Crustacean epifauna of seagrass and macroalgae in Apalachee Bay,Florida, USA

Epifaunal crustaceans on turtlegrass (Thalassia testudinum) and five dominant macroalgae (Anadyomene stellata, Digenia simplex, Halimeda incrassata, Laurencia poitei and Penicillus lamourouxii) were quantitatively sampled bimonthly over a one-year period from September 1979 to September 1980 in a subtropical seagrass meadow in Apalachee Bay, Florida (northeastern Gulf of Mexico). These plant species exhibited a wide range of morphologies, with surface area-to-biomass ratios differing by over 2.5 times. A similar suite of crustaceans occurred on all macrophytes despite differences in shape or architecture among plant species. Relative abundances of many crustaceans, however, varied among plant hosts. Similarity analysis indicated that the epifaunal associates of T. testudinum were distinct from those of the macroalgae. Species richness was generally higher on turtlegrass than on any of the macroalgae. Abundances of total crustaceans per plant biomass or per plant surface area, on the other hand, were greater on all macroalgal species compared to the seagrass. Abundances (per plant biomass or plant surface area) of 14 of the 16 numerically dominant epifaunal species differed significantly among macrophytes. Twelve of the 16 species had greater abundance on one or more macroalgae, while only two species were more abundant on T. testudinum. Almost half of the dominant species had greatest abundances on the branching red alga L. poitei. Although abundances per plant biomass and plant surface area were greater on macroalgae relative to turtlegrass, densities (individuals per meter square of bottom) of animals associated with T. testudinum were significantly greater than those associated with macroalgae, primarily because of the greater abundance of turtlegrass in the grass bed. Both surface area-to-biomass ratios and degree of branching were poorly correlated with epifaunal abundance and number of species. Neither structural feature is an adequate predictor of faunal abundance and species richness among plant species, especially when macrophytes with very different morphologies are compared.     

Factors influencing the association patterns of Hippolyte zostericola and Palaemonetes intermedius (Decapoda: Natantia) with seagrasses of the Indian River Lagoon, Florida

The ecological role and the association of Hippolyte zostericola (Smith, 1873) (Decapoda: Natantia) with different seagrass species in the Indian River Lagoon (Florida, USA) were investigated through field sampling and the analysis of diet, size–frequency distributions and laboratory experiments. Gut contents suggested that H. zostericola is a mesograzer which may be important in the transfer of primary production to higher trophic levels. Population size–frequency distributions showed a polymodal pattern variable according to the site. Preference experiments indicated that choice of seagrass species is not influenced by the available surface area of seagrass blades, nor by the presence of epiphytic food. Significant responses of the shrimp to the ambient light field, mediated by the seagrass canopy, were detected. A clear negative phototropism was observed for H. zostericola which may be an adaptive response to improve avoidance of visual predators. Received: 1 February 1998 / Accepted: 21 December 1998     

Florida,USA, Port Experience with Marpol Annex V

Abstract

This study assesses the effectiveness of MARPOL Annex V regulations, hereafter referred to as the Annex, using observations of United States Department of Agriculture (USDA) personnel stationed at major Florida ports. the study was initiated at the request of the 1IOPS Marine Debris Workshop Steering Committee? and was designed to focus on Gulf and Caribbean experiences gained since the Annex became effective.     

Florida, USA, Port Experience with Marpol Annex V

This study assesses the effectiveness of MARPOL Annex V regulations, hereafter referred to as the Annex, using observations of United States Department of Agriculture (USDA) personnel stationed at major Florida ports. the study was initiated at the request of the 1IOPS Marine Debris Workshop Steering Committee* and was designed to focus on Gulf and Caribbean experiences gained since the Annex became effective.     

Estimating river flow effects on water ages by hydrodynamic modeling in Little Manatee River estuary, Florida, USA

The water age in a tidal river in Florida, Little Manatee River, has been investigated in this study by the application of a three-dimensional hydrodynamic model. In response to a pulse dye release in the upper end of the river boundary, the hydrodynamic model determines the water age for a given location by recording the time for the dye to reach the given river location. The hydrodynamic model uses horizontal curvilinear orthogonal grids to represent the complex river system that includes several bayous and tributaries. The model has was calibrated and verified in previous study by using two continuous data sets for a 6 month period. Satisfactory model verifications indicate that the hydrodynamic model is capable of quantifying the mixing and transport process for calculating the water age in the tidal river. For 17 freshwater inflow scenarios in the Little Manatee River, the hydrodynamic model was applied to simulate water ages along the main channel of the river at 2-km interval. Flow rates in the 17 scenarios varying from 0.26 to 76.56 m³/s cover the range of the observed flows in the Little Manatee River. Water ages from model predictions range from the minimum 1.2 days under the maximum 76.56 m³/s inflow condition to the 50 days under the minimum 0.26 m³/s inflow condition. Empirical regression equations at three selected stations, with the correlation coefficient R² above 0.96, were derived from numerical model simulations to correlate water ages to freshwater inflows. The empirical water-age equation derived from hydrodynamic model simulations can be used to provide quick and low-cost estimations of water ages in response to various inflow scenarios for studying physical–chemical and biological processes in the river.     

Changes in nutrient content and stable isotope ratios of C and N during decomposition of seagrasses and mangrove leaves along a nutrient availability gradient in Florida Bay, USA

The decomposition of the mangrove Rhizophora mangle and the seagrass Thalassia testudinum was examined using litterbags along a natural gradient in nutrient availability. Seagrass leaves had a higher fraction of their biomass in the labile pool (57%), compared to mangrove leaves (36%) and seagrass rhizomes (29%); the overall decomposition rates of the starting material reflected the fractionation into labile and refractory components. There was no relationship between the N or P content of the starting material and the decomposition rate.

Nutrient availability had no influence on decomposition rate, and mass was lost at the same rate from litterbags that were buried in the sediment and litterbags that were left on the sediment surface. The dynamics of N and P content during decomposition varied as a function of starting material and burial state. N content of decomposing mangrove leaves increased, but seagrass rhizomes decreased in N content during decomposition while there was no change in seagrass leaf N content. These same general patterns held for P content, but buried seagrass leaves increased in P content while surficial leaves decreased. δ¹³C and δ¹⁵N changed by as much as 2‰ during decomposition.     

Changes in nutrient content and stable isotope ratios of C and N during decomposition of seagrasses and mangrove leaves along a nutrient availability gradient in Florida Bay,USA

The decomposition of the mangrove Rhizophora mangle and the seagrass Thalassia testudinum was examined using litterbags along a natural gradient in nutrient availability. Seagrass leaves had a higher fraction of their biomass in the labile pool (57%), compared to mangrove leaves (36%) and seagrass rhizomes (29%); the overall decomposition rates of the starting material reflected the fractionation into labile and refractory components. There was no relationship between the N or P content of the starting material and the decomposition rate.

Nutrient availability had no influence on decomposition rate, and mass was lost at the same rate from litterbags that were buried in the sediment and litterbags that were left on the sediment surface. The dynamics of N and P content during decomposition varied as a function of starting material and burial state. N content of decomposing mangrove leaves increased, but seagrass rhizomes decreased in N content during decomposition while there was no change in seagrass leaf N content. These same general patterns held for P content, but buried seagrass leaves increased in P content while surficial leaves decreased. δ¹³C and δ¹⁵N changed by as much as 2‰ during decomposition.     

Diel variation and seasonal consistency in the fish assemblage of the non-estuarine Sulaibikhat Bay,Kuwait

In the period between September 1986 and August 1988, using an otter trawl, a total of 50 species from 30 families were captured in Sulaibikhat Bay, Kuwait. The dominant species were Liza carinata (Valenciennes), Pomadasys stridens (Forrskal) and Leiognathus brevirostris (Valenciennes). Although the total number of fishes captured in 1986–1987 and 1987–1988 differed by an order of magnitude, the seasonal changes in numbers, biomass and number of species in the intertidal and subtidal zones were consistent. Unbalanced three-way analysis of variance showed that significantly larger numbers of fishes and number of species, but not biomass, were captured in the intertidal at night compared to the intertidal during the day. This difference may be due to both increased net efficiency and movement of fishes into the intertidal zone at night to avoid piscivorous fishes that move from deep water into shallower water. During the day few fish are present in the intertidal zone and this may be to avoid predation by piscivorous birds. Several species of fishes were shown to have different patterns of behaviour during the diel period.     

Diel variation in chlorophyll a,carbohydrate and protein content of the marine diatom Skeletonema costatum

Skeletonema costatum (Greville) Cleve isolated from Narragansett Bay, USA, was incubated at 3 light intensities (ca. 0.008, 0.040 and 0.075 ly min^-1) under a 12 h light: 12 h dark (12L:12D) photoperiod at 2°, 10° and 20°C. Cellular chlorophyll a increased at intensities less than ca. 0.040 ly min^-1; increases occured within one photoperiod at temperatures above 10°C. Cellular carbohydrate increased with light intensity at all temperatures; increases during the photophase were due to net production of the dilute acid-soluble fraction. Cellular protein increased during the photoperiod at 10° and 20°C; there was little difference in cellular protein among all cultures after one photoperiod. The rate at which cellular chlorophyll a increased in response to a decrease in light suggests that diel variation in cellular chlorophyll a is temperature-dependent in S. costatum. Protein: carbohydrate ratios ranged from ca. 0.5 to 2.0 over a diel cycle; ratios increased at lower intensities and higher temperatures. The diel range in protein:carbohydrate ratios equals that in cultures developing nitrogen deficiency; thus, use of this ratio as an index to phytoplankton physiological state must account for diel light effects.     

Diel variation of TCO2 in the upper layer of oceanic waters reflects microbial composition,variation and possibly methane cycling

Six diel TCO₂ cycles determined by infrared (IR) photometry from five drift stations occupied between 24 February and 16 March 1979 in the mixed layer of the northwestern Caribbean Sea are examined. Comparison of TCO₂ variation with coincident salinity and O₂ variation demonstrated that TCO₂ often co-varied with these independently measured variables. During five diel cycles TCO₂ variation was characterized by nocturnal production and diurnal consumption. The inverse, diurnal production of CO₂, occurred downstream from Misteriosa Bank, whose corals apparently contributed to a water mass having a twofold increase of POC and a sixfold larger population of heterotrophic nanoplankters. For the five diel studies carried out in waters with balanced or nearly blanced heterotrophic and phototrophic components of the nanoplankton, CO₂ consumption at constant salinity always occurred between 06.00 and 09.00 hrs. Net uptake often continued through 15.00 hrs, but not always in the absence of significant salinity changes. At constant salinity net O₂ evolution never exceeded 0.5 mol l^-1 h^-1 while net CO₂ uptake consistently averaged 3 mol l^-1 h^-1 for an apparent net production of 36 mg C m^-3 h^-1, which greatly exceeds the O₂ changes and open ocean ¹⁴C estimates from the literature. Diurnal consumption was apparently balanced by nocturnal production of CO₂ so that no significant net daily change in TCO₂ was observed. Departures from theoretical PQ and RQ and the possibility of nocturnal variations in formaldehyde and carbonate alkalinity imply that chemotrophs, both methane producers and methane oxidizers, play a significant role in CO₂ cycling. This could be through the metabolism of the nonconservative gases CH₄, CO, and H₂, and a link between chemotrophy and phototrophy through these gases is hypothesized. These open system measurements were subject to diffusion and documentable patchiness, but temporal TCO₂ changes appear to indicate the net direction of microbiological activity and join a growing body of literature showing dynamic variation in CO₂ and O₂ that exceeds estimates by ¹⁴C bottle assays of carbon fixation.     

Long-term variation of organochlorine residues and assemblages of epibenthic organisms in a shallow North Florida (USA) estuary

A 4-year study (1972–1976) determined long-term trends of organochlorine residues (DDT, DDE, DDD, PCB's, mirex) and trawl-susceptible organisms in a shallow, river-dominated estuary in North Florida (Apalachicola Bay, USA). Moderate levels of such compounds were found in various species prior to the restricted use of DDT in 1972. A subsequent precipitous decline in organochlorine besidues was attributed to decreased upland usage, major flushing of the river basin in early 1973, and various factors associated with estuarine function. No mirex was found in sediments or aquatic organisms. Apparently, the half-life of organochlorines is relatively short in this bay system. Various statistical methods were used to test the relationships of different physico-chemical and biological parameters. During the 4-year study period, seasonal river flow fluctuations dominated water color, turbidity, salinity, nutrients (NO₃), chlorophyll a, and the temporal succession of fishes in the bay. Certain long-term trends of fish associations were noted; relative dominance of key fish species declined and stabilized while bay-wide species richness and diversity increased with time. Qualitative changes in species representation determined the long-term pattern of community variability. This was consonant with a distinctive fish fauna during the first year of sampling. The bay anchovy Anchoa mitchilli was dominant during 9 of the first 12 monts of the project; this influenced the time-related changes in community indices. Temporally clustered fish associations reflected the importance of river flow in the estuarine environment. Direct correlation of fish distribution with the rapid disappearance of organochlorine compounds was complicated by aperiodic natural phenomena such as storms and river fluctuations. Population and community trends appeared consistent with other studies showing similar patterns of dominance of stress-resistant fish populations and related changes in community parameters. In this case, the relatively predictable annual succession of fish associations allowed an appraisal of key forcing functions. Due to the high level of seasonal and annual biological variability in this estuary, there were some problems in the application of linear statistical models to the data base. Although the long-term trend of relative species representation is useful as an index of stress, new techniques are needed to analyze extensive field data so that functions such as trophic interactions are included in the estimation of causal relationships. There are indications that such effects could be related to the impact of organochlorine compounds on estuarine systems.     

Influence of predation on infaunal abundance in Upper Chesapeake Bay,USA

The importance of predators in controlling the densities of infaunal (>0.5 mm) organisms was investigated in the mesohaline region of the Upper Chesapeake Bay (USA) using field experiments. The role of predators in controlling infaunal density and community characteristics varied with habitat type, season (i.e., predator abundance) and developmental or successional stage of the community. Few infaunal species were adversely affected by predator exclusion. Species that increased greatly in abundance in the absence of predators (e.g. Eteone heteropoda, Streblospio benedicti, Nereis succinea, and juvenile Macoma balthica and Mya arenaria) lived near the sediment-water interface and had major population pulses from fall through spring. Species whose abundances increased moderately or were not affected by predator exclusion were deeper burrowing organisms (e.g. Heteromastus filiformis and adult Mya arenaria), or were relatively small organisms (e.g. Paraprionospio pinnata, Scolecolepides viridis and Peloscolex gabriellae) whose principal predators could be other members of the infauna. Competition did not appear to be an important factor controlling infaunal density in these experiments.This work is Contribution No. 973 of the Center for Environmental and Estuarine Studies of the University of Maryland     

Seasonal fluctuations of benthic macrofauna in the apalachicola estuary,Florida, USA: The role of predation

Long-term monitoring studies revealed a negative correlation between the abundance of bottom-feeding fishes (Leiostomus xanthurus and Micropogonias undulatus) and benthic macrofaunal density, suggesting a causal relationship. To test this hypothesis, large (3x3 m) topless predator-exclusion cages (mesh opening=6 mm) of a design that produced minimal physical artifacts were constructed at two shallow mud-bottom oligohaline stations. Two-sided control cages and uncaged control areas were also sampled Experiments coincided with maximum abundances of bottom-feeding fishes in the spring and motile macroinvertebrates (penaeid shrimp) in the fall. During short-term (two-month) exclusion experiments in the spring and fall of 1980, large predators (those excluded by 6-mm mesh) were not a major factor in regulating the densities of most macrofaunal species. Predation may be important during other seasons, although this possibility was not tested. Densities of Leiostomus xanthurus and Penaeus setiferus during 1980 were lower than in previous years. Despite the reduced abundance of bottom-feeding fishes, macrofaunal densities still declined during late winter/early spring. It is postulated that increased river flow and lowered salinities during the late winter/early spring may contribute to the decline of macrofaunal densities by reducing larval recruitment.     

Effect of Hurricane Eloise on the benthic fauna of Panama City Beach,Florida, USA

The effect of Hurricane Eloise in September, 1975 on the benthic fauna inhabiting the swash zone on Panama City Beach, Florida, USA is described. Damage by the storm to the beach and property was considerable. The effect of the storm on the benthic invertebrates was not adverse, as the number of individuals occurring in the swash zone was about the same after the storm as before. The number of species increased after the storm, but later decreased to approximate numbers before the storm. The increase in the number of species was mainly due to the influx of species that norusually accompanies a hurricane was probably a factor enabling benthic organisms that normally live in high salinities to survive.     

Larval abundance and recruitment of the sand dollar Dendraster excentricus in Monterey Bay,California, USA

Seasonal abundance of planktonic larvae of the sand dollar Dendraster excentricus was determined in Monterey Bay, California, USA. Larvae were counted from two offshore stations and also over a coastal sand dollar bed, and these data were compared with settlement in the sand dollar bed, with adult population structure and with adult reproductive condition. These measurements were made during the period July 1978 to October 1980 and in October 1981. Sand dollar larvae were most abundant in the plankton during the summer, a period when phytoplankton productivity tended to be high and currents were relatively slow and variable. In some years, small-scale current variations appeared to prevent many larvae in the open bay from reaching the nearshore sand dollar beds; however, in other years, massive shoreward transport of the larvae evidently did occur, since the adult population in the sand dollar bed exhibited a mode in size, indicating a large settlement. A comparison of settled individuals in 1980 and the adult size-frequency distribution in 1981 gives an estimated mortality rate of 88% yr^-1 for early juveniles of D. excentricus.     

Evidence for microfloral succession on allochthonous plant litter in Apalachicola Bay,Florida, USA

Changes in hydrolytic, respiratory,catabolic and lipid biosynthetic activities depend at least in part on successional changes in the microfloral populations of allochthonous plant litter incubated in a semi-tropical estuary. Initial colonization is by populations which have a high content of muramic acid relative to the adenosine triphosphate (ATP) and which are progressively displaced by a microflora with a lower ratio of muramic acid to ATP. Scanning electron micrography of the plant-litter microflora shows a succession of forms, with an initial bacterial colonization and its progressive displacement by more complex forms. Estimates of the microbial mass and the rates of phospholipid synthesis suggest that the detrital microflora has a relatively slow growth rate compared to its growth potential.     

Impact of kraft pulp-mill effluents on estuarine and coastal fishes in Apalachee Bay,Florida, USA

A 2-year field study was carried out to determine the impact of kraft pulp-mill effluents on the fish fauna of a shallow-bay system in north Florida (Apalachee Bay, USA). Offshore areas that received kraft-mill effluents (KME) displayed significant increases in color and turbidity and reductions in (benthic) dissolved oxygen compared to a nearby control area. Estuarine and marsh fish assemblages in areas of acute impact were severely reduced in terms of numbers of individuals (N) and species (S). Offshore areas exposed to varying (chronic) levels of KME were characterized by complex interactions that included seasonal variations of impact. A broad offshore area showed reductions in numbers of individuals and species taken per month. However, the cumulative (annual) number of species taken was the same for polluted and unpolluted (control) areas due to a recruitment of relatively rare species in the areas of impact. Such polluted areas showed decreased dominance as well as qualitative differences in species composition compared to control areas. Inshore bay stations that were most severely affected by KME were dominated by the bay anchovy, Anchoa mitchilli. While species richness and species diversity were lower at the highly stressed stations, in other outlying areas of moderate impact (reduced N and S) there were no reductions of such parameters compared to control areas. Thus, species diversity was not an indicator of pollution per se, and was useful only when taken in conjunction with various other parameters. Transition areas (between polluted and unpolluted portions of the bay) showed substantial (although periodic) increases in N, S, and species diversity. Equitability indices were unchanged in polluted portions of the bay. In general, the effects of KME on offshore fish assemblages appeared to be due to a complex combination of habitat alteration, reduced benthic productivity, and individual behavioral reactions. The alterations of fish assemblages were compared to other studies in this area on benthic macrophytes and invertebrates in an effort to assess the usefulness of various indices in studies on the long-term effects of pollution on estuarine and coastal systems. It was found that kraft pulp-mill effluents had a pronounced effect on the benthic standing crop of plants and animals, but that intensive sampling over prolonged periods of time was necessary for an adequate assessment of the problem. Overall, there were some significant changes in the biota such as reduced dominance and productivity in polluted areas that were similar for the various types of organisms sampled.     

Irrigation suitability of White River in Indiana,Midwestern USA

Climate change models consistently project future precipitation reduction and temperature increase during the crop growing season in the US Midwest, which may exacerbate surface water scarcity issues confronting regional agriculture. To maintain consistent crop yields under the risk of increased droughts, farmers may shift from rain-fed agriculture to irrigation agriculture, particularly during drought periods. There is an urgent need to understand whether surface water in the Midwest is suitable for irrigation. In this study, irrigation water quality was comprehensively analyzed for commonly used parameters regarding salt content including sodium adsorption ratio (SAR), adjusted sodium adsorption ratio (SAR_adj), soluble sodium percentage (SSP), electrical conductivity (EC), total dissolved solids (TDS), residual sodium bicarbonate (RSBC), magnesium adsorption ratio (MAR), permeability index (PI), Kelley’s ratio (KR), synthetic harmful coefficient (SHC), and salinity. Results indicate that water in the White River at Muncie was rated mostly in excellent to good condition with regard to irrigation quality. However, the irrigation suitability level exhibited two distinct patterns between May–July and August–October. Specifically, an average of 7.8% of the samples from May to July were unsuitable for irrigation, and an average of 24.5% of samples from August to October were unsuitable for irrigation considering all parameters. Flow rate change over time and the release of pollutants from wastewater treatment plants and combine sewage outflows to the White River impacted on the irrigation water quality variations of the river. This study showed that there are higher risks during the fall season for farmers to use surface water as an irrigation source, and this risk might be greater if extended or more frequent drought events occur in the future. To our best knowledge, this is the first peer-reviewed study on irrigation water quality assessment in the Midwest and provides useful information for farmers and decision makers to consider while formulating applications for irrigation.

     

Seasonal variation in paediatric blood lead levels in Syracuse,NY, USA

Venous blood lead values for 2,633 children aged 0–4 years in Syracuse, New York, collected between 1 April 1992 and 31 March 1993 were summarised by census tract for study of geographic variability. A demographic exposure model is presented showing housing stock and SES (socioeconomic status) parameters as the most significant predictor variables. A seasonal trend in blood lead levels was observed with late summer values about 40% higher than late winter values for census tracts with the highest geometric mean PbB levels. Seasonal variation is compared with a biokinetic uptake model to examine hypotheses about temporal variations in soil and dust lead exposure patterns.     

Simulating a natural fire regime on an Atlantic coast barrier island complex in Florida, USA

The HFire fire regime model was used to simulate the natural fire regime (prior to European settlement) on Kennedy Space Center, Merritt Island National Wildlife Refuge, Canaveral National Seashore, and Cape Canaveral Air Force Station, Florida. Model simulations were run for 500 years and the model was parameterized using information generated from previously published empirical studies on these properties (e.g., lightning fire ignition frequencies and ignition seasonality). A mosaic pattern of frequent small fires dominated this fire regime with rare but extremely large fires occurring during dry La Niña periods. This simulated fire size distribution very closely matched the previously published fire size distribution for lightning ignitions on these properties. A sensitivity analysis was performed to establish which parameters were most influential and the range of variation surrounding empirically parameterized model output. Dead fuel moisture and wind speed had the largest influence on model outcome. A wide range of variance was observed surrounding the composite simulation with the least being 6% in total burn frequency and the greatest being 49% in total area burned. Because simulation modeling is the best option for fire regime reconstruction in many rapidly growing shrub dominated systems, these results will be of interest to scientists and fire managers for delineating the natural fire regime on these properties, the southeastern United States and other fire adapted shrub systems worldwide.