Question: What industry did cargo ships converted for hauling slaves and Sydenham Teast have in common?

Context paragraphs:
Sydenham Teast: Sydenham Teast was a shipbuilder and shipowner based in Bristol, England, during the 18th and 19th centuries.  Amongst Teast's businesses was whaling, and an ivory and wood trade between England and Africa.  He constructed Redcliffe Parade in the 1770s, and was also involved in the slave trade, refitting the slaver "Hector" in 1776.  Towards the end of the eighteenth century, Teast became a significant figure in Bristol's trade to African communities.  He was not heavily invested in the slave trade

Sydenham Edwards: Sydenham Teast Edwards (1768 – 8 February 1819) was a natural history illustrator.

Amphibious cargo ship: Amphibious cargo ships were U.S. Navy ships designed specifically to carry troops, heavy equipment and supplies in support of amphibious assaults, and to provide naval gunfire support during those assaults.  A total of 108 of these ships were built between 1943 and 1945—which worked out to an average of one ship every eight days.  Six additional AKAs, featuring new and improved designs, were built in later years.They were originally called Attack Cargo Ships and designated AKA.  In 1969, they were renamed as Amphibious Cargo Ships and redesignated LKA.

Slave ship: Slave ships were large cargo ships specially converted for the purpose of transporting slaves.

Banner-class environmental research ship: The "Banner" class was a class of three environmental research ships converted from Camano class cargo ships by the United States Navy during the 1960s.  The class comprised three ships: "Banner" , "Pueblo" , and "Palm Beach" .  The ships were originally United States Army vessels which had been built in 1944.  Although officially classified as environmental research ships, the vessels were actually used as Signals intelligence gathering vessels, as part of the AGER program.

Northwest Steel: Northwest Steel was a small shipyard in Portland, Oregon.  Little is known of its background or owners, but during World War I the yard built cargo ships for the United States Shipping Board () .  Some 37 of the 46 ships ship built at Northwest Steel were the "West" boats, a series of -gross register ton (GRT) steel-hulled cargo ships built for the on the West Coast of the United States as part of the World War I war effort.

Charleston-class amphibious cargo ship: The "Charleston"-class amphibious cargo ships were a class of amphibious cargo ships in service with the United States Navy.  These ships served in Amphibious Readiness Groups between 1968 and 1994.  The ships were the last amphibious cargo ships built for the U.S. Navy, their role having been taken over by amphibious transport docks.

Camano-class cargo ship: The Camano class was a class of fourteen light cargo ships of the United States Navy.  The fifteen ships of the class were originally built as Design 381 coastal freighters or Design 427 coastal freighters and were converted to light cargo ships during 1949 and 1950 after acquisition by the United States Navy.

Algol-class vehicle cargo ship: The "Algol"-class vehicle cargo ships, also known as Fast Sealift Ships (FSS) or SL-7s, are currently the fastest cargo ships in the world, capable of speeds in excess of 33 kn .  Originally built in 1972 and 1973 as high-speed container ships known as SL-7's for Sea-Land Services, Inc., the ships' high operating costs limited their profitability.  All eight ships were acquired by the US Navy in 1981 and 1982, with the last ship converted, recommissioned and delivered to Military Sealift Command in 1986.  The conversion entailed the installation of four cranes, addition of roll on/roll off capability and a redesign of the cargo hold to better facilitate storage of vehicles.  Due largely to their high cost of operation, all fast sealift ships are kept in Reduced Operating Status, but can be activated and ready to sail in 96 hours.  All ships are named after bright stars in the night sky.

J. F. Duthie &amp; Company: J. F. Duthie & Company was a small shipyard in Seattle, Washington.  It was organized in 1911 and expanded in World War I to build cargo ships for the United States Shipping Board () .  In 1928 its name was changed to Wallace Bridge Company.  Some 27 of the 37 ships built at J. F. Duthie were the ""West" boats," a series of steel-hulled cargo ships built for the on the West Coast of the United States as part of the World War I war effort.

Supporting paragraphs: Sydenham Teast Slave ship
Answer: slave trade