Ampelisca mississippiana is a small (less than 6 mm long), colorless amphipod that was discovered only recently from sediment samples taken in the Mississippi Canyon of the Northern Gulf of Mexico (Soliman & Wicksten 2007). At the head of the canyon, at a depth of about 480 m, these crustaceans were found to be the dominant benthic animals forming dense mats of up to 12,000 individuals per m2 in the muddy ocean floor (Soliman & Wicksten 2007).
Like other ampeliscid amphipods, Ampelisca mississippiana probably feed on detritus and build tubes in the sediment. High density mats of tube-dwelling organisms are thought to be of great ecological significance because they stabilize the soft mud while capturing particulate matter flowing from the continental shelf to the deeper regions of the gulf (Soliman & Wicksten 2007). It has also been suggested that ampeliscid tube mats may have a positive effect on certain fish populations by reducing the accumulation of silt in the water, by facilitating the settlement of fish larvae, and by deterring predation (Mackenzie et al. 2006).
Ampelisca mississippiana populations may be threatened by the Gulf of Mexico oil slick resulting from the Deep Water Horizon Incident of 20 April 2010 (Robertson & Krauss 2010). By mid-May 2010, aerial views show the oil within 100 km of the type locality at the head of the Mississippi Canyon (see Map). The effects of oil spills and associated remediation efforts on deep ocean communities are poorly understood (Biella 2010).