Hematodinium perezi, a parasitic dinoflagellate, infects and kills blue crabs, Callinectes sapidus, along the Atlantic and Gulf coasts of the United States. The parasite proliferates within host hemolymph and tissues, and also produces free-swimming biflagellated dinospores that emerge from infected crabs. Infections in C. sapidus recur annually, and it is not known if biotic or environmental reservoirs contribute to reinfection and outbreaks. To address this data gap, a quantitative PCR assay based on the internal transcribed spacer 2 (ITS2) region of H. perezi rRNA genes was developed to asses the temporal and spatial incidence of the parasite in Delaware and Maryland coastal bays.
A previously-used PCR assay for H. perezi, based on the small subunit rRNA gene sequence, was found to lack adequate species specificity to discriminate non-Hematodinium sp. dinoflagellate species in environmental samples. A new ITS2-targeted assay was developed and validated to detect H. perezi DNA in sediment and water samples using E. coli carrying the H. perezi rDNA genes. Application of the method to environmental samples identified potential hotspots in sediment in Indian River Inlet, DE and Chincoteague Bay, MD and VA. H. perezi DNA was not detected in co-occurring shrimp or snails, even during an outbreak of the parasite in C. sapidus.
H. perezi is present in water and sediment samples in Maryland and Delaware coastal bays from April through November with a wide spatial and temporal variability in incidence. Sampling sites with high levels of H. perezi DNA in both bays share characteristics of silty, organic sediments and low tidal currents. The environmental detection of H. perezi in spring, ahead of peak prevalence in crabs, points to gaps in our understanding of the parasite’s life history prior to infection in crabs as well as the mode of environmental transmission. To better understand the H. perezi life cycle will require further monitoring of the parasite in habitats as well as hosts. Improved understanding of potential environmental transmission to crabs will facilitate the development of disease forecasting.
Blue crab; Hematodinium; Parasite; Disease reservoir; Fishery
Hematodinium is a parasitic dinoflagellate and emerging pathogen of crustaceans. It preferably manifests in haemolymph of marine decapod crustaceans, killing a large variety of genera with significant impacts on fisheries worldwide. There is, however, evidence that some crustacean stocks harbor high prevalence, low intensity infections that may not result in widespread host mortality and are therefore hard to detect. The most widely used methods for detection of Hematodinium are conventional blood smears and polymerase chain reaction (PCR) against ribosomal RNAs. Blood smears demand a trained investigator, are labor intensive and not readily scalable for high-throughput sampling. PCRs only detect parasite DNA and can also suffer from false negatives and positives. In order to develop alternative detection tools for Hematodinium cells in decapod crustaceans we employed an immunological approach against a newly identified, abundant dinoflagellate-specific nuclear protein—Dinoflagellate/Viral NucleoProtein (DVNP). Both immunofluorescence assay (IFA) and Western blot methods against DVNP showed high sensitivity of detection. The Western blot detects Hematodinium parasites to levels of 25 parasites per milliliter of crustacean haemolymph, with the potential for sample pooling and screening of large samples. Using both PCR and these new tools, we have identified Hematodinium cells present in three new host crab taxa, at high prevalence but with no sign of pathogenesis. This extends the known range of Hematodinium to southern Australia.
This study reports on an emerging fungal disease of the edible crab, Cancer pagurus. Juvenile (prerecruit) crabs were found to be subject to this disease condition during the months of May to September at two intertidal sites in South Wales, United Kingdom. Histopathology revealed that the fungi overwhelm the host response in the tissues, leading to progressive septicemia. The causative agent of this infection was isolated and grown in pure culture and was identified as a member of the Ophiocordyceps clade by sequencing of the small subunit of the fungal ribosomal DNA (rDNA). Of the crabs naturally infected with the fungus, 94% had a coinfection with the parasitic dinoflagellate Hematodinium species. To determine if there was any interaction between the two disease-causing agents, apparently fungus-free crabs, both with and without natural Hematodinium infections, were challenged with the fungal isolate. The presence of Hematodinium caused a significant reduction in fungal multiplication in the hemocoel of the crabs in comparison to that in Hematodinium-free individuals. Histopathology of coinfected crabs showed a systemic multiplication of Hematodinium within host tissues, leading to a rapid death, while Hematodinium-free crabs experimentally infected with the fungal isolate died due to fungal sepsis (septicemia) with the same characteristic pathology as seen in natural infections.
Increasingly, diseases of marine organisms are recognized as significant biotic factors affecting ecosystem health. However, the responsible disease agents are often unknown and the discovery and description of novel parasites most often rely on morphological descriptions made by highly trained specialists. Here, we describe a new approach for parasite discovery, utilizing denaturing high-performance liquid chromatography (DHPLC) reverse-phase ion-paring technology. Systematic investigations of major DHPLC variables, including temperature, gradient conditions, and target amplicon characteristics were conducted to develop a mechanistic understanding of DNA fragment separation by DHPLC. As a model system, 18S rRNA genes from the blue crab (Callinectes sapidus) and a parasitic dinoflagellate Hematodinium sp. were used. Binding of 18S rRNA gene PCR amplicons to the DNA separation column in the presence of triethylammonium acetate (TEAA) was inversely correlated with temperature and could be predicted based on the estimated DNA helicity of the PCR amplicon. Amplicons of up to 498 bp were resolved as single chromatographic peaks if they had high (>95%) DNA helicity. Amplicons that differed by as few as 2 bp could be resolved. Separation of 18S rRNA gene PCR amplicons was optimized by simultaneous manipulation of both temperature and solvent gradients. The optimal conditions included targeting regions of high DNA helicity (>95%), temperatures in the range of 57 to 63°C, and a linear acetonitrile gradient from 13.75 to 17.5% acetonitrile in 0.1 M TEAA (55 to 70% buffer B) over a 9-min period. Under these conditions, amplicons from a variety of parasites and their hosts can be separated and detected by DHPLC.
Parasitic dinoflagellates of the genus Hematodinium are significant pathogens affecting the global decapod crustacean fishery. Despite this, considerable knowledge gaps exist regarding the life history of the pathogen in vivo, and the role of free living life stages in transmission to naïve hosts.
In this study, we describe a novel disease in European brown shrimp (Crangon crangon) caused by infection with a parasitic dinoflagellate of the genus Hematodinium. This is the second example host within the Infraorder Caridea (shrimp) and significantly, the first description within the superfamily Crangonoidea. Based upon analysis of the rRNA gene (SSU) and spacers (ITS1), the parasite in C. crangon is the same as that previously described infecting Nephrops norvegicus and Cancer pagurus from European seas, and to the parasite infecting several other commercially important crab species in the Northern Hemisphere. The parasite is however distinct from the type species, H. perezi, found infecting type hosts (Carcinus maenas and Liocarcinus depurator) from nearby sites within Europe. Despite these similarities, the current study has also described for the first time, a bacteria-like endosymbiont within dinospore stages of the parasite infecting shrimp. The endosymbionts were either contained individually within electron lucent vacuoles within the parasite cell cytoplasm, or remained in direct contact with the parasite cytoplasm or in some cases, the nucleoplasm. In all of these cases, no apparent detrimental effects of colonization were observed within the parasite cell.
The presence of bacteria-like endosymbionts within dinospore life stages presumes that the relationship between the dinoflagellate and the bacteria is extended beyond the period of liberation of spores from the infected host shrimp. In this context, a potential role of endosymbiosis in the survival of free-living stages of the parasite is possible. The finding offers a further intriguing insight into the life history of this enigmatic pathogen of marine crustacean hosts and highlights a potential for mixotrophy in the parasitic dinoflagellates contained within the genus Hematodinium.
ITS1; Phylogenetics; Dinoflagellate; Bacteria; Crustacean; Disease; Fishery
Recently, we described a novel denaturing high-performance liquid chromatography (DHPLC) approach useful for initial detection and identification of crustacean parasites. Because this approach utilizes general primers targeted to conserved regions of the 18S rRNA gene, a priori genetic sequence information on eukaryotic parasites is not required. This distinction provides a significant advantage over specifically targeted PCR assays that do not allow for the detection of unknown or unsuspected parasites. However, initial field evaluations of the DHPLC assay suggested that because of PCR-biased amplification of dominant host genes it was not possible to detect relatively rare parasite genes in infected crab tissue. Here, we describe the use of a peptide nucleic acid (PNA) PCR hybridization blocking probe in association with DHPLC (PNA-PCR DHPLC) to overcome inherent PCR bias associated with amplification of rare target genes by use of generic primers. This approach was utilized to detect infection of blue crabs (Callinectes sapidus) by the parasitic dinoflagellate Hematodinium sp. Evaluation of 76 crabs caught in Wassaw Sound, GA, indicated a 97% correspondence between detection of the parasite by use of a specific PCR diagnostic assay and that by use of PNA-PCR DHPLC. During these studies, we discovered one crab with an association with a previously undescribed protist symbiont. Phylogenetic analysis of the amplified symbiont 18S rRNA gene indicated that it is most closely related to the free-living kinetoplastid parasite Procryptobia sorokini. To our knowledge, this is the first report of this parasite group in a decapod crab and of this organism exhibiting a presumably parasitic life history.
Microorganisms associated with coastal sands serve as a natural biofilter, providing essential nutrient recycling in nearshore environments and acting to maintain coastal ecosystem health. Anthropogenic stressors often impact these ecosystems, but little is known about whether these disturbances can be identified through microbial community change. The blowout of the Macondo Prospect reservoir on April 20, 2010, which released oil hydrocarbons into the Gulf of Mexico, presented an opportunity to examine whether microbial community composition might provide a sensitive measure of ecosystem disturbance. Samples were collected on four occasions, beginning in mid-June, during initial beach oiling, until mid-November from surface sand and surf zone waters at seven beaches stretching from Bay St. Louis, MS to St. George Island, FL USA. Oil hydrocarbon measurements and NOAA shoreline assessments indicated little to no impact on the two most eastern beaches (controls). Sequence comparisons of bacterial ribosomal RNA gene hypervariable regions isolated from beach sands located to the east and west of Mobile Bay in Alabama demonstrated that regional drivers account for markedly different bacterial communities. Individual beaches had unique community signatures that persisted over time and exhibited spatial relationships, where community similarity decreased as horizontal distance between samples increased from one to hundreds of meters. In contrast, sequence analyses detected larger temporal and less spatial variation among the water samples. Superimposed upon these beach community distance and time relationships, was increased variability in bacterial community composition from oil hydrocarbon contaminated sands. The increased variability was observed among the core, resident, and transient community members, indicating the occurrence of community-wide impacts rather than solely an overprinting of oil hydrocarbon-degrading bacteria onto otherwise relatively stable sand population structures. Among sequences classified to genus, Alcanivorax, Alteromonas, Marinobacter, Winogradskyella, and Zeaxanthinibacter exhibited the largest relative abundance increases in oiled sands.
A study was conducted during the summer of 2009 (from July to September) to characterize mosquito communities among different habitats in five historically ditched tidal salt marshes and three adjacent wooded areas in the E.A. Vaughn Wetland Management Area on the Maryland Delmarva Peninsula, USA. Study marshes are characteristic of Atlantic coastal salt marshes that had undergone grid ditching from the 1930s to 1950s. In the autumn of 2008 (October and November) ditches were plugged near their outlets in two (‘experimental’) marshes with the aim to restore their natural tidal hydrology. The three other marshes were not plugged. Marshes were sampled from July to September in 2009 by using standard dip count method. A total of 2,457 mosquito larvae representing six species were collected on 15.4% (86/557) of all sample occasions and 399 adults representing four mosquito species were collected from landing counts. Aedes sollicitans, Anopheles bradleyi and Culex salinarius were the most common species collected in larval habitats, and Ae. sollicitans was the most common adult collected. Wooded habitats had more total mosquitoes, were also more frequently occupied by mosquitoes and had higher densities of mosquitoes than marsh habitats. Almost all larvae collected from marshes were from one experimental and one control site. The majority of larvae at the control site were Ae. sollicitans in marsh pannes while Cx. salinarius, An. bradleyi, Ae. cantator, and Ae. sollicitans were collected in high numbers from ditches at the experimental site. We found a difference in the proportion of marsh pannes occupied by Ae. sollicitans but not total mosquitoes sampled 4–5 days after spring tide events than on other occasions. Salinity measures of 42 larval habitats showed lower median salinity in mosquito-occupied habitats (11.5 ppt) than unoccupied habitats (20.1 ppt), and in habitats in wooded areas followed by ditches and pannes in marsh areas. The results of this study suggest that wooded areas adjacent to salt marshes may be a substantial source of biting adult mosquitoes usually associated with salt marsh habitats and that ditch plugging may alter the productivity of mosquitoes on some marshes. We recommend future studies consider mosquito productivity from habitats surrounding salt marshes, and if assessments of marsh alterations are a goal, compare multiple experimental and control areas before and after treatments to determine if alterations have a consistent impact on regional mosquito production.
ditch plugging; Delmarva Peninsula; tidal salt marsh; restoration; salinity
Seagrass meadows are highly productive habitats that provide important ecosystem services in the coastal zone, including carbon and nutrient sequestration. Organic carbon in seagrass sediment, known as “blue carbon,” accumulates from both in situ production and sedimentation of particulate carbon from the water column. Using a large-scale restoration (>1700 ha) in the Virginia coastal bays as a model system, we evaluated the role of seagrass, Zosteramarina, restoration in carbon storage in sediments of shallow coastal ecosystems. Sediments of replicate seagrass meadows representing different age treatments (as time since seeding: 0, 4, and 10 years), were analyzed for % carbon, % nitrogen, bulk density, organic matter content, and 210Pb for dating at 1-cm increments to a depth of 10 cm. Sediment nutrient and organic content, and carbon accumulation rates were higher in 10-year seagrass meadows relative to 4-year and bare sediment. These differences were consistent with higher shoot density in the older meadow. Carbon accumulation rates determined for the 10-year restored seagrass meadows were 36.68 g C m-2 yr-1. Within 12 years of seeding, the restored seagrass meadows are expected to accumulate carbon at a rate that is comparable to measured ranges in natural seagrass meadows. This the first study to provide evidence of the potential of seagrass habitat restoration to enhance carbon sequestration in the coastal zone.
The present paper examines the functional diversity-environment relation in a placer rich tropical bay. Understanding the environmental variables that determine the biodiversity pattern will help in the effective conservation plans of coastal habitat. However, few studies have been carried out on the biodiversity-environment relation from the diverse tropical coastal ecosystem. The geographic location of Kalbadevi Bay along the west coast of India provides an opportunity to study the functional diversity pattern of macrofauna along an environmental gradient. Additionally, the area is also a potential placer mining site. Seasonal sampling was carried out for macrofauna and environmental variables. Macrofaunal functional diversity showed significant temporal variation related to the environmental parameters. The most important environmental variables were organic matter and sediment texture. Filter feeders dominated during postmonsoon which is a period when the water column is enriched with sinking detritus. The deposit feeders which rapidly ingest the settled detritus and also transport it to deeper sediment for the subsurface deposit feeders dominated during premonsoon. Abundance of carnivores was high during premonsoon, a response to increase in food in terms of deposit feeders. The result thus indicates that the temporal environmental variation influenced the macrofaunal functional diversity pattern in the Kalbadevi Bay.
Environmental mycobacteria are of increasing concern in terms of the diseases they cause in both humans and animals. Although they are considered to be ubiquitous in aquatic environments, few studies have examined their ecology, and no ecological studies of coastal marine systems have been conducted. This study uses indirect gradient analysis to illustrate the strong relationships that exists between coastal water quality and the abundance of Mycobacterium spp. within a U.S. mid-Atlantic embayment. Mycobacterium species abundance and water quality conditions (based on 16 physical and chemical variables) were examined simultaneously in monthly samples obtained at 18 Maryland and Virginia coastal bay stations from August 2005 to November 2006 (n = 212). A quantitative molecular assay for Mycobacterium spp. was evaluated and applied, allowing for rapid, direct enumeration. By using indirect gradient analysis (environmental principal-components analysis), a strong linkage between eutrophic conditions, characterized by low dissolved-oxygen levels and elevated nutrient concentrations, and mycobacteria was determined. More specifically, a strong nutrient response was noted, with all nitrogen components and turbidity measurements correlating positively with abundance (r values of >0.30; P values of <0.001), while dissolved oxygen showed a strong negative relationship (r = −0.38; P = 0.01). Logistic regression models developed using salinity, dissolved oxygen, and total nitrogen showed a high degree of concordance (83%). These results suggest that coastal restoration and management strategies designed to reduce eutrophication may also reduce total mycobacteria in coastal waters.
The objective is to identify the spatial and temporal variability of the hydrochemical quality of the water column in a subtropical coastal system, Daya Bay, China. Water samples were collected in four seasons at 12 monitoring sites. The Southeast Asian monsoons, northeasterly from October to the next April and southwesterly from May to September have also an important influence on water quality in Daya Bay. In the spatial pattern, two groups have been identified, with the help of multidimensional scaling analysis and cluster analysis. Cluster I consisted of the sites S3, S8, S10 and S11 in the west and north coastal parts of Daya Bay. Cluster I is mainly related to anthropogenic activities such as fish-farming. Cluster II consisted of the rest of the stations in the center, east and south parts of Daya Bay. Cluster II is mainly related to seawater exchange from South China Sea.
Daya Bay; principal component analysis; multidimensional scaling analysis; statistical techniques; water quality
Ammonia-oxidizing archaea (AOA) are widespread and abundant in aquatic and terrestrial habitats and appear to have a significant impact on the global nitrogen cycle. Like the ammonia-oxidizing bacteria, AOA encode a gene homologous to copper-containing nitrite reductases (nirK), which has been studied very little to date. In this study, the diversity, abundance and expression of thaumarchaeal nirK genes from coastal and marine environments were investigated using two mutually excluding primer pairs, which amplify the nirK variants designated as AnirKa and AnirKb. Only the AnirKa variant could be detected in sediment samples from San Francisco Bay and these sequences grouped with the nirK from Candidatus Nitrosopumilus maritimus and Candidatus Nitrosoarchaeum limnia. The two nirK variants had contrasting distributions in the water column in Monterey Bay and the California Current. AnirKa was more abundant in the epi- to mesopelagic Monterey Bay water column, whereas AnirKb was more abundant in the meso- to bathypelagic California Current water. The abundance and community composition of AnirKb, but not AnirKa, followed that of thaumarchaeal amoA, suggesting that either AnirKa is not exclusively associated with AOA or that commonly used amoA primers may be missing a significant fraction of AOA diversity in the epipelagic. Interestingly, thaumarchaeal nirK was expressed 10–100-fold more than amoA in Monterey Bay. Overall, this study provides valuable new insights into the distribution, diversity, abundance and expression of this alternative molecular marker for AOA in the ocean.
ammonia-oxidizing archaea; copper-containing nitrite reductase; Monterey Bay time series; nirK; thaumarchaea
Eelgrass beds in coastal waters of China have declined substantially over the past 30 years. In this study, a simple new transplanting technique was developed for eelgrass (Zostera marina L.) restoration. To assist in anchoring single shoots, several rhizomes of rooted shoots were bound to a small elongate stone (50–150 g) with biodegradable thread (cotton or hemp), and then the bound packet was buried at an angle in the sediments at a depth of 2–4 cm. This stone anchoring method was used to transplant eelgrass in early November 2009 and late May 2010 in Huiquan Bay, Qingdao. The method led to high success. Three month survivorship of the transplanted shoots at the two transplant sites was >95%. From April 20 to November 19, 2012, the following characteristics of the 2009 and 2010 transplanted eelgrass beds were monitored: morphological changes, shoot density, shoot height, leaf biomass, and sediment particle size. Results showed that the sexual reproduction period of the planted eelgrass was from April to August, and vegetative reproduction reached its peak in autumn. Maximum shoot height and biomass were observed in June and July. After becoming established, the transplanted eelgrass beds were statistically equal to natural eelgrass beds nearby in terms of shoot height, biomass, and seasonal variations. This indicates that the transplant technique is effective for eelgrass restoration in coastal waters.
The aim of this study was to initiate autecological studies on uncultivated natural populations of diazotrophic bacteria by examining the distribution of specific diazotrophs in the Chesapeake Bay. By use of quantitative PCR, the abundance of two nifH sequences (907h22 and 912h4) was quantified in water samples collected along a transect from the head to the mouth of the Chesapeake Bay during cruises in April and October 2001 and 2002. Standard curves for the quantitative PCR assays demonstrated that the relationship between gene copies and cycle threshold was linear and highly reproducible from 1 to 107 gene copies. The maximum number of 907h22 gene copies detected was approximately 140 ml−1 and the maximum number of 912h4 gene copies detected was approximately 340 ml−1. Sequence 912h4 was most abundant at the mouth of the Chesapeake Bay, and in general, its abundance increased with increasing salinity, with the highest abundances observed in April 2002. Overall, the 907h22 phylotype was most abundant at the mid-bay station. Additionally, 907h22 was most abundant in the April samples from the mid-bay and mouth of the Chesapeake Bay. Despite the fact that the Chesapeake Bay is rarely nitrogen limited, our results show that individual nitrogen-fixing bacteria have distinct nonrandom spatial and seasonal distributions in the Chesapeake Bay and are either distributed by specific physical processes or adapted to different environmental niches.
The sister phyla dinoflagellates and apicomplexans inherited a drastically reduced mitochondrial genome (mitochondrial DNA, mtDNA) containing only three protein-coding (cob, cox1, and cox3) genes and two ribosomal RNA (rRNA) genes. In apicomplexans, single copies of these genes are encoded on the smallest known mtDNA chromosome (6 kb). In dinoflagellates, however, the genome has undergone further substantial modifications, including massive genome amplification and recombination resulting in multiple copies of each gene and gene fragments linked in numerous combinations. Furthermore, protein-encoding genes have lost standard stop codons, trans-splicing of messenger RNAs (mRNAs) is required to generate complete cox3 transcripts, and extensive RNA editing recodes most genes. From taxa investigated to date, it is unclear when many of these unusual dinoflagellate mtDNA characters evolved. To address this question, we investigated the mitochondrial genome and transcriptome character states of the deep branching dinoflagellate Hematodinium sp. Genomic data show that like later-branching dinoflagellates Hematodinium sp. also contains an inflated, heavily recombined genome of multicopy genes and gene fragments. Although stop codons are also lacking for cox1 and cob, cox3 still encodes a conventional stop codon. Extensive editing of mRNAs also occurs in Hematodinium sp. The mtDNA of basal dinoflagellate Hematodinium sp. indicates that much of the mtDNA modification in dinoflagellates occurred early in this lineage, including genome amplification and recombination, and decreased use of standard stop codons. Trans-splicing, on the other hand, occurred after Hematodinium sp. diverged. Only RNA editing presents a nonlinear pattern of evolution in dinoflagellates as this process occurs in Hematodinium sp. but is absent in some later-branching taxa indicating that this process was either lost in some lineages or developed more than once during the evolution of the highly unusual dinoflagellate mtDNA.
mitochondrion; Apicomplexa; RNA editing; organelle genome
A Bay-wide survey of the distribution of Vibrio parahaemolyticus was carried out in Chesapeake Bay during May 1972, to determine whether the annual cycle of V. parahaemolyticus which was observed to occur in the Rhode River subestuary of Chesapeake Bay took place in other parts of Chesapeake Bay. In an earlier study, April to early June, when the water temperature rises from 14 to 19 C, was found to be a critical period in the annual cycle of the organism in the Rhode River, since this is the time period when the annual cycle is initiated. Results of this study, however, revealed that V. parahaemolyticus could not be found in the water column during May 1972. Neverthless, several samples of sediment and plankton yielded V. parahaemolyticus isolates. Comparison of data with those for the Rhode River area examined in the earlier studies of the annual cycle of V. parahaemolyticus suggests that the time of initiation of the annual cycle of V. parahaemolyticus in the open Bay proper may be influenced by various factors such as temperature and salinity, i.e., deeper water locations may show initiation of the V. parahaemolyticus annual cycle later than shallow areas. Confirmation of the presence of the organism in the samples studied was accomplished using numerical taxonomy with 19 reference strains also included in the analyses.
A study of the ecology of Vibrio parahaemolyticus and related vibrios in the Rhode River area of Chesapeake Bay was carried out over the period December 1970 through August 1971. The incidence of V. parahaemolyticus and related vibrios was found to be correlated with water temperature. The vibrios could not be detected in the water column during the winter months, although they were present in sediment. From late spring to early summer, when water temperatures were 14 ± 1 C, vibrios over-wintering in sediment were released from the bottom communities and attached to zooplankton, proliferating as the temperature rose. The number of vibrios in and on plankton was reflected in the water column bacterial population densities at water temperatures of ca. 19 C. Thus, temperature of the water column in the range of 14 to 19 C was found to be critical in the annual cycle of the vibrios. Interaction between sediment, water, and zooplankton was found to be essential in the natural estuarine ecosystem. Bacterial counts of zooplankton were found to be temperature dependent. The bacterial population associated with zooplankton was found to be predominantly on external surfaces and was specific, differing from that of the sediment. Vibrio spp. and related organisms comprised the total bacterial population associated with zooplankton in summer months. The ecological role of Vibrio spp., including V. parahaemolyticus, was found to be significant, with respect to their property of chitin digestion and in relation to the population dynamics of zooplankton in Chesapeake Bay.
We compared the detection of bacteria and archaea in the coastal North Sea and at Monterey Bay, Calif., after fluorescence in situ hybridization (FISH) either with rRNA-targeted oligonucleotide probes monolabeled with the cyanin dye Cy3 (oligoFISH) or with fluorescein-labeled polyribonucleotide probes (polyFISH). During an annual cycle in German Bight surface waters, the percentages of bacteria visualized by polyFISH (annual mean, 77% of total counts) were significantly higher than those detected by oligoFISH (53%). The fraction of total bacteria visualized by oligoFISH declined during winter, whereas cell numbers determined by polyFISH remained constant throughout the year. Depth profiles from Monterey Bay showed large differences in the fraction of bacterial cells visualized by polyFISH and oligoFISH in the deeper water layers irrespective of the season. Image-analyzed microscopy indicated that the superior detection of cells by polyFISH with fluorescein-labeled probes in bacterioplankton samples was less a consequence of higher absolute fluorescence intensities but was rather related to quasi-linear bleaching dynamics and to a higher signal-to-background ratio. The relative abundances of archaea in North Sea and Monterey Bay spring samples as determined by oligoFISH were on average higher than those determined by polyFISH. However, simultaneous hybridizations with oligonucleotide probes for bacteria and archaea suggested that the oligoFISH probe ARCH915 unspecifically stained a population of bacteria. Using either FISH technique, blooms of archaea were observed in North Sea surface waters during the spring and summer months. Marine group II archaea (Euryarchaeota) reached >30% of total picoplankton abundances, as determined by polyFISH. We suggest that studies of pelagic microbial community structure using oligoFISH with monolabeled probes should focus on environments that yield detections ≥70% of total cell counts, e.g., coastal surface waters during spring and summer.
Recent studies have shown that the fecal indicator bacteria (FIB) currently used to indicate water quality in the coastal environment may be inadequate to reflect human viral contamination. Coliphage was suggested as a better indicator of human viral pollution and was proposed by the U.S. EPA as an alternative indicator for fecal pollution in groundwater. In this study, we investigated the occurrence and distribution of FIB, F+ coliphage, and PCR-detectable human adenovirus and enterovirus for an entire year at 15 locations around the Newport Bay watershed, an important southern California estuary for water recreation and an ecological reserve. Peak concentrations and prevalences of FIB and F+ coliphage were associated with winter storms (wet weather). Human adenoviruses and enteroviruses, however, were detected by PCR in ∼5% of samples collected in the summer (dry weather) but only once in wet weather. These results demonstrated that FIB and coliphage have similar seasonal and freshwater-to-saltwater distribution patterns, while the detection of human viruses depends on a distribution pattern that is the opposite of that of FIB and coliphage. This research suggested that coliphage and FIB share similar environmental sources, while sources of human viruses in Newport Bay are perhaps different.
The distribution of viral and microbial abundance in the Key Largo, Fla., reef environment was measured. Viral abundance was measured by transmission electron microscope direct counts and plaque titer on specific bacterial hosts in water and sediment samples from Florida Bay (Blackwater Sound) and along a transect from Key Largo to the outer edge of the reef tract in Key Largo Sanctuary. Water column viral direct counts were highest in Blackwater Sound of Florida Bay (1.2 x 10(7) viruses per ml), decreased to the shelf break (1.7 x 10(6) viruses per ml), and were inversely correlated with salinity (r = -0.97). Viral direct counts in sediment samples ranged from 1.35 x 10(8) to 5.3 x 10(8)/cm(3) of sediment and averaged nearly 2 orders of magnitude greater than counts in the water column. Viral direct counts (both sediment and water column measurements) exceeded plaque titers on marine bacterial hosts (Vibrio natriegens and others) by 7 to 8 orders of magnitude. Water column viral abundance did not correlate with bacterial direct counts or chlorophyll a measurements, and sediment viral parameters did not correlate with water column microbial, viral, or salinity data. Coliphage, which are indicators of fecal pollution, were detected in two water column samples and most sediment samples, yet their concentrations were relatively low (<2 to 15/liter for water column samples, and <2 to 108/cm(3) of sediment). Our findings indicate that viruses are abundant in the Key Largo environment, particularly on the Florida Bay side of Key Largo, and that processes governing their distribution in the water column (i.e., salinity and freshwater input) are independent of those governing their distribution in the sediment environment.
Bacteria were readily isolated from the hemolymph of a majority (88%) of the blue crabs collected from Galveston Bay, Texas. The hemolymph of most crabs contained moderate (greater than 10(3) bacteria/ml) to heavy (greater than (10(5) bacteria/ml) infections. Large variances were observed in the bacterial number associated with individual crabs, but no significant difference was observed between the mean bacterial levels in the hemolymph of crabs collected during different seasons of the sampling year. Vibrio spp. were the predominant bacterial types in the hemolymph of infected crabs and increased in number significantly during the summer season. Warmer water temperatures were thought to be responsible for this increase. Bacterial numbers and the percentage of Vibrio spp. were highest in the interior of the crab bodies, especially in the digestive tract. The exterior of the crabs did not appear to be the source of the hemolymph's bacterial flora. Bacteria taxonomically identical to Vibrio cholerae. V. vulnificus, and V. parahaemolyticus were routinely isolated from the crab hemolymph and external carapace. V. parahaemolyticus was the most prevalent of the pathogenic Vibrio spp. and was isolated from 23% of the hemolymph samples. V. vulnificus (7%) and V. cholerae (2%) occurred less commonly in the hemolymph. The incidences of V. parachaemolyticus and V. vulnificus were related and increased in the summer months. Both organisms were frequently isolated from the same crab.
Grand Bay National Estuarine Research Reserve (NERR) is an important ecosystem in the Mississippi Gulf Coast. It serves as important nursery areas for juveniles of many species of fish. The bay is also used for fishing, crabbing, oyster togging, boating as well as recreation. Like in other aquatic environments, this bay may be contaminated by microorganisms including pathogenic bacteria. The objective of this study was to evaluate the microbiological quality of water in the Grand Bay NERR and determine the levels and potential source(s) of human fecal pollution. To achieve this goal, water samples were collected aseptically every month in Bayou Heron, Bayou Cumbest, Point Aux Chenes Bay and Bangs Lake. Enterococci were concentrated from water samples by membrane filtration according to the methodology outlined in USEPA Method 1600. After incubation, DNA was extracted from bacteria colonies on the membrane filters by using QIAamp DNA extraction kit. Water samples were also tested for the presence of traditional indicator bacteria including: heterotrophic plate count, total coliforms, fecal coliforms, and Enterococcus bacteria. The marker esp gene was detected in one site of Bayou Cumbest, an area where human populations reside. Data from this study indicates higher concentrations of indicator bacteria compared to the recommended acceptable levels. Presence of esp marker and high numbers of indicator bacteria suggest a public health concern for shellfish and water contact activities. Hence, control strategies should be developed and implemented to prevent further contamination of the Grand bay NERR waters.
Grand Bay NERR; recreation; molecular probing; esp gene; bacteria; public health
Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D coupled physical/biogeochemical model was developed. Two versions of the biogeochemical model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period of 5 years (2007–2011). The model accuracy assessment showed that both versions of the model were able of capturing the seasonal changes and spatial characteristics of the ecosystem. The model also reproduced upwelling events and the intrusion of Rhone River water into the Bay of Marseille well. Those processes appeared to greatly impact this coastal oligotrophic area because they induced strong increases in chlorophyll-a concentrations in the surface layer. The model with the C, N and P cycles better reproduced the chlorophyll-a concentrations at the surface than did the model without the P cycle, especially for the Rhone River water. Nevertheless, the chlorophyll-a concentrations at depth were better represented by the model without the P cycle. Therefore, the complexity of the biogeochemical model introduced errors into the model results, but it also improved model results during specific events. Finally, this study suggested that in coastal oligotrophic areas, improvements in the description and quantification of the hydrodynamics and the terrestrial inputs should be preferred over increasing the complexity of the biogeochemical model.
Pfiesteria piscicida is a heterotrophic dinoflagellate widely distributed along the middle Atlantic shore of the United States and associated with fish kills in the Neuse River (North Carolina) and the Chesapeake Bay (Maryland and Virginia). We constructed a genomic DNA library from clonally cultured P. piscicida and characterized the nontranscribed spacer (NTS), small subunit, internal transcribed spacer 1 (ITS1), 5.8S region, ITS2, and large subunit of the rRNA gene cluster. Based on the P. piscicida ribosomal DNA sequence, we developed a PCR-based detection assay that targets the NTS. The assay specificity was assessed by testing clonal P. piscicida and Pfiesteria shumwayae, 35 additional dinoflagellate species, and algal prey (Rhodomonas sp.). Only P. piscicida and nine presumptive P. piscicida isolates tested positive. All PCR-positive products yielded identical sequences for P. piscicida, suggesting that the PCR-based assay is species specific. The assay can detect a single P. piscicida zoospore in 1 ml of water, 10 resting cysts in 1 g of sediment, or 10 fg of P. piscicida DNA in 1 μg of heterologous DNA. An internal standard for the PCR assay was constructed to identify potential false-negative results in testing of environmental sediment and water samples and as a competitor for the development of a quantitative competitive PCR assay format. The specificities of both qualitative and quantitative PCR assay formats were validated with >200 environmental samples, and the assays provide simple, rapid, and accurate methods for the assessment of P. piscicida in water and sediments.