From 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
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 an 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 an 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” a 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 Pedologic 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 an 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@example.com. 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.
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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 firstname.lastname@example.org
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