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The Cycle of Eelgrass and Fish Habitats – 1890-1990
IMEP #51 A - Habitat Information for Fishers and Fishery Area Managers Understanding Science Through History
(IMEP History Newsletters can be found indexed by date – Title on the BlueCrab.info™ website: Fishing, Eeling and Oystering thread)
The Sound School ISSP – Capstone Series
Can Eelgrass Save the Planet?
Tim Visel, Coordinator, The Sound School
May 2015

Note – Part one of two parts

This paper is divided into two sections and should be read as a combined report. The cycle of eelgrass is represented by dozens of reports and reviews of historical manuscripts. It introduces a broad concept of marine habitat succession governed by natural forces largely beyond our control.

The cycle of eelgrass is not unlike the habitat succession process of forest soils after a forest fire. Only in the estuarine soils is eelgrass successive over much longer periods of time. Many eelgrass meadows take decades to form and often transitioned those habitats that preceded them. As in a forest fire, such habitats can be destroyed in a single “energy event” called hurricanes winter or cyclones called Nor’easters.

The habitat successional attributes eelgrass can be highly specific and most noticeable in shallow, poorly flushed bays and coves. Here the cycle of eelgrass is much more cyclic and condensed as energy drops and temperature increases. Eelgrass in this case can increase eutrophication – by collecting organics, warming water and slowing tidal flows.

Eelgrass has a complex habitat history – at times providing very good “habitat services,” while at others becoming deadly.

I respond to all comments at tim.visel@new-haven.k12.ct.us.

Students interested in researching a Capstone Project should contact their ASTE advisor. FFA/SAE experimental research guidelines are available from the Aquaculture office.

There has been a tremendous interest in eelgrass as it relates to several estuarine habitat species including blue crabs. Over long periods of time the habitat services from eelgrass however are very complex, related to soil chemistry, temperature and energy levels. Before any connections can be made to blue crab Megalops survival in eelgrass we need to look at those shallow habitats over time. Several researchers have linked the decline of eelgrass populations to fish and shellfish declines and associated declines in eelgrass meadows with negative human coastal activities. One of the most mentioned activity is called bottom or sediment disturbance. The research question is if bottom disturbance has any negative influence upon eelgrass over long periods of time. Does eelgrass along our coast have a habitat cycle and what impacts could that have upon shellfish, finfish and lobster or the blue crab? It may be that eelgrass much as terrestrial grasses are an indicator of habitat change not stability. Other reports have promoted the concept of eelgrass as a stable high quality habitat, over time that concept requires definition.

When examining the historical fisheries literature, the habitat cycle of eelgrass appears to benefit from periodic energy events (storms). Over time eelgrass habitats succeed – they tend to build up and trap organic matter raising sulfide levels so high it damages the root systems. This feature also helps describe its pattern of seed dispersal which is also assisted by energy (storms) in spreading portions of plants with viable root tissue over wide areas. It also helps explain why eelgrass leaves have very high silicon levels (resists rotting) in at times very acidic habitats. These life history conditions relating to eelgrass have been mentioned in different parts of the United States and overseas. The ability of eelgrass to bind organic matter which in high heat suffers from periodic die offs is now related to putrification of the same organic matter. Did the scientific community capture all the discussions about the habitat characteristics pertaining to eelgrass? A century long look at eelgrass shows that regulatory agencies, shellfish farmers and fishers all had very different view points regarding eelgrass . (Appendix #1). Although eelgrass can have positive habitat functions, these change as habitats change responding to many natural conditions.

Over time, eelgrass habitat services appear to change dramatically in the historical fisheries literature. In a recent Boston Globe article titled, “Eelgrass Could Save the Planet” – and referenced its ability to hold organic matter as positive attribute as to lock up or sequester carbon in organics held by eelgrass. This habitat feature has a price – in high heat it could under the correct oxygen limiting conditions help the return of the toxic sulfur cycle which once ruled habitats before oxygen. We have a bias to follow the oxygen (because we require it) rather than the increase of sulfur because it is so deadly. That is why there was so much excitement when deep under sea vents were publicized – the “black smokers” under hot and extreme sulfur conditions some “life” seemed to thrive in them.

The Cycle of Eelgrass – Shellfish Habitats

The cycle of eelgrass in northern waters may be an indicator of habitat change, not stability. A long term view is necessary to capture the habitat role and services of eelgrass in our region especially for shellfish.

The decline in eelgrass populations followed a relatively “hot” period with little storm activity. In studies of Great Bay, Long Island, New York, the increase and closure of tidal inlets water exchange was linked to hard shell clam production changes (Mackenzie NOAA). In colder times increased energy tended to increase inlet openings (and marine soil cultivation) producing more hard clams while periods of neat, inlets tend to heal reducing tidal exchanges and clam harvests (Currituck Sound in North Carolina has a similar habitat history (see Megalops Report #2 2015). When the Great South Bay inlet exchange was increased hard shell clam production also increased (turns cooler) when it was restricted or smaller it was warmer and hard shell clam production then over time declined. It may be that the hard shell clam and eelgrass cycles overlap, after a cool energy rich climate period, (many storms) hard shell clams enjoy a habitat advantage – sets can be intense and widespread into renewed soils as eelgrass needs a ready seed pool nearby. Eventually hard clams became established and subject to a growing fishery as catch/landings now increase. Patches of eelgrass become established among hard shell clam habitats and as energy lessens and temperatures increase eelgrass meadows become dominant. In time this ends the hard clam habitats.

In a period of warming (less energy) organic deposits become trapped in areas of low flows – this is the transition of firm or hard bottoms to soft muck ones that so many winter flounder fishers experienced in the 1980s and 1990s here in Connecticut. In warming waters organics collected in eelgrass meadows as they now begin to rise over time leaving the previous habitat conditions now buried under a layer of soft organics. In time and in continued heat with little storm activity these deposits become Sapropelic and sulfide rich. A unique feature allows eelgrass to hang on longer in these oxygen depleted sulfate rich soils. It has the ability to move oxygen directly to its roots, resisting sulfide tissue necrosis or root weakening. As this continues the sulfide levels reach levels even those that harm eelgrass causing to roots to die or break. Weakened plants in monocultures are naturally more susceptible to disease and eelgrass habitat histories near them as well as other SAV species. In high heat low oxygen conditions organic deposits can shed ammonia as sulfide levels climb. At the end the eelgrass meadows rots away leaving isolated patches of soft exposed organic deposits. A rising sea level has often left a habitat history of habitat type reversals in estuarine coves. Often in coves and bays estuarine cores contain layers of mixed sand/gravel “vegetable mold” or a black organic layer is sandwiched at time between sandy layers that contain bivalve shell. Several Connecticut core studies show these pronounced “layers” providing evidence of both previous temperature and energy cycles. Readers interested in this topic should review IMEP series numbers 15-A and 15-B (Blue Crab Forum ™ Fishing, eeling and oystering thread).

The affinity of eelgrass to transition shellfish habitats put it squarely in conflict with shellfishers – explaining attempts to control this habitat succession process much as agriculture did terrestrial succession. In many ways eelgrass shares many of the habitat aggressive traits of non-native plant phragmites, in fact we may have several eelgrass strains here, some brought across from the North Sea. To the hard clam fishers Quahogers on Cape Cod, it seemed as though eelgrass sought out clam habitats in which to start thick growths. Of soft shell, bay scallop or quahog fishers, it was the later that mentioned eelgrass harming hard shell clam catches the most.

Eelgrass and Bay Scallop

The case of eelgrass habitat services to the bay scallop in our waters also deserves a second look. Despite that much has been written about eelgrass and the bay scallop habitat association that also is in conflict with fisheries history, some of the best bay scallop habitat conditions occur at times in which eelgrass is destroyed by storms. Some of the largest bay scallop crops occur when eelgrass habitat coverage was in full retreat over time. Bay scallop landings decline when eelgrass expands its habitat hold. The Narragansett Bay deep water bay scallop fishery is an excellent case history – we also have an example from the Niantic Bay, River systems here in Connecticut. The 1950s and 1960s in cooler and more energy period bay scallop crops were the largest (CT DEEP harvest records).

The increase of bay scallop harvests in Niantic came as eelgrass died off, not the other way around as most would understand. Today the eelgrass blight was worldwide not just the US east coast. The died off was over – large areas eelgrass had “washed away” from fungus infections. A series of storms in the mid 1930s raked New England and the 1938 Hurricane came onshore between Bridgeport and New Haven putting its strongest winds of 115 mph east of its center squarely over the eastern CT/western RI shore- Bay scallop production surged after this storm in this same area. Any exposed soft or weak eelgrass growths very likely could not stand up against this powerful storm; Sapropel and eelgrass were just simply washed away. Some habitats would forever be altered preventing the return of eelgrass. The year 1931 is mentioned many times in texts as mentioning habitat change. According to a 2005 shellfish management plan for the Town of East Lyme, CT has this mention of eelgrass being absent during some of the best bay scallop years (1940) on page 42 of the plan some of the best bay scalloping is found in this quote:

East Lyme Shellfish Commission Management Plan - December 2005
“Bay scallops have also had variable landing records. The majority of scallops in Connecticut waters are found in the eastern half of the state, with the Niantic River having the most abundant population. The landings were quite low (under 50,000 pounds annually) until the 1930s, when the catch increased sharply (300,000 pounds were landed in 1935-36). [Readers should be aware that on “off the books” seed transplant program had started in the 1920 is (IMEP #7 January 2014 Blue Crab forum fishery eeling and oystering thread}.

Verbal histories from four long-time residents of East Lyme (Henry Avery, Olive Chendall, Paul Kumpitch, Sr., and Joseph Selden) all indicate that there have always been large quantities of shellfish in East Lyme waters, particularly in the Niantic River.

Mr. Avery, Mrs. Chendall and Mr. Kumpitch all agree that there were few scallops in the river prior to the 1930s. The scallop populations explosion occurred in the 1932 and the river was described as having been “paved with scallops from Golden Spur to the highway bridge.” The surface of the river was paved with boats collecting scallops to sell to the trucks coming in from New York and Rhode Island. The limit on scallops at that time was fifteen bushels per day per person, and there was no problem meeting the limit. Mr. Kumpitch (who was a shellfish warden in the early 1940s) spoke of accidentally sinking his boat because he had collected too many scallops. He also stated that there was not a single blade of eelgrass in the river, during this period of time and that the blight that killed it off extended up and down the Atlantic coast. Around 1940 the state planted some plugs of eelgrass in the river and the eelgrass beds grew from those plugs.”

The production of bay scallops would increase until 1955 the year that eelgrass became reestablished in the Niantic River 1955 catch 425,000 pounds or about 75,000 bushels State of Connecticut (DEEP fishery statistics M. Blake et al, July 1984). The 1955 to 1990 period was one of continuous decline. By 1974 eelgrass growths in the Niantic River grew so dense explosives were used to restore tidal circulation.

Eelgrass Habitat History in Estuaries

By the middle 1970s the policies regarding eelgrass had changed, once considered a nuisance and even a pest it was extolled for its habitat services to fish, shellfish, wild life such as birds and food for migratory waterfowl (Brant). Many times the reason for declines to eelgrass was our activities and then by habitat associations, such as declines of coastal fish and shellfish populations. I would have a personal experience with eelgrass populations in Niantic Bay, CT in the early 1980s. My previous employment on Cape Cod had also raised many questions about the habitat benefits from eelgrass but excess nitrogen was still I felt a plausible reason for its decline. (I observed eelgrass in Buttermilk Bay on Cape Cod turn black and break so I was already interested in shallow soft areas).

In July of 1984 Patricia Foley Chairman of Waterford – East Lyme wrote the University of Connecticut – Marine Advisory Service Dr. Lance Stewart head of the program where I worked. The Shellfish Commission was concerned about the decline of eelgrass as years of research by Nelson Marshall had included observations linking large populations of the bay scallop and eelgrass. This is the text of the letter and my response to an area of concern adjacent to Pine Grove on August 24th 1984 and later January 1986 which was the areas that had started the Niantic River eelgrass died off.

July 24, 1984
Dear Mr. Stewart:

There is concern among {Shellfish} Commission members about the lack of eelgrass in an area east of the water tower at Camp O’Neill where it once was plentiful.

Would you be able to take some bottom samples, looking for lime or herbicides deposited in that area? A map is enclosed with the area in question marked in red.

If I can be of further assistance, you may contact me at 26 Laurel Hill Drive, South – Niantic, CT 06357

Very truly yours,

(Mrs.) Patricia Foley, Chairman

{Tim Visel response August 24, 1984}

Dear Chairman Foley:

Your letter of July 24, has been referred to me by Dr. Stewart. Observations of eelgrass decline are not unusual, especially if circulation of sedimentation patterns change. In addition, competition from blooms of green seaweed such as sea lettuce Ulva lactuca can also limit the growth of eelgrass.

Due to the fact that Niantic Bay has such a long residence time for nutrient loading this may be an important consideration. I have enclosed a publication titled “Nutrient Enrichment of Seagrass Beds in a Rhode Island Coastal Lagoon” for your interest.

Sincerely,

Timothy C. Visel
Regional Marne Extension Specialist
University of Connecticut

At the time, I came to the conclusion that the decline of eelgrass was both a nutrient (human caused) enrichment problem and warm water related to flushing. In later years was to learn that Niantic River once had three inlets, two of which long closed by a road and railway causeway. In fact it had an interesting environmental history and as was pointed out by colleagues, that nutrient pollution is only one of the several possible explanations for the eelgrass decline including natural fluctuations in eelgrass populations themselves. By 1986 I had broadened the investigation to include the build up of organic matter on the (River) bottom (July 1986) as contributing to the “higher oxygen debts due to the increased build up of organic matter on the bottom.” In this case it was the accumulation of oak leaves (naturally acidic) as a factor in acidic conditions connected to a growing problem in winter flounder exhibiting fin rot disease (DEP Public Statement T. Visel proposed regulations regarding winter flounder July 1986 Section 26-159a- Cool

The presence of multiple inlets in the Niantic River over time had opened and then closed or healed. This allowed periodic habitat reversals from natural energy events (storms). There now appears to be a climate and energy connection to water quality and residence time for nutrients. The decline of bay scallops had nothing in common with the decline in eelgrass – in this case of this areas shellfish history in fact quite the opposite. The impact of human source nitrogen also was misleading – in fact the deposition and putrification of oak leaves was more “damaging” in shallow areas than aqueous nitrogen compounds from us. Over longer time periods little habitat association of eelgrass to bay scallop populations could be determined from meetings with local bay scallopers.

A response of January 8, 1986 contained this section.

January 8, 1986

Dear Chairman Foley:

Last year you contacted me regarding apparent declines in the eelgrass population on the west side of Niantic Bay. Since then I have learned about the devastating decline of eelgrass beds in Chesapeake Bay from Plankton blooms. It seems that nutrient pollution creates a bloom of unicellular algae that may cover eelgrass blades blocking sunlight. In addition, suspended silt particles may cling to the algae forming a “slime” or gelatinous coating on the eelgrass blade killing the plant. Lastly, the plankton blooms may be so intense so as to diminish light intensity reaching the eelgrass plants.

Sincerely yours,

Timothy C. Visel
Regional Marine Extension Specialist
Fisheries/Aquaculture – University of Connecticut

In 1987, I learned from retired Niantic Bay scallopers that eelgrass once was so dense it nearly stopped tidal action and dynamite had been set in areas in attempts to dislodge heavy growths. This was done in an effort to restore tidal circulation and to shorten nutrient residence – the time it takes for flushing. The Niantic River was more like a lagoon with an active barrier beach spit that in high energy period breaks the split allowing storms and waves to remove organic deposits and increase flushing. The last major break in this split had occurred in 1815 when the “bar” broke sending storm waves deep into this lagoon. The early natural history of the “bar” included multiple breaks requiring brush and rocks to stabilize them for rope ferries established to cross them. The causeway road across the stabilized split today is still called “Rope Ferry Road.”

Over time records indicate that the bar would break and inlet change over long periods of time. It is therefore possible that high energy colder periods would have different habitats than those in quiet hot or warmer periods.

Many shellfishers on Cape Cod mentioned similar situations and one in particular summarized this situation very well. In a letter to the editor John B. Farrington of Osterville wrote The Village Advertiser, Feb 10, 1983. In his letter to the editor titled,

“Too Much Eelgrass” he describes the end stages of a very long habitat history.

“In some of the bays (Cape Cod) the eelgrass and codium are slime and silt covered, greatly reducing the flow of nutrients to the shellfish. This silt laden mess is certainly not preferred as a setting place for shellfish as they leave the veliger stage. When the roots finally get so thick that they crowd one another out, the losers decay, and with no oxygen in the soil create gases that shellfish cannot live in.”

It is the soil itself that ends the habitat clock for eelgrass (and other SAV species) with the formation of sulfide. The sulfide is the result of bacterial action organic matter in low oxygen conditions. The Tampa Bay Estuary program technical publication 04-02215-229 (Carlson et al 1994) describes the influence of sediment sulfide on the structure of south Florida sea grass communities and this feature of sulfide formation in 1993 and 2003.

The lack of energy changing estuarine soils was first mentioned in Tampa Bay as the “Tampa Bay effect” in the 1970s. A series of causeways had reduced tidal flows (energy) and organic accumulations increased behind them. In high heat these organic deposits became Sapropelic – in the absence of oxygen (in hot weather) they shed sulfides – noticeable to blue crabbers as the smell of rotten eggs. Almost every “Jubilee event” in the fisheries literature where blue crabs walked out if the water and made for easy catching was in extreme heat, low energy just before dawn and almost always accompanied by the smell of sulfide. [See Historic Reviews of The Mobile Bay, Jubilee Events, in areas in which organic matter accumulated tended to release sulfides and ammonia in low oxygen conditions.] After 12 years of study Tampa Bay researchers concluded” that this study provide powerful albeit circumstantial evidence that high sulfide concentrations kill turtle grass.” Other researchers in the 1980s noted poor eelgrass growths in acidic soils that had high pore water sulfides. (In 1978 in a study of anoxic Long Island Sound sediment nutrient regeneration (Christopher Martens et al) researchers examined bottom cores off the Thimble Islands in Branford, CT In all cases the deeper the cove the more acidic the deposit (Limnology Oceanographer 23(4) 1978 605-617). Some of the first press releases concerning low oxygen in Long Island Sound from the University of Connecticut also mentioned bottom waters “smelled heavily of hydrogen sulfide” University of CT press release July 30, 1987.

At the end of a habitat cycle eelgrass ability to hold organic matter has the same sulfide producing impacts – compare the quote from John Farrington on Cape Cod many years ago to reports to Danish researchers Marianne Holmer of the University of Southern Denmark and Jens Borum from the University of Copenhagen in 2014. They described from their research the rings of dense eelgrass beds that died off linking the ability of eelgrass to trap organic matter to the increased presence of toxic sulfide.

Science Recorder Feb 1, 2014

“We have studied the mud that accumulates among the eelgrass plants and we can see that the mud contains a substance that is toxic to eelgrass” (Holmer and Borum).

“Eelgrass plants trap the mud. And therefore there will be a high concentrations of sulfide rich mud among the eelgrass plants. The toxin weakens the old and new eelgrass, but not the adult and strong plants. When the sulfide begins to work it starts with the oldest and thus the inner part of the populations because here in an increased release of toxic sulfide and uptake by plants due to accumulations of mud. According to the researchers, sulfide poisoning of eelgrass is a significant issue worldwide.”

Basically describing the same conditions mentioned by Mr. Farrington and Cape Cod shellfishers at the end of habitat succession eelgrass habitats themselves become toxic – “not preferred as a setting place for shellfish” nor would I add a great place for blue crab Megalops either. In high heat these organic deposits purge sulfide and at times shed enormous quantities of ammonia – both toxic substances to blue crab Megalops.

The sediment quality for eelgrass is further complicated in areas that obtain terrestrial leaf matter. Shore areas that collect leaf fall, or obtain run off containing twigs, bark, especially oak leaf residues in times of high heat and low energy become subject to bacterial reduction. In low oxygen bacteria utilize sulfate as an oxygen source – the end product being hydrogen sulfide gas – with the smell of sulfur. Paraffin (wax and some soap residues) are not completely digested by sulfate reducing bacteria they remain and form a “sticky mud” that closes off pore water exchange in the soil as it seals it from oxygen above. It is thought that any “disturbance” even the smallest amount, clam raking, oyster tonging or even the movement of clams themselves (called bioturbation) can alter the circulation in these soils.

When the seawater is cold – some deposits become so sticky or cohesive that lobsters and some shrimp (manta) can excavate them- the sides don’t collapse and resemble the fiddler crab burrows on salt marshes (which is also the end result of terrestrial organic debris and explains high aluminum/heavy metal complexing in them – also from sulfur/sulfate reducing bacteria). In hot weather salt marshes themselves will produce strong sulfur smells, and high heat organic digestion below surfaces can cause sink holes or collapses as often noted by (Nichols 1920) in describing salt marshes that collapsed during the great heat period (1880-1920 in our area). The sticky and compressed organic matter sustained the Western CT lobster fishery in the 1980s – until oxygen levels turned these organic burrows into sulfide death traps. One 1983 lobster fishing observation at the mouth of the Saugatuck River had a great catch over 100 lbs of lobsters from 30 pots set below the marine docks over organic burrows – we didn’t even need a boat! The lobsters below had so many burrows in the organic matter it looked like “Swiss cheese” according to some dive reports. The lobsters also kept the oxygen levels higher by aerating the soil much as terrestrial soil drills/aerators. In this case even the movement of quahogs (hard shell clams) create passage ways for water movement (similar to the terrestrial soil cultivation aspect) and increase soil respiration rates. This could cause a reduction in sulfide formation or at least prevent Sapropel formation below these shallow wax containing organic deposits.

Oak leaves have a natural high paraffin residue – a natural defense against dry periods on land (oak leaves often have a shinny appearance). It is this same wax that creates the sticky mud bottoms in estuaries during periods of heat and little storm activity. Bivalve shell could act as a pH buffer to these soils providing suitable habitat for eelgrass which is later buried as eelgrass traps organics. In winter oxygen levels are sufficient but in summer heat turns eelgrass meadows into natures killing fields. These eelgrass meadows are destroyed by periodic energy storms allowing the habitat cycle then to repeat.

In instances on Cape Cod after storms or dredging projects in which eelgrass meadows were cut open exposing estuarine soils below they nearly always revealed buried dead oyster or hard clam beds beneath (shells). Eelgrass evidently overwhelmed these habitats and anything that once lived in them. In review of the literature it seems hard shell clam habitats were the first to show this habitat transition. It was in those shelly areas that often contained the first signs of eelgrass plants – isolated at first but in time covered large areas. A consistent report was that eelgrass first started in the back waters calmer areas subject to less “energy” after storms.

According to shellfishers on Cape Cod eelgrass came in and suffocated bivalve populations and then grew over them. This aspect was detailed by Massachusetts state shellfish biologists on Pleasant Bay on Cape Cod. This is a section of a 1967 study of the Marine Resources of Pleasant Bay – Massachusetts Division of Marine Fisheries Monograph series (John D. Fiske et al 1967).

“The most productive quahog area is characterized by sandy mud covered with a thin silt accumulation. In one area where diver biologists found quahogs to be exceptionally thick, the bottom was covered with great numbers of empty quahog shells. These mats of empty shells were indicative of extensive mortality which occurs in this crowded population of quahogs. In many areas, especially the upper portion of the estuary, rapidly spreading eelgrass growth was noted to be taking over quahog setting and growing bottom.”

And again mentioning eelgrass forming continuous under water eelgrass meadows on pages 46-47.

“A main problem facing scallop fishermen is the rapid spread of eelgrass. While eelgrass provides anchorage and protection for juvenile scallops, in dense growth it hinders dredging (harvesting) operations and adversely affects scallop grow by retarding water circulation. The eelgrass problem, which is not unique to Pleasant Bay, has become common in practically all bay waters on the south shore of Massachusetts. Unfortunately there is no practical method of controlling eelgrass at the present time.”

This was not an isolated occurrence shellfish biologists were making similar observations from Canada to Chesapeake Bay.

Eelgrass and the Sapropelic Cycle

Sapropels are described as high organic deposits containing low amounts of oxygen and high levels of sulfides. Over a century ago, shellfish researchers such as Dr. David Belding on Cape Cod noted that eelgrass and meadows over time tended to rise by its ability to hold organics and harm shellfish beds. Organic matter then was a problem but not considered a pollutant.

In one of the first discussions of organic matter as a type of pollutant was brought forward by Dr. Donald Rhoads of Yale University in the 1970s and who also pioneered some early documentation on the impacts of bioturbation upon marine sediments in the middle 1980s.

In an article in the Long Island Sound Report from the Oceanic Society volume 3, #1 Spring 1986 issue Dr. Rhoads mentions the formation of Sapropelic mud in an article written by Dick Harris. Dr. Rhoads details the impact of organic matter reducing the oxygen levels in sediments forcing bottom feeders to be compressed into smaller areas. He mentions the Chesapeake Bay blue crab fishery “how it appeared to the going so well, great catches of blue crabs and then nothing.”

The description of habitat compression often describes a much larger blue crab Jubilee event and makes the connection to organic debris collecting on the bottoms of deeper basins – “The result… is the formation of a black/mayonnaise like material (sapropelic mud) now all too familiar on the bottom of many of our harbors at the western end of the Sound” (pg 10).

Mr. Harris continues in his article the description of this organic matter….

“He describes this black, colloidal paste in vivid terms, this goal is free of oxygen and subsequently fee of metazoans (higher invertebrates that help oxygenate sediments by burrowing).” There is so much organic material and limited amounts of oxygen, that bacteria are unable to burn it off (reduction) efficiency. The small concentrations of oxygen are consumed in the process. As the sediment become more reducing in character, sulfate reduction also takes place, producing hydrogen sulfide and methane.”

As a final suggestion Dr. Rhoads urges mapping the increase of organic debris to determine if this layer of an aerobic sediment may in fact be spreading across the bottom of the western basin of Long Island Sound (page 13) “we could map this anaerobic sedimentation on the bottom of (the) western basin and determine the extent of the sapropelic mud or the azoic (lifeless) zone.”

These habitat changes appear slowly – quick changes are more noticeable.

The dreaded oyster disease MSX appears in shallow, older populations in the same areas as black mayonnaise deposits. The Connecticut MSX outbreak has been linked to the Hammonassett River site of production oyster beds, but accumulations of black mayonnaise organic deposits started in the later 1970s. These organic deposits dominated the lower Hammonasett River estuary in the early 1980s, adjacent to a closed barrier spit inlet called the Dardenelles, which reduced flushing. Organic deposits then accumulated over previous hard “bottoms,” providing a thick eelgrass cover over them. Eelgrass habitats in shallow bays are the compost piles of estuaries.

Even the red tide organism, Gonyaulax tamarensis has been linked to shallow, warm organic deposits as potential seed or start innoculations that can spread to larger areas. This occurs during periods of habitat transitions, instability, extreme heat and very active storm filled winters. Strong storms dislodge marine composts releasing at times enormous quantities of nitrogen compounds, which like spring marine algae, can “bloom” when temperatures rise. It could take a decade of storms to reduce such “stored” nitrogen containing composts. According to some Cape Cod shellfishers, the 1938 hurricane “cleaned out the coves” transitioning once soft bottoms to firm ones (John C. Hammond, Personal conversation, 1982).

In many texts references are found to warm, soft organics (deposits) as containing buried red tide cysts (Mumford Cove, Groton, CT). These areas are often located near closed inlets or areas with long connections to the sea (poor flushing). In a review of the Abundance and Distribution of the Toxic Dinoflagellate, Gonyaulax tamarensis in Long Island estuaries (Schrey et al Estuaries Vol. 7 #48, page 472-477, December 1984) found that “high concentrations of motile cells (moving spores) primarily occurred in head water regions where fine-grained sediments are deposited and where currents and tidal flushing are small” pg. 476 and red tide distribution was not uniform within each of the four main study areas cell densities and were “generally confined to the headquarters of the estuaries, falling to undetectable levels at the mouths” (p. 475). (See Red Tide, Appendix 2)

These soft organic deposits have been linked to winter flounder fin rot disease and a vector for the blood fluke commonly called, swimmer’s or clammer’s itch (parasite schistosomes). A more recent increase in the vibrio bacterial series has also been associated with deep organic deposits in which bacteria reduction occurs. Harmful algal blooms (HAB) has a link to ammonia, while red tide algal strains to nitrate.

The process of sulfate bacterial reduction happens in areas of low energy (disturbance), nearly always shallow, warm organic deposits in poorly flushed areas. Chemical and biochemical reactions can alter sediment quality with the addition of sulfur compounds and the purging of sulfides/organic acids. Combined with basic ammonia seeps or discharges of sulfuric acids pH levels can change quickly –removing remaining oxygen during this process. Eelgrass can hold such soft organic deposits for decades releasing nitrogen and sulfur chemical compounds in storm events (heavy rains, ice scour and waves). Eelgrass can also slow tidal flows, trapping organics and enhancing high temperature organic reduction by sulfur reducing bacteria in a slow steady habitat succession process.

This is one of the reasons so much concern has been expressed about large amounts of organic matter collecting behind terrestrial dams (Conowingo Dam articles in 2014). Such organic deposits occur quickly after rain events (floods). That organic matter in sulfate limited waters (like terrestrial streams) is accumulated and then redistributed down stream in high energy events (floods). Once this huge slurry of organic matter reaches estuarine habitats areas in which sulfate is not limiting in high heat bacteria decomposes them (marine composts) in low oxygen conditions turning to sulfate for an oxygen source and this sulfides. This is the same organic matter that is trapped by eelgrass as eelgrass meadows tend to rise in elevation (deposits tend to deepen and may even transition into navigation channels). Bays and coves obtaining such tremendous quantities of organic matter (mostly ground up leaf material in New England) are naturally phone to oxygen depletion as bacteria strive to consume this large new “food supply.” Although terrestrial composting is encouraged even celebrated on land such marine composting is often deadly in the marine environment – creating at times a sulfide acidic wash (fishers may notice metal traps weakening or being eaten away) followed by hydrogen sulfide smells in summer or methane in winter. In high heat ammonia can be shed by these organic deposits in large quantities a direct toxic substances to fish and providing a “ready” nutrient to harmful algal blooms (HABS).

This process has catastrophic habitat impacts on oxygen requiring organisms, as these bacteria decomposers run out of oxygen they first look for nitrate (also a ready source of “usable” oxygen) once that is fully utilized they turn to sulfate (S04) which is non limiting (abundant) in sea water and produce deadly sulfur compounds – the cause of the oxygen/chemical habitat compression we call blue crab jubilees. This process is familiar as a greasy blue/black deposits – high in iron sulfide which gives it this appearance others may refer to it as black mayonnaise. This was the process that Dr. Rhoads was trying to explain in 1985-1986. As our temperatures increased into the 1990s, excess organic matter became Sapropel – and spread out into deeper areas in the absence of strong storms. It is the Sapropels that in time can eliminate eelgrass as sulfide levels increase. It is also formed underneath eelgrass or SAV meadows. In high and low energy these deposits shed toxic sulfides as oxygen levels go down. What was seen first as a shallow water or bay effect in the 1980s spread to cover hundreds of square miles in the 1990s with increasing heat.

Many crabbers and shellfishers have experienced the five stages of sulfide low oxygen toxicity from organic bacterial reduction.

The cycle of eelgrass does have a part in sulfide levels, the first by direct accumulation gather of organic matter and by slowing tidal flows, for oxygen requiring life hydrogen sulfide toxicity is a respiratory response – lethal in micro molar concentrations as it disrupts the bloods (hemoglobin) to ability transport oxygen – thus enhancing low oxygen impacts (Riesch et al Royal Holloway University of London – Hydrogen Sulfide – Toxic Habitats 2015). This explains why fish will move to the surface to benefit from higher oxygen levels and where bottom waters stratify (layer) in warm weather why h2S smells often originate. Hydrogen sulfide was formally described by a German-Swedish chemist C. W. Scheele in the late 1770s as “stinkerde” a variant continues today as stinker today is associated with “bad smells.” (Riesch et al 2015).

Sulfide toxicity is a factor of temperature, oxygen levels and acidity pH. There is an agreement from a variety of sources that sulfide toxicity is much more damaging on larval forms than adults H2S sulfide is soluble in water – one gram fully dissolved into 242 ml of freshwater at 20oC forming a solution about 4,000 parts per million at a pH 4.5. The strong odor of sulfide is detectable by us at levels of only 5 to 300 parts per billion. (Reef Keeping – Hydrogen sulfide and the Reef Aquarium – Farley) and is toxic to us at high concentrations at which we cannot detect – adding to its potential danger in contained air spaces. Most saltwater aquarium owners will recognize the black layers from sulfate reduction and at times the sulfide – sulfur odors during filter changes. Although most experience sulfide impacts in heat but ice can also seal off oxygen and create bottom scours – dislodging sulfide rich bottom deposits producing sulfide sulfuric acid washes lowing pH. Long cold periods have been associated with “winter kills” but we may find that such “kills” are sulfide toxicity from cold water sulfide purging.

Fish have acquired varying degrees of sulfide tolerance, eels for example can exist in these low oxygen sulfide rich environments much more than many others. However, Brown Trout its lethal concentration as which half (50 percent) perish (LC50) is only 7 parts per billion, while flatworms can tolerate much more 30,000 parts per billion sulfide or more.

The five stages of low oxygen (sulfide) death – as described by Tyson and T. H. Pearson – (additional sulfide information provided by T. Visel).

Stage 1 Low oxygen levels 2.0 to 1 mg/L – Habitat compression or the Jubilee factors on hot summer days crabs will move to cooler groundwater tide lines – fish that can will fled the area. Blue crabs may walk out of the water. Sulfide levels in shallow waters purge from bottom organic deposits. About 30 to 300 parts/per billion. Rotten egg or match stick sulfur smells reported.

Stage 2 Oxygen 1.4 to 1m/L – Any crabs or fish will flee these sediments. Winter flounder trapped may seek out sandy areas at first for ground pore water – especially on ebb tides. Soft shell clams may extend their necks – Adults blue crabs will die. Sulfide level is lethal to most larval forms as pore water fills with sulfide. 300 to 1,000 parts/ billion. Soft organic deposits when distributed may have a strong to moderate sulfur smell.

Stage 3 Oxygen less than 1mg/Liter – Fish may leave bottom and be at surface circling or jumping soft shell clams may leave the sediments entirely (hard clams also) by the thousands oysters tend to gap. This happened in Rhode Island recently when millions of soft shells popped up and then were washed shore – decomposing meats then fuels greater sulfide formation – fish trapped in these waters die within a few minutes. About 1,000 to 5,000 parts/billion.

Stage 4 Oxygen .5 mg Liter – All visible life movement ends – dead fish crabs and shellfish now evident the smell of sulfur at times can be so strong when handled. Stains of black on crab bodies, shellfish shells also can be observed –black above the sediment – Houses can be stained black from sulfide aerosols blown ashore very high 5,000 to 10,000 parts/billion.

Stage 5 -0- By tide or wind – the smell of sulfide in the air is strong – any shellfish recovered will have black stains, fish trapped on surface or carried in by tides now circle on top then perish, low or no oxygen bottom waters upwelling to the surface can kill fish by the millions – this happens to menhaden in shallows most frequently contain soft organic deposits or Sapropel (see local references to Black Mayonnaise). 10,000 parts/billion or higher these levels approach those sulfide waters found in the Black Sea but also reported levels in the Narrow River in Rhode Island. (See Gaines 1974, 1983, 1994).

Not that much has been studied about sulfide toxicity in these very shallow yet very critical shallow water habitats. Most of the important larval forms (Blue Crab Megalops) live in this tidal zone at some point and it is this shallow areas so vulnerable to excessive heat. As eelgrass meadows rise they collect solar energy in shallow waters – on very warm days they become themselves hot – in observations on the Niantic River in the 1980s – fish fled from these areas on hot August days (T. Visel observations of Niantic eelgrass meadows 1987) (Files from Niantic River, eelgrass survey). Observations in Buttermilk Bay on Cape Cod had similar conditions very warm waters and eelgrass that had turned black (T. Visel observations 1982). In a shellfish survey on Buttermilk Bay soft shell clams were dead, shells stained black and sulfur smells quite evident in the sediment (BSSA reports 1981).

Most of the scientific literature today reports on the limitations of declining amounts of oxygen – rather than the toxicology of increasing amounts of sulfur. The return of the high heat sulfur cycle would be nothing short of catastrophic to us and other oxygen requiring organisms. However in the case of eelgrass it could be argued that in the smallest of bays and coves it helps create the first dead zones (hypoxic zones) in the areas most recognized as critical to larval forms of fin and shellfish. Researchers are now beginning to mention Sapropels (black mud layers) and dead organic matter being a source of nitrogen and phosphorus. John Vare Kamp of Wesleyan University recently issued an excellent fact sheet titled Hypoxia in Long Island Sound – Facts and Comparisons (it is available from Connecticut Fund for the Environment) that mentions this process on page 4 in a report Feb 9, 2015). More information is needed pertaining to sediment quality for ammonia and sulfide toxicity (EPA 1994 Methods for Assessing the toxicity of sediment – associated contaminants with estuarine and marine Amphipods.)

With increasing temperatures and oxygen inverse solubility law it may be impossible for some areas to be hypoxia free making eelgrass meadows a case to study for sulfide generation not its ability to hold organics. The emphasis upon oxygen needs could be said our bias – without oxygen we could not survive but a host of sulfur sustaining organisms could. (See worldwide anoxic event). This would signal the return of the sulfur not the oxygen cycle. It is also the concern behind reducing sulfur in fuels that discharge high amounts of sulfur. In warmer environmental conditions deep deposits of organic matter would just by their very presence assist sulfur requiring organisms.

The return of the Sapropel/Sulfur cycle would mean oxygen requiring organisms would lose this habitat conflict – they often die and something that fishers observe in the shallows. Eelgrass it seems has developed some survival attributes itself – the ability to move oxygen into its roots for example giving it a sulfide edge. While cooler temperatures oxygen sufficient levels eelgrass performs habitat services for blue crab megalops (and many other fish and shellfish larval forms) in high temperatures it becomes natures killing fields shedding enormous quantities of sulfide so much that over time this sapropel kills the plant itself or weakens it so much it is vulnerable to disease. In the 1940s and 1950s (a cooler period for New England) historical references mentions that Widgeon grass (Ruppia) was once a dominant species. Eelgrass displaced Widgeon grass in upper estuaries and river mouths over time and many Rhode Island Salt Pond habitat histories do mention Widgeon grass not eelgrass as dominant. Tropical storms are now thought to unbalance the sulfur cycle sending vast plumes of organic debris into estuaries source of nutrients and later sulfides – this makes habitat type indexing against temperature all the more important. In hot dry periods Sapropel builds rapidly – in times of cold and frequent storms harder bay bottoms often prevail.

In a study of determining the economics benefits of habitat restoration “Sea grass and the Virginia hard shell Blue Crab Fishery” (Eric E. Anerson, 1989) {North American Journal of Fisheries Management 9-140-149 1989}. The author mentions the importance of Chesapeake Bay sea grasses to the early juvenile stages of blue crabs – especially megalops and offers the 1960s as the peak period for submerged aquatic vegetation (pg 140). (This period was during a negative NAO period – known for cooler temps and stronger more frequent storms).

What isn’t mentioned often is the habitat succession attributes of submerged aquatic vegetation themselves (see Appendix I, report of Harold J. Elser) which should be measured over longer periods of time and different climate conditions. That report was done roughly the same time period and has another and very different point of view. The 1960s had several storms and was cooler – oxygen levels were higher and organic debris and nutrients washed into Chesapeake Bay most likely caused growth of these plants from organic debris – while higher energy zones most likely benefited from marine soil cultivation low energy zones now saw firm habitats turn soft. Eelgrass benefited in southern reaches in higher energy areas while sea lettuce for example formed dense matts in the shallows capable of providing sulfides in heat and lower energy areas. This in some way explains the advance of eelgrass in northern areas in mixed or cultivated marine soils and why oyster growers noticed its ability to form on edges and channel banks after “energy events.”

In high heat this organic matter trapped by eelgrass raises toxic sulfide levels so high it can kill the plant itself. Danish researchers have documented this pattern describing them as eelgrass death/rot rings. Contrary to prevalent policies, eelgrass populations are sustained by periodic coastal energy naturally ripping out overgrown areas – redistributing built up organics and setting the conditions for the habitat succession process to begin once again. Without periodic energy eelgrass meadows overtime then to develop disease as they become shallower and “hotter” over time inducing so they make low oxygen condition conditions worse and deadly to Megalops and other oxygen based life forms. As sulfur reducing bacteria reduce this organic matter they also assist in the complexing of heavy metals (many toxic) including aluminum.

Conflicting Habitat Services –

The structural reef services to fish and food supplies to waterfowl (especially Brant) provided some of the first publicized benefits of eelgrass – at a time when the public was not concerned about tidal wetlands, dredging out salt marshes or filling them. This time period was a public policy foundation of many todays environmental groups. Tidal wetlands are extremely important to finfish and shellfish species but their “value” can change over time with climate patterns. What was good in a cold and energy filled period for winter flounder in the 1950s would turn deadly for them in the 1980s. The clean and green eelgrass does provide important habitat services to fish, birds – migratory waterfowl crustaceans such as blue crabs but such environmental habitat services are very much climate dependent. In times of cold beneficial, in times of heat - deadly. In the future the cycle of eelgrass might become one of the more significant indicator of climate patterns and help to explain the process of habitat succession in coastal environments. The cycle of eelgrass may in time resemble the role of terrestrial grasses stabilizing “forest soils” after a forest fire, and the production of sulfide or ammonia similar to smoke.

Transitioning Roles for Habitat Quality

In a review of the trends in submersed macrophyte communities of the Currituck Sound 1909-1979 (Davis et al 1983). Journal of Aquatic Plant Management vol 21, pages 83-87 mentions that over time Widgeon grass Ruppia maritima, Wild Celery Vallisneria americana or red head grass Potomogetan all varied in dominance. A greater mention (emphasis) was the change in water color and bays with forest litter over time mentions Mahogany tides – most likely those containing tannin.

The Currituck Sound reviews are some of the largest and in depth reports giving an insight into changes into circulation (inlet locks and canal) exchanges. Many such bays have periodic inlet openings and closures and on page 84 (of Davis et al 1983) contains this section,

“Between 1909-1919 a previous researcher (Bourn W. S. 1932) describes Currituck conditions which implies a “deteriorated ecosystem with low oxygen, turbid water, higher salinity than normal and a four odor.” It is the reference to bottom deposits that today sound so familiar – Davis et al continued – quoting Bourne “There was a deep layer of sludge” on the bottom which was kept in partial suspension of waves. Sludge accumulated at rates as high as 5cm per year – concluding that the turbidity was the principal cause of the demise of the submerged macrophytes.” But further examination points to an opening of the Cheseapeake Canal which delivered a surplus of organics into a system although large in area – had reduced flushing and periodic energy – inlet events linked to storms. This report gives a rare insight into long term climate (temperature, rainfall and energy) habitat reversals and the observations of specie flucuations.

Eelgrass and Bay Scallops?

In the early 1980s eelgrass was frequently promoted as providing essential habitat services to the bay scallop. Bay scallops do attach to eelgrass blades with abyssal threads but in world wide research, it appears corralline algal hydroliths enhance larval settlement of scallops species worldwide – with the isolation of chemical products that increase settlement and in some cases spawning (Diana Steller et al – Marine Ecology Series Vol 396-49-602009). What wasn’t mentioned it also provided habitat services to one of our most problem some invasive – the European green crab Carcinus maenas several scallop researchers noted the fierce predation of blade attack, stripping small bay scallops off eelgrass blades and that over time green crab/eelgrass habitat association often increased bay scallop predation not reduced it. (Canadian researchers have documented a direct eelgrass/green crab habitat association Jodi Harney CORI project 2008-11 July 2008).

Other researchers have identified fragments of chemical compounds released after coralline algal tears – such as following a storm perhaps sending chemical clues as to the location of algal locations as a potential or preferred settlement area. (Researchers today are looking at corraline red algae exudates for scallop setting). In early studies of Niantic Bay done by Mr. Nelson Marshall local Niantic River bay scallopers claimed that “red weed” thought to be Agardhiella subulata was the correct “scallop grass.” Several oral histories claim bay scallop were settings more intense after cold periods and hurricanes. Supporting these oral histories actual catch statistics for bay scallops in Connecticut shows harvests were higher in periods of cooler water and numerous hurricanes (1950s), when eelgrass was practically nonexistent. High organic matted aquatic plant deposition in rots in shallow water undergoing bacterial reduction. On clear mornings on small coves a steady stream of bubbles can been surfacing from these decaying deposits (Middle and North Coves Essex, CT).

Eelgrass (as to other grasses) hold soil and reduce tidal flows and such actions have terrible consequences in shallow estuarine habitats – if the capture of organics occurred in warming waters (and the consensus supports global warming) than the accumulation of organics in shallow heated waters would likely end most of the critical habitat (termed essential) zones that today support most coastal shellfish and finfish species. A return of the Sapropel/sulfide habitats can be highly toxic to many estuarine species. We will certainly need more information about ammonia and sulfides generated by eelgrass meadows before asking for more in “essential” nursery habitats subject to high temperatures – my view.

MARYLAND DEPARTMENT OF CHESAPEAKE BAY AFFAIRS (Appendix #1)
Manatee Project
Annapolis, Maryland May 5, 1965

STATUS OF AQUATIC WEED PROBLEMS IN TIDEWATER MARYLAND, SPRING 1965

Harold J. Elser
Fisheries Biologist

Currently, Chesapeake Bay and its tidal tributaries contain large beds of aquatic weeds, many of which are so placed they interface with recreational uses of the water, and with commercial fishing. They also have adversely affected waterfront property values. There have been weed problems for many years but never as extensive as they are today. The complaints they generate are increasing, partly because more and more people want to use the water.

The growth of all aquatic weeds is promoted by enrichment – nutrient materials, primarily nitrogen and phosphorous, which act as fertilizing agents. With the expansion of the human population and changes in agricultural techniques in the watershed, the sources of this nutrient material are constantly increasing. The chief sources are: (a) fertilizer from farmers fields, (b) effluent from sewage-disposal plants, (c) overflow and seepage from septic tanks, and (d) waste from pleasure craft (although this is probably a very minor factor). Even migrating ducks, geese, and swans contribute nutrients to the Bay.

Increasing amounts of nutrient materials result in an increasing over-all productivity of the water and this productivity eventually produces a greater population of fish, oysters, clams, etc. however, the nutrient materials must first be organized by green plants and it is this stage of the process that creates our problems.

If aquatic-weed problems are caused by excessive nutrients, it follows that the only permanent solution would be to stop the supply of these nutrients or inactivate them in some way. Any program of plant removal or destruction with chemicals can have only temporary results, because while it may be possible to eliminate certain species from an area, other species will certainly take over in a short time.

The problem plants are of two types, the large, usually rooted, plants and the microscopic, free floating organisms known as phytoplankton. In the Potomac immediately below Washington, D.C. (where an estimated 45 tons of N and P compounds enter each day), plankton grows in such abundance that the water is continuously the color of pea soup. It is not clearly understood why the nutrient materials are organized primarily by plankton in some areas and by large aquatics in others.

Extensive beds of large aquatics interfere with boating, fishing and swimming, and often provide excellent breeding areas for mosquitoes. Excessive plankton causes wildly variable amounts of oxygen in the water which often results in fish kills. Sometimes the plankton washes up on shore and rots, producing vile odors. It has also been found that certain insects, such as midges, are especially abundant in areas of plankton bloom

IMEP #51-A Appendix 2
The Cycle of Eelgrass and Fish Habitats 1890-1990 – Part 1

The Cycle of Eelgrass
Climate Change and Red Tide – The Mumford Cove, Groton, CT
Habitat Case History
Tim Visel

In 1981 I participated in a shellfish survey of Mumford Cove, Groton, CT - the site of a municipal sewage outfall and once a productive shellfishing area. The survey was arranged by Malcolm Shute of then the Connecticut Dept of Health and Edward Wong of Region 1, EPA Office in Boston. This survey was in cooperation with Dr. Sung Feng of the University of Connecticut. Rhode Island shellfish officials also participated because of previous experience in sampling soft shell clams Mya arenaria, which was reported to be in heavy concentrations along the lower cove edges.

Groton Shellfish Committee members Elmer Edwards and Ken Holloway were also interested in bacteria tests (both waters and meats) in regards to a waste water treatment plan (World War II) that was expanded in the middle 1970s. That plant was constructed during the World War II effort to support navy housing. The University of Connecticut Marine Sciences was researching nutrient levels – Drs Buck and Feng. The 1981 survey of Mumford Cove was conducted in the summer and first reports back in November 1981 (Ed Wong, EPA memorandum of November 2, 1981 to Tim Visel) included one of the results included red ride cysts were found just above a layer of oyster shell some 1.5 meters deep in some areas that according to Dr. Wong these cysts were still “viable” and biological active. He summarized that these cysts were deposited at a warmer climate recently (1981) and made reference to Narragansett Bay red tides in the 1890s – similar coves that had also shown them (locations not mentioned). We did find large quantities of soft shell clams in the lower cove adjacent to the entrance of Groton Long Point Harbor- also called Venetian Harbor. Much of the center of the cove was dominated by soft muds and thick growths of sea lettuce Ulva lactuca. Oyster populations had long since vanished.

That agreed with local Groton Shellfish Commission members as well local stories continued to exist that Mumford Cove was once an active oyster bed. Conditions I experienced then (1981) did not represent any hard bottom – edges were firm into the center channel areas which held modest eelgrass growths but the flat portion of the cove was entirely covered by dense mats of the green alga Ulva lactuca. The bottom would not support walking many areas. Commonly called sea lettuce Ulva is now thought to emit a natural biocide. The transition from Duck weed (Ruppia martina) may have had an impact on the blue crab as well. Research is now focusing upon toxic impacts of sea lettuce to blue crabs (The Search for Megalops Blue Crab series #3 July 23, 2013). Donna A. Johnson and Barbara L. Welsh of the UCONN Marine Sciences were looking at dense growths of sea lettuce for toxic impacts to Blue Crab Megalops – their research found that in low oxygen conditions (at night) these plants shed exudates that were toxic to blue crab larvae. In very low oxygen conditions in one trial (almost none) all the larvae died in 13 to 40 minutes. (Journal of Experimental Marine Biology and Ecology 1985). In semi closed systems where flushing is adequate but tidal energy low Sapropel may sustain dense growth of sea lettuce. Sea lettuce growths have now been linked to high pore sulfide levels in soils below them. In summer Sapropel/sea lettuce growths shed high levels of ammonia.

Large dense areas of soft shell clams were found in brown sandy edges near eelgrass – occasionally in dense quantities in the southern portion of the cove. Concerns were expressed by Connecticut Health Dept (Malcolm Shute) about soft shellfish harvesting but soft shell clam relays were occurring on Cape Cod and Martha’s Vineyard (State of Massachusetts Management Plan For Soft Shell Clam Resources In Moderately Contaminated Areas September 18, 1978). The Town of Edgartown Massachusetts moved nearly a half million seed clams (many stunted) with jet pumps into better growing areas. [The use of an outboard power Hanks (hydraulic) rig – (clams being moved to ensure growth in Edgartown Project” Cape Cod Times June 19th, 1977 could move 50 bushels of adult steamer clams per day – John Hammond – and source of article to Tim Visel, 1983.]

Several soft shell clam relays using a hydraulic dredge commonly called escalator dredges were able to move up to 2 seed bushels per day with Hanks Rig hydraulics (also called escalator dredges) on Martha’s Vineyard moved to clean waters they became the basis of a recreational shellfishery.

The disappearance of Widgeon grass (Ruppia maritina) was linked to an increase of sewage discharges and reduction of fresh water – primarily droughts. According to the Groton Shellfish Commission at times Ulva matts smelled (sulfur) and the Mumford Cove was a popular duck hunting area before sea lettuce appeared (Ken Holloway, personal communication). In more saline periods lower rainfalls does promote sulfate reduction producing sulfides – eelgrass being very tolerant of sulfide could naturally been displaced Ruppia and then itself by sea lettuce. That is recorded in many Rhode Island salt ponds and bays in the middle Atlantic. According to Groton Shellfish members “Duck Weed” was once prevalent in Mumford Cove and “held the ducks” (Lee 1980) also mentions similar Rhode Island salt pond habitat circumstances. If dry periods are long enough sulfides could reach levels to those toxic even to eelgrass – entering questions about habitat succession of eelgrass over time (Temperature and energy profiles).

Red Tide Cysts -

Concerns were raised by Woods Hole Oceanographic Institute about red tide dynoflagellate blooms in Perch Pond in 1979 (Falmouth MA) was G. excavata – not G. tamarensis. The Woods Hole Sea Grant project had raised concerns about cyst survival in organic sediments in poorly flushed areas. Some evidence did indicate red tide occurrence in the Poquonnock River following the regional outbreaks of the 1970s (reports of Groton shell fishermen). It was thought at the time red tide cysts lay deep in these sheltered organic deposits and hydraulics (or any storm) could re expose them to potential blooms (Dept of Environmental Quality Report – Town of Falmouth Shellfish Dept Project) (Communication to Tim Visel 1982 - Woods Hole Sea Grant Project. Red tides appeared on the Cape after the Blizzard of 1978 and summer of 1972.