Marsh Creeks Research Articles

Temporal sampling and discharge asymmetry in salt marsh creeks

Studies of tidal flows in salt marsh creeks have shown velocity pulses on certain tides, although these have often been overlooked in considering temporal sampling designs for the measurement of discharge asymmetry. Velocity measurements for both spring and neap tides were taken at 5-min intervals at Bridge Creek in south-east Essex. The importance of temporal sampling interval in determining measured discharge asymmetry is examined using these data, integrating at intervals of between 5 and 30 min. The results indicate that sampling at 30-min intervals can underestimate discharge when velocity pulses on spring tides are not accurately monitored. Both under- and over-estimation of discharge on neap tides suggests that temporal sampling is also an important consideration when velocity pulses do not occur.

Temporal Patterns of Feeding by Blue Crabs (Callinectes sapidus) in a Tidal-Marsh Creek and Adjacent Seagrass Meadow in the Lower Chesapeake Bay

A 24-h study of blue crab feeding periodicity was conducted concurrently in a tidal marsh creek and adjacent seagrass meadow in the lower Chesapeake Bay. Crabs from the grassbed tended to have fuller guts than crabs from the marsh creek. In the grassbed, a weak trend toward nocturnal feeding was observed, with an apparent peak at dusk. During the day, crabs were not easily observed and were assumed to be feeding beneath the eelgrass canopy; at night crabs fed in the canopy. In the marsh creek, feeding was related to the tidal cycle, with guts being fullest at high tide and decreasing to lows just prior to the next high tide. This study suggests the potential importance of habitat on blue crab feeding patterns.

Meiobenthic gradients with special reference to Plathelminthes and Polychaeta in an estuarine salt marsh creek—a small-scale model for boreal tidal coasts?

Environmental conditions in salt marsh creeks are intermediate between the open tidal coast and estuaries. A large salt marsh creek at the island of Sylt (North Sea) was studied in order to test whether its fauna is more similar to that of the open tidal coast or to that of estuaries. Because of a sandy bar at the seaward opening, the tidal range is only 10 cm in the creek, and the water level never drops below the level of the sand bar. Zoobenthos in the sandy bottom and on the sandy shores was studied at both ends and in the middle of the creek. Polychaeta and Plathelminthes were determined to species level. On an average, 2115 metazoans were found below 10 cm2 of surface area. At the seaward end of the creek, abundance and taxonomic composition are similar to that of the adjoining Wadden area. Nematoda are the dominant taxon, followed by Copepoda, Plathelminthes and Oligochaeta. Taxonomic composition is different at the landward end. Plathelminthes and Nematoda are most abundant followed by Copepoda. Both Oligochaeta and Polychaeta are scarce at these newly eroded sites. Plathelminth abundance at the landward end of the creek is exceptionally high (770–935·10 cm−2). Contrary to what is generally found in estuaries, the species density of Plathelminthes shows a significant increase toward the land. The species composition of Polychaeta and Plathelminthes indicates that the sites below mean high tide level of the creek correspond to the adjacent eulittoral Wadden area while the fauna of the supralittoral sites of the creek is similar to the fauna of supralittoral tidal coasts. Typical sublittoral species did not occur in the salt marsh creek. Thus, salt marsh creeks may be regarded as a small-scale model for the tidal coast. In context with the results obtained, the definition of estuaries is discussed.

Hydrologic parameters of salt marsh peat

AbstractBecause of their profound influence on water movement and nutrient cycling in salt marshes, the two key physical properties of hydraulic conductivity and compressibility were studied in the Great Sippewissett Marsh and in the Ebben Creek Marsh in Massachusetts. Hydraulic conductivity was the most variable property: most frequently observed conductivities were of the order of 10−3 cm s−1 in both marshes, but extremes ranged from about 10−1 to 10−5 cm s−1. Compressibility was much less variable, and contributed of the order of 10−3 cm−1 to the specific storativity of marsh sediment, making compression a major mechanism for changes in water storage in the sediment. Surface sediments frequently exhibited below‐average conductivity, in contrast to freshwater bog peats which are usually most conductive at the surface. These measured properties may be applied to estimate the importance of many critical processes, such as the extent of infiltration occurring on the marsh surface, the hydrologic influence of the tidally varying creeks, and the hydrologic response to spring‐neap tidal cycles.

Ultilization of a seagrass meadow and tidal marsh creek by blue crabs Callinectes sapidus. I. Seasonal and annual variations in abundance with emphasis on post-settlement juveniles

Blue crabs Callinectes sapidus Rathbun were sampled in a lower Chesapeake Bay seagrass bed and adjacent tidal marsh creek from October 1982 through December 1986, using a drop net and suction sampler. Suction sampling was 88 % efficient and provided more accurate estimates of juvenile blue crab abundance, that were at least an order of magnitude greater than those obtained by conventional trawl gear For data analysis, C. sapidus were separated into 4 size classes by carapace width-54.25 mm (recently settled 1st and 2nd juveniles); 4.25 to 11.00 mm (3rd through 7th juvenile crabs); > 11.00 to 525.00 mm (8th through 12th juvenile crabs); and >25.00 mm (older juveniles and adults). Seasonal and annual cycles of C. sapidus abundance were observed in both habitats with annual differences most pronounced in the grassbed. Densities of C. sapidus were significantly greater in the grassbed in all but 2 of the 48 sampling dates. Settlement of the new year class appeared to be by megalopae and occurred from August through December A pulse of small C. sapidus C4.25 mm was observed in the grassbed from early to mid-September, whereas in the marsh creek this pulse occurred 2 to 4 wk later and consisted of 3rd stage and generally larger crabs (>4.25 mm). The small numbers of 1st and 2nd stage juvenile crabs ( 25 mm throughout the study period did not differ significantly among years (1983 to 1986) even though there were significant differences in the abundance of smaller sized individuals between 1983-84 and 1985-86. This suggests mortality within or emigration from grassbeds around this size. A possible ontogenetic shift in habitat use by crabs 11 to 25 mm may reflect a refuge in size from predation.

Fish and macrocrustacean use of submerged plant beds in tidal freshwater marsh creeks

Fishes and macrocrustaceans (nekton) were sampled biweekly from mid-June through October 1985 from submerged aquatic vegetation (SAV) and during September 1985 from unvegetated areas of tidal freshwater marsh creeks. Nineteen species of fishes (6918 individuals, 3.068 kg preserved wet weight) from 9 famhes, and 3 species of invertebrates (12036 individuals, 1.577 kg preserved wet weight) were collected from SAV The most abundant species were grass shrimp Palaemonetes pugio, banded killifish Fundulus diaphanus, mummlchogs F. heteroclitus, bluespotted sunfish Enneacanthus gloriosus, and mud crabs Rhithropanopeus harrisj:. Recruitment of small juvenile fishes of several species coincided with the period of greatest SAV area1 cover (late June through September). Average densities of fauna were significantly greater in SAV than over nearby unvegetated creek bottoms in September. Fauna1 abundance was not significantly related to SAV biomass, perhaps because the structural complexity of the SAV in our study area was high and nekton were abundant when SAV was present at low densities (i.e. low biomass). The numerically dominant species that occurred in SAV at low tide and on the marsh surface at high tide were similar Grass shrimp, banded lullifish, mummichogs and bluespotted sunfish accounted for > 90 % of the total number of organisms collected in each of the 2 habitats, SAV and marsh surface. The SAV of tidal freshwater marsh creeks is probably most important as habitat for forage fishes. Young of recreational species such as bluegill Lepomis macrochirus and pumpkinseed L. gibbosus also occupy this habitat.

Density, size distribution and home range of American eels, Anguilla rostrata, in a Massachusetts salt marsh

Local American eel stocks were studied by mark-recapture methods along 600m of tidal creeks in Great Sippewisset Marsh, Falmouth, Massachusetts, during summer 1979. The estimated stock density was 350 eels, equivalent to 875 fish ha-1, and movement of individual American eels over the five week study was usually less than 100 m. Large American eels were found to predominate in the wide marsh creeks whereas smaller American eels predominated in narrower creeks at the landward side of the marsh. Territoriality is suggested as a mechanism for maintaining differences in distribution of size classes and a limited home range.

The effects of predation by the mummichog, Fundulusheteroclitus (L.), on the abundance and distribution of the salt marsh snail, Melampus bidentatus (Say)

Enclosure and exclosure experiments were conducted in Canary Creek marsh to examine how predation by a killifish, Fundulus heteroclitus (L.), affects the abundance and size distribution of the salt marsh snail, Melampus bidentatus (Say). Enclosures (7.6 × 19.7 m) were stocked with Fundulus heteroclitus at densities of one-half normal, normal, twice normal, and four times normal density. Fish exclusion pens were also built. In both years of study, the mean density of snails increased significantly in pens where fish were excluded or their density reduced. During the same period in each year, the density of snails in pens containing higher than normal fish density fell by ≈50%. Fish density also affected the size distribution of snails within pens. In both years, mean shell length of snails in the pen with the highest density of fish was significantly greater, and mean shell length of snails within fish exclusion pens was significantly lower than in all other treatments. Gape size limitation of F. heteroclitus causes selective predation on small snails and apparently is responsible for the difference in mean shell length among treatments. Density and size distribution measurements of the natural Melampus bidentatus population in Canary Creek marsh were also taken. Larger snails were found to occur in the low marsh zone, whereas smaller snails occurred in the high marsh zone. Since the high marsh area is flooded less often than the low marsh, and the grass types found in the high marsh zone are known to afford protection from fish predation, the distribution of snails in the marsh is consistent with the idea that fish predation is an important factor influencing the distribution of snails in Canary Creek marsh.

Seasonal changes in surface level of a salt marsh creek

AbstractNineteen surveys were carried out over a two‐year period to determine the surface height of a salt marsh creek located on the north side of the River Esk, Cumbria, England. An AGA 112 electromagnetic distance measurer mounted on a Wild TI theodolite was used in conjunction with acrylic reflectors to follow the form of the ground. The results showed that there were no significant net trends in surface level, although seasonal variations of the order of 2 cm occurred. Vegetated areas responded in similar fashion to bare surfaces. It is thought that the elevational changes were attributable to the swelling of clay particles during the winter months rather than the effects of erosion and accretion.

Implications of sedimentological and hydrological processes on the distribution of radionuclides: The example of a salt marsh near Ravenglass, Cumbria

This paper summarizes sedimentological and hydrological studies at a salt marsh site on the north bank of the River Esk near Ravenglass which have a bearing on the fate of the low-level radioactive effluent from the reprocessing facility at Sellafield, Cumbria. A range of techniques has been used including electromagnetic distance measurement (EDM) and pore water pressure studies. The results show that: 1. (a) Over a two-year period there were no significant net changes in salt marsh creek level, although shorter-term (probably seasonal) fluctuations, of the order of 2 cm, occurred. These were attributed to expansion of clay particles during the winter months. Nearby, however, there were vertical changes of the order of 1 m due to erosion. 2. (b) Pore water pressures indicated a dynamic situation with very rapid responses both to tidal fluctuations and to rainfall. During neap tides there was clear evidence for water seeping upwards from the underlying clay/sand interface. Shortlived radionuclides ( 95 Zr 95 Nb and 106Ru) were detected in this zone. 3. (c) Soil polygons, once initiated by desiccation, thereafter provide preferential routes for water (and radionuclides) to the sub-surface sediment. These, and other results, are discussed in the context of previous studies. It is concluded that the complexity of the estuarine environment results in most data being site specific.

Effects of organic amendments on sulfate reduction activity, H2 consumption, and H2 production in salt marsh sediments

Sulfate reduction activity (SRA) was measured via the radioactive tracer ((35)SO4 (=)) technique in sediment samples from the Canary Creek Marsh in Lewes, Delaware. Basal levels of SRA ranged from 130 to 319 nmoles of sulfate reduced/gram dry sediment/hour. With the exception of lactate and formate, all organic acids tested resulted in no stimulation of SRA, whereas straight chain alcohols (C1-C4) all gave a significant increase in SRA. In addition, H2, glucose, and cellobiose caused a twofold or greater increase in SRA, while cellulose amendments did not alter SRA. Molybdate, an inhibitor of sulfate-reducing bacteria (SRB), caused a total inhibition in SRA. 2-Bromoethanesulfonic acid (BES), an inhibitor of methanogenic bacteria, caused a slight decrease in SRA. Hydrogen was not produced in detectable quantities in unamended samples but was produced in large amounts in glucose-amended samples. Hydrogen was rapidly consumed in unamended samples with molybdate additions causing a significant decrease in the rate of H2 consumption. A variety of organic amendments was found to stimulate H2 uptake. These studies suggest that SRB are stimulated by a large variety of organic amendments in situ and that SRB play a major role in maintaining low partial pressures of H2 in marsh sediments.

Effects of predators and food resources on the macrobenthos of salt marsh creeks

Effects of predators and food resources on the macrobenthos of salt marsh creeks

Osmotic potential and turgor maintenance in Spartina alterniflora Loisel.

The dependence of leaf water potential (Ψ), osmotic potential (π) and turgor pressure (P) on relative water content (RWC) was determined for leaves of tall and short growth forms of Spartina alterniflora Loisel. from a site on Canary Creek marsh in Lewes, Delaware. Tall plants (ca. 1.5 m) occured along a drainage ditch where interstitial water salinity was approximately 20‰, and short plants (ca. 0.2 m) were 13 m away near a pan and exposed to 80‰ salinity during the most stressful period. Leaves were collected at dawn and pressure-volume measurements were made as they desiccated in the laboratory. Pressure equilibrium was used to measure Ψ, RWC was determined from weight loss and dry weight, π was determined from the pressure volume curve, and P was calculated as the difference between Ψ and π. Physical properties of the bulk leaf tissue that have a role in regulating water balance of the two growth forms were estimated: relative water content of apoplastic water (RWCa) relative water content at zero turgor (RWC0), the bulk modulus of elasticity (E), and water capacity (C w). There were no detectable temporal trends in any of the parameters measured from Nune through September and no significant differences between the two growth forms when compared on the basis of RWCa, RWC0, E, and C w. There was a clear difference between the two growth forms with respect to π; at RWC0, π was-4.5±0.40 MPa for short form plants and-3.3±0.40 MPa for tall form.Turgor pressure of plants in the field (P') was lower in leaves from short form than for the tall form plants with average difference of about 0.4 MPa. In July, P' in short form leaves dropped to zero by mid-morning as expected for leaves experiencing water stress.These results show that S. alterniflora is capable of reducing osmotic potential in response to increased salinity and that turgor pressure was lower in short growth form than in tall forms.

Behaviour of iron, manganese, phosphate and humic acid during mixing in a Delaware salt marsh creek

The mixing behaviour of iron, manganese, phosphate and humic acid in a Delaware salt marsh creek was studied using field data, laboratory mixing experiments, and geochemical mass balance equations. Property-salinity diagrams for field data indicated that the removal of iron is 56–70% in the 0–10‰ salinity range. A proposed mechanism of removal is the flocculation of colloidal iron, perhaps with humic acid. Phosphate, however, undergoes 195% addition in the same low salinity region, which may be due to release of phosphate from resuspended sediments. Dissolved manganese is conserved, as is humic acid throughout the salt marsh mixing zone. Within the uncertainty of the data the maximum possible removal of humic acid is 23%. Laboratory mixing experiments that simulated salt marsh mixing along the same salinity gradient as observed in the field (5–25‰) showed only small-scale additions and removals compared to the field results. Such small-scale changes occurred largely at salinities >10‰ in the laboratory experiments, whereas most removals and additions occurred at salinities <10‰ in the field. Mixing studies also showed little difference between prefiltered and unfiltered mixes. The studies suggest that simple mixing of salt marsh waters, with or without suspended material, does not strongly influence the observed behaviour of dissolved constituents in salt marshes, and that other processes (e.g. sediment or intertidal exchange) must dominate their behaviour.

Aboveground and Belowground Primary Production Dynamics of Two Delaware Bay Tidal Marshes

ROMAN, C. T., AND F. C. DAIBER (College of Marine Studies, Univ. of Delaware, Newark, DE 19711). Aboveground and belowground primary production dynamics of two Delaware Bay tidal marshes. Bull. Torrey Bot. Club 111: 34-41. 1984.-Aboveground and belowground net primary productivity estimates of the dominant angiosperms from two tidal marshes along the Delaware Bay estuary are reported. Ash, carbon and nitrogen content of the aboveground and belowground components were also determined. Annual net aboveground production was determined by the peak live standing crop method and the Smalley (1958) method. Aerial production of tall Spartina alterniflora Loisel. at the Canary Creek salt marsh, employing the Smalley technique, was 1487 g m2 yr', while production of short S. alterniflora, S. patens (Ait.) Muhl. and Distichlis spicata (L.) Greene was, 654 g m-2 yr-1, 1147 g m-2 yrV1, and 785 g m-2 yr, respectively. At the brackish water Blackbird Creek marsh, Phragmites australis (Cav.) Trin. had the highest aboveground production (2940 g m2 yrV), followed by S. patens (1089 g m2 yr-1) and short S. alterniflora (916 g m2 yr-2 ). Belowground primary production was determined by the annual increment (max-min) method, with respective estimates of 6.5 kg m2 yrV, 5.0 kg m2 yr. , and 3.3 kg m2 yr1, for tall S. alterniflora, short S. alterniflora and S. patens, at the Canary Creek marsh. Belowground estimates at the Blackbird Creek marsh were within this range.

Population Dynamics of an Estuarine-Dependent Fish, the Spot (Leiostomus xanthurus), ASong a Tidal Creek–Seagrass Meadow Coenocline

To study the population dynamics of young-of-the-year spot (Leiostomus xanthurus) I released 6981 marked fish midway up the tidal creek portion of a small (&lt;20 ha) marsh creek–seagrass meadow coenocline. Holding mortality experiments (96 h) indicated that 61.5%, or 4300 individuals, survived the marking process to constitute the population available for recapture. Over a 90-d study period, 212 marked fishes were recaptured. From plots of the ratio of marked to unmarked individuals in subsequent samples, I concluded that the population was resident in the creek for up to 182 d with the average individual present for 91 d. When this population turnover rate was compared to the total population decay rate (marked plus unmarked fish), the exchange between habitats (immigration/emigration) accounted for about 26% of the total decay rate, with the remainder attributed to natural mortality. By correcting the overall disappearance rate for population turnover due to immigration/emigration, and using this adjusted value as a measure of instantaneous mortality (Z), the estimated production in this population was 21.8 kcal (91342 J)∙m−2∙d−1. This figure is over six times greater than previously reported values for this species for all size classes over the entire growing season.

Subtidal food webs in a georgia estuary: δ13C analysis

Stable carbon isotope compositions were analyzed for estuarine fauna collected in tidal creeks draining salt marshes dominated by either Spartina alterniflora Loisel. ( δ 13 C of −12.5%.) or Juncus roemerianus Scheele ( δ 13 C of −26%.). Mean δ 13 C values of subtidal invertebrates and fishes were −17.8%. and −17.5%. in the Spartina creek and −20.1%. and −20.0%. respectively in the two Juncus creeks. The intermediate δ 13 C values of the fauna implied an alternate carbon input to the food web, most probably benthic algae ( δ 13 C of −16 to −18%.) and phytoplankton ( δ 13 C of −20 to −22%.). In the Spartina marsh creek, animals with δ 13 C values less negative than −17%., e.g. mummichogs, mullet, and mud crabs, were most closely linked to the Spartina detritus/benthic algal food web, while species with δ 13 C values more negative than −19%., e.g. brown shrimp, menhaden, and oysters, were apparently more dependent on the phytoplankton food web. The data suggested that 1. (1) marsh plant carbon is a component of subtidal food webs, 2. (2) phytoplankton carbon is a more important food source for subtidal animals than for intertidal marsh fauna, 3. (3) the subtidal food web is structured such that individual invertebrate and fish species show varying degrees of dependence on the detritus/benthic algae-based food web of the marsh vs. the phytoplankton-based food web of the tidal creek.

Transport of microbial biomass through the North Inlet ecosystem

Tidal fluctuations and transports of total microbial biomass (measured as adenosine triphosphate [ATP]) were investigated at three marsh creeks comprising the major transfer points between the North Inlet marsh and the adjoining aquatic ecosystems. Two creeks, Town Creek and North Jones Creek, form the inlet mouth and are the only marsh-ocean exchange points. The third creek, South Jones Creek, connects to a brackish water embayment. The creeks were simultaneously sampled every 1.5 hours for 50 consecutive hours during neap tides (four tidal cycles) and 50 consecutive hours during spring tides of each season. At the inlet, ATP concentration fluctuated in phase with the tide during winter and fall and out of phase with the tide during the spring. Fluctuation patterns at South Jones Creek were irregular. The highest ATP concentrations were during the spring (mean=2.17 mg of ATP per m(3)) and the lowest concentrations were during the winter (mean=0.65 mg of ATP per m(3)). Net transports of ATP varied from tidal cycle to tidal cycle with regard to direction of transport (import or export) and magnitude. Net transports were small compared to large instantaneous transports and only 4 of 22 determinations of net transport were different from zero transport.

Ingestion, egestion, excretion, growth, and conversion efficiency for the mummichog, Fundulus heteroclitus (L.)

The food conversion efficiency of Fundulus heteroclitus (L.) was measured in terms of calories and nitrogen for three diets: Palaemonetes sp., Nereis sp., and Uca pugnax. Fish were allowed to feed ad libitum for 30–60 min each day. Growth, ingestion, egestion, and excretion were measured for fish fed each diet. The growth rates of Fundulus heteroclitus fed two of the single item diets of invertebrates were higher than growth rates previously estimated for mummichogs from the natural population in Canary Creek marsh. In comparison with other fish species, F. heteroclitus was found to have a higher than average assimilation efficiency ( X ̄ = 87% for all three diets) and a lower than average gross growth efficiency (≈12% for two of the diets). Metabolic costs accounted for an average of 69% of ingested energy. Excretion rates were also large, with excretion accounting for more energy than egestion in two of the three diets.

Seasonal Variability and Transport of Suspended Microfungi in a Southeastern Salt Marsh

Tidally induced fluctuations and transports of microfungi were investigated. Samples were collected at three depths from three stations positioned at a transect in a large salt marsh creek. Samples were taken every 1.5 h for 50 consecutive h during neap tides and 50 consecutive h during the corresponding spring tides. In each season, microfungi concentrations fluctuated out of phase with the tides during both neap and spring tides. Mean concentrations of suspended microfungi did not vary appreciably throughout the year. Fungi were exported from the marsh during the majority of the tidal cycles studied. The results suggest that microfungi may serve as indicators of water mass movements.