Successive mapping of dune slack vegetation

Summary The succession of the dune slack vegetation around an artificial lake was studied by means of successive mapping. A succession scheme was prepared on the basis of comparison of the maps made in various years. This scheme was discussed in terms of systems theory, with reference to a kinematic graph prepared on the basis of the transformations. The succession derived from the vegetation maps was compared with that derived from the permanent plots; the results of this comparison indicated that only a small proportion of the total number of succession lines could be detected with the aid of the permanent plots. In addition, the information that could be derived from the permanent plot analysis depended on the degree of change of the vegetation in the area; more information could be derived from drier areas which showed the least degree of change. The best method for the investigation of the succession proved to be a combination of a restricted number of permanent plots and successive mapping. Nomenclature of species follows Heukels-van Ooststroom Flora van Nederland, 16 ed. 1970. R.I.N.-Comm. nr. 107.     

Responses of periphyton to artificial nutrient enrichment in freshwater kettle ponds of Cape Cod National Seashore

Nutrient enrichment bioassays, in conjunction with sampling and analysis of surface water chemistry, were conducted in freshwater lakes (kettle ponds) of Cape Cod National Seashore (Massachusetts, USA) to ascertain the importance of nitrogen (N) and phosphorus (P) in regulating the growth of periphyton. Arrays of nutrient diffusing substrata (NDS) were suspended 0.5 m below the water surface in a total of 12 ponds in July and August 2005. Algal biomass developing on each NDS after ~3 weeks of exposure in each month was assessed by quantifying chlorophyll a + phaeophyton pigments. In both July and August, strong responses to N + P and N enrichments were observed in the majority of ponds, while P had no stimulatory effect. These responses correspond well with low atomic ratios (1–18) of dissolved inorganic nitrogen (DIN) to total phosphorus (TP) in ambient surface waters. The results suggest that conditions in the kettle ponds develop whereby nitrogen is the primary limiting nutrient to periphyton growth. While this may be a seasonal phenomenon, it has implications for nutrient management in individual ponds and within the larger watershed.     

Biological Soil Crusts of Sand Dunes in Cape Cod National Seashore,Massachusetts, USA

Biological soil crusts cover hundreds of hectares of sand dunes at the northern tip of Cape Cod National Seashore (Massachusetts, USA). Although the presence of crusts in this habitat has long been recognized, neither the organisms nor their ecological roles have been described. In this study, we report on the microbial community composition of crusts from this region and describe several of their physical and chemical attributes that bear on their environmental role. Microscopic and molecular analyses revealed that eukaryotic green algae belonging to the genera Klebsormidium or Geminella formed the bulk of the material sampled. Phylogenetic reconstruction of partial 16S rDNA sequences obtained from denaturing gradient gel electrophoresis (DGGE) fingerprints also revealed the presence of bacterial populations related to the subclass of the Proteobacteria, the newly described phylum Geothrix/Holophaga/Acidobacterium, the Cytophaga/Flavobacterium/Bacteroides group, and spirochetes. The presence of these crusts had significant effects on the hydric properties and nutrient status of the natural substrate. Although biological soil crusts are known to occur in dune environments around the world, this study enhances our knowledge of their geographic distribution and suggests a potential ecological role for crust communities in this landscape.This revised version was published online in November 2004 with corrections to Volume 48.     

Aquatic vegetation and trophic condition of Cape Cod (Massachusetts,U.S.A.) kettle ponds

The species composition and relative abundance of aquatic macrophytes was evaluated in five Cape Cod, Massachusetts, freshwater kettle ponds, representing a range of trophic conditions from oligotrophic to eutrophic. At each pond, aquatic vegetation and environmental variables (slope, water depth, sediment bulk density, sediment grain size, sediment organic content and porewater inorganic nutrients) were measured along five transects extending perpendicular to the shoreline from the upland border into the pond. Based on a variety of multivariate methods, including Detrended Correspondence Analysis (DCA), an indirect gradient analysis technique, and Canonical Correspondence Analysis (CCA), a direct gradient approach, it was determined that the eutrophic Herring Pond was dominated by floating aquatic vegetation (Brasenia schreberi, Nymphoides cordata, Nymphaea odorata), and the algal stonewort, Nitella. Partial CCA suggested that high porewater PO₄-P concentrations and fine-grained sediments strongly influenced the vegetation of this eutrophic pond. In contrast, vegetation of the oligotrophic Duck Pond was sparse, contained no floating aquatics, and was dominated by emergent plants. Low porewater nutrients, low sediment organic content, high water clarity and low pH (4.8) best defined the environmental characteristics of this oligotrophic pond. Gull Pond, with inorganic nitrogen-enriched sediments, also exhibited a flora quite different from the oligotrophic Duck Pond. The species composition and relative abundance of aquatic macrophytes provide good indicators of the trophic status of freshwater ponds and should be incorporated into long-term monitoring programs aimed at detecting responses to anthropogenically-derived nutrient loading.     

A comparison of seed banks across a sand dune successional gradient at Lake Michigan dunes (Indiana,USA)

In habitats where disturbance is frequent, seed banks are important for the regeneration of vegetation. Sand dune systems are dynamic habitats in which sand movement provides intermittent disturbance. As succession proceeds from bare sand to forest, the disturbance decreases. At Indiana Dunes National Lakeshore, we examined the seed banks of three habitat types across a successional gradient: foredunes, secondary dunes, and oak savanna. There were differences among the types of species that germinated from each of the habitats. The mean seed bank density increased across the successional gradient by habitat, from 376 to 433 to 968 seeds m⁻², but with foredune and secondary dune seed bank densities being significantly lower than the savanna seed bank density. The number of seeds germinated was significantly correlated with soil organic carbon, demonstrating for this primary successional sequence that seed density increases with stage and age. The seed bank had much lower species richness than that of the aboveground vegetation across all habitats. Among sites within a habitat type, the similarity of species germinated from the seed banks was very low, illustrating the variability of the seed bank even in similar habitat types. These results suggest that restoration of these habitats cannot rely on seed banks alone.     

Relationship between DOC concentration and vadose zone thickness and depth below water table in groundwater of Cape Cod, U.S.A.

Changes in concentration ofdissolved organic carbon (DOC) reflectbiogeochemical processes that determinechemical composition of groundwater and othernatural waters. We found that the deeper thevadose zone, the lower the concentration of DOCin groundwater near the water table, indicatingthat considerable attenuation ofsurface-derived DOC occurred in the vadosezone. Under vadose zones <1.25 m, DOCconcentrations at the surface of the watertable ranged to >20 mg C l^–1, while forvadose zones >5.0 m, DOC never exceeded2.0 mg C l^–1. DOC concentrations alsodecreased exponentially with increasing depthbelow the water table, most notably in theupper two meters, implying continuedattenuation in the upper layer of the saturatedzone. Ninety-nine percent of the DOC wasattenuated by the time the water reached adepth of 19 m below the water table. A stronginverse relationship between DOC and nitrateconcentrations suggests that nitrate isdepleted where DOC supplies are high, providingevidence that some portion of the DOC losses ingroundwater are due to microbialtransformations, including denitrification. DOC concentrations in shallow groundwater showconsiderable spatial variability, butconcentration of DOC at any one site issurprisingly stable over time. The largestsource of variation in DOC concentration ingroundwater therefore is spatial rather thantemporal, suggesting that local heterogeneitiesplay an important role in DOC delivery toshallow groundwater. Our results highlightboth the importance of shallow vadose areas inDOC delivery to groundwater and the need todistinguish where samples are collected inrelation to flow paths before conclusions aremade about mean groundwater DOC concentrations. The substantial losses of DOC in the vadosezone and in shallow depths within the aquifersuggest quite active biogeochemical processesin these boundary environments.     

Dynamics of Alexandrium fundyense blooms and shellfish toxicity in the Nauset Marsh System of Cape Cod (Massachusetts,USA)

Paralytic Shellfish Poisoning (PSP) toxins are annually recurrent along the Massachusetts coastline (USA), which includes many small embayments and salt ponds. Among these is the Nauset Marsh System (NMS), which has a long history of PSP toxicity. Little is known, however, about the bloom dynamics of the causative organism Alexandrium fundyense within that economically and socially important system. The overall goal of this work was to characterize the distribution and dynamics of A. fundyense blooms within the NMS and adjacent coastal waters by documenting the distribution and abundance of resting cysts and vegetative cells. Cysts were found predominantly in three drowned kettle holes or salt ponds at the distal ends of the NMS – Salt Pond, Mill Pond, and Town Cove. The central region of the NMS had a much lower concentration of cysts. Two types of A. fundyense blooms were observed. One originated entirely within the estuary, seeded by cysts in the three seedbeds. These blooms developed independently of each other and of the A. fundyense population observed in adjacent coastal waters outside the NMS. The temporal development of the blooms was different in the three salt ponds, with initiation differing by as much as 30 days. These differences do not appear to reflect the initial cyst abundances in these locations, and may simply result from higher cell retention and higher nutrient concentrations in Mill Pond, the first site to bloom. Germination of cysts accounted for a small percentage of the peak cell densities in the ponds, so population size was influenced more by the factors affecting growth than by cyst abundance. Subsurface cell aggregation (surface avoidance) limited advection of the vegetative A. fundyense cells out of the salt ponds through the shallow inlet channels. Thus, the upper reaches of the NMS are at the greatest risk for PSP since the highest cyst abundances and cell concentrations were found there. After these localized blooms in the salt ponds peaked and declined, a second, late season bloom occurred within the central portions of the NMS. The timing of this second bloom relative to those within the salt ponds and the coastal circulation patterns at that time strongly suggest that those cells originated from a regional A. fundyense bloom in the Gulf of Maine, delivered to the central marsh from coastal waters outside the NMS through Nauset Inlet. These results will guide policy decisions about water quality as well as shellfish monitoring and utilization within the NMS and highlight the potential for “surgical” closures of shellfish during PSP events, leaving some areas open for harvesting while others are closed.     

Spondylitic changes in long-finned pilot whales (Globicephala melas) stranded on Cape Cod, Massachusetts, USA, between 1982 and 2000

The primary bone pathology diagnoses recognized in cetacea are osteomyelitis and spondylosis deformans. In this study, we determined the prevalence, type, and severity of vertebral pathology in 52 pilot whales, a mass stranding species that stranded on Cape Cod, Massachusetts, between 1982 and 2000. Eleven whales (21%) had hyperostosis and ossification of tendon insertion points on and between vertebrae, chevron bones, and costovertebral joints, with multiple fused blocks of vertebrae. These lesions are typical of a group of interrelated diseases described in humans as spondyloarthropathies, specifically ankylosing spondylitis, which has not been fully described in cetacea. In severe cases, ankylosing spondylitis in humans can inhibit mobility. If the lesions described here negatively affect the overall health of the whale, these lesions may be a contributing factor in stranding of this highly sociable species.     

A comparison of postrelease survival parameters between single and mass stranded delphinids from Cape Cod,Massachusetts, U.S.A.

The viability of healthy single stranded dolphins as immediate release candidates has received little attention. Responders have been reluctant to release lone delphinids due to their social needs, even when they pass the same health evaluations as mass stranded animals. This study tracked postrelease success of 34 relocated and released satellite tagged delphinids from single and mass strandings. Three postrelease survival parameters (transmission duration, swim speed, and daily distance) were examined to evaluate whether they differed among single stranded/single released (SS/SR), mass stranded/single released (MS/SR), or mass stranded/mass released (MS/MR) dolphin groups. Comparisons were also made between healthy and borderline release candidates. Satellite tags transmitted for a mean of 21.2 d (SD = 19.2, range = 1–79), daily distance traveled was 42.0 km/d (11.25, 20.96–70.72), and swim speed was 4.3 km/h (1.1, 2.15–8.54). Postrelease parameters did not differ between health status groups, however, SS/SR dolphins transmitted for a shorter mean duration than MS/MR and MS/SR groups. Postrelease vessel‐based surveys confirmed conspecific group location for two healthy, MS/SR dolphins. Overall, these results support the potential to release healthy stranded single delphinids; however, further refinement of health assessment protocols for these challenging cases is needed.     

Effects of mud fiddler crabs (Uca pugnax) on the recruitment of halophyte seedlings in salt marsh dieback areas of Cape Cod (Massachusetts, USA)

The effects of bioturbation by the mud fiddler crab (Uca pugnax) on salt marsh seedling recruitment were investigated experimentally in this study. Burrowing and foraging activity caused a large amount of soil disturbance, which in turn negatively impacted the establishment of seedlings. Either seeds did not germinate or seedlings were uprooted or buried. Although the majority of the published literature suggests a positive influence of Uca spp. on salt marsh plant growth, at high densities they have the potential to hinder the re-colonization of areas made bare by previous disturbance. This study illustrates the perhaps underappreciated role that bioturbators can have on vegetation patterns in salt marshes and other ecosystems.     

Determining discharges from the Table Mountain Group (TMG) aquifer to wetlands in the Southern Cape, South Africa

The focus of this study was to determine whether coastal wetlands in lowland settings could be dependent on groundwater from the deep circulating confined Table Mountain Group (TMG) aquifer. Groundwater interactions with wetlands are normally perceived to be limited to primary aquifers. A comparative study was done between two endorheic coastal wetlands in the southern Cape. Earlier reports stated that these groundwater dependent wetlands were fed by discharges from the fixed dunes surrounding them. On the basis of a three-dimensional electrical conductivity (EC) interpolation for Groenvlei, a hydrological link between the TMG aquifer and Groenvlei and Van Kervelsvlei was investigated by measuring water level and quality of groundwater and surface water. Water quality parameters used were EC, pH, Na⁺, Fe²⁺ and Cl⁻. The results from this, and an accompanying study, on the basis of water quality and plant nutrient cycling assessments, indicated direct groundwater discharges from the TMG to at least Van Kervelsvlei, with Groenvlei receiving secondary discharges from the TMG via Van Kervelslvlei. These findings significantly affect the current knowledge on which water balance models are based for the determination of groundwater availability for the area. Handling editor: D. Hamilton The first author did the research as part of his PhD in the Department of Earth Sciences of the University of the Western Cape, Bellville, South Africa. Funding is quoted under acknowledgements.     

Seasonal movement of the American horseshoe crab Limulus polyphemus in a semi-enclosed bay on Cape Cod,Massachusetts (USA) as determined by acoustic telemetry

<正> American horseshoe crabs Limulus polyphemus were tracked using acoustic telemetry and traditional tagging in asemi-enclosed bay on Cape Cod (Pleasant Bay),Massachusetts,USA,to determine seasonal movement patterns.Fifty-five activelyspawning females were fitted with transmitters in 2008 and 2009 and were tracked using acoustic telemetry from May 2008through July 2010.Fifteen crabs with transmitters also had archive depth-temperature tags attached.In addition,over 2000spawning crabs (males and females) were tagged with US Fish and Wildlife (USFWS) button tags over the same period.Ninety-one percent of the crabs with transmitters were detected during this study.In the spring,crabs were primarily located inthe northern section of the bay near spawning beaches,whereas in the fall crabs moved towards the deeper portions of the bay,and some may have overwintered in the bay.There was evidence that a majority (58%-71%) of the females with transmittersspawned in two sequential seasons.One archive tag was recovered resulting in a year-long continuous record of depth and temperaturedata that,when integrated with telemetry data,indicated that the crab overwintered in the bay.The live recapture rate ofcrabs with USFWS button tags was 11%,with all re-sighted crabs except one observed inside Pleasant Bay.Eighty-three percentof recaptures were found within 2.5km of the tagging location,and 51% were observed at the same beach where they were tagged.This study provides further evidence that horseshoe crabs in Pleasant Bay may be philopatric to this embayment     

Overwintering habitat selection by the mummichog, Fundulus Heteroclitus, in a Cape Cod (USA) salt marsh

This study tracked the seasonal distribution and winter habitat selection of the mummichog, Fundulus heteroclitus (Linnaeus), in a Cape Cod, Massachusetts salt marsh. Fish (mean size = 43.1 mm total length, range = 10–93 mm) were collected with a 1 m² throw trap and by excavating sediments. In fall, F. heteroclitus began migrating upstream in creeks and eventually moved into upstream pools where they remained throughout winter. F. heteroclitus burrowed into the sediments of these pools at a density of 0.5 fish m^–2, but was not found burrowed in the sediments of downstream pools or any creeks. Sediments in upstream pools were composed of a higher proportion of fine-grained particles and organic content than other marsh pools and creeks, and winter temperatures in upstream pool sediments remained above 1 °C. Temperatures in the water column and sediments of downstream pools regularly dropped below –1.8 °C, exceeding the lethal limit for F. heteroclitus. These results support other recent work showing that F. heteroclitus migrates upstream in salt marshes in fall and overwinters in salt marsh pools. Moreover, this study demonstrates that F. heteroclitus does not utilize all available pools as overwintering habitat but apparently selects pools with sediments that offer a thermal refuge from lethal winter temperatures.     

An inventory of 13C abundances in coastal wetlands of Louisiana,USA: vegetation and sediments

Summary Organic carbon-rich sediments from the surface of fresh, intermediate, brackish and salt marshes of coastal Louisiana were sampled and analyzed for their ¹³C content. The average ¹³C from all sites within each wetland type was-27.8,-22.1,-16.9, and-16.2, for fresh, intermediate, brackish and salt marshes, respectively. Means from the fresh, intermediate and brackish marshes were significantly different at the 0.01 level. A mixing model using measurements of standing crop and ¹³C of plant carbon was applied to estimate the contribution of each species to the sedimentary carbon at four of the marsh sites. Sedimentary ¹³C values generally reflected that of the dominant species present at each site. Brackish and salt marsh samples, however, showed a negative shift of ¹³C with respect to whole plant carbon. We interpret these depeleted ¹³C values to be the result of more extensive organic matter decomposition and selective preservation of ¹³C-depleted refractory components in sediments from saline sites. The results of this study suggest that ¹³C composition of sedimentary carbon may offer a valuable tool for distinguishing subtle changes in paleohydrology of wetlands resulting from relative sea level changes.     

Comparison of created and natural freshwater emergent wetlands in Connecticut (USA)

Five three- to four-year old created palustrine/emergent wetland sites were compared with five nearby natural wetlands of comparable size and type. Hydrologic, soil and vegetation data were compiled over a nearly two-year period (1988-90). Created sites, which were located along major highways, exhibited more open water, greater water depth, and greater fluctuation in water depth than natural wetlands. Typical wetland soils exhibiting mottling and organic accumulation were wanting in created sites as compared with natural sites. Typha latifolia (common cattail) was the characteristic emergent vegetation at created sites, whereas a more diverse mosaic of emergent wetland species was often associated with Typha at the natural sites. Species richness was slightly higher in created (22–45) vs. natural (20–39) wetlands, but the mean difference (33 vs. 30) was not significant. Nearly half (44%) of the 54 wetland taxa found at the various study sites were more frequently recorded at created than natural wetlands. The presence of mycorrhizae in roots of Typha angustifolia (narrow-leaved cattail) and Phragmites australis (common reed) was greater at created than natural wetlands, which may be related to differential nutrient availability. Wildlife use at all sites ranged from occasional to rare, with more sightings of different species in the natural (39) than created (29) wetlands. The presence of P. australis and introduced Lythrum salicaria (purple loosestrife) may pose a threat to future species richness at the created sites. One created site has permanent flow-through hydrology, and its vegetation and wildlife somewhat mimic a natural wetland; however, the presence of P. australis and its potential spread pose an uncertain future for this site. This study suggests the possibility of creating small palustrine/emergent wetlands having certain functions associated with natural wetlands, such as flood water storage, sediment accretion and wildlife habitat. It is premature to evaluate fully the outcome of these wetland creation efforts. A decade or more is needed, emphasizing the importance of long term monitoring and the need to establish demonstration areas.     

Responses of Plant Communities to Incremental Hydrologic Restoration of a Tide-Restricted Salt Marsh in Southern New England (Massachusetts, U.S.A.)

Hydrologic restoration of Hatches Harbor, a tide-restricted marsh on Cape Cod (Massachusetts), has resulted in significant plant community changes 7 years following the reintroduction of seawater. Since 1999, incremental increases in flow through a tide-restricting dike have facilitated the rapid decline of salt-intolerant vegetation, while encouraging the expansion of native salt marsh taxa. These changes show strong spatial gradients and are correlated with marsh surface elevation, distance from the point of seawater entry, and porewater salinity. Common reed ( Phragmites australis ) has not decreased in abundance but has migrated a considerable distance upslope. In the wake of this retreat native halophytes have proliferated. Now that maximum flow through the existing dike structure has been reached, continued recovery may be limited less by changing physicochemical conditions and more by rates of growth, seed dispersal, and seed germination of salt marsh taxa.     

Effects of seasonal flooding and grazing on the vegetation of former ricefields in the Rhône delta (Southern France)

Six management regimes were tested during 5 years in 18 abandoned ricefields in the Rh^one delta, France: two artificial floodings for 6 months (winter and summer flooding, 10 cm deep) and a control only flooded by rain, each flooding treatment either with or without grazing by cattle and horses. In the absence of artificial flooding and in presence of grazing by domestic herbivores (i.e., maintaining the initial management since the abandonment) no significant change in plant communities was recorded after 5 years. The vegetation was mainly composed of halophytes (Salicornia fruticosa and Inula crithmoides). The removal of grazing led to the dominance of a salt tolerant grass: Aeluropus littoralis. Flooding favoured the dominance of clonal plants and led to a decrease in the number of species. In the ungrazed fields, changes in plant communities were related to the height of species with Bolboschoenus maritimus and Phragmites australis becoming dominant. When grazing was combined with summer flooding, B. maritimus dominated the first two years of the experiment, but with a low cover, and was replaced in the 3rd year by Typha angustifolia. When grazing was combined with winter and early spring flooding the competitive exclusion of B. maritimus by Juncus gerardii slowed the establishment of the former. The management of former ricefields led to the establishment and dominance of emergent species common to Mediterranean wetlands. Although it is subordinate to the maintenance of artificial flooding, the project may be considered a restoration (or a rehabilitation) of seasonally flooded marshes as original functions existing before the land was put under cultivation are re-established.     

Impacts of section 404 permits requiring compensatory mitigation on wetlands in California (USA)

We analyzed data from Section 404 permits issued in California from January 1971 through November 1987 that involved impacts to wetlands and required compensatory mitigation (wetland creation, restoration, or preservation). The purpose of this study was to determine patterns and trends in permitting activity and to document cumulative effects of associated management decisions on the California wetland resource. The 324 permits examined documented that 387 compensatory wetlands (1255.9 ha) were required as mitigation for impacts to 368 wetlands (1176.3 ha). The utility of the data on wetland area was limited, however, since 38.0% of the impacted wetlands and 41.6% of the compensatory wetlands lacked acreage data. The wetland type most frequently impacted (37.8% of impacted wetlands) and used in compensation (38.2% of compensatory wetlands) was palustrine forested wetlands. Estuarine intertidal emergent wetlands had the most area impacted (52.3%) and compensated (62.5%). The majority of the wetlands were small (less than or equal to 4.0 ha in size). Wildlife habitat was the most frequently listed function of impacted wetlands (90.7% of the permits) and objective of compensatory wetlands (83.3%). Endangered species were listed as affected in 20.4% of impacted and 21.0% of compensatory projects. The number of permits requiring compensatory mitigation and the number of impacted and compensatory wetlands increased from 1971 to 1986.Documentation of the details of Section 404 permit decisions was inadequate for the permits we examined. Area information and specific locations of impacted and compensatory wetlands were lacking or of poor quality. Follow-up information was also inadequate. For example, project completion dates were specified in the permit for only 2.2% of compensatory wetlands. Furthermore, less than one-third (31.5%) of the permits required the compensatory wetland to be monitored by at least one site visit. We recommend improved documentation, regular reporting, and increased monitoring for better evaluation of the Section 404 permitting system.     

Development of a protocol for recognizing sulfidic sediments (potential acid sulfate soils) in freshwater wetlands

Summary   The presence of sulfidic sediments (potential acid sulfate soils) is an emerging problem in the management of inland wetlands. Using data from 81 wetlands in the Murray-Darling Basin, a simple protocol was developed to assess whether a wetland will contain sulfidic sediments at levels that could cause ecological damage. Risk factors include whether or not the wetland receives municipal waste or irrigation return water, elevated salinity in the overlying water (>1750 µS/cm) or sediment (400 µS/cm in a 1:5 soil : water extract) and high levels of sulfate in the water column (>10 mg/L). Neutral or basic sediment pH indicates that, even if the sediment does contain sulfidic sediments, there is a reduced likelihood of acidification if the sediments are oxidized.