Geology topics

Joan A. Browder

Publications and source records attributed to Joan A. Browder.

5 recordsLinked to original sources

USGS2010

Nearshore concentration of pink shrimp (Farfantepenaeus duorarum) postlarvae in northern Florida bay in relation to nocturnal flood tide

We address the question of whether the low abundance of juvenile pink shrimp Farfantepenaeus duorarum (Burkenroad, 1939) in northern-central Florida Bay results from (i) limiting environmental conditions, (ii) a reduced postlarval transport, or (iii) both. To explore this question, postlarvae were collected during the new moon in both summer and fall of 2004 and 2005 at six stations located on a transect from the bay's western margin to its interior. The highest concentrations of postlarvae occurred at two mid-transect stations located in shallow channels with moderate tidal amplitudes (15-20 cm) and dense seagrass beds. At the two interiormost stations postlarval concentrations decreased together with a reduction of the tidal amplitude (= 1 cm). Estimates of the cumulative flood-tide displacement with the semidiurnal M 2 constituent indicated that the tide moves a maximum of 15 km in four nights, a distance that corresponds to the location of the highest concentrations of postlarvae. The size of postlarvae also reached a maximum at the location of the highest concentrations of postlarvae. Results suggest that postlarvae move into the bay's interior by a cumulative flood tidal process, advancing onshore during successive nights as far as they can go with the tide. Analyses indicate that, in addition to the tidal amplitude, cross-shelf wind stress and salinity also affect the concentrations of postlarvae. Peaks of postlarvae occurred at times of low salinity and strong southeasterly winds. While tidal transport appears to be insufficient for postlarvae to reach Florida Bay's interior, salinity and winds may also contribute to the observed distribution patterns of early pink shrimp recruits. ?? 2010 Rosenstiel School of Marine and Atmospheric Science of the University of Miami.

Bulletin of Marine Science↗

USGS2007

Cross-shelf transport of pink shrimp larvae: Interactions of tidal currents, larval vertical migrations and internal tides

Transport and behavior of pink shrimp Farfantepenaeu s duorarum larvae were investigated on the southwestern Florida (SWF) shelf of the Gulf of Mexico between the Dry Tortugas spawning grounds and Florida Bay nursery grounds. Stratified plankton samples and hydrographic data were collected at 2 h intervals at 3 stations located on a cross-shelf transect. At the Marquesas station, midway between Dry Tortugas and Florida Bay, internal tides were recognized by anomalously cool water, a shallow thermocline with strong density gradients, strong current shear, and a high concentration of pink shrimp larvae at the shallow thermocline. Low Richardson numbers occurred at the pycnocline depth, indicating vertical shear instability and possible turbulent transport from the lower to the upper layer where myses and postlarvae were concentrated. Analysis of vertically stratified plankton suggested that larvae perform vertical migrations and the specific behavior changes ontogenetically; protozoeae were found deeper than myses, and myses deeper than postlarvae. Relative concentrations of protozoea in the upper, middle and bottom layers were consistent with a diel vertical migration, whereas that of postlarvae and myses were consistent with the semidiurnal tides in phase with the flood tide. Postlarvae, the shallowest dwellers that migrate with a semidiurnal periodicity, experienced the largest net onshore flux and larval concentrations were highly correlated with the cross-shelf current. These results provide the first evidence of an onshore tidal transport (a type of selective tidal stream transport, STST), in decapod larvae migrating in continental shelf waters offshore, ca. 100 km from the coast and at a depth of 20 m, while approaching the coastal nursery grounds. Longer time series would be necessary to establish whether internal tides play any role in the larval onshore transport of this species and determine if the STST is the dominant onshore transport mechanism.

Florida↗

USGS2006

Variability in supply and cross-shelf transport of pink shrimp ( Farfantepenaeus duorarum ) postlarvae into western Florida Bay

The variability in the supply of pink shrimp ( Farfantepenaeus duorarum ) postlarvae and the transport mechanisms of planktonic stages were investigated with field data and simulations of transport. Postlarvae entering the nursery grounds of Florida Bay were collected for three consecutive years at channels that connect the Bay with the Gulf of Mexico, and in channels of the Middle Florida Keys that connect the southeastern margin of the Bay with the Atlantic Ocean. The influx of postlarvae in the Middle Florida Keys was low in magnitude and varied seasonally and among years. In contrast, the greater postlarval influx occurred at the northwestern border of the Bay, where there was a strong seasonal pattern with peaks in influx from July through September each year. Planktonic stages need to travel up to 150 km eastward between spawning grounds (northeast of Dry Tortugas) and nursery grounds (western Florida Bay) in about 30 days, the estimated time of planktonic development for this species. A Lagrangian trajectory model was developed to estimate the drift of planktonic stages across the SW Florida shelf. The model simulated the maximal distance traveled by planktonic stages under various assumptions of behavior. Simulation results indicated that larvae traveling with the instantaneous current and exhibiting a diel behavior travel up to 65 km and 75% of the larvae travel only 30 km. However, the eastward distance traveled increased substantially when a larval response to tides was added to the behavioral variable (distance increased to 200 km and 85% of larvae traveled 150 km). The question is, when during larval development, and where on the shallow SW Florida shelf, does the tidal response become incorporated into the behavior of pink shrimp.

Florida↗

USGS2005

Tidal and seasonal effects on transport of pink shrimp postlarvae

Transport simulations were conducted to investigate a large seasonal peak in postlarvae of the pink shrimp Farfantepenaeus duorarum that occurs every summer on the northwestern border of Florida Bay. Daily vertical migration, a known behavior in pink shrimp postlarvae, was assumed in all scenarios investigated. A Lagrangian trajectory model was developed using a current field derived from a 3 yr ADCP (Acoustic Doppler Current Profiler) time series. To fit the estimated planktonic development time of pink shrimp, the model simulated larvae traveling at night over a 30 d period. We investigated 2 types of effects: (1) the effect of mismatch periodicity between tidal constituents and daily migration, and (2) the effect of seasonal changes in night length. The maximum eastward displacement with the semidiurnal lunar tidal constituent (M2) was 4 km, with periods of enhanced transport in both summer and winter. In contrast, eastward displacement with the semidiurnal solar tidal constituent (S2) and the lunisolar diurnal K1 was 65 km and the period of maximum distance occurred in summer every year. Because the periods of S2 and K1 are so close to the 24 h vertical migration period, and the eastward current (flood) of these constituents matches the diel cycle over extended intervals, they can induce strong horizontal transport during summer. Thus, diel vertical migration can interact with the S2 and the K1 tidal constituents and with the annual cycle of night length to produce a distinct annual cycle that may enhance transport of pink shrimp and other coastal species during summer in shallow areas of the Gulf of Mexico. ?? Inter-Research 2005.

Marine Ecology Progress Series↗

USGS1999

Environmental influences on potential recruitment of pink shrimp, Fatlantopenaeus duorarum , from Florida Bay nursery grounds

Two modeling approaches were used to explore the basis for variation in recruitment of pink shrimp, Farfantepenaeus duorarum, to the Tortugas fishing grounds. Emphasis was on development and juvenile densities on the nursery grounds. An exploratory simulation modeling exercise demonstrated large year-to-year variations in recruitment contributions to the Tortugas rink shrimp fishery may occur on some nursery grounds, and production may differ considerably among nursery grounds within the same year, simply on the basis of differences in temperature and salinity. We used a growth and survival model to simulate cumulative harvests from a July-centered cohort of early-settlement-stage postlarvae from two parts of Florida Bay (western Florida Bay and northcentral Florida Bay), using historic temperature and salinity data from these areas. Very large year-to-year differences in simulated cumulative harvests were found for recruits from Whipray Basin. Year-to-year differences in simulated harvests of recruits from Johnson Key Basin were much smaller. In a complementary activity, generalized linear and additive models and intermittent, historic density records were used to develop an uninterrupted multi-year time series of monthly density estimates for juvenile rink shrimp in the Johnson Key Basin. The developed data series was based on relationships of density with environmental variables. The strongest relationship was with sea-surface temperature. Three other environmental variables (rainfall, water level at Everglades National Park Well P35, and mean wind speed) also contributed significantly to explaining variation in juvenile densities. Results of the simulation model and two of the three statistical models yielded similar interannual patterns for Johnson Key Basin. While it is not possible to say that one result validates the other, the concordance of the annual patterns from the two models is supportive of both approaches.

Estuaries↗