Boulder Zone Research Articles

Invader–invader interactions in relation to environmental heterogeneity leads to zonation of two invasive amphipods, Dikerogammarus villosus (Sowinsky) and Gammarus tigrinus Sexton: amphipod pilot species project (AMPIS) report 6

As biological invasions continue, interactions occur not only between invaders and natives, but increasingly new invaders come into contact with previous invaders. Whilst this can lead to species replacements, co-existence may occur, but we lack knowledge of processes driving such patterns. Since environmental heterogeneity can determine species richness and co-existence, the present study examines habitat use and its mediation of the predatory interaction between invasive aquatic amphipods, the Ponto-Caspian Dikerogammarus villosus and the N. American Gammarus tigrinus. In the Dutch Lake IJsselmeer, we found broad segregation of D. villosus and G. tigrinus by habitat type, the former predominating in the boulder zone and the latter in the soft sediment. However, the two species co-exist in the boulder zone, both on the short and longer terms. We used an experimental simulation of habitat heterogeneity and show that both species utilize crevices, different sized holes in a plastic grid, non-randomly. These amphipods appear to optimise the use of holes with respect to their ‘C-shape’ body size. When placed together, D. villosus adults preyed on G. tigrinus adults and juveniles, while G. tigrinus adults preyed on D. villosus juveniles. Juveniles were also predators and both species were cannibalistic. However, the impact on G. tigrinus of the superior intraguild predator, D. villosus, was significantly reduced where experimental grids were present as compared to absent. This mitigation of intraguild predation between the two species in complex habitats may explain the co-existence of these two invasive species.

Vertical migration of municipal wastewater in deep injection well systems, South Florida, USA

Deep well injection is widely used in South Florida, USA for wastewater disposal largely because of the presence of an injection zone ("boulder zone" of Floridan Aquifer System) that is capable of accepting very large quantities of fluids, in some wells over 75,000m 3 / day. The greatest potential risk to public health associated with deep injection wells in South Florida is vertical migration of wastewater, containing pathogenic micro- organisms and pollutants, into brackish-water aquifer zones that are being used for alternative water-supply projects such as aquifer storage and recovery. Upwards migration of municipal wastewater has occurred in a minority of South Florida injection systems. The results of solute-transport modeling using the SEAWAT program indicate that the measured vertical hydraulic conductivi- ties of the rock matrix would allow for only minimal vertical migration. Fracturing at some sites increased the equivalent average vertical hydraulic conductivity of confining zone strata by approximately four orders of magnitude and allowed for vertical migration rates of up 80m/year. Even where vertical migration was rapid, the documented transit times are likely long enough for the inactivation of pathogenic microorganisms. Resume Les injections par puits profonds sont largement utilisees au sud de la Floride (Etats-Unis) pour stocker les eaux usees, essentiellement du fait de la presence d'une zone d'injection ("zone des blocs" du Systeme Aquifere de Floride) apte a accepter des quantites considerables de fluides : plus de 75,000m 3 /jour dans certains puits. Le plus

Abstract: Mud Hole: A Unique Warm-Water Submarine Spring Located Offshore Southwestern Florida 

ABSTRACT Hole Submarine Spring is an unusual warm-water submarine discharge of water offshore of the southwestern Gulf Coast of Florida, located at latitude 2615'48N longitude 8201'06W, or about 18.5 km due south of the Sanibel Island lighthouse, Lee County, Florida. This warm-water submarine spring oftentimes has a surface appearance of discolored turbid warm-water which is very attractive to large fish, sharks, turtles, sport fisherman, and scuba divers. The spring discharges warm water from many vents in a sinkhole depression about 61 m in diameter at about 19 m below NGVD. The bottom sediment consists of gray silt and mud atop sand and limestone gravel which, when disturbed, causes clouds of mud to be thrown into suspension, giving the spring the name Mud Hole. Warm water flowing from several orifices has a constant temperature of 35.31C, pH of 7.25, and a salinity of 34.6 ppt (averaged hourly measurements during the period May 5 through June 17,1998). The plume extends about 1.5 m around the main orifice, about 1 m long by 0.3 m wide, with a velocity estimated at 0.6 m/s and a discharge of about 0.17 m3/s (4 million gallons/day). The total discharge from the whole depression is however considerably much larger. This study mapped the spring and measured physical water quality. The results indicated that the discharge movement is fault-related to the basement Sunniland Fracture Zone, based on the geology of southern Florida. The saline-water temperature of 35.3C indicates that the water comes from a considerable depth, as the surrounding seawater only averages 21C and onshore Upper Floridan aquifer water only ranges from 26.6C to 29.4C. The temperature profile in the oil-exploration well, State Lease #224B-1, located offshore north of Sanibel Island indicates that this temperature exists only at a depth greater than 500 m, that is, in the Boulder Zone of the Lower Floridan aquifer. This study concludes that the source is saline water migrating through faults extending from the basement Sunniland Fracture Zone and moving upwards through the section, mixing with the brackish cooler Floridan Aquifer, and eventually flowing from the spring. As no lithological gradient exists from east to west in southern Florida and higher water temperatures are found near major fault zones, the geothermally-activated convective flow cell hypothesis cannot be valid. Based on the data obtained in this study, the source is not considered the surficial aquifer as reported in the literature by some researchers.

Hydrogeology of deep-well disposal of liquid wastes in southwestern Florida, USA

Deep-well injection has been used to dispose of municipal liquid wastes in southwestern Florida since 1988. The liquid wastes are injected into an extremely high-transmissivity zone of fractured dolomite in the Early Eocene Oldsmar Formation of the Floridan aquifer system; this zone is commonly referred to as the Boulder Zone. Data collected during the drilling and operational testing of southwestern Florida injection wells provide insights into the nature of the injection zone and overlying confining beds. The location of high-transmissivity zones that are capable of accepting large quantities of waste water is vertically and horizontally variable and cannot be predicted with certainty. A 40.9-m thick high-permeability interval in one injection well, for example, was absent in a well drilled only 85.4 m away. Some upward migration of low-density injected fluids has occurred, but at no site were the injected liquids detected in deep monitor wells, such as occurred at injection-well sites along the coasts of southeastern, west-central, and east-central Florida. The primary confinement of the injected liquids (i.e., deepest effective confining beds) consists of unfractured beds of low-permeability dolomite within the Oldsmar Formation, whose locations are also laterally and vertically variable. The origin and controls of the distribution of fractures in the Oldsmar Formation are poorly understood.

Dynamics of Late Cretaceous Rocky Shores (Rosario Formation) from Baja California, Mexico

Two rocky-shore deposits are described at localities of Late Cretaceous age in Baja California, Mexico. The main locality, at Las Minas, is characterized by a carbonate matrix containing clasts derived from an underlying andesite flow. Basal boulders give way up section to smaller cobbles and silt, indicating a transgression. The biotas from the sites include encrusting forms (coralline algae, bryozoans, serpulids, ostreids, spondylids), pholadid bivalve borings, and several nestling and mobile taxa. The well exposed boulder zone contains clusters of nestling pectinids preserved in growth position. This is the first such observation from an ancient rocky shore. Echinoids also lived within the relatively stable boulder interstices. Rocky-shore biotas of Late Cretaceous age from around the world contain many elements in common, including large encrusting oysters, spondylids, serpulids, rhynconellid brachiopods, and echinoids. Other groups common to rocky shores today are found at only some Cretaceous localities (e.g., barnacles, trochid and cerithiid gastropods, limpets, chitons). More archaic taxa, such as crinoids and large inarticulate brachiopods, are rarely represented at the known Cretaceous localities. Reconstructions of the biotas of ancient rocky shores offer a new avenue for the study of evolution on hard substrates. As the number and quality of described rocky-shore localitiesmore » increases, it will be possible to put into a broader context evolutionary trends derived strictly from hard-grounds or other hard-substrate types.« less

Pump Testing Boulder Zone Aquifer, South Florida

Pumping tests were performed on a 3,200 ft (976 m) deep injection well tapping the Boulder Zone near Miami, Florida, as a part of the construction and testing of a deep well injection system for the proposed Miami‐Dade Water and Sewer Authority's South District Wastewater Treatment Plant. Testing included a step‐drawdown test and a constant‐rate withdrawal test. The stepdrawdown test was performed at rates of about 2,000 gpm (126 lps), 4,000 gpm (253 lps), and 6,000 gpm (379 lps). The constant‐rate withdrawal test was run at approximately 5,950 gpm (375 lps). Semi‐diurnal (tidal) water‐level fluctuation in the Boulder Zone is approximately 0.40 ft (0.12 m). The quality of the native ground water resembles that of seawater. The effects of the pumping were observed in two nearby deep wells. Transmissivity and storage coefficient of the Boulder Zone calculated from the observed time‐drawdown‐recovery data are about 184×106gpd/ft(2.2×106m2/day) and about 7.7×10-4, respectively.

DEEP WELL DISPOSAL OF SECONDARY EFFLUENT IN DADE COUNTY, FLORIDA1

ABSTRACT: Data were obtained from drilling and testing of a test injection well for deep underground injection of waste water effluent from the proposed 50‐million‐gallon‐per‐day (mgd) South District Regional Wastewater Treatment Plant of the Miami‐Dade Water and Sewer Authority, Dade County, Florida. The drilling operation progressed in stages, each stage coverting the strata to be sealed off by the 48‐inch, 40‐inch, 30‐inch, and 20‐inch casings, respectively. Total depth of the well is 3,200 feet. The top of the saline, cavernous, dolomitic Boulder Zone was found at 2,790 feet below the surface and is separated from the Floridan aquifer above by approximately 1,100 feet of confining limestone layers. These confining layers were determined, by packer testing, to be very effective. The transmissivity of the Boulder Zone was estimated to be 14 × 106 gallons per day per foot (gpd/ft) from the data obtained from pump out tests. An 8,000‐gallon‐per‐minute (gpm) injection test was conducted to confirm well performance under operating conditions. Based on all of the data obtained, it was concluded that underground injection into the Boulder Zone of secondary waste water effluent from the proposed treatment plant is feasible, both hydraulically and environmentally. A monitoring system was proposed to provide a record of the effects of injection on the subsurface environment.

GEOTECHNICAL INVESTIGATIONS DURING DRILLING OF A DEEP DISPOSAL WELL IN DADE COUNTY, FLORIDA

Abstract.A test‐injection well was drilled to a depth of 3,200 feet (976 m) to determine the feasibility of deep underground injection of 50 mgd (190,000 m 3/day) ADF of secondary treated waste water in south Dade County, Florida. Geological formation samples and water samples were collected and analyzed during the drilling of the well and geophysical logging was performed in the well at several stages. At this site, the Floridan aquifer extends from a depth of 920 feet (281 m) to 1,680 feet (512 m) and generally consists of limestone which is fossiliferous in part. Water from this aquifer is brackish, with chlorides ranging from 700 mg/l at the top to 15,000 mg/l at the bottom. The strata from 1,680 feet (512 m) to 2,790 feet (851 m) are essentially nonwater‐producing and act as a confining bed between the Floridan aquifer and the Boulder Zone.The Boulder Zone begins at 2,790 feet (851 m) in depth and consists of a very hard, fractured, cavernous, dark dolomite. The water from this aquifer is very similar to sea water. The subsurface temperature gradient at this site is reversed from the normal gradient, cooling with depth at an average rate of approximately 0.4° F (0.22°C) per 100 feet (30 m). The injection zone extends from approximately 2,830 feet (863 m) to 2,920 feet (891 m) in depth. Results of pumping tests indicate that the Boulder Zone is very transmissive and has a good confining bed above it.

Uranium-isotope variations in groundwaters of the Floridan aquifer and Boulder Zone of south Florida

Water samples from four wells from the main Floridan aquifer (300–400 m below mean sea level) in southeast Florida exhibit 234 U 233 U activity ratios that are significantly lower than the secular equilibrium value of 1.00. Such anomalous values have been observed previously only in waters from sedimentary aquifers in the near-surface oxidizing environments. These four wells differ from six others, all producing from the same general horizon, in being located in cavernous highly transmissive zones. We hypothesize that the low activity ratios are indicative of a relic circulation pattern whereby water from the surface aquifer was channelled to lower levels when sea level was much lower. At a deeper cavernous level, known as the Boulder Zone (800–1,000 m below mean sea level), the U isotopes, along with other chemical constituents, show progressive changes with increasing distance from an inferred flow source in the Straits of Florida. This tends to support the hypothesized landward flow (though with a more northerly component) of cold seawater in the extensively transmissive Boulder Zone.

Subsurface Wastewater Injection, Florida

Deep-well injection of liquid waste is being evaluated in Florida as a management option to help alleviate environmental deterioration of fresh and estuarine waters and increasing problems of waste disposal. Extensive areas of Florida are underlain by permeable saline-aquifer systems that are separated from overlying freshwater aquifers by low-permeability confining materials consisting of clay, evaporites, or dense carbonate rocks. These deep saline zones are the subject of current research designed to assess the environmental impact of subsurface waste storage. Three active deep-well disposal systems currently exist, and two additional systems are under construction. Industrial and municipal wastes are injected into subsurface environments of different hydrogeologic characteristics at depths ranging from 1,400–3,000 ft. Transmissivities of the receiving carbonate aquifers range from 6,500 gpd per ft in northwest Florida to more than 17,000,000 gpd per ft for the cavernous Boulder Zone in southern peninsular Florida

Deep Well Disposal of Waste Waters in Saline Aquifers of South Florida

Florida is underlain by very rich water‐bearing strata commonly referred to as the Floridan aquifer. Solution channels and caverns in carbonaceous rocks are found at different depth intervals in extensive, thick (several thousand feet) sections of limestones and dolomites. In south Florida the bottom part of the Floridan aquifer includes extremely cavernous strata commonly referred to as the ‘Boulder Zone’. Chloride concentration in the water of the Boulder Zone is over 2000 mg/1. Because of this, large volumes of brine from oil fields are reinjected into this zone. Since 1966 industrial waste (essentially 1% acetic acid) has been injected into a disposal well drilled to the top of the Boulder Zone southeast of Lake Okeechobee. Planning and monitoring of this well have included the cooperation of government and private interests. Experiences, results, and potential of this zone for further similar uses are discussed.

A Coral Reef in the New Hebrides

Summary.On the north‐east coast of Gaua, in the New Hebrides, there is a fringing reef about half‐a‐mile wide. Coral growth is most active near the shore, the dominant coral in this zone being Montipora ramosa. Outside the double boulder zone coral growth is not very active, and Lithothamnium does not flourish as it does in so many reefs.It is suggested that a fringing coral‐reef not only grows outwards on its own talus bed, but also grows inwards to form a thin layer lying on a flat shallow platform produced by the erosion of the coast.