Spartina Alterniflora Salt Marsh Research Articles

Coupled nitrification-denitrification measured in situ in a Spartina alterniflora marsh with a 15NH4+ tracer

Measurements of N losses by denitrification from saltmarsh sediments have proved difficult because of the importance of plant metabolism and tidal cycles to sediment N cycling. In vitro approaches often do not measure the dominant coupled nitrification-denitrification pathway and/or alter in situ plant growth and redox conditions. We developed an in situ 15 NH4 + tracer approach to measure coupled nitrification-denitrification fluxes in an undisturbed New England Spartina alterniflora saltmarsh. The tracer was line-injected into sediments underlying natural S. alterniflora stands and in similar areas receiving long-term N amendment (up to 11.2 mol organic N m -2 yr -1 for 16 to 23 yr), and 15 N retention and loss routes were followed for 1 to 5 d. Denitrification losses in unfertilized grass stands ranged from 0.4 to 11.9 mmol N m -2 d -1 (0.77 ± 0.18 mol N m -2 yr -1 ). Denitrification in unfertilized sediments remained low until late summer, but underwent a ca. 4-fold increase in August and September, although sediment temperatures and respiration rates were high throughout the summer. Plant N uptake may limit the availability of N to support denitrification dur- ing the early summer, and denitrification may be released from competition with plant uptake in late summer, when plant growth slows. Denitrification rates in fertilized areas ranged from 22 to 77 mmol N m -2 d -1 (10.5 ± 4.9 mol N m -2 yr -1 ), and denitrification was likely controlled by the availability of fertilizer N rather than by competition with plants, since N was added in excess of plant demand. Our results emphasize the importance of in situ measurements of denitrification in understanding the dynamics of saltmarsh N cycling.

A NEW IDEA IN MARSH CORING

Standard coring techniques are often ineffective in the unconsolidated and vegetated soils and sediments of marsh environments. In this paper, a novel coring device is presented that minimizes the problems of compaction, core plugging, and root disturbance to allow the collection of intact 35+ cm cores from densely vegetated marsh areas. The simple concept uses a sharpened main body and cover plate that are inserted sequentially to obtain a wedge‐shaped soil or sediment slice. In a typical application, the corer is transferred to the field laboratory where sectioning can occur. Removal of the cover plate exposes a large surface area of soil or sediment for visual inspection and sampling. The advantages of the wedge corer design are described in relation to its use in a Spartina alterniflora salt marsh.

INTER-YEAR CARRYOVER EFFECTS OF A NUTRIENT PULSE ON SPARTINA PLANTS, HERBIVORES, AND NATURAL ENEMIES

Pulsed resources, such as natural and anthropogenic inputs of nutrients into natural communities, can have important consequences for primary productivity, as well as for consumers and their predators. Little, however, is known of how a resource pulse influences community assemblages for periods longer than one growing season. This study, repeated twice and in two different habitats on a mid-Atlantic Spartina alterniflora salt marsh, showed that a one-time nitrogen (N) subsidy can have not only significant within- year effects on plant primary production and herbivore and natural enemy abundance, but can also have long-term effects on plants and arthropod food web structure. Spartina plants exhibited significantly greater biomass for 2-3 yr and elevated per- centage of N for up to two years following the nutrient pulse, an effect that had direct positive effects on herbivores that were sensitive to variation in plant N content. Populations of Prokelisia planthoppers (Hemiptera: Delphacidae) were elevated in fertilized plots for up to three years following the nutrient addition. However, Trigonotylus uhleri, an herbiv- orous mirid (Hemiptera: Miridae), was more abundant on previously fertilized plants only for a brief time, either within the same season as the nutrient addition, or for only one year after the pulse. The carryover effect of the nutrient pulse on plants and herbivores also propagated to the third trophic level. Both non-lycosid spiders (mostly linyphiids) and a specialist egg predator of Spartina planthoppers (Tytthus vagus) were more abundant in previously fertilized plots for up to two years following the nutrient pulse. In contrast, wolf spider (Lycosidae) densities were elevated in fertilized plots only within the same season as the initial fertilization pulse. Food web structure, as indexed by herbivore:predator ratio, was altered in plots that received a one-time N subsidy, with the arthropod food web in fertilized Spartina taking three years to resemble that of unperturbed Spartina. The response of particular herbivores and predators to the nutrient pulse was in part habitat dependent (contiguous Spartina meadows vs. isolated islets), suggesting that habitat heterogeneity combined with the differential dispersal ability of arthropods can influence the long-term response of a food web to a nutrient pulse.

Impact of fiddler crabs and plant roots on sediment biogeochemistry in a Georgia saltmarsh

The influence of macrofauna and macrophytes on sediment biogeochemistry was quantified in a Spartina alterniflora (Loisel) saltmarsh, with emphasis on sulfur and iron cycling. Vertical profiles of sediment geochemistry and rates of microbial metabolism at 3 sites with different abundances of fiddler crab Uca pugnax burrows, vegetation coverage and hydrology were supple- mented with high-resolution radial profiles around burrow walls and S. alterniflora roots. Carbon oxi- dation was measured as sulfate reduction using the 35 S technique, as total anaerobic CO2 production, and as Fe(III) reduction by monitoring Fe(II) evolution. Depth-integrated (0 to 10 cm) sulfate reduc- tion was 25% lower, while total Fe and Fe(III) concentrations were 1.5 and 6 times higher, respec- tively, in bioturbated than in nonbioturbated sediment. Low sulfate-reduction rates adjacent to bur- row walls (3% of those in bulk sediment) were counteracted by very high Fe(III) reduction rates. Thus, Fe(III) reduction accounted for 54 to 86% of the total carbon oxidation within 4 cm distance of burrows, decreasing in importance with distance from the burrow wall. Overall, S. alterniflora roots showed a greater impact on sediment biogeochemistry than crab burrows. Sulfate reduction was almost absent in the rhizosphere, whereas Fe(III) reduction rates (6.2 µmol Fe cm -3 d -1 ) were among the highest reported for marine sediments, accounting for >99% of carbon oxidation. Our results con- firm the universal relationship between the contribution of Fe(III) respiration to total carbon oxidation and solid Fe(III) concentrations that has been suggested based on studies of subtidal marine sedi- ments. The importance of Fe(III) respiration was strongly dependent on Fe(III) concentrations below levels of 30 µmol cm -3 , whereas above this level almost all anaerobic respiration was mediated by Fe(III) reduction in saltmarsh sediments.

Diel feeding behavior of meiofauna and their relationships with microalgal resources

Diel variation of feeding by ostracods and harpacticoid copepod species on microalgae was examined in a mudflat of a Spartina alterniflora saltmarsh. Feeding (gut pigments and consumption of 14C‐labeled algae) and benthic microalgal abundance and composition (HPLC analysis of photopigments) were measured every 6 h over a 48‐h period. Midday feeding peaks were detected in Coullana sp. juveniles and adult females (but not males), Microarthridion littorale, Pseudostenhelia wellsi, and ostracods and were coincident with peaks in microalgal biomass. This pattern of midday feeding peaks by meiofauna differs from classical models of zooplankton feeding, which typically peak at night. Midday feeding peaks were apparently influenced by functional responses to food availability (ostracods and Coullana sp. females and juveniles), entrained diel rhythms (M. littorale), influence of light—positive (M.littorale) or negative (Coullana sp.), and possibly by vertical migration of diatoms within sediment. The negative influence of light on grazing by Coullana sp. may have implications for its feeding activity during midday low tides. Diatoms dominated the benthic microalgae, but cyanobacteria and chlorophytes contributed significantly to the planktonic community. Coullana sp. gut pigments indicate that at least part of its diet is planktonic, but it selectively avoids planktonic cyanobacteria. Diel variation of microalgal biomass appears to be influenced by meiofaunal grazing, which implies that meiofauna represent an important link between microalgal primary production and higher trophic levels.

Restoration of a Spartina alterniflora salt marsh following a fuel oil spill, New York City, NY.

In the seven years since 2.5 million liters of No. 2fuel oil spilled into the Arthur Kill, the Salt MarshRestoration Team of New York City Parks has restoredSpartina alterniflora(Salt Marsh Cordgrass)to 2.43 ha of shoreline, planting seedlings andtransplants in areas of low salt marsh severelyimpacted by oil. Restoration was undertaken to haltsurface erosion and the loss of surviving vegetationand remnant peat. Biomass, stem density, flowerdensity, height of plants, rhizome spread, basal areaand plant cover were monitored for a minimum of threeyears between 1993 and 1997. Unplanted SeverelyImpacted (USI) reference sites and Existing Vegetation(EV) in the severe impact zone were also monitored.Ninety-five percent of the surface area denuded ofvegetation by oil at USI reference sites remainedunvegetated seven years after the spill. SedimentTotal Petroleum Hydrocarbon (TPH) content was measuredbefore and after plantings and these results indicateda high level of persistent contamination. Residual oilwas not the determining factor in the survival or lossof Spartina alternifloraseedlings andtransplants at planting sites. Instead, plantspacing, shoreline morphology, wave energy generatedby passing vessels, and predation by Brantacanadensis(Canada Goose) were the most criticalfactors. Three years after planting, the abovegroundbiomass at two of the three restoration sites wascomparable to the biomass at existing and restoredeastern North American salt marshes. Seedlings spaced30 cm apart provided rapid cover at two of three sitesand contributed to overall survival. Where initialsurvival was high, goose predation was low. Whereinitial survival was low, shoreline morphology andwave energy were the primary causes of mortality, withgoose predation an important secondary cause. Bedformsat one planting site indicated a high energyshoreline as did sediment texture results for allsites. The fetch along the Arthur Kill is not longenough to generate such high-wave energy, but passingvessels do generate plunging and surging breakers ona regular basis. A reduction in the frequency of oilspills since 1990 has been beneficial to the saltmarshes along the Arthur Kill. A reduction in otheranthropogenic stresses would further enhance theplanted and existing vegetation.

Co-development of wetland soils and benthic invertebrate communities following salt marsh creation

The development of wetland soil characteristics andbenthic invertebrate communities were evaluated increated Spartina alterniflorasalt marshes inNorth Carolina ranging in age from 1 to 25 years-old.A combination of measurements from different-agecreated marshes as well as periodic measurements overtime on two marshes were used to (1) document rates ofwetland pedogenesis, especially soil organic matter,and, (2) explore relationships between soil andbenthic invertebrate community development. Soilmacro-organic matter (MOM, the living and dead rootand rhizome mat), organic C and N increased and bulkdensity decreased during the 25 years following marshestablishment. The most dramatic changes in bulkdensity, MOM, C and N occurred within the upper 10 cmof the soil with lesser changes below this depth.Created marshes were sinks for organic C (90–140g·m-2·yr-1) and N (7–11g·m-2·yr-1) but not for P (0–1g·m-2·yr-1). The density of benthicinvertebrates (>250 μm) and subsurface-depositfeeding oligochaetes also increased over time oncreated salt marshes. Invertebrate and oligochaetedensity were strongly related to MOM content(r2= 0.83–0.87) and soil organic C(r2= 0.52–0.82) and N (r2= 0.62–0.84). Thesefindings suggest that, in created salt marshes,development of the benthic invertebrate community istied to marsh soil formation, especially accumulationof organic matter as MOM and soil. Field studies thatmanipulate the quantity and quality of soil organicmatter are needed to elucidate the relationshipbetween salt marsh pedogenesis and benthicinvertebrate community development.

Spartina alternifloraDieback Recovery Correlates with Increased Acetylene Reduction Activity in Saltmarsh Sediments

Spartina alterniflorasalt marshes occasionally exhibit areas where the plants have all died off for no apparent reason. These dieback areas remain devoid of plant growth for months to years. An analysis of microbial acetylene reduction activity (ARA) and porewater chemistry of four such diebacks has been carried out on marshes in the Cooper River estuary, South Carolina, U.S.A. Four different diebacks were studied and sediments in all of them showed low rates of ARA, relative to sediments from the control areas which were populated by healthyS. alternifloraplants. The pore water of all the dieback sediments had higher salinities than the controls when this study began, but this trend was not consistent over the 18-month study period. Furthermore, dissolved ammonium and sulfide in the pore water, microbial biomass, organic matter and macro-organic matter content did not show a consistent trend differentiating the control and dieback sediments over this study period. During the course of this study, one of the diebacks recovered and the recolonisation of the barren area with healthy plants correlated with a full recovery of sediment ARA. The return of ARA to the sediments of this recovered marsh could not be correlated, however, with any of the porewater parameters measured (including NH4+), nor with any of the sediment characteristics. It is concluded that the lower levels of bacterial ARA in the diebacks may be due to the lack of essential factors associated with healthy spartina plants.

Response of a benthic food web to hydrocarbon contamination

Direct and indirect effects of diesel-contaminated sediment on microalgae, meiofauna, and meiofauna-microalgae trophic interactions were examined in a microcosm study of the sediment community from a Spartina alterniflora salt marsh. Microcosms of natural sediment were given small daily doses of contaminated sediment over a 28-d period, creating low-, medium-, and high-diesel treatment concentrations of ∼0.5, 5.5, and 55 ppm PAH, respectively. Diesel caused initial (within 7 h) reductions in microalgal grazing by meiobenthic harpacticoid copepods. Over longer periods of exposure (7–28 d), grazing on microalgae by copepods as a group was reduced in high-diesel treatments, primarily because of high copepod mortality. In contrast, grazing by and abundance of Cletocamptus deitersi (a copepod) was significantly enhanced in high-diesel treatments. Concurrent with reduced grazing by copepods, nematode grazing rates increased significantly in high-diesel treatments, indicating possible competition for microalgae between copepods and nematodes. In spite of transiently enhanced grazing by nematodes and C. deitersi, total meiofaunal grazing on microalgae was reduced in high-diesel treatments. Increased Chl a : pheopigment ratios in contaminated sediments were also indicative of reduced grazing pressure. A large (10×) increase in microalgal biomass was observed in high-diesel treatments and was likely a consequence of reduced meiofaunal grazing. The general responses observed in microcosms were also observed in a field study of polycyclic aromatic hydrocarbon contamination. Collectively, our data indicate that benthic microalgal biomass is controlled by meiofaunal grazing and that meiofauna may compete for limited algal resources. Furthermore, consideration of multiple trophic levels and their interactions allows a more complete and ecologically meaningful understanding of the mechanisms by which contaminants induce changes in natural communities.

BURNING OF OILED LOUISIANA COASTAL MARSH: FIELD EVALUATION

ABSTRACT Burning was evaluated as a method of remediating oiled Louisiana Spartina alterniflora salt marsh. A short-term reduction in plant biomass was observed; however, 1 year after burning, plant biomass was the same as in control plots. A comparison of the normal alkane profile in the soil residue following oiling to preburn oil showed a loss of more volatile hydrocarbons. Similar patterns were observed for aromatic hydrocarbons. More than half the aromatic hydrocarbons detected in the plume were derived from unburned hydrocarbons. Carbonyl sulfide and carbon disulfide were the main sulfur gases found in the smoke plume.

Development of a process-based nitrogen mass balance model for a Virginia (USA) Spartina alterniflora salt marsh:implications for net DIN flux

Development of a process-based nitrogen mass balance model for a Virginia (USA) Spartina alterniflora salt marsh:implications for net DIN flux

Interactions of Tin(IV) and monomethyltin cation in estuarine water-sediment slurries from the great bay estuary, New Hampshire, USA

This study describes experiments on sediment-estuarine water slurries originating from a Spartina alterniflora salt marsh. We investigated the fate of tin(IV) or monomethyltin cation (MeSn 3+ ) chlorides after their additon to slurries under anaerobic and aerobic conditions. We did not observe methylation of tin in anaerobic or aerobic slurries with and without added tin(IV). MeSn 3+ -amended samples occasionally formed small amounts of Me 2 Sn 2+ or Me 3 Sn + after extended periods of time, particularly when MeSn 3+ remained in solution. The stability of MeSn 3+ in slurries demonstrates that the absence of net methylation of tin(IV) is not due to rapid demethylation of MeSn 3+ or its further methylation. Inorganic tin concentrations in the aqueous phase of anaerobic slurries spiked with MeSn 3+ and unspiked slurries decreased by about 85% in 21 days and remained relatively constant until the end of the 59-day experiments. In similar anaerobic experiments about 25% of the MeSn 3+ spike was adsorbed to sediment within 1 h and about 75% was adsorbed within 10 days. The lack of methylation and demethylation reactions in our aerobic and anaerobic slurries, which contrasts with two previous reports, undoubtedly reflects the absence of added nutrients and low concentrations of added tin(IV) in our experiments. We believe that our model experiments more accurately reflect conditions in salt marshes than do previous studies. We conclude that future model studies on methylation of inorganic tin should include S. alterniflora because it is so prominent in observations of methyltin compounds in the estuary.

Formation of volatile sulfur compounds in salt marsh sediment as influenced by soil redox condition

The effect of soil redox condition on the production or formation of gaseous sulfur compounds in anaerobic salt marsh soil was studied. Marsh soil from a Louisiana Gulf Coast Spartina alterniflora salt marsh was incubated under controlled soil redox potentials ranging from +220 mV to −240 mV, which represent a range in anaerobic soil conditions. The gas phase production of hydrogen sulfide, methanethiol, dimethyl sulfide, carbonyl sulfide, and carbon disulfide as influenced by soil redox level was quantified. Total reduced sulfur gases increased with decreasing soil redox potential. Percentage composition of the individual sulfur gases varied depending on soil redox level. Methanethiol, dimethyl sulfide and carbon disulfide progressively increased with decrease in soil redox level. A major increase in hydrogen sulfide was measured at redox potential of −100 mV and below. Likewise a significant increase in carbonyl sulfide was observed between −70 and −100 mV. Results show that intensity of soil reduction or degree of anaerobiosis is important in the production of these gaseous sulfur compounds.

Modelling water circulation in an estuary and intertidal salt marsh system

An implicit numerical model was successfully used to simulate water circulation in North Inlet, an estuarine system in South Carolina consisting of extensive Spartina alterniflora salt marshes and numerous interconnected tidal creeks. The model allows for grid elements to become flooded as the tide rises. We found that tidal water surface slopes and vegetation density in the salt marsh control tidal currents in the creeks. Sheet flow across the marsh at high stages of the tide generates pronounced current asymmetry in the creeks.

Dinitrogen and nitrous oxide emission and entrapment in Spartina alterniflora saltmarsh soils following addition of N-15 labelled ammonium and nitrate

Sediment cores were collected from a Spartina alterniflora saltmarsh (dormant season) located in Barataria Basin, Louisiana, U.S.A. Highly N-15 labelled NH 4 + and NO 3 − sources were added and gaseous emission and entrapment of 15N 2 and N 2O resulting from nitrification/denitrification in the flooded sediments were investigated over 33 days. Denitrification of the surface-applied NO 3 − was rapid and significantly higher on all sampling dates compared with 15N 2 emissions from the NH 4 + treated sediment surfaces. Significant concentrations of 15N 2 and N 2O were entrapped in the NO 3 − treated sediments as compared with very low values of 15N 2 and N 2O accumulation in the sediment receiving added NH 4 +. Ratios of N 2 N 2O ranged from 3 to 250 with the lower ratios measured over the first 11 days. At the conclusion of the study, approximately 23% of the added 15NO 3 −N remained in the sediment columns compared with 90% for the 15NH 4 +N treatments.

Estimation of primary production using five different methods in a Spartina alterniflora salt marsh

The aboveground production of Spartina alterniflora in a salt marsh in Barataria Bay, Louisiana, USA was estimated using five different harvest methods: peak standing crop (PSC), Milner-Hughes, Smalley, Wiegert-Evans, and Lomnicki et al., and a non-destructive method based on measurement of stem density and longevity. Annual production estimates were 831 ± 41, 831 ± 62, 1231 ± 252, 1873 ± 147 and 1437 ± 96 g dry wt m−2 for each method, respectively. The average longevity of individually tagged young shoots was 5.2 ± 0.2 months, equivalent to an annual turnover rate of 2.3 crops per year. Among the five methods, Wiegert-Evans and Lomnicki et al. were considered more accurate than the other three because they corrected for mortality losses between sampling times. The Lomnicki et al. method was preferred over the Wiegert-Evans method because of its greater simplicity.

Effects of filter-feeding by the ribbed mussel Geukensia demissa on the water-column microbiota of a Spartina alterniflora saltmarsh

Effects of filter-feeding by the ribbed mussel Geukensia demissa on the water-column microbiota of a Spartina alterniflora saltmarsh

Multiple Disturbances in a Spartina alterniflora Salt Marsh: Are they Additive?

TURNER, M. G. (Env. Sci. Div., Oak Ridge Natl. Lab., Oak Ridge, TN 37831). Multiple disturbances in a Spartina alterniflora salt marsh: Are they additive? Bull. Torrey Bot. Club 115: 196-202. 1988.-The role of ecological disturbance has received much attention, but most studies consider single rather than multiple types of disturbance. An experiment was conducted to determine whether combinations of disturbances (clipping, trampling and fire) elicit additive responses from Spartina alterniflora Loisel. equivalent to the sum of responses to the individual disturbances. When combined, clipping and trampling had additive effects on aboveground standing stocks of Spartina, but combinations of fire with clipping or trampling had less effect than predicted. Effects on net aboveground primary production (NAPP) differed from effects on standing stocks. Clipping combined with trampling or burning reduced NAPP more than predicted, whereas the effect of burning and trampling on NAPP was additive. Thus, nonadditive responses to multiple disturbances can be identified and quantified, but the nature of the effect may differ with the parameter studied. Understanding such interactions is necessary to predict ecosystem dynamics in response to disturbances.

Evaluation of alternative oil spill cleanup techniques in a Spartina alterniflora salt marsh

Three oil spill situations which cause long-term impact were simulated in 1 m 2 salt marsh plots to evaluate the effectiveness of alternative cleanup techniques at removing oil and reducing damage to Spartina alterniflora. Cleanup techniques, implemented 18–24 h after oiling, were not effective at removing oil after sediment penetration. When oil remained on the sediment surface, flushing techniques were most effective at removal, reducing levels of added oil by 73% to 83%. The addition of dispersant to the flushing stream only slightly enhanced oil removal. Clipping of vegetation followed by sorbent pad application to sediment was moderately effective, reducing added oil by 36% to 44%. In contrast to flushing and clipping, burning increased the amount of oil in sediment by 27% to 72%. Although flushing and clipping were effective at oil removal, neither technique reduced initial damage to plants or enhanced long-term recovery. While flushed plots sustained no additional plant damage due to cleanup, clipped and burned plots sustained additional initial plant damage. Based on these results, first considerations should be given to natural tidal flushing as the means to remove oil, especially in salt marshes subject to ample tidal inundation. Although our results do not support cleanup in salt marshes with ample tidal inundation, low pressure flushing may be warranted when fuel oils or large quantities of crude oil impact salt marshes subject to reduced tidal flushing. Flushing, when warranted, should be initiated prior to oil penetration into the substrate. Clipping may be considered as a cleanup response only when heavy oil cannot be effectively removed from vegetation by flushing. Burning is not recommended because it enhances oil penetration into sediment and causes substantial initial plant damage.

Evidence for NH4+ switch-off regulation of nitrogenase activity by bacteria in salt marsh sediments and roots of the grass Spartina alterniflora.

The regulatory effect of NH4+ on nitrogen fixation in a Spartina alterniflora salt marsh was examined. Acetylene reduction activity (ARA) measured in situ was only partially inhibited by NH4+ in both the light and dark after 2 h. In vitro analysis of bulk sediment divided into sediment particles, live and dead roots, and rhizomes showed that microbes associated with sediment and dead roots have a great potential for anaerobic C2H2 reduction, but only if amended with a carbon source such as mannose. Only live roots had significant rates of ARA without an added carbon source. In sediment, N2-fixing mannose enrichment cultures could be distinguished from those enriched by lactate in that only the latter were rapidly inhibited by NH4+. Ammonia also inhibited ARA in dead and live roots and in surface-sterilized roots. The rate of this inhibition appeared to be too rapid to be attributed to the repression and subsequent dilution of nitrogenase. The kinetic characteristics of this inhibition and its prevention in root-associated microbes by methionine sulfoximine are consistent with the NH4+ switch-off-switch-on mechanism of nitrogenase regulation.