Subaqueous soil

Last updated
Example of a subaqueous soil landscape map of Ninigret Pond, Charlestown, Rhode Island, USA Ninigret Subaqueous Soil Map.png
Example of a subaqueous soil landscape map of Ninigret Pond, Charlestown, Rhode Island, USA

Subaqueous soils are soils formed in sediment found in shallow, permanently flooded environments or soils in any areas permanently covered by water too deep for the growth of rooted plants.

Contents

The study of subaqueous soils is a relatively new field in Pedology or soil science. The concept that sediments in shallow water environments undergo soil-forming processes, are capable of supporting rooted plants (such as Eelgrass), and meet the definition of soil according to criteria in Soil Taxonomy has been moving soil scientists into a new frontier of soil survey – mapping subaqueous soils.

USDA soil taxonomy (ST) developed by United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters and in several levels: Order, Suborder, Great Group, Subgroup, Family, and Series. The classification was originally developed by Guy Donald Smith, former director of the U.S. Department of Agriculture's soil survey investigations.

The National Cooperative Soil Survey (NCSS) is a nationwide partnership of Federal, regional, State, and local agencies and institutions. This partnership works together to cooperatively investigate, inventory, document, classify, and interpret soils and to disseminate, publish, and promote the use of information about the soils of the United States and its trust territories. The activities of the NCSS are carried out on National, regional, and State levels.

The USDA-Natural Resources Conservation Service (NRCS) is the lead federal agency for mapping and developing interpretations for the nation's soil resources and the extension of soil survey technology to global applications.

United States Department of Agriculture department of United States government responsible policy on farming, agriculture, forestry, and food

The United States Department of Agriculture (USDA), also known as the Agriculture Department, is the U.S. federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of farmers and ranchers, promote agricultural trade and production, work to assure food safety, protect natural resources, foster rural communities and end hunger in the United States and internationally.

Natural Resources Conservation Service (NRCS), formerly known as the Soil Conservation Service (SCS), is an agency of the United States Department of Agriculture (USDA) that provides technical assistance to farmers and other private landowners and managers.

Subaqueous and Submerged Soils

As the name implies, subaqueous and submerged soils are soils that occur under water (both fresh and salt water). The depth range of the water column where these soils may be found is not known, an arbitrary depth of 2.5 meters below the surface has been set for soil survey inventory but some states have extended this depth to 5 m (NAVD 88). The difference between subaqueous and submerged soils is that submerged soils formed in an upland environment then became submerged as a result of rising water tables, flooding events (such as a Beaver Dam), or sea level rise. Subaqueous soils formed under a continuous water column (such as in an estuary), although their sediments may have originated from an upland area such as a dune.

Sea level rise The current long-term trend for sea levels to rise mainly in response to global warming

Since at least the start of the 20th century, the average global sea level has been rising. Between 1900 and 2016, the sea level rose by 16–21 cm (6.3–8.3 in). More precise data gathered from satellite radar measurements reveal an accelerating rise of 7.5 cm (3.0 in) from 1993 to 2017, which is a trend of roughly 30 cm (12 in) per century. This acceleration is due mostly to human-caused global warming, which is driving thermal expansion of seawater and the melting of land-based ice sheets and glaciers. Between 1993 and 2018, thermal expansion of the oceans contributed 42% to sea level rise; the melting of temperate glaciers, 21%; Greenland, 15%; and Antarctica, 8%. Climate scientists expect the rate to further accelerate during the 21st century.

Estuary A partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea.

Although proposals to include permanently submersed sediments as soil have been put forth since the mid-1800s, it was not until the early 1990s that the concept of subaqueous soils was developed in the U.S. The pioneer in U.S. subaqueous soils is the late George Demas, a soil scientist working for the National Cooperative Soil Survey in the Chesapeake Bay region of Maryland. Dr. Demas observed that subaqueous areas met the definition of soil by being able to support rooted plant growth (such as Eelgrass) and had formed soil horizons. Further study revealed that these submersed sediments underwent other soil forming (pedogenic) processes including additions, losses, and transformations of energy and matter.

George Demas was an American pedologist whose pioneering studies of subaqueous soil contributed to the understanding of soil formation and the expansion of the concept of soil. USDA soil taxonomy was revised as a result.

<i>Zostera</i> genus of plants

Zostera is a small genus of widely distributed seagrasses, commonly called marine eelgrass or simply eelgrass. The genus Zostera contains 15 species.

Significance of Subaqueous Soils

A major limitation to science-based management of shallow water habitats has been a lack of definitive information on the properties and spatial distribution of subaqueous soils. In part, this lack of information has stemmed from an inadequate paradigm for subaqueous soils, which has not considered them "soils" at all, but rather as "sediments". During the last decade, it has been demonstrated that these "sediments" would be better understood as "soils" and that the sedimentary paradigm should give way to a pedological paradigm.

An advantage of using the pedological approach to study shallow water habitat is that soils are studied as a collection of horizons that are linked vertically with depth and horizontally across the subaqueous landscape. These horizons are studied and characterized by examining a combination of properties and characteristics, instead of, say, a single component or parameter. In this manner, subaqueous soil can be characterized as ecological map units and provide a site-based system to identify the geomorphic settings that represent the subaqueous landscape. The following are some advantages of using an emphasis on subaqueous soils in shallow water classification:

  1. Sediment characteristics presented to a greater depth (2 m), rather than a bottom-type classification (such as mud bottom or rocky bottom).
  2. Provides a comprehensive classification scheme (Soil Taxonomy, Soil Survey Manual) for shallow water sediments.
  3. Could provide a major or missing dataset for submersed aquatic vegetation (SAV) restoration, estuarine protection, planning and management.

Subaqueous Soil Survey

Several states throughout the U.S. have begun the process of mapping and inventorying subaqueous soils. Within NRCS, each state is responsible for determining the priority given to subaqueous soil mapping, based on their importance in local conservation concerns.

Nitrogen Dynamics in Submerged Soil

The soil condition with submergence of water (continuous or intermittent) is submerged soil. Such soil occurs in rice fields, wetlands, estuaries and flood plains. Nitrogen dynamics is different as that from aerated soil conditions affecting soil microorganisms and nitrogen cycle. [1]

How are subaqueous soils mapped?

Traditional terrestrial soil mapping is conducted by a soil scientist trained to understand the interaction of soil-forming processes and soil-landscape relations. Mapping soils involves field work traversing the landscape and digging many holes to observe and classify the soil in various locations. Subaqueous soil mapping is performed in much the same way, except the mapper is in water. Instead of topographic maps and aerial photographs, subaqueous soil mapping uses bathymetric maps to identify underwater landscapes and landforms (a glossary of subaqueous landforms is available at: Glossary of Subaqueous Soil Landscape Terms). Shovels are replaced by augers with extendable shafts, and special tools such as peat corers and the vibracore to obtain soil samples.

Uses of Subaqueous Soil Maps

A major use of traditional soil surveys is to provide interpretations for various land uses and environmental planning. Interpretations for subaqueous soils are currently being developed for a variety of uses. As more areas are surveyed and more data collected, a wide array of soil interpretations are expected.

Related Research Articles

Pedology The study of soils in their natural environment

Pedology is the study of soils in their natural environment. It is one of two main branches of soil science, the other being edaphology. Pedology deals with pedogenesis, soil morphology, and soil classification, while edaphology studies the way soils influence plants, fungi, and other living things. The quantitative branch of pedology is called pedometrics.

Soil science The study of soil as a natural resource on the surface of the earth

Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils.

Wetland A land area that is permanently or seasonally saturated with water

A wetland is a distinct ecosystem that is flooded by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of functions, including water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, and support of plants and animals. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Whether any individual wetland performs these functions, and the degree to which it performs them, depends on characteristics of that wetland and the lands and waters near it. Methods for rapidly assessing these functions, wetland ecological health, and general wetland condition have been developed in many regions and have contributed to wetland conservation partly by raising public awareness of the functions and the ecosystem services some wetlands provide.

Pedogenesis is the process of soil formation as regulated by the effects of place, environment, and history. Biogeochemical processes act to both create and destroy order (anisotropy) within soils. These alterations lead to the development of layers, termed soil horizons, distinguished by differences in color, structure, texture, and chemistry. These features occur in patterns of soil type distribution, forming in response to differences in soil forming factors.

Salt marsh A coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides

A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated by dense stands of salt-tolerant plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh in trapping and binding sediments. Salt marshes play a large role in the aquatic food web and the delivery of nutrients to coastal waters. They also support terrestrial animals and provide coastal protection.

Shoal A natural landform that rises from the bed of a body of water to near the surface and is covered by unconsolidated material

In oceanography, geomorphology, and earth sciences, a shoal is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises from the bed of a body of water to near the surface. Often it refers to those submerged ridges, banks, or bars that rise near enough to the surface of a body of water as to constitute a danger to navigation. Shoals are also known as sandbanks, sandbars, or gravelbars. Two or more shoals that are either separated by shared troughs or interconnected by past or present sedimentary and hydrographic processes are referred to as a shoal complex.

Bioturbation The reworking of soils and sediments by organisms.

Bioturbation is defined as the reworking of soils and sediments by animals or plants. These include burrowing, ingestion and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a primary driver of biodiversity. The formal study of bioturbation began in the 1800s by Charles Darwin experimenting in his garden. The disruption of aquatic sediments and terrestrial soils through bioturbating activities provides significant ecosystem services. These include the alteration of nutrients in aquatic sediment and overlying water, shelter to other species in the form of burrows in terrestrial and water ecosystems, and soil production on land.

Entisol soil type

In USDA soil taxonomy, Entisols are defined as soils that do not show any profile development other than an A horizon. An entisol has no diagnostic horizons, and most are basically unaltered from their parent material, which can be unconsolidated sediment or rock. Entisols are the second most abundant soil order, occupying about 16% of the global ice-free land area.

Aquatic ecosystem An ecosystem in a body of water

An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.

Hydrosere A type of Plant Succession

A hydrosere is a plant succession which occurs in an area of fresh water such as in oxbow lakes and kettle lakes. In time, an area of open freshwater will naturally dry out, ultimately becoming woodland. During this change, a range of different landtypes such as swamp and marsh will succeed each other.

Gleysol type of wetland soil

A Gley is a wetland soil that, unless drained, is saturated with groundwater for long enough periods to develop a characteristic gleyic colour pattern. This pattern is essentially made up of reddish, brownish, or yellowish colours at surfaces of soil particles and/or in the upper soil horizons mixed with greyish/blueish colours inside the peds and/or deeper in the soil. Gleysols are also known as Gleyzems, meadow soils, Aqu-suborders of Entisols, Inceptisols and Mollisols, or as groundwater soils and hydro-morphic soils.

Yaquina Bay small bay partially within Newport, Oregon, United States

Yaquina Bay is a coastal estuarine community found in Newport, Oregon, United States. Yaquina Bay is a semi-enclosed body of water, approximately 8 km² (3.2 mi²) in area, with free connection to the Pacific Ocean, but also diluted with freshwater from the Yaquina River land drainage. The Bay is traversed by the Yaquina Bay Bridge. There are three small communities that border the Yaquina River and Bay; Newport, Toledo and Elk City. The Yaquina Bay in Newport is a popular tourist destination along the Pacific Coast Highway. It is also an important estuary for the ecology and economy of the area.

Great Bay (New Hampshire)

Great Bay is a tidal estuary located in Strafford and Rockingham counties in eastern New Hampshire, United States. The bay occupies over 6,000 acres (24 km2), not including its several tidal river tributaries. Its outlet is at Hilton Point in Dover, New Hampshire, where waters from the bay flow into the Piscataqua River, thence proceeding southeast to the Atlantic Ocean near Portsmouth. The northern end of the bay, near its outlet, is referred to as Little Bay.

Solum surface and subsurface layers of soil

The solum in soil science consists of the surface and subsoil layers that have undergone the same soil forming conditions. The base of the solum is the relatively unweathered parent material.

Groundwater-dependent ecosystems Ground water

Groundwater-Dependent Ecosystems are ecosystems that rely upon groundwater for their continued existence. Groundwater is water that has seeped down beneath Earth's surface and has come to reside within the pore spaces in soil and fractures in rock, this process can create water tables and aquifers, which are large storehouses for groundwater. An ecosystem is a community of living organisms interacting with the nonliving aspects of their environment. With a few exceptions, the interaction between various ecosystems and their respective groundwater is a vital yet poorly understood relationship, and their management is not nearly as advanced as in-stream ecosystems.

A stonelayer, or soil stonelayer, or stone line, is a three-dimensional subsurface layer, or soil horizon, dominated by coarse particles (>2mm), that generally follows (mimics) the surface topography. A stonelayer occupies the basal horizon of two-layered soil biomantles. A stonelayer may be one stone thick, and thus appear in a trench or pit as a "stone line," or it may be several stones thick and appear as a "stone zone". The gravel components of stonelayers may be compositionally variable, and while many are lithic clasts, often of quartzose composition, others may be metallic nodules and concretions of iron and manganese oxides, human artifacts, snail and clam shells, precious and semi-precious stones, or some combination thereof.

Marine habitats A habitat that supports marine life

Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea. A habitat is an ecological or environmental area inhabited by one or more living species. The marine environment supports many kinds of these habitats.

PCDitch is a dynamic aquatic ecosystem model used to study eutrophication effects in ditches. PCDitch models the nutrient fluxes in the water, the sediment and the vegetation, as well as the competition between different groups of vegetation. PCDitch is used both by scientists and water quality managers.

References

  1. "Nitrogen Transformations in Submergence Soils" (pdf).