Ocean dredging was an oceanography technique introduced in the nineteenth century and developed by naturalist Edward Forbes. This form of dredging removes substrate and fauna specifically from the marine environment. Ocean dredging techniques were used on the HMS Challenger expeditions as a way to sample marine sediment and organisms. [1] [2]
Edward Forbes would lay out the dredged material on the deck to examine, preserve and study it. The practice was chronicled in a remembrance of Forbes by William Jerdan in his 1866 book Men I Have Known. [3]
Ocean dredging was a common sampling technique used on the Challenger expedition. [4] The expedition, led by oceanographer John Murray and chief scientist Charles Wyville Thomson, set sail in 1872 and returned to England in 1876. [4] [2] The ship was equipped with 34 dredges and 20 dredge nets, completing 133 dredges at 111 stations during the 4 year long expedition. [5] [4] [1] Thomson and Murray detail the following instructions for surveying dredged organisms:
"Examine mud brought up by dredge from different depths for living diatoms; examine also for the same purpose the stomachs of Salpae and other marine animals." [5]
The expedition successfully dredged, collected, and preserved marine sediments, plants, algae, and invertebrates. [1] The Challenger expedition is attributed to discovering approximately 4,700 new marine species and expanding the current knowledge of ocean sediments and geology. [2] [4] [1]
Ocean dredging can negatively affect benthic ecosystems. [7] When dredging equipment is moved along the seafloor, habitat-forming epifauna is damaged or removed. [8] As emergent corals, sponges, and seagrasses are damaged there is less habitat complexity for juvenile fishes to find protection in. [8] Dredging also removes the sand waves in which juvenile Atlantic cod settle. [8]
The top 2–6 cm of marine substrate is disturbed during dredging, which can have negative impacts on deposit feeders, nutrient flux, and burrowing species. [9] Dredging is often banned or highly restricted within marine protected areas in order to protect recovering ecosystems. [8]
Dredging in the marine environment can be carried out with a variety of equipment, depending on the purpose of the dredge. If the purpose is to remove sand or redistribute sediment, then a dredge drag head attached to a trailing suction hopper dredger ship is used. [10] A fishing dredge (also known as a scallop dredge) is used for collecting edible species of oysters, mussels, scallops, clams, and crabs from the seafloor. [11]
Oceanography, also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics; plate tectonics and the geology of the sea floor; and fluxes of various chemical substances and physical properties within the ocean and across its boundaries. These diverse topics reflect multiple disciplines that oceanographers utilize to glean further knowledge of the world ocean, including astronomy, biology, chemistry, climatology, geography, geology, hydrology, meteorology and physics. Paleoceanography studies the history of the oceans in the geologic past. An oceanographer is a person who studies many matters concerned with oceans, including marine geology, physics, chemistry and biology.
The Challenger expedition of 1872–1876 was a scientific programme that made many discoveries to lay the foundation of oceanography. The expedition was named after the naval vessel that undertook the trip, HMS Challenger.
Vice-Admiral Sir George Strong Nares was a Royal Navy officer and Arctic explorer. He commanded the Challenger Expedition, and the British Arctic Expedition. He was highly thought of as a leader and scientific explorer. In later life he worked for the Board of Trade and as Acting Conservator of the River Mersey.
Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different species of fishes or sometimes targeted species. Trawls are often called towed gear or dragged gear.
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "the depths." Organisms living in this zone are called benthos and include microorganisms as well as larger invertebrates, such as crustaceans and polychaetes. Organisms here generally live in close relationship with the substrate and many are permanently attached to the bottom. The benthic boundary layer, which includes the bottom layer of water and the uppermost layer of sediment directly influenced by the overlying water, is an integral part of the benthic zone, as it greatly influences the biological activity that takes place there. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud.
Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing dams, dikes, and other controls for streams and shorelines; and recovering valuable mineral deposits or marine life having commercial value. In all but a few situations the excavation is undertaken by a specialist floating plant, known as a dredger.
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3,000 metres (9,800 ft) and 6,000 metres (20,000 ft). Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They are among the flattest, smoothest, and least explored regions on Earth. Abyssal plains are key geologic elements of oceanic basins.
Sir Charles Wyville Thomson was a Scottish natural historian and marine zoologist. He served as the chief scientist on the Challenger expedition; his work there revolutionized oceanography and led to his knighthood.
Bottom trawling is trawling along the seafloor. It is also referred to as "dragging". The scientific community divides bottom trawling into benthic trawling and demersal trawling. Benthic trawling is towing a net at the very bottom of the ocean and demersal trawling is towing a net just above the benthic zone. Bottom trawling can be contrasted with midwater trawling, where a net is towed higher in the water column. Midwater trawling catches pelagic fish such as anchovies and mackerel, whereas bottom trawling targets both bottom-living fish (groundfish) and semi-pelagic species such as cod, squid, shrimp, and rockfish.
The seabed is the bottom of the ocean. All floors of the ocean are known as 'seabeds'.
HMS Challenger was a steam-assisted Royal Navy Pearl-class corvette launched on 13 February 1858 at the Woolwich Dockyard. She was the flagship of the Australia Station between 1866 and 1870.
Biological oceanography is the study of how organisms affect and are affected by the physics, chemistry, and geology of the oceanographic system. Biological oceanography may also be referred to as ocean ecology, in which the root word of ecology is Oikos (oικoσ), meaning ‘house’ or ‘habitat’ in Greek. With that in mind, it is of no surprise then that the main focus of biological oceanography is on the microorganisms within the ocean; looking at how they are affected by their environment and how that affects larger marine creatures and their ecosystem. Biological oceanography is similar to marine biology, but is different because of the perspective used to study the ocean. Biological oceanography takes a bottom-up approach, while marine biology studies the ocean from a top-down perspective. Biological oceanography mainly focuses on the ecosystem of the ocean with an emphasis on plankton: their diversity ; their productivity and how that plays a role in the global carbon cycle; and their distribution.
Janolus is a genus of small to large sea slugs, or more accurately nudibranchs, marine gastropod mollusks, in the family Janolidae. The name Janolus is derived from the two-headed god Janus, in ancient Roman mythology.
Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea. Additional deposits come from marine organisms and chemical precipitation in seawater, as well as from underwater volcanoes and meteorite debris.
Thomas Henry Tizard was an English oceanographer, hydrographic surveyor, and navigator.
A fishing dredge, also known as a scallop dredge or oyster dredge, is a kind of dredge which is towed along the bottom of the sea by a fishing boat in order to collect a targeted edible bottom-dwelling species. The gear is used to fish for scallops, oysters and other species of clams, crabs, and sea cucumber. The dredge is then winched up into the boat and emptied. Dredges are also used in connection with the work of the naturalist in marine biology, notably on the Challenger Expedition.
Acoustic seabed classification is the partitioning of a seabed acoustic image into discrete physical entities or classes. This is a particularly active area of development in the field of seabed mapping, marine geophysics, underwater acoustics and benthic habitat mapping. Seabed classification is one route to characterizing the seabed and its habitats. Seabed characterization makes the link between the classified regions and the seabed physical, geological, chemical or biological properties. Acoustic seabed classification is possible using a wide range of acoustic imaging systems including multibeam echosounders, sidescan sonar, single-beam echosounders, interferometric systems and sub-bottom profilers. Seabed classification based on acoustic properties can be divided into two main categories; surficial seabed classification and sub-surface seabed classification. Sub-surface imaging technologies use lower frequency sound to provide higher penetration, whereas surficial imaging technologies provide higher resolution imagery by utilizing higher frequencies.
Enypniastes is a genus of deep-sea sea cucumber. It is monotypic, being represented by the single species Enypniastes eximia. Due to its unique appearance, the species has been dubbed the headless chicken fish, headless chicken monster, and the Spanish dancer. It is also known as the swimming sea cucumber, and some are called the pink see-through fantasia.
Eulima cylindrata is a species of sea snail, it is a marine gastropod mollusk in the family Eulimidae. The species is one of a number within the genus Eulima.
Collodaria is a unicellular order under the phylum Radiozoa and the infrakingdom Rhizaria. Like most of the Radiolaria taxonomy, Collodaria was first described by Ernst Haeckel, a German scholar who published three volumes of manuscript describing the extensive samples of Radiolaria collected by the voyage of HMS Challenger. Recent molecular phylogenetic studies concluded that there are Collodaria contains three families, Sphaerozodae, Collosphaeridae, and Collophidilidae.
