Assessing the impact of the Lake Kissimmee restoration on apple snails

Seasonal fluctuations in rainfall occur naturally in Florida, historically producing correspondingly large intra-annual and inter-annual fluctuations in lake water levels. As a result, "normal" lake levels are elusive; the norm is for wide fluctuations, a pattern which earned them the descriptive title, "astatic", or unstable (Brenner et. al. 1990). Lake Kissimmee, in Osceola County, FL, had a mean average water level fluctuation of 1.4 meters, but over several years varied as much as 3.7 meters (Grocki 1975).The substrate and vegetative communities, in part, reflect the pattern of hydrologic fluctuations, their timing, duration, and frequency. Topographic variability in lake systems, coupled with their hydrologic patterns, yield a mosaic of shrubby, emergent and submerged plant habitats in the littoral zone of the lake. Fish and wildlife have adapted accordingly, and successfully forage and reproduce in these highly fluctuating systems. Installation and operation of water control structures over the past 40 to 50 years have dampened the degree of hydrologic fluctuations in many Florida lakes, resulting in long term stabilization oflake levels [Holcomb and Wegener 1971, Wegener et. al. 1974, Fox et. al. 1977, Moyer and Williams 1982, Florida Game and Fresh Water Fish Commission (GFC) 1995]. The mean annual flux on Lake Kissimmee was reduced from 1.4 meters to 0.9 meters (Wegener et al 1973). In addition, increased nutrient inputs to Florida's watersheds from agricultural and urban development have resulted in lake eutrophication (Wegener et. al. 1974, Moyer and Williams 1982). As nutrients increased and water levels stabilized, rooted aquatic macrophytes expanded and organic debris accumulated to form undesirable lake substrates. Fish populations suffer from drops in accumulated to form undesirable lake substrates. Fish populations suffer from drops in dissolved oxygen associated with decaying algae and plant matter, the alteration of plant community composition, and poor habitat quality of the substrate (Wegener and Williams 1974). To remedy these problems in Florida lakes, the Florida Game and Fresh Water Fish Commission initiated a lake restoration program in 1971 which emphasizes the use of a lake draw down to expose sediments (GFC 95). The objective ofthe program is to reduce undesirable plant species, expand desirable plant communities, and consolidate flocculent organic sediments (Holcomb and Wegener 1971, Wegener et. al. 1974, Fox et. al. 1977, Cooke 1980, Tarver 1980, GFC 1995). In addition, muck removal operations following lake level draw downs are meant to resolve the problem of extensive build up of organic sediments (GFC 1995, Moyer et. al. 1995). The goal of the draw down and restoration activity is to improve aquatic habitat in support of fisheries and wildlife while improving lake quality for recreational usage (e.g. sport fishing) (Wegener and Williams 1974, Tarver 1980,. GFC 1995). The Florida Game and Fresh Water Fish Commission (GFC), in cooperation with the South Florida Water Management District (SFWMD), conducted a draw down of Lake Kissimmee from December 1995- June 1996, dropping lake levels by approximately 1.7 meters. The Lake Kissimmee draw down provided an excellent opportunity to investigate the impact of management techniques on an invertebrate which is a critical component of the central lakes food web, the Florida apple snail (Pomacea paludosa, SAY). Although data on the responses of some invertebrate species 2 to draw downs in central Florida are available (Wegener et. al. 1974, Fox et. al. 1977, Butler et. al. 1992), no published studies document the responses of P. paludosa. The Florida apple snail belongs to the tropical family of aquatic snails, Pilidae, which inhabitant wetland areas in Florida, Central and South America, Africa and India. Most Pilidae habitat typically (under natural hydrologic patterns) experiences a seasonal dry down, and the Florida apple snail is no exception. Pilidae snails utilize both a lung and gill for respiration (Andrews 1965). The dual respiratory system enables these animals to tolerate daily and seasonal dissolved oxygen fluctuations, permits egg-laying above water level (eggs thus avoid hypoxia and predation), and, in some Pilid species, enables adults to maintain aerobic respiration during the dry-season (McClary 1964, Burky et al. 1972, Aldridge 1983). Apple snails are critical components of lake food webs in Florida. They are prey to alligators (Alligator mississippiensis)( Delany and Abercrombie 1986), fish (Lepomis microlophus)(Chable 1947), turtles (Trionyxferox) (Dalrymple 1977), and ibis (Eudocimus albus)(Kushlan 1974). Apple snails comprise over 75% ofthe diet of the limpkins (Aramus guaraunaXCottam 1942), and nearly 100% ofthe diet of endangered snail kite (Rostramus sociabilis)(Snyder and Snyder 1969). Although the majority of the snail kite population occupies wetland habitats in south Florida throughout the year, they have been found to emigrate from this area when the dry season escalates into a prolonged drought (Beissinger and Takekawa 1983, Bennetts and Kitchens 1997). Researchers have identified the central lakes system as a critical refuge for the snail kite during these droughts (Beissinger and Takekawa 1983, Bennetts and Kitchens 1997). In 3 addition, the kites have been consistently nesting (even in non-drought years) on Lake Kissimmee and Lake Tohopekaliga since the early 1980's, providing further support (in the form of suitable foraging and nesting habitat) for the endangered kite population (Beissinger and Takekawa 1983, Bennetts and Kitchens 1997). The impetus for the Lake Kissimmee draw down is habitat improvement for fisheries and wildlife (GFC 1995). A conservation priority ranking system for Florida wildlife identifies the snail kite and limpkin, largely due to their specialized diet of apple snails, as deserving special attention for monitoring and management (Milsap et. a1. 1990).Moyer et a1. 1991 specifically recommended an evaluation ofthe impact of lake draw downs on apple snails. In this report we present the findings of a three-year study ofthe immediate and long term impacts ofthe Lake Kissimmee draw down and restoration activity on apple snail populations. The objectives ofthis research are as follows: • To study the impacts oflake restoration activity (e.g. draw down, muck removal) on snail populations in several sites throughout the lake by assessing pre-draw down and post-draw down snail abundance~ • To study the movement patterns of snails to find out what proportion ofthe population migrates to deeper water or become stranded in the dry down area as lake levels recede; • To study the capacity for snails to survive in dry down conditions (Document has 55 pages

Dry Down Tolerance of the Florida Apple Snail (Pomacea paludosa, Say): Effects of Age and Season

This Research Work Order includes three experiments to look at apple snail dry down survival as a function of age and season. Two of those experiments have been completed and the third one will likely run through February (depending on snail survival). The third experiment began on September 2 1, 1998. The detailed results of Experiment # 1 and #2 were reported in the update report of 10/15/98. The overall survival for Experiments #I and #2 are included herein for comparison with Experiment #3. (7 page document

OVERFLOW Simulations of Space Shuttle Orbiter Reentry Based on As-Built Geometry

The Space Shuttle Orbiters Discovery and Endeavor have been digitally scanned to obtain outer mold line surfaces. Using these scans, the existing overset computational fluid dynamics (CFD) grid system will be modified by projecting the grid points to the scanned geometry. Simulations will be performed using the OVERFLOW solver and the results compared to previous OVERFLOW results on the theoretical geometry and the aerodynamic databook. The "bent airframe" term will be compared between the aerodynamic databook and the computations over a range of reentry conditions

Urban transportation: Perspectives on mobility and choice

A study of urban transportation systems are presented characterized by intensive scrutiny of many ideas, philosophies, and academic perspectives. This report is intended to communicate some dimensions of the urban transportation problem to the general public

Mean-risk models using two risk measures: A multi-objective approach

This paper proposes a model for portfolio optimisation, in which distributions are characterised and compared on the basis of three statistics: the expected value, the variance and the CVaR at a specified confidence level. The problem is multi-objective and transformed into a single objective problem in which variance is minimised while constraints are imposed on the expected value and CVaR. In the case of discrete random variables, the problem is a quadratic program. The mean-variance (mean-CVaR) efficient solutions that are not dominated with respect to CVaR (variance) are particular efficient solutions of the proposed model. In addition, the model has efficient solutions that are discarded by both mean-variance and mean-CVaR models, although they may improve the return distribution. The model is tested on real data drawn from the FTSE 100 index. An analysis of the return distribution of the chosen portfolios is presented

Beta decay of 71,73Co; probing single particle states approaching doubly magic 78Ni

Low-energy excited states in 71,73Ni populated via the {\beta} decay of 71,73Co were investigated in an experiment performed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). Detailed analysis led to the construction of level schemes of 71,73Ni, which are interpreted using systematics and analyzed using shell model calculations. The 5/2- states attributed to the the f5/2 orbital and positive parity 5/2+ and 7/2+ states from the g9/2 orbital have been identified in both 71,73Ni. In 71Ni the location of a 1/2- {\beta}-decaying isomer is proposed and limits are suggested as to the location of the isomer in 73Ni. The location of positive parity cluster states are also identified in 71,73Ni. Beta-delayed neutron branching ratios obtained from this data are given for both 71,73Co.Comment: Accepted for publication in PR

Water quality modelling of the Mekong River basin: climate change and socioeconomics drive flow and nutrient flux changes to the Mekong Delta

The Mekong delta is recognised as one of the world's most vulnerable mega-deltas, being subject to a range of environmental pressures including sea level rise, increasing population, and changes in flows and nutrients from its upland catchment. With changing climate and socioeconomics there is a need to assess how the Mekong catchment will be affected in terms of the delivery of water and nutrients into the delta system. Here we apply the Integrated Catchment model (INCA) to the whole Mekong River Basin to simulate flow and water quality, including nitrate, ammonia, total phosphorus and soluble reactive phosphorus. The impacts of climate change on all these variables have been assessed across 24 river reaches ranging from the Himalayas down to the delta in Vietnam. We used the UK Met Office PRECIS regionally coupled climate model to downscale precipitation and temperature to the Mekong catchment. This was accomplished using the Global Circulation Model GFDL-CM to provide the boundary conditions under two carbon control strategies, namely representative concentration pathways (RCP) 4.5 and a RCP 8.5 scenario. The RCP 4.5 scenario represents the carbon strategy required to meet the Paris Accord, which aims to limit peak global temperatures to below a 2 °C rise whilst seeking to pursue options that limit temperature rise to 1.5 °C. The RCP 8.5 scenario is associated with a larger 3–4 °C rise. In addition, we also constructed a range of socio-economic scenarios to investigate the potential impacts of changing population, atmospheric pollution, economic growth and land use change up to the 2050s. Results of INCA simulations indicate increases in mean flows of up to 24%, with flood flows in the monsoon period increasing by up to 27%, but with increasing periods of drought up to 2050. A shift in the timing of the monsoon is also simulated, with a 4 week advance in the onset of monsoon flows on average. Decreases in nitrogen and phosphorus concentrations occur primarily due to flow dilution, but fluxes of these nutrients also increase by 5%, which reflects the changing flow, land use change and population changes

Chemical Gas Sensors for Aeronautic and Space Applications 2

Aeronautic and space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Areas of interest include launch vehicle safety monitoring, emission monitoring, and fire detection. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensors is based on progress in two types of technology: 1) Micromachining and microfabrication technology to fabricate miniaturized sensors. 2) The development of high temperature semiconductors, especially silicon carbide. Sensor development for each application involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this microfabricated gas sensor technology make this area of sensor development a field of significant interest

Valuation of soil health ecosystem services. Vermont Payment for Ecosystem Services Technical Research Report #5

In this report, we present estimates for ecosystem services from soil health using two approaches for four different services. One approach generates estimates based on soil-health practices, and the other approach is based on improvements in soil-health indicators. For soil- health practices, such as adopting best-management practices on annual corn, we utilize a set of off-the shelf empirical models widely used to estimate ecological functions on farm landscapes. For soil-health indicators, we make estimates by linking these tools with soil data and statistical models describing how soil-health parameters influence the interaction of soils with water and their environment. We provide rough monetary estimates of the value of these services, using several different standard ecological economics methods. These results are necessarily rough but can help to elucidate the relative magnitudes of different types of benefits. For millennia, farmers have recognized the importance of soil health for crop productivity and resilience. Recently, scientists, policy-makers, and farmers have become interested in the non-agricultural benefits of healthy farmland soils. Healthy soils can support climate mitigation through carbon sequestration, protect the health of waterways by retaining nutrients and sediments, protect downstream communities by absorbing water and protect the air by regulating gaseous emissions. These and other ecosystem services provided by healthy soils may meaningfully contribute to the health and vitality of communities and ecosystems. In recent years, farms have struggled financially and awareness of environmental problems have grown. Policy-makers worldwide have sought ways to compensate family farms for their environmental stewardship as a means to tackle both these problems. Farmers have organized under the banner of “regenerative agriculture” to experiment with new practices and promote values provided by healthy soils far beyond the farm. Vermont is well-positioned to become a leader in this movement; family farming and environmental stewardship are central to our collective identity and economy. There have been several efforts to develop a policy framework for soil stewardship, but none have succeeded. In 2019, Act 83 of the Vermont Legislature created a working group to explore payments for ecosystem services as a framework for linking farm supports and environmental stewardship. This report was commissioned as part of this effort. To design a program to promote soil ecosystem services, it is necessary to generate an estimate of the magnitude of each of the benefits. If we understand the scale and value of benefits, we can then judge the cost-effectiveness of such a program compared with alternatives, such as investments in other natural systems like forests and wetlands, or investments in hard infrastructure. Because improvements in natural systems can affect many different things we care about, putting total benefits in dollar terms helps us to combine different types of benefits and to assess which benefits are largest