Grantee Research Project Results
2001 Progress Report: Physical Oceanographic Studies
EPA Grant Number: R828020C004Subproject: this is subproject number 004 , established and managed by the Center Director under grant R828020
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Children's Environmental Health and Disease Prevention Center - Dartmouth College
Center Director: Karagas, Margaret Rita
Title: Physical Oceanographic Studies
Investigators: Lee, Thomas N.
Institution: University of Miami
EPA Project Officer: Packard, Benjamin H
Project Period: December 15, 1999 through December 14, 2003
Project Period Covered by this Report: December 15, 2000 through December 14, 2001
RFA: National Center for Caribbean Coral Reef Research (1999) RFA Text | Recipients Lists
Research Category: Congressionally Mandated Center , Targeted Research
Objective:
The goal of the physical oceanography component of the NCORE study is to quantify the upwelling nutrient flux to the Florida Keys coral reefs and to understand the controlling physical processes. The specific objectives are: 1) To determine the spatial and temporal variability of the near-bottom flux of nutrients from the Florida Current and to quantify the rates and pathways of nutrient inputs to coral reef communities. 2) To identify and describe the primary physical processes regulating this nutrient flux. 3) To provide input to the nutrient budget. 4) To quantify the temporal and spatial characteristics of water movements and temperature and salinity variability in Pennekamp Park.Progress Summary:
Recent hydrographic surveys, moored current measurements and drifter trajactories show a high degree of connectivity between the different subregions of south Florida coastal waters and with remote upstream areas of the Gulf of Mexico. The southwest Florida shelf and the Keys Atlantic coastal zone respond differently to wind forcing that is coherent over both areas due to different coastline configurations and topographic constraints. The connection between the two shelf regimes is provided by the transports through the Keys passages. Measurements show that subtidal transport variations of + 1000 to -2500 m3/s (negative is toward the reef tract) are due to local wind forced cross-Key sea level slopes. In addition, a mean southeastward transport of about -700 m3/s is estimated for the middle Keys that opposes the prevailing winds and appears to be related to the flow on the southwest Florida shelf, suggesting a Loop Current influence. Drifter trajectories show that there are three common pathways connecting the entire south Florida coastal system that follow the seasonal changes in wind patterns: southeastward through the passages of the middle Keys, (winter/spring); southwest to the Tortugas (fall); and northwest with eventual entrainment by the Loop Current, followed by transport to the Tortugas (summer/fall). Advective time scales to reach the Keys coastal zone range from 1 to 6 months, that can be followed by 1 to 3 months retention in coastal eddies and countercurrents.
Field work began in June 2000 with the deployment of a 7-mooring current and temperature array across the shelf in the northern Keys off Key Largo as per the following table:
Mooring # | Lat (deg) | Lat (min) | Long (deg) | Long (min) | Depth (m) | Type |
Mooring A | 25 | 6.539 | 80 | 22.823 | 4.1 | Current/temp |
Mooring B | 25 | 5.587 | 80 | 21.296 | 7.01 | Current/temp |
Mooring C | 25 | 4.044 | 80 | 19.073 | 26.8 | Current/temp |
Temp #1 | 25 | 4.139 | 80 | 19.167 | 9.7 | Bottom temp |
Temp #2 | 25 | 4.43 | 80 | 19.473 | 7.0 | Bottom temp |
Temp #3 | 25 | 4.77 | 80 | 20.061 | 4.0 | Bottom temp |
Temp #4 | 25 | 5.271 | 80 | 20.829 | 5.6 | Bottom temp |
Location of the mooring stations and hydrographic stations are shown in Figure 1 below.
This array was recovered and redeployed in November 2000 and will be maintained for a 1.5 year period. Data quality and quantity from this first deployment are excellent. Data processing and analysis are underway.
All time series data are processed to produce raw edited time series, 3 hour
low-passed filtered and 40-hour low-passed filtered time series. Current data
are converted to alongshelf (v) and cross-shelf (u) components. Statistical
analyses are conducted with each parameter of the time series to determine the
means, standard deviations, standard error of the mean, percent variance due to
tides and to subtidal motions. In addition Spectra, cross-coherence and
cross-phase analysis are conducted with all current and temperature pairs of
time series, including spectral analyses of local winds with currents.
Temperature data will be regressed together with nutrient data to look for
meaningful relationships that can be used to convert temperature time series to
nutrient time series that can be used together with current data to determine
nutrient flux.
Examples of temperature and current time series from the deep outer reef station (24 m isobath) are shown in Figure 2. Large amplitude temperature variations were observed near bottom over several periods during the first 6-months of records that are visually correlated to onshore flow events. These shoreward pulses of cold water are believed to be high in nutrient concentration and represent a pulsed delivery of nutrients to the fringing reefs from the Florida Current nutracline. These data will be used to estimate onshore nutrient flux.
Spatial patterns and seasonal variability of temperature, salinity and
nutrient distributions in the Florida Keys National Marine Scantuary and
surrounding regions are determined on bi-monthly, multidisciplinary research
cruises. Five such cruises have been conducted to date. This effort will also be
continued for a 1.5 year period. Hydrographic station locations occupied on
these bi-monthly cruises are given in the following table:
Table 2. Location of NCORE CTD stations.
Station | Lat (deg) | Lat (min) | Long (deg) | Long (min) | Depth (m) | Transect |
E1 | 25 | 10.7 | 80 | 20.1 | 2.5 | Elbow Reef |
E2 | 25 | 9.7 | 80 | 18.32 | 4.5 | Elbow Reef |
E3 | 25 | 8.88 | 80 | 17.0 | 6.6 | Elbow Reef |
E4 | 25 | 8.1 | 80 | 15.5 | 31.1 | Elbow Reef |
4.0 | 25 | 6.5 | 80 | 22.8 | 3.0 | Dixie Shoal |
5.0 | 25 | 5.6 | 80 | 21.3 | 6.0 | Dixie Shoal |
5.5 | 25 | 4.78 | 80 | 20.05 | 3.8 | Dixie Shoal |
6.0 | 25 | 3.9 | 80 | 18.9 | 31.0 | Dixie Shoal |
6.5 | 25 | 2.9 | 80 | 17.26 | 72.0 | Dixie Shoal |
P1 | 25 | 0.6 | 80 | 28.6 | 3.0 | Pickles Reef |
P2 | 25 | 59.85 | 80 | 27.78 | 4.5 | Pickles Reef |
P3 | 25 | 58.9 | 80 | 26.7 | 6.0 | Pickles Reef |
P4 | 25 | 58.0 | 80 | 25.68 | 35.0 | Pickles Reef |
Figure 1. Locations of NCORE moored instrumentation for the measurement of currents and water temperature. The open circles indicate the standard CTD stations for the bimonthly hydrographic cruises. The gray shadowed circles and the black circle show the location of long-term current measurements. The stars show the relative positions of the temperature sensor array.
All instruments are calibrated before or after use to maintain high levels of accuracy. Instrumentation preparation, deployment and recovery are following our standard methods as discussed in the Q/A Report. Data analysis is also on target and following prescribed methodology.
Results to date indicate that nutrient flux to the reef tract from the Florida Current is a transient process that takes place in the spring and early summer in a nearbottom layer. Current and temperature time series show high frequency bursts of cold nearbottom intrusions that appear to make a significant contribution to the nutrient flux.
Future Activities:
Planned activity for the subsequent reporting period will be to continue the ongoing field measurements both moored observations and hydrographic survey cruises to better understand the oceanography of the Florida reef tract and its influence on sustaining reef ecosystems.SUMMARY
South Florida coastal ecosystems consist of a collection of distinct marine environments that are strongly connected by their circulation and exchange processes on a regional scale, and by oceanic boundary currents to remote upstream regions of the Gulf of Mexico and Caribbean. The south Florida Coastal waters lie between the eastern Gulf of Mexico and the Atlantic and are thereby strongly impacted by major currents and eddy systems that connect these regions. Large-scale transport by the Loop Current and Florida Current provide a long distance conduit for foreign recruits, especially those with long larval duration periods. The combination of eddies that form along the fronts of these current systems together with wind-driven coastal counter currents along the Florida Keys reef tract and sea surface slope driven flows through the passages between the Keys provides an effective recirculation system to retain locally spawned larvae on time scales of weeks to several months. Longer retention times are available for recruitment pathways linking south coastal Florida waters with the west Florida shelf that provide a potential recruitment link for locally spawned Florida lobster larvae. The combination of Florida Current meanders and eddies in the southern Straits of Florida, together with northward wind driven Ekman transports establishes a potential pathway for larvae spawned along the north coast of Cuba to recruit to south Florida coastal ecosystems on time scales of one to three weeks. Seasonal cycles of local winds and Florida Current transport favor the fall season for retention of local larvae, as well as recruitment of larvae from Cuban coastal waters.
Circulation and Exchange Processes Linking South Florida Coastal Waters
Thomas N. Lee1, Elizabeth Johns2, Ned Smith3, Doug Wilson2, Elizabeth Williams1 and Ryan Smith2
Recent hydrographic surveys, moored current measurements and drifter trajactories show a high degree of connectivity between the different subregions of south Florida coastal waters and with remote upstream areas of the Gulf of Mexico. The southwest Florida shelf and the Keys Atlantic coastal zone respond differently to wind forcing that is coherent over both areas due to different coastline configurations and topographic constraints. The connection between the two shelf regimes is provided by the transports through the Keys passages. Measurements show that subtidal transport variations of + 1000 to -2500 m3/s (negative is toward the reef tract) are due to local wind forced cross-Key sea level slopes. In addition, a mean southeastward transport of about -700 m3/s is estimated for the middle Keys that opposes the prevailing winds and appears to be related to the flow on the southwest Florida shelf, suggesting a Loop Current influence. Drifter trajectories show that there are three common pathways connecting the entire south Florida coastal system that follow the seasonal changes in wind patterns: southeastward through the passages of the middle Keys, (winter/spring); southwest to the Tortugas (fall); and northwest with eventual entrainment by the Loop Current, followed by transport to the Tortugas (summer/fall). Advective time scales to reach the Keys coastal zone range from 1 to 6 months, that can be followed by 1 to 3 months retention in coastal eddies and countercurrents.
1University of Miami-RSMAS, Miami, Fl;
2NOAA/AOML, Miami, Fl;
3Harbor
Branch Oceanographic Laboratory, Ft. Pierce, Fl.
Thomas, Lee, University of Miami-RSMAS, 4600 Rickenbacker Causeway, Miami, Fl, 33149, Phone: 305-361-4046, tlee@rsmas.miami.edu.
Journal Articles:
No journal articles submitted with this report: View all 3 publications for this subprojectSupplemental Keywords:
Coral Reefs, Estuarine Research, coastal ecosystem, aquatic ecosystem, watersheds, nutrient flux, Florida Keys, hydrogeographic survey, marine environment., RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, estuarine research, Water & Watershed, Aquatic Ecosystems & Estuarine Research, Nutrients, State, Aquatic Ecosystem, algal blooms, Environmental Monitoring, Ecological Risk Assessment, Ecology and Ecosystems, Watersheds, marine ecosystem, wetlands, coastal ecosystem, hydrological stability, nutrient supply, nutrient transport, bloom dynamics, coastal resources, coral reefs, estuaries, coastal watershed, estuarine integrity, nutrient concentrations, marine biology, watershed sustainablity, nutrient flux, Florida Keys, esturarine eutrophication, coastal environments, algal growth, nutrient stress, environmental indicators, coastal ecosystems, aquatic ecosystems, coral reef ecosystem integrity, watershed sustainablility, environmental stress, nutrient cycling, water quality, Florida, ecological indicators, coral reef communities, watershed assessment, ecosystem stress, ecological research, watershed restoration, ecosystem responseProgress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R828020 Children's Environmental Health and Disease Prevention Center - Dartmouth College Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R828020C002 Nutrient Cycling and Algal Productivity in the Florida Keys
R828020C003 Top-Down Trophodynamics
R828020C004 Physical Oceanographic Studies
R828020C005 Impacts of Nutrients on Reefs in the Florida Keys
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
Main Center: R828020
9 publications for this center
2 journal articles for this center