Evaluation of Succession in an Estuarine Macrobenthic Soft-Bottom Community near Tampa,Florida

A subtidal macrobenthic infaunal community was quantitatively sampled monthly from February 1975 to July 1978 (42 months). During that period, complete defaunation (presumably due to hypoxia) occurred three times at approximately annual intervals. The recovery of the community was examined for successional patterns by quantitative and qualitative normal and inverse classification analyses and by rank-order analysis of the dominant species. There was no consistent pattern of succession from recovery to recovery. Samples taken just after defaunation were not similar to each other and no consistent suites of species were detected. Classical succession in which suites of species are successively replaced by other suites until a persisting suite of species occurs (faciliation model) was not found. Other models of succession are discussed.     

Microbial Biogeography along an Estuarine Salinity Gradient: Combined Influences of Bacterial Growth and Residence Time

Shifts in bacterioplankton community composition along the salinity gradient of the Parker River estuary and Plum Island Sound, in northeastern Massachusetts, were related to residence time and bacterial community doubling time in spring, summer, and fall seasons. Bacterial community composition was characterized with denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA. Average community doubling time was calculated from bacterial production ([¹⁴C]leucine incorporation) and bacterial abundance (direct counts). Freshwater and marine populations advected into the estuary represented a large fraction of the bacterioplankton community in all seasons. However, a unique estuarine community formed at intermediate salinities in summer and fall, when average doubling time was much shorter than water residence time, but not in spring, when doubling time was similar to residence time. Sequencing of DNA in DGGE bands demonstrated that most bands represented single phylotypes and that matching bands from different samples represented identical phylotypes. Most river and coastal ocean bacterioplankton were members of common freshwater and marine phylogenetic clusters within the phyla Proteobacteria, Bacteroidetes, and Actinobacteria. Estuarine bacterioplankton also belonged to these phyla but were related to clones and isolates from several different environments, including marine water columns, freshwater sediments, and soil.     

Norovirus Distribution within an Estuarine Environment

Human norovirus (NoV) has been studied extensively as an important cause of gastroenteritis outbreaks worldwide. While oysters are a primary vehicle for infection, few studies have examined the wider distribution of NoV in the estuarine environment. Active shellfish-harvesting areas in Georgia were examined for the prevalence, genotype diversity, and concentrations of NoV in a variety of estuarine sample types over the course of 1 year. Of the 225 samples (9 oyster, 72 water, 72 63- to 200-μm plankton, and 72 >200-μm plankton) collected from 12 stations across two estuaries, 21 samples (9.3%) tested positive for NoV. By sample type, 55.0% (5/9) of oysters, 8.3% (6/72) of water samples, 11.1% (8/72) of 63- to 200-μm plankton samples, and 2.8% (2/72) of >200-μm plankton samples were positive for human NoV. The two NoV-positive >200-μm plankton samples, which contained mainly zooplankton, had the greatest quantity of NoV genomes (3.5 × 10¹³ and 1.7 × 10¹⁵ genomes g⁻¹) of any sample tested. The majority, 90.5% (19/21), of the samples tested positive for genogroup I NoV, and only 9.5% (2/21) of the samples tested positive for genogroup II. The high concentrations of NoV in plankton samples compared to water and oyster samples were unexpected and provide new insights into the presence and distribution of human NoV in the water environment.Human norovirus (NoV) is the leading cause of nonbacterial gastroenteritis worldwide (3). The Centers for Disease Control and Prevention (CDC) estimate that 23 million cases of acute gastroenteritis due to NoV occur each year, with symptoms including acute-onset vomiting, watery nonbloody diarrhea with abdominal cramps, and nausea (35). NoV outbreaks are pervasive for many reasons, but particularly because the virus is highly contagious and environmentally hardy (7). Additionally, infected individuals can excrete millions of viral particles in feces, leading to large numbers in sewage (16). Without proper removal or inactivation during wastewater treatment, the viruses can be released into recreational and shellfish-harvesting water bodies. Complete inactivation of NoV during sewage treatment is rare, and even in areas with proper wastewater treatment, contamination of oyster beds has been reported (5, 16, 17, 32, 38). Because bivalve molluscan shellfish are believed to act as filters for viruses and other microbes and because NoV is extremely infectious (as little as one viral particle is required for disease), the disease risk for consumption of raw oysters is high (27, 33, 40).Human NoV genogroup I (GI) and GII have been detected in oyster samples harvested from bays and estuaries worldwide (5, 10, 20). Ueki et al. (42) detected NoV in both shellfish and the surrounding river water in Japan and concluded that NoV contamination was most likely due to sewage and treated wastewater input into the river; however, no study has yet been able to characterize how NoV may be naturally distributed in an estuarine system, including in water, adhered to particles (including plankton), and in shellfish. The limitations are due in part to a lack of adequate detection methods specifically adapted to different environmental-sample types (8). Using a newly developed detection and quantification protocol (21), this study aimed to examine the distribution of NoV genogroups across a range of sample types within an estuarine system with the goal of better characterizing possible circulation of viruses between water, plankton, and oysters.     

Macrobenthic Communities of the Lower Chesapeake Bay. IV. Bay-wide Transects and the Inner Continental Shelf Benthic Studies of the Lower Chesapeake Bay 7

The distribution, abundance, and species composition of subtidal macrobenthic invertebrates of the lower Chesapeake Bay and the inner continental shelf off the mouth of the bay were studied. The benthos of the lower bay was sampled on two bay-wide transects sampled once in June 1978. The benthos of the inner shelf was sampled five times per year from 1979 through 1981. Data from this study were compared with data from previous studies of estuaries and the inner shelf of the mid-Atlantic Southeastern U.S.     

Macrobenthic community structure before, during, and after implementation of the Clean Water Act in the Neches River estuary (Texas)

Community structure of macrobenthos in the industrialized, tidal Neches River was studied 12 years after implementation of phase III of the Clean Water Act (CWA). Result were compared with a 1971–72 study conducted before implementation of the CWA and a 1984–85 study conducted after implementation of phases I & II of the CWA. The permitted BOD waste load decreased 93% between the 1971–72 and 1984–85 studies, then increased 19% between 1984–85 and the current study. A total of 50 taxa were collected during the 1971–72 study, 104 during the 1984–85 study, and 110 during the current study. Numbers of taxa per collection at each station increased by a factor of at least two between the 1971–72 and 1984–85 studies and were significantly different at the 0.0001 level. Numbers of taxa per collection at each station were not significantly different between the 1984–85 and the current study (p=0.286). Minimum collection densities in 1984–85 were higher than maximum densities in 1971–72 and were significantly different at the 0.0001 level. Collection densities were not significantly different between the 1984–85 study and the current study (p=0.374). Shannon's annual and station collection diversity values significantly increased (p=<0.05) between the 1971–72 and 1984–85 studies, but not between the 1984–85 and the current study (p=>0.05). Dendrograms of Sorenson's similarity index between all pairs of stations were more alike between the 1971–72 and the current study than between the 1984–85 and the current study. Evidence of some organic enrichment at the upper stations was indicated by the dominance of Limnodrilus hoffmeisteri and depressed oxygen concentrations. Environmental quality in the river has greatly improved since implementation of the CWA in 1972. Most of the improvments were due to phases I & II of the CWA, with little apparent change since implementation of phase III.     

Macrobenthic community structure before and after pollution abatement in the Neches River estuary (Texas)

Macrobenthos and physicochemical conditions in the lower 39 km of the Neches River estuary were studied from August, 1984 to May, 1985. The results were compared with data collected in 1971–1972. Between 1972 and 1984 the permitted BOD waste load in the tidal Neches River was reduced from 123 125 kg d to 8717 kg d. River discharge and dissolved oxygen concentrations were consistently higher and salinity was lower, during the same seasons, during the 1984–1985 study. A total of 50 taxa of macrobenthos were collected in 1971–1972 and 104 taxa were collected in 1984–1985. The numbers of taxa per collection at each station in 1984–1985 were at least twice those found in 1971–1972. Minimum densities in 1984–1985 were much higher than the maximum densities in 1971–1972 at all stations. Patterns of dominance, Sorenson's similarity index, and diversity ( ) values indicated improved water quality in 1984–1985. Statistical analysis of macrobenthic diversity indicated significant differences between upper estuary and lower estuary stations in 1971–1972. No significant differences were found in 1984–1985. Significant differences in numbers of taxa, macrobenthos densities, and values between the two studies were found. Reductions of waste loads, increased river discharge, and deepening of the navigation channel were among the factors that probably contributed most to the changes in community structure of the macrobenthos observed.     

Macrobenthic invertebrate richness and composition along a latitudinal gradient of European glacier-fed streams

1. The influence of 11 environmental variables on benthic macroinvertebrate communities was examined in seven glacier-fed European streams ranging from Svalbard in the north to the Pyrenees in the south. Between 4 and 11 near-pristine reaches were studied on each stream in 1996–97.
2. Taxonomic richness, measured at the family or subfamily (for Chironomidae) levels for insects and higher levels for non-insects, increased with latitude from Svalbard (3 taxa) to the Pyrenees (29 taxa).
3. A Generalized Additive Model (GAM) incorporating channel stability [Pfankuch Index (PFAN)], tractive force, Froude number (FROU), water conductivity (COND), suspended solids (SUSP) concentration, and maximum temperature explained 79% of the total deviance of the taxonomic richness per reach. Water temperature and the PFAN of stability made the highest contribution to this deviance. In the model, richness response to temperature was positive linear, whereas the response to the PFAN was bell-shaped with an optimum at an intermediate level of stability.
4. Generalized Additive Models calculated for the 16 most frequent taxa explained between 25 (Tipulidae) and 79% (Heptageniidae) of the deviance. In 10 models, more than 50% of the deviance was explained and 11 models had cross-validation correlation ratios above 0.5. Maximum temperature, the PFAN, SUSP and tractive force (TRAC) were the most frequently incorporated explanatory variables. Season and substrate characteristics were very rarely incorporated.
5. Our results highlight the strong deterministic nature of zoobenthic communities in glacier-fed streams and the prominent role of water temperature and substrate stability in determining longitudinal patterns of macroinvertebrate community structure. The GAMs are proposed as a tool for predicting changes of zoobenthic communities in glacier-fed streams under climate or hydrological change scenarios.     

Richness and Diversity of Bacterioplankton Species along an Estuarine Gradient in Moreton Bay, Australia

Bacterioplankton community diversity was investigated in the subtropical Brisbane River-Moreton Bay estuary, Australia (27°25′S, 153°5′E). Bacterial communities were studied using automated rRNA intergenic spacer analysis (ARISA), which amplifies 16S-23S ribosomal DNA internally transcribed spacer regions from mixed-community DNA and detects the separated products on a fragment analyzer. Samples were collected from eight sites throughout the estuary and east to the East Australian Current (Coral Sea). Bacterioplankton communities had the highest operational taxonomic unit (OTU) richness, as measured by ARISA at eastern bay stations (S [total richness] = 84 to 85 OTU) and the lowest richness in the Coral Sea (S = 39 to 59 OTU). Richness correlated positively with bacterial abundance; however, there were no strong correlations between diversity and salinity, NO₃⁻ and PO₄³⁻ concentrations, or chlorophyll a concentration. Bacterioplankton communities at the riverine stations were different from communities in the bay or Coral Sea. The main differences in OTU richness between stations were in taxa that each represented 0.1% (the detection limit) to 0.5% of the total amplified DNA, i.e., the “tail” of the distribution. We found that some bacterioplankton taxa are specific to distinct environments while others have a ubiquitous distribution from river to sea. Bacterioplankton richness and diversity patterns in the estuary are potentially a consequence of greater niche availability, mixing of local and adjacent environment communities, or intermediate disturbance. Furthermore, these results contrast with previous reports of spatially homogeneous bacterioplankton communities in other coastal waters.     

Biodegradation of Dichloromethane in an Estuarine Environment

Dichloromethane (DCM) is a toxic pollutant showing prolonged persistence in water. So far, biodegradation of DCM has only been reported in soils and freshwater systems. Herein, we studied whether or not biodegradation of DCM could occur in estuarine waters. Results showed over 90% mineralization of DCM in natural estuarine waters supplemented with DCM. Biodegradation of DCM in estuarine waters occurred by association of different bacterial species. Generally, two bacterial species participated in DCM degradation. Two bacterial consortia were obtained. Consortia were able to degrade around 80% of DCM in about 6 days. The species involved in the process were identified by 16S rRNA gene sequencing; a consortium was constituted by Pseudomonas sp. and Brevundimonas sp. and a second consortium was formed by Pseudomonas sp. and an Acinetobacter sp. Our results showed that DCM can be readily biodegraded in estuarine waters.     

Patterns of Fine Root Mass and Distribution along a Disturbance Gradient in a Tropical Montane Forest, Central Sulawesi (Indonesia)

Large parts of the remaining tropical moist forests of South-east Asia are encroached at their margins by selective logging, rattan harvesting and the establishment of small agroforest plantations under the rainforest canopy. These slight to heavy disturbances affect aboveground forest structure by reducing wood biomass and canopy cover; however, they may also have a profound impact on the belowground compartment. In a lower montane moist forest of Central Sulawesi, we studied the profile totals of fine root biomass (FRB_tot, roots <2 mm until 50 cm of soil depth) and of fine root necromass (FRN_tot), the vertical distribution of fine root mass, and the fine root live/dead ratio by root coring in 12 forest stands that represented a gradient in forest use (or disturbance) intensity (forest use type A: undisturbed natural forest, B and C: slightly or moderately disturbed forests with selective timber extraction, D: heavily disturbed cacao agroforest systems under a remaining rainforest cover; each forest types being replicated three times). FRB_tot decreased significantly from forest A to the disturbed B, C and D forests, and reached less than 60% of the FRB_tot value of A in the agroforest systems D. A similar decrease with increasing disturbance intensity was found for FRN_tot. Forest disturbance intensity had no significant influence on the vertical distribution of fine root biomass in the profiles. According to correlation and principal components analyses, fractional canopy cover was the most important factor influencing FRB_tot and FRN_tot, whereas diameter at breast height, stand basal area, stem density, soil pH and base saturation had only a minor or no influence on root mass. A reduction in canopy cover from 90% (forest type A) to 75% (types C and D) was associated with a reduction in FRB_tot by about 45% which indicates that timber extraction leads not only to canopy gaps but to corresponding ‘root gaps’ in the soil as well. We conclude that forest encroachment that is widespread in large parts of South-east Asia’s remaining rainforests significantly reduces tree fine root biomass and associated carbon sequestration, even if it is conducted at moderate intensities only.     

Sediment Composition Influences Spatial Variation in the Abundance of Human Pathogen Indicator Bacteria within an Estuarine Environment

Faecal contamination of estuarine and coastal waters can pose a risk to human health, particularly in areas used for shellfish production or recreation. Routine microbiological water quality testing highlights areas of faecal indicator bacteria (FIB) contamination within the water column, but fails to consider the abundance of FIB in sediments, which under certain hydrodynamic conditions can become resuspended. Sediments can enhance the survival of FIB in estuarine environments, but the influence of sediment composition on the ecology and abundance of FIB is poorly understood. To determine the relationship between sediment composition (grain size and organic matter) and the abundance of pathogen indicator bacteria (PIB), sediments were collected from four transverse transects of the Conwy estuary, UK. The abundance of culturable Escherichia coli, total coliforms, enterococci, Campylobacter, Salmonella and Vibrio spp. in sediments was determined in relation to sediment grain size, organic matter content, salinity, depth and temperature. Sediments that contained higher proportions of silt and/or clay and associated organic matter content showed significant positive correlations with the abundance of PIB. Furthermore, the abundance of each bacterial group was positively correlated with the presence of all other groups enumerated. Campylobacter spp. were not isolated from estuarine sediments. Comparisons of the number of culturable E. coli, total coliforms and Vibrio spp. in sediments and the water column revealed that their abundance was 281, 433 and 58-fold greater in sediments (colony forming units (CFU)/100g) when compared with the water column (CFU/100ml), respectively. These data provide important insights into sediment compositions that promote the abundance of PIB in estuarine environments, with important implications for the modelling and prediction of public health risk based on sediment resuspension and transport.     

Vertical Distribution of Denitrification in an Estuarine Sediment: Integrating Sediment Flowthrough Reactor Experiments and Microprofiling via Reactive Transport Modeling

Denitrifying activity in a sediment from the freshwater part of a polluted estuary in northwest Europe was quantified using two independent approaches. High-resolution N₂O microprofiles were recorded in sediment cores to which acetylene was added to the overlying water and injected laterally into the sediment. The vertical distribution of the rate of denitrification supported by nitrate uptake from the overlying water was then derived from the time series N₂O concentration profiles. The rates obtained for the core incubations were compared to the rates predicted by a forward reactive transport model, which included rate expression for denitrification calibrated with potential rate measurements obtained in flowthrough reactors containing undisturbed, 1-cm-thick sediment slices. The two approaches yielded comparable rate profiles, with a near-surface, 2- to 3-mm narrow zone of denitrification and maximum in situ rates on the order of 200 to 300 nmol cm⁻³ h⁻¹. The maximum in situ rates were about twofold lower than the maximum potential rate for the 0- to 1-cm depth interval of the sediment, indicating that in situ denitrification was nitrate limited. The experimentally and model-derived rates of denitrification implied that there was nitrate uptake by the sediment at a rate that was on the order of 50 (± 10) nmol cm⁻² h⁻¹, which agreed well with direct nitrate flux measurements for core incubations. Reactive transport model calculations showed that benthic uptake of nitrate at the site is particularly sensitive to the nitrate concentration in the overlying water and the maximum potential rate of denitrification in the sediment.     

Benthic macrofauna and sediments in the Severn Estuary

In the Severn Estuary and Bristol Channel, a multivariate analysis indicated eight groupings of macrobenthic fauna, each associated with a different physical habitat. Samples were faunistically impoverished, especially in sublittoral areas, but greater species richness was associated with reefs of Sabellaria alveolata , which extended well into the estuary.     

Macrobenthic Communities of the Lower Chesapeake Bay. III. Southern Branch of the Elizabeth River

Macrobenthic invertebrates of an industrialized seaport ecosystem were studied seasonally from October, 1977 through July, 1978. Five stations were selected along the Southern Branch of the Elizabeth River, Virginia. The benthic community was dominated by eurytopic species that were not affected by minor to moderate stresses induced by man's activities in the seaport. Caution is required when benthic communities of the lower polyhaline to mesohaline zones of an estuary are used to indicate the effects of anthropomorphic alterations.     

Plant Functional Traits and the Distribution of West African Rain Forest Trees along the Rainfall Gradient

Plant morphological and physiological traits affect the way plants tolerate environmental stresses and therefore play an important role in shaping species distribution patterns in relation to environmental gradients. Despite our growing knowledge on the role of functional traits in structuring plant communities, few studies have tested their importance at large scales in the wet tropics. Here, we describe the distribution patterns of the most important West African rain forest timber species along the regional rainfall gradient and relate them to their functional traits. We found that the distribution patterns of 25 out of the 31 studied species (80%) were significantly related to mean annual rainfall. Shade tolerance and drought resistance were identified as the main strategy axes of variation. Wood density and leaf deciduousness emerged as the best predictor traits of species position along the rainfall gradient, explaining respectively 32 and 15 percent of the variation. Species traits tended to show stronger relationships with estimated optimum annual rainfall for each species than to the extreme rainfall conditions where they occur. The significant role of rainfall in shaping timber species distribution and the strong relationships between species traits and rainfall indicate that changes in climate, especially declining rainfall, could have strong effects on species composition and abundance in these tropical forests.     

Seasonality and Structure of a Macrobenthic Seagrass Community on the Florida Gulf Coast

Macrofauna at two intertidal sites, quantitatively sampled monthly for 25 months, exhibited distinct reoccurring population fluctuations which were poorly correlated with abiotic parameters. Faunal dominants, Laeonereis culveri and Onuphis simoni, showed reciprocal fluctuations. Laeonereis exhibited non-synchronized reproduction and recruitment while Onuphis exhibited synchronized release. Laeonereis peaked before Onuphis while Oniphis fluctuated with the majority of other species. The faunal dominants exhibited one cycle in autumn at both sites but also exhibited a cycle at only one site in spring. Temperature is thus not indicated as causal and detrital input was suggested as the overriding factor. A hypothesis was advanced that Laeonereis is an opportunistic species exploiting fresh detritus, while Onuphis is a detritus feeder utilizing bacterial populations.     

Spatial Subtidal Macrobenthic Distribution in Relation to Abiotic Conditions in the Lima Estuary, NW of Portugal

During the summer of 2002, sampling was carried out in the Lima estuary in order to compare the pattern of the macrobenthic community’s distribution in relation to physical and chemical variables. A total of 54 macrobenthic taxa were identified. Abundance, biomass and specific diversity varied among the twenty stations. Abundance ranged from 212 to 9856 ind./m², with an average of 1581 ind./m². Abra alba presented the highest density corresponding to 39.1% of the total specimens gathered, followed by Hediste diversicolor with 31.5%. Biomass ranged from 0.12 to 264.62 g AFDW/m², with an average of 17.58 g AFDW/m². Cerastoderma edule and A. alba were the species with a clear predominance in the total biomass, contributing 75.3 and 13.8%, respectively. The multivariate techniques used revealed a macrobenthic community with five distinct groups, particularly related to the sedimentological characteristics and salinity. These results demonstrated significant differences in macrobenthic assemblage’s composition along an estuarine gradient. For the first time the presence of the nonindigenous invasive species Corbicula fluminea was described in this estuary.     

东海春秋季大型底栖动物分布现状

根据 2 0 0 0年 11月和 2 0 0 1年 4月在 12 1°～ 12 7°E、2 6°～ 32°N之间的东海水域所设的 30个取样站所采集的5 2 6号采泥和 973号拖网样品 ,共计 392种大型底栖动物 ,报道了东海大陆架底栖动物的种类组成和数量分布。392种底栖动物中 ,多毛类 95种 ,软体动物 131种 ,甲壳类 118种 ,棘皮动物 4 8种。从分析结果看 ,底栖动物的种数自北向南和由近岸 (西部 )向外海 (东部 )逐渐增多。调查海区春季底栖动物平均生物量为 7.2 1g/m2 ,平均栖息密度为 132 .95个 /m2 ;秋季底栖动物的平均生物量为 8.79g/m2 ,平均栖息密度为 10 1.4 5个 /m2 。春秋季生物量及栖息密度等值线分布趋势无明显变化。在春秋季底栖动物生物量及栖息密度组成中均以多毛类占主要地位 ,春季生物量以多毛类和棘皮动物占优势。与 195 9～ 196 0年的全国海洋综合调查对东海底栖生物的调查结果比较 ,当前东海海域大型底栖生物的分布格局和生态学特点无明显变化 ,但春季的生物量较 195 9年低。