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Author Topic: What About Sapropel and the Conowingo Dam? - Tim Visel 9/29/14  (Read 2550 times)
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« on: September 29, 2014, 01:25:15 PM »

What About Sapropel and the Conowingo Dam?

Note from Tim Visel: [email protected]

I had started this report last April, but since that time I have discovered two important case histories related to Sapropel accumulations in reservoir systems in Arizona and Black Mayonnaise build up in the Indian River lagoon in Florida- then came the Conowingo Dam in July. Sapropel (Black mayonnaise) buildup and the sulfur reducing environments have been linked to shellfish disease, lobster shell rot (pox) and winter flounder fin rot as well as some parasites- even one that can harm us.
While most of the low oxygen high sulfide research is pertaining to blue crab and estuarine habitats is in progress, I hope that the Blue Crab Forum will allow posting this newsletter under the Environment and Conservation Thread for interested readers in the Chesapeake Bay area (my first post here).
Black Mayonnaise (Sapropel) is now under discussion across the country; I believe much of this is caused by an institutional or locational bias from the early marsh and cove studies that assigned very low organic deposition criteria to leaves.  In fact, many of the foundational studies did not include terrestrial organics of if they did, assigned them very low values. (Correll, 1975) (Nixon and Oviatt 1973)  As such, the concept of leaf fall impacts and negative blue crab habitat assessments from them are few. 
The Conowingo Dam Pond sediments maybe the most important case studies to date.  Connecticut coves, cores in 1992-1994 did show layers of organic matter between bivalve shell layers now thought to represent climate patterns (heat few storms- Sapropel habitats cold many storms- bivalve shell habitats)
The Conowingo Pond may have a habitat history of deposition in heat and could provide important information.  About 2 meters in depth high heat high organic estuarine coves should be Sapropelic – Sulfide levels rise sulfate bacteria increase with concentrations of metal salts.
With tannin signatures, it is now possible to identify sources of rotting organic matter – (even to the species of trapped leaves) organics behind mill dams.  On September 22nd I asked representatives of the Baltimore Army Corps of Engineers if they would share the results of deep core samples behind Conowingo Dam for student projects. 
I suspect that organic matter has been trapped behind this dam at great depths (Conowingo Pond) very similar to deep deposits behind mill dams here in Connecticut a century ago.  This organic compost may have very different habitat impacts in different environments.

Comments, suggestions I respond to all emails- Tim Visel

Connecticut Rivers Lead Sapropel Production 1850 to 1885
IMEP Newsletter #26
Habitat Information For Fishers and Fishery Area Managers
Understanding Science Through History

(IMEP Habitat History Newsletters can be found indexed by date on The Blue Crab.Info™ website:  Fishing, eeling and oystering thread)
and Connecticut Fish Salt Water Reports

What About Sapropel and the Conowingo Dam?
Did the Marine Community Miss Sapropel?
September 4, 2014
A Sound School Capstone SAE Project
Tim Visel, The Sound School


Prior to 1931 Connecticut and other New England farmers used an organic compost found in rivers and estuaries.  Two of the rivers that led Connecticut “Marine Mud” harvests were the Mystic and Connecticut Rivers – although smaller quantities were harvested in New Haven, Branford, and Old Saybrook.  Soils tests were conducted by the New Haven Agricultural Experiment Station for a half century (after 1931 commercial fertilizers quickly displaced organics easier to ship and spread they soon captured most of the commercial market share for them) consistently showed high sulfur and paraffin (wax) residues.  To offset the waxes recommendations included letting Sapropel freeze first, for the sulfuric acid, adding mixtures of lime stone or shells (mussel clam oyster) was often suggested.

Indeed some of the more valued Sapropel (marine mud) was that material containing oyster shell – an added protection against acidity.  Farmers often reported a “hurtful acidity” to the soil which we know now today is a segment of the sulfur cycle when old or deep Sapropel deposits was applied.  In fact trial and error use of it behind mill dams (in deep deposits) was found to “destroy all crops.”  The older and deeper it was it seemed the more toxic to terrestrial soils.  Most of the mill pond Sapropel in the Essex Connecticut region was from apparent leaf fall and avoided. 

The Conowingo Pond case history has been in the news lately and now the focus of intense study.  Sapropel and sulfur reducing bacteria digest of leaves emitting nitrogen compounds may impact Nitrogen TDML values (my opinion) in bays and sounds and appears to be overlooked, at least the sulfur cycle segment. 

This is the Capstone Question – Did The Marine Research Community Miss Sapropel? 

Sound School students interested in the Conowingo Dam study should contact Tim Visel in the Aquaculture Office.   


A century ago Connecticut farmers harvested “marine mud” from the lower sections of tidal rivers.  As long as this marine compost was “fresh” and consisted mostly of surface rotting terrestrial leaves (and seaweed mixed in), farmers found it was a nourishing compost, soil conditioner and sometimes a fertilizer.  But built up mud in deep deposits behind mill dams – those accumulations with a jelly blue/black and often greasy consistency when used “killed all crops” and had a strong smell.  (Reports of the Connecticut Board of Agriculture Report of the New Haven Experiment Station 1879).  Farmers from Canada to New York reported much the same result – some reported excellent  crop and soil productivity while others claimed it ruined their hay fields, some times for years.  (Various reports of the Maine Agriculture Experiment Station 1890s). 

What farmers experienced was the difference between aerobic reduction – those surface bacteria strains that consumed cellulose in the presence of oxygen and those best described as sulfur reducing bacteria – those older “more primitive” deeper bacterial stains that looked to sulfur compounds for cellulose digestion.  It is the byproduct of this digestion process that was so hazardous to farmers and is most recognized on land as acidic sulfate reducing soil.  In the marine environment buried organic layers putrefied in the absence of oxygen and are called Sapropel, from the Greek language “putrefied matter.”  When exposed on subtidal habitats Sapropel becomes both a killer of organisms and alters the ecology of estuarine habitats.

Sapropel has long been studied overseas – in Europe today it is harvested for a “green” fertilizer (natural and renewable) soil conditioners, filter media for complexing metals and sometimes soil supplements to lower pH.  Newer uses include pharmaceutical biotechnology (source of drugs) and energy.  Most of the available information in the United States about Sapropel often comes from the marine trades – as dredged material or acid sulfate soils from navigational dredging projects.

Not too much is known about New England Sapropel – it usually signifies a very slow bacterial process but in New England and behind reservoirs dams, organic matter (mostly leaves) can collect and reach several feet deep.  This can occur when dams or restricted tidal openings (railroad causeways) block transport (mostly forest litter called duff) leaves and some seaweeds. 

Sapropel Can Degrade Estuarine Habitats

Sapropel is a serious problem in the marine environment when tidal energy is reduced (natural or manmade) organic deposition is rapid and higher temperatures occur.  All of these factors diminish available dissolved oxygen in seawater.  In extreme heat a century ago that was the recipe for hydrogen sulfide purging from Sapropel (the rotten egg smell) and when disturbed by rain or ice the fish kills called  “black water deaths.”  The worse black water deaths (fish kills) happened in coves, restricted bays and rivers.  From time to time rivers near cardboard and paper mills were notorious for black waters an old term that still used in the Aquarium industry today and overseas.  In fact black waters still describe those conditions that are natural or manmade such as paper processing by products (black liquor) as a continuation wood sulfur digestion process (The Kraft Process™).

Black water events caused fish kills in the Murray and Murrumbidgee River catchments in 2010-2011 (Australia) and a portion of the case history includes the following “Black water is a natural part of the ecology of lowland river systems. Black water occurs naturally due to the rapid breakdown of leaf litter on the floor of the floodplain causing water discoloration and often low dissolved oxygen levels. Weather conditions where there is a prolonged drought followed by heavy flooding contribute to the severity of these events. “ 

Many of the black water deaths (fish kills) of the last century were linked to excess organic matter entering rivers and streams (The Saprobien System 1909).  The “tougher” the cellulose the more sulfur damaging the bacteria needed to consume them and the greater the habitat impacts.  (Much of the habitat reversals are now linked to organic matter from land as part of a long term climatic cycle termed the NAO).

The long chain cellulose molecules feed three basic of types of sulfur reducing bacteria and is a slow process but speeds up with heat.  When warm ammonia compounds are now released from Sapropel which often fuel brown algal growths (frequently called harmful algal blooms or HABs).  As digestion continues high levels of hydrogen sulfide dissolve into waters in winter leading to winter kills and when discharged downstream in a “sulfide wash.”  When Sapropel deposits are disturbed by storm or dredging and exposed to oxygen again (such as land application a century ago) or by ice currents below the sulfide quickly becomes sulfuric acid or “Acidic Sulfate Soils” toxic to plants, fish and oysters.  This is the marine sour bottoms or acidic damage described by Connecticut farmers a century ago and most likely whey Sapropel mixed with estuarine shell (mussels, oyster clams) negated this acidity.  (For nearly 50 years New England Agricultural Experiment Stations tested marine mud (Sapropel fertilizers) and found high sulfur levels).

Soil acidity has been reviewed in so many articles about dredged “spoils” (now termed material because of the negative association of low pH which is not always a negative factor).  Acidic terrestrial soils are good for certain crops such as blueberries so now dredge spoils today is termed material.  Researchers overseas are also investing the use of Sapropel as “natural filters” to bind polluting substances.  However, Sapropel the sulfur rich reduced organic deposits that purge (emit) sulfide has not to my knowledge been studied in Connecticut since the early 1980s.

Did We Miss The Sapropel Cycle?

A research bias now exits – a perception that all bottoms are “good” and a resulting general neglect of estuarine habitat succession.  One of the reasons that Sapropel research has languished here in the United States for so long is that it places a certain “habitat value” upon it and presents a major conflict in recent environmental policy in which dredging is perceived to be a consistent negative practice.  Sapropel exists and currently is under review in western states as its waxy residue frequently clogs drips irrigation equipment mostly behind reservoirs.

Recent news reports on the eastern seaboard again have also raised the issue of toxic sulfide washes downstream of the Conowingo Dam.  Here a large structure has accumulated decades of forest litter, mineral clays and organic matter.  Rain events appear now to dislodge deep deposits (suspected to be or close to becoming Sapropelic) releasing volatile acidic toxic organic compounds (VOC) that release toxic hydrogen sulfide into outfalls.  Hydrogen sulfide is more toxic than cyanide.  Core sections of deep sediments is currently under review by the Army Corps of Engineers in regards to the Conowingo Dam study.  Core sectioning should identify Sapropel layers.

We may be able to shortly know if the Conowingo Reservoir contains Sapropel as several western reservoir studies now indicate.  If so it would be an interest to those researching estuarine restoration programs nationwide.  A Capstone Project can respond to several research questions for Sapropel in many coastal systems, namely     

1)   Will core studies beneath the Conowingo Reservoir Pond deposits indicate Sapropel.
2)   Does a Sapropel induce a “Sulfide wash” downstream after rain events and pose a threat to fish and shellfish.
3)   Does a current review of the available literature indicate a negative bias for Sapropel research?
4)   Can Sapropel forming sulfur reducing bacteria be cultured in a laboratory setting and identified for further study.

The EPA (Environmental Protection Agency) has recognized the water quality impairment in streams and wetlands (EPA National Risk Management Research Laboratory Forshay and Mayer) from legacy sediment as enriched nutrient pollution in watersheds.  In an article “Effects of Watershed Restoration on Nitrogen in a Stream Impacted by Legacy Sediments” authors describe legacy sediments as “deposited as function of historic mill dam construction.”  The accumulating “legacy sediments” represent another aspect to the Conowingo Dam investigations, has the fall leaves flowing into the Conowingo Pond, especially after strong storms or significant rains events become Sapropel?  After Hurricane Irene and the heavy rains associated with the remains of Tropical Storm Lee evidently washed a large deposit of leaves into the Saugatuck River.  One organization, Earth Place in the fall of 2012 comments on the increase of leaves including the dumping of leaves into waterways.  Dick Harris mentions in a organization newsletter (pg 3 fall 2012) “leaves and yard waste that were thoughtlessly brown or dumped into waterways are now lying on the bottom of our harbors decomposing and forming a black gooey paste that boaters know it as “black mayonnaise. ” When black mayonnaise forms and becomes abundant enough to cover large areas of the harbor bottoms, it precludes benthic (bottom – dwelling) fish from spawning in that area.”

In the 1950s researchers had determined that leaf litter impacted the chemical quality of streams.  In a 1964 United States Geological Survey paper Keith Slack focuses attention to the fact that leaves could impact even the smallest stream pools – “The freshly shed leaves accumulate at the downstream end of pools, where they float on the surface at first but gradually sink to form a blanket over the streambed; later arrivals replenish the surface layer.  Eventually the lower ends of pools become filled with a water logged mass of leaves that may inhibit flow over the riffles – as the waterlogged leaves decompose by bacterial action, the supply of dissolved oxygen in the pool is depleted (USGS Slack, Keith V pg D 181, 1964).  This study also identified the cycling of sulfate to sulfide and the lowest oxygen concentrations where is pools “where decomposition of (leaf) litter seemed to be especially far advanced.”  It is suspected that the Conowingo Pond holds the remains of leaves deposited over the decades.  A question remains if Sapropel has formed deep within them.

Although much public policy attention has been focused towards oxygen poor dead zones (which fluctuate according to temperature) and the impact of nitrogen (TMDL) upon living marine resources.  A far greater and relentless foe however appears to be the Tannin – Sapropel cycle with the presence of sulfur reducing bacteria. 

The following paper describes Sapropel uses of the last century under various names and terms.  Additional reference papers includes Sapropel and Climate Change, and The Cycle of Sapropel and interested Sound School students could review both for developing a capstone research proposal. 

Students interested in developing a Sapropel Capstone Project should check with a teacher of FFA responsibility for assistance and completion of all approval paperwork.
Questions please see the Brochure titled SAE Blended Capstones available in the Aquaculture Office.

Revised for student proposals Sept 8, 2014

This is a foundational fact sheet about Sapropel history and “leaf” digestion in shallow water habitats.  Some of the most frequent observations of brown waters and Sapropel bottoms come from near shore fishers especially shore crabbers.  It is reference material for the Conowingo case study proposal – Tim Visel

The Search for Megalops – Special Report #8 – September 4, 2014
Questions About Sapropel – Potential Impacts to Blue Crab Habitats
The Sound School Regional Vocational Aquaculture Center
A Capstone Project ISSP For Sulfur Reducing Bacteria
Blue Crab Research in Long Island Sound 2014
Tim Visel
Posted on the Blue Crab Info Forum™ and Connecticut Fish Talk™ Saltwater report websites.

I appreciated the responses about leaves filling in shallow estuarine habitats; the past two years I have mentioned those areas which smell bad and have streaming bubbles (Megalops #1, April 1, 2013 and #7, August 16, 2013) as not very productive for blue crabs.  Shallow areas may have become acidic and deadly to Blue Crab Megalops.

For those blue crabbers interested in shallow blue crab habitats a paper about Sapropel bottoms might be of interest.  (IMEP Newsletter #23 The Cycle of Sapropel and Estuarine Habitats). It is found under the Fishing, Eeling and Oystering Thread in the Blue Crab Forum.™ 

Questions about Sapropel –

Composting marine habitats has not been reported much in the recent scientific literature so many fishers have not really heard the term Sapropel, but it describes a sub tidal breakdown process of organic matter similar to that in backyard compost with oxygen.  That is why so many European organic growers now use it. (It is marketed as a natural soil enrichment). Terrestrial growers have long recommended that recycled organic matter (compost) often “be turned” to introduce oxygen for those terrestrial bacterial composers that consume it.  Marine compost contains most of the same soil enriching qualities (once rinsed of salt) and for centuries used for agricultural purposes even here in Connecticut.  Marine composts (humic) in oxygen limited conditions however, have sulfur reducing bacteria and that is the largest difference between terrestrial and marine composts, the type of bacteria within them.  A slippery or greasy feel to Sapropel described by agricultural researchers for over a century, is the remnants of leaf waxes, the relatively long chain hydrocarbon molecules that plants produce to protect the leaf – the “shine” on oak leafs for example that also protects trees in times of excessive drought.  Sulfur reducing bacteria leave the waxes behind (longer chain carbon molecules) and they give Sapropel the blue/black shine or glimmer in sunlight. 

Sapropel as Fertilizer

As early as the 1860s, descriptions of marine mud or mussel mud often contained the phrases of adhesive or sticky (Agriculture of Maine Forty-Fifth Annual Report of the Secretary of Agriculture, 1864). “When first taken out musle (mussel) mud is adhesive and somewhat like blue-clay and must be frozen before it can be spread on land.”  Some farmers reported very good results other mixed but many noticed its sticky consistency waiting for it to freeze.  Once frozen it lost its waxey adhesive features and could be spread on farm fields.

It is that same wax that plagues western farmers today in drip irrigation field out West when Sapropel from reservoirs is introduced into water distribution systems.  It is that wax that “clogs” drip irrigation systems in slow moving lines.  It’s also this waxy characteristic to have such estuarine bottoms noted as “sticky mud.”  Other than leaving waxes sulfur reducing bacteria produce sulfur compounds including acids and some highly toxic sulfide compounds to marine organisms.  Early agricultural use often noted its sulfur content.

Sapropel formation is aided by high heat and lower oxygen conditions driving out oxygen dependent bacteria in favor of sulfur reducing ones. It seems ironic that higher temperatures that favor blue crab reproduction at the same time favors sulfur reducing bacterial reduction. Not that much is known about recent Sapropel as most estuarine studies concentrate on unnatural coastal processes and frequently overlooks the natural impacts that fishers often observe themselves. (Winter flounder fishers were correct about Sapropel habitat change in the late 1970s and 1980s).

The use of marine mud or mussel (muscle) mud as fertilizers appears in New England coastal states experiment station reports for about half a century. The Connecticut Experiment Station appears to be the leader in recommendations. In a July 1917 bulletin (#94) titled “Manure From the Sea” (Jenkins and Street), the Connecticut Experiment Station (New Haven, Connecticut) recommends “1,000 to 2,000 bushels per acre has given excellent results “ (pg.11, Marine Mud section).  It was not only Connecticut following its use by shore farms as a soil amendment and at times a fertilizer. But the dangers of marine mud (Sapropel) were also noted a century ago although farmers did not know why. In a 1885 Maine experiment station report it issues a caution on page 35 in a section titled, “Harbor Mud” and relates the concern of oxygen absent reduction over a century ago.

“This station (Maine Experiment Station) was sent a sample by Fred Atwood of Winterport (Maine) the barrel of mud was received several weeks before being sampled and when it was opened it emitted a strong odor of ammonia.”

In 1903 a Dr. Knoblauch of Cologne, Germany patented an improved process of extracting ammonia from marine mud sediment by simply heating it (The American Fertilizer Magazine, January 1903, Vol. XVIII, pg. 14).  Coastal farmers were often perplexed. Some fields grew tremendous crops of hay while others languished in “mud dust” for years after treatments. A key to the sulfur/ammonia problem was known by just descriptions of odor –a link to age and heat but not well understood by the agricultural community. Today we know that as acidic sulfate soils. Mr. J.I. Stevens of Essex, Connecticut writing to the New Haven Connecticut Experiment Station in 1879 stated “Its effect as a top dressing for lawns and also on mowing land [hay fields] has proved greater for good than anything I have ever seen”. Pg 49, 1879. The same report also includes a caution “The only drawback to the use of the marine mud lies in the considerable proportion of salts, mostly common. Salt, which it contains, being nearly one percent, if thrown out in heaps and exposed to this rain, this salt will be mostly removed.”  The Connecticut (New Haven) Experiment Station also reported that “marine mud” contained high amounts of sulfuric acid “Unlike stable manure and ordinary composts, the mud (marine) contains considerable amount of sulfuric acid” (pg 49, 1879).

In one of the first agriculture references to Sapropel benefiting coastal farmers was from a 1854, September 14th address before the Rhode Island Horticultural Society Industrial Exhibition in Providence by Rev. William Clift of Stonington, Connecticut. In the speech he urges coastal farmers to look into local fertilizers,

 “The marine deposits in the bottoms of your bays, creeks and rivers are made up very largely of these decayed weeds; and could not fail to prove a valuable fertilizer” – and further – “Dead forests of gigantic dimensions lie entombed in them (Marine Humic). In these places the vegetable wealth of centuries is accumulated” and finally, “Let human skill breathe upon these reeking sepulchers of dead plants and they shall wake again to life, beauty and fruitfulness.”

It is the reference to “reeking” --an historical reference to strong stench in this case was most likely toxic sulfur compounds. But the source of Reverend Clifton’s marine mud was the Mystic River (Connecticut) and in the 1860s Professor Johnson of Yale’s Department of Analytical and Agricultural Chemistry had it tested (Peat and Its Uses As Fertilizer and Fuel, Samuel W. Johnson, Yale College, 1866) and it revealed “high levels of sulfate of iron in considerable quantity” – and reviewed detrimental ingredients appears to be “sulfate of protoxide of iron” (p.56). Some farmers allowed it to overwinter and freeze, noticing that the presence of mussel or oyster shells seemed to bring it to fruition much quicker. Professor Johnson (1866) in a bulletin about the use of peat reported it to be mixed with lime and wood ash and to yield the best results,” adding many writers here asserted a hurtful “acidity” which must be converted before “they can be usefully employed.”

One of the reasons why Sapropel is not mentioned today is that the scientific community has had difficulty classifying it – as soil studies reflect mineralization processes and Sapropel is the product of living sulfur reducing bacteria. Estuarine studies refer to it as “sediment” while land application terms include acid sulfate material. This situation has been mentioned in several studies including a paper titled, (Subaqueous Soils: A Pedagogical Approach to the Study of Shallow-Water Habitats, Carl Demas et al, Estuaries Vol. 19 #2A, p. 229-237, June 1996). This quote from the paper’s abstract highlights this problem: “Present classification systems are inadequate because existing paradigm does not actually consider them as soils but merely as sediments” (from abstract). To add to the confusion Sapropel is often referred to as many as twelve different terms including marl, guttja, peat, green vitriol, mussel mud, marine snow, black mayonnaise, ooze, vegetable mold, benthic flux and coquina.

Exposure of Sapropel to oxygen causes the production of sulfuric acid and extremely low pH; sometimes approaching a pH of 2, toxic nearly to all plants (perhaps the only plant that can live in this soil is Phragmites). That is the reason for toxicity to plant life; it burns the root tissue, not unlike its destruction of eelgrass meadows reported in Megalops Newsletter #3, August 20th, 2014.  Is Sapropel responsible for the decline in blue crabs this year?  No, I don’t’ think so, but it may be a part of a long term climate pattern that degrades its habitats for many species of “value” including blue crabs for years. A retired oyster grower on Cape Cod, John Hammond once remarked to me “This stuff is bad for fish and shellfish,” and I agreed.

The Cycle of Sapropel

For blue crabs, a sandy, bivalve bottom and patches of eelgrass has shown to be key to post Megalops survival. The clean and green eelgrass is beneficial to blue crabs and green crabs as well.  Both eelgrass and shellfish also have habitat cycles that depend upon marine soil pH – acidic bottoms therefore, may have a long term negative impact.

The cycle of Sapropel is now thought to be connected to the natural cycle of eelgrass bottom habitats. Sulfur compounds have now been shown to be deadly to eelgrass as well as to clams and fish.  Blue crabs are very susceptible to sulfide bottoms for many years the scientific community has searched for “indicator” organisms that link pollution to habitat quality but one of the first such quality habitat indicators is perhaps Sapropel.  Most fishers have seen it, a soft blue black jelly like material and those that dig deeply into it, find that it emits strong sulfur smells. For decades estuarine studies have focused on the absence of oxygen (we need it also so a bias of “value” exists) and not the presence of sulfur.

It is now suspected that the increase in forest coverage, a warming climate (post 1972) and storm water movement of leaves has assisted the formation of Sapropel. Because this organic input is natural it is often excluded from nitrogen input studies.  A century ago Robert Lauterborn was the German biologist who brought the study of organic wastes (rotting sludge) without oxygen as the studies of “Saprobial life” to main street “science”.  Pollution of the Rhine River in 1900s led to studies of indexing habitat zones to the types of fish they could support.  In this regard it was mentioned that he relied on the experiences of inland fishermen and water authorities to characterize such habitats.  (Melkenion et al Robert Lauterborn 1864-1952 and his Paulinella chromatophara Protist, Vol. 156, August 2005).

For Connecticut it has been the river habitats that have supported the most consistent overwintering of blue crabs.  Tropical rains that started with the tropical storm Lee, then followed by Irene and Sandy may have moved huge quantities of leaves downstream covering former hibernation habitats both smothering crabs and providing organic matter for Sapropel reduction processes.  We may now have Sapropel accumulations and such deposits have been associated with fish kills, providing harmful algal blooms (HABs) with ammonia and sulfide smells. The presence of oxygen may produce very low pH “acid or sour bottoms.”  Sapropel may act as a huge nitrogen sink (storage) that now supplies far more damaging ammonia/nitrogen compounds for algal blooms.

Coastal Connecticut farms long ago used Sapropel as a fertilizer and noticed its high sulfur contents in deep aging deposits.  Deep organic deposits behind dams however were avoided for toxic sulfur conditions.  (CT Board of Agriculture, 1879).  As Sapropel ages it becomes more deadly.  Floods and heavy rains can dig into it and dislodge the toxic sulfides that may have accumulated for decades, rainfall moving toxic compounds downstream.  This event is usually short in duration but at the time very deadly, so without sufficient oxygen causes this deadly sulfide “wash” to flow downstream.  In time, oxygen changes the sulfides into acids. This sulfide release was often caused by ice in winter as tides found these tidal restrictions and speeded up and re suspended Sapropel deposits and the sulfides contained in them.  Warnings about this winter sulfide die offs still appear for Massachusetts coastal salt ponds.

One of the best descriptions of Sapropel harvesting was the digging of “mussel mud” by Canadian farmers to our north. The Canadian Oyster, page 103 printed in 1913 by Jos. Stafford, the Maritime Company, Ottawa) contains a section about its fertilizer use.  It was not a practice supported by oyster growers for many of the reasons listed above and in the process removed many oysters on shells growing over the “mussel mud.” [Several reports mentioned the presence of estuary shell (mussel, oyster clam) as a benefit to the use of this soil amendment.]

“A mud-digger consists of a framework suspending a huge dipper-like scoop with a bale and a long beam for a handle.  The sloop is lowered through a hole dug out in the ice and controlled by men at the end of the beam.  The power is applied through a chain that passes from the bale over a pulley and is wound around a vertical windlass turned by a horse.  The framework may be slid along to fresh places as the old ones become exhausted; the so called “mussel mud” is comprised largely of decaying oyster shells with some mussel clam quahog or other shells mixed with mud, and is used as a fertilizer for the land.”

But Connecticut River area farmers likely harvested it with the same methods and a Old Saybrook farm sold it by the cartload (full carloads delivered, $.25) but they stayed away from the deep accumulations behind mill dams.  A sample of black mud containing some seaweed from saltwater at Saybrook, was sent to the Connecticut Experiment Station by Geo. M. Denison, Esq., (1879) who states that it is exposed at low tide, and can be got upon the land for about 25 cents per load. I guess trial and error came into the process and a description of Sapropel made in 1879 is very similar to today.

Mr. Stevens of Essex also remarks: “Our mill ponds a few miles back from the river, contain a rich, black mud, quite deep and with a very strong smell.  It has been tried on various crops but kills everything. After being hauled and dried it turns from black to white, and puckers the mouth like alum.” (1879) I would match that 100 year plus description against any one made today for Sapropel.

Essex, Connecticut had a small parcel (Sunset Pond) dredged three years ago.  It had become a popular place for summer pond boat races and winter skating; leaves from the surrounds – trees are on the east and west edges were filling the pond and submerged aquatic vegetation (lily pads) growth made these activities difficult and at times impossible. The pond was dredged and a blue black mud (Sapropel) was spread on a grassy hill covering the existing soil.  For the first year, grass growth was a bit reduced as it took some time for the compost to become a part of the top soil, but today three years out, the grass is lush and thick – no doubt benefiting from this soil additive. 

Increases in “leaves” can occur downstream after heavy rains and often appear as a slurry of organic chaf (Cape Cod fishers called this material “oatmeal”).  I have noticed that some recent deposits contain mostly leaf stems; a few kayakers have noticed this soft bottom material in the Essex area primarily in North Cove.  This Sapropel appears to come and go over the past century and comments appear in historical literature that mentions the buildup of this organic material.  This is a reference to North Cove Essex, the site of “marine mud” production in the 1880s.

“In a recent note Mr. Stevens states that the mud sent by him was from a cove or pocket from the Connecticut River; the sediment is brought down in the spring freshets by the Connecticut, the cove connected with the river by a narrow channel. There is no current in it and suspended matters are deposited at such a rate as to have reduced the depth of the water three feet since the remembrance of elderly people”.

North Cove has in the past few seasons supported large populations of blue crabs, especially near recent dredging projects.  It is the deep and old Sapropel deposits in the coastal zone that is a problem; a thin layer seems to improve blue crab habitats, and it like all composts nourishes eelgrass plants but deeper layers kills most benthic organisms including clams, a major part of small blue crab diets.  As deeper layers become separated or “sealed” from oxygen in the water, they contain more sulfur reduction.  What was once good for eelgrass now turns against it.  Prolonged sulfur reduction finds that biological diversity drops and only a few species of primitive worms can survive in it.  As it “ages” toxic sulfide levels increases and the danger of sulfide washes downstream when disturbed.  In other words, in times of low oxygen (heat) it becomes deadly.  One of the coves reported to have the deepest Sapropel deposits at the turn of the century was Hamburg Cove in Lyme, Connecticut. Many boaters have reported deep deposits south of the Hamburg Cove entrance channel recently. Observations of Sapropel deposits would be appreciated especially if a thick blanket of leaves has appeared over once firm and shelly bottoms that had contained blue crabs.

All blue crab habitat observations are important.

Email your blue crab reports to: [email protected].  All blue crab observations are valuable as we learn more about our blue crab population. Questions? Send me an email.

The Search for Megalops is part of a Project Shellfish/Finfish Student/Citizen Monitoring Effort Supported by a 2005 grant to The Sound School from the National Fish and Wildlife Foundation grant #2005-0191-001.

Program reports are available upon request.
For more information about New Haven Environmental Monitoring Initiative or for reports please contact Susan Weber, Sound School Adult Education and Outreach Program Coordinator at [email protected]
The Sound School is a Regional High School Agriculture Science and Technology Center enrolling students from 23 participating Connecticut communities.



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