Clay L. Montague

Estuaries of the South Atlantic Coast of North America: Their Geographical Signatures

Estuaries of the southeastern Atlantic coastal plain are dominated by shallow meso-tidal bar-built systems interspersed with shallow sounds and both low flow coastal plain and high flow piedmont riverine systems. Three general geographical areas can be discriminated: the sounds of North Carolina; the alternating series of riverine and ocean dominated bar-built systems of South Carolina, Georgia, and northeast Florida, and the subtropical bar-built estuaries of the Florida southeast coast. The regional climate ranges from temperate to subtropical with sea level rise and hurricanes having a major impact on the regions estuaries because of its low and relatively flat geomorphology. Primary production is highest in the central region. Seagrasses are common in the northern and southern most systems, while intertidal salt marshes composed ofSpartina alterniflora reach their greatest extent and productivity in South Carolina and Georgia. Nuisance blooms (cyanobacteria, dinoflagellates, and cryptomonads) occur more frequently in the northern and extreme southern parts of the region. Fishery catches are highest in the North Carolina and Florida areas. Human population growth with its associated urbanization reaches a maximum in Florida and it is thought that the long-term sustainability of the Florida coast for human habitation will be lost within the next 25 years. Tidal flushing appears to play an important role in mitigating anthropogenic inputs in systems of moderate to high tidal range, i.e., the South Carolina and Georgia coasts. The most pressing environmental problems for the estuaries of the southeastern Atlantic coast seem to be nutrient loading and poor land use in North Carolina and high human population density and growth in Florida. The future utilization of these estuarine systems and their services will depend on the development of improved management strategies based on improved data quality.

A Possible Effect of Salinity Fluctuation on Abundance of Benthic Vegetation and Associated Fauna in Northeastern Florida Bay

In southern Florida, a vast network of canals and water control structures mediate freshwater discharge into the coastal zone. Management protocol for one such canal network (C-111) is being modified in part to try to improve habitat for estuarine fish and wading birds in northeastern Florida Bay, an estuarine part of Everglades National Park. Changes in canal management could alter the spatial and temporal salinity regime in the estuary. To better predict the effect of such changes on estuarine habitat, abundances of submersed vegetation and benthic animals were sampled repeatedly at 12 stations that differed in salinity. A variety of other parameters were also measured (nutrients, light, temperature, oxygen, sediment characteristics, and others). Mean salinity among stations ranged from 11.4‰ to 33.1‰. Densities of benthic plants and animals differed among stations by several orders of magnitude. The standard deviation of salinity was the best environmental correlate with mean plant biomass and benthic animal density: less biota occurred at stations with greater fluctuations in salinity. The two stations with the least plant biomass also had the highest mean water temperatures. In a stepwise multiple regression analysis, standard deviation of salinity accounted for 59% of the variation in the logarithm of mean plant biomass among stations. For every 3‰ increase in the standard deviation, total benthic plant biomass decreased by an order of magnitude. Mean water temperature accounted for only 14% of the variation, and mean salinity was not included for lack of significance. At stations with widely fluctuating salinities, not only was biomass low, but species dominance also frequently changed. Severe fluctuation in salinity may have prevented abundant benthos by causing physiological stress that reduced growth and survival. Salinity may not have remained within the range of tolerance of any one plant species for long enough to allow the development of a substantially vegetated benthic community. Hence, gaining control over salinity fluctuation may be the key to estuarine habitat improvement through canal management in southern Florida.

THE INFLUENCE OF FIDDLER CRAB BURROWS AND BURROWING ON METABOLIC PROCESSES IN SALT MARSH SEDIMENTS

Abstract Effects of burrows and burrowing by fiddler crabs on production and decomposition of organic carbon in a salt marsh on Sapelo Island, G A, were measured. Field experiments determined rate of excavation of organic carbon from belowground; efflux of carbon dioxide from burrows; effect of burrows on growth of Spartina alterniflora; density of roots near burrows; and salinity, pH, phosphate concentration, and ammonium concentration in burrow water. Fiddler crabs transported 26 g organic C m-2 from belowground in July 1979. Annual excavation was estimated at 157 g C m-2, or 20% of the belowground production of S. alterniflora. Mean burrow respiration was 2.1 mg CO2 h-1, accounting for 20% to 90% of salt marsh sediment respiration, depending on marsh wetness. Burrows increased S. alterniflora standing stocks by 23% in high marsh. Chemistry of burrow water was much different from interstitial water. Salinity of burrow water was 20–23°/∞ while that of interstitial water was 37–45°/∞. Burrows also contained high levels of ammonium. The combined effects of added nutrients, lower salinity, greater oxygen, lower sulfide, and greater flow of water through sediments as a result of fiddler crab burrowing are suggested as reasons for the increased standing stock of short S. alterniflora.

Ecological effects of coastal marsh impoundments: a review

Many coastal resource managers believe estuarine marshes are critically important to estuarine fish and shellfish, not only because of the habitat present for juvenile stages, but also because of the export of detritus and plant nutrients that are consumed in the estuary. Concern has been widely expressed that diking and flooding marshes (impounding) for mosquito control and waterfowl management interferes with these values of marshes. Major changes caused by impoundment include an increase in water level, a decrease in salinity, and a decrease in the exchange of marsh water with estuarine water. Alteration of species composition is dramatic after impoundment. Changes in overall production and transport phenomena, however—and the consequences of these changes— may not be as great in some cases as the concern about these has implied. Although few data are available, a more important concern may be the reduction of access by estuarine fish and shellfish to the abundant foods and cover available in many natural, as well as impounded, marshes. Perhaps even more important is the occasional removal of free access to open water when conditions become unfavorable in impounded marsh that is periodically opened and closed. Collection of comparative data on the estuarine animal use of various configurations of natural and impounded marshes by estuarine animals should lead to improved management of both impounded and unimpounded marshes.

Viruses in drinking water

Viral infections have a long history of association with drinking water supplies. Evidence of waterborne transmission is predominantly based on epidemiological data. Water-borne transmission has only in exceptional cases been confirmed by direct detection of viruses in drinking water supplies. This is because the majority of viruses typically transmitted by water (enteric viruses) are not detectable by conventional methods. However, molecular techniques based on the reverse transcriptase-polymerase chain reaction (RT-PCR) available now, have made it possible to detect low levels of a wide variety of enteric viruses. This preliminary study deals with 411 analyses of drinking water supplies carried out over a period of two years. The drinking water supplies were derived from acceptable quality surface water sources using generally accepted treatment and disinfection processes. Glass wool filters were used for the on-site and in-line recovery of viruses from 100 to 1000 litre volumes of water. Viruses eluted from the glass wool were inoculated onto combinations of cell cultures including the BGM monkey kidney, PLC/PRF/5 human liver and CaCo-2 human colon carcinoma cell lines, as well as primary vervet monkey kidney cells. The purpose of cell culture inoculation was to isolate cytopathogenic viruses, to amplify the nucleic acid of non-cytopatho genic viruses, and to confirm viability of viruses. After two passages cell cultures were homogenised and analysed by RT-PCR for a variety of enteric viruses. Positive results were recorded for 24 % of the samples. Enteroviruses were detected in 17 % of the samples, adenoviruses in 4 % and hepatitis A virus in 3 %. None of the viruses were cytopathogenic, which implies that they would not be detected by conventional cell culture propagation techniques. These findings are in agreement with reports on the detection of viruses in drinking-water supplies in other parts of the world. The results also support epidemiological studies which indicate low level transmission of viral infections by drinking water supplies which have been treated and disinfected by acceptable procedures and meet quality specifications for indicators such as coliform bacteria. All the water supplies analysed in this study had heterotrophic plate counts of less than 100/1 ml, total and faecal coliform counts of 0/100 ml, and negative results in qualitative presenceabsence tests for somatic and F-RNA coliphages on 500 ml samples. These findings support earlier evidence on shortcomings of conventional indicators for assessment of the virological quality of drinking water. The results have various implications. For instance, the water supplies analysed here, and probably many others, would fail national and international quality guidelines which state that drinking water should be free of viruses. However, since these guidelines are based on outdated viral detection methods, they may be considered due for revision to accommodate new molecular technology. This may not be an easy decision because the viruses detected by the technology described here are at least potentially infectious and may be regarded to constitute a health risk. Retention of the existing guidelines would have major cost and technical implications for the water industry. The results of this investigation underline the need for more detailed studies.

Impacts of the Deepwater Horizon Oil Spill on Salt Marsh Periwinkles (Littoraria irrorata).

Deepwater Horizon was the largest marine oil spill in U.S. waters, oiling large expanses of coastal wetland shorelines. We compared marsh periwinkle (Littoraria irrorata) density and shell length at salt marsh sites with heavy oiling to reference conditions ∼16 months after oiling. We also compared periwinkle density and size among oiled sites with and without shoreline cleanup treatments. Densities of periwinkles were reduced by 80-90% at the oiled marsh edge and by 50% in the oiled marsh interior (∼9 m inland) compared to reference, with greatest numerical losses of periwinkles in the marsh interior, where densities were naturally higher. Shoreline cleanup further reduced adult snail density as well as snail size. Based on the size of adult periwinkles observed coupled with age and growth information, population recovery is projected to take several years once oiling and habitat conditions in affected areas are suitable to support normal periwinkle life-history functions. Where heavily oiled marshes have experienced accelerated erosion as a result of the spill, these habitat impacts would represent additional losses of periwinkles. Losses of marsh periwinkles would likely affect other ecosystem processes and attributes, including organic matter and nutrient cycling, marsh-estuarine food chains, and multiple species that prey on periwinkles.

Patterns of fish use and piscivore abundance within a reconnected saltmarsh impoundment in the northern Indian River Lagoon, Florida

Nearly all saltmarshes in east-central, Florida were impounded for mosquito control during the 1960s. The majority of these marshes have since been reconnected to the estuary by culverts, providing an opportunity to effectively measure exchange of aquatic organisms. A multi-gear approach was used monthly to simultaneously estimate fish standing stock (cast net), fish exchange with the estuary (culvert traps), and piscivore abundance (gill nets and bird counts) to document patterns of fish use in a reconnected saltmarsh impoundment. Changes in saltmarsh fish abundance, and exchange of fish with the estuary reflected the seasonal pattern of marsh flooding in the northern Indian River Lagoon system. During a 6-month period of marsh flooding, resident fish had continuous access to the marsh surface. Large piscivorous fish regularly entered the impoundment via creeks and ditches to prey upon small resident fish, and piscivorous birds aggregated following major fish movements to the marsh surface or to deep habitats. As water levels receded in winter, saltmarsh fish concentrated into deep habitats and emigration to the estuary ensued (200% greater biomass left the impoundment than entered). Fish abundance and community structure along the estuary shoreline (although fringed with marsh vegetation) were not analogous to marsh creeks and ditches. Perimeter ditches provided deep-water habitat for large estuarine predators, and shallow creeks served as an alternative habitat for resident fish when the marsh surface was dry. Use of the impoundment as nursery by transients was limited to Mugil cephalus Linnaeus, but large juvenile and adult piscivorous fish used the impoundment for feeding. In conclusion, the saltmarsh impoundment was a feeding site for piscivorous fish and birds, and functioned as a net exporter of forage fish to adjacent estuarine waters.

Simulated populations of the black salt march mosquito (Aedes taeniorhynchus) in a Florida mangrove forest

A simulation model of the population dynamics of the black salt marsh mosquito (Aedes taeniorhynchus) in a mangrove basin forest in southwestern Florida is described. This mosquito is a major pest in coastal Florida, with large populations migrating many kilometres from the breeding site. The basic model realistically simulated annual population trends and the occurrence of larval broods. Model output (adult females and sum of eggs, larvae and adult females) was most sensitive to adult survival, larval predator populations and immigration of adult females. Detailed analysis of dispersal indicated that persistence of mosquitoes was dependent upon immigration and the absence of tidal flooding and attendant larval predators. Model versions incorporating fish-mediated oviposition repellency and increased survival in young autogenous adult females led to a respective 21% decrease and 267% increase in mean adult female population. These results suggest that a model offering alternative, predator-free oviposition sites for migrating females would more realistically simulate natural populations.

A causal hypothesis explaining predator-prey dynamics in Great Salt Lake, Utah

Abstract A hypothesis explaining the recurring annual plankton dynamics found in a natural two-species system in Great Salt Lake, Utah is developed, and tested via computer simulation. A springtime peak of the phytoplankter Dunaliella viridis is followed by a peak of the sole grazing zooplankter Artemia salina . The annual time patterns of these two species are analyzed using Forresters feedback dynamics methodology. The goal is to obtain a model with coupled feedback loops sufficient to reproduce the major features shown in three years of field data (e.g., spring phytoplankton blooms and crashes followed by zooplankton). Some details are ignored until a sensitivity analysis has revealed important needed information. For example, we consider an average liter of water, at an average depth, in a homogeneous lake; and we include only eggs, nauplii and adults in the brine shrimp life cycle. Emphasis is given to overall pattern reproduction and model stability. The system is driven by solar energy, but the dynamics arise primarily from the feedback loop structure. Feedback loops included are the life cycles of algae and brine shrimp; algal self-shading; algal grazing by brine shrimp; and brine shrimp starvation. The algae are hypothesized to be limited in spring by self-shading, and then by grazing until the fall disappearance of brine shrimp, when the algae become temperature- and light-limited. Brine shrimp are limited only by food.

Recovering the Sand Deficit from a Century of Dredging and Jetties along Florida's Atlantic Coast: A Reevaluation of Beach Nourishment as an Essential Tool for Ecological Conservation

Abstract A sand deficit on Floridas Atlantic coast affects sea turtle nesting, dune ecosystems, and storm protection. Ecological benefits of restoring very large deficits could exceed ecological costs. Dredging and beach nourishment databases revealed sand disposal dynamics and deficit size. Dredge-and-fill activities increased after 1950, peaked in the 1980s, then declined somewhat. Most sand disposal accompanied channel and harbor deepening; little was primarily for beach nourishment. Until the 1970s most dredged material was placed outside the coastal sand-sharing system (offshore and upland). After 1970, beach and nearshore disposal rapidly increased, but generally involved sand already within the system. Moreover, offshore and upland disposal did not immediately decline. To date, little sand has been returned. By 2003, net removal totaled ∼130 × 106 m3. Channels and harbors increased by ∼70 × 106 m3, leaving 60 × 106 m3 of standing sand deficit. Jetties could have redistributed another 70 × 106 m3 from beaches and dunes to inlet shoals. Overall, loss of beaches and dunes could approach 130 × 106 m3. Engineering responses to past objections have improved both habitat suitability and longevity of nourished beaches. Through field trials and adaptive management principles, ecologists could now develop beach nourishment into a management tool to rebuild lost habitat, restore the sand deficit, and stockpile additional sand before nonessential channels and harbors are allowed to refill. With large projects, sand from offshore, upland, and ebb shoal sites and natural wave energy for stable beach building, beach and dune habitat can be restored within decades, better preparing threatened animals for rising sea level.