NPR/NGS Radio Expeditions
28 Mar 1995
- Panama City
- 8.98333 -79.51667
- SONY TCD-D7
Panama - Dar1en
Tony Coates and Jeremy Jackson in the Lab
00:02 ac: this is the laboratory of tony coates back in Panama city it's a good size room, with a tile floor, air condition --not at all like the field, there's a very orderly chart -or map case over on the wall and several filing cases labeled, and tony's samples from the field are bagged here. they are ready to be shipped off to the university of Michigan? tc: right.
tc: that's because they are micro-samples. if they were macro they would go to GIDA at the lab at Nouse.
ac: and, um, and then there are tables with some of tony's field books and notes and there is a sink over there -Zania, his lab assistant is here.
tc: and that's a stack of special cases that contain all of the geological and topographic maps of Panama and all of the surrounding countries that we have been or shortly go to, so it covers most of central America.
ac: and here are your field notes laid out.
tc: um, we are going in two directions with information that we brought in the field notebooks. one is to get them into the data base -a sample of which is here, and you can see there's a list of numbers down the side, and those numbers key to dates collected -the sea is caribbean versus pacific, and then country, location in more precise detail, and then you can see a description, whether it's equivalent to some other place this is 1.2 NW of etc., and then the actual latitude and longitude. and that's particularly important because this is all geographic information about where the sample comes from, and Zania will utilize this, particularly this latitude longitude operation, to digitize it on to a map. and if you look through at the other office there, there's a digitizing pad you see it there on the table¬
ac: oh yes
tc: and Zania will follow the outline of any area that we are stUdying to make a detailed map. she will create the map that she can project on to the screen there. and then, if she digitizes each of the localities then at some future date we can call for all the specimens from the dariendara 4 million years old, and the program would simply select from the data base those samples plot them using those latitude and longitude on to the map already digitize and anyone could have a map of any of the particular samples or even the particular fossils -a species from that have been isolated from the sample you could then for us -you remember we were talking about strong binned gastropods can we have a map of strombina alex chadwickensis from anywhere that we have mapped. and it would just plan out a locality map of that one species. or, all of the mollusks or which mollusks are only on the pacific side. so it's just a simple way of being able to ask questions to manipulate the data for biogeographic and evolutionary information. so that number keys across into all of that. then the -that's the locality data base. there is also the same -those same set of numbers can key you into what has happened to the sample -¬who's got it, what have they done with it, what was in it, etc. which maybe splits of it, one was sent -we had a microsample that was sent to Michigan, but at that same location we got ten bags of bulk sample; four of which are being processed for mollusks in basel, and two are being processed for briazoa in Panama, and that data base will keep track of who's got it, what they found in it, and that sort of geologic information if you like. That's one aspect of this operation. Now, we described in the field that my job that my job was to make a three dimensional picture of the geology of the strata, so that these faunas can be identified in time slices. The other aspect of what Zania and I do in this laboratory is to translate that information into graphic form. This is chronological information now as opposed to geographic and processing information. Now, I will come in with this book, which is notes that you saw me writing in the field. this is actually the transcribed notes. you remember that i mentioned that I always write them up so that if you loose the field book you don't loose the whole summer's work. What i will usually do from the notebook is create quickly on a piece of graph paper a vertical section with the samples located each with their numbers, and then zania and i will then go over that because she will spot -i've forgotten something, or this....once she is happy with that, she will take it and develop, through a program, this section. zania why don't you come for a second and tell alex what this is relative to that. this is a software program called ¬
6:14 zania: rockware. this is a command pile, and you write down in here all of the samples --where exactly they are according to a format, for example this one is 15 meters per page. and then, you do that according to how deep it is -the section¬
6:33 tc: you see, i may have given her a section that is 3000 meters thick, which we have done on some occasions. or it may be 200 meters thick, or 50 meters thick. so she will make a judgement that, for this, we need a relatively large scale document versus small.
6:51 zania: and, then with the command file you'll say if this -the composition of the strata, and then you will just write it down with all of the description and what the --it will be the interbeds that we have. and where exactly they are, and then from here you will produce the ¬
7:15 tc: this graph. so, in essence she has a list that she and i have already talked about that is a complete list of all of the rock types we normally encounter, ok. so when she reads what i have written in the notes there she will write in -oh for that 10 feet it was this kind of lithology. lithology is just a geological term for rock type. and then i might have said -coral reef bedded or it had pinnars in it, or it had plantic foraminifera or it had shells, or corals. so it will overlay on the basic rock description patterns that show different kinds of organic content fossil content, etc. and then, i will have put a symbol. a triangle for example is a paleomagnetic sample, and a square is a fossil sample. and she will locate at each of these intervals, um' where those are. you can see 0 on this one for example we've got paleomagnetic samples and regular samples in rocks as they change in time.
8:22 ac: let me ask you -ok, as an example here -you have this being 9 meters thick, does that mean that this is ~n actual representation of 9 meters of (tc: exactly) sediment that you went through at some particular ¬in a particular location (tc: right) and in that you found all the stuff that's outlined here.
8:44 tc: that's right. as you can see that's from fish hole in bastimentus, which is in Borcus, and these are the descriptions of the rocks and some of my notes, which she has put in, and this is a change here
8:56 ac: and is this a description of a sediment that is similar to the sediment that we have been looking through ... i don't mean it's similar in geologic-but is this same process you found a sediment that you (tc: absolutely) wanted to look at at this site and it was 9 meters thick and you went through it from top to bottom ¬
9:16 tc: and we oriented it -'cause if it's dipping like that -dipping at an angel along the river i have to correct for the fact that the distance along the river that i see is in fact a diagonal through it and i will recalculate the true thickness, and this is the actual thickness in the layer -the true thickness of the layer
9:35 ac: how big an area is this that you are representing. have you taken out a segment that is 7 meters deep and ¬
tc: the vertical is the true thickness ac: yes tc: the fact that this is a thin column and then a thick column and then a thin column. i am trying to express the way it weathers. do you remember some beds stuck out as ledges and others were recessed because they were so ¬
10:03 tc: so, if a geologist wanted to go back to the location and check what i have been doing or add to it, i would give him or her that section and it's this weathering profile that will be the most obvious thing that will strike the person when they go back to the field and that will help them locate where they were with respect to this particular 9 meters. so it's a way of describing the geological properties which is a key to recognizing my vertical section in the field.
10:37 ac: the 9 meters represented here or the 7 represented there, could you say to a layman like myself what age does this represent what is the date of this meter here and the date of this meter here.
tc: that all depends where we are. you remember when we were out at the darien we talked about an impressive pile of well-bedded sediments that look a lot of time -and i said they were very laminated and were deposited that could have been a hundred thousand years. this could be a similar thickness of 9 meters of slow growing or slowly depositing deeper water mud and it might represent 6 million years
ac: and that you can determine by ¬
tc: the way we determine that are these sequence of samples through here... when the floating plankton are sent to our specialist, bill bergrin at Woods Hole and he tells us what age they are, he will probably be able to say oh, that's late upper micoen -it's btwn. 2 & 3.4 million years. that's a typical date if we got good material ........ac: 2 & 3.4 million ¬tc: that's 1.4 million years. but then i will come along with don McNeal from Miami and we will do all of these paleomagnetic samples and if ¬remember we discussed in the field that these samples recapture the orientation of the magnetic field... and for reasons that are not well understood for some periods of time in the past they are like they are today -they are normal polarity. the north pole is were the present north pole is, and for some erratic and changing periods of time the polarity is reversed. so that in effect today's south pole would now be today's/would now have been the past north pole. now that change we know very precisely
in time because it's recorded on the floor of the ocean. and as the oceans spread out -as the magmar in the center of the ocean comes to the surface and cools, all of the little crystals, the magnitude crystals, that are orient floating around in it, orient themselves just like iron filings around a magnet to the Earth's magnetic field. Once the rock is frozen or cooled to solidity they are frozen in there. then if the rock moves, they will change with that movement, but they will never re-orient to the later field of the Earth. What we find is that some come up and are frozen and they're normally polarized, and then a little while later more comes up and they are reversed. and so if this vertical 9 meters that we are looking on
in this section is 8 million years old and happens to be this 8 million years old -and i brought you another chart here, and you can see we have a column along the side of that kicked off (?) in 1 1/2 inch intervals: 5, 4, 3, 2, 1 million years, and you can see in that 5 million years there are
....11 reversals of the Earth's magnetic field. NOw, if I can tell if the plantlike foraminifera can tell that we're in say, 1 to 2 million years, and you have a reversal here and a normal here, and a reversal here on this column you can very precisely say, oh it's that normal, this reverse, and that normal. therefore it is 2.4 million years old. so the combination of the reversal -magnetic reversal stratigraphy -superimposed upon the biological dating can get you extreme precision, and that's what we are aiming to do.
14:47 ac: so suppose i came to you for some reason and said, tony i need a map of what Panama, the isthmus of Panama, what the region looked like 2.4 million years ago. could you ¬
15:02 tc: that i could do with less precision. um, i think zania we have one available to show alex. ah¬
15:10 ac: but with the data that you are gathering, if -and of course no one is asking you to do this for that -this is just as an exercise. and no one is coming to you to say, but with the data that you are gathering if some one did say, i need a map of 2.4 million years ago or 2.3 -and here is a million dollars to go gather the rest of the data that you are going to need -can you do that kind of thing?
15:34 tc: yes, we can. but we can't do it (ac: look at that, look at that) with quite the precision that um, that i can tell you how old that
particular rock is vertically. and it is somewhat difficult to translate that into reality for a lay person. this is a record of rock in a single place and i can get information out of it, it tells me that at this place, in that rock, it was that old. now what you are asking me to do here is to look at all rocks across a single time plane (ac: right, and obviously they) and tell me what's happening at that,and that's much more difficult to do, because i don't have a record for all of those places.
16:18 ac: you are connecting the dots, and the question is how many dots do you have.
tc: right, exactly. and if i have a lot of dots i give you a very good map, if i have a few dots i give you an increasingly vague and less certain map. so what we try to do is to do a map that's at the limit of the certainty.
16:35 ac: let me just say -you have just laid out three sheets of paper here, and outlined on them is a kind of tracing of the current isthmus of panama and overlaid on that is a series of a kind of dots and shaded areas that i gather represent the past formation of the isthmus of Panama.
17:02 tc: yes, the striped lines define are my best guess at the existing land of the period. and the dotted area that is sort of following the present outline of the isthmus is the area where shelf sediments were being deposited. and for that, those would be sediments less than 200 meters deep. and so, what you can see is that here, in the first chart, which is in the middle Miocene about 15 million years ago, there is an archipelago of islands coming down from Nicaragua through costa Rica and Panama, and it stops at roughly the line of the present Panama canal, and then there is a deep ocean represented btwn. that point and anywhere in Columbia. and we were on this trip together in the Darien, and when you ¬you remember i said how beautiful those plantlike foraminifera were in those rocks (18:03 -) some of those that we were looking at are 15 million years old and some of those benthic foraminifera that we described were so sensitive for depth are telling us that it's 2000 meters deep at that point. um, so since i've qot 2000 meters deep benthic foraminifera over this reqion, and i know they are all at 15 million years old i am forced to the conclusion that where we were walkinq around with rivers in the darien was then a deep ocean -not a shallow shelf -a deep ocean. and that's crystal clear to some one who understands those benthic foraminifera that live in the deep_ now, when we get -as i am measuring up the river and we are getting rocks that are lying on top of those and they are getting younger and younger, i can get to rocks that from the paleomagnetism and planktic foraminifera the floating ones, i can isolate all of the rocks in that region that are 6 -7 million years old. and then i find that the evidence is that the sea is much shallower, less than 200 meters deep now, and indeed there's sediment in there that shows that not very far away land was being eroded. do you remember we found those (ac: right, right, yes, right... ) layers of conglomerates and coarse sandstones, and shallow water mollusks. so, that allows me to reconstruct the fact that there are some strips of land near by ¬
19:31 ac: because when we found the sediment in that -contained in that sediment were rocks ¬tc: right, boulders and they aren't going to be, there is no mechanism except for floating icebergs which not a scenario that we have to worry about here. there's no other mechanism to get boulders into 2000 meter ocean except in very special circumstances
19:54 ac:so you know that some how these rocks are washing down from river beds and things ¬
tc: close by, that we may even be standing in the estuary of that river. so when i plot the distribution of that kind of evidence i can then come up with a vague map. i say vague because i couldn't swear to you the coast line is not 30 miles to the west of that or 15 miles to the east and in some cases a bit more. but i am pretty sure that something like that distribution of islands and shallow shelf existed at that time.
ac: ok -we just need pauses in here ever now and then to ¬
20:36 tc: and then, just to finish, in the 3 million year old map you can see that when we find sediments of that age, and we're finding less and less of them, because there's more and more of the archipelago is now above water, we are left with just one or two narrow corridors going from the Caribbean to the pacific; one across what is the side of the present canal which never gets more than 45 meters above, excuse me it's about 65 meters above sea level today. one through the atrato valley where Columbia meets Panama. and one through the area of lake Nicaragua which incidently was the place they first thought they were going to build the Panama -what is now the Panama canal, and that never reaches more than about 45 meters above sea level now. and if you remember Jeremy talking about sea levels going up and down, we are talking about a 100 meters of amplitude. so one of those raising of sea levels today would rebreach the isthmus even now. that's unlikely. we are at a relatively higher sea level stand than normal; a lot of the ice from the ice age has melted. so we are not likely to go up another 100 meters. but never the less, um, if you melted the rest of the ice sheets it would very closely raise sea level to the point where you could almost rebreach the isthmus now.....
22:06 ac: .... i have one more thing that i would like to figure out that is puzzling me. we are looking at this -now, here is something that i haven't quite figured out -we are looking at a fossil record that you were saying... that... obviously this is not/was not beach this was deep ocean. but it's not deep ocean now, it's land. so, it must have gone through a stage or a period of transition when it's rising up. so why isn't there a fossil record of it being ah -you know, beach?
22:53 tc: well, somewhere there is , but what you have to remember is that these 3 maps -i think the difficulty you are having is translating this vertical section that i am handing to you here as a history of one point to a series of maps which is an arrangement of points of the same age over much area. i have a lot of information about time at one point. i have much less information about space at one time. and so, when -if you think about it, what you are asking me -at this point in space, at that point in time, i have a rock that tells me that sea is 2000 meters deep. at the exactly the same point, i am now moving from the same point in the dariento the second map, i am going from 15 to 6 million years, i have a rock which is now 20 strata higher up in the section than the deep water rock, and i look at that same rock and the plantlike foraminifera in it -excuse me the benthic foraminifera in it -are telling me that it's only 50 meters deep. so now i've come up with 1000 -nearly 2000 meters. and then i go to this same point here on that third map and if i am lucky enough i've got a section that goes from 15 to 3 million years i will have this rock, even if it is a higher sequence of beds ,and it will tell me that at 3 million years there's a beach. or it tells me at 3 million years it's only 20 feet deep. ok? so, ... if i had that, and we do in many places, the map over there is of Limon in costa Rica of rocks of very similar age, and we have a section that does just that, in which case i can compute for you the fact that the land has risen 1950 meters in 15 to 3 that's in 12 million years. Now you can divide that through and calculate the rate of uplift. the trouble is the beach itself, and the land that will then appear above it goes from being a depositional area to an erosional and on much, much less likely to have that beach preserved or the swamps or the rivers, etc..
25:30 ac: pardon my...um .......but it's obtuse....we are here in the darien... (tc: that's roughly where we were yesterday) and the sediments are telling us this was 2000 meters, but, from what you have told me about the geology of the region, i know that this point when that was 2000 meters if 2000 meters was 15 million years ago, that point wasn't there (tc: right, there was no darien) 15 million years -but it's a point on a plate that was over here ¬
26:24 tc: we haven't even discussed the complication of the fact that these are moving plates. in fact, then darien is probably was, as you say, further out to the west. notice on this diagram that i showed you that shows the ocean much, i've noted much wider ocean is written on here. because i am looking at this space today but in fact, it was perhaps twice as wide or maybe more 15 million years ago. it has consertinied (???) up. and in fact the reason for
27:02 the fact that that 2000 meter deep sediment of 15 million years ago is above water and you can look at it, is precisely because the plate has pushed and pushed and pushed against the caribbean plate, and in the process has compressed the whole situation which has buckled it which has caused it to rise up. so that's part of the reason why you are seeing more and more land appear above the surface it's because central america and the pacific are crashing together.
27:32 ac: as it rose up it did create some beach region -it carried the record of that at one point, but it's eroded away ¬
tc: it's probably eroded away, or perhaps we will find it one of these days. or perhaps we will find it one of these days if we are lucky, but it's quite likely that the moment that it's come up above sea level it's been -i mean the rainy season in the darien is quite something to see, and the rate of erosion of those rivers is phenomenal. and the rate of chemical destruction, by you know chemical weathering, break down of sediments is quite impressive. so the likelihood is that we won't find much of that. so what we'll have to do to tell you the moment in which that river system developed which biff certainly wants to know about because he wants to know what's the earliest moment my fish could have been swimming in fresh water, is to try and find out what's the youngest marine sediment we find anywhere in the isthmus. and if we can say after 2.8 million year we never see another marine sediment -we see estuarine or....then we can say ah, that's about the time the isthmus has gone up. but it's still a little bit vaguer than what i tell you about a single point, a single section in time, because there may have been marine sediments there and they may have been subsequently eroded away and i will not be able to detect that.
29:01 ac: ok... leo: we are off....
dead air through 29:57 (i think alex is writing some notes)
NOW ON WITH JEREMY ..............
29:58 -30:39 no good
30:39 jj: this is the place where all of the work based on all of these things is done. and helena fortunado is a research associate of mine
. . . . . . . . .. . .. .............. .
no good through 31:31
31:31 ac: so this is the kind of stuff that you bring back ...and just say what happens to it...
jj: .... this is a bulk sample of sediment from somewhere like where you were yesterday -and that's to show you that we actually find things. ok, this is from a very rich locality so even in the bulk sample after things have been specially taken out it's full of large gastropods as well as other things. that sample is sieved through these four sieves which are of varying mesh size and when that's done you then get this.......
no good blc of the air-conditioner
32:50 ac: we are in jeremy jackson's lab at STRI in Panama city and this is where the stuff that he gathers in the field goes on at least the first stop. this is a room maybe 20 by 15 a couple of sinks in it and some people with ah pretty intense looking microscopes. a lot of file cabinets and baskets of samples labeled and bagged in plastic bags and some wall cabinets, charts and things, lots of computers and maps and uh and some stuff -and here is jeremey who can explain what happens.
33:51 jj: ok, so here is a bulk a sample which is collected in the field when we think that it's actually worth going to the trouble and the time of processing it. meaning that we have been able to see that there is some concentration of fossils in the material when we get it. and this is a particularly rich sample even though the outcrop would have been picked before it was bulked sampled for particularly good specimens this one is full of snails and what have you. the sample is sieved through four different mesh sizes and then in the end what you get are four different size fractions of materials the largest size fraction -and this is all just from one sample, ok. the largest fraction being very rich and mollusk in this case. the next size fraction tends to be the best fraction for
bryozoans and the very smallest fraction we rarely look at but we say that in case that we need to go back for something --one also finds the ear bones of fishes, which one can use to identify fish to genus, and things like that...we have a new person from Venezuela who has expressed interest in doing that. we never had somebody interested in that before that's why you save samples, because people come along. ok, if you have a huge sample like this and you need to look at this fraction, it might take magnolia two weeks to go through that and pick it, which is too much time so we pour it through a splitter like this to get half, a quarter, or an eighth or a sixteenth of the sample some amount that would -can be delt with given the constraints of time or what have you. after that the sample has to be picked, and there is no replacement for simple human labor. and if you
.... you can look and you can see the type of stuff that she is picking out. so here in the middle for example are some rather dirty fragments of bryozoan colonies which are small colonial animals whose -each chamber of which constitutes (ac: wow) the home of a polyp like animal. she spends on average a solid week on each sample, just picking the material out so that it can be identified.
36:23 ac: are these reef fragments that we are looking at? ..
jj: these are fragments of little colonies of bryozoan colony -bryozoans ¬that grow this particular thing as tiny little trees, maybe a centimeter high. and i have no idea actually about where this sample came from. um, there's also a ¬
36:49 ac: i am sorry, i am saying that because i look through there i am saying, gee, these things look like reef fragments. but of course, they are absolutely minute little things. and they only look like reefs because i see them under intense magnification.
37:03 jj: we never found any mollusks on the field trip, we found a lot of foraminifera. here are a number of large foraminifera in the field. ok. she goes on and on doing that and you can see in these boxes the amount of material that's been picked out of the sample already. ok. and these then are examples of what might come from an entire sample. a number of different kinds of bryozoans which have been sorted at this stage very crudely, in terms of their general obviotite, because she can't afford to take the time to really look to identify them. different kinds of mollusks which we don't identify here, so this is material to send to Peter Jung in Basil. Corals to be sent to Ann Bud at the University of Iowa, an another person at the National Museum. So this is sort of the staging point, after which all of the mollusks are packed up and bagged and sent to Basil and switzerland. The corals go to the people in the united states, and the bryozoans stay here. The bryozoans are then identified by Gero Anticea
(??) who goes once a year to the National Museum in Washington to work with my colleague, Alan Sheetum, and Joanne Santer, to confirm her identifications, use the reference collections in Washington, what have you. Gero has been doing this for nearly 9 years, and there are now two cabinets like this in Washington that are full of the specimens that she has processed. and you get an idea of the intensity of the labor when you just take any sample at random and realize that everyone of these is full of little bits and pieces that look like nothing at this scale, but which under the microscope are different kinds of bryozoans. and there are 150
genera of bryozoans, and approximately 500 species already identified.
39:18 ac: what you are showing me is a plastic box divided into 40 different sections, each one contains at least one and in some cases several specimen of a particular type -each is labeled in a little card there's some id of it written down in each of the 40 chambers of this box.
39:48 jj: and then after those identifications are checked, the data are entered into a computerized database, and when we really grow up and grow modern we'll avoid all of this handwriting and we will do the labeling and everything automatically -well, by entering the data in the computer right away and having a label spit out. so that this huge amount of time which is spent transcribing labels just as in the 19th century can be circumvented. so there are 8 or 9 person years have been invested in the processing of thesis material and that represents only one of the major groups of organisms being studied in the project. one could say at this point that there are approximately 30-40 person years of labor have been put into the production of the collections to the point that they constitute data rather than just objects of curiosity -in the Panama paleontological project.
ac: let me just ask you a rival thing here -CJ stands for coates Jackson.
jj: that's right. and these are the samples that are awaiting being processed because when we go into the field for 2 weeks and collect 100 bulk samples we create 2 person years of work. just in the processing to get it out of here. and that doesn't count the time that peter's army of people spend further identifying the mollusks or that other people spend identifying foraminifera, etc.
41:37 ac: i was wondering about that because you gather a bag of material in the field it takes three or four minutes in the field to fill up that bag ¬
jj: overtime you fill up that bag what you really need to be thinking about is the amount of time down the line. and although we do tend to collect more than we need to be sure, because it costs so much money to go back to the same place, we have large numbers of sample that we never process. that are sitting there on reserve, but which we simply can't justify the time and money to do. there's one other thing that i would like to show you. magnolia picked out examples of living and fossil forms of the same group. so in addition to studying fossil representatives we go out and we sample living organisms in the recent to get a sense of their distribution and for the interpreting of the fossil record. and all i want to show you here -here is an example of a living -this is a bryozoan that looks like a little Chinese hat, and this colonial organisms has such coordinated movements that it walks around on stilts that are about a centimeter long on the bottom of the mud. and it is a very characteristic organism of a particular environment. so that's one that was alive when it was collected, and here are some that are about 7 million years old. Cac: huh. except for size they are a little smaller-} and they are a little dirtier, and they have grains of sand stuck in them. They are a little smaller, because they happen to be a different species. and to try and clean them up you use things like an ultra sonic cleaner. this thing over here.
43:27 leo: amazing!
ac: wait a second -you got to see this.
leo: oh god, they are gorgeous.
jj: ok, so, i can't do it but Gero can do it. these are the cast of characters of the chinese hat bryozoans. these are the roughly 50 species where as before. . ....RE-ADJUSTING THE AXIS .... ok, these are xerox copies of scanning electron micrographs of the roughly 50 species of those Chinese hat bryozoans that have been found in our collection so far. there were perhaps half a dozen of them described before. so in order for gera to be able to just pick these things and identify them she has to work form these scanning micrographs almost all of which represent new species that will have to be described afterwards, and we don't even want to be worried about that at this point, but she can't do the work reliably without having all of these different pictures in front of her to know which little box to put them in. when it became apparent that that group was so diverse, it took a month of work to do nothing but try to sort out roughly what those groups would be, in order to proceed with the simple processing. any formal taxonomic description of these organisms which is a second phase of the project, is probably on the order of 5 or 10 years works by somebody who wants to dedicate a large part of their life to it. we don't have time for that level of resolution now, we deliberately avoid that degree of subdivision, because if we got bogged down doing that we'd never be able to unravel the simplest patterns of distribution and abundance. and that kind of problem exists for every group we work with.
45:26 ac: you just simply must get up and look at these things -they are so fascinating to see ¬
cj: i'd be happy to
ac: but how you distinguish between this and this and this and this and this ¬
45:45 jj: well, the little yellow parts are places she has highlighted which indicate features that are diagnostic per a particular group. but you know for doing this it's like distinguishing any group. for example bird watchers will tell you that the best bird books are the ones that don't have accurate photographs but which have paintings which artificially highlight the diagnostic feature for the identification of the birds. and these photographs are taken in a way that highlight the features that are particularly useful.
1?1\tJE)~ ................. ac: this shell looks like something i found on the beach yesterday ¬
46:50 jj: yeah, it's a strombis, and it looks very much like something called stombis puqalis that lives in the Caribbean now. and one of the things that's very useful for us in the work we do is that most of the forms have modern representatives. and um, it makes it much easier to
interpret the past life habits, environments of these organisms because they have living representatives. in one sense that means that we are studying much less exotic creatures of the past in terms of their great similarity to the present, but on the other hand it means that we have far more information available for interpreting their patterns of association, and the way they lived.
47:42 ac: ... i am holding a specimen from this field bag and it looks like a small conch shell that you might find today. small, i would guess about an inch and a half, perhaps two inches long, ah -it's pale, cream, ah, kind of stained dark with dirt. it's filled with this dark sediment. um¬how common would it be for you to find something like -this appears to be absolutely perfectly preserved.
48:16 jj: this sample is only 2 million years old, and it's from a place in costa rica which has turned out to be enormously important to us because this is the first appearance of the modern Caribbean fauna of marine organisms. this fauna sits only a few thousand years above a sequence of the older fauna of the Miocene that dominated the region for 5 million years. it was discovery of this fauna which alerted us to the fact that there had been a sudden and striking turnover of the Caribbean biota roughly 2 million years ago. so you go down, below the deposit where this bag was collected and you see a biota of forms that are roughly 50% extinct. and we think that the interval between that now half extinct fauna and this fauna which is essentially modern is only 200 to 300 thousand years. That's such a remarkable result, that we just had an expedition last month by tony coates and ann buds from the university of Iowa and a number the people involved in stratigraphy in the project to go back over all of the sections in that area, recollect them, to date them again, to get paleomagnetic information and the like. because if in fact this holds then it provides really striking evidence for rapid shifts in the composition of marine communities of the type that we hadn't originally suspected...
50:00 ac: ... and why did this happen 2 million years ago?
jj: well i think this happened because of the intensification of glaciation in the northern hemisphere. and how that caused this turnover is really anybody's guess. we know now that temperatures really did decline in the tropics by as much as 5 or 6 degrees. we also know that there were probably changes in the food chains in the sea -changes in upwelling patterns, and nutrients and the like, and we simply don't have yet the kinds of geochemical data that we need to sort out which of these factors we think is more important or perhaps other factors. but the coincidence with the intensification of northern hemisphere glaciation is so obvious and dramatic that it must some how be connected to this major shift in the climate of the world that took place at about that time.
51:00 ac: is that glaciation tied to the rise of the isthmus -even though it was a million years earlier. the changing ¬
jj: that certainly is the prevailing opinion that the formation of the
isthmus, and the birth of the gulf stream and the transport of moist air ¬
of heat, and therefore evaporation in the polar regions is the basis of
intense effied ???? glaciation, that's really not my game, but that is the prevailing view. and that opinion was developed independently of all of this work. the discovery of the turnover long postdates the paleoclimatic reconstructions that ascribe the isthmuian basis to that phenomenon.
51:50 ac: 2 million years ago, there are X number of species, marine species. you have this catastrophic event, at least in terms of life at that time. 50 % of the species are driven into extinction, does that mean we have 50% fewer marine life forms today than we did 2 million years ago. or are those life forms replaced by other life forms?
52:21 jj: the conventional view before we did this work was that there was a mass extinction in the Caribbean that was not replenished by speciation. what we discovered again to our surprise was that anything -diversity in this fauna -is higher than in the fauna that immediately proceeds it, allowing for the enormous amount of sampling error and the inadequacies of our samples, despite all our efforts. so far, it's certainly safe to safe to say that there was no dramatic decrease in diversity the way people thought. so that this was indeed a turnover in the biota rather than just a simple extinction of the biota. one of the reasons the stratigraphic refinement is important is that if we can really pin down the timing of these events, we might for example, be able to ask did the extinction proceed the speciation or did it all happen together at the same time. that may be impossible to resolve. we really don't know whether or not we will be able to refine our time scales so exactly that we can answer that question. but it's a very important one, because depending on which way it came out that would greatly influence the kinds of models one would make up to try and explain the pattern of turnover that we observe.
53:51 ac: carolyn has a question about lessons of biodiversity -lessons from the past that may be applied to the future, i am not quite sure that i can phrase this correctly. but i think what she wants to get to is what you all were talking about in conversation the other day.
54:13 cj: it just has to do with the application of being able to draw upon the record that the fossils provide of life on earth basically. you are able to appreciate and understand life on earth through the fossil record. can you use that information to predict the future at all?
54:41 jj: well, you might not be able to use it to predict the future, but at least you could put constraints or boundary conditions on the behavior that you might expect. the formation of the isthmus resulted in very significant environmental changes and yet at least initially we don't see much of an evolutionary or ecological response. all tony's and my arguing back and forth about just exactly what that means makes it clearer that whatever effects there may have been, they bear discussion. on the other hand, a million years or more later, we then see this dramatic event of turnover and change in the biota caused by a different set of factors whatever they may be. That right away tells us that there is a certain resilience to ecological systems. such that even though they may be perturbed rather profoundly they don't necessarily respond in a one for one fashion. in other words, gradual environmental change does not necessarily illicit a comparable and equal change in the biota. it also tells us that there may be thresholds, or break points, such that we may think a system is in fine shape because it's been stressed and stressed, and nothing happens. and then all of the sudden it might break and we could see a very sudden shift. and in fact, some of believe that's exactly what's happened in the caribbean today in terms of coral reef ecology in the Caribbean. that a long history of overfishing of Caribbean reefs resulted in apparently very little change in the coral communities. we know that from old records, and also from examination of subfossil and Holocene deposits, only a few thousand years old. and we were all living in a fools paradise thinking that the fish that were obviously gone from places like Jamaica that corals were clearly still abundant. and then a series of natural and possibly natural disasters -a major hurricane and the die of the sea urchin, which had taken the place of fishes as the principle grazer resulted in a dramatic shift in coral reef communities such that micrologies seaweeds cover coral were living corals used to exist. nancy knowlton for example has modeled that and tried to understand how these kinds of threshold effects can result -at least in the short term ¬difficult to reverse or irreversible shifts in community composition. those aren't the kinds of things managers want to worry about, because they are mUCh, much more complicated. it means that the sequence of events, long ago, may have a very real effect on the way a system will behave in the future and without a historical perspective you can't begin to manage Caribbean coral reefs. one could make other kinds of examples, but that's just one that i know a little bit about.
57:57 cj: much of the discussion and much of your work focused on the past when there are natural disturbances. but what happens when you introduce man on earth into these natural life systems. how has man effected life on the oceans?
58:16 jj: well, the coral reef example is again convenient because it is relatively simple. we know from the historical accounts in the new world from only a few hundred years ago that there was a great abundance of large fish and other vertebrates in Caribbean marine ecosystems that are virtually gone. we know that these were major consumers of sea grasses and algae and other kind of fishes and what have you. and therefore we can see this very clear human stress, and we believe in fact it was overfishing i mean many people believe this. this was first pointed out by a number of people, most prominently by a fellow named Mark Kaye ? Markay? at the University of North Carolina who clearly showed that there was a relationship between the amount of grazing that went on at a reef and the amount of overfishing -or fishing -that had occurred. and so, it seems pretty clear the reason the death of the sea urchin in this epidemic had such a profound effect on the balance of sea weeds and corals is because the fish had been removed previously from the system by people.
59:34 ac: there is no redundancy in the system? to¬
59:36 jj: there is redundancy in the system, but the redundancy is reduced by harvesting. the redundancy exists in terms on grazing on algae and a number of groups of fishes and a number groups of echinoderms a number of groups of snails, and one time turtles and manatees, and organisms like that. but we have systematically removed most of these organisms from the system and so when the one, abundant, remanent form died for whatever
reason, presumable we don't even know the pathogen that caused the outbreak because it turned out to be impossible to isolate by ecologists who weren't experienced microbiologists, but that was just the final straw in a long sequence of events. so even though the final cause -for the sake of argument -was natural, the sequence of events that led up to the situation we now observe is a function of human activity and interference. one can argue for other kinds of examples like the death of the large mega-herbavores with the invasion of human beings into the new world 10 or 12 thousand years ago, and shifts from savannah to forest conditions, or what have you, that i know a lot less about. but these stories -these kinds of stories are accumulating as we begin to realize that there has been a much tighter interaction than suspected between human activity and natural ecosystems long before western Europeans spread out over the globe.
1:01:23 cj: one last question has to do with two words mentioned yesterday. and i think that you were suggesting that they were -the two words were signal and noise and being a~le to distinguish between the two when one considers what is happening to the environment. what did you mean by those two terms?
1:01:40 jj: ok, well let's talk about reefs again. maybe coral reefs on the north coast of Jamaica are in the terrible shape their in, meaning almost no living coral and a great abundance of seaweed where it wasn't before. maybe they are the way they are because of something that is unique to Jamaica. maybe Jamaican fishermen are more efficient in harvesting than fishermen anywhere else, or maybe the hurricane that passed through Jamaica was the reason. or maybe the oil spill that killed the coral in the reefs here in Panama in 1986 was the reason for all of the problems that exists on the reefs in that region in Panama. how do you sort out that individual local pattern from a wider scale, when the only way you can do that is to sample from many places at the same time so you can factor out different local effects to try and get a sense of a regional signal. and that experiment is what hector Guzman from STRI is doing in the Los Racos archipelago right now; attempting a partial human exclusion experiment that will allow him to evaluate the extent to which coral reefs on a large but local scale might respond to the removal of human interference to see whether or not that kind of local effort can indeed have an effect. and that's of course very important for many people if one wants to convince an indigenous people somewhere tat they should hold back from fishing in a large amount of their territory that's a difficult political decision for them as for anybody else, and you wanted to be able to provide their leaders with the kind of information that would suggest to them that it's worth the risk. that they might indeed see a return for their trouble within their life time, in a kind of way that their people would understand. and that's really no different from any people. the only reason i said indigenous people is because they are actually more interested in many cases than many others. and so there are a number of areas in Panama that are looking to see the answer to this experiment.
1:04:07 -1:05:16 NG -planning what to do next, leo recorded dull sound from the lab -faint: people typing on the computer
1:05:17 ac: ...... i tell you that -although i would never admit this-we
MUST destroy this tape -i'll tell you that we have a bias -in that our bias is we are basically conservationists i think; i mean we are in favor of the natural world, we are in favor of preserving the natural world, and we -ah -that's why we do this......
END OF TAPE