In overview NOAA's Florida Bay Science Program has had three overall objectives: improving our physical understanding of Florida Bay (three projects); characterizing the Bay ecosystem and recent changes (five projects); and two projects that address anthropogenic pollution. The full FY96 project reports submitted are given verbatim below under their respective themes.
Improving our physical understanding and/or modeling of Florida Bay's interconnection and dependence upon regional oceanographic and meteorological processes are the general goals of three of the individual projects. They represent the NOAA contribution to a larger Interagency effort attempting to develop, initialize and run in operational mode a Bay Circulation model which is in turn part of the still larger effort to develop, initialize and run in operational mode a coupled oceanographic, hydrological and atmospheric model of the South Florida penninsula.
1) "Regional Boundary Conditions for Florida Bay"
F.
Aikman III, W. O'Connor and G. Mellor.
The project goal is to provide accurate physical (water levels, currents,temperature and salinity) boundary condition information to modelers and investigators working in the South Florida region and in Florida Bay. The total water level is probably the single most important parameter for any hydrodynamic modeling effort in Florida Bay, thus we are initially focusing on providing this, coordinating as closely as possible with the Corps of Engineers modeling effort in Florida Bay. To this end the Princeton Ocean Model (POM) is being applied for the Gulf of Mexico/Caribbean (GOM) region to provide this information, based on atmospheric and tidal forcing of a barotropic (two-dimensional; vertically integrated) version of the POM. Work to date can be summarized as follows:
Accomplishments to date can be summarized as follows:
Aikman, F. III, G. L. Mellor, T. Ezer, D. Sheinin, P. Chen, L. Breaker,
K. Bosley, and D. B. Rao. 1996. Towards an operational nowcast/forecast
system for the U.S. East Coast. In: Modern Approaches to Data
Assimilation in Ocean Modeling. P. Malanotte-Rizzoli (Editor). Elsevier
Oceanography Series, 61, 347-376.
2) "Reconstruction and Simulation of Episodic
Meteorological Events and Local Weather Regimes which affect the South
Florida Ecosystem"
M. Powell, C. Mattocks, S. Houston, E. Swartz
and P. Herbert
ARPS Modeling: A critical bottleneck in this project, the lack of sufficient computational resources, was overcome early this summer when a high-powered (DEC Alpha) unix workstation was purchased by the Hurricane Research Division at NOAA-AOML. This eliminated expensive remote supercomputer cycles and accelerated ARPS development.
ARPS has been extended to actually predict the amount and the distribution of rainfall. Previously, only moisture convergence and the locations of dry convective cells could be predicted. With the implementation of the Kessler warm rain microphysics (which simulates the conversion between water vapor, cloudwater, and rain water) and the Anthes-Kuo convective parameterization (for organizing convection on the mesoscale), realistic looking precipitation patterns have been replicated along the sea breeze front. Because the development of the sea breeze, the onset of convective systems, and the dispersion of atmospheric pollutants are sensitive to the depth of the planetary boundary layer (PBL), its determination is of great practical concern. ARPS has recently been enhanced to predict the PBL height as a function of time and stability.
Work has also progressed in initializing ARPS from real-time operational model history files (fields from NMC/NCEP Meso-ETA model forecasts). A GRIB (GRIdded Binary) dataset decoder was developed and donated to CAPS scientists, who modified it for use. Initializing ARPS from a realistic 3-D heterogeneous atmospheric state should substantially improve the realism of the atmospheric simulations, particularly for cold frontal passages, and tropical weather systems which track through the region.
The achievement of these important milestones in the development of the ARPS atmospheric numerical weather prediction model makes the generation of high-resolution simulations of rainfall and surface winds, and their application as tactical decision aids (TDAs) in Everglades restoration management, a near-term possibility.
Episodic Meteorological Event Reconstruction: Two papers describing the reconstruction of Hurricane Andrew's surface wind field were published (Powell et al, 1995, 1996). These papers document the methods used to develop wind fields for past tropical cyclones that have affected Florida Bay.
Most of the recent work in reconstructing extreme wind fields has been in collecting, digitizing, quality controlling, and analyzing the surface wind fields for Hurricane Donna, which affected the Florida Bay region during 9 - 10 September 1960. The data were derived from a number of sources, including journals, newspapers, microfilm records, and the "storm folder" archive at the National Hurricane Center. Data include: surface reports from light houses, coast guard installations, surface aviation facilities, Weather Bureau Offices, Department of Defense installations, CHURN (Co-operative Hurricane Network) reports, microfilm images of WSR-57 radars located at Key West and Miami, U.S. Navy aircraft reconnaissance observations and National Hurricane Research Project flights into Donna before and during the time Donna traversed Florida Bay. A background wind field was constructed for 1900 UTC, 9 September 1960, about ten hours before the center passed over the keys. This analysis will be combined with surface measurements obtained during landfall to produce a wind field representative for the storms passage across the bay.
With the assistance of students from Florida International University and MAST Academy, the program is setting up the archival of images of the wind fields on the AOML World Wide Web (WWW) site for access by other Florida Bay researchers. Cases to be made available include Hurricanes Donna (1960) and Andrew (1992), as well as Tropical Storm Gordon (1994). Interested research scientists will soon be able to retrieve data from this event/regime archive (additional storms will be added as they become available). Snap shots of the streamline and isotach fields for each storm are being generated for a 2 x 2 degree Latitude domain centered on Florida Bay and for the storm center at 6-12 h intervals, depending on the translation speed of the storm. This domain encompasses Florida Bay and should also be suitable for those interested in studying extreme wind affects on the southern end of the Everglades. Gridded data sets will be generated manually upon request for user-specified domains and grid resolutions.
Objectives for FY97:
Atmospheric Modeling
Episodic Meteorological Event Reconstruction
3)
"Florida Bay circulation and exchange study"
T. Lee and L.
Johns
Ongoing Research: An observational study of the interaction and exchange of Florida Bay with the connecting coastal waters of the Gulf of Mexico and the Atlantic in the Florida Keys was initiated in August 1995. Field work began December 1995. The research is designed to address several of the key scientific questions presented in the NOAA/COP Florida Bay Implementation Plan as critical to understanding the functioning of the ecosystem and future evolution from restoration actions. In particular, the research will address the following questions: 1) To what degree is the circulation of water within Florida Bay coupled to that of the surrounding coastal and oceanic environments? 2) What is the relationship of surface and groundwater flows through the Everglades to the salinity of Florida Bay? 3) Is the quality of the water flowing from the Bay contributing to the degradation of corals along the reef tract of the Florida Keys in the Atlantic Ocean?
Observational methods consist of a combination of synoptic shipboard surveys, in-situ moorings and Lagrangian surface drifters to describe and quantify the circulation within the Bay as related to local forcing and coupling with the waters of the Atlantic and Gulf. These observations will also help to provide necessary boundary conditions for future physical and biological models.
Progress - Field Work: Five hydrographic surveys of Florida Bay and the surrounding waters, have been completed and they consist of seasonal surveys of winter, spring and summer conditions that include the hydrological cycle from dry to wet seasons, and surveys before and following the passage of a major winter storm. A 20 ft. shallow draft catamaran, the R/V Miller, owned by the NOAA Southeast Fisheries Center has been equipped with a continuous flow thermosalinograph/fluorometer and a broad band 600 KHz Acoustic Doppler Current Profiler (ADCP) for conducting the hydrographic surveys in Florida Bay and nearby waters. A five mooring current meter array has been maintained since December 1995. Time series of current, temperature, conductivity and bottom pressure are being collected in western Florida Bay and adjacent southwest Florida shelf and Florida Keys coastal waters to determine the degree and variability of coupling of Florida Bay to surrounding waters. Obtained 3 month surface drifter trajectories from two satellite tracked drifters over the winter/spring period. Quantitatively determined the tidal and net transports through the major exchange passages between the Florida Keys over tidal periods during winter and summer seasons using a 600 KHz broad band ADCP mounted between the hulls of R/V Miller.
Progress - Scientific Results: The Shark River discharge forms a narrow low-salinity plume that is advected towards Florida Bay and the Keys to the southeast by a net background flow of 1 to 4 cm/s. Plume widths range from about 2 to 20 km and vertical stratification can be up to 3 psu per 3 m water depth near the river mouth. Plume shape and salinity structure is a function of seasonal and episodic river discharge, local wind forcing and tidal mixing. Extensive exchange between the waters of the western Florida Bay and the Gulf of Mexico occurred during the passage of an intense cold front, but little exchange occurred in the northeast interior portion of Florida Bay. High chlorophyll concentrations are observed in Key West Harbor and in the low salinity plume downstream of the river mouth, indicative of planktonic uptake of riverborne nutrients. Drifter trajectories show evidence of a cyclonic recirculation between West Cape Sable and Cape Romano. Synthesis of drifter trajectories from this project and those deployed in a coordinated DEP project indicate a net southeastward flow from the Gulf of Mexico to the Florida reef track through western Florida Bay that varies with season, stronger in the winter (3 to 4 cm/s) and weaker in summer (1 to 2 cm/s). Drifter trajectories are strongly influenced by local tide and wind forcing. A multiple linear regression model is used to explain approximately 70 to 80% of the subtidal variance of drifter currents due to local wind forcing. The cause and variability of the residual backgound currents are unknown at this time.
Net volume transport through Channels 5, 2 and Long Key Channel combined is estimated at 1500 - 2000 m3/s toward the southeast. Net flow through Seven Mile Bridge is also estimated about 2000 m3/s towards the southeast. This is equivalent to the peak river discharge onto the southeast U. S. shelf by all the rivers between Florida and Cape Hatteras. Approximately 1000 - 1500 m3/s flows through Long Key Channel alone, which is about 200 times greater than the peak fresh water discharge out of Shark River. Also we found that all surface drifters deployed near Shark River and in the western part of Florida Bay were observed to exit Florida Bay toward the reef track through Long Key Channel. Therefore it appears that waters from Shark River and the seagrass die-off region of western Florida Bay will be passively advected and dispersed toward the Florida Keys Marine Sanctuary (FKNMS) primarily through Long Key Channel by this strong mean southeastward flow. The advective/dispersal time-scale for materials in the Shark River Plume to reach the FKNMS is estimated from drifter trajectories at one to two months.
Current meter data indicate that the maximum cross-shelf flow in the FKNMS from Key Largo to the Dry Tortugas occurs in the outer shelf of the Long Key region. After entering Hawk Channel and the reef track the drifter trajectories were either northeast or southwest depending on the direction of the alongshore wind. Several drifters were entrained by the Florida Current and one was ejected out of the Florida Current northeast of Cape Hatteras into a warm-core ring and recirculated within this ring as it slowly progressed to the southwest in the Middle Atlantic Bight (MAB). This drifter trajectory has percipitated a collaboration on larval recruitment in the MAB with J. Churchill (WHOI) and D. Hess (NMFS) and shows the connectivity between the Gulf of Mexico, Florida Bay, Keys coastal waters and the MAB.
Objectives for FY97: As part of the overall south Florida ecosystem restoration project the SFWMD and U. S. Army COE are planning to redistribute surface water flow to the Everglades by increasing the flow to Shark River slough. The ultimate fate and exchange pathway of this increased discharge into the southwest Florida shelf adjacent to western Florida Bay is unknown. Initial trajectories of satellite tracked surface drifter releases in the low-salinity Shark River plume reveal a high degree of spatial and temporal variability in the exchange pathway of waters discharged from Shark River. Drifter trajectories show a cyclonic recirculation between West Cape Sable and Cape Romano, followed by a net advection through the seagrass die-off region of western Florida Bay and ejection into the FKNMS through Long Key Channel. The drifter trajectories are further complicated by a high degree of variance due to local tide and wind forcing, which also may contribute to a significant seasonal variability in the Lagrangian patterns and advective flow rates. We propose to quantify the statistical behavior of the exchange pathway of Shark River discharge by conducting monthly releases of pairs of Argos satellite tracked Davis type drifters offshore of Shark River in the low-salinity plume over a two year period. Nutrient and chl a concentrations along the drifter pathways will be determined during ongoing seasonal surveys as part of the Florida Bay Circulation study. Drifter releases will be done with ENP personnel and facilities. Drifter trajectories will be analyzed with spline fitting and filtering techniques to remove tidal fluctuations and compute current vectors. Drifter currents will then be modeled with linear multiple regression to determine local wind forcing influence. Residual background currents will be compared to sea surface slopes between the Gulf of Mexico and Keys coastal waters from horizontal barotropic pressure gradients derived from the moored array of the circulation study to investigate the cause of the net southeastward flow toward the Keys and its seasonal variability. Large-scale sea level slopes between the Gulf of Mexico and the Atlantic in the Straits of Florida will be investigated using satellite derived (TOPEX) sea level data and compared to bottom pressure and current measurements. We are also proposing to enhance the moored array in the vicinity of the Shark River discharge with bottom ADCP's and conductivity recorders to better understand the fresh water plume variability in relation to backgroud currents. The proposed enhancement of drifter releases are essential for evaluating the statistical behavior of particle pathways from numerical models being developed for Florida Bay circulation. These drifter trajectories together with nutrient and chlorophyll data being collected by other projects are critical to understanding the influence of redistribution of surface waters to the Shark River slough on seagrasses and plankton communities of Florida Bay, and impact on the coral reefs of the FKNMS.
4) "Monitoring and Evaluation of Radar Measured Rain
Estimate over Florida Bay and the Everglades"
F. Marks, P.
Willis, D. Churchill, P. Herbert
This project was initiated in the
late summer of 1995 and the first flights were made in the early Fall of
1995. Its objective is the tuning of radar rain estimation algorithms so
that the The NEXRAD data now being generated from the Miami site, and the
new not yet commissioned Key West site, can be effectively used to
accurately characterize the rainfall amount and distribution over the
peninsula and Florida Bay. The present rain gage network is simply too
sparse and inaccurate given the highly convective nature of rainfall
events
in the Florida Bay/Everglades system, to provide an adequate
measure of the rainfall input to the system. The standard NEXRAD
algorithms were developed largely for non-tropical conditions, and may
not be applicable to this system. The best possible NEXRAD product is the
only way to obtain the requisite data. Airborne rain drop distributions,
a continuous point measurement of surface distributions from a
distrometer at the Everglades Research Center, and surface measurements
from a mobile van, as well as all available rain gage data are being used
to tune the radar-rain algorithm for the specific conditions that prevail
over the Florida Bay/Everglades system.
Ongoing Research: NEXRAD (WSR-88D) hourly digital precipitation array (DPA) data have been archived for the 1996 rainy season. These data have been made available in near real time on the InterNet (http://www.rsmas.miami.edu/groups/hdp/). The Key West NEXRAD has been operating, though not commissioned, and these data are also being evaluated.
Airborne rain drop size distributions made with a Particle Measurement Systems laser rain drop spectrometer, and airborne radar data, have been collected over South Florida to tune the NEXRAD rain estimation algorithm for the maritime/tropical rain regime present over South Florida. Five NOAA P-3 flights in support of this objective have been accomplished to date, 3 in 1995 and 2 in 1996.
A rain drop distrometer has been operated continuously during the 1996 rainy season at the NPS Everglades Research Center, along with a high resolution rain gage. This continuous record of one minute rain drop size distributions will also be used in algorithm development and tuning. The rain measurement at this point is being compared to the NEXRAD rain estimate for this grid point.
The same instrument (PMS) that we use in the aircraft was installed in a mobile van. This instrument has been used to collect surface rain drop size distributions over South Florida during the 1996 rainy season. This data set will complement the continuous point distrometer data and the aircraft data in algorithm development.
We attempted to collect aircraft data over the surface distrometer, and the surface van measurements for case studies to define any differences in rain distributions aloft versus those on the surface.
Objectives for FY 97:
5) "Assessment of trophic structure and responses of fish and
shellfish to changes in habitat in Florida Bay"
D. Hoss, G.
Thayer, A. Powell, P. Tester, and M. Robblee
During FY 96 research was continued to address changes in the distribution and abundance of living resources in Florida Bay and the question dealing with trophic relationships in the Bay in response to declining seagrasses, increased plankton blooms and altered salinity conditions relative to a decade previous. The field sampling program has dealt with phytoplankton, zooplankton, ichthyoplankton, juvenile and resident fishery organisms, with respect to distributions of salinity and seagrass habitats within Everglades National Park waters of Florida Bay. Techniques, specifically those for all but phytoplankton, used are those employed a decade previous in published evaluations of the ecology of the Bay, and by-and-large the stations are identical or similar.
At least 23 genera of phytoplankton have been identified, with centric diatoms dominating, and high chlorophyll levels possibly reflecting the presence of Synechococcus sp. at many of the stations sampled. Preliminary analyses of 1984 and 1994 ichthyoplankton samples collected at similar but not identical stations suggests higher zooplankton densities during the 1984 sampling period at many of the stations, although the differences are less than 10-fold in most cases.
Ichthyoplankton sampling is demonstrating that spotted seatrout spawning is highest in the western portion of Florida Bay adjacent to the mainland from Cape Sable to Crocodile point, along the edge of the Gulf of Mexico, and in portions of the central and western interior of the Bay. Otolith aging and back-calculation indicate that intensive spawning occurs in August, but occurs from May through September.
The resident-fish association work in Johnson Key Basin and in four bay-wide strata, have shown that Thalassia has decreased in most areas sampled, but that in some areas (e.g., Johnson Key Basin) there are indications of increases in Halodule. In Johnson Key Basin, caridean shrimp and total fish were considerably lower in abundance in 1995 than during the same months of 1985, with the rainwater killifish and the caridean shrimp Thor having declined by 97% and 93%, respectively. Increases here were in bay anchovy. Bay-wide sampling is demonstrating that there are numerous areas of the Bay where seagrasses have declined considerably since 1984, and that there have been an overall decrease in numerical abundance of resident fish. Changes in the composition of the fishery community also are being observed. For example Gobiosoma robustum and Harengula jaguana, neither very dense, are currently about twice as abundant as they were in 1984-85 collections, whereas Bairdiella chrysoura, Opsanus beta, and Syngnathus scovelli all remain at similar densities on the average. Other species, and in particular the rainwater killifish, have decreased significantly. Bay anchovy has become the numerically dominant species, representing almost 60% of all fish we collect by high speed bottom trawl compared to representing about 1% of fish collected a decade previous. The changes noted both in the quantitative sampling in Johnson Key Basin and in the high speed trawling evaluations, continue to indicate a shift from a benthic-epibenthic feeding community in large areas of the Bay to one dominated by planktivores. This may be a response to habitat changes in terms of increased turbidity and/or decreased benthic structure (e.g., the seagrasses), or to a decrease in salinity.
6) "The trophodynamic
roles of zooplankton in Florida Bay"
M. Dagg and P. Ortner
Phytoplankton blooms are commonly thought to be controlled by nutrients and light. Certainly these factors, and temperature, are the major determinants of phytoplankton growth rate. But blooms are the result of an accumulation of cells. Whether the cells grow rapidly or slowly, they can accumulate if they are not grazed, do not sink or are otherwise not lost to the system. Blooms then, are the result of imbalance between phytoplankton growth rate and loss processes. It is our intent to examine the dominant loss process for phytoplankton, zooplankton grazing, and to compare grazing losses to algal growth rates or productivity rates. One of the general goals of this work is to understand the dynamics of phytoplankton blooms in Florida Bay. Another is to characterize the trophodynamic role of these animals. Who is eating them and what percent of their diet might these constitute? We have now collected and analyzed the abundance and distribution of holoplankton and meroplankton larger than ca. 20um. at a series of stations across the bay at bimonthly intervals for the past two years. More recently we have started to examine the gut contents of larval and juvenile planktivorous fishes and to estimate zooplankton grazing.
First, the grazing role of copepod nauplii were examined. During the past twelve months, the concentration of copepod nauplii was determined at eight sites within Florida Bay on a bimonthly basis. Copepod nauplii were measured for length and width, and an equivalent spherical diameter was determined. It was also determined that an average of 18% of an individual's volume was lost in preservation. Therefore, all size date for the Florida Bay nauplii were corrected and live sizes were used to calculate the volume for each nauplius. Temperature-compensated conversion factors, derived from the literature, were then used to estimate carbon weight (mg C ind-1), respiration rate (m1 O2 ind-1h-1), and metabolic requirements (mg C ind-1 d-1) for each nauplius. These data were applied to the projects measured abundances of nauplii at each site to determine the metabolic requirements of the nauplius community at each site (mg C m-3 d-1).
It was determined that nauplii at six of the sites in Florida Bay require between 0 - 3.5 mg C m-3 d-1 to meet their metabolic demands, eqivalent to a food requirement of approximately 0.2 - 11.5 mg C m-3 d-1. Sites 11 and 15 had much higher food requirements, sometimes exceeding 28.5 mg C m -3 d-1. These community ingestion rates need to be specifically compared to primary production rates to determine what percentage of daily productivity is being consumed by the naupliar community. But assuming production rates of at least 1000 mg C m -3 d-1 suggests that ingestion of phytoplankton by the community of copepod nauplii accounts for only a small fraction of the phytoplankton production. Similar calculations are currently being made for larger zooplankton including copepods and other organisms including meroplankton. In addition to estimates based on metabolism for some larger organisms we will have estimates that are species specific from gut fluorescence. These will be compared to metabolic estimates wherever possible.
In anticipation that the microzooplankton (possibly protozoa) will be the major grazers on phytoplankton in Florida Bay, we have begun to include the grazing of this component of the zooplankton community. Experiments were conducted at one site in July and September 1996, with plans in place to continue bi-monthly experiments for at least the next year. Determination of whole community grazing rates is made with the dilution technique using unprefiltered water samples in comparatively large volumes (2l). Bottles are incubated at 50 % light in situ for 24 h.
In July, phytoplankton growth rates in ambient water and in water with added nutrients were not different, suggesting that ambient growth was not limited by nutrients. The growth coefficient was 1.50 day-1, indicating the phytoplankton community would double every sixteen hours without grazing. The grazing coefficient was 0.77 d-1, which indicates a loss of approximately 75% of the phytoplankton standing crop per day. In September, phytoplankton growth coefficient was even higher than July, 1.90 day--1, and the grazing coefficient was also higher, 1.36 day-1. Clearly, phytoplankton growth rate was very high in this location during both months, and local water column zooplankton grazing was the major fate of this production, although some production was available for other processes (other grazers, sinking, advection to another part of the system, or accumulation in the water column).
7) "The sediment record as
a monitor of natural and anthropogenic changes in the lower
Everglades/Florida Bay ecosystem"
T. Nelsen, P. Blackwelder, H.
Wanless, J. Trefry, P. Swart, and L. Tedesco
Investigators from NOAA-AOML, University of Miami/RSMAS, Florida Institute of Technology and Indiana University/Purdue University at Indianapolis have pooled expertise to study the sediment record from the Florida Everglades, Florida Bay, and the interface between them. The objective is to evaluate the natural and anthropogenically-induced changes over at least the last century. This retrospective analysis is built upon an integrated interdisciplinary study employing geological, geochemical and biological investigations
Field Work: Presently, at the end of the first fully-funded year of work, significant progress has been made in recovering interpretable sedimentary sequences from the Everglades/Florida Bay ecosystem that have proven to be ideal for evaluating anthropogenically-induced changes within this natural system. To date, reconnaissance cores have been successfully collected covering a region from the Shark River Slough to the First National Bank and a subsequent suite of study cores representing the Everglades coastal salinity gradient of the Shark River Slough area and Coot Bay. This transect has the potential to represent the changing influence of discharge from Shark River Slough to the adjacent marine environment while Coot Bay has provided an opportunity to evaluate how the sediment sequence has recorded known historical changes and influences (opening and closing of Coot Bay Canal connection with Florida Bay; Hurricane of 1935 and 1960). In total, 21 cores were taken in 1994, six in 1995, and seven reconnaissance and study cores in 1996.
Stratigraphy: Recognition that sediments in this study area can have disrupted stratigraphic sequences due to bioturbation (macrobenthos, plant roots, ...) is critical to reconstruction of meaningful historical interpretations of project data. To this end each core has been X radiographed and evaluated for stratigraphic integrity. From the above recovered cores, those that have passed this rigorous quality-control criteria are currently being analyzed. Thus far our investigations indicate:
Geochemistry: Isotope-based (210Pb, 137Cs) geochronolgy has indicated both recovery of interpretable stratigraphic sequences and time horizons that extend back at least 100 years thus spanning the period of interest. A geochemically-supported baseline for natural Hg levels in sediments from the study area was established using Al and organic C data. Results show that Hg levels were 5X natural levels in sediments deposited at the mouth of Shark River Slough since 1950. Anthropogenic loading of Hg was progressively lower in post-1950 sediments from the lower Shark River, Ponce de Leon Bay and the more isolated Coot Bay. Pre-1950s sediment show limited Hg enrichment at each site when using geochemically normalized data. A similar trend was observed for lead. Preliminary carbon and oxygen isotopic analyses of ostracod valves reveals changes associated with inputs of freshwater at certain intervals in the core. The oxygen and carbon isotopic composition strongly co-vary and the oxygen values change from heavy values, characteristic of evaporative situations to light values during periods when excess precipitation takes place. As sampling and analyses progress these data will be placed within a temporal context for paleoenvironmental reconstruction.
Paleoecology: Historical change in water flow and microfaunal variability over time are related. This relationship permits utilization of benthic faunal community characteristics for reconstruction of environments back in time to pre-management conditions. Results to date indicate that the overall ostracod community structure and morphologic variability within particular species are strongly salinity related. Moreover, apparent salinity-related shifts in benthic foram community structure are observed within particular genera. These shifts will not only be compared to ostracodes but to oxygen stable isotope data for these same samples. Progress in palynology includes both the creation of the first tropical-pollen reference set for the Everglades, which will serve as a standard for all project pollen identification, and the creation of the first WWW site for such. In addition, detailed pollen facies maps for current surface environments have been created to assess how pollen assemblages record vegetative community structure and this has been placed within a GIS context. These data will soon be subjected to statistical analyses to determine how meaningful vegetative shifts are manifested in the pollen paleo-record. Processing and identification of pollen from cores is underway. This, in concert with statistical data analysis noted above will allow meaningful paleoecological interpretations.
Future Work: This is envisioned to include additional sampling in other critical areas throughout the southernmost portion of the Everglades and Florida Bay. From experience, we have demonstrated that our retrospective-analysis methods have been successfully applied in other study areas and thus we are optimistic about the present study. When viewed together, experience, current results and anticipated progress provides a positive outlook for being able to place, within a temporal context, anthropogenic impacts on the lower Everglades/Florida Bay ecosystems, as preserved in the sediment record. From this we anticipate establishing a pre-anthropogenic paleoecological base line against which to measure restoration efforts as well as paleo-water column conditions for a historical context in which to place present water-column studies.
8) "An integrated study of
pink shrimp as indicators of habitat health in Florida Bay"
J.
Browder, N. Erhardt, V. Restrepo, J. Nance, M. Robblee, and P.
Sheridan
The project objectives were to determine: A) functional relationships between pink shrimp growth and survival and environmental variables, such as salinity and temperature and B) determine sources of two or more within-year cohorts in fishery landings, in terms of space and timing. Progress toward these objectives can be summarized as follows:
In order to understand the causes of the phytoplankton blooms in Florida Bay, the sources of the nutrients need to be known. It is hypothesized that benthic nutrients are a major source and are examining the role of sediment resuspension and the transport of nutrients between the sediments and the water column. Our primary objective is to determine if present phytoplankton blooms are promoted primarily by benthic nutrients. Such knowledge will allow one to predict how various management practices may or may not reduce these phytoplankton blooms. This project seeks to determine if the distribution of the blooms corresponds to the distribution of nutrients in the sediments or the pattern of sediment resuspension.
Stations in Florida Bay and out to the Florida Reef Tract have been set up and collected both water and sediment samples. Methods have been developed and tested. Water column and sediment samples have been processed although some analyses remain to be completed. Chlorophyll concentrations range from as high as 6.21 ug/l in Florida Bay to as low as 0.13 ug/l at the offshore stations. Turbidity ranges from as high as 99 NTUs in Florida Bay to as low as 0.01 NTUs offshore. Salinities range from 15 to 37.4 ppt. Dissolved phosphate concentrations in the water column range from 0.01 to 0.16 uM, nitrate from 0.02 to 4.68 uM, ammonia from undetectable to 28.85 uM, and silicate from 1.83 to 127.91 uM. Nutrients were considerably higher in Florida Bay than at the offshore stations. Porewater ammonia concentrations ranged from 15.86 to 1531.15 uM ,porewater nitrate from 0.09 to 2.25 uM, and porewater phosphate from undetectable to 10.75 uM. The highest porewater nutrient concentrations were at stations in Florida Bay closest to Upper Matecumbe Key. The sampling program has only recently begun, so while patterns are seen in the data, it would be premature to evaluate the data for support of any particular hypotheses at this time.
Two studies of anthropogenic pollution were funded by the NOAA Florida Bay program in FY95:
10) "An Ecotoxicological Assessment of Agricultural Nonpoint Source
Runoff into Florida Bay and Surrounding Environments With an Emphasis on
the Organochlorine Insecticide Endosulfan"
G. Scott, M. Fulton,
P. Key, E. Wirth, G. Thayer and T. Chandler
Background:
Both field and laboratory research was conducted in FY96 to assess the
potential for contaminant loading of agricultural pesticides via nonpoint
source (NPS) runoff into Florida Bay and resulting effects on living
marine resources. Field studies were focused on measuring the occurrence
of agricultural pesticides, such as endosulfan, in water, sediment and
biota (oysters and fish) within the environs of Florida Bay so that a
potential risk assessment characterization could be made. The
deteriorating conditions of Florida Bay [increased phytoplankton blooms,
declines/death in sea grass beds and coral reef communities, and trophic
shifts in fish communities towards more herbivorous fish species] may be
related in part to increased contaminant loadings from upland adjacent
terrestrial environments including both urban and agricultural areas.
Urban contaminants are primarily polycyclic aromatic hydrocarbons (PAHs),
some trace metals (e.g. Cu) and pesticides associated with urban
landscaping (e.g. chlorpyrifos), termitacide control (formerly chlordane
and presently chlorpyrifos), and golf course maintenance (chlorpyrifos
and other insecticides as well as numerous herbicides and fungicides).
Agricultural pesticides were of greatest concern because of the large
concentration of vegetable farming in close proximity to Florida Bay.
Vegetable farming requires high intensity pesticide control (>20 pounds
of active ingredient pesticide per acre/crop). Often there may be more
than one crop per year may further increase the amount of pesticides
used. Agricultural pesticides of concern include azinphosmethyl,
fenvalerate and endosulfan because of their high toxicity potential to
aquatic organisms (Supertoxic = 96h LC50 values of <10 ug/L base U.S.
Fish and Wildlife hazard ranking) and high prevalence rate in coastal
fishkills (e.g. endosulfan was the primary pesticides involved in coastal
fishkills in the U.S. from 1980-89.
Endosulfan was chosen as a
contaminant for further toxicological studies because of the high usage
on vegetable crops (e.g. >70% of the endosulfan in the southeastern U.S.
is applied to vegetable crops in the south Florida), the moderately high
KOW (3.50-4.57), high acute toxicity potential (96h LC50 values of <1.00
ug/L for many for many shellfish and juvenile fish species), the very low
marine water quality criteria (0.0085 ug/L) and its known endocrine
disrupting capabilities demonstrated in vivo laboratory studies
when compared to estrogen and DES. Laboratory studies were focused on
assessing the potential for endosulfan to be an endocrine disrupting
chemical to crustaceans using the grass shrimp (Palaemonetes
pugio) as a water column model and the copepod (Amphiascus
tenuiremis) as a sediment model for ecotoxicology risk assessment.
Field Monitoring Studies: The design of field studies
for monitoring was to collect surface water samples from a grid of
stations approximating a gradient of sites including: 1) Land based
stations (adjacent to agricultural areas near Homestead, Florida which
drain into the C111 Canal); 2) Land estuarine stations (where
agricultural NPS runoff may enter Florida Bay); and 3) Bay stations
(within Florida Bay). At each station, surface water samples were
collected and analyzed for a variety of pesticides including insecticides
and herbicides. At selected stations sediments were collected for
chemical analysis as well as toxicological analysis using a 14 day
chronic copepod (Amphiascus tenuiremis) sediment toxicity test
(this allowed for field and laboratory comparisons). Additionally,
oysters were deployed at selected field sites and measured for survival,
condition index, gonadal index and the uptake of selected pesticides.
Results of fields studies conducted during 1993-95 indicted the presence
of endosulfan and other pesticides in surface waters from Florida Bay and
surrounding environments. Initial sampling indicated the presence of
endosulfan in both agricultural areas as well as in Florida Bay waters,
indicating further study of this issue was warranted. In 1993-94,
detectable levels of endosulfan were measured ranging from 0.017- 0.155
ug/L, but only in surface waters adjacent to agricultural areas.
Similarly, detectable concentrations of atrazine ranging from 0.005-0.194
ug/L were measured but only in surface waters adjacent to agricultural
areas. During 1995, detectable concentrations of endosulfan were measured
in both bay sites and agricultural areas. In Florida Bay, 39% of the
sites had detectable endosulfan concentrations ranging from
Spatial statistical analysis of these
data indicated that the mean endosulfan I isomer concentrations in the
bay was 0.001168 ug/L (+/- 0.000188) versus mean concentrations of
0.006538 ug/L (+/- 0.004378 ug/L) in agricultural areas. These data
suggest that endosulfan I concentrations were reduced by 83% in the bay
relative to concentrations measured in areas adjacent to agricultural
areas. Similar results have been found in bays in Texas for other
pesticides (aldicarb, carbofuran and atrazine) as concentrations declined
by 90% in going from drainage ditches adjacent to agricultural areas to
shallow Texas bay waters (Scott et al., 1992). Additionally, the
endosulfan II isomer was only detected in surface waters in the
agricultural areas and in those bay sites in close proximity to the C111
canal (e.g. Barnes Sound, Long Sound and Manatee Bay). These findings for
the spatial distributions of endosulfan II suggest that the source of the
endosulfan is from agricultural runoff.
In addition to endosulfan,
other pesticides were measured with high frequency including
chlorthalonil (73.6% of sites sampled), chlorpyrifos (94.7%),
alpha-chlordane (42%), gamma chlordane (68.4%),t-nonachlor (100%),
alpha-HCH (73.6%), gamma-HCH (47.3%) and trifluralin (5.2%) at
concentration which would not be acutely toxic( <0.002600 ug/L).The high
prevalence rate of these pesticides as well as endosulfan raises the
issues of the potential additive chronic toxicity of these pesticides to
living marine resources of Florida Bay, since many of these pesticides
are known Endocrine Disrupting Chemical (EDCs), with the potential to
disrupt and alter development and reproduction. Recent studies published
in Science (McLaughlin et al., 1996) and Environmental Health
Perspectives (Sota et al., 1995) in both in vivo and animal studies have
demonstrated that endosulfan is clearly an estrogen mimic in vertebrates
and that combinations of pesticides in small doses (< than concentrations
which cause significant binding with estrogen receptors), including
endosulfan, have greater than additive estrogenic activity (e.g. implying
the potential for synergistic effects). EDCs effects are different than
traditional toxicological concerns in aquatic toxicology in that small
doses may be as effective as high doses in altering endocrine function
and compounds which are not estrogen agonist may be androgen agonist
(e.g. estrogen antagonist), either of which may cause endocrine
disruption. Additionally, EDCs may be most effective during sensitive
stages of development (e.g. molting stages in crustaceans and during
differentiation/development in fish embryos) and effects may be
transgenic, manifesting effects in subsequent generations. Most
current aquatic toxicity testing models are not designed to adequately
evaluate the transgenic effects of EDCs. Chandler (1992) has developed a
copepod life cycle assay which allow for multiple generational testing
(F0 --->F1---->F2 generational testing) within a 28 day period with both
survival and reproduction/development endpoints. Field sediments were
collected from a variety of sites (end of the C111 canal, Joe Bay, Little
Madeira Bay and Barnes Sound) in Florida Bay as well as two Florida Bay
control sites and a laboratory reference sediment (pristine North Inlet
in South Carolina) and tested for their chronic toxicity potential in a
partial life cycle test (F0 - -->F1) using the marine benthic copepod
Amphiascus tenuiremis. Twenty five barren females and 25 males are
introduced to test sediments for 14 days. Test end points included: Adult
survival (male, gravid females and nongravid females), egg production per
female, nauplii production, and copepodite production. Results indicated
significant (p <0.05) reductions in the % of surviving males (e.g.
selective male toxicity=Joe Bay and the end of the C111 canal), reduced
nauplii production (end of the C111 Canal, Little Madeira Bay and one
Florida Bay site), and reduced clutch size per female at several sites,
using ANOVA as well as multiple comparisons (Dunnett's and Tukeys)
statistical analysis. Additionally, the % of gravid females ranged from
69-82% (X=74.4%) in Florida Bay reference and control sediments versus
36-58% (X = 51%) at all Florida Bay Sites (an overall 31.5% reduction in
the % gravid females). Although this difference was not significant (p <
0.09), the reduced clutch size and reduced naupliar production are
suggestive of potential alterations in reproduction and development in
copepods in certain regions of Florida Bay. Of additional interest is the
finding of selective male toxicity at certain Florida Bay sites (Joe Bay
and the end of the C111 Canal). Many lipophilic compounds (e.g.
ogranochlorine pesticides) are more toxic to males than females as
females are able to off load these contaminants into eggs/offspring
during reproduction. This was observed with Kepone in the James River in
blue crabs and other species. Studies are underway to identify any
potential toxic compounds in the sediments used in these toxicity tests.
Of particular interest are the sediments from Joe Bay since the highest
endosulfan concentration detected in oysters by the NOAA NST Program were
found there. Reduced benthic copepod production may have significant
ecological implications since they are primary grazers on phytoplankton
within Florida Bays well as a major food source for many marine/estuarine
fish and shellfish species. Given the significant algal blooms and shifts
in trophic structure among macropelagic fish populations towards
increased herbivorous fish species which have occurred recently in
Florida Bay, the role if any that decreased copepod production may play
warrants further study. Collaborations with Dr. Gary Kleppel, who is
studying distributions of major water column copepod populations within
Florida Bay, are planned which will focus on the toxicity potential of
pesticides to pelagic copepod species. Results of oyster studies
involving deployment of oysters at the end of the C111 Canal, a Florida
Bay reference site and a SC laboratory reference have indicated
significant reductions in condition and gonadal indices in oysters from
the end of the C111 canal. These findings are consistent with results of
studies of agricultural NPS runoff in South Carolina in which significant
reductions in condition and gonadal indices were observed immediately
down stream of a major vegetable farming area following significant
runoff events in which oysters bioconcentrated endosulfan (30 113 ug/kg)
and other insecticides. Ernst (1977) similarly found reduced gonadal
production in mussels exposed to endosulfan. Analysis of oyster tissues
are underway to determine if deployed oysters bioconcentrated
contaminants from surface waters/sediments at each site and if the
observed effects can be correlated with chemical contaminant exposure.
Laboratory Toxicity Tests: Results of laboratory toxicity tests
with crustaceans (grass shrimp = P. pugio and copepods =
Amphiascus tenuiremis) evaluating the potential for endosulfan to
act as an EDC are underway and have focused on four major areas: 1)
Alterations in lipid (fatty acids, cholesterol, and fatty acid methyl
esters) production which may affect egg quality and ultimately
reproduction. Analytical methods have been developed for detecting these
lipids and micro extraction techniques have been developed (recovery
efficiencies ranging from 68-115%); 2) Development of methods for
detecting and measuring the juvenile crustacean hormone, methyl
fornesoate (which may the crustacean equivalent for estrogen) are
underway and involve collaborations with researchers at SUNY Stoneybrook
and the University of Arizona. Both GC Mass Spectrometry(MS) and
API/MS-MS methods are being analyzed and compared. There is not universal
agreement that methyl fornesoate acts like its insect counterpart
Juvenile Hormone, even though they are structurally equivalent except for
an epoxide bond. If methyl fornesoate is found to indeed be the juvenile
hormone analog in crustaceans, a pathway for potential endocrine effects
may be discerned for endosulfan as well as other contaminants; 3)
Development of methods for measuring vitellin, a protein which is used to
measure the health of an organism. Vitellogenesis is a hormonally
controlled process which causes vitellin to be produced and stored in the
yolk of eggs. Environmental conditions which disrupt this process may
ultimately affect reproduction. Methods development is underway and
should be completed soon.; 4) Aqueous and sediment laboratory toxicity
test with grass shrimp and copepods have been conducted. The acute
aqueous 96h LC50 values for grass shrimp and copepods are quite similar
(0.95 versus 0.46 ug/L). Preliminary (range finding )sediment bioassays
have been conducted and are to be expanded to include multi generational
toxicity testing with copepods during the fall of 1996.
Laboratory
toxicity testing of mosquito fish (Gambusia affinis) for pesticide
resistance have been conducted. Many cyclodiene insecticides, such as
endosulfan, cause resistance which results in fish being able to survive
much higher pesticide levels (>100X) of exposure. This may have
significant environmental consequences in that fish may bioconcentrate
much higher pesticide levels which may be then passed up the food chain.
The source of the this resistance is a thought to be a point mutation on
the GABA A receptor which allow for bioconcentration of cyclodiene
insecticides without accompanying toxicity normally observed. To
determine if mosquito fish in South Florida waters may have in breed
resistance, mosquito fish were collected from the C111 canal and compared
to fish collected from a pristine reference site in South Carolina in
terms of their tolerance of acute endosulfan exposure. Preliminary
results have not suggested the presence of resistance in fish from the
C111 canal based upon their acute toxicity responses to endosulfan
exposures. The next phase of the research will involve assessment of
endosulfan bioconcentration in fish from each area (C111 Canal and a
pristine reference site), since acute toxicity per se may not a sensitive
indicator of resistance. Concurrent molecular studies are also being
conducted and/or planned to assay the potential for GABA A receptor
mutations in mosquito fish from different sites including areas of the
Mississippi Delta where the original cyclodiene pesticide resistance was
measured more than 25 years ago.
11) "Initial assessments of
mercury in Florida Bay biota and development of models of mercury
accumulation in target species"
The
Science Plan for Florida Bay (1994) identified mercury as a contaminant
of major concern. It was felt that Florida Bay, like the adjacent
Everglades, might contain high levels of mercury in resident biota.
Moreover, proposals for augmented freshwater flows to the Everglades
might export mercury into Florida Bay. Both human and wildlife consumers
of fish from Florida Bay may be at risk from mercury. These risks will
depend on three general factors:
D. Evans and D. Engle
We proposed to answer the following four questions:
Initial work has targeted mercury analysis in forage fish (bay anchovies and silver jennies) that are the main prey of some the intermediate and top predators. It is hypothesized that if Everglades' freshwater runoff is an important source of methyl mercury to Florida Bay, then fish captured from areas nearest the Taylor Slough and Canal 111 inputs would contain the highest concentrations of methyl mercury.
Field and Lab Work: Initial field sampling targeted food web organisms from eastern Florida Bay, the area of greatest concern for mercury enrichment. Samples were collected by 3.4 m otter trawl during five minute tows, sorted on deck, placed in ziplock bags, iced until returned to the laboratory where they were frozen until analysis. Water temperature and salinity and position (GPS) were measured at time of sampling. Total mercury analysis in tissues was performed by cold vapor atomic absorption on individual fish rather than composites with QC results that were within the criteria recommended in EPA, 1995).. Bay anchovies (Anchoa mitchelli) were analyzed whole while silver jennies (Eucinostomus gula) were homogenized and subsampled.
Results: Mercury concentrations in bay anchovies from eastern Florida Bay were surprisingly high. Mean concentrations ranged from 0.055 µg Hg/g wet weight at the Crab Keys site, most distant from the Everglades to 0.271 µg Hg/g at the Eagle Key site near Little Madeira Bay. These concentrations are of the same magnitude (0.177 to 0.422 µg Hg/g wet weight) as bay anchovies collected from a mercury contaminated Superfund site at Lavaca Bay, Texas. They are higher than concentrations found in a similar sized forage fish, Gambusia sp., from within the Everglades drainage (Water Control Areas) where highest mercury concentrations are also found in largemouth bass and wading birds (Stober et al., 1995). This suggests that predators on anchovies in eastern Florida Bay could bioaccumulate concentrations of mercury high enough to be of concern.
If we assume an approximate biomagnification factor for methyl mercury of about four between prey and predator fish (current modeling effort), intermediate carnivores such as spotted seatrout feeding on anchovies would be predicted to contain between 0.22 and 1.08 µg Hg/g wet weight. This is similar to the range 0.38 to 1.70 µg Hg/g wet weight reported for spotted seatrout in eastern Florida Bay (Strom and Graves, 1995).
Existence of lower Hg concentrations in anchovies at the site most distant from the Everglades suggests a possible spatial gradient which will require further sampling for confirmation.
Silver Jennies (mojarra) from only four sites have been analyzed for mercury, as yet. The three sites nearest the Everglades have marginally higher mean Hg concentrations (0.110, 0.120, 0.123 µg Hg/g) than the more distant site (0.092 µg Hg/g). Analysis of existing samples and others scheduled for collection should allow us to determine if mercury concentrations in mojarra and in rainwater killifish (the other dominant forage fish) are as high as in bay anchovies. If not, then the reported shift over the past dozen years to anchovies as the dominant forage fish in Florida Bay (Hoss et al., 1996) could translate to an increase in mercury concentrations in fish such as spotted seatrout which feed preferentially on anchovies. Thus, the recent reports of elevated mercury concentrations in certain recreational sized fish in eastern Florida Bay could be follow from ecological shifts in the food web of Florida Bay, independent of any possible historical changes in mercury inputs
Ongoing Work: Collection of intermediate carnivorous fish (spotted seatrout, gray snapper, and red drum) for mercury analysis is being done through a cooperative arrangement with Robert Brock of the National Park Service. These angler-caught fish will also be analyzed for growth and reproductive condition as indicators of changing environmental condition in Florida Bay (Elledge and Brock, 1995). Growth data will be of direct use in modeling the mercury bioaccumulation in these fish which requires bioenergetic estimates of growth and feeding for calibration.
Additional intermediate carnivore fish are being collected as part of the Fisheries-Independent Monitoring program of the Florida Department of Environmental Protection in Florida Bay (Colvocoresses and McMichael, 1995). Duplicate fillet samples from the same fish will be analyzed for mercury by the two groups as a quality assurance measure. We will also analyze smaller individuals of the three carnivore species as part of bioaccumulation modeling. We expect to acquire, for mercury analysis, additional samples of the forage fish from this program whose array of 31 stations covers most of Florida Bay, including stations from each of the targeted sampling zones.
Mercury analyses of other teleost and invertebrate food web organisms from eastern Florida Bay are underway. This data will provide possible corroborating evidence of spatial gradients of mercury in the Bay, provide inputs to mercury bioaccumulation modeling useful in prediction, and perhaps allow us to infer the relative importance of benthic and pelagic environments as proximate sources of mercury to higher trophic level biota.
Colvocoresses, J.A. and R. H. McMichael Jr. 1995. Marine fisheries-independent monitoring program. Abstract presented at Florida Bay Science Conference: A report by principal investigators. Gainesville FL October 17-18, 1995. pp.203-206.
The NOAA Florida Bay Program has also
funded essential non-research items:
12) "Data Management
and Administration"
M. Crane
The NOAA research program in Florida Bay has a significant data gathering mission plus an agreement with the other agencies to share that information. There are three major areas of data administration to report.