WEBVTT 00:00:07.871 --> 00:00:11.610 This is Adam Skarke on the ship, we've just reached bottom with the ROV. 00:00:12.683 --> 00:00:17.880 And this hard bottom appears, initially, to look like an area of seepage. 00:00:19.554 --> 00:00:23.310 A cold seep is a location where we have fluid coming out of the seafloor. 00:00:23.510 --> 00:00:32.060 This can either be a gas, a natural gas like methane, or it can be a fluid like groundwater or brines that come out of the seafloor. 00:00:36.636 --> 00:00:39.970 This looks here like we've got a very small brine pool. 00:00:41.740 --> 00:00:51.170 These are highly dense, highly saline waters. They have a very high degree of dissolved salt in this water, 00:00:51.370 --> 00:01:00.890 and so it's much denser than the overlying seawater and it seeks low spots, and so you see pools and sometimes we see rivers of moving brine. 00:01:06.761 --> 00:01:15.230 We can now see pretty clearly the shimmering created by the density contrast in the water of that fluid coming out of the seafloor. 00:01:21.023 --> 00:01:26.640 I think we're moving up an extinct, what could be a relic brine waterfall here. 00:01:36.989 --> 00:01:42.100 So those mussels actually have symbionts, so they have bacteria that live within. 00:01:42.300 --> 00:01:50.990 And those bacteria can harvest the power from methane and other gases and provide nutrition to the mussel. 00:01:51.946 --> 00:01:56.090 So these are really important foundation species for these chemosynthetic environments. 00:02:03.092 --> 00:02:11.740 The Okeanos Explorer was one of the first ships to find a widespread methane gas seep along the Atlantic margin of the U.S. East Coast. 00:02:13.211 --> 00:02:17.740 We were keeping an eye out, seeing if we could find such plumes in the water column. 00:02:17.940 --> 00:02:23.980 And those were discovered in 2012, right off Virginia, we saw a major gas seep. 00:02:24.180 --> 00:02:26.910 And then within that cruise, we saw a couple more seeps farther north. 00:02:29.587 --> 00:02:37.650 With that impetus, we went back through and looked at the many years of collected sonar data from the Okeanos Explorer, 00:02:37.850 --> 00:02:42.170 and we ended up finding almost 700 sites of individual gas seepage. 00:02:44.450 --> 00:02:49.950 We can see if there's bubbles in the water column, or sonar anomalies within the water column or the sonar itself. 00:02:50.733 --> 00:02:51.140 And then it can also be used to find seeps. 00:03:01.305 --> 00:03:05.172 A lot of these chemosynthetic environments, you have a lot of abundance. 00:03:05.372 --> 00:03:08.850 So a lot of the deep-sea floor is flat and not a lot of life, 00:03:09.050 --> 00:03:14.260 but when you find these seeps, you see an incredible abundance, and that's exactly what we're seeing. 00:03:17.791 --> 00:03:19.820 Those are chemosynthetic tube worms. 00:03:20.020 --> 00:03:23.340 So those tube worms actually don't have guts anymore, 00:03:23.540 --> 00:03:31.180 they get all their nutrition by bacteria that live inside them and they use the energy they get from gases. 00:03:35.669 --> 00:03:41.050 Something that's quite remarkable is that chemosynthetic communities and this concept of chemosynthesis is relatively new. 00:03:41.250 --> 00:03:48.940 It was only in the 1970s that we discovered, in the deep sea, the first organisms that were chemosynthetic. 00:03:50.301 --> 00:03:56.820 So before that, it was presumed that all life was photosynthetic, that was plants using chlorophyll to transfer sunlight into energy 00:03:57.020 --> 00:03:59.310 and that being the basis of all food chains. 00:04:01.089 --> 00:04:05.630 It's only been within the past 50 years or so that we've understood that there are different organisms, 00:04:05.830 --> 00:04:11.660 particularly bacteria, that can synthesize chemicals in the deep sea in the complete absence of any sunlight, 00:04:11.860 --> 00:04:16.360 and that that can serve as the basis of a food chain for entire communities like we see here. 00:04:23.585 --> 00:04:27.680 The large carbonate rocks take quite awhile to grow to the size that they are. 00:04:27.880 --> 00:04:33.940 Those indicate that in many locations, we've had persistent seepage over many thousands of years, 00:04:34.140 --> 00:04:37.190 some dated back as far as 15,000 years in the Atlantic Ocean. 00:04:41.500 --> 00:04:44.050 It has been a truly spectacular dive today. 00:04:46.211 --> 00:04:48.640 It's days like these you can't believe you get paid to do this sort of thing.