EC # 31 Part 1 Salt Marsh Dieback Linked To Sulfide Formation

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EC #31 - Part 1: Salt Marsh Dieback Linked to Sulfide Formation
Salt Marshes and the Chemistry of Climate Cycles
The Nitrogen Bacteria Series - March 2020
Higher Salinities Changes Edge Vegetation
Sea Level Rise Brings Salt Water Inland
Sulfide Soil Levels Key to Habitat Research for Eelgrass
Salt Marsh Vegetation Die Back Linked to Sulfide Generation
Viewpoint of Tim Visel – no other agency or organization
This is a delayed report
 
Tim Visel retired from The Sound School June 30, 2022
The Nitrogen/Bacteria habitat series has had over 150,000 views to date

 

A Note from Tim Visel
 
My employment on Cape Cod had me visit the Woods Hole research labs of NOAA and the Woods Hole Oceanographic Institution many times.  On several occasions these visits yielded field research surveys with Dr. Arthur Gaines and sometimes a car ride with Dr. Donald Rhoads.  Dr. Rhoads of Yale University who I met in 1978 during a short work internship with a DAMOS dredge material project in New Haven, Connecticut and in 1979-1980 I would attend meetings at the University of Rhode Island with Dr. Gaines while working for ICMRD then a URI international education effort for marine resources.  The car pool trips back to Madison, CT had me in the car with these two distinguished benthic researchers: Dr. Rhoads for the study of benthic carbon sediment processing and Dr. Gaines for sulfide sediment generation in salt ponds.  I recall one conversation in which we discussed the Narrow River (Pettaquamscutt Lake Shores) in which Dr. Wayne Durfee (URI) had me respond to a call to his office from Bruce Rogers about an oyster die off in September 1980.  It was very warm and the bad smells were associated with a massive oyster kill.
 
The Narrow River 1980
 
On the shores of the upper salt ponds of the Narrow River a huge die off of oysters occurred and the smell of sulfide very evident.  The oyster shells I observed were stained black (later I would learn the result of iron sulfide staining).  I met with some neighbors who described a strong sulfur odor just before the oysters died.  It was a warm fall and explained that warm water holds less oxygen and most likely the upper pond suffered from low oxygen for which very little could be done.
 
When asked why it happened (the black water, dead oysters and strong sulfide smell) in the summer ... I explained the thermocline formation that I learned from Florida Institute of Technology oceanography classes a few years before.  As spring ended, waters warmed and formed a surface warm layer over top a saltwater denser layer.  As this boundary became stronger as the summer heat progressed, a strong thermocline "locked" the bottom water from oxygen exchange (often termed "a renewal") from air or oxygen diffusion from phytoplankton.  The bottom layer becomes oxygen-starved, especially as warm water can hold less oxygen and the use of sulfate (enormous amounts of sulfate are available in seawater) by bacteria, which frees the sulfur.  One of the best (and easiest to understand – my view, T. Visel) explanations can be found in a fact sheet titled "Invisible Engines of the Salt Marsh" printed by the Tidewater Institute of Old Saybrook, CT.  This two-page fact sheet sponsored by the Yale Center for Coastal and Watershed Systems and Sea Grant CT in the 1980s describes the bacterial processes in tidal salt marshes of digesting plant tissue by bacteria as "Invisible Engines."  A small section on bacterial processes is included below:
 
"Specialized bacteria work in the saturated soils of salt marshes and carry out chemical reactions in these soils that are called redox reactions.  Redox stands for oxidation-reduction; one cannot happen without the other.  This process refers to the chemical exchange of electrons between one element and another in the soil, and results in a number of chemical reactions that release energy.  This process is what is happening when soil bacteria eat the organic matter that originated as our familiar salt marsh plants.
 
Redox reactions are more familiarly known through such everyday processes as the tarnishing of silver (corrosion), and the series of reactions that occur when iron or steel rusts.  Oxidation-reduction reactions are the most important reactions in saturated soils, like those found in the salt marsh.  Redox reactions are responsible for turning sulfate, contained in seawater, into sulfide in marsh soils where there is no oxygen.  This produces that familiar rotten egg smell of the marsh.  In this case, sulfur-reducing bacteria in the soil water derive energy from combining sulfate with organic matter to produce Hydrogen Sulfide (H₂S).
 
Redox reactions are responsible for many other chemical processes occurring in salt marsh soils – both in the presence, and absence of oxygen – and in conjunction with the billions of bacteria that also thrive there.  Bacteria are the most abundant and diverse organisms on earth, performing a multitude of functions, many in extreme environments.  If you stir up some salt marsh mud and smell sulfur in the air, you may be able to see bacteria – thin layers of green, purple or deep black." (from a fact sheet coauthored by Judy Preston)
I was familiar with this bacterial chemistry of converting nitrogen as in the early biological filters used in aquaculture.  Therefore, the best time for this sulfur smell to happen is summer peak heating at the end of August, the worst time for summer visitors.  I will never forget the thousands of small oysters, meats rotting in the hot sun in these salt ponds.  In later years in the colder 1960's, it was the fall collapse of the thermocline (described as an overturn) was so sudden that it brought black water and even bottom leaves to the surface.  I was able to locate Rhode Island reports that described these violent overturns – and issued reports after them for the public.  These reports mentioned smells and discolored waters but generally did not mention the composting aspect of these salt ponds as bacteria consumed organic matter and unlocked the nitrogen compounds contained in them.  Huge amounts of phosphorous and nitrogen (often described as "hard nitrogen") are stored in the plant tissue, both marine and terrestrial.  The visual impacts were hard to ignore.  In the spring, these ponds had living oysters and the visibility was very clear, only to see the black iron sulfide stains in late summer.  Since this time, the Narrow River "overturns" have been somewhat spectacular – October 2007 – Purple Waters in the Narrow River, October 2020 was so strong that a milky white river could be seen from the air (Narrow River Preservation Association report).
 
In 1974, I had seen similar black shells and dead shellfish.  This had happened in Tom's Creek, the small creek next to my family home at Webster Point, Madison, CT.  After long storms and large waves, the shore waters would also have a grey tint or color.  This is also from large waves suspending this grey stain from iron sulfide, the result of sulfate-reducing bacteria.  (Tom's Creek was closed to direct shellfishing from high bacterial water tests.)
 
By the time I started working for the Cape Cod Cooperative Extension Service in 1981, I was familiar with sulfur-sulfide staining of bivalve shell.  The iron sulfide changes in some of the Cape Cod salt ponds, especially Green Pond, were similar as stains were observed on soft shell clam shells.  These dead clams were also stained black.  The Narrow River was the site of 1975 PhD research for Dr. Gaines.  My contribution during this carpool was that an organic compost was suffocating oysters and clams in a creek in Madison (Tom's Creek).  It was during these trips I learned about sapropel.  A few years later Dr. Gaines and I would both look at sulfide – as a sign of benthic suffocation and the bacterial production of toxic sulfides.  Several discussions involved how much human activities had influenced the surge in sulfide as compared to natural events. 
 
A 1991 study by Dr. Gaines mentions this aspect – that sulfide formation (sulfate metabolism) is largely a natural composting bacteria process.  From "Value Judgement and Science in Costal Management – The Case of Anoxia" – Arthur A Gaines, Jr. Marine Policy Center Wood Hole Oceanographic Institution – from Woods Hole Oceanographic WHO1-90-21 New England Salt Pond Data Book by Anne E. Giblin June 1990 pg. 18 has this statement:
     
"A related matter is the accumulation of organic sediments in coastal ponds.  This material has a consistency sometimes described as "black mayonnaise" and typically smells of hydrogen sulfide.  Commonly, high organic sediment is believed to suggest pollution and several coastal communities have proposed removal of these sediments or their burial under clean sand.  As indicated in the Narrow River sediment study, this kind of sediment has been deposited naturally in both fresh and brackish basins since glacial ablation over 10,000 years ago."
 
This natural process is often described as "sulfate metabolism" the bacterial use of sulfate as a source of oxygen.  This bacterial change of oxygen reducers to ones that use sulfate is influenced by heat as shallow, warm waters naturally contain less dissolved oxygen. 
 
They would dramatically alter the relationship between nitrate, nitrite and ammonia.  Each of these nitrogen compounds will be influenced by the amount of elemental dissolved oxygen is present – bacteria species would feed upon dead plant tissue and the fastest bacterial composters were those that could mobilize oxygen directly from the water.  Ammonia would be oxidized by other bacteria and produce nitrate and nitrite compounds.  In the absence of oxygen, ammonia levels would build up.  In very low oxygen conditions, bacteria would turn to oxygen substitutes, compounds that contained oxygen but would require energy (breaking bonds) to obtain it. The easiest was nitrate and nitrite and those in seawater would show declines as ammonia and ammonium ions increased.  Those would provide a nitrogen source to different types of bacteria – the blue-green bacteria often termed cyanobacteria.  People living along salt ponds (and freshwater ponds with high organic (leaf) inputs) can experience these thermocline bacteria and rarely see white or sometimes "purple waters."
 
Sulfate metabolism would put salt marshes at the center of bacterial sulfide generation.  Salt marshes reflect the composting of organic matter as deposits reach the level of surface vegetation.  This often led to contrasting bacterial processes described as the "high marsh" where the peat water table was lower and allowed oxygen to be more available – versus the "lower marsh" where a higher water table (soil saturation) meant a shortage of oxygen and a greater chance of sulfate being used as an oxygen source.  Terrestrial farmers long ago in Europe had altered this bacterial relationship by building "Mounds" of water-soaked peat.  Once dewatered, they could support agriculture.  A report titled Cultural Entities Denmark, The Marshland at Brede, A. Lindhort and Frederiksen (2001) mention mound builders for agriculture, and lowering water tables could cause some areas to sink (See IMEP #68-A Sapropel and Habitat Impacts, posted Dec. 12, 2018, The Blue Crab Forum^TM).
 
The salt marshes of our coast seen today reflect thousands of years of bacterial composting.  The increase of heat and lowering of oxygen speeds the formation of sulfide and the digestion of peat.  With sea level rise greater amounts of sulfate now is available for the bacteria that can use it.  That is how sulfate turns salt marshes into poisoned waters.  In very hot conditions, the generation of "black water."  This condition is found in salt ponds that act as heat sinks.  Dr. Gaines in a 1986 – Lagoon Pond Study – looks into the condition of a shallow water tidal pond – in Lagoon Pond – Martha's Vineyard from "Lagoon Pond Study, An Assessment of Environmental Issues and Observations on the Estuarine System" WHOI Proposal #3599).  Page 18 has this segment: (Note – these salt ponds can be described as poorly flushed, T. Visel)
 
"In anoxic aqueous environments hydrogen sulfide can accumulate to very high levels and during periodic ventilation events the sulfide reaches the surface and can be smelled over a great distance."
 
This is the sulfide "deadline" in water and in soil that can be detected by our senses.  Knowing the level of height of the sulfide deadline is key to understanding the impact of sea level rise upon salt marshes and small bays and coves.  When the water contains high level of sulfide, sulfides become airborne and recorded as the smell of "rotten eggs."  What was a concern is that sulfide events on the bottom could happen at night and could not be detected by smell.  Such events could be deadly and yet go unnoticed or blamed on things not connected to bacterial actions.  This is how sulfide becomes the "silent" killer of seafood.  Perhaps one of the few indicators of sulfide toxicity is a bottom dweller – the blue crab.  The oxygen minimum occurs in our region about 2:00am to 4:00am in the morning.  The lack of sunlight turns off the oxygen producing "algal pump" at sunset allowing bacterial composting to slowly drawdown dissolved oxygen in the dark – as dissolved oxygen becomes scarce other bacteria use sulfate and release sulfides into the water.  Sulfides interrupt oxygen respiration in fish and can damage gill tissue.  Sulfides can also impact benthic shellfish as sulfide is detected shellfish stop filtering sea water for food.  Blue crabs have adapted to this evening low oxygen event, especially in late summer as warm water contains much less dissolved oxygen.  This explains the tenancy of blue crabs coming to the surface at night the "pole crabs" of late summer.  Sunlight at dawn restarts the algal pump, allowing oxygen depletion conditions to lessen and crabs return to the bottom.  In the historical fisheries literature, this is known as "torch lighting" for blue crabs.  In 2011 to 2012 this night time blue crabbing became very popular in dredged basins and marinas.  Docks at night became crowded with "pole" crabbers that several marinas had to limit access.
 
In 2013, I exchanged several emails with Dr. Gaines and he provided several additional reports for my sulfide research.  Oxygen Depletion In Connecticut Estuarine Waters – Final Research Reports, January 15, 2003.  At this time, I was reexamining climate cycle influence a positive NAO for intense warming of coastal waters.  One aspect other than "pole crabs" (blue crab) was the surface die off of small marsh vegetation.  I reference the research of Dr. Wade Elmer at the Connecticut Agriculture Experiment Station (New Haven, CT), "Response of Sediment Bacterial Communities to Sudden Vegetation Dieback in a Coastal Wetland" Elmer and Thiel (2017).  The report has this comment, my comments (T. Visel):
 
The vegetated sediments (Spartina meadow – T. Visel) harbored significantly higher populations of Bacteroidetes, related bacteria (gram negative bacteria that obtain energy from plant tissue) whereas the sudden vegetated dieback affected sediments contained a significantly enriched relative abundance of sulfate reducing, bacteria predominantly within the genus Desulfobulbus."
 
Knowing the sulfide deadline (the height of sulfide richness in peat soil pores) is key to understanding fish and shellfish habitat loss from sulfate bacterial composting.  That lesson I learned from John Hammond a retired oyster former on Cape Cod.  He was the one, who termed it the "sulfur deadline."
 
Introduction

The topic of several posts is the habitat successional aspects of climate cycles. In warmer areas, the habitat areas of some trees and plants show they have adapted to saline conditions and the low oxygen conditions of submerged peat.  These estuarine conditions provide huge quantities of sulfate needed to sulfate reducing bacteria to break down dead plant tissue.  Some plants however have adapted to high sulfide conditions from bacterial discharge.
 
When I studied at the Florida Institute of Technology at Jensen Beach Campus (now closed), I would walk along sandy areas adjacent to the campus (there were a few hundred yards east of the Ralph S. Evinrude Mechanics building) and wonder about the roots of the red mangrove trees where small sailboats were stored. Small oysters grew on the roots of these trees and on occasion I would see a large blue crab or two.  Here was a tree that grew, in salt water, had roots fan out like a comb and hold any leaves and twigs as its own compost source.   Where these trees grew out into the Indian River, this patch of sand where the sailboats were stored was free of them (most likely cleared to facilitate the launching of these boats, including the Sunfish^TM, which I was able to use (as I helped install and patch some drywall in the mansion building next to the beach).  The two edges of this small beach had two mangrove trees, they also contained many more fish.  Several times, I tried a small minnow seine for some potential bait but fish quickly darted back to the shade and protection of these roots.  These roots made fishing or seining impossible sort of a habitat refuge area, low energy organic rich environments, which to me acted more as a reef than a marsh. And the waters were very warm much warmer than Connecticut, adding to the chemistry of a tree that could live in saline conditions, surrounded by sulfate.
 
The standing vertical profile of wood root structures are now recognized as significant to many species. They slow the movement of organic matter while providing habitat for dozens of species that live on or near the roots.  There are just hundreds of reports about the value of this shady wood structure to fish - they need not be repeated here.
 
It is the soil chemistry of these areas however that provide insight to climate cycles and the rise and fall of fish species - low oxygen in the production of hydrogen sulfide in these high organic areas.
 
We do not have mangrove fringe habitats in New England that bind over time organic matter into a peat, here in New England it is salt marsh "hay" or cord grass. Although we lack the mangrove, the chemistry of plants that bind and create peat appear remarkably the same - adaptation to high salinity low oxygen habitats, those that are bathed in sulfate twice a day by tides.  What distinguishes these plants, mangroves, sea grasses and peat grass (salt marsh hay) is the chemistry of survival is dependent upon temperature and to some extent the presence of nitrate and sulfate, two oxygen containing compounds.
 
It is a unique and different root structure that protects the ionic exchange of nutrients and the toxic impacts of sulfides. The root tissue is able to create a field of oxygen requiring bacteria to protect the root tissue from sulfate reducing bacteria such as the Desulfovibrio series.  To accomplish this, the plants themselves provide a chemical life support system by moving oxygen from the air or seawater to their roots (opposite of the common upward pattern of moving nutrients to the leaves) and in this way creates a field of oxygen protection in these high organic-low oxygen peat (below the surface peat is sapropel-humus in lower oxygen conditions).  If oxygen is limited by changing tides, restriction of tidal flows, or lower warm water saturation of oxygen, these plants struggle to keep this protective root shield in place. As acidic conditions exist in these peat soils except those areas that contain bivalve shell (these soil habitat areas are also habitats that provide eelgrass a "first in" and "last out" successional pattern) – a sulfide – sulfuric balance is reached.  This is where sulfide reacts with oxygen to form sulfuric acid. 
 
Black chain and metal chemical erosion on mooring anchors show this sulfuric acid impact to metal.  This is the impact that boaters may experience when moorings are pulled or ground tackle repaired.  It is the lower portions of the chain that is black and shows metal loss from sulfuric acid release from sulfide reactions.  This oxic or oxygen containing larger appears a reddish-brown coloration (rust) while the lower portions the impact of sulfuric acid.  Two centuries or more ago it was the canal lock operators that noticed the bottoms of huge metal lock gates would disappear.  This continues to be a problem for canal locks (see A Corrosion Control Plan for Saint Lawrence Seaway Navigation Locks – Huntley and Boich).  The action of hydrogen sulfide in metal sewer pipes shows similar damage and has created a large industry that sells hydrogen sulfide gas detection systems.  Many reports are available that detail the damage from sulfide and sulfuric acid to metals but very few detail impacts to marine vegetation.  This is very important to plants in the marine zone because sulfate is so abundant, and at time leads to sulfuric acid release.  Marine plants such as Spartina patens and Spartina alterniflora, which live in salt marsh peat, can access oxygen from air.  For submerged plants, the buildup of sulfide is more dangerous or critical – as they never are completely dry.  Submerged plants are impacted by warming and lower dissolved oxygen in seawater and includes seagrass called eelgrass.   
 
It is the collapse of this protective shield that surrounds eelgrass root tissue that leads to the yellowing or black rot - the toxic impacts of hydrogen sulfide. Most of the eelgrass (or other SAV declines) can be traced to increasing sulfide concentrations and a lack of oxygen.  The same oxygen impact can be observed on peat islands those created from organics or those built by the practice of "side casting" the movement of organic composts – sapropels from channels to create dredge "spoil" islands.  This frequently happened in the cooler 1950's and 1960's although they look stable they form a compost that can be consumed by bacteria.  In heat, they can sink and any plants perish (See IMEP #76: Sulfate Metabolism in Salt Marshes, posted May 28, 2020, The Blue Crab Forum ^TM Fishing, Eeling and Oystering thread).
 
When I observed patches of dying eelgrass in Buttermilk Bay these blades often had black spots (1982) and were coated with a mucous (thought to be bacterial snottite) covering over these blades (See IMEP Parts 51-A, 51-B: The Cycle of Eelgrass and Fish Habitats 1890-1990, The Blue Crab Forum^TM, Fishing, Eeling and Oystering thread).  As the waters warmed, they naturally contained less oxygen - and with low flushing, nutrients now increased.   The primary high heat nitrogen compound is ammonia.  Algal blooms and bacterial breakdown on the bottom would trigger chemical reactions that would doom eelgrass - a lower oxygen level in water (now warm) limits the ability to move oxygen to its roots, any bacterial growth on the leaves made accessing what little oxygen was left more difficult, the plant was under chemical respiratory stress, its protective root shields collapsing and hydrogen sulfide, a toxin, now increased.  Sulfate reducing bacteria fought a "war" to dominate the reduction pathway of this organic humus - now turning to sapropel below the surface about 20 cm below the interface.  Not too many papers have discussed the chemistry of this bacterial war.  Most have highlighted non-climate impacts but the chemistry of climate change provides much more complete explanations that match habitat history and observations. It is a chemistry lesson that is repeated across the globe in marshes and mangroves when oxygen levels drop - the return of the sulfur cycle and rise of sulfate reducing bacteria.  I described this as a "climate change bacterial war" (See EC #7: Salt Marshes A Climate Change Bacterial Battlefield, posted September 10, 2015, The Blue Crab Forum^TM Environment Conservation thread).
 
"The Seafood Killing Fields and the Rise of Sapropel"
 
Of all the reports that John C. Hammond had, one of his most favorite was the Oyster Pond River study conducted by David A. Gates and Hebert Pettengill in 1970 "Some Aspects of the Estuarine Ecosystem of Oyster Pond Chatham Massachusetts." It is here the concept of long-term habitat history was brought into plain view by Mr. Hammond - the dredging project and exposing "old bottoms." His research into energy and temperature fit my perspective as well. My father Raymond J. Visel was a weather watcher of the 1960's long before current news media made it into news broadcasts. He had a Cape Cod weather station anemometer for wind and barometer for pressure. By the time I was in grade school, I was very familiar with storms called N'oreasters and a receding shoreline under attack from them.  After strong storms segments of Hammonasset Beach wore torn away often large sections of the beach in the middle of winter.
 
But here on Cape Cod, Mr. Hammond had come up with a "primer" for weather and fish as it related to the energy of storms and the impacts of warm or cold air. Here according to Mr. Hammond was the real fish story one of many periods of habitat change that reversed over the centuries and the record book was the bottom history uncovered by dredging.  Long a facet of terrestrial soil study of buried "horizons" and soil types digging into the ground to see the soil ages of times long ago. That was in fact what dredging projects could also do.  The concept of something similar in the marine environment the history of bottoms shaped and changed by energy was something I had seen happen to beaches but not the submerged bottom that was, for the most part, out of my view. 
 
Mr. Hammond helped frame my research into the past" a habitat history" for many close to shore seafood species. My employment in association with the Cooperative Extension Service first started in 1966 with 4-H, a component of the Land Grant Acts of 1914 with agricultural study of demonstration farms.  A half-century later 4-H was a youth program and I had a pony and raised some chickens. From then, I worked for three land grant universities, University of Connecticut, University of Massachusetts and University of Rhode Island. Although my employment was in the marine areas, one could not help hearing the message of getting your soil tested for pH or how soils high in organic matter were good for growth but needed proper "field drainage" to allow oxygen to penetrate the soil "pores." 
 
It was Mr. Hammond who helped with similar agricultural concepts in marine habitats, I was to learn in time that he was very knowledgeable in agriculture science as well.  Early soil researchers dug test pits (now commonly referred to cores) to see different horizons or layers over long periods of geologic time.  The melting of glaciers 10,000 year ago had scraped most of the previous organic matter away (Connecticut's climate was once tropical and hosts a Dinosaur State Park in Rocky Hill Connecticut) and when they melted left soils poor in organic matter.  This is the "culture media" so to speak to support bacteria that plants need to access essential plant nutrients such as nitrogen into its root tissue.
 
Connecticut's soil is often described as "shallow" "thin" or "impoverished" all terms that in some measure reflect low organic matter content – which meant in general poor plant growth and for Connecticut farmers low productivity and poor crops.  In several areas the planting of broom corn had depleted carbon so badly that little vegetation could grow without carbon replenishment.
 
The organic matter or "humus" determined those soils good for agriculture – sands and minerals devoid of organic matter supported minimal plant growth, but could be made "serviceable" by the introduction of organic matter and carbon into it – such as composts or manure.
 
To dig down into the soil the dark black humus layer, there remains dead plants that over thousands of years of bacterial decomposition had left a layer of organic matter.  The surface twigs, stems, and leaf fragments, below a humus partially decomposed material with some plant tissue remains and below that well decomposed with little direct plant remains that resemble plant tissue.  Chemical "signatures" exist such as tannin as a measure of oak leaf matter could remain for centuries.   Tougher plant compounds took longer to break down and wood cellulose could take decades and sometimes hundreds of years in low oxygen habitats.  That is the habitat history of bogs, and salt marshes – but most noticeable in salt ponds, areas that obtained plant material from land but shared tides with the sea.  Here are some of the most noticeable deposits of organic matter undergoing bacterial reduction a marine compost, that covert sulfate to sulfides and sulfuric acid.  Here, the fall oak leaves turned black and slowly rotted leaving the stems behind that Cape Cod shellfishers called "oatmeal."
 
Having some experience in agriculture and growing up along the shore provided an experience of examining this marine to terrestrial habitat process – the home is which I lived in Madison, CT.  At most, soils had 5 to 8 inches of dark top soil our backyard (a hollow) as compared to neighbors' properties, we had three feet.  In some backyard excavations below this layer (which made our garden extremely productive) was beach sand, and mussel shells.  Our yard at one point was likely a tide pool that on occasion shells were swept into this depression.  We were now 600 feet from mussel shells and the active beach front, but at one point subject to storms long ago.  I recall that the mussel shells were remarkably preserved, it took little effort to see what they were or that over time, organic matter had washed in our blown into this hallow over them which explained the depth of organic matter that now supported grass and trees.  Habitats had changed from what it was once to what it was presently.
 
I think that is why many years later I appreciated the habitat history of native American shell middens of Maine and Harold Castner's account which includes a great habitat history example of past climate conditions (See A Historic Trilogy by Harold W. Castner 1950).  In this account Castner describes immense oyster shell layers separated by several inches of vegetable mould.  The vegetable mould Castner describes is layers of decayed plant (both terrestrial and marine) indicating perhaps severe heat and low oxygen conditions.  This would allow for slower composting processes and the buildup of organic deposit along the banks of Maine's Damariscotta River.  As Cape Cod was absent large tidal rivers a different habitat history existed – in large "salt" ponds.
 
As sea levels rise as temperatures warmed after the ice age (and some researchers felt the shoreline themselves were sinking), large blocks of ice formed depression in melt waters – these on Cape Cod called Kettle Ponds largely fresh deep and isolated from tides but those near the shore flooded and reconnected to the sea, they become known as the name describes "salt ponds."  Salt ponds once connected to the sea new would have two habitat histories, one terrestrial and one marine, influenced by rains and plants and another from storms and the chemistry of the sea itself – salt water.  It is here over thousands of years climate would leave a measurable footprint in the plant material decomposing in it, a chemical signature that recorded terrestrial and marine events of long ago, we know today as climate change. 
 
To the fishers that later harvested seafood these climate changes would be called cycles but to ecologists as the battle between oxygen and sulfur as terms anoxic or aerobic organisms that needed oxygen and those who did not.  As an oxygen requiring life form we have come squarely down to favor those life forms that need oxygen as well, life forms in fact we call seafood – we value them and need them to survive.  Changes in seafood associated with climate change is a current media concern one that certainly reflects a bias for the return of sulfur which ruled the earth habitats long before oxygen.  The sulfur cycle is to be feared (the reason for climate change concerns) but is under represented in the marine habitat literature although its former dominance is in every cup of seawater today the sulfur–oxygen compounds we call sulfate.  Sulfate dissolved into seawater when the sulfur cycle was once in geologic time dominate, remains as a constant reminder of sulfate requiring organisms (bacteria) that access oxygen attached to sulfur instead of elemental oxygen.
 
The salt pond habitat histories provide a rare view into past periods when oxygen is short, tidally restricted or in heat when oxygen is less "saturated" in shallow waters.  These histories often reflect the type of organic plant tissue in them.  The difference in habitat quality is in a large way the difference in bacteria, oxygen requiting bacteria that quickly consume plant matter (such as those on land) and sulfate requiring bacteria who are far less efficient who take a long time to digest organic matter.  The difference over time has left a sapropel "record book" that today prevent themselves as layers in core studies.  That is why Mr. Hammond could see, by examining the Oyster Pond River, dredge spoils (they are called dredged material today, T. Visel).  He could see different layers as detailed in Appendix #4.
 
The layers of sapropel peat can be described as the humic/fibric, the layer of limited oxygen availability especially in heat, sapric, and the deepest layer, the presence of methogens that do not need any oxygen at all.  It is the sapric layer that smells of sulfur and contains the deadly Vibrio bacterial series now linked to fish disease worldwide (in our area linked to Vibrio beneckea lobster shell disease and Vibrio anguillarum the winter flounder fin rot).
 
 
Salt Ponds and Geologic Time
 
It is the Cape Cod kettle ponds now connected to the sea that provide a glimpse of habitats long ago. The remains of once a large piece of ice pressed and covered in the retreat of the glaciers had left a void in the landscape, which now filled with water but if close to the sea a possible connection, a "salt" pond. The bottom of these kettle ponds, the glacial till, the outwash of melting glaciers that covered gravel and sand, and in time over the till organic matter from energy plant life that found warmer temperatures suitable for growth. The bottoms of salt ponds therefore hold a geological time capsule of pollen grains, chemical fractions of trees and bark (lignin) as well as plankton and seaweeds swept into or that had died and sank into the ooze to be digested by bacteria over thousands of years, the sulfidic waters of oxygen poor regions with slow bacterial digestion of wood and plant matter. In time, a black jelly-like deposit that had soil compost qualities and, of course, sapropel could form.
 
One of the features of this bacterial decay (often termed benthic flux in the current literature) is that it is both the remains of terrestrial and marine plants. Leaves, especially, can fall into salt ponds and over time form an organic rich compost, one that New England farmers once harvested, termed mussel mud or just marine mud to spread on hay fields to increase oxic-requiring bacterial actions.  Although the term benthic flux is frequently used in the literature about coastal habitats, it rarely describes the role of bacteria that live in this marine compost. You cannot harvest benthic flux, but farmers bought and sold mussel mud by the cartloads. They noticed two things that came with mussel mud, a strong sulfur smell and sulfuric acid once exposed to air – oxygen (See E/C #1, posted September 29, 2014, The Blue Crab Forum^TM, Environmental Conservation thread).  This is a quote from the Connecticut Board of Agriculture in 1879 from M.J. Stevens of Essex, Connecticut:
 
"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.
 
But farmers knew to harvest the surface deposits, those that could get oxygen and support oxygen bacterial strains purged sulfuric acids in deep layers.  They often left those to overwinter before spreading on salt hay fields to restore thick grass growth.  In the 1900's, it was learned that bacteria were responsible for these acid differences.  The aspect of marine composting and the sulfide generation from sulfate metabolism is often overlooked as a natural process today - my view, Tim Visel.
 

 

Appendix #1

 

US Fish Commission – The Scallop Fishery 1887- GPO -1932 – The Dovekie Case of November 1932- A Climate Extinction Event

 

The immense numbers of small scallop seed have references in the shellfish literature as food for waterfowl. In an 1887 report on The Scallop fishery (US Fish Commission) on page 574 notes birds feeding on them:
 
"This multitude of Scallops," says a recent writer, "attracts to the waters of Peconic Bay, thousands of waterfowl.  Black ducks, geese, loons, and the common non-edible ducks, such as roots, old squaws, and whistlers, are in immense numbers while the gulls fairly whiten the sand bars when receding tide leaves the sand bare."
 
It is thought that an immense set of bay scallops occurred and is mentioned in the bay scallop literature one year later in 1933 (Nelson Marshall). A tremendous storm hit central and eastern Connecticut on November 19 and 20, 1932 (Ben Rathbun).  B.F. Rathbun of Noank (1997) and most likely was a hurricane but because the hurricane season ended November 1^st classified a gale. This storm was said to be more damaging because little warning was given shore residents. (Rathbun, 1997).  This storm is reported to have blown hundreds of Dovekie inland away from shore forage where they died.  I am told that the Dovekie has yet to return from these pre-1931 numbers.
 
Murphy and Vogt, The Dovekie Influx of 1932 – Vol. 1, 1933 pg. 325
The Dovekie Influx of 1932 by Robert Cushman Murphy and William Vogt.
 
"During November and December of 1932, an influx of Dovekies on a scale apparently unprecedented within the historic period, took place along the coast of north American, from the Canadian provinces to Florida and Cuba.  In response to a request by the Editor of 'The Auk' published in the January, 1933 issue, there has been received at the American Museum of Natural History, a mass of records and other observations, which we herewith present in summary.  It is impracticable to name all of the several hundred contributors who have assisted in this inquiry, but to each of them we take this opportunity of expressing our own appreciation as well as that of 'The Auk' and its readers."
 
Hundreds of Dovekie were blown inshore and died, stranded from its normal diet.  It is important to note that rapid species declines can be connected to natural events or storms.  These events are often found in historical reports, such as the above report.  What is far more difficult to ascertain are long-term climate extinction events – these can vary from a few tens of years to hundreds if not thousands of years.  For example, the oyster shell heaps of the Maine Damariscotta River described by Castner (1950), who mentions three distinct "layers" of oyster shell separated by plant material molds (organic layers).  It is important to note that the 1950s and 1960s Maine's colder waters had ceased the oyster Crassostrea virginica's ability to spawn.  Maine shellfish researchers had introduced the European flat oyster Ostrea edulis, which spawned at much cooler seawater temperatures.  Once could surmise that the vast deposits of oysters had happened during a much warmer Maine climate period.  We might be able to compare salt marsh cores to see a bacterial climate response as well.

 

Appendix #2

 

A Long Term Extinction Event of the Eastern Oyster Crassostrea virginica as Reported in Maine

 

A Historic Trilogy by Harold W. Castner

The Prehistoric Oyster Shell Heaps of the Damariscotta River

 
An excerpt of an account of Ancient Oysters in the Damariscotta River in Maine.  A 1950 account reproduced from a reprinted Damariscotta History Society bulletin.  A Historic Trilogy by Harold Castner – reprinted by the Damariscotta Historical Society – introduction Richard B. Day printed by the Boothbay Register.
 
In 1950 Harold Castner wrote several environmental fisheries histories for the Damariscotta River and a village he called Pemaquid in mid coast Maine.  I am sure he did not realize at the time that he would be one of the first environmental historians to portray coastal shellfish history (ecology) as a continuum of events far before European settlement.  He looked to those who lived along the coast before his time to write and help explain his favorite topic, history.
 
In this account he describes a healthy oyster population in Oyster Creek 1895 and "novelty oyster suppers" at the Damariscotta Baptist Church and a dredging project in 1900-1901 to Cottrells Wharf when some very large oyster shells were dredged up in the Damariscotta River.  (A more detailed write up of his accounts found in IMEP #3 Did Native Americans Leaves Us a Habitat History Lesson for Climate Change?  December 2013 – The Blue Crab Forum™ Fishing, Eeling and Oystering posted February 11, 2014).
 
A segment of his description is reprinted below but a more recent work – "Boom and Bust" on the River, The Story of the Damariscotta Oyster Shell Heaps – Archaeology of Eastern North America (1986) provides evidence of habitat species reversals – the presence of clam middens over those of oysters (from a series of accounts The Davistown Museum) changes of abundance such as above indicate a changing population that could signify a different climate.  Investigations of shell middens should yield further evidence of such cycles in coastal resource abundance.
 
An excerpt of an account of Ancient Oysters in the Damariscotta River in Maine is from a 1950 account reproduced from a reprinted Damariscotta History Society bulletin.
 
"Just previous to the Civil War, Professor Chadbourne of Bowdoin College, made a thorough study of the deposits, and established for all time, conclusive proof that these shells had been left there as a result of ancient feasts, and at a time so far in the past, he dared not attempt computation.  He found many individual piles of shells ten or fifteen feet in diameter and several feet deep.  Beneath this, the soil was made up of a alluvial deposit of sand, gravel and rocks, resembling the land adjacent to the deposits.  There were numerous bones of animals, birds and beavers, and even a sturgeon's plate.  A dark line ran through the bottom of the great mounds, showing the possibility of vegetable mould, formed during temporary abandonment of the place.  Shells under this layer were decomposed, or turned to lime, as if acted upon by fire.  He obtained shells of other types than the oyster and found some clam, quahog, and several kinds.
 
Despite the loss of hundreds of tons of shells by erosion and commercial uses, a great volume still stands exposed to view.  Scientific investigation revealed that there were three distinct periods of construction of these heaps.  In each case there was a period of abandonment, during which time a thick layer of vegetable mould accumulated over the shells.  The lowest layer of shells extended over about one eighth of the present known area.  This layer was about three feet thick, and at the base, many large tree trunks were found which had decayed to powder, leaving conical hollows around which the shells were packed.  Directly above this layer was a strata of mould which was some five inches thick.  It has been quite accurately determined that it takes about one hundred years to accumulate an inch of mould.  We can, therefore fix the period of this first abandonment at about five hundred years.
 
The second layer of shells was larger and more extensive.  This was about six-feet thick and covered by mould to the thickness of about three inches, or, let us say, an interval of three hundred years of the second abandonment.  In this second strata of mould were found trunks of large trees, which were of unknown species in this climate.  They were two or three feet in diameter and had grown up entirely over this second strata of shells.  These trunks were better preserved than those of the first strata, but although they held their form, they easily crumbled in his hands.
 
The third strata of shells had a layer of about three inches of mould over it.  An intimate study of this top layer of mould caused scientists to agree that it was about three hundred years ago when the last deposits were made, or at the time of the Wawenock Settlement, at this place of abundant food supply."
 

Appendix #3

 

Invisible Engines of The Salt Marsh"

Could Salt Marsh Peat Coves Record Changes in Bacterial Species as They Relate to Climate?

 

Center for Coastal and Watershed Systems,

Yale School of Forestry and Environmental Studies

Connecticut Sea Grant

Tidewater Institute

 
 
"What makes tidal wetlands so valuable, and among the most productive ecosystems on the planet?  The answer is complex, but at least one of the wonders of a healthy salt marsh is its ability to produce abundant vegetation, which in turn fuels multiple life cycles throughout the salt marsh ecosystem, and beyond.  While plants are the major source of organic matter – and food – in the marsh, few other organisms can eat it as is.  The process of converting dead plant material into "food" or energy for other organisms is the invisible engine of marsh productivity.
 
This is accomplished through complex chemical processes with the help of invisible organisms – billions of them.  Bacteria are the real workhorses of the productive marsh ecosystem, especially those working below ground – without sun, underwater, and in most cases, even without air.  These are tough working conditions.
 
If you think about it, the green plants that make up our familiar tidal wetlands occupy just the surface of the marsh.  You need only observe tidal creeks at low tide to see how much of the marsh is made up of that dark, wet "soil" below.  Closer observations reveal the makeup of this soil to be full of broken up plant material, or peat.  It is also quite saturated with water, even at low tide, which means all but a thin layer at the marsh's surface is absent of oxygen, or anoxic.
 
The cycling of nutrients in wetlands is different than in forests or in the ocean.  More nutrients are tied up in sediments and peat in wetlands, and there are seasonal variations in the amount of nutrients that a wetland holds onto, or releases to the benefit of other ecosystems (such as the near shore ocean).  And wetlands are frequently linked to upstream or upland ecosystems through complex chemical processes and exchanges, making an estuary's watershed an important part of a tidal wetland's health."
 

Appendix #4

 

From the Collection of John C. Hammond
 Some aspects of the Estuarine Ecosystem of Oyster Pond,
 Chatham, Massachusetts 1971
 
 with special emphasis on The Quahog (Venus mercenaria)
 
 The Soft-Shelled Clam (Mya arenaria) and
 The Scallop (Pecten irradians)
 By
 David A. Gates, M.S., Biologist
 and
 Herbert F. Pettengill, M.A.T., Chemist
  
 The Cultivation of Marine Soils
 
 Timothy C. Visel, The Sound School,
 Former UMASS Cooperative Extension Service Agent, Barnstable Cape Cod 1981 -1983
 February 17, 2017
 
 The Oyster Pond study was one of Mr. Hammond's favorites when it came to the area of previous bottoms, the impact of temperature and energy upon shellfish habitats and the process of eelgrass succession. It was this dredging operation that Mr. Hammond described the most that the dredging company broke into a previous layer of organic matter humus mud. This "humus" according to Mr. Hammond, smelled so bad the dredging operation was stopped – what he termed "humus" was most likely Sapropel, sealed from oxygen by the newer bottom; the result of sulfur reducing bacteria had made the common reported rotten egg smell of this "older bottom.".

 Mr. Hammond stated that as the smell increased, from the disposal area (apparently a beach) neighbors objected to this substance now thought to be "Sapropel," the result of the sulfur cycle bacterial processes pumped on the shore of Ebb Tide Motel. (It was not something that would be a pleasant beach experience for summer visitors.) The smell of sulfur was very strong and the dredging halted for need of a substitute disposal area.

 From what I recall, a layer of sand had caused navigation (perhaps a flood pressure sand wave) had covered the previous bottom most likely after a storm.  Such inlets are prone to have sand waves offshore (sand bars) move into them following storm events.  Therefore, the concept of a "habitat history," and mention of a "bar" is on page 8 of the report. It is thought the dredge operation on "black sands" moved into a blue-black Sapropel.  Black sand does smell like a slight matchstick sulfur smell; it is Sapropel that sulfide smell that can cause eyes to water and people to cough- sulfides are so strong (pg. 12). Apparently, the sand wave made it almost to the pond itself and dredging set out to a certain depth (contractual no doubt) broke through the newer sand and started to pump older sapropel (black mayonnaise) buried below.  This substance, once re-exposed to sea water, creates sulfuric acid wash and the sulfur "dead line" observed on mooring chains to mushroom anchors; it is sulfuric acid that dissolves steel and iron in seawater – it is also deadly to sea life.  Sapropel contains few living forms and the acid conditions quickly kill shellfish spat.  On page 21, note the comment "layer of sand covering a mud base."  This is the marine humus that Mr. Hammond mentioned so many times. (He also felt this should be studied as part of a marine soil research effort.)

 Ice on salt ponds causes sulfides to rise as a "winter kill" from Sapropel, many scallops perished this way in cold winters (pg. 21), leaving the dead shells behind (Winter kill in salt ponds (sulfide events) still happen today on the Cape, warnings are still issued.).

 The sulfur cycle of sapropel is mentioned on page 40 including the rotten egg sulfur smell most likely from Sapropel once exposed to air.
 Bacterial concerns are mentioned on pages 76 to 77, but many Vibrio infections were perhaps misdiagnosed as E. coli – then – and on page 84 "the eelgrass problems" now linked as a reservoir for vibrio bacteria. Vibrio bacteria outbreaks happen in heat such as the oyster Vibrio cholera outbreaks in the 1920's in Southern New England.  A rather infamous cholera outbreak (which is a Vibrio) in New York led to the establishment of the National Shellfish Sanitation Program.

 It is the warm temperatures (shallow water heat) that allows vibrio bacteria to bleed up to the surface and then dominate the bacterial spectrum.  Because eelgrass stabilizes and then traps (builds) organic matter, it provides a growth media for vibrio to populate below this eelgrass peat.  Mr. Hammond used this study to illustrate the eelgrass aggressive habitat successive attributes that so damaged shellfish habitats even for bay scallops; he did not feel the eelgrass strain in Oyster Pond was in fact, native – it was so damaging over time- first in after a break once then years later thick mats of root tissue "peat"- the "eelgrass problem" (pg. 94, killing the habitat by simply covering up clam and oyster beds).

Marine Soils and Plant Succession

 He kept a binder of eelgrass blade press-mounts on old heavy biological paper – like mounts for botanical collections of seaweed from the last century.  He had blade samples from Chatham eelgrass plants and some from overseas. He would repeat his concern that "it did not belong here" because it was so deadly (over time) to Quahogs

 He said to me many times, "This eelgrass is like a visitor to your home, stays too long and then kicks you out of your own house." (Habitat successive attributes of a farm field going to forest is the example he often used.)
 He did not like eelgrass (at least this strain) and from what we know today it is a likely North Sea strain as Mr. Hammond suggested long ago came over here in the first ships as a cushioning material packing for green crabs or put into oyster barrels to cushion them for ocean transit.
 

 There is much habitat information in this report, pH, salinity and more information is coming in (mostly from overseas Sapropel research) that eelgrass meadows from "Vibrio pools" beneath them that include, vibrio (sp.) that impact the shellfish industry- vibrio (sp.) that cause lobster shell disease, Vibrio of the flesh (fin)rot of Winter Flounder and even Vibrio chlorae (Cholera) that devastated the Long Island Sound Oyster industry here a century ago, all below eelgrass and in southern water seagrasses of various species. In high heat, eelgrass peat becomes deadly to fish and shellfish and even to us – blue crabbers in more southern waters have been dying from Vibrio infections in warm oxygen depleted waters.

 This report provides a snapshot of Oyster Pond as the colder NAO weather pattern began to moderate (1970).  What Mr. Hammond called the "New England Oscillation" is known today as the Northeast Atlantic Oscillation or the NAO. The 1950s and 1960s allowed the outbreak of the polar vortex cold Canadian air to sink deep into the middle of the United States; these cold air outbreaks energize the low pressure systems and strong storms drove sand deep into the estuaries – a moving sand bar or sand wave that moves with this increase of energy.

 He had watched some of the project, looking at the shell remains of previous sets – softshell clams, quahogs and bay scallops.  The long buried soils of sand and organic matter gave a history of previous sets according to Mr. Hammond from energy soil cultivation – much from even the direction of wind (In his notebook, he kept records of nor'easter's, the duration, velocity and direction.  He explained that different sides could get a set, or from energy in tidal action around bend themselves. The 1950's and 1960's were cold and storm filled – this period is largely attributed to a negative NAO. 
 In times of a positive NAO, the 1880-1920 period Mr. Hammond mentioned, many times it was hot and few storms.  The composting of sapropel produced ammonia, which caused the brown tides of the 1890s and the sulfide black water fish kills. The 1950s and 1960s waters were cooler and contained more oxygen; the composting of humus produced nitrate, which feeds algal strains that bay scallops and quahogs needed. Coastal processes changed as well. Inlets tended to "seal up" and needed to be opened to keep herring (alewife) runs in operation. The 1880-1920 was warm few storms and these storms, "weak."  Chatham became famous for oysters and soft-shells in the 1880-1920 period; in the 1950s-1960s in the negative NAO, it was the time of bay scallop and quahogs.

 That was Mr. Hammond's habitat history lesson: The Oyster Pond Dredge study was his textbook for that lesson.

 Tim Visel, February 2017, The Sound School