The Madison-Hills Paleoecology Project ("MPEP")

Introduction

The MPEP is a privately funded endeavor that will drill and sample the layers of soft sediment that have accumulated in the deepest part of Big Pea Porridge Pond ("BPPP") in Madison, New Hampshire during the past +/- 14,000 years. The purpose of the work is to scientifically analyze, technically describe/catalogue, and radiocarbon/proxy date these progressively deposited materials to establish the ecologic change-sequence history of the Pond's basin since the departure of the last ice sheet. The work described above will begin in late January or early February 2008 and be completed by late Spring or Summer 2008.

Scientific Basis of the MPEP

Lake-bottom sediments represent the most continuously detailed records of post-glacial (Pleistocene to Holocene) climate and environmental change available, and such records provide the best long term context for the dramatic physical and biological/ecological changes that have occurred during what has become to be known as the "Anthropocene" period (time since the beginning of extensive human habitation).

Who's Involved

The scientific staff of MPEP includes the following individuals, all of whom are donating their professional expertise to the project:

P. Thompson Davis, Ph.D., Dept. of Natural & Applied Sciences, Bentley College.
Brian Fowler, Quaternary Scientist, Project Director.
Lee Pollock, Ph.D., Dept. of Biology, Drew University.
Lisa Doner, Ph.D., Center for the Environmental, Plymouth State University



Thursday, January 5, 2012

Update

It's been a while since news has been posted here, so I thought it time to do so. In fact, it's way past time; the last post was in 2009 (!). Sorry...

Our project is still underway with work being complete in the labs at Plymouth State and in the labs of Beta Analytical, where our last 3 carbon-14 dates are being processed for us. We hope to have these results by months end (1/12), and I promise that I'll get them posted asap aftr I receive them. Thereafter, and after the rest of the lab work is complete, work will begin on another professional publication of our results. Portions of that will appear here as they become available.

Meantime, longtime Pond-resident Connie Brown is publishing a book about the history of the Pond in the next couple of months. That book will include the first layman's summary of climatic information for the Pond basin. So, keep an eye out for its availability, and we'll be "back here on the blog" soon.

Tuesday, September 8, 2009

Scientific Posting No. 24

Results at Last!

Here is one of the long overdue RESULTS reports that Brian mentioned recently. This one addresses our efforts to use subfossil remains of midge larvae to investigate Late Glacial temperatures at Big Pea Porridge Pond. As you will see, it is a work-in-progress. But this report will bring you up to date at least.

If you are interest in investigating a particular phenomenon in nature, you search the landscape for a setting that makes viewing that feature clear. To study distribution patterns of animals, for example, you don’t start out with the bewildering complexity of a tropical rainforest. On the other hand, if you are primarily interested in unraveling the story of a particular location, you must apply available procedures and make the best of the results you get. I’ll use our studies using chironomid (non-biting midge) larvae as a proxy (an indicator) of past climate temperatures to illustrate this point. Today, these insect larvae are abundant and diverse in lake bottom sediments. The same was true in the past.

To study past temperature changes, paleoecologists have selected small, shallow water bodies because they are sensitive to overlying atmospheric conditions. These water bodies mix easily and frequently with any modest wind. While in any water body, direct heating by the sun may be limited to surface waters, wind-driven mixing in shallow pools circulates warmed water throughout the water body and in the process heats up bottom sediments throughout the pond as well. When climate-sensitive adult midges reproduce and lay their eggs in such ponds, the eggs sink to the bottom where they hatch into tiny larvae that feed on organic debris, unicellular plants, and in some cases on each other. As benthic (i.e., bottom dwelling) creatures, they pass through 4 successive molts before eventually becoming pupae and finally adults. Figure 1 shows examples of these larvae.



Long after the soft parts of such larvae rot and disappear, their hard head capsules remain intact. For every egg laid or adult hatched, there are 4 hardened, exoskeleton head capsules (inset in Figure 1) left behind in the bottom sediments. Each year, debris from the plankton community, leaf litter, pollen grains, etc. sinks to form the next layer of bottom sediments, trapping beneath them sediment layers from previous years. Each year these settled sediments include midge head capsules representing the variety of these creatures alive at that time.

As waters circulate within a pond, in a fashion similar to that seen when you gently swirl a bowl of water containing small particles, there is a tendency for small items such as the heads of midge larvae to be swept from the shallows around the perimeter towards its center, where they eventually sink through the water and join that year’s layer of bottom sediments. Since there is no corresponding mechanism to sweep such midge remains from the deeper bottom toward the shallow shoreward regions, bottom samples taken toward the pond’s deep center are most apt to include the full array of chironomid types available at that time – both the shallow (often warmer-water tolerating ones) and the deeper (more cold tolerant types). Also in the deep center, the delicate annual layering of bottom sediments is far less apt to become disrupted by water movements or by biological activity (burrowing mussels, wading moose, or human boating or swimming traffic). It is conventional wisdom that coring “the deep spot” provides the least disturbed, most representative chironomid samples.

From our sediment core, I took 3 cc subsamples at 10 cm intervals starting at the bottom of the core and progressing towards the surface. Refer back to Scientific Posting 22 for a description of subsampling techniques. For each subsample examined, we determined the “species composition” of the community of chironomids alive at that location and at that period in time.

Many of the chironomids found in deeper sections of the sediment core (i.e., from several 1000 years ago when local conditions were much colder) represent species no longer active in today’s warmer climate at PPP. However, these very same species are alive today in more poleward, colder localities such as ponds of northern Canada, Labrador, etc. Scientists have visited these locations and studied the environmental conditions in which these representatives of these species thrive today. Doing so has permitted them to determine that the mid-summer surface water temperature is the environmental variable that most accurately determines which species are present in bottom sediments and which are not. They have determined the optimal mid-summer surface water temperature required by each species. Using this information one can use a mathematical model (a partial least squares weighted average (PLS-WA) model) to blend the optimal temperatures for each species found in a given subsample, weighted by proportional abundance of that species in the subsample’s community, to produce the “best guess” inferred mid-summer surface water temperature that would fit a chironomid community composition matching that observed. For each subsample, a temperature point so generated is placed on a graph. Repeating this at 10 cm intervals up the sediment core generates a temperature profile for the period.



Studies of this sort in water bodies throughout northeastern North America have generated profiles similar to that shown in Figure 2. Starting to the right, at the retreat of glacial ice, temperatures rise steeply, but then shelve off, usually with a modest mid-shelf dip. This period is referred to as the “Killarney Oscillation” and in most cases occurs just older (i.e., deeper in the core) than 11,000 radiocarbon years before the present. Following the Killarney period, temperatures plummet to near glacial conditions (9-10 C) and they stay low for approximately 1000 years – from ca 11,000 – 10,000 radiocarbon years before the present). This period is known as the Younger Dryas period and may correspond to the time when glacial retreat was enough to permit meltwaters to, for the first time, flow out through the St Lawrence system, flooding the North Atlantic. This surge of frigid freshwaters may have been sufficient to block the Gulf Stream from delivering its included heat to northern North America and Europe. The Younger Dryas ends in a steep temperature build-back to something resembling today’s climate.

The top of Figure 3 shows an example of such a profile – this one generated from sediments taken at Splan Pond in New Brunswick. The Killarney Oscillation and Younger Dryas periods are obvious. The temperature profile generated from our analysis of the core taken at Big Pea Porridge Pond in New Hampshire may be seen in the bottom of Figure 3.

Comparing these two graphs, some overall similarities are seen, such as something generally similar to the Killarney Oscillation followed by a period of much lower temperatures. But there are also clear differences. 1) There is a spike in temperature late in what “should be” the cold Younger Dryas (marked as “4” on the Pea Porridge Pond figure). 2) There is a more modest overall temperature range observed (10-16 C at Big Pea Porridge Pond vs 0-18 C at Splan Pond). So how do we explain these differences?

Table 1 compares features at Big Pea Porridge Pond to those at 14 other locations where chironomid-based temperature estimates have been made.

Big Pea Porridge Pond lies furtherest to the south of all these sites, but not so much so as to account for the differences we found. Big Pea Porridge Pond is both the deepest of any of the sites (only Splan Pond at 10.4 m comes close) and by far the greatest in surface area of all (48 ha vs. a mean value of just 4 ha for the others). Although, Big Pea Porridge Pond is small compared to other New Hampshire lakes, it is large enough so that nearly all the input source of radiant heat from the sun is absorbed in its surface waters only. Looking progressively deeper In summer, this creates a layer of warm surface water and then a “thermocline” region of sharply falling temperatures overlying otherwise much colder deep waters. Such lakes are referred to as “thermally stratified”, and as such, resist vertical mixing. The creators of the PLS-WA model were clear that their model is designed for use on small, shallow water bodies that are not large enough to thermally stratify. Their model is designed for use in small, shallow, frequently mixed water bodies. But we were trying to learn about past conditions in our particular lake which doesn’t match this description. We are in fact applying a mathematical model to a circumstance beyond the model’s limits. But nonetheless, what can we learn about the past at Big Pea Porridge Pond?




Working in a larger, deeper, stratified pond means that only the shallow perimeter and the bottom sediments underlying its edges are significantly warmed by the sun, leaving the bulk of the lake’s interior and its underlying sediments much cooler and less variable in temperature. The published information on chironomids reveals that some larval types are associated with deeper, colder sediments (i.e., “profundal” sediments), while other species are limited to shallow, warmer sediments (i.e., “littoral” sediments). In Figure 4, we have calculated the percentage of each of the communities we observed at 10 cm intervals comprised of colder, profundal types. Sixty to eightly percent of our communities met this criterion. In previously published studies using chironomid larvae in this way, more than half the chironomids are warm littoral types. By studying communities from a deeper colder lake, we have observed communities more dominated by colder larval forms than is the case in ponds upon which the model is based. Therefore, our data matches low temperature patterns observed elsewhere, but it underestimates the higher temperature portion of the temperature profile, i.e., our smaller temperature range.

But the most obvious departure of the PPP temperature profile and that of Splan Pond is the late-Younger Dryas temperature spike. No one anywhere in the northeast has reported a similar late-YD thermal event at that time period. It makes you stop and think about the temperature conditions larvae living in the depths of thermally stratified PPP may have encountered. Eggs laid in PPP are the product of adults flying around in and totally dependent on the ambient climate conditions, including temperature. But in fact, once eggs have been laid in PPP and have sunk through the warm surface water layer followed by the thermocline, they enter cold deep water that, in a thermally stratified pond like this, shows very little temperature change year-round. Survival of larvae in all but the very shallow bottom sediments in this larger, deeper lake has little to do with temperature. Temperature is simply not much of a variable in their larval lives. What other conditions might influence which larvae survive and which do not in such lakes?

Frequently, in thermally stratified, non-circulating lakes, access to oxygen at depth is an issue. Oxygen is replenished in aquatic systems largely through diffusion into surface waters from the overlying atmosphere or as a by-product of light-driven plant photosynthesis – also a surface phenomenon. In small, shallow ponds with good mixing, frequent wind-driven circulation continually replenishes bottom sediments with oxygen. In deeper, non-circulating lakes, access to oxygen replenishment in deep sediments is a serious problem.

Once again, the published chironomid literature proved useful in providing information on which larval types are limited to conditions high in oxygen and which types are adapted to cope with reduced oxygen levels in bottom sediments. An example of an adaptation found in some species in the latter group would be the presence in body fluids of some species of hemoglobin which significantly improves oxygen uptake when it is scarce. Another low-oxygen adaptation is seen in species that build cylindrical burrows in bottom mud and use undulations to circulate water past their body. Comparison between species demanding high oxygen conditions vs those able to tolerate low oxygen levels vs those not distinguished by either characteristic, applied to communities observed from PPP, results in Figure 5.


One particularly striking change in proportions of these types can be found surrounding a depth of 790 cm within the core – exactly where the anomalous “temperature” spike occurred during the mid-Younger Dryas.

Our working hypothesis is that as the YD progressed, bottom oxygen in PPP declined. This resulted in a decline in high oxygen demanding species and a rise in those tolerant of lower oxygen. This represented an alteration in the community composition – in this case due to an oxygen crisis. But data reflecting this oxygen-related change was inserted into a mathematical model that only “understands” temperature. Consequently, the temperature model interpreted such a change in species present as necessarily being a result of a sudden temperature spike. Here is clear example of the problem in applying a model designed for use in environmental circumstances in which temperature change is the only or at least the primary controlling variable (e.g., small, shallow water bodies) to non-target circumstances in which two or more variables (in this case, both temperature & dissolved oxygen) are important.

It is possible that as the cold Younger Dryas period wore on, surface water temperatures may have dropped below 4 C. This is important because water is densest at 4 C. If less dense cold water (i.e., 1, 2, or 3 C) forms above deeper, denser, 4 C water, it will prevent the deep water from mixing with surface water. As a result of stagnation, dissolved oxygen used in bottom sediments would not be replenished. Oxygen levels would fall. Although year-round ice cover would also lead to stagnation, it would also block the input of chironomid eggs into the lake, and we noted no decline in chironomid larvae during this period.

We are currently exploring techniques for trying to distinguish between the roles of these two variables at PPP. If we are able to quantify changes in PPP’s chironomid community due to oxygen variations, perhaps we can “subtract” the oxygen influence to produce a clearer picture of temperature changes during this Late Glacial period.

Lee Pollock

Monday, August 24, 2009

Overdue Updates

After a long hiatus generated by the collapse of the economy during the past 6-9 months, the project staff is ready again to begin updating everyone on our progress on the project. In the next few weeks and months, we'll be adding posts that describe our results to date and the field and laboratory work that will likely be undertaken over the winter months. We apologize for this long hiatus; making making a living took time away from the project in various unexpected ways.

The first bit of news is that Brian gave a review presentation about the project on August 2nd to about 60 people who attended the program as a part of the Town of Madison's Old Home Week activities. Most of the folks there had not heard about the project before, and so there were lots of great questions and discussions about how citizen science projects like ours can get started up, about local/regional climate change, and about the geologic and natural histories of Big PPP. Of particular interest was the possibility that folks on Silver Lake may be interested in a project like ours. We'll keep you posted on any such developments.

Meantime and for now, that's it - back soon with more "good stuff".

Monday, December 22, 2008

Scientific Information Posting No. 23

LATEST PROJECT NEWS
First, the MPEP Team has been invited, both formally and informally, to present papers regarding its work to date at the Annual Meeting of the Northeastern Section of the Geological Society of America this coming March in Portland, Maine. These invitations are the result of the scientific interest our project is generating in the post-glacial geologic and paleolimnological communities of the northeastern U.S. and adjacent Canada during the past year. This is an important opportunity for us to present and discuss our current findings with others active in the same scientific fields, and we're excited to be a part of such a process. The abstracts for each presentation can be found by clicking on the following link icon:
Abstracts

As you already know, we obtained a new basal carbon-14 date for the bottom of the Pond that shows when the influences of the last glacial ice left the basin (~14,000 calendar years ago; see earlier Post). Since that time, we've analyzed the bottom 6 core samples (6 more to go), and have established that while the temperature of the Pond's water varied somewhat from time to time, the organic content of the sediments increased fairly steadily after the Pond was de-iced up to about 9,660 calendar years ago. At that point, something unusual occurred here, and right now we don't know precisely what.
Near the top of core sample T-7, we found two +/- 1 inch-thick light tan to yellow colored bands about 2 inches apart within the otherwise dark greenish brown to black sediment. These were the first such variations we found up to that point in the otherwise consistent sedimentation shown in the cores, and we immediately determined that they must represent some significant change in the environment around the point in time. We initially thought, based on what we estimated the likely rate of sedimentation in the Pond basin to be, that these bands might be the local representation of an important global cooling event that occurred 8,200 calendar years ago. If it did, it would be a very significant finding.
Accordingly, we carefully sampled each band to check their organic content, the relative temperature of the water at the time (from the species of chironomids present in the band's sediment), and their age via a sample for carbon-14 (AMS) dating taken from the regular sediment in the area between the two bands. The date came out at ~ 9,660 calendar years - too old for the bands to be related to the 8,200-year cooling event, but the organic content and the relative temperature of the water both drop significantly within each band. Thus, the bands do represent two significant cooling events of perhaps 100-years each with a break of maybe 150-200 years in between. We've tried to specifically relate the date of these bands with other known climatic cooling events, but have so far been unsuccessful.
Microscopic observation of the contents of the sediment within the bands after all organic material has been removed show they are composed of a combination of millions of siliceous diatom remains intermixed with a generally light-tan to yellow, but in some places orangey and pinkish residue that survived the high heat of the organic removal process with its various colors intact. We don't yet know what this residue is composed of, but we've sent samples out for geochemical analysis. When we get the results and combine them with the pollen analyses that are to begin soon on all the cores, we should be able to determine what these unusual sediments indicate about climate changes in the Pond basin back about 9,600 years ago.
We, of course, will keep you posted here on the blog in the next few weeks. Meantime, if you have comments or questions, please contact us by commenting here on the blog (instruction for doing so on the homepage). So far, very few folks have chosen to comment, but please do. It's easy, and it will be great to hear what you think the bands may represent about our Pond "back in "The 96-Hundreds".

Wednesday, October 8, 2008

Scientific Posting #22

The Chironomids

Among the sources of evidence of past climate conditions that lie buried in the layered sediments of lake bottoms are the remains of midge larvae. Today, non-biting midges (of the insect order Diptera, family Chironomidae) are abundant almost everywhere. You may have encountered tiny adult midges lying dead beneath the nightlight in the bathroom in the morning. They lay eggs in water and their larvae go through a series of molts before they metamorphose into pupae and ultimately into flying adults. The larvae (1/16th to 1/8th inch or so in length) are cumulatively so abundant that they typically form the largest single source of animal biomass in lake-bottom sediments. As such, they contribute an important food chain link between the detrital organic matter and algae that they eat and larger benthic (i.e., bottom dwelling) invertebrates or bottom-feeding fishes.
Because of their ecological importance, this group of insects has been well studied with regard to their identity (>5000 species worldwide so far), their distribution and the conditions required for their well-being. As arthropods, their construction includes a non-living exoskeleton covering that remains more or less intact long after the decomposable organic parts of the animal are lost over time. The head capsule of these animals are particularly thick and resilient and can be found identifiably preserved in the sediments into which they settled even thousands of years ago. Features of their heads – especially the appearance of their teeth, their dentition – are used by biologists to identify them at least to the genus level.
To study the chironomids present in the distant past, 3 cubic centimeter subsamples of sediment are removed from various levels within a sediment core. Each sample is immersed in hot 5% potassium hydroxide solution for 20 minutes, which disaggregates clumped sediment particles. The resulting mixture is passed through sieves with mesh sizes of 118 μm (micrometers) and 53 μm and rinsed with distilled water. Particles larger than 118 μm and 53 μm respectively, including the head capsules of chironomids, are retained in the sieves, while the bulk of the material, including most of the disaggregated sediment particles, pass through the 53 μm mesh. The material caught by each sieve is back-washed into a Petri dish and examined using 40X power of a dissecting microscope (see Figure 1).

Figure 1

Watch-makers forceps are used to transfer each head capsule present within the resulting debris to a drop of CMC-10 mounting medium on glass slides. A coverslip is added and the slide is observed using 100-430X power of a phase contrast compound microscope. Identifications are made with reference to several helpful publications (especially, Brooks, SJ, Langdon, PG, and Heiri, O. The Identification and Use of Palaearctic Chironomidae Larvae in Palaeoecology. Quaternary Research Association Technical Guide No. 10. 2007). A minimum of 50 chironomid heads must be located and identified to provide sufficient data to characterize the community of these animals found at a particular depth (= age) within a sediment core. It requires 3-5 hours of painstaking work to complete the analysis of each subsample.
The composition of the chironomid community that settles into surface bottom sediments today would be very different from that found towards the deepest segments of our core sample. The climatic conditions that favor today's community are presumably quite different (e.g., much warmer) than conditions here would have been 10,000 years ago. While many of the chironomid types found in the deepest parts of our core are no longer found locally, they do occur alive and well in today's cold climate areas such as Baffin Island or Labrador or in high elevation alpine tarns. Biologists studying these high latitude or elevation types have been able to determine the environmental conditions that these living representatives require. Distribution of chironomids is particularly highly correlated with mid-summer, surface-water temperatures of the lakes where they are found. We assume that the same critters living here years ago had similar requirements to their currently living representatives that over time followed the cold water conditions they prefer polewardly as the glaciers retreated and the climate here warmed. Species that have narrow preferences for cold water conditions are especially useful as indicator species, i.e., their presence in the past suggests that this narrow range of cold conditions existed then. Such species are referred to as stenothermal (steno – (Greek) narrow + thermal – (Greek) temperature) and they can be used as "proxy" clues to reveal temperature conditions wherever or whenever they are found.
Predictive models have been constructed based on documented requirements of each of these stenothermal species. Each species' optimal mid-summer, surface-water temperature requirement contributes in proportion to that species' abundance within a chironomid community from the past (i.e., from a particular sediment level) to produce a best-guess inferred mid-summer, surface-water temperature present at the time when that layer of sediment settled out.

Figure 2

(For example, Heterotrissocladius, shown in Figure 2, has an optimal temperature of 11.1 C, while Sergentia, shown in Figure 3, is optimal at 9.8 C). Doing this repeatedly at intervals through the sediment core permits the reconstruction of the most-likely temperature history of the pond over time.

Figure 3

We extracted a first-round of 15 sediment samples at 20 cm intervals from the deepest part of our core. Preliminary results demonstrate that we need to add intervening samples, resulting in 10 cm intervals, to improve the resolution of our model-generated temperature curve. We intend to gather these additional samples (and more) when we return to the core sampling on October 25th. It will be some time before the more refined results will be available. For now, we can say that in comparison to the mid-summer, surface-water temperature of 24.5 C (76 F) at Big Pea Porridge Pond in 2008 (see Scientific Posting # 20), comparable model-generated temperatures from the earliest portions of our core are, appropriately, in the 12-18 C (53.5-64.5 F) range.

Lee Pollock

Monday, October 6, 2008

Scientific Posting #21

Follow-up Plankton Tow in Big Pea Porridge Pond, August 26, 2008

To explore the composition of the plankton community responsible for the "positive heterograde" dissolved oxygen curve (see Scientific Posting No. 20), a 10 minute plankton tow was taken along a mid-lake transect with the net weighted to tow at a depth of ca 10 feet. Here is an annotated listing of some members of the plankton community at Big Pea Porridge Pond in Madison, NH, August, 2008

PHYTOPLANKTON = the microscopic, unicellular or colonial PLANT (or in one case bacterial) component of the plankton community.

Division: Cyanobacteria – blue-green bacteria
Anabaena : Chain of beads, including an occasional, larger "bead" known as a heterocyst. This is the site of nitrogen-fixation. This genus can become overly productive blooms and cause water quality problems. The neat thing about Anabaena in Big PPP is that it was not at all abundant. However, it formed some tiny ball-like masses to which a form of stalked ciliate protozoa, Vorticella-like, was attached. The beating of the cilia to create feeding currents by the Vorticella also propelled the entire colony around through the water – presumably an asset to Anabaena by bringing it to fresh nutrients and reducing its sinking rate in the water column.

Division: Crysophyta – golden-brown algae
Dinobryon: Colonial. Vase-shaped case or lorica, each with two flagella to provide some mobility to the colony. When abundant, Dinobryon sertularia gives a fishy taste to the water.

Diatoma: Colonial diatom.

Division: Chlorophyta – green algae
Asterionella – star shaped colonies. Individuals are glued to one another at one end by mucilage.

Micractinium – small spherical cells with projecting spines to aid with floatation.


Division: Pyrrhophyta – dinoflagellates
Ceratium – armor plated cell with 3 long projecting spines that assist in floatation. They are "mixotrophic", i.e., they both photosynthesize like a plant and phagocytize, eating other organisms, like an animal.

ZOOPLANKTON = the microscopic, unicellular ANIMAL component of the plankton community.

Phylum: Rotifera
Asplanchna – large sac-like rotifer. Feeds on algae and bacteria. Its presence here suggests productivity is more towards the oligotrophic side. It also suggests that pH of Big PPP is usually at or above 7 (neutrality).

Keratella feed on algae and microorganisms. They tend to have two population maxima – one in the spring and a second in the summer. They live for about 3 weeks – longer than many rotifers whose lifespan in measured in days. They tend to be associated with oligotrophic waters.

Kellicotia longispina – with 4 long spines that assist with buoyancy – slowing its sinking rate. They are typically in oligotrophic waters and have a single mid-summer population maximum.

Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca
Order: Cladocera ("water fleas")
There are illustrations and descriptions of each of these water flea species at: http://ilmbwww.gov.bc.ca/risc/pubs/aquatic/crustacea/

Bosmina longirostrus A small, substrate-dwelling type with antennae modified to form an "elephant trunk"-like projection. The remains of exoskeletons of this type of water flea are the most common objects of animal origin found in our deep core samples from the past.

Daphnia longiremis Their egg cases or ephippia are among the items that remain well preserved in the sediments thousands of years old in our core samples. An indicator species for cold, oligotrophic waters.

Holopedium – has an inflated body covering encased in a large gelatinous coating. Uniquely among water fleas, it swims ventral side up. It tends to be associated with lakes tending toward the acid side of the pH scale, so it's presence in Big PPP clashes a bit with the rotifer Asplanchna. An indicator species for cold, oligotrophic waters.

Leptodora – a large (up to 18 mm) and bizarre water flea with enlarged, wing-like second antennae and legs adapted for capturing rotifers and other plankton.

Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca
Order: Copepoda

Cyclopoid copepods: club-shaped body with curved antennae or moderate length. Some are predatory, others are grazers. Undoubtedly several species.

Calanoid copepods: torpedo-shaped body with long straight antennae. Algal filter-feeders. At least two species – including one bearing conspicuous orange droplets of oil-storage reserved. This species is often associated with acidified waters.

Nauplius larva: only three-pairs of appendages. Undergo six growth stages or moults. Life cycle lasts 5-6 months.

As a rough indication of the relative abundance of these members of the plankton community at Big Pea Porridge Pond in late August, 2008, the following lists numbers observed in a 5 cc sample from a 10 minute plankton tow at 10 foot depth.

Phytoplankton (# of colonies)
300 Dinobryon slender
10 Dinobryon sertularia
600 Micractinium
60 Asterionella
80 Diatoma
10 Ceratium (individuals)
2 Anabaena
Rotifera
1 Dichoerca
24 Keratella
2 Asplanchna
4 Kellicottia
Cladocera
1 Leptodora kindtii
8 Holopedium gibberum
19 Diaphanosoma brachyurum
4 Daphnia pulcaria?
3 Bosmina longirostrus
17 Ceriodaphnia reticulata
Copepoda
61 Calanoid copepods
49 Cyclopoid copepods

(Click on the image below to be linked to a slideshow of more images of community members)
From Scientific Posting #21


Lee Pollock

Monday, September 29, 2008

NEWS

LATEST NEWS

Now that the summer's activities and travels, along with two weddings(!), are out of the way, work is scheduled to restart on the project. The splitting, sampling, and logging of the remaining core samples is scheduled to be completed over the weekend of October 25-26, and thereafter, the remaining laboratory work (C-14, pollen analyses, Loss-On-Ignition, magnetic susceptibility, etc.) will be completed as soon as practical by the various labs services. Meantime, scheduling discussions will begin soon for the completion of the pond bottom-surface ground penetrating radar survey (GPR) that had to be postponed last winter because of slushy ice surface conditions on the pond.

So, as all this gets retarted, the blog will begin to become more active as this Autumn and Winter progress. For now, sorry for the long silence. We didn't quit the project - just had lots of professional and family obligations.