 3547) to 36.1% (n = 1472 of 3895); P = .007) in men, and the proportion of women reporting that their partner was circumcised increased by 35% from 35.7% (n = 1695 of 4766) to 48.2% (n = 2519 of 5207; P < .001). Knowledge of HIV-seropositive status increased by 21% from 51.8% (n = 504 of 3547) to 62.9% (n = 570 of 3895; P < .001) in men and by 14% from 64.6% (n = 1833 of 6265) to 73.4% (n = 2182 of 6341; P < .001) in women. Use of antiretroviral therapy increased by 32% from 36.7% (n = 341 of 3547) to 48.6% (n = 432 of 3895; P < .001) in men and by 29% from 45.6% (n = 1251 of 6265) to 58.8% (n = 1743 of 6341; P < .001) in women; HIV viral suppression increased by 20% from 41.9% (n = 401 of 3547) to 50.3% (n = 456 of 3895; P = .005) in men and by 13% from 54.8% (n = 1547 of 6265) to 61.9% (n = 1828 of 6341; P < .001) in women. Incidence of HIV declined in women aged 15 to 19 years from 4.63 (95% CI, 3.29-6.52) to 2.74 (95% CI, 1.84-4.09) per 100 person-years (P = .04) but declined marginally or remained unchanged among men and women in other age groups. This study showed a significant decline in HIV incidence in young women; however, to further reduce HIV incidence, HIV prevention and treatment program coverage must be intensified and scaled up.

Distribution and retention trends of physician-scientists in Japan: a longitudinal study

BackgroundPhysician Scientists (PSs) play a significant role in medical science because of their clinical practice and research expertise. Although it is important to analyze the distribution and retention trends in the number of PSs in Japan, research on this topic has been insufficient. Thus, the purpose of this study is to analyze PSs distribution and retention trends, identify factors related to their retention, and consider the policy implications.MethodI analyzed individual data from 1996 to 2016 from a national census survey that had been administered by the national government of Japan every 2 years. The number of PSs in 1996 and 2016 were 4930 (2.1% of all physicians) and 5212 (1.6%), respectively. I conducted a descriptive analysis and identified retention trends. I then used a multivariable logistic regression analysis to identify the factors related to the retention of PSs.ResultsBetween 1996 and 2016, the total number of PSs in Japan increased by 6%. The number of PSs aged 39 years or younger decreased by 48%, while those aged between 55 and 69 increased by 91%, indicating a notable decrease in the number of PSs under the age of 39. From 2014 to 2016, the annual retention rate of PSs was estimated to be 75.5%, which represented a low and stable rate compared to other physicians over the study period. The odds of continuing to practice as a PS were significantly higher for those who have between 15 to 29 years of experience after qualification as a physician.ConclusionThis study indicates that it is likely for the total number of PSs to decrease in the future. Although the Japanese government has implemented various measures to retain PSs, these have not been effective. Possible new interventions to address this problem include increasing the knowledge of medical students and younger physicians of the role of PSs and the benefits of a career as a PS, providing specific career paths for PSs, securing specific positions for PSs, and increasing the compensation for PSs.

To Grow or Not to Grow: Strategy Development at PGC Basketball

Mano Watsa, President of Point Guard College (PGC) Basketball, is contemplating the next direction to take his organization. His co-owner, Nicole, is adamant that the next five years should be focused on growing PGC Basketball. Like Nicole, Mano would love to see PGC Basketball continue to grow; however, he is skeptical about focusing on growth when the organization is facing some significant challenges. Specifically, PGC Basketball is faced with a low athlete annual retention rate (i.e., 20%) and camps in some regions operating below 70% capacity. In addition, Mano recognizes that PGC Basketball has issues achieving consistency within their operations to ensure quality control, promoting their summer camps within all the markets they serve, as well as attracting and retaining top talent to work as camp instructors. Mano must determine the best strategy to implement for PGC Basketball to continue its success over the next five years.

Retention among full-time occupational physicians in Japan.

To secure human resources for occupational medicine, it is important to analyse occupational physician retention trends and the factors associated with retention. However, little is currently known about this topic. To identify occupational physician retention trends, to identify factors associated with this retention and to discuss the policy implications of the findings. We analysed data from the biannual national physician census surveys conducted by the government of Japan from 2002 to 2014. In this study, those who chose 'working as an occupational physician' as their workplace/type of work from a pre-determined list in the survey questionnaire were considered full-time occupational physicians. We presented retention trends by calculating the annual retention rate for each set of two consecutive surveys. We then used logistic regression to identify factors associated with retention among occupational physicians. The annual retention rate of full-time occupational physicians from 2012 to 2014 was estimated as 76%, which represents a 6% improvement in retention over the study period. The odds of continuing to practise as an occupational physician were higher for occupational physicians working in cities compared with those working in towns or villages. Improving and facilitating smooth transitions between clinical practice and occupational medicine would help to secure human resources in occupational medicine, even if the current trend of low retention continues.

Black Teachers’ Retention and Transfer Patterns in North Carolina: How Do Patterns Vary by Teacher Effectiveness, Subject, and School Conditions?

Despite public interest and government action toward diversifying the teaching workforce in U.S. public schools, our knowledge about the retention and transfer patterns of Black teachers lacks specificity and clarity. In this study, I find that Black teachers’ annual retention rate was about 4 percentage points lower than that of White teachers in North Carolina elementary and secondary schools from 2004 to 2015. This Black-White teacher retention gap can largely be explained by Black teachers’ experience and education and the challenging school and community contexts in which these teachers worked. Compared with White teachers who had similar professional attributes and worked in similar school settings, Black teachers were more likely to stay in schools serving a larger proportion of Black students and to move to a school that served a higher proportion of Black students. The marginal probability of Black teachers’ retention received an additional boost with an increase in teachers’ observational ratings and math value-added scores. Stronger school leadership and higher-quality professional development predict a higher retention rate of more effective Black teachers.

Calculating averted caries attributable to school-based sealant programs with a minimal data set.

We describe a methodology for school-based sealant programs (SBSP) to estimate averted cavities, (i.e., difference in cavities without and with SBSP) over 9 years using a minimal data set. A Markov model was used to estimate averted cavities. SBSP would input estimates of their annual attack rate (AR) and 1-year retention rate. The model estimated retention 2+ years after placement with a functional form obtained from the literature. Assuming a constant AR, SBSP can estimate their AR with child-level data collected prior to sealant placement on sealant presence, number of decayed/filled first molars, and age. We demonstrate the methodology with data from the Wisconsin SBSP. Finally, we examine how sensitive averted cavities obtained with this methodology is if an SBSP were to over or underestimate their AR or 1-year retention. Demonstrating the methodology with estimated AR (= 7 percent) and 1-year retention (= 92 percent) from the Wisconsin SBSP data, we found that placing 31,324 sealants averted 10,718 cavities. Sensitivity analysis indicated that for any AR, the magnitude of the error (percent) in estimating averted cavities was always less than the magnitude of the error in specifying the AR and equal to the error in specifying the 1-year retention rate. We also found that estimates of averted cavities were more robust to misspecifications of AR for higher- versus lower-risk children. With Excel (Microsoft Corporation, Redmond, WA, USA) spreadsheets available upon request, SBSP can use this methodology to generate reasonable estimates of their impact with a minimal data set.

Spatiotemporal patterns in nutrient loads, nutrient concentrations, and algal biomass in Lake Taihu, China

Lake Taihu, China's third largest freshwater lake, exemplifies the severity of eutrophication problems in rapidly developing regions. We used long term land use, water quality, and hydrologic data from 26 in-lake and 32 tributary locations to describe the spatiotemporal patterns in nutrient loads, nutrient concentration, algal biomass, measured as chlorophyll a (Chl-a), in Lake Taihu. Point and nonpoint sources, as determined by chemical oxygen demand, contributed approximately 75 and 25% of the total nutrient loads to the lake, respectively. Spatial patterns in total phosphorus (TP) and total nitrogen (TN) concentrations in Lake Taihu strongly corresponded with observed loads from adjoining rivers with high concentrations proximate to densely populated areas. Chl-a concentrations exhibited spatial patterns similar to TP and TN concentrations. Generally, nutrient and Chl-a concentrations were highest in the northwestern region of the lake and lowest in the southeastern region of the lake. Seasonally, the largest nutrient loads occurred during summer. The annual net retention rate of TP and TN in Lake Taihu was approximately 30% of the total load. This study identifies regions of the lake and the watershed that are producing more nutrients to develop targeted management strategies. Reducing external P and N input from both point and nonpoint sources is obviously critical to address water quality issues in the lake. In addition, atmospheric deposition and resuspension of existing lake sediments also likely play a role in eutrophication processes and harmful algal blooms occurrence.

The Impact of Tariff Structure on Customer Retention, Usage, and Profitability of Access Services

Past research in marketing and psychology suggests that pricing structure may influence consumers' perception of value. In the context of two commonly used pricing schemes, pay-per-use and two-part tariff, we evaluate the impact of pricing structure on consumer preferences for access services. To this end, we develop a utility-based model of consumer retention and usage of a new service. A notable feature of the model is its ability to capture the pricing structure effect and measure its impact on consumer retention, usage, and pricing policy.Using data from a pricing field experiment for a new telecommunication service, we find that consumers derive lower utility from consumption under a two-part tariff than pay-per-use pricing, resulting in lower retention of customers and lower usage of the service. Specifically, our demand analysis shows that a two-part tariff structure leads to an average decline of 10.5% in the annual retention rate and an average decrease of 38.7% in yearly usage relative to pay-per-use pricing after controlling for income effects. Despite the higher customer churn and lower usage, we find that the two-part tariff is still the profit-maximizing pricing structure. However, our results show that if firms ignore the pricing structure (or access fee) effect, then they would overcharge customers for the access fee and undercharge them for the per-minute price. Translated in terms of profitability, the failure to account for the access fee effect leads to a reduction of 11% in firm profit.

An Age‐Dependent Tag Return Model for Estimating Mortality and Selectivity of an Estuarine‐Dependent Fish with High Rates of Catch and Release

AbstractRed drum Sciaenops ocellatus support commercial and recreational fisheries in North Carolina, but the stock was overfished in the 1980s because fishing was unregulated. Subsequent fishery regulations increased subadult survival into adult age‐classes, but overall stock status is difficult to assess because of migration to ocean waters, prohibited harvest of older fish, and relative importance of catch and release. We analyzed 24 years of tagging data from the North Carolina Division of Marine Fisheries to assess the effects of two regulation changes (effected in 1991 and 1998) on fishing mortality rate (F) and selectivity (SEL) patterns of red drum. We used an age‐dependent tag return model that accounted for both harvest and catch‐and‐release fishing. Using external estimates of natural mortality (M) and annual tag retention rate, we obtained precise estimates of annual F; an overall tag reporting rate (λ); and fate‐specific, age‐specific, and regulation‐period‐specific SEL. Estimated F of fully selected red drum was high and variable before 1991 (mean F = 2.38) but decreased in magnitude and variability after 1991. A dome‐shaped pattern of SEL was observed for harvested fish in all regulation periods; maximum SEL occurred at age 2, when red drum were of harvestable size and found in more‐accessible estuarine waters. Selectivity for caught‐and‐released red drum generally decreased for younger ages and increased for older ages in later regulation periods. The λ was estimated at 18% and was generally insensitive to changes in the inputs of M or tag retention rate. As catch‐and‐release fishing increases, tag return models may be important tools for studying fish populations, as long as practical issues, such as λ, tag loss, timing of tagging, and hooking and tagging mortality, are addressed.

Living Wages and Retention of Homecare Workers in San Francisco

This study records the impact on workforce retention of the nearly doubling of wages for homecare workers in San Francisco County over a 52‐month period. Using descriptive statistics and logistic regression analysis the author finds that the annual retention rate of new providers rose from 39 percent to 74 percent following significant wage and benefit increases and that a $1 increase in the wage rate from $8 an hour—the national average wage for homecare—would increase retention by 17 percentage points. The author also shows that adding health insurance increases the retention rate by 21 percentage points.

Lessons of a First-Year Teacher

It seems taboo to question one's commitment to Teach For America and to one's students. But, in fact, Ms. Ness confesses to questioning her commitment nearly every day. WHEN I graduated from college, I joined Teach For America and so committed the next two years of my life to teaching in one of the nation's most underresourced school districts. Now part of the AmeriCorps service program, Teach For America has a clear mission: to give every child - regardless of race, ethnicity, background, or religion - the opportunity to attain an excellent education. Founded a decade ago, Teach For America places more than 800 college graduates every year in impoverished school districts in such urban areas as Baltimore, Los Angeles, and New York City and in such rural areas as the Mississippi Delta and the Rio Grande Valley. Teach For America teachers fill vacancies in districts that suffer from teacher shortages, most often taking the most challenging placements in the most difficult schools. Corps members go through an intensive five-week training program before they are placed in schools. In that training, they focus on theories of education, holding children to high expectations, practical ways of becoming an effective teacher, and leveling the playing field for students who lack the educational opportunities that children from better backgrounds take for granted. Corps members are hired directly by school districts, and many complete state credentialing programs during their two years of service. Upon the completion of their two- year commitment, more than 60% of corps members continue teaching, while the others change paths and move on to graduate schools or to other forms of employment. In my first year of teaching, I was assigned to Roosevelt Middle School in East Oakland, California, an extremely overcrowded school with an annual teacher retention rate of just 60%. The student body is 50% Asian, 25% Latino, and 25% African American. Roosevelt is located in a rough area that is notorious for drug use, and gangs are an ever- present force. Most of my students were not native speakers of English. Indeed, in that first year, my students spoke 10 languages, including Arabic, Cambodian, Spanish, Vietnamese, and Chinese. Many were recent immigrants, and I was expected to teach them conversational and written English, as well as the state-mandated social studies curriculum. Although I had been told before I began my Teach For America commitment that I was about to experience a harsher reality than anything I had previously known, I still believed that teaching was a 9-to-3 job and that I could leave my work at school and keep my personal and professional lives totally separate. I thought I could bring my students into my classroom, shut the door, and leave the problems of their inner-city community outside. I believed that I could instill the love of learning in my students and that they would somehow be able to forget all the turmoil they faced in their lives. I vowed that my passion and enthusiasm for my children and for teaching would never diminish. I would never allow myself to suffer emotionally, as many first-year teachers do. I would stay positive and avoid the disillusionment that so many teachers feel. I would enter my classroom every day with the same energy and passion I started with in September. It wouldn't matter if it was a gloomy Thursday in late October or if I had been battling the flu for two weeks. I would never become the worksheet teacher. Rather than slide grammar worksheets under my students' noses, I would have them build the pyramids out of sugar cubes. I set high expectations not only for my students, but for myself as well. In one swift transformation, I graduated from college, packed my belongings, and drove across the country to start life anew in an entirely unfamiliar environment, without the comforts of family, friends, and home. It was an exciting adventure at first - relocating, getting my first real job, and having the responsibilities of adult life. …

Sample attrition bias in a longitudinal study of young people

Abstract Attrition analyses are reported from a longitudinal survey of young people conducted annually over the years 1980–1988. Not surprisingly, there was considerable sample attrition over the period so that the initial sample of 3,130 was reduced to 483 after eight years. This reflected an average annual retention rate of just under 80%. There was evidence of some selective bias in attrition, particularly during the early years, when those dropping out tended to be of lower academic ability, lower socioeconomic status, and from non-English backgrounds. Although most of the differences were slight, the drop-outs also exhibited greater externality of locus of control and less achievement motivation than those who stayed in, as well as being greater consumers of alcohol, cigarettes, and both non-prescribed and illicit drugs. These results are similar to those that have been reported from other comparable studies conducted in the United States. Implications for the interpretation of longitudinal survey da...

Retention and release of selected major and minor metals by the altamaha river marsh ecosystem

The retention and release of two major metals, K and Mg, and two minor metals, Zn and Mn, bySpartina alterniflora andSpartina cynosuroides salt marsh ecosystems along the terminal course of Altamaha river were investigated. The metal content in plant and soil samples collected from the two sites was measured periodically. A rectangular box-model of the ecosystem (1 m × 1 m × 0.5 m) was used to normalize the metal content of all materials in g m−3. The net annual retention or release of the metals in the ecosystem was computed from the periodic changes in the metal content of the live plant, dead tissues and of the soil (HCI extractable). The system populated byS. alterniflora releases 1.53 g m−3 of Mn while that covered byS. cynosuroides delivers 17.18 g m−3 of Mn to the river. Zinc is retained at the annual rate of 0.17 g m−3 by the former system and 1.21 g m−3 by the latter. The annual retention rate of K and Mg byS. alterniflora system is 71.76 g m−3 and 522.08 g m−3 respectively, whileS. cynosuroides system retains annually 171.0 g m−3 of K and 499.54 g m−3 of Mg.