Horseshoe crabs are usually found crawling on the bottom but they sometimes swim by flapping their gills, as seen in this video. We see this swimming behavior in a few different circumstances. They may swim to move through the water more quickly than while crawling. The horseshoe crabs at the Alabama Aquarium are often hand-fed at the water’s surface, held mouth-up and then gently released. Sometimes, as they’re released, they swim. Sometimes, if a horseshoe crab crawls up an incline, if the incline gets steep, they may fall backwards (whether this is deliberate, we’re not sure) and swim until they descend to the bottom. The bowl or boat shape of their bodies provides a broad surface area that causes them to sink slower, so they can “glide” downwards.

@@DISeaLabawesome response, thank you! i do recall reading about their swimming response when encountering a steep enough slope that they fall backwards, swimming for a momemt and gliding down to rest before performing a righting maneuver. something about the engineering of wildlife barriers on a water inlet. do you have any papers on the subject of their swimming behaviour at sea? as far as i know, it's thought the flapping may be used when traveling longer distances and the shallow waters, but from what ive found theres a gap in research in terms of observational studies outsode of the estuarine environment. thank you again! loved the response

Michael, I'll share your question and get back to you.

From Kara: I wasn't on the Gulf Coast when the oil spill occurred, but scientists who did studies right after the spill found that there was a pulse of "marine snow" deposited on the seafloor, probably caused by the oil from the spill forming globs with other stuff in the water and quickly sinking to the bottom. Sediment microbes chowed down on this stuff, which used up the oxygen and thinned the oxygenated layer in sediments. And the spill did affect the animal communities living in sediments, most noticeably in the area right around the wellhead; the communities were less diverse and more dominated by species that are known to be tolerant to stressful conditions. Sediments are in a long process of recovery from DWH. One of the problems with studying the effects of DWH is that there isn't a lot of data about these ecosystems from before the spill, so it's hard to figure out how things may have changed afterward because we don't have much to compare it to. This is why it's so important to collect data on these ecosystems now, so we can understand how they change in the future.