Head Of Creek Research Articles

Geographic variability in headward erosion of marsh tidal creeks: Ecological and physical causes

AbstractExpansion of drainage networks through the headward erosion of tidal creeks is an eco‐geomorphologic response of salt marshes to accelerated sea‐level rise (SLR). This response can counter the negative impacts of an elevation deficit by increasing drainage and encouraging plant health, thereby reducing potential for submergence and marsh platform loss. In the wetlands of Cape Romain, SC, intense bioturbation near creek heads by the common marsh crab Sesarma reticulatum has been found to facilitate sediment erosion and rapid creek growth. This keystone grazer has been recently observed to have increasing influence on landscape evolution throughout the southeast US coast. Here, we compare measurements taken at Sapelo Island, GA, with those previously collected at Cape Romain, to confirm that eco‐geomorphic feedbacks facilitating creek growth at each location are similar, and to compare these processes under differing background conditions. We use sediment cores, precise elevation measurements and historical imagery to compare substrate properties, elevation within the tidal frame, creek growth rates and drainage morphology at both sites. Our results show identical processes; however, the higher elevation of the marsh at Sapelo Island leads to shallower and shorter periods of tidal inundation, explaining the greater soil strength and lower belowground biomass compared with the marsh at Cape Romain. The smaller tidal range at the site in Cape Romain compared with Sapelo Island translates to a proportionally shallower depth of tidal creeks, which therefore requires less erosion to produce headward creek extension. These effects are likely to have contributed to slower growth rates of tidal creeks at Sapelo Island during the past several decades of SLR. Our findings highlight the similarities in process but differences in rates in how marshes are responding to climate‐related stress.

Directional movement of consumer fronts associated with creek heads in salt marshes.

Consumers often deplete local resources and aggregate along edges of remaining resources, forming "consumer fronts." We examined the factors that promote Sesarma reticulatum crab aggregations at saltmarsh creek heads to explain the directional but slow movement of these fronts. We also created artificial creek heads to test the hypothesis that hydrological conditions at creek heads create superior habitat for crabs. Soil temperatures were ˜11-12% cooler, hydrogen sulfide concentrations lower (0.0 vs. ˜0.58mg/L), and dissolved oxygen concentrations twofold higher at the creek head versus the marsh platform. In the artificial creek-head experiment, altering hydrological conditions led to lower dissolved sulfide levels, higher dissolved oxygen levels, and increased densities of crab burrows and Sesarma crabs. Moreover, the elevation of the soil surface declined rapidly at artificial creek heads versus controls, suggesting that crabs were increasing erosion. Our results suggest that abiotic conditions for crabs are better at the leading edge of the creek head than the trailing edge, explaining the directional movement of the front. Moreover, the speed at which the front propagates appears to be limited by the rate at which the creekhead erodes, rather than by crab mobility. The directional and slow movement of Sesarma fronts compared to consumer fronts of other invertebrates appears to result from the inextricable link between Sesarma and marsh geomorphology, whereas other consumer fronts are associated mostly with food resources.

A natural history model of New England salt marsh die-off.

Natural history gave birth to ecology and evolutionary biology, but today its importance is sometimes marginalized. Natural history provides context for ecological research, a concept that we illustrate using a consumer-driven vegetation die-off case study. For three decades, local predator depletion promoted the formation of high-density crab (Sesarma reticulatum) grazing and burrowing fronts, resulting in the spread of vegetation die-off through southern New England and Long Island marshes. We review results from a decade of research on this phenomenon and synthesize these findings with new field surveys, experiments, and historical reconstructions to test the hypothesis that the locations and processes of vegetation die-off and recovery are spatially predictable. We discovered that crab-driven die-off consistently begins on marsh creek heads, where peat and high flow conditions overlap, before spreading to inner creeks following peat availability, stunted cordgrass, and flow. Eventually, die-off eliminates most low marsh vegetation, leaving behind unvegetated substrate too soft to support burrows. Vegetation recovery exhibits the reverse patterns of die-off; it consistently begins in the low marsh within inner creeks, where soft substrate and low flow conditions overlap, before spreading to creek heads. This spatially explicit, substrate-dependent recovery eventually leads to ungrazed cordgrass abutting grazed cordgrass on the high marsh border. We present a conceptual model of die-off through recovery progression to provide managers and landowners with a diagnostic tool for identifying marsh die-off and recovery status. Collectively, this work illustrates the fundamental importance of long-term, natural history-based investigations of ecosystem dynamics in informing ecology, conservation, and management practices.

Ecosystem engineers drive creek formation in salt marshes.

Ecosystem engineers affect different organisms and processes in multiple ways at different spatial scales. Moreover, similar species may differ in their engineering effects for reasons that are not always clear. We examined the role of four species of burrowing crabs (Sesarma reticulatum, Eurytium limosum, Panopeus herbstii, Uca pugnax) in engineering tidal creek networks in salt marshes experiencing sea level rise. In the field, crab burrows were associated with heads of eroding creeks and the loss of plant (Spartina alterniflora) stems. S.reticulatum was closely associated with creek heads, but densities of the other crab species did not vary across marsh zones. In mesocosm experiments, S.reticulatum excavated the most soil and strongly reduced S.alterniflora biomass. The other three species excavated less and did not affect S.alterniflora. Creek heads with vegetation removed to simulate crab herbivory grew significantly faster than controls. Percolation rates of water into marsh sediments were 10 times faster at creek heads than on the marsh platform. Biomass decomposed two times faster at creek heads than on the marsh platform. Our results indicate that S.reticulatum increases creek growth by excavating sediments and by consuming plants, thereby increasing water flow and erosion at creek heads. Moreover, it is possible that S.reticulatum burrows also increase creek growth by increasing surface and subsurface erosion, and by increasing decomposition of organic matter at creek heads. Our results show that the interaction between crab and plant ecosystem engineers can have both positive and negative effects. At a small scale, in contrast to other marsh crabs, S.reticulatum harms rather than benefits plants, and increases erosion rather than marsh growth. At a large scale, however, S.reticulatum facilitates the drainage efficiency of the marsh through the expansion of tidal creek networks, and promotes marsh health.

A comparison of GPS and lidar salt marsh DEMs

ABSTRACTDigital elevation models (DEMs) were compared to characterize how well airborne lidar (light detection and ranging) data depict the microtopography of a salt marsh. 72,000 GPS points and 700,000 lidar points from a 1 km2 salt marsh island were linearly interpolated using identical DEM configurations. Overall, 78% of lidar elevations were within ±0.15 m of the high precision GPS elevations. Spatial arrangement of difference values reveal that lidar performed best on the marsh platform, and poorly along tidal creeks and creek heads. Also, the overall shape of the salt marsh was poorly defined, even where lidar data were within the reported range of accuracy. These observations indicate that lidar appears to be a robust tool for mapping intertidal landscapes. However, lidar DEMs may not adequately resolve the microtopographic variations of a salt marsh, and for research questions that require accurate depiction of small‐scale tidal creek networks and subtle terrain features lidar data should be augmented with other information. Copyright © 2011 John Wiley & Sons, Ltd.

Direct and indirect effects of burrowing crab Chasmagnathus granulatus activities on erosion of southwest Atlantic Sarcocornia‐dominated marshes

Using field measurements and field experiments, we investigated the effect of a dominant Southwest Atlantic intertidal burrowing crab, Chasmagnathus granulatus, on the inland growth of tidal creeks and creek genesis in salt marshes. By burrowing intensively on marsh sediments, this crab changed sediment physical parameters, such as penetrability, water content, and shear strength, which are related to sediment resistance to erosion. There were positive relationships between crab density and activities occurring in the creek heads and creek growth rates. Field experiments show that the presence and activity of C. granulatus and the presence of their burrows enhance the growth rates of tidal creeks, promoting marsh erosion. When crabs were present, these creeks grew faster than did creeks in which crabs were excluded. Furthermore, the interaction (disturbance and herbivory) between crabs and the dominant halophyte marsh plant, Sarcocornia perennis, generate circular depressions that accumulate standing water (salt pans), which in turn facilitates the creation of new creeks in the marsh surface, which evolve, to a greater extent, into fully functional tidal creeks because of colonization by crabs, which in turn further enhances creek growth rates. These direct and indirect effects of crabs on marsh erosion provide strong evidence of the importance of bioturbation and biological processes to the erosion and geomorphology of marshes.

Effects of topographic structure on salt marsh currents

The purpose of this study was to assess the spatial and temporal variability in overmarsh and in‐channel currents, and to assess that variability in the context of salt marsh topographic structure. We created a high accuracy digital elevation model of a salt marsh island using a real time kinematic Global Positioning System. We measured currents with two velocimeters at the heads of adjacent first order creeks of two separate intertidal creek networks, 30 m apart. We also monitored in‐channel currents with one current profiler. All measurements were taken during a 5‐day period with spring, mixed tides. Observations reveal that during the high‐high tides three current reversals occurred, one during flood, one near peak tide, and another during ebb, as opposed to the usual single reversal near peak tide. These reversals took place in shallow overmarsh flows and in deeper in‐channel flows. This current complexity appears to be related to tide elevation and the submergence or emergence of salt marsh topography, and it likely reflects interactions between local topographic forcing and larger scale barotrophic pressure gradients. Moreover, when the marsh platform was inundated but under ebb conditions the major components in overmarsh flow patterns between creek heads indicated a regular exchange of water between tidal creek systems. Hence the characterization of overmarsh flows as having flow divides between intertidal creek networks deserves greater scrutiny. Taken together, these observations show that the subtle topography of a salt marsh landscape exerts important control on the temporal and spatial variability on currents at centimeter‐ to creek network‐scales. More research is needed to characterize marsh topography, overmarsh circulation, and their combined effect on material transport and sediment accretion.

Mortality in Unionacean Mussels in a Year of Drought

In the year 1980 drought prevailed in south-central Kansas causing desiccation of shallower waters in streams. Numbers of dead unionacean mussels observed at twelve stations on two such streams are tabulated. Relevance of drought to past and future of the mussel fauna of the streams is discussed. In a previous paper (Metcalf, 1980) kinds of unionacean mussels found at a number of stations on Big Caney River and Grouse Creek, in southcentral Kansas, were reported. These are streams originating in the Flint Hills region. Grouse Creek heads in the area of conjunction of Cowley, Butler and Elk counties and flows diagonally southwestward across Cowley County, emptying into the Arkansas River near the Kansas-Oklahoma border. Big Caney River heads in southwestern Elk County and flows across western Chautauqua County. The segment surveyed on Big Caney extended only to the southern border of Kansas. Station numbers mentioned herein are as in Metcalf (1980), with numbering beginning upstream and continuing downstream. Stations are located at 4-8 km intervals (C = Big Caney River and G = Grouse Creek). The previous survey was carried out from 1969-1979, years when intermittency of streams did not occur at stations sampled. In 1980 drought conditions in the watersheds of these streams resulted in intermittency or minimal flow at all stations. Below are climatological data (NOAA, 1970-1980; data for July-December 1980, for Grenola, from F. M. Metcalf) for four towns located on or near the watersheds of the streams noted. Grenola is located on upper Big Caney River and Elgin on its lowermost reaches in Kansas. Dexter is located near mid-length of Grouse Creek and Arkansas City 12 km WNW of its mouth. Precipitation amounts are given, first, in inches (as published) and, second, in mm (calculated). Average annual precipitation for the years 19701979 is given before, range for these years within, and precipitation for 1980 after parentheses: This content downloaded from 207.46.13.11 on Wed, 10 Aug 2016 06:33:15 UTC All use subject to http://about.jstor.org/terms 90 TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCE Grenola 35.11 (25.04-48.95) 20.76; 892 (636-1243) 527 Elgin 37.74 (29.07-46.22) 24.27; 959 (738-1174) 616 Dexter 33.41 (26.16-42.87) 20.38; 849 (664-1089) 518 Arkansas City 34.57 (26.99-47.95) 25.00; 878 (686-1218) 635 Thus, for these four stations, 1980 precipitation was some 9.5 to 14.5 inches (240-365 mm) below the average for the decade 1970-1979. In addition to low precipitation, temperatures were elevated in the summer of 1980. Average temperatures for the summer months at Cedar Vale, midlength of Big Caney River, in Kansas, for 1979 (first) and 1980 (second)

The Hydrogen‐Ion Concentration of a Creek, Its Waterfall, Swamp and Ponds

This investigation was undertaken with the view of studying certain rather striking ecological features which occur in a creek situated in part on the campus of Johns Hopkins University at Homewood, Baltimore, Maryland. The creek originates as seepage in a shallow gulley which gradually becomes wider and deeper. At the base of this gulley the water collects in a slight depression, hereafter to be designated as the Small Pool (see Map of Creek, fig. 1). From this pool a stream arises which, by the addition of further seepage, becomes larger and widens out into several ponds, one of which is 100 feet in width and 105 feet in length (see Map, Small Pond, Bay, Euglena Pond ). The stream, continuing as rapids through the deepening gulley, which here assumes the proportions of a ravine, reaches a precipice marking the entrance of the ravine into a rather spacious, old quarry which is no longer in use. A small Waterfall forms as the stream flows over the precipice. In the quarry is a Swamp and a pond called the Quarry Pond on the map. The main interest in this stream centers in the fact that one of the ponds, the large one or the Euglena Pond mentioned above, has been covered for a number of years during most of the summer with a layer of Euglenae, while the other ponds, including the swamp, seemed to be free from that interesting plant-like animal. Accordingly, the authors made an effort during the summer of 1921 to study the factors which limit the distribution of Euglena and which localize it in the large pond. It was thought that the determination of the degree of acidity (hydrogenion concentration), the amount of free and combined carbon dioxide, and the temperature of the water at selected stations along the whole watercourse at definite intervals throughout a 24-hour period, would be a good introduction to the chemical side of the problem. Thirteen stations were chosen for their presumed critical importance with reference to the subject-matter of the investigation (compare with map). Station I. Small Pool. Bubbling, running water, in a pool about 18 inches in diameter. Near head of creek, with no aquatic vegetation. Shaded.

The Relationships of the Olentangy Shale and Associated Devonian Deposits of Northern Ohio

In the flat glaciated region to the south and east of Sandusky there are few outcrops of the older rocks. The drainage is mostly by small, weak streams which have not yet had time to erode extensive valleys, and railroads have not been compelled to cut deeply in order to establish their grades. About seven miles south of Sandusky, however, where the land is a little higher than in the city and the mantle rock is exceedingly thin, some of the creeks have exposed small sections of bedrock which are somewhat exaggerated by a considerable local dip. Two of the more important of these are to be found along Plum and Pipe creeks. These sections have been discussed elsewhere,2 but a recent study of the region has added some valuable facts to those formerly given and has made it possible to correlate this Ohio Hamilton with the Devonian deposits of the same age to the north of Lake Erie. Plum Creek heads about nine miles southeast of Sandusky and flows, in a general northerly direction, to the lake. At a point about two miles east-northeast of Prout station, on the Baltimore & Ohio Railroad, it cuts into Huron shale, and a little farther north into the Hamilton beds, exposing the following section: