Spatial and seasonal patterns of periphyton biomass and productivity in the northern Everglades,Florida, U.S.A.

We sampled periphyton in dominant habitats at oligotrophic and eutrophic sites in the northern Everglades during the wet and the dryseasons to determine the effects of nutrient enrichment on periphytonbiomass, taxonomic composition, productivity, and phosphorus storage. Arealbiomass was high (100–1600 g ash-free dry mass [AFDM]m⁻²) in oligotrophic sloughs and in stands of the emergentmacrophyte Eleocharis cellulosa, but was low in adjacent stands of sawgrass,Cladium jamaicense (7–52 g AFDM m⁻²). Epipelon biomasswas high throughout the year at oligotrophic sites whereas epiphyton andmetaphyton biomass varied seasonally and peaked during the wet season.Periphyton biomass was low (3–68 g AFDM m⁻²) and limitedto epiphyton and metaphyton in open-water habitats at eutrophic sites andwas undetectable in cattail stands (Typha domingensis) that covered morethan 90% of the marsh in these areas. Oligotrophic periphytonassemblages exhibited strong seasonal shifts in species composition and weredominated by cyanobacteria (e.g., Chroococcus turgidus, Scytonema hofmannii)during the wet season and diatoms (e.g. Amphora lineolata, Mastogloiasmithii) during the dry season. Eutrophic assemblages were dominated byCyanobacteria (e.g., Oscillatoria princeps) and green algae (e.g., Spirogyraspp.) and exhibited comparatively little seasonality. Biomass-specific grossprimary productivity (GPP) of periphyton assemblages in eutrophic openwaters was higher than for comparable slough assemblages, but areal GPP wassimilar in these eutrophic (0.9–9.1 g C m⁻²d⁻¹) and oligotrophic (1.75–11.49 g C m⁻²d⁻¹) habitats. On a habitat-weighted basis, areal periphytonGPP was 6- to 30-fold lower in eutrophic areas of the marsh due to extensiveTypha stands that were devoid of periphyton. Periphyton at eutrophic siteshad higher P content and uptake rates than the oligotrophic assemblage, butstored only 5% as much P because of the lower areal biomass.Eutrophication in the Everglades has resulted in a decrease in periphytonbiomass and its contribution to marsh primary productivity. These changesmay have important implications for efforts to manage this wetland in asustainable manner. This revised version was published online in July 2006 with corrections to the Cover Date.     

Seasonal transmission of Fasciola hepatica in north central Florida (U.S.A.)

To assess seasonal transmission of Fasciola hepatica 37 groups of fluke-free tracer sheep, one group of four sheep each month in succession, grazed an infected pasture in north central Florida (U.S.A.) from June 1984 to June 1987. At the end of each month, tracers were moved to a fluke-free barn for 2 months, then necropsied and flukes counted. Fluke transmission mostly occurred during the first half of the year, with peak transmission from February to April. No transmission occurred during the warm summer months, having ceased in either May or June of each year to begin again in late autumn or early winter (November-January).     

Bivalve enhancement and restoration strategies in Florida,U.S.A.

In Florida, U.S.A. populations of recreationally and commercially important bivalve molluscs are stressed by a variety of factors, including habitat degradation, overfishing and development. Bivalves such as the bay scallop, Argopecten irradians, and the hard clam, Mercenaria spp., are uniquely positioned to benefit from restoration and enhancement activities because of the physical setting in which they live or because of recent efforts to restore habitat. For bay scallops, a major restoration effort has been implemented on the west coast of Florida. Adult scallops are collected from the target site and spawned in the laboratory. The offspring are cultured in ponds until they reach an average shell height of approximately 30 mm and then are planted in cages at the target site from which the parents were collected. Parents and offspring are genetically monitored, as are new recruits sampled at a variety of sites along the coast. The ultimate goal of this restoration program is to create concentrated patches of spawners that will supply recruits to west Florida seagrass beds. For hard clams, three different strategies are being tested to determine the most ecologically and economically feasible approach to use to enhance harvestable clam populations. Hard clams are occasionally abundant in the Indian River lagoon on the east central coast of the state, but transportation causeways fragment the lagoon into a series of basins that are largely isolated from one another. At any time, only a subset of the basins that compose the lagoon may be environmentally suitable for supporting the sensitive larval and juvenile stages of hard clams, and the members of that subset change constantly as environmental conditions change in the lagoon. Transplanting spawner stock, seeding juveniles under a variety of protective treatments, and injecting fertilized eggs directly into the lagoon are each being tested for their effectiveness in exploiting environmentally appropriate conditions and producing successful settlement events. Each strategy is being tested for its ecological and economic suitability, and the most appropriate strategy will be implemented in an effort to maintain clam abundance at a level where licensed clammers in the Indian River region can realize a minimum income from the fishery, even when naturally recruiting clam stocks are depleted.     

Savanna in central Wisconsin,U.S.A.

Summary A black oak savanna in central Wisconsin was analyzed in detail, including canopy trees, understory and tree seedlings. Although many authors have held that savanna in this region is a subclimax maintained by fire, this stand, unburned for many years, shows a high degree of stability and very little trend toward the postulated increase in trees. Of the 25 most frequent understory species, 80% have higher affinity for prairie or other very open habitats than for forest. Although oak seedlings had 72% frequency in 1 m² quadrats, their growth is exceedingly slow, while dieback and mortality are very high; few survive to 1 m in height and saplings are nearly absent. The tree canopy at 40% is low in relation to B. A., probably due to frequent wind and lightning damage. The inhibition of oak seedlings which prevents succession toward forest appears to be caused by a combination of frost, drouth, sandy soil of low water retaining capacity, interspecific competition and allelopathy; seedlings in an adjacent old field grow approximately 3 times faster, with little injury or mortality. Light grazing in early years of settlement may have allowed a temporary increase in tree establishment, since over 2/3 of the present canopy trees appear to be in one age group of 105–110 years. On the basis of this evidence we propose that at least some savanna sites in this region are naturally stable communities maintained by a complex interaction of the local climate, edaphic factors, and the existing community; fire is not an essential factor.

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Résumé La Savane à Chêne noir du Wisconsin central est analysée en détail, comprenant arbres, arbustes et semis d'arbres. Beaucoup d'auteurs considèrent cette Savane d?e à l'incendie. Notre groupement pas soumis à l'incendie depuis beaucoup d'années montre un haut degré de stabilité. Des 25 espèces les plus fréquentes du sous-bois 80% montrent davantage d'affinité avec la prairie où d'autres stations ouvertes qu'avec la forêt. Sur une surface de 1 m² les semis deQuercus ont une fréquence de 72%. Ils poussent très lentement et la mortalité est très grande, la hauteur de la strate arbustive, influencée par les vents fréquents est faible. L'évolution très lente des semis de Chêne semble causée par une combinaison de froid, sêcheresse, sol sablonneux, d'une faible capacité de retenu d'eau, concurrence interspécifique. Dans un vieux champ, les semis poussent à peu près 3 fois plus vite et montrent une plus faible mortalité. Plus de 2/3 des individus de la strate arborescente ont 105–110 ans. Tenant compte de ces faits, nous pouvons admettre qu'au moins certaines Savanes de cette région sont des unités naturelles, stables, maintenues dans cet état par une interaction du climat local, des facteurs édaphiques et de la végétation existante. Le feu n'est pas un facteur essentiel.

     

Savanna in central Wisconsin,U.S.A.

Summary A black oak savanna in central Wisconsin was analyzed in detail, including canopy trees, understory and tree seedlings. Although many authors have held that savanna in this region is a subclimax maintained by fire, this stand, unburned for many years, shows a high degree of stability and very little trend toward the postulated increase in trees. Of the 25 most frequent understory species, 80 % have higher affinity for prairie or other very open habitats than for forest. Although oak seedlings had 72 % frequency in 1 m² quadrats, their growth is exceedingly slow, while dieback and mortality are very high; few survive to 1 m in height and saplings are nearly absent. The tree canopy at 40 % is low in relation to B. A., probably due to frequent wind and lightning damage. The inhibition of oak seedlings which prevents succession toward forest appears to be caused by a combination of frost, drouth, sandy soil of low water retaining capacity, interspecific competition and allelopathy; seedlings in an adjacent old field grow approximately 3 times faster, with little injury or mortality. Light grazing in early years of settlement may have allowed a temporary increase in tree establishment, since over 2/3 of the present canopy trees appear to be in one age group of 105–110 years. On the basis of this evidence we propose that at least some savanna sites in this region are naturally stable communities maintained by a complex interaction of the local climate, edaphic factors, and the existing community; fire is not an essential factor.

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Résumé La Savane à Chêne noir du Wisconsin central est analysée en détail, comprenant arbres, arbustes et semis d'arbres. Beaucoup d'auteurs considèrent cette Savane d?e à l'incendie. Notre groupement pas soumis à l'incendie depuis beaucoup d'années montre un haut degré de stabilité. Des 25 espèces les plus fréquentes du sous-bois 80 % montrent davantage d'affinité avec la prairie où d'autres stations ouvertes qu'avec la forêt. Sur une surface de 1 m² les semis deQuercus ont une fréquence de 72 %. Ils poussent très lentement et la mortalité est très grande, la hauteur de la strate arbustive, influencée par les vents fréquents est faible. L'évolution très lente des semis de Chêne semble causée par une combinaison de froid, sêcheresse, sol sablonneux, d'une faible capacité de retenu d'eau, concurrence interspécifique. Dans un vieux champ, les semis poussent à peu près 3 fois plus vite et montrent une plus faible mortalité. Plus de 2/3 des individus de la strate arborescente ont 105–110 ans. Tenant compte de ces faits, nous pouvons admettre qu'au moins certaines Savanes de cette région sont des unités naturelles, stables, maintenues dans cet état par une interaction du climat local, des facteurs édaphiques et de la végétation existante. Le feu n'est pas un facteur essentiel.

     

The Kissimmee River Restoration Project and Evaluation Program,Florida, U.S.A.

Over the past decade, restoration of the Kissimmee River in central Florida has received considerable attention from local, state, national, and international media. In terms of areal extent, project cost, and ecological evaluation it is one of the largest and most comprehensive river restoration projects in the world. The goal of reestablishing ecological integrity involves restoring the physical attributes and the hydrologic processes that were lost after channelization of the river in the 1960s. The project is expected to restore over 80 km² of floodplain wetlands and reestablish over 70 km of river channel. Restoration construction began in 1999; to date, three construction phases have been completed, with the final phase of construction slated for completion in 2019. Restoration evaluation is widely viewed as a critical component of any restoration project. Equally important is the dissemination of information gained from restoration evaluation programs. This introductory article presents a brief overview of project history and outlines the approach and logic of the Kissimmee River Restoration Evaluation Program. The following papers present the results of ecological studies conducted before and after completion of the first phase of restoration construction. This first phase reestablished flow through 23 km of reconnected river channels and seasonally inundated a large portion (approximately 2,900 ha) of the floodplain within the Phase I project area. Although these studies present interim responses prior to full hydrologic restoration, results suggest that the ecosystem is responding largely as predicted by performance measures developed prior to restoration construction.     

Influence of habitat on grouper abundance in the Florida Keys, U.S.A.

There was a significant inshore to offshore pattern in grouper species composition and density on Florida Keys coral reefs. Red grouper Epinephelus morio and black grouper Mycteroperca bonaci were most abundant on inshore patch reefs. Graysby Cephalopholis cruentata was most abundant on offshore reef types. Density among sites ranged from 0 to 0·43, 0 to 0·26 and 0 to 1·23 100 m⁻² for red grouper, black grouper, and graysby, respectively. Grouper density exhibited no consistency among sites within similar reef types. The densities of red and black grouper were correlated significantly with either physical or biotic habitat parameters. Graysby were observed in microhabitats with whose benthic features differed significantly from the surrounding habitat. This species was observed in high-relief areas with significantly less octocoral species and colony densities. Larger graysby were observed in areas of higher relief and less octocorals than smaller graysby. Habitat was one of several important factors influencing the distribution of groupers among coral reefs types in the Florida Keys.     

Ecology and management of Melaleuca quinquenervia,an invader of wetlands in Florida,U.S.A.

Invasive weeds are potent agents of environmental change. Wetlands are valuable environments that frequently are impinged by a variety of threats including invasive weeds. Melaleuca quinquenervia (Cav.) S.T. Blake (broad-leaved paperbark), though experiencing major diminishment of native populations in Australia, is naturalized and highly invasive in most wetland habitats of south Florida, U.S.A., where it infests more than 202,000 ha. Wetlands in south Florida, including such renowned areas as the Everglades, are being transformed into M. quinquenervia swamps, with major environmental and economic impacts. Current management methods include herbicides, mechanical or hand removal of plants, flooding, and prescribed burning. Insufficient information, high costs, non-target impacts, and the resilience of M. quinquenervia (trunk and root sprouts and massive canopy seed banks) greatly constrain the effectiveness of these control methods. Biological control offers long-term management potential, most likely by reducing the rate of spread and the vitality and growth rate of plants, thus rendering them more vulnerable to other environmental stresses and control methods. The leaf weevil Oxyops vitiosa Pascoe, a natural enemy of M. quinquenervia in Australia, will likely be the first biocontrol agent released against the weed in Florida. More information is needed, especially ecological data, to better understand the invasiveness of M. quinquenervia in Florida and to facilitate its management there.     

Piscivore Responses to Enhancement of the Channelized Kissimmee River,Florida, U.S.A.

Evaluation of the success of ecosystem restoration projects requires identification of appropriate ecological metrics. Comparison of reconstructed food webs (or subsets thereof) from restored and non‐restored habitats may be a valuable tool to evaluate restoration success because food webs help identify critical predator–prey relationships, keystone species, relative importance of direct and indirect trophic interactions, and other aspects of ecological function. We compared the diets of apex predatory fishes collected from enhanced and non‐enhanced portions of the channelized Kissimmee River, Florida, USA to determine whether food web structure responded to experimental hydrologic manipulations. Diets were reconstructed for black crappie (Pomoxis nigromaculatus), bowfin (Amia calva), chain pickerel (Esox niger), Florida gar (Lepisosteus platyrhincus), largemouth bass (Micropterus salmoides), and warmouth (Lepomis gulosus) collected from enhanced and non‐enhanced portions of the Kissimmee River. Prey eaten by apex predatory fishes in the enhanced portion of the Kissimmee River were quantitatively and qualitatively different from prey eaten in non‐enhanced portions of the river. Predators in the enhanced portion of the river had fewer empty stomachs, more prey items per individual, more prey types per individual, more fish prey per individual, greater overall richness of prey, and a multivariate suite of prey distinct from predators in non‐enhanced portions of the river. Results from hydrologic manipulations suggest that large‐scale restoration of hydrologic linkages between the main channel and floodplain habitats will positively affect food web structure and ecosystem function in the Kissimmee River.     

The spatial distribution of desmids in lakes in northern Minnesota, U.S.A.

As a result of studies in certain lakes in northern Minnesota it has been found that the spatial distribution of desmids in them depends especially on the following factors: the constitution, abundance and distribution of the lakes' submerged aquatic flora and the morphometry and consequent patterns of their water circulation. The study has also shown a positive relationship between the size of desmid cells present in the plankton and the extent of water circulation. The latter factor may determine the composition and hence the diversity of lake phytoplankton.     

Mallomonas wujekii (Synurophyceae), a new species from Florida, U.S.A.

A new species of Mallomonas, M. wujekii sp. nov., belonging to the Series Tonsuratae is described from a dilute, acidic locality in Florida, U.S.A. Bristle bearing domed scales are restricted to the anterior end, and scales are orientated with their longitudinal axes at a 60° to 90° angle with the longitudinal axis of the cell. Cells have three types of scales, domed anterior scales, domeless body scales and spined posterior scales. All scales possess papillae that are restricted to the shield and have one rib positioned on each end of the posterior flange. The new species is believed to be most closely related to Mallomonas tonsurata and M. galeiformis . The combination of characters of the bristles is unique among taxa of Mallomonas .     

Coastal wetland restoration improves habitat for juvenile sportfish in Tampa Bay,Florida, U.S.A.

Increasing human populations and urban development have led to losses of estuarine habitats for fish and wildlife. Where resource managers are restoring coastal wetlands, in addition to meeting goals related to hydrologic connectivity, biodiversity, and recreational opportunities, efforts are being made to provide habitat that is suitable for juvenile sportfish. An 18‐month study was conducted to compare juvenile sportfish use of natural, restored, and impacted sites along Tampa Bay, Florida, shorelines. Juvenile sportfish densities at restored sites were broadly comparable to natural sites and greater than at impacted sites. However, site‐specific differences in sportfish use did occur within site types. For example, one restored site had significantly higher densities of red drum Sciaenops ocellatus than any other site, while black drum Pogonias cromis were found exclusively at another restored site. To evaluate whether the restored sites are providing suitable habitat for juvenile fish, we assessed growth (estimated from counts of daily rings on otoliths) and condition (determined by lipid analyses) of juvenile common snook Centropomus undecimalis, an archetypal coastal wetland‐dependent species. Growth (0.43–0.56 mm SL/day) and condition (4.6–6.1% lipid of dry weight) exhibited only site‐specific differences and did not vary among natural, restored, and impacted site types. Although mortality rates of juvenile sportfish were not determined, use of a 40‐m seine found that densities of potential piscine predators in these coastal wetlands were relatively low compared to published studies of open estuarine shorelines. The restoration and creation of coastal wetlands in Tampa Bay provides improved habitat for juvenile sportfish.     

Response of river metabolism to restoration of flow in the Kissimmee River, Florida, U.S.A.

1. The single station diel oxygen curve method was used to determine the response of system metabolism to backfilling of a flood control canal and restoration of flow through the historic river channel of the Kissimmee River, a sub‐tropical, low gradient, blackwater river in central Florida, U.S.A. Gross primary productivity (GPP), community respiration (CR), the ratio of GPP/CR (P/R) and net daily metabolism (NDM) were estimated before and after canal backfilling and restoration of continuous flow through the river channel. 2. Restoration of flow through the river channel significantly increased reaeration rates and mean dissolved oxygen (DO) concentrations from <2 mg L⁻¹ before restoration of flow to 4.70 mg L⁻¹ after flow was restored. 3. Annual GPP and CR rates were 0.43 g O₂ m⁻² day⁻¹ and 1.61 g O₂ m⁻² day⁻¹ respectively, before restoration of flow. After restoration of flow, annual GPP and CR rates increased to 3.95 O₂ m⁻² day⁻¹ and 9.44 g O₂ m⁻² day⁻¹ respectively. 4. The ratio of P/R (mean of monthly values) increased from 0.29 during the prerestoration period to 0.51 after flow was restored, indicating an increase in autotrophic processes in the restored river channel. NDM values became more negative after flow was restored. 5. After flow was restored, metabolism parameters were generally similar to those reported for other blackwater river systems in the southeast U.S.A. Postrestoration DO concentrations met target values derived from free flowing, minimally impacted reference streams.     

Reproduction in an invasive exotic catfish Pterygoplichthys disjunctivus in Volusia Blue Spring,Florida, U.S.A.

Morphology and reproductive strategies of a population of invasive loricariid catfish, Pterygoplichthys disjunctivus, in Volusia Blue Spring, Florida, were examined using morphological characters, gonado‐somatic indices and batch fecundity. This species has cystovarian ovaries, a left ovary that is significantly larger than the right ovary, and is highly fecund. Ovaries contained multiple oocyte size classes and completely spent females were not found, both of which indicate that this species is a multiple spawner. Reproductive patterns changed significantly between the first (2005) and the last (2007) years of this study; female fish became capable of spawning at a smaller size, a greater proportion of the captured population were capable of spawning each year and female batch fecundity increased, as did male and female gonado‐somatic indices. Plasticity of P. disjunctivus reproductive patterns is discussed in relation to resource availability and environmental stability.     

Interim Response of Dissolved Oxygen to Reestablished Flow in the Kissimmee River,Florida, U.S.A.

Restoration of the Kissimmee River should have multiple ecological benefits including improved dissolved oxygen (DO) within the river channel. Channelization of the Kissimmee River virtually eliminated flow through the natural river channel. After channelization, chronically low DO concentrations were observed in the stagnant remnant channel. Although no DO data from before channelization exist, reference estimates of pre‐channelization conditions were derived from seven relatively unimpacted streams. Stations along the Kissimmee River were sampled for 3 years before construction of the first phase of the restoration project began and for up to 8 years after the completion of construction. After Phase I construction, DO concentrations in the area of the river channel to which flow had been restored increased significantly from 2.2 to 4.9 mg/L, which is similar to DO concentrations observed in the reference streams. Mean DO concentrations for the reference streams ranged from 4.6 to 6.7 mg/L. Comparison of reference data to data from the pre‐Phase I and post‐Phase I system suggests that channelization had a negative impact on DO and that DO concentrations in the post‐Phase I Kissimmee River channel have made a significant recovery. Long‐term data trends demonstrate that DO concentrations can be negatively impacted by high flow events and that recovery from these events is generally quick, suggesting some degree of resilience in the system.     

Forest communities of the northern whitefish range, rocky mountains, Montana, U.S.A.

The montane and subalpine forests of a mountain range in northwestern Montana were investigated using phytosociological and numerical methods. Twelve associations and two subassociations were identified, of which eight are described here for the first time. The forest vegetation of valleys and lower slopes is strongly affected by repeated fire and is placed in the new orderCalamagrostio-Pseudotsugetalia glaucae, which includes temperate, low elevation forests in inland regions of northwestern North America. These forests bear only weak resemblance to forests traditionally assigned to the classVaccinio-Piceetea, and occupy the habitats filled by broad-leaved forests elsewhere at temperate latitudes. Montane and subalpine forest vegetation is moister and has longer snow duration and a shorter growing season. Upper montane vegetation more closely resembles that of other temperate montane forests of the classVaccinio-Piceetea.     

Dynamics of the exotic Daphnia lumholtzii and native macro-zooplankton in a subtropical chain-of-lakes in Florida, U.S.A.

1. Seasonal dynamics of the exotic Daphnia lumholtzii and native macro-zooplankton species were studied for 2 years in six inter-connected lakes in Florida, U.S.A. The lakes ranged widely in pH, colour and trophic status, and were dominated by copepods.
2. All six lakes contained both D. lumholtzii and the native D. ambigua , but the two species did not overlap in time. D. ambigua was dominant in autumn–spring, coinciding with lower water temperature, higher transparency and lower nutrient and chlorophyll a (Chl a ) concentrations than in summer, when D. lumholtzii was dominant.
3. Based on the field observations, temperature optima were 24 °C for D. ambigua and 29 °C for D. lumholtzii , suggesting that temperature plays a role in determining dominance among the daphnids of subtropical Florida lakes.
4.  D. lumholtzii has not displaced native cladocerans but occupies a 'vacant' seasonal niche, unexploited due to the inability of native taxa to tolerate high temperature. Furthermore, D. lumholtzii did not significantly alter algal–zooplankton interactions. There was evidence of top–down control by grazing, but it was primarily attributable to the native taxa.     

Seasonal pheromone response by Ips pini in northern Arizona and western Montana, U.S.A.

1 Populations of Ips pini (Say) in northern Arizona and western Montana, U.S.A., were studied to determine regional pheromone response and to evaluate seasonal shifts in that response. A range of enantiomeric blends of the attractant ipsdienol, alone and in the presence of the synergist lanierone, were tested during spring and summer seasons over several years.
2 Both populations were most attracted to high levels of ( R )-(–)-ipsdienol, and lanierone was highly synergistic.
3 A significant seasonal shift in pheromone response between spring and summer seasons was found in both regions in both years. Shifts resulted in a more specific preference for the pheromone treatment of 97% ( R )-(–)-ipsdienol with lanierone.
4 Several coleopteran insect associates of I. pini also displayed responses to the ipsdienol and lanierone treatments. Temnochila chlorodia (Mannerheim) (Trogositidae), Enoclerus sphegeus (F.) (Cleridae) and, to a limited extent, Lasconotus laqueatus (LeConte) (Colydiidae) were attracted to higher proportions of ( R )-(–)-ipsdienol with no apparent reaction to the presence of lanierone. Orthotomicus latidens (LeConte) (Curculionidae: Scolytinae) was strongly attracted to ( S )-(+)-ipsdienol with Enoclerus lecontei (Wolcott) (Cleridae), Pityogenes carinulatus (LeConte) (Curculionidae: Scolytinae) and Hylurgops porosus (LeConte) (Curculionidae: Scolytinae) demonstrating some preferences for the ( S )-(+)-enantiomer. However, lanierone was synergistic for E. lecontei and P. carinulatus , inhibitory for O. latidens , and produced no significant reaction for H. porosus . Elacatis sp. (Salpingidae, previously Othniidae) was attracted to the presence of ipsdienol but displayed no preference to the enantiomeric ratios of ipsdienol or the presence of lanierone.