Wednesday, April 23, 2008
Scientific Information Posting No. 14
While not purely scientific information, this is a project follow-up note on aesthetics for residents of Big Pea Porridge Pond looking out across the melting but still nearly complete ice cover (here on April 23!). We just wanted you to know that the debris the melting ice is revealing in the general vicinity of the drilling site is NOT anything we left behind there! But it is indicative of the depth of ice & snow cover this winter that the bright red plastic milk crate and the several large blocks of wood revealed now were completely and invisibly buried there at the time of our drilling operation. Lee.
Wednesday, April 16, 2008
Quick update on scheduled presentations regarding the MPEP project
1. We will be included with a poster/information table display at the Climate Change Forum scheduled for 6:30-8:30 p.m. on Monday, April 28th at the Kennett High School Auditorium. At the forum, presentations from experts around the country will focus on the science as well as economic and social aspects of the climate change phenomenon, including regional and global challenges and solutions. Speakers from organizations and state agencies will provide presentations on New Hampshire’s Climate Change Action Plan, information and science related to their field of expertise, and will also answer audience questions. Call 539-1859 for more information. Hosted by the Green Mountain Conservation Group, Eagle Academy and Timberland, Inc. The public and other schools are welcome to attend this event.
2. We will also use the poster/ information table format to help represent the activities of the Tin Mountain Conservation Center at a gathering from 6:30-8:30 at Granite State College on Wednesday, May 21. We have recently formed a linkage to Tin Mountain, finding that the MPEP project has much in common with their educational mission.
3. We will present a program based on the MPEP study for the Kennett High School Environmental Club at their monthly meeting at the Tin Mountain Conservation Center on Wednesday, May 21. Contact Tin Mtn for more information: 447-6991.
4. On Tuesday, June 10, we will review the MPEP program so far, and talk about its goals as part of the Tin Mountain Conservation Center's Nature Program series. More information at Tin Mtn: 447-6991.
At each of these sessions, we hope to gather names of individuals interested in the issues raised by our project. This group will form an informal discussion "club" that will be invited to meet at the Tin Mountain Center periodically to learn about new information as analytic results become available and to help us all explore the evolving story of the post-glacial period in this area.
Lee Pollock
2. We will also use the poster/ information table format to help represent the activities of the Tin Mountain Conservation Center at a gathering from 6:30-8:30 at Granite State College on Wednesday, May 21. We have recently formed a linkage to Tin Mountain, finding that the MPEP project has much in common with their educational mission.
3. We will present a program based on the MPEP study for the Kennett High School Environmental Club at their monthly meeting at the Tin Mountain Conservation Center on Wednesday, May 21. Contact Tin Mtn for more information: 447-6991.
4. On Tuesday, June 10, we will review the MPEP program so far, and talk about its goals as part of the Tin Mountain Conservation Center's Nature Program series. More information at Tin Mtn: 447-6991.
At each of these sessions, we hope to gather names of individuals interested in the issues raised by our project. This group will form an informal discussion "club" that will be invited to meet at the Tin Mountain Center periodically to learn about new information as analytic results become available and to help us all explore the evolving story of the post-glacial period in this area.
Lee Pollock
Tuesday, April 15, 2008
Scientific Information Posting No. 13
QUICK NEWS UPDATE
It's been relatively quiet on the MPEP front since we completed the drilling and sampling in early March, but things are beginning to percolate once again.
First, the project staff has now scheduled the so-called "Splitting and Sampling Party" for Saturday, May 3rd. This "party" will take place in the paleolimnology lab facilities at Plymouth State University with Dr. Lisa Doner as our gracious host. This activity will establish the next stage of the project's work tasks, primarily those that involve careful laboratory testing and documentation.
There are several specfic purposes of this activity once our samples have been retrieved from the walk-in storage cooler (maintained at 4 degrees Celcius since the field samlping) at PSU:
(a) to carefully split the samples longitudinally so we can inspect their interior where the shearing effects of the drilling and sampling process will not have disturbed them;
(b) to photograph and carefully document the nature, texture, and sedimentary structure we see on these freshly-exposed surfaces; and,
(c) to determine what type and how many specific laboratory test samples to take from these surfaces to develop the best picture of the samples' ages and fossil organic components.
This latter step will probably require the longest portion of this rather "full day" at PSU. We will report to you all asap after the work is done as to what was found and what testing is proposed to be done. That report will include the best photographs of the day, descriptions of the more interesting structural findings from within the samples, and preliminary comments on the possible paleoclimate history we begin to see. We will also attempt to establish a schedule for the lab results to "come in" and when we might be able to formulate a better picture of the Pond's paleoclimatic history, likely sometime in the mid to late Summer this year.
The second item of news is that Thom Davis and Brian Fowler have been asked to present papers as part of a northern New England pond paleolimnology theme session at the annual meeting of the Northeast Section of the Geological Society of America next Spring. Word of our project "has gotten out" in the regional geological community, and people are interested in what we've done, how we've done it, and what results we may have obtained by the time of the meeting. Abstracts for these presentations will be available nationally through the Society, so word of MPEP will spread. We'll also post them here on the blog. More about this later...
So for now, things are moving more slowly but surely. We will be back in touch in several weeks with more exciting news. Please stay tuned, and please give us your comments and questions here on the blog. For those not familiar with its use, please refer back several Scientific Posts to the one that provides the simple instructions. We'd love to hear from you all!
Friday, April 4, 2008
Amount of Organic Sediments Accumulated….Reconsidered.
Thinking about a full meter of sediments settling in a millennium seems like a lot of material to accumulate. On the other hand, when you recalculate that same meter of sediments on an annual basis, 1 meter or 1000 millimeters in 1000 years, the accumulate rate is only 1 mm per year, and that seems much more plausible. This would be especially so when you consider concentrating particulate materials appearing throughout the lake's interior in the lake's deepest area (much like gently swirling a coffee cup accumulates the grounds in the bottom center).
The accumulation rate of organic materials also depends on how productive the lake is – especially the contribution by the photosynthetic members of the microscopic plankton community (i.e., the "phytoplankton" – such as algae, diatoms, or blue-green bacteria). The VLAP data for Big PPP suggests chlorophyll-a concentrations are low enough to qualify the lake as oligotrophic (see other blog posts for a discussion of both VLAP and the oligotrophic/eutrophic questions), although the levels of cholorophyll-a and total phosphorus in surface waters of the lake show a historical trend of increase. More on that during the next year since the VLAP promises a report for the lake that will include a more extensive analysis of changes they have observed in more than 10 years of sampling data.
Meantime, another way to gain a "snapshot" view of the amount of organic matter produced within a lake (often primarily the result of phytoplankton productivity), is to observe a temperature-dissolved oxygen profile through the water column, taken when there is minimal circulation of the lake's waters. There are two times of year when this condition is met. Toward mid- to late-summer, when surface waters heat up more than deeper waters (your body is warm but your feet are cold when floating upright in the water), very little mixing of the water column occurs and deep waters stagnate. Also during the winter, when surface waters are colder than deeper waters (because freshwater at about 4 C is densest and sinks to occupy deeper parts of the lake – so water both less than AND more than 4 C are less dense and sit above 4 C water) and ice prevents wind from causing water movement and circulation, again the deep waters stagnate. In either case, without circulation, oxygen in deep waters can not be replenished from the surface, so if oxygen is consumed down there, the concentration of oxygen dissolved in the surrounding deep water declines. (Oxygen replenishment to the depths occurs primarily during spring and fall period of "turnover", when the whole water column is similar in temperature and thus equal in density, and the resistance to vertical mixing is minimal).
Some deep water oxygen is lost to various chemical reactions in bottom sediments. But the major source of oxygen depletion is from fueling the biological activities of the decomposer community – the bacteria, protists, fungi, etc. that live on and in bottom sediments and use the fall-out of organic particles (plant or animal parts, undigested wastes, biological detritus rinsed in from the surrounding landscape, etc.) as their food – their energy source. Like the rest of us "consumers", most of these decomposers use aerobic (oxygen-consuming) biochemical breakdown pathways, so to the degree that decomposition is going on, oxygen is lost from stagnant deep waters – and what is lost is not replenished until the next turn-over period.
Strictly "oligotrophic" lakes, with few nutrients and very limited phytoplankton productivity as a result, produce very little organic fall-out for the bottom-dwelling decomposers to use. As a result, not much oxygen is consumed in deep waters – even during periods of water column stagnation. Conversely, "eutrophic" lakes, loaded with nutrients and supporting dense phytoplankton growth, produce lots of organic fall-out, offering an on-going feast to the decomposers, who oblige by stripping the deep waters of their oxygen content. Comparing the actual levels of dissolved oxygen present throughout the water column with the maximal amount of dissolved oxygen possible, given the water temperature and no sources of consumption (i.e., the "saturation" level of dissolved oxygen), gives you a valuable piece of evidence about how much decomposition, and thus how much productivity, has occurred in a given lake. Little departure from saturation levels – ultra-oligotrophic, very low productivity lake. Oxygen levels falling to very low levels or perhaps to zero (= anaerobic conditions) – strongly eutrophic, very productive lake.
On Sunday, March 30, 2008, I performed such a temperature-dissolved oxygen profile on Big PPP. Since it's later in the season, I worked my way cautiously out toward the drilling site – stopping 4 times to auger my way through the snow & ice cover to be sure I was safe. In each case, there was 32-34" of consolidated, frozen snow & underlying ice present – including 10" of pretty solid ice at the base. In no case did I even begin to penetrate through the overlying consolidated snow layers, and knowing there was 10" of ice beneath, I felt okay proceeding. (Thanks to Bob Denoncourt for sharing his DO meter for this).
The graph below shows the results of this survey. You'll need to tip your head 90 degrees to the left to see the graph with data lines proceeding from the surface to the deepest spot at this particular site – about 33 ft. The temperature line (square-symbol line) is to the left and shows the less than 4 deg C (i.e., less dense waters) sitting on top of the 4 C layer toward the bottom. (If it weren't for this so-called "density anomaly" of water – being densest at 4 C (cold, but above freezing) – freshwater bodies would freeze top to bottom, and probably do in most of the creatures therein in the process). The actual dissolved oxygen curve (circle-symbol line) ranges from about 15 mg/L near the surface down to ca 5.7 mg/L at the bottom. The triangle-symbol line to the right shows what saturation dissolved oxygen levels (based solely on temperatures) would look like at each depth.
Clearly, the observed DO line doesn't closely follow the saturation curve, so we aren't as oligotrophic as would be possible. But it doesn't fall off to really low numbers or zero at the bottom, so we aren't strongly eutrophic. Using this one estimate of productivity, we might surmise that Big PPP is somewhere in between – tending toward the oligotrophic side of being "mesotrophic", since the 50% loss of saturation oxygen we see still leaves a fair bit of dissolved oxygen in the deep water to stimulate decomposition. But this does suggest to us that there is fair phytoplankton productivity in the surface waters, and that surely phytoplankton joined by zooplankton (the animal members of the plankton community) remains will have made a significant contribution to the buildup of organic-rich sediments at least in recent years.
.. Lee Pollock
The accumulation rate of organic materials also depends on how productive the lake is – especially the contribution by the photosynthetic members of the microscopic plankton community (i.e., the "phytoplankton" – such as algae, diatoms, or blue-green bacteria). The VLAP data for Big PPP suggests chlorophyll-a concentrations are low enough to qualify the lake as oligotrophic (see other blog posts for a discussion of both VLAP and the oligotrophic/eutrophic questions), although the levels of cholorophyll-a and total phosphorus in surface waters of the lake show a historical trend of increase. More on that during the next year since the VLAP promises a report for the lake that will include a more extensive analysis of changes they have observed in more than 10 years of sampling data.
Meantime, another way to gain a "snapshot" view of the amount of organic matter produced within a lake (often primarily the result of phytoplankton productivity), is to observe a temperature-dissolved oxygen profile through the water column, taken when there is minimal circulation of the lake's waters. There are two times of year when this condition is met. Toward mid- to late-summer, when surface waters heat up more than deeper waters (your body is warm but your feet are cold when floating upright in the water), very little mixing of the water column occurs and deep waters stagnate. Also during the winter, when surface waters are colder than deeper waters (because freshwater at about 4 C is densest and sinks to occupy deeper parts of the lake – so water both less than AND more than 4 C are less dense and sit above 4 C water) and ice prevents wind from causing water movement and circulation, again the deep waters stagnate. In either case, without circulation, oxygen in deep waters can not be replenished from the surface, so if oxygen is consumed down there, the concentration of oxygen dissolved in the surrounding deep water declines. (Oxygen replenishment to the depths occurs primarily during spring and fall period of "turnover", when the whole water column is similar in temperature and thus equal in density, and the resistance to vertical mixing is minimal).
Some deep water oxygen is lost to various chemical reactions in bottom sediments. But the major source of oxygen depletion is from fueling the biological activities of the decomposer community – the bacteria, protists, fungi, etc. that live on and in bottom sediments and use the fall-out of organic particles (plant or animal parts, undigested wastes, biological detritus rinsed in from the surrounding landscape, etc.) as their food – their energy source. Like the rest of us "consumers", most of these decomposers use aerobic (oxygen-consuming) biochemical breakdown pathways, so to the degree that decomposition is going on, oxygen is lost from stagnant deep waters – and what is lost is not replenished until the next turn-over period.
Strictly "oligotrophic" lakes, with few nutrients and very limited phytoplankton productivity as a result, produce very little organic fall-out for the bottom-dwelling decomposers to use. As a result, not much oxygen is consumed in deep waters – even during periods of water column stagnation. Conversely, "eutrophic" lakes, loaded with nutrients and supporting dense phytoplankton growth, produce lots of organic fall-out, offering an on-going feast to the decomposers, who oblige by stripping the deep waters of their oxygen content. Comparing the actual levels of dissolved oxygen present throughout the water column with the maximal amount of dissolved oxygen possible, given the water temperature and no sources of consumption (i.e., the "saturation" level of dissolved oxygen), gives you a valuable piece of evidence about how much decomposition, and thus how much productivity, has occurred in a given lake. Little departure from saturation levels – ultra-oligotrophic, very low productivity lake. Oxygen levels falling to very low levels or perhaps to zero (= anaerobic conditions) – strongly eutrophic, very productive lake.
On Sunday, March 30, 2008, I performed such a temperature-dissolved oxygen profile on Big PPP. Since it's later in the season, I worked my way cautiously out toward the drilling site – stopping 4 times to auger my way through the snow & ice cover to be sure I was safe. In each case, there was 32-34" of consolidated, frozen snow & underlying ice present – including 10" of pretty solid ice at the base. In no case did I even begin to penetrate through the overlying consolidated snow layers, and knowing there was 10" of ice beneath, I felt okay proceeding. (Thanks to Bob Denoncourt for sharing his DO meter for this).
The graph below shows the results of this survey. You'll need to tip your head 90 degrees to the left to see the graph with data lines proceeding from the surface to the deepest spot at this particular site – about 33 ft. The temperature line (square-symbol line) is to the left and shows the less than 4 deg C (i.e., less dense waters) sitting on top of the 4 C layer toward the bottom. (If it weren't for this so-called "density anomaly" of water – being densest at 4 C (cold, but above freezing) – freshwater bodies would freeze top to bottom, and probably do in most of the creatures therein in the process). The actual dissolved oxygen curve (circle-symbol line) ranges from about 15 mg/L near the surface down to ca 5.7 mg/L at the bottom. The triangle-symbol line to the right shows what saturation dissolved oxygen levels (based solely on temperatures) would look like at each depth.
Clearly, the observed DO line doesn't closely follow the saturation curve, so we aren't as oligotrophic as would be possible. But it doesn't fall off to really low numbers or zero at the bottom, so we aren't strongly eutrophic. Using this one estimate of productivity, we might surmise that Big PPP is somewhere in between – tending toward the oligotrophic side of being "mesotrophic", since the 50% loss of saturation oxygen we see still leaves a fair bit of dissolved oxygen in the deep water to stimulate decomposition. But this does suggest to us that there is fair phytoplankton productivity in the surface waters, and that surely phytoplankton joined by zooplankton (the animal members of the plankton community) remains will have made a significant contribution to the buildup of organic-rich sediments at least in recent years.
.. Lee Pollock
Subscribe to:
Posts (Atom)
