Friday, February 20, 2015

Female Blue Crabs Go the Extra Mile

The Washington Post recently ran an article on the status of blue crabs in Chesapeake Bay. The first few paragraphs and a link to the full article are posted below. The Post site has a nice graphic of the blue crab life cycle.

 February 12  
Deep under the cold, dark waters of the Chesapeake Bay, the answer to whether the decimated blue crab population can survive lies buried in mud.
Tens of millions of female crabs are scattered across the floor of the lower bay in southern Virginia, where the estuary pours into the Atlantic Ocean, waiting out winter for one of the most important events in their short lives. When spring comes, they will inch closer to the ocean with billions of eggs.
It’s a critical time because the blue crab population is reeling, facing some of the lowest numbers in history. Officials are desperately hoping that steps taken to protect females last year will allow the fishery to rebound from the edge of disaster. But those efforts are also mired in a debate over the best way to protect the crabs.
As females go, so go blue crabs. Last year, scientists estimated that there were only 68.5 million females old enough to spawn, far below the 215 million that officials say are needed to overcome natural threats such as predators and cold — and human threats such as commercial overfishing — without depleting the population. This year’s count is underway by Maryland and Virginia scientists at 1,500 locations.
The blue crab, Maryland’s state crustacean and a symbol of pride for the region as much as a resource, is more threatened now than at any time since biologists started to record numbers in the late 1940s. Both watermen and state officials are deeply worried about blue crabs’ future. Sixty years ago, the Chesapeake Bay yielded 75 percent of the crabs harvested in the United States; now the withered stock yields about 35 percent, according to a report by the Maryland’s natural resources department.
Some watermen say the steps taken by Virginia, Maryland and the Potomac River Fisheries Commission to rescue crabs after the population’s free fall in 2008 haven’t worked. The states cut the number of females that can be fished by about 30 percent. When the stock rose only to fall hard again last year, Virginia cut the number of females that could be fished by an additional 10 percent during the spawning run.
Smithsonian scientists worry that efforts to save females might produce a serious side effect: overfishing males. When male crabs decline, those remaining mate more often, and sometimes can’t regenerate their sperm supply quickly enough, according to a study by the Smithsonian Environmental Research Center.
Read the rest of the article at the Washington Post by clicking here.

Monday, February 2, 2015

American Indians, Colonists had an Appetite for Crabs

Flickr photo by Rhea C has an article about my lab's recent paper on blue crab remains found in Chesapeake Bay archaeological sites.

By John Barrat

Native Americans and America’s early colonists ate many more blue crabs than modern researchers previously thought, according to a team of scientists studying crab remains unearthed at archaeological sites in the Chesapeake Bay area.
Because so very few crab shells have been recovered in archaeological digs in the midAtlantic, anthropologists and others have long assumed that crabs were eaten rarely, if at all, by Native Americans or colonists there.
Now a comprehensive review of 93 archaeological sites across the Chesapeake Bay dating back to 1,200 B.C. has turned up evidence showing quite the opposite.
“I don’t feel confident saying crabs were consistently a dietary staple for Native Americans, but they are found in so many different sites across so many different time periods that we know Native Americans and the colonists were clearly eating them,” says Torben Rick, an anthropologist at the Smithsonian’s National Museum of Natural History. Rick was lead author of a recent paper on the subject in Journal of Archaeological Science.
The researchers found little mention in archaeological studies of the remains of blue crabs in the Chesapeake region, says Matt Ogburn, a crab ecologist at the Smithsonian Environmental Research Center and co-author of the paper. 

“Initially, when we began reviewing Chesapeake sites, we thought we might find 100 or, if lucky, 200 pieces of crab remains and claws to work with. But it turned out there is a lot more out there than we expected,” Ogburn says.

As the paper reveals, by looking into museums and other repositories “we identified and evaluated more than 900 crab remains collected from archaeological sites,” Ogburn adds. The findings ran counter to “the widely held hypothesis that people in the past did not eat crabs,” the scientists say.
“Blue crabs were an important food source for Native Americans, Euro American colonists, and African Americans,” Rick, Ogburn and their co-authors write in their paper. “They are found at a wide variety of site types, including George Washington’s Mount Vernon Estate, a series of plantations and manors in Maryland, a 17th century Native American site, and a 19th-20th century African American domestic site (Sukeek’s Cabin). These crab remains range in age from the early 17th century to the 20th century, suggesting continuous consumption of crabs from prehistoric times and across all major cultural or ethnic groups (Native American, Euro American, African American).”
Why hasn’t previous research found evidence of crabs? The answer is in the shells.  “The blue crab carapace is so fragile and friable that it just doesn’t preserve that well over time,” Rick says.  The shell pieces have often gone unrecognized during archaeological digs.
In this new study, Rick and the other scientists conducted experiments with crab remains showing just how susceptible blue crab shells are to being scattered by scavengers, dissolved and etched by acidic soil, and fragmented into tiny pieces during decomposition and burial. Because the  shells break into such tiny pieces, archaeologists needed special tiny gauge screens to recover the  fragments.
By measuring the excavated the crab parts–primarily pieces of claws and shell parts–the researchers determined that large crabs were more common in the archaeological collections compared to crabs caught in the Chesapeake today.
“Large crabs overall seem to have been quite a bit more common in prehistoric times than they are today,” Rick says. “That’s what we would expect, but it is good to have scientific confirmation that today’s smaller crabs are in part the result of an intensive fishery that removes large crabs from the population.”

Wednesday, January 21, 2015

Discovering the Monster Crabs of the Old Chesapeake

The following article and interview by Tom Pelton at WYPR in Baltimore describes new research from my lab at the Smithsonian Environmental Research Center on ancient blue crabs. Click here for a link to the original WYPR story and podcast of the audio interview. For our paper in the Journal of Archaeological Science, click here.

Discovering the Monster Crabs of the Old Chesapeake

Blue crabs are an important part of the Chesapeake region’s culture, diet, and economy. But crab remains are rare in archeological sites around the Bay. This has led some scientists to believe that Native Americans did not eat the beautiful swimmers that today we find so delicious.
 “What we know about Native Americans ate is based on some historic records, but also on looking at the trash piles that Indians left, mostly on the shoreline of Chesapeake Bay,” said Tuck Hines, Director of the Smithsonian Environmental Research Center. “And the majority of those trash piles are made up of oyster shells. But not much in the way of blue crab remains are generally found in those trash piles or ‘middens.’”
It might make sense that Native Americans did not eat blue crabs.  After all, blue crabs were not a commercially harvested species -- even by European Americans -- until after World War II, when the crab pot was invented as an underwater trap. 
In the century before that, oysters were the most popular food from the Chesapeake.  It the past, highly targeted seafood included terrapin, American shad, and sturgeon -- all of which were over-fished nearly to extinction, until little was left to eat in the Bay except the ornery, edgy blue crabs.
Maybe Native Americans had no reason to mess with blue crabs centuries ago -- because they had so many other, larger morsels of protein they could pluck from the bay with more ease.
The problem with this theory is that records from the 1600’s show that Native Americans were interested in blue crabs as a source of food.
“If you look back at the records of when colonists arrived, and negotiated fishing peace treaties, including hunting and fishing rights in the Chesapeake Bay region, those descriptions and those treaties including rights for crabbing for finfish as well as a collection of oysters,” Hines said.
If Native Americas were negotiating for crabbing rights, why are crab shells missing from Indian archeological sites, while oyster shells and even fish bones are common?  To solve  the mystery, Hines and colleagues at the Smithsonian re-examined old trash piles around the Bay using a new technique.  They used sieves with a very fine mesh.
Scrutinizing historic sites more closely with these sieves, the researchers discovered  tiny fragments  of crab shells in 93 different Native American refuse heaps  around the Bay, some dating back more than 3,000 years, according to an article that Hines and colleagues published last month in the Journal of Archeological Science titled, “Archaeology, Taphonomy, and Historical Ecology of Chesapeake Bay Blue Crabs.”  His co-authors are Torben Rick, Matthew Ogburn, Margaret Kramer, Sean McCanty, Leslie Reeder-Myers  and Henry M. Miller.
Their conclusion was:  Native Americans, in fact, ate plenty of crabs.  But the shells broke down over the centuries, perhaps in part because of acid rain from coal fired power plant pollution in the 20th century.
“The main part of the blue crab that carries forward in these middens are the tips of the claws, which are the most calcified hard part of the crabs,” Hines said.
Analyzing the size of tips of the crab claws they found, the scientists extrapolated how large the crabs must have been. They concluded the crabs caught by Native Americans were much larger than they are now – some twice as large as the typical five inch crab caught today.
“We’ve found middens that contain crabs as large as 10 inches, which is a quite large crab,” Hines said.  “So that’s interesting.”
These giant crabs were not a different species. They just lived longer, because they faced less fishing pressure.  Crabs today typically do not live more than two or three years because most are quickly scooped up by watermen using dredges or pots. Every year, about half of all the adult crabs in the Chesapeake Bay are caught.  But back in Native American times, maybe one percent of blue crabs were harvested every year by people using baited lines and dip nets.
So blue crabs lived as much as twice as long, and grew up to twice as big. Imagine those meaty crab feasts on the Old Chesapeake Bay, with those monster crabs.
The lesson we can learn today from these ancient garbage heaps is that we can have more of what we love if we take less.
(Photo at top of Tuck Hines and blue crab from Smithsonian Environmental Research Center)

Monday, November 3, 2014

2013 Gulf of Mexico Blue Crab Harvest

As on the US East Coast, blue crab harvests declined in most states in 2013. The only increase seen for any state in 2013 was on the West Coast of Florida, and it was a small increase. See my previous post for additional details and a link to the NOAA report on commercial fisheries.

Thursday, October 30, 2014

Blue Crab Fishery Declined Throughout US East Coast in 2013

NOAA recently released its report summarizing commercial fisheries in 2013. The commercial harvest of blue crabs declined in every US East Coast state with substantial harvests. The total US harvest of hard blue crabs decreased about 25% from 2012, although the value actually increased 3%. The full report can be found here. Gulf Coast graphs will follow in a separate post soon. Blue crabs fell to the 15th largest catch of a species by weight and the 9th greatest dollar value.

Thursday, October 9, 2014

2014 Connecticut Blue Crab Report #4

From Tim Visel at The Search for Megalops:

ISSP and Capstone Project
The Sound School Regional Vocational Aquaculture Center
The Search for Megalops - Program Report #4
October 7, 2014
You Do Not Need to Be a Scientist to Report

·        Blue Crabs Set Off Faulkner’s Island

·        Sound School Reports – Charles Neal, Ceondice Johnson, Steve Joseph and Sean Bishop

·        Black Mayonnaise May Indicate Habitat Failure for Blue Crabs

·        Black Mayonnaise Can Lead to Sapropel

  • Conowingo Dam Study and Blue Crabs

Megalops Blue Crab Setting Off Faulkner’s Island Mid-September

For the third year in a row our blue crab Megalops set appeared mid-September, very late compared to 2010 and 2011 crab years and most likely too late to add to our dwindling blue crab population. Between September 12th to 18th, fishers reported black sea bass consuming large numbers of blue crabs about the middle of September almost to the same weeks as last year (Megalops #10, October 2, 2013) (Megalops Special #6, October 24, 2013) and reflect cooler spring temperatures.

Several requests have come in from southern blue crabbers wanting a blue crab habitat assessment from Hurricane Agnes (1972) to present. Storms such as Agnes or now Lee, Irene and Sandy for Long Island Sound are major habitat events especially when indexed for temperature. I will try to look at this over the winter; general trends do appear: a series of cold winters, low catches, gradual warming (but not hot), better catches. I don’t think many blue crabbers will be surprised here. Many habitat assessments, however, do not include soil pore size, grain size, pH and oxygen redox depths. I also look at habitat types and predator/prey relationships. I just don’t know enough about Chesapeake Bay, so I hope a delay is not disappointing.

 I will also delay some assessments for New England until the NOAA models for the North Atlantic Oscillation (NAO) are finished. The NAO has again turned negative, a sign of an early “polar vortex” (a horseshoe shaped storm pattern) and a cold, snow filled winter for us here in New England.  I use the NAO for one of the long-term habitat quality indicators.

New England blue crab populations are hanging on, it’s to early to declare a habitat failure but remaining populations should be considered “residual legacy” as size is frequently an indicator as well as three cold winters in a row. Historically three cold winters in succession were reflected in sharply lower landings. The truth of the matter is deep water sets late in the fall don’t make it and we are fishing on the past year’s survivors. Compare the three-year classes in the July 11th, Megalops #8 2011 report to current reports and the difference is very apparent.

Cooler Waters On October 5th Essex town dock the bottom temperature at a morning still high tide was 62 F at Indian River, Clinton 60 F. Look for crabs to be active in the deep saline holes (traps better than handlines) as they prepare to burrow in for the winter ahead.

Thanks for the emails and comments. All such observations and reports are helpful as we follow blue crab population trend. I do appreciate all the information entering year four of the Megalops habitat study.

Tim Visel
The Sound School

Megalops Blue Crab Set Observed Off Faulkner’s Island

Thanks to Charles Neal of our Sound School for giving me this report of September 12, 2014:

Charles Neal
September 12, 2014

7:30 AM – Friday – I went fishing with my cousins. We went out for a day of porgy and Black Sea bass fishing by Faulkner’s Island in Guilford, Connecticut. We had a good day, but noticed we were catching more sea bass than porgies. After venturing home to prepare fish for a meal, when cleaning the sea bass, I noticed the stomachs had small blue crabs in their bellies. I cleaned four of them and they all had small crabs they had consumed in their stomachs. We were in 70 feet of water and it was about 10:00 AM when we caught the fish. The fish weighed about 3 to 4 pounds each. The blue crabs we found in their stomachs were about an inch point to point about the size of a nickel.

Also fishers reported black sea bass full of blue crabs on September 14 at Long Island Shoal off of Old Saybrook. Steve Joseph, also of Sound School, reporting large black sea bass feeding on mud crabs at the Branford Beacon the same week. Examining gut cavities you can tell much about “what’s around” and this is one way of finding a post Megalops or star set (Special Report #4, April 25, 2014).

Crabs Return to Shore Areas in New Haven – Ceondice Johnson

Ceondice Johnson
Sound School Senior                                                                                      8/18/14

On my nineteenth survey I used one trap, the wing trap, bated with raw chicken. The sky was partly cloudy. I was out for about an hour and caught one large male green crab that was very active and very aggressive. It was about five inches wide.  With the temperatures very warm (75°F), it seems as though the crabs moved from the shallows (no small crabs).


On my latest survey, I used a hoop trap bated with chicken. As the water has gotten less warm, less green crabs have been seen. There has been an increase in snappers and big blue fish. Also not many spider crabs, but they are larger than before. One small blue crab was observed. I haven’t seen a difference in using menhaden and chicken as bait. I also noticed a male fiddler had been picking at the bait also. The first day back at school I noticed many large blue crabs were back along our docks.

Sean Bishop
Sound School
Milford Beach – September 28th, 2014
Cazwall Cove

Sunday afternoon I found a blue crab shell on Anchor Beach in Milford by Holley Avenue. The crab shell was about 6 inches wide (point to point). I found blue crab shells on the beach before but these are the first large ones I have found. The day I saw them they were on the tideline. I check the tideline for sea glass and corals. I have seen live blue crabs swimming around during high tide and in the cervices between the rocks. I suspect blue crabs were still in this area on September 29th.

Black Mayonnaise May Indicate Habitat Failure for Blue Crabs

More and more attention it appears to be gathering around the country as it relates to terrestrial organics and possible roles in habitat failures. High heat can be just as habitat damaging as very cold. It is ironic that energy (storm strength) and duration has huge implications for habitat quality in each temperature range. One of the areas now receiving attention is the accumulation of black mayonnaise in southern areas. Florida recently commissioned several studies regarding the Indian River lagoon, similar organic deposits have been noted on Cape Cod, Boston Harbor and in the Saugatuck River in Connecticut. More recent news about the Saugatuck River conditions seems to have improved. New York Harbor has been looking at black mayonnaise deposits for over a decade.  Western states are looking at it as well. Sapropel formation found on page 22 of CAP Arizona project contains this section.

Arizona is finding that organics behind reservoirs here already formed Sapropel and accumulating waxes ruining irrigation drip equipment:

“The oxygen deficit conditions at the lower depths may cause sediment nutrient release through the process of reduction. If the sediment/water interface is exposed to prolonged periods of anoxia, reducing conditions allow the formation of nutrients previously unavailable for organisms that cause taste and odor changes in the water. This reduction may lead to Sapropel formation, a compound that is high in hydrogen sulfide and methane, and has a shiny black color due to the presence of ferrous sulfide. This compound is responsible for the occasional “rotten-egg” odor associated with releases from the hypolimnion layer through the lower portal on the intake towers.

Nutrients, such as nitrogen and phosphorous, become unbound from their ionic association with metals, such as iron, and manganese. This process may free up nutrients, which contribute to algae blooms in the canal system. Precipitates of iron and manganese cause discolored water and treatment problems” (P.22, 2011 Annual Water Quality Report, Prepared by the Water Control Department contributing efforts by Arizona State University, July 2012, Central Arizona Project).

With studies on Long Island (duck farm organic residues) New York, Florida’s Indian River and Cape Cod’s Buttermilk Bay, we are finding more and more about the black mayonnaise – Sapropel relationship. As we learn more about it and its ability to seal circulation within it (waxes), many habitat pieces that have so long perplexed biologists are now falling into place. Black mayonnaise is the building material of Sapropel when deprived of oxygen. With oxygen it is a benefit to some; with thin deposits nourishes eelgrass patches and good flows, it helps the blue crab Megalops but take away the oxygen and those same eelgrass meadows now become sulfur-killing fields, except near ground waters upwelling on shore fronts

It explains why in the early 1980s sections of Buttermilk Bay on Cape Cod and Eel Pond heavily loaded with black mayonnaise still had surviving populations of Mya, the soft shell clam along tidal edges (shellfish surveys conducted by the Bourne/Sandwich Shellfishers Association). At low tide a reverse hydraulic pressure would release tidal ground water and keep soil pores open to exchanges of oxygen (if this sounds like a sand/bead backwash cycle on a filter system, it is, only a natural one).

Organic patches were backwashed out keeping this “thin band of life” between mid-tide and the low tide line. Below the low tide, the soft shell clams were dead. But just a few feet above they were doing fine. Soft shells are a favorite food for blue crab Megalops. So a light sandy organic matter soil mixed with shell fragments with soft shell clams and eelgrass is prime blue crab star (past Megalops) habitat. Take away the oxygen and crabs move out, and if sulfides increase fast enough, kills crabs through contact (during test pits on the beach detected upflowing ground water; it is cool even on hot summer days).

It is the sulfide layer in winter that kills crabs in place. Cold water allows deep sulfide layers to leach out. Sulfide levels tend to rise to the top of black mayonnaise under ice and crabs now in a hibernated state cannot escapes as they can in the summer. “Sulfide jubilees” here the sulfide kills the minute the Megalops touch the bottom, hundreds of thousands of crabs at a time (Green pond EEL pond observations, Cape Cod, 1982) and the crabs have no defense. It gives the appearance of “winter kill” but freezing did not do it. On the contrary, crabs benefit from the heat in these composts and temperatures directly in them (not exposed tidal flats) rarely drop below 35 F. Even on winter days the black color of these deposits absorb heat as a solar bank to be released at night.

Charles Beebe of Madison illustrated the power of the winter sun to me in 1978. Our 16-foot Brockway skiff was locked in ice in Clinton Harbor and chopping it out each day, well it was taking its toll. After about a week of heavy complaints, he arrived in his green pickup truck with half a bag of rock salt and orders for Ray (my brother) and I to get a bag of charcoal briquettes, a tall order in February. We found some and placed the bag down on the ground. Mr. Beebe proceeded to jump on it. Soon we were circling the skiff in a mixture of ground up charcoal and rock salt. Within minutes (it was noon) crackling and popping happened. The ice sagged and then broke; the skiff was free. He left muttering something like “I need to teach you both everything.”

In 1988, George McNeil of Clinton gave a similar account of saving the oyster boats at City Point, New Haven, Connecticut (then Oyster Point). In 1931, several oyster boats were locked in deep ice, only this time it was coal dust at the end of South Water Street from a coal business, mixed with rock salt. The heat plus the salt did the trick; he chuckled when he heard of Mr. Beebe’s charcoal briquettes – same idea. The point is, black mayonnaise can absorb tremendous amounts of heat, and if deep enough, kick start the Sapropel process. Eelgrass at the end helps in developing these killing fields (sorry to all the eelgrass reports, but the eelgrass habitat history is very mixed as much good as bad in our area).

This is a quote from an article last February investigating mysterious die-off of eelgrass from the University of Copenhagen (Jens Borum) and Marianne Holmer from the University of Southern Denmark:

“The biologists explain that ‘eelgrass plants trap the mud’ that is washed away from chalky seabeds, and they also trap the poisonous sulfides. The high concentration of sulfides that is trapped in the midst of the older eelgrass that is less capable of withstanding the effects of the poison gets killed off, leaving only eelgrass that encircles the deposits of sulfide-rich mud. They state that the fairy circles of eelgrass (death) caused by the build up of sulfides is also found elsewhere in the world’s oceans.”

At the turn of the century, during intense heat, David Belding, a renowned shellfish biologist then, gave an account of the impact of organic matter upon marine soils and his 1910 report is just as valid today. He found many other biologists during this period the habitat change aspects of sulfide:

 “Organic Material: Clams are usually absent from soils containing an abundance of organic material. Even if the slimy surface does not prevent the set, the clams that take lodgment soon perish. Organic acids corrode their shells and interfere with the shell-forming function of the mantle. Such a soil indicates a lack of water circulation within the soil itself as indicated by the foul odor of the lower layers of soil, the presence of hydrogen sulfide, decaying matter, dead eelgrass, shells and worm. If such a soil could be opened up by deep ploughing, or resurfaced with fresh soil to sufficient depth, it would probably favor the growth of the clam. 

 Soils in which organic acid caused by vegetable decay, are present prove unsatisfactory for the catching of seed and interfere to a slight extent with growth by destroying the shell, often giving to the clam a black appearance which makes it less suitable for marketing.” (A Report Upon the Soft-shell Clam Fishery of Massachusetts Including the Life History, Growth and Cultivation of the Soft-shell Clam (Mya arenaria), David Belding, MD Biologist, 1910)

Several crabbers have noticed bubbles coming off leaf deposits (mostly methane) (Megalops #7, August 16, 2013) and deep leaf accumulations as poor crab habitat. In high heat the gas becomes hydrogen sulfide; the rotten egg odor of coastal areas when it is hot. That is why most large fish kills are preceded by accounts of smells of sulfur and mostly occur during hot and low energy periods. When oxygen is low, the toxic sulfur cycle resumes and the first toxic impacts are to the benthic bottom dwellers and dead crabs. John Hammond, a retired oyster grower on Cape Cod, used to say this stuff is bad for the fish and fishers; it is. When sulfur levels get high, blue crabs may walk out of the water, most benthic organisms can’t do that. Down south in the historical literature, they were called “jubilees.”

But even here they happen in extreme heat in New England Niantic Bay had a small jubilee accompanied by sulfur smells [Crabs Pick Land Over Niantic Bay, August 7, 2009, WTNH, Jamie Muro] and the infamous August 1898 die-off of Narragansett Bay, Rhode Island contains similar accounts. I agree with Dr. Scott Nixon who in 1992 said that a century before the account of A Meade could not be improved. I also agree and repeat Dr. Mead’s account here as it first appeared in 1898 after a long heat wave.

“On the 8th and 9th of September the water became extremely red and thick in various localities from East Greenwich to Providence, and the peculiar behavior of the marine animals attracted much attention. Myriads of shrimp and blue crabs, and vast numbers of eels, menhaden, tautog and flatfish came up to the surface and to the edge of the shore as though struggling to get out of the noxious water. Indeed, the shrimp and crabs were observed actually to climb out of the water upon stakes and buoys and even upon the iron cylinders which support one of the bridges and which must have been very hot in the bright sun…”

 When you read these accounts, they often share the same features within case histories: 1) a sudden or severe period of rain during extreme heat, 2) chocolate, purple or red waters, 3) algal blooms, 4) sulfur smells, 5) fish kills and 6) black waters. The smell of hydrogen sulfide or the rotten egg smell is mentioned in 9 out of 10 cases. Sulfur compounds are highly toxic and over time can be the source of “natural pollution” that kills finfish and shellfish.  Black mayonnaise, fresh organic marine compost is deprived of oxygen and turns deadly into Sapropel, creating sulfide waters.

A sulfide block is now suspected of impacting some coastal alewife runs. Although a Sapropel bottom has become in many areas a dominant habitat type and may signal a massive habitat reversal; we know very little about recent deposits. It just has not been a process of habitat change, which until recently focused almost entirely upon man-made pollutants. Anyone who has noticed an increase in leaves over previously firm bottoms or deposits that give off sulfur odors, drop me an email. All bottom habitat type observations are important as we learn more about habitats that may or may not support Megalops (blue crabs).

Black Mayonnaise Can Lead to Sapropel and Toxic Compounds

As mentioned in Special Report #8, the first accounts of the toxic impacts were from the agricultural community with older Sapropel, the built up organic matter behind dams. The New Haven Agricultural Experiment Station tested several sources of marine mud used as fertilizer and found it contained a high sulfuric acid content, four times that of “regular” stable manure (Report of the Connecticut Experiment Station, 1879).  As this organic matter collected deposits above effectively sealed it from oxygen in the water column. In time as the deposit deepened, the bottom layers became Sapropel and sulfur rich. Dredging in the coastal zone frequently removes these Sapropel deposits and is much of the reason after dredging projects local fishers often report improved fish catches and firmer bottom conditions after the source of sulfide waters are removed. Sapropel builds behind dams in high heat, or in in the marine zone behind blocked coastal inlets or above bridge and railroad tidal restrictions. It was the winter flounder fishers of eastern Connecticut in the 1980s who first grew concerned over deepening deposits of black mayonnaise (IMEP#15, 1and 2, April 2014) over bivalve flounder nursery habitats, which eventually signaled a huge winter flounder habitat failure. European organic matter pollution a century ago created an entire habitat classification system, the Saprobien System, in 1909.

One of the best current case histories of Sapropel (called sludge) is regarding the Long Island, New York duck farms which discharged into small creeks and bays collected on the bottom (Long Island Duck Farm History and Ecosystem Restoring Opportunities, Suffolk County, Long Island, New York). Here these bottom sediments become Sapropelic and shed sulfide and ammonia, nutrient for harmful algal blooms (HABS).  They rot in high heat and lower oxygen conditions and when sulfate bacterial reduction shed hydrogen sulfide gas (H2S). The presence of this “benthic flux” has been associated with the increase of the brown algal strains, which can directly utilize area (ammonia) nitrogen compounds. Descriptions of the benthic flux follow the patterns (descriptions) of fisher observations a century ago described by Mead, Narragansett Bay 1898 and later, Gaines for the Narrow River in Rhode Island, (1988). Sapropel and its impacts to bottom habitats has not been discussed for decades.

This description of page 16, Appendix D, February 2009, U.S. Army Corps of Engineers Duck Sludge fits the description provided by Stevens of Essex nearly a century before (North Cove, Essex, Connecticut, Marine Mud Harvests, 1879).

    “These organic rich sediments, often several feet deep, became soupy, black, clayey silt that had a rich odor of hydrogen sulfide, so potent that home owners adjacent to Moriches and Great South Bays complained that the paint on their homes were being discolored (Nichols, 1964, O’Connor, 1972)”

 And with decreased habitat energy (tidal flows, restrictions) smells got worse as experienced by other barrier split/ inlet systems, further descriptions (I bid) is provided by the comment below:

“Ecological degradation that was associated with the accumulating of nutrients throughout the estuarine bays continued throughout the history of the duck industry, and was heightened when the Moriches inlet was closed (Nichols, 1964 Lively et al, 1983) in the early 1950s.”

Sapropel habitat concerns are just not marine; the original classification of organic pollution, both natural and man-made, was developed in fresh water rivers (IMEP #23, August 29, 2014 – All IMEP Habitat newsletters can be found on the Blue Crab Forum™ – Eeling, fishing and oystering thread and CT Fish Talk™ Saltwater Reports, 1909). Sapropel can accumulate and show the basic characteristics in fresh water as (Megalops Report#8, 2014).

This is a description of Sapropel from a 1997 Arizona CAP study of reservoir and canal irrigation system. System managers were concerned with “organic rain,” organic matter that forms a sediment that when disturbed releases hydrogen sulfide, changed the odor and taste of water. In summer heat these water reservoirs have periods of anoxia and organic matter reduction occurs in the bottom sediments. It is a natural condition enhanced by high heat and increased biomass (organic) rains. Releases of Sapropel slurry into water distribution systems led to water customer complaints (odor and taste) and were implicated in filter system failures and clogging (waxes) agricultural drip irrigation equipment.

Water system operations soon launched “investigation” studies seeking answers to these complaints. Eventually the problem was linked to bottom water releases. In summer large bodies of water tend to stratify, surface warm water on top and colder water below (visitors to lakes in Maine will identify with this while swimming). The colder water below will become anoxic (oxygen limited) while organic debris inputs are now (grasses, leaves, woody residues from forest soils) and washed into water bodies. When that happened, waxes formed a byproduct of “leaf digestion” and the waxes clogged irrigation equipment.

Results from sampling trip to Lake Pleasant (Arizona):

“The anoxic conditions that occur in the hypolimnion during summer thermal stratification in most lakes are a result of high epilimnetic biomass that “rains” through the metalimnion and thermocline becoming trapped in the hypolimnion. This may lead to increased BOD in the hypolimnion and, therefore, an oxygen deficit. The oxygen deficit may have profound impacts on water chemistry and composition. If the sediment is exposed to prolonged periods of anoxia, reducing conditions may prevail. This may lead to the formation of Sapropel. Sapropel is high in H2S and CH4 and has shiny black color due to the presence of ferrous sulfide. This has been anecdotally referred to as the “rotten-egg” odor associated with high levels of discharge from the hypolimnion into the Waddell forebay. During the fall overturn, large amounts of sediment may be disturbed and entrained in the outlet ports of the towers.”

This is the report of Robert DeGoursey describing of black mayonnaise deposits in the Pattagansett River in August 1988 of East Lyme, Connecticut (Shellfish Survey with Gasoline Jet Pump):

“Robert E. DeGoursey, UCONN Dive Team Leader
Diver/ Video Survey of the Upper Pattagansett River Estuary, East Lyme, Connecticut

16 August 1988      UCONN Marine Sciences Initiative

Transect 3- 50 meters north of the Amtrak bridge

Area Surveyed: Approximately 25 meters in the center of the river proceeding west to east.   Depth: 1 meter

Sediment type: “All sediments observed were very fine grained, soft, unconsolidated and easily re-suspended. Divers could easily penetrate the bottom by hand to 1 meter with little resistance. No hard substrates were located. The surficial layer of sediment was oxygenated to approximately 1 cm. Characteristic H2S odor was produced when sediments below the redox layer were disturbed.”

A further second examination with the use of a hydraulic gasoline water jet pump revealed a buried oyster bed at 2 meters depth. The relic oyster shells were brought to the surface with glass shards, coal cinders and clinker chunks (thought to be remnants of steam trains coal refuse), an old bottle and the leather remains of an old shoe. Closer to the Amtrak causeway water high pressure fluidization did not allow divers reaching down far enough to pick up oyster shells. The UCONN dive team (Peter Auster, Bob DeGoursey) estimated that the high pressure water jets had removed about 1 meter from the surface, the pipe held into the hole had allowed divers to pressure fluidize about another meter with additional lead weights had penetrated another meter and the arm thrusts that had perhaps added about another meter. Any shell debris or relic oyster habitats had to be at least 3 meters and deep or more. Efforts to further examine this habitat history were suspended by high amounts of hydrogen sulfide gas being suspended in the immediate area (T. Visel personal observation).  This organic substance had most likely putrefied in high heat and then formed a layer of Sapropel.”

We were looking at black mayonnaise not realizing that at about 6 feet of depth it was Sapropel, the bacterial reduction of organic matter created without oxygen; the sulfur cycle and generating all the sulfide gas. Elizabeth Craig of the Norwalk River Watershed Association in her article “Good News From Norwalk Harbor: Flounder Population Recovers” (In the Mainstream newsletter, Fall 2013) sums it up for the rebound in winter flounder in Norwalk Harbor:

“Residents and homeowners in the Norwalk River Watershed, especially those living along river or stream banks, continue to play an important role in keeping Norwalk Harbor and the Sound healthy, so here is your friendly fall reminder not to dump leaves into the River or storm drains and wetlands. While this leaf litter is ‘natural,’ organic and biodegradeable, in excessive amounts, as it decomposes, it uses up most of the dissolved oxygen in deeper water and makes the bottom water uninhabitable for fish and other animals. Leaves and yard waste blown into the river and wetlands form a black gooey paste known to boaters as “black mayonnaise.” When black mayo forms and becomes thick enough, it destroys spawning areas of bottom dwelling (benthic) fish such as flounder. Unlike many fish that spend their time swimming, benthic fish are very dense and have negative buoyancy, which allows them to lie effortlessly on the ocean floor or bury themselves, like flounders and sole who can remain hidden in sand because of their flat body shape.

Leaf litter is known to gardeners as “Black Gold.” Used in your garden to enrich soil, it is black gold, but dumped into the river, these same leaves settle on the harbor’s bottom and become the notorious ‘Black Mayonnaise,’ destroying important fish habitat.”

The sulfur cycle and its deadly habitat impacts are not found in many estuarine studies (a bias reflected perhaps in the not so nice eco-biological services of such deposits), but black mayonnaise exists and its deeper more toxic counterpart Sapropel does also.

Conowingo Dam Study and Blue Crabs

 The Conowingo Dam study offers a unique opportunity to examine the long-term organic digestion of leaf material (contrary to many published studies, leaves form most of the nitrogen sinks in estuarine waters) in the sulfur cycle. This dam no doubt trapped leaves coming down the Susquehanna River and with tannin signatures (See IMEP #23, #26 Blue Crab Info™, Fishing eeling and oystering thread), we might be able to distinguish the organic source material fingerprints of what comprises this organic deposit.

The Conowingo sediments should have leaf paraffin that seal these deposits with increasing depth. Cove profiles (deep cores) below 12 feet should show elevated sulfur levels. The sulfide problem was described by oyster farmers here a century ago who noticed that the teens oyster shell was dissolving quicker in these “black bottoms” (George McNeil) and this material may signal increased shell loss for the oyster industry. * Blue crabbers are justified in their habitat concerns; the Conowingo sediments may tell us more about Sapropel formation than the Indian River Florida Black Mayonnaise Study currently underway. Due to the fact that the Conowingo has unconsolidated sediments (loose), some exceptionally deep cores are possible (no boulders). Since we know the age of the dam, we can tell how quickly Sapropel can from and such deep cores could tell us much more. Dislodged Sapropel deposits release sulfur compounds that quickly turn into sulfuric acid. A sulfide wash is toxic to most organisms including blue crab Megalops. Acid bottoms in high heat dissolve bivalve shell and may explain sudden soft shell clam failures as well; a favorite food of young blue crabs. Acid waters could be part of the loss of shell on oyster bars as well.

This Chesapeake Bay habitat study of Conowingo Pond could be the most important review to date. It could tell us much more about how sulfide impacts blue crab habitats. Next newsletter will detail cold-water habitat failures.

*Some of the first export organic matter studies from estuarine marshes were conducted in Chesapeake Bay. David Correll in Estuarine Productivity (Chesapeake Bay Center for Environmental Studies, Smithsonian Institute, 1978) reported export from tidal marshes of 200 grams of organic carbon per year per meter (p. 647). The Conowingo is watershed source entirely and tannin signatures (source) from organics not mixed with marine source organics. Therefore identifying sources should be all terrestrial, etc. – a clear look at Sapropel formation.

Thanks again for your interest and support.

Tim Visel

Every observation is valuable as we learn more about our blue crab population.

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

The Sound School is a Regional High School Agriculture Science and Technology Center enrolling students from 23 participating Connecticut communities.

The latest Search for Megalops (blue crabs) newsletters can be found on The International Blue Crab Blog Spot™, The Blue Crab Info™ Forum (Northeast Crab Resources) and Connecticut Fish Talk™ Salt Water Reports.

Email your blue crab reports to:

If interested in helping with the Blue Crab Census, please email me at and register as a volunteer. 

Thursday, September 18, 2014

2014 Connecticut Blue Crab Special Report #8

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
Tim Visel

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:  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

The Sound School is a Regional High School Agriculture Science and Technology Center enrolling students from 23 participating Connecticut communities.