Jorge R. Rey

Habitat Segregation of Mosquito Arbovirus Vectors in South Florida

Abstract Oviposition traps set in rural to urban environments in three south Florida counties were colonized predominantly by Culex quinquefasciatus Say (35.1%), Aedes albopictus (Skuse) (34.5%), Aedes aegypti (L.) (23.8%), and Culex nigripalpus Theobald (6.6%) during 1 yr of monthly sampling. Significant differences were detected among counties for abundances of Cx. quinquefasciatus and for percentage composition of that species and Ae. albopictus. Aerial images of habitats around each collection site were digitized, and coverages by each of 16 habitat variables were recorded. Abundances of Ae. aegypti were positively related to habitat variables associated with urbanization and negatively correlated to those reflecting rural characteristics. Multiple regression models of habitat selection explained similar proportions of variances in abundance of Ae. aegypti and Ae. albopictus, but signs of significant variables were opposite for these two species. No consistent trends of habitat associations were observed among counties for the two Culex spp. Co-occurrences of the four species in individual traps depended on container type (tub versus cup), and, for Aedes spp. with Culex spp., county. The results underscore the importance of scale in evaluating habitat selection and the utility of quantifiable habitat characteristics of intermediate scale to identify site characteristics favored by the arboviral vectors Ae. aegypti and Ae. albopictus. RESUMEN Trampas de oviposición localizadas in tres condados del sur de Florida fueron colonizadas principalmente por Aedes aegypti (L) (23.8%), Aedes albopictus (Skuse) (34.5%), Culex quinquefasciatus Say (35.1%), and Culex nigripalapus Theobald (6.6%) en muestreos mensuales durante un año. Se encontraron diferencias significativas entre los condados en la abundancia de Cx quinquefasciatus y en el porcentaje de esa especie y de Ae. albopictus. Imágenes aéreas de cada sitio de colección fueron digitalizadas y la cobertura por cada una de 17 variables relacionadas con el habitáculo fué anotada. La abundancia de Ae. aegypti fué correlacionada positivamente con variables relacionadas a la urbanización, y negativamente con aquellas que reflejan características rurales. Modelos de regresión múltiple de selección de habitáculo explicaron proporciones similares de la varianza en abundancia de Ae. aegypti y de Ae. albopictus pero los signos de las variable significativas fueron opuestos para las dos especies. No SE encontraron patrones consistentes algunos entre los condados para las dos especies de Culex. Cohabitación de las cuatro especies en las trampas dependió del tipo de trampa (tinas o tazas) y, para Aedes spp con Culex spp., en el condado. Los resultados recalcan la importancia de la escala de medidas y la utilidad de características cuantificables del habitáculo a escala media para identificar características de sitios preferidos por los vectores de arboviruses Ae. aegypti y Ae. albopictus.

Rehabilitation of impounded estuarine wetlands by hydrologic reconnection to the Indian River Lagoon, Florida (USA)

Salt marshes of the Indian River Lagoon, Florida (USA) were once prolific producers of mosquitoes. Mosquitoes lay their eggs on the infrequently-flooded high marsh surface when the soil surface is exposed. The eggs hatch when the high marsh is flooded by the infrequent high tides or summer rains. To control mosquito production, most of the salt marshes (over 16.200 ha) were impounded by the early 1970s. Flooding, usually by pumping water from the Lagoon, effectively controlled mosquitoes.However, impounding had a profoundly negative impact on the wetland plant, fish, and invertebrate communities. Isolation from the Lagoon cut off aquatic access by transient estuarine species that used the wetlands for feeding or as nursery area. In one study, the number of fish species dropped from 16 to 5 after impounding. Wetland vegetation within some impoundments was totally eliminated; other impoundments developed into freshwater systems.When tidal exchange is restored through hydrologic connection, usually by culverts installed through the perimeter dike, recovery to more natural conditions is often rapid. In one impoundment where wetland vegetation was totally eliminated, recovery of salt-tolerant plants began almost immediately. In another, cover of salt-tolerant plants increased 1,056% in less than 3 years. Fisheries species that benefitted the most were snook, ladyfish, and striped mullet. Over 1,500 juvenile snook were captured in a single 3-hr flood-tide culvert trap as they attempted to migrate into an impoundment. The zooplankton community rapidly returned to the more typical marsh-Lagoon community. Water quality and sediment sulfides returned to typical marsh values. Overall, reconnection enhances natural productivity and diversity, although water quality in the perimeter ditch, an artifact of dike construction, remains problematic.Earlier experiments demonstrated that flooding only during the summer mosquito breeding season provided as effective mosquito control as year-round flooding. In standard management, the impoundment is flooded in summer, then left open to the Lagoon through culverts the rest of the year. Culverts are typically opened when the fall sea level rise first floods the high marsh.Impoundment reconnection is being implemented by a multi-agency partnership. The total reconnected area is expected to reach 9,454 ha by the end of 1998, representing 60% of the impounded wetlands in the entire IRL system. One stumbling block is private ownership of many of the remaining isolated impoundments.

Vegetation dynamics in impounded marshes along the Indian River Lagoon, Florida, USA.

Data are presented on the vegetation dynamics of two impounded marshes along the Indian River Lagoon, in east-central Florida, USA. Vegetation in one of the marshes (IRC 12) was totally eliminated by overflooding and by hypersaline conditions (salinities over 100 ppt) that developed there in 1979 after the culvert connecting the marsh with the lagoon was closed. Over 20% recovery of the herbaceous halophytesSalicornia virginica, S. bigelovii, andBatis maritima was observed at that site after the culvert was reopened in 1982, but total cover in the marsh remains well below the original 75%. No recovery of mangroves was observed at this site. The second site (SLC 24), while remaining isolated from the lagoon during much of the study, did not suffer the complete elimination of vegetation experienced at the first site. At this location, mangroves increased in cover and frequency with a concomitant decrease in herbaceous halophytes.Considerable damage to the vegetation was evident at IRC 12 when the impoundment was closed and flooded for mosquito control in 1986. Although the damage was temporary, its occurrence emphasizes the need of planning and constant monitoring and adjustment of management details as conditions within particular marshes change. Storms and hurricanes may be important in promoting a replacement of black mangroves by red mangroves in closed impoundments because the former cannot tolerate pneumatophore submergence for long periods of time.

Effects of re-establishing tidal connections in two impounded subtropical marshes on fishes and physical conditions

The effects of reestablishing a marsh-lagoon connection through culverts upon the fish populations and the physical conditions of two impounded sub-tropical marshes are examined. After installation of the culverts, mean salinities in the two marshes increased from approximately 13 ppt to 25 ppt and pH from 7.1 to 7.3. The abundance of marsh resident species, particularly those that forage in the upper marsh, decreased significantly after connection, but utilization of the marshes by transient species increased by almost two orders of magnitude. Modification of the marsh hydroperiod seems to be most important in influencing the changes in the patterns of fish utilization, abundance, and diversity observed at the study sites.

Factors affecting mosquito production from stormwater drains and catch basins in two Florida cities

ABSTRACT Mosquito production from drains and catch basins in the cities of Vero Beach and Key West, FL were monitored from May 2004 through August 2005. A total of 48,787 mosquitoes were captured during the study. Of these, over 99% belonged to two species, Culex nigripalpus Theobald (2,630) and Culex quinquefasciatus Say (45,946). Other species collected included Culex restuans Theobald, Culex salinarius Coquillett, Aedes aegypti (L.), Aedes albopictus (Skuse), and Uranotaenia lowii Theobald. Significantly greater numbers of Cx. nigripalpus were collected at Vero Beach than at Key West, but no significant differences in numbers of Cx. quinquefasciatus and in total numbers of mosquitoes between the two cities were evident. Rainfall, salinity, type of structure, structure setting, and presence or absence of predators or competitors influenced the numbers of mosquitoes collected and/or the frequency of positive, negative, dry, or flooded samples.

Sulfide variation in the pore and surface waters of artificial salt-marsh ditches and a natural tidal creek

Pore and surface water sulfide variation near artificial ditches and a natural creek are examined in salt marshes bordering the Indian River Lagoon in east-central Florida. Pore water sulfide concentrations ranged from 0 μg-at I−1 to 1,640 μg-at I−1. On average, the natural creek had the lowest sulfide concentrations (mean <1.0 μ-at I−1) and the perimeter ditch of a managed salt marsh impoundment the highest (436.5 μg-at I−1). There was a trend of increasing sulfide concentration in the summer, and sharp peaks in late fall-early winter which correspond with peak litter input into the sediments. Significant differences in sulfide concentration between sites are attributed to differences in water flow and in organic matter content. Delaying the seasonal opening of culverts (which connect impounded marshes with the lagoon) until lagoon water levels rise in fall may prevent massive fish kills that have been associated with high sulfide levels in the impoundment perimeter ditches.

Above-ground primary production in impounded, ditched, and naturalBatis-salicornia marshes along the Indian River Lagoon, Florida, U.S.A.

Yearly above-ground production estimates in natural, ditched, and impounded high salt marshes along the Indian River Lagoon in east central Florida ranged from 834.9 g/m2 in the impounded marsh to 2.316.5 g/m2 in the natural one. Mosquito control activities in the impounded marsh prior to the start of this study resulted in larger stocks of dead and litter biomass there during the first year than at the other two marshes. High soil temperature and salinity during the summer may have caused a decrease in production during that season. Annual tumover rales varied from 5.8 at the impounded marsh during the first year to 1.1 at the impounded marsh and at a nearby ditched marsh during the second year. Prduction was inversely correlated with flooding frequency. No significant differences were found in the rates of litter loss from any of the sites, but litter from the impounded marsh had greater organic content than litter from the open and the ditched marshes. The data suggest that flooding for mosquito control during the summer can curtail production, but the effects upon yearly production are minor, as production during the summer is naturally low.

North American Wetlands and Mosquito Control

Wetlands are valuable habitats that provide important social, economic, and ecological services such as flood control, water quality improvement, carbon sequestration, pollutant removal, and primary/secondary production export to terrestrial and aquatic food chains. There is disagreement about the need for mosquito control in wetlands and about the techniques utilized for mosquito abatement and their impacts upon wetlands ecosystems. Mosquito control in wetlands is a complex issue influenced by numerous factors, including many hard to quantify elements such as human perceptions, cultural predispositions, and political climate. In spite of considerable progress during the last decades, habitat protection and environmentally sound habitat management still remain inextricably tied to politics and economics. Furthermore, the connections are often complex, and occur at several levels, ranging from local businesses and politicians, to national governments and multinational institutions. Education is the key to lasting wetlands conservation. Integrated mosquito abatement strategies incorporate many approaches and practicable options, as described herein, and need to be well-defined, effective, and ecologically and economically sound for the wetland type and for the mosquito species of concern. The approach will certainly differ in response to disease outbreaks caused by mosquito-vectored pathogens versus quality of life issues caused by nuisance-biting mosquitoes. In this contribution, we provide an overview of the ecological setting and context for mosquito control in wetlands, present pertinent information on wetlands mosquitoes, review the mosquito abatement options available for current wetlands managers and mosquito control professionals, and outline some necessary considerations when devising mosquito control strategies. Although the emphasis is on North American wetlands, most of the material is applicable to wetlands everywhere.

Coastal wetland management in Florida: environmental concerns and human health

High mosquito populations have always been a part of Florida’s environment. While mosquito-transmitted diseases have played a major role in Florida’s history, saltmarsh mosquitoes have not been implicated in these disease outbreaks. However, the impact of high saltmarsh mosquito numbers on the well-being of residents and visitors cannot be underestimated. Coastal wetland management efforts in Florida, which date back to the 1920s, have included ditching, dredging and filling, and impounding, all having mosquito control and environmental benefits and liabilities. In the early 1980s, efforts to encourage coastal wetlands management for both mosquito control and environmental interests came to the forefront. This resulted in the Florida Legislature creating the Florida Coordinating Council on Mosquito Control and its Subcommittee on Managed Marshes. Through the efforts of these committees, a heavy investment in research, interagency cooperation, and public acquisition of coastal wetlands property, tremendous progress has been made in management of coastal wetlands. This has occurred largely by implementing management and restoration techniques that minimize environmental impacts, allow for mosquito control, and minimize the need for pesticide use. Continued efforts are needed to place into public ownership remaining privately owned coastal wetland property to allow implementation of best management practices on these important habitats.

Sampling zooplankton in shallow marsh and estuarine habitats: Gear description and field tests

Pump and net samplers for collecting zooplankton from very shallow marsh and estuarine habitats are described. Their use is illustrated with data obtained in salt marshes along the Indian River lagoon in east-central Florida. In general, both pump and net samplers were found to be satisfactory for sampling zooplankton in these areas. Larger sample volumes were obtained with gear utilizing 202 μ mesh sizes than with gear using 63 μ mesh because the latter became clogged very quickly. Quantitative and qualitative similarity between samples collected with different gear was moderate to low. Comparison of the kinds and densities of taxa captured with the various gear indicate that a combination of techniques may be needed to ensure a proper description of the plankton communities of the area.