Seabed mapping; Benthic habitats
NPR/NGS Radio Expeditions
30 Jul 1997
- Stellwagen Bank National Marine Sanctuary
- 42.35 -70.5
Stereo=1; Decoded MS stereo; Sennheiser MKH40 Cardioid Mid Mic and MKH30 Bidirectional Side Mic through Sonosax Preamp into Sony TCD3
NPR/NGS RADIO EXPEDITIONS
Stellwagen Bank NMS
Anthony Brooks interview with Page Valentine
NG 00:36 -bg ambi on ship -
1 : 14 PV (?) ( a bit faint, a low hum of engine in bg) this is the area we are mapping. Cape Cod is right here off the map -Cape Ann.
1:53 PV -I am Page Valentine I am with the US Geological Survey in Woods Hole, MA. We have a laboratory devoted to coastal and marine research there. At present we are working in Stellwagen Bank National Marine Sanctuary conducting the mapping of the sea bed and this image here shows you the entire area that we are mapping which includes an area that is somewhat bigger than the Sanctuary. We decided to square it off and do this whole area here. It is about 1100 square nautical miles. 2:32 This area has been completed. And we are using a sonar system mounted on a research vessel that's especially designed to do high speed surveys of the sea floor using a multi-beam sonar system so that we are looking at a -not at a single point as we go along but rather at a swath of the sea floor. And with it the swath is dependent on the water depth so we can image a path across the sea floor about 5 times the water depth. So in a hundred meters of water we can do 500 meters or half a kilometer swath with each pass (path?). So it is just a matter of surveying the entire area and then the sonar info gives us 2 products. One is the depth to the seabed which translates to a bathymetric map or a topographic map. Shows us all the features of the sea bed. And the other use of that data is to show us the nature of the sea floor based on the strength of the sound return. So the sound will come back stronger from hard seabed gravel, boulders, out cropping rocks, and have a weaker return from the mud bottoms. So in this image the mud bottoms are dark, or black. And the (radio chatter) rocky or sandy bottoms are grays -shades of gray or white. So we use both of these products, the topography and the back-scatter to help us make interpretive maps of the sea bed. And we also contour the depth data so we are going to have a new set of highly detailed bathymetric contour maps. 4:34
4:35 TB (radio chatter in bg) Did this kind of mapping exist before this project or is this -
PV -In this area?
PG -no this is this the first time this area has been mapped and this detailed. And we hope it will be the basis for future scientific research and for management -making management decisions regarding the Sanctuary. So we feel like if you don't know
what the environments are like, what their distributions are, what sort of organisms are living and what kinds of bottom types than you really can't conduct research or management in a useful way. 5: 18
5: 19 TB -So what kind of decisions can be made, what kind of management decisions can be made and management policy set using this kind of map.
5:30 PV -well, with regard to this Sanctuary the marine mammals, the whales are an important aspect of it. And so they are interested in where they are feeding, what sorts of bottom types they are feeding on. Where there prey is located. What their prey feeds on. There are certain areas of higher whale activity than others and it is important to know why they are there. If you know where the whales are and what they are doing then you can make decisions on protecting them better where they are most vulnerable, that sort of thing. Another aspect of this is fisheries research and the fishery in general is in having hard times in New England and new issues are coming into focus, for instance the issue of habitat destruction, fishing in gear (?) and that sort of thing so our research in the Sanctuary will maybe through some light on how fishing gear (?) effects the bottom.
6:44 TB -and what have you seen so far?
PV -well, we have done additional work on Georges Bank which is farther off shore. In fact I have another project where we are focusing just on that aspect of how fishing gear effects the habitats and alters it. And we are starting to do similar research on Stellwagen, and basically the bottom gear that moves along the bottom -the scallop tredges and the outer trolls. They -when they are towed in gravel areas where there is often a lot of attached organisms -sponges and anemones and smaller crustaceans that live amongst the gravel. They tend to knock those species off the gravel and remove a lot of the 3 dimensional aspects of the bottom. and on Georges Bank the assemblage which lives in the disturbed areas is much different than the assemblage that lives in the undisturbed areas.
7:47 -TB -just for the layman ... when you said the assemblage what are you referring too?
7: 51 PV -well I mean the group of biological organisms that live there -all of the different types of animals that live on the bottom or attached to the bottom or in the bottom. so basically the gear is towed through the gravel, knocks the pieces of gravel together as it is passing over. Knocks these organisms off and it ends up looking like beach gravel. Where as in the pristine state there is usually a lot of attached fauna and associated species. So one of the implications of that are the moving cover for
juvenile fish other than moving prey for fish just what are the -we assume that it is
detrimental but we really haven't proven that yet. But it is altering the bottom that
much we can say. So we can use -once we have our maps made and know in detail
where all the different bottom types are then we can use the Sanctuary as a laboratory for conducting this kind of research 8:59
9: 00 TB -and talk about how that fits in -one of the reasons we are doing this series on NMS is bc it has been 25 years since the first one was established -how is this consistent with that mandate and sort of carrying out what these sanctuaries are supposed to do as sort of living laboratories in a sense.
9:28 PV -Well, this particular Sanctuary there was an impetus to designate it as I recall bc there was a move afoot to do sand and gravel mining on the Sanctuary. Stellwagen Bank, one of the main features of the Sanctuary is covered with sand and gravel and it ws known marine mammal habitat. I think that was the impetus to set this area aside to preserve it for the marine mammals and to also preserve it as a fishing -recreational and commercial fishing area that would not be impacted by any new mutes -whether it is mining or the laying of pipelines or any new conceivable use -so, it is an area that has special attributes which is from what I know, what Sanctuaries have to have to be designated as special places. So, now we have this special place, and these kinds of places -when you have a place like this there is a natural focus of research activities and support from Sanctuary personnel, so, it sort of evolves into a place where activity is concentrated and it becomes an area of-or a laboratory for marine research. By the fact that many people are interested in it. And it is probably easier to get them interested in it bc it has a special status. 11: 19
11:20 TB -from what you see one of the issues that I have been talking about on this boat today is that whole issue of bottom trawling and the effect that it has and how it might or might not impact in a negative way in the long term. From what you see-you refer to this but expand on it a little bit -do we know definitively that that this is damaging for the long term -the habitat environment for these species down there or do we need to look at it more?
12:00 PV -well, we know that it changes the bottom I will put it that way. And we know that it changes the grouping of species that live in that area. It eliminates some. We assume that has an effect on the fishery. We really haven't proven that. A colleague of mine, a colleague that I work with on Georges Bank, he and I are working together on this issue and he is probably more knowledgeable than I am about the details .... There is a tendency to think that when you see a change it has to have a bad effect. But, we really don't know that yet. That is a major question since the fisheries and the fishery service now has to pay attention to fishery habitat and where an essential habitat is and to try and identify it and manage it in a certain way. I wouldn't want to say that we have definitively come to that conclusion but we are working on it.
TB -and no hunches?
13 :20 PV -well, we know that on Georges Bank that juvenile cod become juveniles in the water column before they settle to the bottom. they float around as eggs and
larvae and develop into small fish. And are 5 or 6 cent. Long before they actually go to the bottom to spend the rest of their lives there, and on Georges Bank it is pretty well proven that they do better in the gravel then in the sand. Presumably they can find cover -refuge from predators in the gravel and there might be a food issue there too. So we know the gravel which is very extensive on Georges Bank is an important habitat for juvenile cod so we know that -so an alteration of the gravel might effect that, but we don't know that for sure. There is also the issue of -there is also a scallop fishery out there and it appears that the scallops may do better in a some what disturbed habitat in pristine habitat -and we are following up on that one too. so this kind of info allows managers to make decisions on how the bottom is going to be utilized and that is sort of a new approach. They really didn't have this kind of info before but now they have the info -where they will potentially be allowed to use the info and say alright, we are going to close this area for instance when the cod are in this area on this bottom growing up for several months or whatever. They will have the ability to do that if they want to.
15: 16 tb -could you sort of give an example by looking at the map we are looking at which to me looks sort of like a lunar landscape what we are looking at right now -I mean how might they be able to look at this and sort of make a decision about
managing the resource?
15:35 PV -well, this is a sun illuminated (?) topographic map so it has a 3D aspect to it. You can see the features very clearly. There are 2 major banks here. One is Stellwagen Bank and the other is leffer's ledge. They are both fishing areas. they are
both shallow and sandy. And
15: 57 -TB -so this is Stellwagen Bank -it just stands in sort of a leaf _
PV -this is Stellwagen right here -it is very steep edge on the western side -this is Stellwagen basin which is a muddy area which supports a whole different fishery then the bank itself so if you look at this -this is the back scatter (??) which is a crude one (bg ambi: opening map) but you can see the basin areas. The deep areas are covered with mud shown here in dark areas. So you see there are lots of small bases up in this area here where there is a lot of relief So these areas are fished for different kinds of fish than these sandy areas on the bank here. Sandy and rocky areas. So right now they know that fisherman find different species in different geographic areas. But until now they were not really related in detail to a bottom type. The fisherman know if they are fishing on mud or sand but one of the things these images will do is show the actually extent of these habitats. And that extent would be related to the presence of certain species they might want to manage ... we are also interested in the geological aspects of this. For instance these features here -this is an area here -we have 18 quadrangles in this area and we have to treat it in a piece meal fashion bc it is such a large area. So area 5 is this one right here (radio talk in bg). You will see these wedge shaped deposits long here -these are sand deposits created by northeasters.
Our major storms here are from the north east bc the area is protected by land from
most directions. It is open to the north east and the entire Gulf of Maine so when major storm from the north east very large waves impact the bank and coast line. They are basically eroding sand from the seaward edge of the bank. Moving across the bank to the Stellwagen basin on the western side. In fact the bank probably protects the coast line in a way bc it is shallow. It is about 30 meters and the storm waves extort a lot of energy moving across the bank which they would normally expend on the coast line. So (radio chatter in bg -can't understand PV' s words) ... as the sand is removed .... so we are interested in determining what directions sediment is moving in what the texture is. In this case the texture becomes finer and finer. .. (more radio chatter in bg) TALK ABOUT DIFFERENT SAND TEXTURES AND GRAVEL MOVING AROUND ... .in future eons this will totally be gone and that habitat will be gone. 19:41 on a short term basis, which can happen every year but sometimes don't, these storms can alter the habitat. For instance if you had a gravel habitat that was well established a large storm could just smother it by sand and it would be gone and by contrast you can uncover gravel and it would be open for colonization so the dynamic nature of the top of the bank really effects the distribution of the habitats and where the organisms live. 20: 19. These for instance -it is hard to see here but these are fine sand this feature here -and you can see that little texture that is aligned in this direction which is consistent with transport. Now these are sand waves, they are hard to see here, and in the troths of those sand waves are shell deposits ... MORE ON THESE DEPOSITS ... there is a large aggregation of broken shell habitat in here which can be utilized by say -juvenile fish species and a major storm could just wipe that out.
TB -so it sounds like what you are saying there are big chunks of this that are fragile, tenuous at best
21 :22 PV -oh yeah. And especially since in this case when they are effected by _ actually the tidal currents are very weak on Stellwagen Bank so that they really don't have an effect on the sediment movement it is the major storms which do it. So that hasn't been appreciated until now. So say for instance say you had an instance where scallop larvae are settling in on the bottom, typically when they reach the bottom they attach to a piece of shell or a little piece of sand grain and they live there young, their early life attached to the bottom and then they drop that attachment and they can move around ... MORE ON EFFECTS OF SCALLOPS IN SAND -AND EFFECTS OF STORM ON SCALLOP
22:45 TB -as someone who does this kind of work is it surprising that it has taken this long to get this kind of detail from something that is so much a part of our world
22:59 PV -well, it is very difficult to work at sea bc you can't see what you are doing basically. It is sort of like mapping a land from a helicopter at night with a search light. That sort of thing. On land you can take an area photograph and right away you know a lot of what is going on. Until recently it was done just by using samplers
on the bottom. now we have video cameras. We don't do any sampling w/o seeing what we are sampling. We do a lot of bottom video and photography. And now we have these sonar systems that can map large areas of the sea floor very rapidly. But it takes a lot of work and we will probably never be able to map the whole continental shelf in this detail bc it is just so time consuming. So the strategy is to pick areas that are important for one reason or another and concentrate on them so we can learn about processes, ocean floor processes, analogous to other areas where we don't have that kind of detail and can be applied there. We have projects all up and down the east coast that are focusing on different areas for different reasons. And the sanctuary is one of our more active projects bc it involves biologists, geologists, physical oceanographers and of course the Sanctuary policy people, and of course the public is interested in the Sanctuary bc there is so much activity out here with commercial fishing and the whale watching industry and recreational fishing 24: 59
TB -well good. thank you
24:53 PV -let me show you one last thing -as part of this project we, the Sanctuary boundary goes right along here I don't show it with this image. But the MA bay dump site is right here where they deposit
TB -is that the outflow pipe?
PV -no, no the outflow pipe is closer to shore. But this is where they deposit dredge materials from harbors and it is right on the Sanctuary boundaries. So when we when we were doing this project we decided, well, we will image that area too and this is the map we produced showing the MASS Bay disposal site. It shows you an application of this data published application of this data (bg ambi -pulling map out) so this site is managed by the engineers and by the EPA in an on going fashion. So we are providing this map to show where all the features are in this dump site. Now, this is the Sanctuary boundary right here so everything on this side is in the Sanctuary. They had to move the dump site when the Sanctuary was designated to keep it outside the Sanctuary and this is the area of the dump site right now. And dumping is occurring right here. So you can see -
TB -you can see it very clearly. It looks like a mound of dirt
26:33 PV -right, right. It is about 5 to 8 meters higher than the surrounding very flat seabed. A former mound was over here which has been used for a number of years
and has been degraded here. But this is the present mound. It has been used for about 10 years. So, now with this kind of an image, and I will show you (bg ambi -he
reaches back to get map) this is the topographic image that will show some relief.
This is the back scatter image that shows the kinds of sea bed there. Or the features of a sea bed in terms of their texture. And one is normal and one is reversed. So in this case, this is the dump site here, this is the mound. All of these are individual deposits from the barges that dump the material. And this is a period over many years. And you can see that as the barges approach the dump site they start dumping and material dribbles out, shown in a streaky fashion the actual track of the barge. 27:44
TB -and they are supposed to make it into the circle but
27:50 PV -now they have a buoy here and they are very good about finding the buoy ... it is easier to find a buoy than to navigate in bad weather. Now these dark features here are piles of rocks that were blasted out of harbor for the Ted Williams tunnel. They had a lot of what they called fresh blasted rock and they decided to put it ........on the edge of the bank ... now inhabited by lobsters ....had a positive effect in that regard ... a case where they created new habitat and it had positive effect ... these maps will provide them with info that will help make their decisions .... kind if an example ...
30: 15 TB -a nice example too of the hand of man actually doing something nice and natural to the environment
30:23 PV -well, we are going to have to use the off shore areas for many things including depositing our dredge material so it is a good idea to know a lot about it so we can make the best decisions on where to do these things
30:56 room ambi , 31 :09 folding of maps
31 :39 quiet room ambi (w/o folding in bg) end 32:03
Chuck -what are the striations?
32:32 PV -those are the track lines of the ships -we edit a lot of these things out _ you can see this is the way the ship went -there is always a grain to your survey.
34: 10 ambi on deck of the ship
*34:35 ambi of crane?
35:53 -ok going ahead and start up') -coming up!
*35:57 -good crane ambi
36:51 -get any slack here?
SOME TALK ABOUT WORKING THE CRANE (hard to hear)
some chatter, but good ambi of crane
38:08 I'm a going to go up for the tri-point
38:41 ( faint)-so are you guys doing another diver? -no!
39:30 -I will just put a line on that to pull it over
39:40 -yeah. We are going to take up the trawl (not on mike)
40: 00 -new crane sound
40: 10 -ok, you can run it through there -you can just drive it right through it
41 :03 STOP DOWN
notes from CHUCK: ambi at end out of the wheel house should be enough to cover out of the helm end ambi is tail end of bringing up the ROV from the final dive the day