Florida Estuary Research Articles

Origin and transport of sedimentary organic matter in two subtropical estuaries: a comparative, biomarker-based study

Two sub-tropical estuaries of south Florida, USA, were studied to determine the origin and transport of organic matter between the freshwater and marine end-members of these systems. Sediments, as well as main biomass components (vegetation) were analyzed for lipid composition and content. The molecular distribution of several biomarker compounds, organism-specific biomarkers and bulk sediment characteristics such as %OM, C/N and δ13C were used to assess differences in OM source and transport between a strongly tidally-influenced estuary (Harney River) and one that is only seasonally influenced by estuarine waters (Taylor River). The data show mixing of combined terrestrial and autochthonous freshwater-derived OM, with marine planktonic and seagrass-derived OM in the middle to lower estuary of the Harney River. In contrast, such mixing did not occur to a measurable degree at the Taylor River, where low water discharge and exchange does not allow for any significant mixing of OM from end-member sources. Differences in hydrological conditions and benthic plant biomass and productivity between the two systems results in different OM inputs, which are reflected in the quality and degree of diagenesis of the sedimentary OM. Specific applications and potential limitations of traditional biomarker compounds for OM source assessment are discussed.

Abundance, Spatial Distribution, and Mortality of Young-of-the-Year Spotted Seatrout (Cynoscion nebulosus) Along the Gulf Coast of Florida

We used fixed-station and random-station sampling data from the period 1989-97 to examine spatial and temporal patterns in the abundance and size structure of young-of-the-year (YOY) spotted seatrout, Cynoscion nebulosus, in three Florida estuaries. YOY seatrout first appeared at shallow-water (<1.5 m) seine sites in May-June in Choctawhatchee Bay (Florida Panhandle) and in April-May in Tampa Bay and Charlotte Harbor (both along the southwest Florida peninsula). Spotted seatrout were caught at deepwater (> 1.6 m) trawl stations within 1-3 mo of their initial appearance at shallow-water sites. Most spotted seatrout were caught in waters <3.7 m. Spring and summer peal's in YOY abundance, corresponding to strong influxes of newly spawned individuals, were observed only in southwest peninsula estuaries. Depending on the estuary, the occurrence of YOY spotted seatrout at shallow-water sites was associated with some combination of seagrasses, mangroves, salinity, depth, temperature, and mud. Estimates of total instantaneous mortality rates for YOY spotted seatrout in Tampa Bay were 0.027·d-1 for fixed sites and to 0.025·d-1 for randomly selected sites.

Origin and transport of n-alkane-2-ones in a subtropical estuary: potential biomarkers for seagrass-derived organic matter

n-Alkane-2-ones are lipids commonly found in sediments and soils. This group of compounds, frequently reported in the literature, usually occurs in the form of a homologous series ranging from about C19 to C33 characterized by a strong odd over even carbon number predominance. In this paper we report a different molecular distribution, centered about the C25 homologue as the dominant ketone. The relative abundance of the C25 compared to the C27 homologue in a sediment transect increased from the upper to the lower end of a South Florida estuary, and was found to correlate with surface water salinity in extracts from suspended solids. Analyses of different varieties of seagrasses showed these to be the most likely source of the C25n-alkane-2-ones, while the C27+ homologues were mainly derived from mangroves and freshwater marsh vegetation. Compound-specific stable isotope measurements and statistical analyses support this finding, suggesting that molecular distributions of n-alkane-2-ones can be used to identify seagrass-derived organic matter in coastal environments.

Intralocality Variation in Feeding Biomechanics and Prey Use in Archosargus probatocephalus (Teleostei, Sparidae), with Implications for the Ecomorphology of Fishes

Archosargus probatocephalusin a Florida estuary was investigated to explore intraspecific variation in prey utilization and jaw biomechanics. Volumetric contribution of major prey types and seven biomechanical features of the oral jaws that characterize prey-capture and processing performance were contrasted between two locations within the estuary. At Mosquito Lagoon, where A. probatocephalusinhabited mostly oyster beds, mangroves and salt marshes, fish consumed mostly thick-shelled bivalves, gastropods, crabs, and tubiculous polychaetes and amphipods. In contrast, conspecifics at Indian River Lagoon that inhabited mostly seagrass beds and algal turf consumed predominantly algae, seagrass, epiphytic invertebrates and small bivalves and gastropods. Difference in magnitude of durophagy between locations was associated with differences in oral-jaw biomechanics. Analyses of covariance indicated that A. probatocephalusat Mosquito Lagoon had more massive jaw muscles and bones, than conspecifics at Indian River Lagoon. Variations in lever ratios for jaw-opening and jaw-closing between locations were not significant. It is hypothesized that intralocality differences in food habits have induced the development of feeding morphologies that enhance the ability of A. probatocephalusto successfully exploit locally dominant prey resources within the estuary. Plasticity of the feeding mechanism of A. probatocephalusmay buffer the species from the adverse effects of settling on heterogeneous habitats that contain variable prey resources such as those found within estuaries.

δ15N Studies of Nitrogen Use by the Red Mangrove, Rhizophora mangle L. in South Florida

To help define nitrogen (N) sources and patterns of N processing in mangrove ecosystems, mangrove leaf nitrogen contents and δ15N values were assayed in three marshes along the south Florida coast. In each marsh, leaf samples were collected from dwarf mangroves at interior locations and taller mangroves at the ocean fringe. Leaf %N and δ15N values did not differ consistently between dwarf and tall mangroves, even though there were large variations in δ15N (18‰ range, −5 to +13‰) and %N (1·2% range, 0·9–2·1%). Highest %N and δ15N values occurred along the western margin of Biscayne Bay where canals draining agricultural lands deliver high-nitrate waters to fringing mangrove marshes. High mangrove δ15N values may be good biomonitors of anthropogenic N loading to south Florida estuaries. Lower values likely reflect less anthropogenic N entering the mangrove marshes, as well as differences in plant physiology that occur along the fringe-dwarf gradient.

FORUM: Hypothesis-Driven Experimental Research Is Necessary for Natural Resource Management.

/ Effective management of natural resources must be grounded in a solid scientific understanding of the ecosystem and its responses to natural and human-induced stress. Such an understanding does not arise easily from observational data and models that are not substantiated by experimental data. Cause-and-effect relationships are more easily documented when observations and/or models are supplemented by hypothesis-driven experimental research. In this paper we present three examples from south Florida where hypothesis-driven experimental research has been combined with observational data collection to address specific resource management questions. These include research to determine: (1) the cause of cattail expansion in the Everglades; (2) a threshold phosphorus concentration for the Everglades; and (3) optimal salinity criteria for Florida estuaries. In each case, the results have led to a better understanding of ecosystem function and more sound guidance for resource managers than was possible without the hypothesis-drive experimental research. Resource managers need to recognize the merits of this holistic approach to environmental science and management if we are to have success in reversing detrimental human impacts on natural ecosystems.

Distribution of total mercury and methyl mercury in water, sediment, and fish from south Florida estuaries.

Concentrations of total mercury and methyl mercury were determined in sediment and fish collected from estuarine waters of Florida to understand their distribution and partitioning. Total mercury concentrations in sediments ranged from 1 to 219 ng/g dry wt. Methyl mercury accounted for, on average, 0.77% of total mercury in sediment. Methyl mercury concentrations were not correlated with total mercury or organic carbon content in sediments. The concentrations of total mercury in fish muscle were between 0.03 and 2.22 (mean: 0.31) micrograms/g, wet wt, with methyl mercury contributing 83% of total mercury. Methyl mercury concentrations in fish muscle were directly proportional to total mercury concentrations. The relationship of total and methyl mercury concentrations in fish to those of sediments from corresponding locations was fish-species dependent, in addition to several abiotic factors. Among fish species analyzed, hardhead catfish, gafftopsail catfish, and sand seatrout contained the highest concentrations of mercury. Filtered water samples from canals and creeks that discharge into the Florida Bay showed mercury concentrations of 3-7.4 ng/L, with methyl mercury accounting for < 0.03-52% of the total mercury. Consumption of fish containing 0.31 microgram mercury/g wet wt, the mean concentration found in this study, at rates greater than 70 g/day, was estimated to be hazardous to human health.

The culture of the southern bay scallop in Tampa Bay, an urban Florida estuary

Bay scallop, Argopecten irradians concentricus (Say), stocks were collected from a Homosassa (Florida) population in 1991 and were kept in seawater from Bayboro Harbor on Tampa Bay, an urban Florida estuary. They were fed with Isochrysis galbana and Tetraselmis sp. Spawning was allowed to occur after the scallops became ripe. The hatching rate of the F1 eggs to D-shaped larvae was 72%. Settlement and metamorphosis began 11 days after fertilization. When spat reached a shell height of 0.8 mm in the laboratory, they were placed with substrates into 300 and 800 μm mesh bags, and later in lantern nets, suspended from a dock in Bayboro Harbor. The F1 scallops successfully survived to gonad maturity in the fall of 1992, with mean (sd) shell height of 49.8 (4.0) mm on 6 September 1992. The scallops experienced heavy mortality during the summer, partially as a result of heavy fouling. From early August to October of 1992, F1 scallops grown in Bayboro Harbor were successfully spawned in the laboratory. Growth and survival of the F2 scallops were comparable to those of the F1 scallops. Results have shown that bay scallops can complete an entire life cycle in an urban estuary such as Tampa Bay, and a hatchery for bay scallops on the estuary can assist in the restoration of the population. Fouling represents a possible severe limitation and alternatives to caging for grow-out should be considered.

Consequences of protist-stimulated bacterial production for estimating protist growth efficiencies

The trophic link between bacteria and bacterivorous protists is a complex interaction that involves feedback of inorganic nutrients and growth substrates that are immeadiately available for prey growth. These interactions were examined in the laboratory and in incubations of concentrated natural assemblages of bacterioplankton. Growth dynamics of estuarine and marine bacterivorous protists were determined in laboratory culture using Vibrio natriegens as prey and were compared to growth of protists on bacterioplankton assemblages concentrated by tangential flow filtration from four northwest Florida Estuaries. Biomass transfers from bacteria to protists were monitored by tracing elemental carbon and nitrogen in particulate fractions of protist added and grazer free controls. Gross growth efficiencies of the protists on naturally occurring bacteria were within the range determined in lab estimates of growth efficiency on cultured bacteria (∼50%). However, bacterial response to protist excretion products was different in the lab and field incubations, and bacterial growth contributed to the biomass available to protists in the field incubations. As determined by radioisotope-labeled substrate incorporation, a time lag in bacterial reponse to protist excretion products was observed for laboratory batch cultures, allowing accurate estimation of growth efficiency. In incubations with concentrated natural bacterial assemblages, bacterial growth response coincided with protist growth and excretion. The additional bacterial production on protist excretion products reached a maximum of 2–3-fold higher than protist-free controls. In addition, ammonium concentrations increased with protist grazing and growth in lab cultures, but ammonium excreted by protists in concentrates did not accumulate. The C:N values for the bacterial concentrates suggests that these bacteria were nitrogen limited. It is speculated that dissolved organic carbon, concentrated by tangential flow filtration (> 100,000 MW membrane) with the bacterioplankton, was utilized by bacteria when nitrogen was supplied as ammonium and amino acids from protist excretion. Thus, estimates of protist growth efficiency on naturally occurring bacterioplankton, corrected for protist-stimulated bacterial production, were in the range of 13–21%.

Anthropogenic Sediment Resuspension Mechanisms in a Shallow Microtidal Estuary

The mechanisms that resuspend bottom sediments in Hillsborough Bay, a shallow, microtidal, subtropical estuary in West-central Florida, were determined by analysing hydrodynamic and suspended-solids concentration data collected during several instrument deployments made in 1990 and 1991. Large vessels in a dredged ship channel can generate forced solitary long waves that cause large water velocities and sediment resuspension at the study sites. An experiment was conducted with a trawler that resuspended bottom sediments, and some of the resuspended sediments remained in suspension for at least 8 h. A secondary impact of vessel-generated long waves and trawling is that sediments that are resuspended and newly deposited are more susceptible to resuspension by tidal currents than undisturbed bottom sediments. Natural sediment resuspension by wind waves and tidal current is less frequent or of smaller magnitude than anthropogenic sediment resuspension. The annual mass of sediment resuspended by vessel-generated long waves is estimated to be one order of magnitude greater than the annual mass of sediment resuspended by wind waves generated by winter storms.

Inhibition of bacterial activities by solar radiation in nearshore waters and the Gulf of Mexico

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 11:229-238 (1996) - doi:10.3354/ame011229 Inhibition of bacterial activities by solar radiation in nearshore waters and the Gulf of Mexico Aas P, Lyons MM, Pledger R, Mitchell DL, Jeffrey WH The effects of ultraviolet (UV) radiation on thymidine and leucine incorporation were examined in surface waters from the Gulf of Mexico and Santa Rosa Sound, a mesotrophic estuary in northwest Florida, USA. Whole and 0.8 μm filtered surface waters were incubated with 3H-thymidine and 14C-leucine in UV transparent containers under natural solar radiation. Solar radiation was either not filtered (samples exposed to UV-B, UV-A, and photosynthetically active radiation, PAR), filtered through Mylar 500D (samples exposed to UV-A and PAR), or filtered through Acrylite OP3 (samples exposed only to PAR). In Santa Rosa Sound, thymidine incorporation was inhibited an average of 44% relative to dark controls when exposed to unfiltered solar radiation. PAR contributed 23% to the total thymidine inhibition, while UV-A and UV-B contributed 37% and 39%, respectively, to total inhibition. Leucine incorporation in Santa Rosa Sound was inhibited 29% by full solar radiation. The majority of the total leucine inhibition was due to UV-B (83%), while PAR only treatments showed leucine incorporation rates 10% higher than dark controls. For the Gulf of Mexico experiments, full solar radiation inhibited thymidine incorporation approximately twice as much as leucine incorporation. However, there were no consistent patterns in differences due to different wavelengths. Both thymidine and leucine incorporation were inhibited to a greater extent in <0.8 μm filtered water samples than in whole water samples, suggesting that the presence of primary producers may mediate the detrimental effects of solar radiation on bacterioplankton. Surface water was also incubated in situ with thymidine at fixed depths in UV transparent and darkened containers at 3 locations in the Gulf of Mexico. Total inhibition was 60 to 70% at the surface and was evident to 15 m. Comparison with radiometric data and DNA dosimeters indicated that UV-B exerted the greatest effect in the upper 5 m while below that the inhibition was most likely due to longer wavelengths. Our results suggest that both UV and visible solar radiation can negatively affect bacterial metabolism and failure to take into account the effects of light may result in the overestimation of bacterioplankton production in surface waters. Ultraviolet radiation · Bacteria · Thymidine · Leucine · Gulf of Mexico · Global carbon cycle Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 11, No. 3. Publication date: December 31, 1996 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1996 Inter-Research.

Sediment Resuspension Mechanisms in Old Tampa Bay, Florida

The mechanisms that resuspend bottom sediments in Old Tampa Bay, a shallow, microtidal, subtropical estuary in west-central Florida, were determined by analysing data collected during several periods from 1988 to 1990. Hydrodynamic and suspended-solids concentration data were collected at a relatively deep (4m) site where a permanent platform was built and at a relatively shallow (1·5m) site where a submersible instrument package was deployed. Bottom sediments were non-cohesive silts and fine sands. The primary sediment resuspension mechanism at both sites was wind waves, which were generated by strong and sustained winds associated with winter storms and tropical storms. At the platform, waves were depth-transitional, and estimated bottom shear stresses were most sensitive to wave period and water depth. Concentrations of suspended solids at this site corresponded well with wave motion, and non-linear wave-current interaction was small. At the shallow-water site, concentrations of suspended solids were elevated during periods of strong north-easterly winds and large bottom orbital velocities. At both sites, wind direction was an important factor in determining the occurrence and magnitude of sediment resuspension. Resuspended sediments settled within several hours as storm intensity diminished. Winds and waves generated by thunderstorms were more transient than those generated by winter storms and tropical storms. Based on the data collected during this study, thunderstorms are less likely to resuspend bottom sediment than winter storms and tropical storms. Maximum tidal currents at the study sites are usually less than 15cm s−1and did not increase observed concentrations of suspended solids.

Differences in the Crab Fauna of Mangrove Areas at a Southwest Florida and a Northeast Australia Location: Implications for Leaf Litter Processing

Existing paradigms suggest that mangrove leaf litter is processed primarily via the detrital pathway in forests in the Caribbean biogeographic realm whereas herbivorous crabs are relatively more important litter processors in the Indo-West Pacific. To test this hypothesis, we used pitfall traps to collect intertidal crabs to characterize the crab fauna in a mangrove estuary in southwest Florida. We also tethered mangrove leaves to determine if herbivorous crabs are major leaf consumers there. We compared the results with previously published data collected in an analogous manner from forests in northeastern Australia. The crab fauna in Rookery Bay, Florida, is dominated by carnivorous xanthid and deposit-feeding ocypodid crabs whereas that of the Murray River in northeastern Australia is dominated by herbivorous grapsid crabs. No leaves tethered at five sites in the forests in Southwest Florida were taken by crabs. This contrasts greatly with reported values of leaf removal by crabs in Australian forests of 28–79% of the leaves reaching the forest floor. These differences in the faunal assemblages and in the fate of marked or tethered leaves provide preliminary support for the hypothesis that leaf litter is in fact processed in fundamentally different ways in the two biogeographic realms.

The Historical Record of Metal Enrichment in Two Florida Estuaries

Historical profiles of metal accumulation have been generated for the lower St. Johns River and Hillsborough Bay, Florida, in cores representing approximately 50 yr of sediment and metal accumulation. These profiles demonstrate that Cd, Pb, and Zn are enriched in these Florida estuarine sediments. Pb enrichment has decreased since the mid 1970s because of reduced use of leaded gasoline. In the St. Johns River, most metals exhibit a trend of increasing enrichment with time. Cd enrichment significantly decreased between 1970 and 1975 as a result of reduced discharges into the river and control of aquatic vegetation. In Hillsborough Bay, enrichment factors for most metals are relatively high and show little change downcore. Cr, Cu, and Ni border on enrichment and Pb, Cd, and Zn are enriched. The results of this study are consistent with other studies of surficial-sediment metal concentration in other Florida estuaries.

Atmospheric deposition of nitrate and its transport to the Apalachicola Bay estuary in Florida

A comparison of fluxes of ten dissolved constituents of rain water and river water has been carried out for the watershed of the Apalachicola River in order to estimate the magnitude of nitrate contribution from the atmosphere to surface water that may flow to the Apalachicola Bay estuary. The comparison is based on statistical analysis of both atmospheric and fiver water monitoring data: weekly rain water chemical data from the National Acid Deposition Program (NADP) for five sites within the watershed area, from 1978–84 until late 1989, and less frequent river water chemical data from the U.S. Geological Survey for one site ai Chattahoochee, Florida, from 1965 until late 1989. The means and standard errors of the fluxes from the atmosphere and in the river flow were determined. As a measure of correlations between different ionic concentrations in the rain and river water data sets, factor analysis was used to account for data variance by a sum of principal components according to a linear mixing model. By comparing the compositions and magnitudes of these components, judgments could be made concerning the importance of atmospheric deposition as a source of nitrate in the watershed as well as of chemical transformations and possible loss of nitrate during its residence in the watershed and transport to the estuary. Although surface sources of N and extent of loss to the atmosphere by denitrification have not yet been quantitatively determined, atmospheric deposition to the watershed appears to be sufficient to account for essentially all the dissolved nitrate and ammonium and total organic N flow in the river. After deposition most of the nitrate may be transformed to other chemical forms during the flow, except possibly under high flow conditions that mainly occur in winter. However, either nitrate or the other forms could, with high efficiency, reach the estuary and be available for its marine biological processes.

Estimating estuarine flushing and residence times in Charlotte Harbor, Florida. via salt balance and a box model

We present a new concept and techniques for processing flow and salinity data and calibrating a box model designed to estimate water residence times in Charlotte Harbor, a large estuary in southwestern Florida. The new concept is that, over many tidal cycles, the tidally averaged “flow” (Qg) of water from the Gulf of Mexico with a salinity of 35‰ can be treated as a constant at any point in the estuary. This flow is used in a simple mixing equation to predict salinity in the estuary at different river inflows, and the predicted salinities are used to compute residence times for water in the estuary. The techniques developed to achieve optimal precision in the relation between river inflow and salinity include a newly derived equation to fit Qg by a least‐squares method and a procedure to determine the optimal averaging period for river inflow. Results from Charlotte Harbor indicate that, under average (70 m3 s−1) river inflow, 95% of the original water present in the harbor flushes into the gulf in 130 d.

Extracellular Enzyme Activity of Some Saprolegniales from a Florida Estuary

Click to increase image sizeClick to decrease image sizeKey Words: SaprolegnialesSaprolegniaAchlyaAphanomycesenzymesfishpathogendisease

Extracellular Enzyme Activity of Some Saprolegniales from a Florida Estuary

highly successful in that calculated numbers of saprolegniaceous spores fell within 2% of num? bers known to be present. In recent field trials we compared our Natrosol technique with the agar pour plate method (Wil? loughby and Collins, 1966) and the Polycell-gel procedure (Willoughby et al, 1984). Estimates derived from the Natrosol assay were 38% higher than those from the agar method and 55% higher than those using Polycell-gel. In addition to detecting more water mold propagules, the Natrosol assay proved far less laborious. Agar and Poly? cell-gel samples contained fourto six-fold more germinating spores (mostly non-saprolegniaceous) than did Natrosol plates and usually more than 95% of Natrosol method germlings proved to be water molds.

Occurrence of Gunterichthys longipenis (Osteichthys: Bythitidae) in a Southwest Florida Estuary

Occurrence of Gunterichthys longipenis (Osteichthys: Bythitidae) in a Southwest Florida Estuary

Deposition and persistence of aerially-applied fenthion in a Florida estuary.

Deposition and persistence of aerially-applied fenthion in a Florida estuary.