CTFishTalk.com: The Cycle of Eelgrass and Fish Habitats - 1890-1990 IMEP 51B - Connecticut Saltwater Reports ( CT Saltwater Reports ) - A Community Built for Connecticut Fisherman.

BlueChip

The Cycle of Eelgrass and Fish Habitats 1890-1990
IMEP 51B – 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 – June 2015

Note –Part two 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 or winter 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.

Part 2 – Blue Crabs Shellfish and Eelgrass –

Blue Crab and Eelgrass – Many researchers from the 1950s described a positive relationship of eelgrass and other submerged vegetation types as important for the blue crab Megalops – which is correct – for the time period. The 1950s will be remembered as some of the coldest periods since the 1870s. The impact of temperature and benthic sulfide flux upon larval forms has not been usually included in eelgrass habitat services. A clean and green eelgrass in sandy soils provides both significant feeding and predator protection services. But in extreme heat these areas support huge densities of mummichogs (Fundulus heteroditus) which can tolerate high sulfide levels and feast on dead or dying blue crab Megalops. In brackish waters these species consume so many mosquito pupa they are nicknamed the “mosquito fish.” The zoea blue crab (coiled stage) looks very similar to the mosquito pupa if fact they are very hard to tell apart, eelgrass in this case may increase the predation of Megalops and star crab sizes. In high heat and less energy eelgrass habitat values decline – in respect to species we “value.” The cycle of eelgrass has both positive and at times very negative habitat “services.”

Transitioning Estuarine Habitat Services?

A few years ago SAV (Submerged Aquatic Vegetation) was championed for helping keep waters clearer. This was accomplished by presuming that the collection of silted “fines” was a good thing for estuarine habitats – similar to flocculation tanks at sewage treatment plants or behind terrestrial dams. But as any organic accumulating activity – eventually capacity is reached and you must empty the tank or dredge out the pond. Eelgrass does have the ability to slow water movements and in doing so fines and organic materials settle out faster. What is often missed is the same process in high heat turns deadly (Sapropel formation) as eelgrass grows upward trying to hold onto its organic base. This is in fact helps reduce tidal circulation in areas with inlets or small cove/bay connections to the sea. It has even been suggested that eelgrass meadows function was breakwaters and for brief periods during storms they do however very intense storms are no match for eelgrass meadows, any protection services are quickly eliminated by storm waves long quiet periods are very different and thick growths can reduce tidal flows. The oyster industry literature is often accompanied by carefully drawn sketches detailing how circulation was reduced by eelgrass and available food or oxygen for living marine resources lessened. Collins (1891) in this review of the Connecticut oyster details a habitat history for the Poquonnock River in Groton, CT.

“The Poquonock method has been moderately successful and perhaps is the best for the locality where it is employed – there are several reasons why it has not proved entirely successful, among which may be mentioned the collection of large quantities of eelgrass about the flats at the mouth of the stream causing stagnation of the water and producing such conditions that the board of health of the town has caused the bushes to be pulled up and destroyed. However, while the bushes could be kept down, the young oysters have invariably grown rapidly, probably because the bottom of the river is very muddy,” pg 477. (Notes on the oyster fishery of Connecticut by J.W. Collins – 1891 Washington GPO Bulletin of the United States Fish Commission Volume IX for 1889 pg 416-497).

Very few articles describe the negative implications of collecting organic matter in shallow easily warmed estuarine habitats. The consequences of habitat compression and failure of the southern New England winter flounder habitats is now linked to organic matter trapped in estuaries during periods of high heat/low oxygen. In this organic matter (which can accumulated over previous hard bottoms) sulfur reducing bacteria live and several associated toxic strains to the infamous flesh eating bacterial strains.

Eelgrass does have the capacity to store organics in deposits especially in meadows and as such historic literature mentions their ability to rise over time. Below the eelgrass meadows, however and removed further from oxygen containing sea water these deposits under go sulfate bacterial reduction releasing sulfide and ammonia while at the same time complexing (naturally) heavy metals in sapropels. In this case the environmental “services” can become negative. In times of extreme heat or extreme cold (ice) heavy organic loads such as flush or organics after heavy rains can trigger sulfur reduction processes.

They do in fact under these conditions become deadly and can assist anoxic events releasing hydrogen sulfide in greater and greater amounts. This aspect of eelgrass habitat history is rarely presented in current media stories about eelgrass.

Dr. David Belding who did extensive research on Cape Cod during a warm and relatively quiet period describes the fate of soft shell clam beds and eelgrass with short and often blunt statements. Belding also documents negative impacts to hard clam, shellfish slow growth, burial and for bay scallops low meat/bushel yields. Many recent reports make reference to eelgrass increasing water clarity in seawater but some of the heaviest growths of a recent cycle was during a much colder period.

Dr. Belding on the growth of soft shell clams – “Eelgrass as we have seen is fatal to a good clam bed. Many productive beds would be quickly spoiled by eelgrass if it were not for constant digging. The grass raises the surface of the bed above the normal level by bringing in silt, which smoothers the clams.”

Colder water tends to be clearer from biologically reduced plankton growths. That is quickly observed after a fall frost, a walk along the Shoreline then will be remarkably clear – colder waters – clearer waters are better for submerged plants. And the brown colors have observed by coastal observers now has a direct influence to high levels of Tannin wash downstream from forests (Peter T. Harris et al Seafloor Geomorphology as Benthic Habitat 2011 Science) observations of the Connecticut River in the Essex Old Saybrook. The Connecticut River was brown for several days after a heavy rainstorm – no upward flows. Some blue crabbers described it as “oak leaf tea.”

In some historical texts look for references to Mahogany waters on Tannin Black Waters on ebb flows in rivers. Not to be confused with the coast by brown algal tides of the 1980s. These references often mention sawdust or wood pulp (paper waste) pollution in rivers as a possible pollution source. One of the most discussed cases was the Androscogsin River in Maine but others exist referencing brown or mahogany waters. This is also the results of leaf matter tumbled or broken apart in fast moving water to make what has been described a brown “Tannin Tea.” That is noticeable, what is not is the huge amounts of organic debris below the surface a slurry of leaf litter and forest “duff” washed into rivers and creeks. This is what turns water brown as tannin also a toxic substance can add to respiratory stress. Most tannin fish kills are associated with “black waters” often a sulfide rich event that can even be attributed even to green leaves (see ).
Some experiments with turn of the century sawdust exhibited similar sulfide toxic impacts upon river and stream life.

Paul Galtsoff in 1937 undertook a study of the York River, Virginia oyster beds. Oyster farmers had complained that for some reason oysters would not grow and appeared to have poor meat quality. Oyster harvesters had identified a paper mill as a possible reason for the problem. After several plant wash pulp water tests (all negative), researchers started looking at salinity, food availability, oxygen levels and temperature and found no concerns until be tested the black liquor (the reduction if wood pulp with high heat sulfate) with oysters in controlled conditions (tanks). Eventually when subjected to “black liquor” oysters weakened and then gapped before expiring. The problem with this finding is that the plant (part of the Kraft paper process) recycled its black liquor as it helped digest incoming wood pulp. The plant had become in fact a speeded up end result of cellulose digestion in the absence of oxygen (oxygen levels downstream of the plant were found to be sufficient) by the depth of organic deposits.

What was most likely happening was sulfide production in the York River bottom waters – from any organic deposit – manure, leaf fall, wood waste and forest litter overwhelmed the River. As organic deposits grew deeper so did the problem – a gradual habitat reversal of Sapropel. The end of the study the researchers commented that some subtle change had taken place in the York River “the nature of which could not be determined.”

While mentioning at the end of the river had weak tides and some “stagnation.” It is thought that over time when organic deposits grow deeper sulfide toxicity increases. The Currituck Bay report clearly mentions a deepening organic layer that seemed to be in constant motion adding to turbidity (1909-1919).

A more recent organic sulfite event that occurred in low energy high heat conditions was a Rhode Island upper Narragansett Bay event in 2003.
The Rhode Island Fish –Shellfish die off of August 20th 2003 in Apponaug Cove has a similar case history. Although a Rhode Island DEM report mentions hydrogen sulfide as being toxic to organisms and it is produced by sediment chemistry and bacterial processes (Pg 3) it focused mostly upon levels of dissolved oxygen. In areas oxygen levels dropped to zero as white bacterial matts (mislabeled as sewage fungus in the 1950s) formed. On page 15 of the report it mentions a gradual decline and “the stench of dead and decaying macroalgae has been a frequent complaint in the Greenwich Bay and other upper bay areas in recent years” pg 15. This alludes to the gradual changing habitat quality – a series of smaller less severe events.

Connecticut had a recent example in the Black Hall River with a February 2014 fish kill that numbered around 1,000 small striped bass. A severe cold snap was blamed for the loss, although the river has deepening deposits of organic matter termed Black Mayonnaise and perhaps undergoing sarpropelic degradation – a natural process in high heat. In winter with cold temperatures these deposits can shed sulfides especially under ice floes. Upon investigation it was learned from river neighbors that this was not the first fish kill (although it was the largest) that in 2013 – 2014 winter about 80 dead stripers will seen and 2012-2013 several dozen were observed dead. As habitat conditions decline the number of these types of events increase in the historical literature.

One of the symptoms of sulfide accumulation is that conditions gradually decline two or three fish kills before a massive one, the other symptom is a growing eelgrass meadow.

Eelgrass therefore has a questionable role in gathering these organics deposits as they reach the coastal zone. They can transition previous hard, firm and at times cobble habitats into those that are soft and organic matter filled. This is why in so many references over time eelgrass meadows tide to rise. In high heat and low energy leaf litter is made into a toxic deadly deposit – helped by eelgrass. Any environmental service (such as carbon sequestion) should be offset by the habitat transition capacity of eelgrass itself. Not to discuss pore water sulfide levels in deposits under eelgrass is a research omission that deserves a second look – my view.

Marine Habitat Succession – eelgrass stabilizes organic deposits

Bivalve shell layers below eelgrass confirms such habitat succession, events do in fact occur. Research by the Virginia Institute of Marine Sciences (Moore and Orth 1997) in a paper titled “Evidence of Widespread Destruction of Submerged Aquatic Vegetation (SAV) from Clam Dredging in Chincoteague Bay” Virginia found much the same impacts and confirms such earlier observations on Cape Cod. When energy is applied (in this case clam dredging) sediment habitat quality was very different, later page 2 of the paper contains this section. “Sediments later within the dredged scars (areas jetted to obtain clams) were very sandy with an abundance of broken clam shells and relic oyster shells scattered throughout. Outside of the scars (dredge) the sediments were much softer with a surface layer of fine sands and organic matter observed between the SAV shoots. Apparently the dredging had completed disrupted the sediments changing them from organic rich sands to coarse sands and broken shell and had removed nearly all the SAV vegetation, as well.”

It is the buried “relic” shell layers that provides evidence of habitat succession. Energy perhaps guides habitat succession - although negative –and sets the state for renewed habitats in long cycles along our coast.

In northern areas the environment services of eelgrass appear to follow energy/heat climate cycles. The observations of buried bivalve shell in the Chesapeake Bay area provides clues that bivalve shell (species) once pre existed eelgrass. On Cape Cod some areas had 20 inches of built up eelgrass over dead Quahog beds (personal observations Pleasant Bay Cape Cod, 1982). Shellfish researchers during this period frequently mention eelgrass displacing shellfish beds in the span of two decades. This is often the problem of snapshot ecology and the bias of perspective made famous by Daniel Pauly in his report entitled Shifting Baselines, (1995).

If the environment services of eelgrass are transitioning then its ability to shelter Blue Crab Megalops change over time as well. It may be that the cycle of eelgrass may help Blue Crabs but in extreme cold and heat perhaps not. From current research the concept of very dense eelgrass meadows all the time is not natural nor does it seem sustainable considering what we can learn from long term habitat observations.

Habitat succession is a natural force- we may not like the consequences but energy input is integral to our natural world. Forest ecologists who faced the same habitat dilemma after a series of horrific August 1910 forest fires. Over three million acres of forest were consumed in what was called the “Big Blowup” in Idaho and Montana, fire and smoke spread across the Northeast all the way to the coast. Fires continued to burn even to the first snowfall, but next spring the wildflower bloom was the best ever seen. [After the Fire, Roddy Scheer, 2001]

The “Big Blow up” [1910] created the public policy of fire suppression for the US Forest Service. Unfortunately this policy no doubt saved timber and human lives but set up the stage for organic matter to build up (sometimes for decades) and fuel for even more horrific and devastating fires in the years to come. A snapshot look at fire suppression gives a positive outlook but forest ecologists have come to realize that this is not sustainable over long term periods, energy elimination is not natural and has more severe consequences. In the 1970s a theory of controlled or prescribed fires, became public policies as habitat fire succession information linked smoke to seed germination, controls of pests and parasites nutrient recycling- opens tree canopies and increases coverage of natural vegetation (Abstracted from Native Plants, volume 20 #3, Spring 2004).

It appears that we have had four cycles of eelgrass in recent times, very low in the 1870s, very high in the 1900s, low in the 1930s and high in the 1960s. The 1990s were low, so look for renewed eelgrass meadows after our recent storms. This is offset from the cycle of Sapropel, which shares a similar pattern or cycle. Sapropel when in high heat sheds huge amounts of ammonia is recognized as a limiting extreme habitat type, Yale University (New Haven) was the first research institution to point out is negative habitat characteristics three decades ago.

Hurricanes are Marine Forest Fires.

Look for areas in New England that took the worst pounding as waves cleared out putrefied organics (Sapropel) to have the healthiest eelgrass populations decades later. Some evidence is coming in that following New England dredging projects (Boston Harbor) some of best “clean and green” new eelgrass are near them. Although contrary to public policy concerning eelgrass non bottom disturbance appears to be in conflict with habitat succession and positive ecological services generally unsustainable over long time periods. Without energy such monocultures over time are also subject to massive disease outbreaks (This is a problem with agriculture also). This happened to eelgrass in the 1930s and 1980s, following historic thick growths. It is these thick growth periods that support eelgrass populations are subject to natural cycles and why at these times observed to be in conflict with shellfishers. The cycle appears to be an old one.

In a book by Henry Moore 1897 describes the need to protect oysters from strong vegetable growths on page 318 is found this excerpt “In places where eelgrass (Zostera), etc grow so rapidly as to cause stagnation of the water and suffocation of the oysters some means must be adopted for its removal. Sometimes it may be removed with an ordinary scythe at low water – a grower in New Jersey has invented for this purpose what has been termed an aquatic mowing machine – it is described as follows – eelgrass grows abundantly in some parts of the Navesink River, and as in other localities where it is found, acquires in due time full possession of the areas where it grows (a characteristic reference of habitat succession T. Visel) rendering them useless for oysters culture. In combating this enemy of the oyster planting industry. Mr. Charles T. Allen of Oceanic New Jersey has achieved success here to fore unequaled, he invented in 1885 and has since used a device (underwater) which may be termed an aquatic mowing machine.”

This was written in 1897 at a time of massive habitat reversal, it would be another decade before the heavy growths of eelgrass would fully hit New England, and Samuel Cabot would witness windows of eelgrass six feet high on Revere Massachusetts beaches (horse teams were required to remove it so bathers could reach the ocean. In 1893) Samuel Cabot created insulation of layers of dried eelgrass stitched between sheets Kraft ™ of heavy paper – the product the first roll insulation was called Cabot’s Quilt™ and dominated the household insulation market until the 1940s.

One of its attributes as an insulating material was its extremely high silicon level in its leaves – it resisted burning and would not rot. A 1918 magazine advertisement in “Better Fruit” on pages 10 and 11 has this statement as Cabots Quilt gradually took over the cork insulation market.

“Cabots Quilt™ being composed of a matting of eelgrass quilted between two layers of Kraft™ paper, the eelgrass has a tough flat fiber that forms thousands of dead air spaces, making the ideal insulator. Eelgrass grows in the sea and is composed of silicon in place of carbon that exits in plants that grow in the air, and it will therefore not rot, will not harbor insects or vermin and will not burn.”

The high silicon levels in the leaves soon made eelgrass a popular insulating material for icehouses (1890s). Sawdust one of the chief insulating materials in walls supported combustion and at times even fires. The high silicon levels in the leaf blades also protect it from sulfides, but root tissue is softer and eventually vulnerable to sulfide damage. Contrary to common perceptions energy or any cutting/disturbance that release organics, sulfides and injects alkaline sea water into the soil can help eelgrass maintain its hold in estuarine soils. Eelgrass according to shellfish reports tends to build after strong energy events (hurricanes) – the start of its habitat clock and tends to fail from low energy and heat by sulfides it helped create or disease, something that impacts monocultures on every continent.

John (Clint) Hammond a retired oyster grower from Chatham Cape Cod who in one of his many conversations with me about the habitat aggressive eelgrass in Quahog beds likened it to visitors who come to visit for a few days and never leave – eventually taking over your house. That is what he described in the 1960s eelgrass would appear in small patches but eventually these patches merged – slowing currents and collecting organics. In the end it suffocated hard shell and bays scallop habitats and then became “black” and died off. What seemed to start the eelgrass growth was recent energy (soil cultivation) and periodic thinning, he (Mr. Hammond) used thinning a row of carrots as an example, the healthy eelgrass was “clean and green” near channels, edges, good flows and recent dredging projects. The “brown and furry” eelgrass was on flats in areas of slow currents and soft bottoms. Here shellfish could no longer be found. It is these areas that eelgrass first started to “die off.”

Almost any type of disturbance that thins the roots or releases organic/sulfide rich deposits seems to help eelgrass. The current series of storms (high energy) areas should see eelgrass “recover” first in them describing a cycle of habitat succession that could be a century in length. Several quahogers on Cape Cod noticed that in places they raked for clams was often the first places to see eelgrass plants. They attributed its spread to “runners” subsoil lateral roots that spread out in loose soil in radiating patterns. In the end these quahoggers would declare war on these eelgrass habitat invaders.

When you look at efforts to control eelgrass some of which started in Chesapeake Bay in the 1950s and early 1960s, they all mention habitat shifts – Goodman et al (1995) found that photo synthesis and growth of Zostera marina eelgrass was inhibited by induced elevated sulfide levels – it times of heat this impact would become called die offs.

The “trouble with eelgrass” became apparent to shellfish researchers and state biologists by the mid 1960s. Estuarine soils along the New England seaboard had been “cultivated” by an tremendous increase in coastal hurricanes in the 1950s. Extensive erosion had occurred and the lighter deposits of organics removed by storm waves and tides leaving a sandy and mixed soil often containing bilvalve shell fragments, ideal conditions for eelgrass (and other SAV) growths. In now stable conditions and available nutrients submerged aquatic vegetation surged increasing habitat “coverage.” Some of the first areas to notice this habitat transition were areas to our south.

On May 5, 1965 the Maryland Department of Chesapeake Affaires (Manatee Project) Harold Elsner a fisheries biologist writes a report explaining the problem. This is not an isolated account – similar reports from coastal areas extend all the way to Cape Cod and into the Canadian Maritimes. [See Appendix #1]

Biologist Elsner writes -

“The problem plants are of two types the large usually rooted plants, and the microscopic, free floating organisms known as phytoplankton… 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 eater which often results in fish kills. Sometimes the Plankton washes upon shore and rots, producing vile odors.”

{Canadian and United States shellfish biologists looked at first to control eelgrass apparent habitat aggressiveness with just cutting, mowing and digging but by the late 1960s more severe attempts had been tried including chemicals hydraulic jetting (even explosives in Connecticut) treatments. John Hammond recounted the shoveling of a pelleted herbicide he termed “Agent Orange” but most likely 2, 4, D into areas of Pleasant Bay (1971-1973).}

Harold Elsner writes on page 2 of his 1965 report that the use of pelleted 2, 4, D. on trials (testing) was well underway in the 1960s in Maryland.

“There are many chemicals which can be used to control aquatic weeds. Of these, the most popular, and one of the safest to use, is 2, 4-D. This chemical can be used in its liquid form in lakes, but in tidal waters it is moved about so rapidly by the currents there isn’t time for it to be absorbed by the plant. To counteract this tendency to be carried away, a pelleted form of the material has been developed. This consists of 2, 4-D impregnated in clay particles and so processed that the clay disintegrates slowly, releasing the 2,4-D about as fast as the plants can pick it up. Other recently developed herbicides have not been as thoroughly tested in Maryland tidewater and, as of this writing; the State does not allow their use for aquatic weed control” and continues later in the report.

“Of special interest is a device built by an Annapolis man, Mr. David Talbot. His machine is designed to uproot the vegetation, using strong hydraulic jets. This device is especially valuable at swimming beaches because, in the violent bottom-stirring action, heavy debris such as glass and metal becomes buried under the sand.” In this case the jetting was a temporary habitat adjustment (similar to lawn care) and the cultivation most likely enhanced soil characteristics suitable for eelgrass.

{John Hammond also similar jetting projects on Cape Cod, especially in swimming areas but felt all that was accomplished was the spread of rooted plants and eelgrass soon returned to the jetted areas many times denser than before}.

The concerns in the 1960s also included other species of SAV even sulfides, Elsner continues- “Another important feature is that dense beds of milfoil create muddy bottoms by serving as settling basins for silt particles. Extensive beds can damage oysters and clams by slowing down water circulation and cutting off oxygen supplies to these animals. Large fish find it difficult to swim in thick weeds. Although fry and larvae find adequate protection and an abundance of food.”

“The problem associated with sea lettuce is not one of restricting boating, swimming, or fishing, although it sometimes interferes with oyster tonging. Its nuisance value comes from the fact that broken fragments of the plant tend to collect in favorable sites (small coves, bays, etc.), where they pile up on beaches and rot. In the decaying process hydrogen sulfide is produced. This gas has a rotten-egg odor and often becomes so strong that lead paint on waterfront houses is discolored. Silverware becomes badly tarnished and copper is often affected. In sufficient concentrations, hydrogen sulfide is a health hazard.”

(This mention of hydrogen sulfide stains is also found in the historical literature for Long Island New York, and the Narrow River system in Rhode Island)

The Cycle of Eelgrass

The cycle of eelgrass appears to be impacted by the collection of organics. Although New England’s climate moderated after 1920 – organics continued to accumulate (lacking any severe storms) until the warm winters of 1931-32. It is suspected that high sulfides may have weakened the plants in the 1920s as later eelgrass died offs first occurred in the shallows poorly flushed areas first. Later as storm intensity increased into the 1930s sapropel deposits (with eelgrass holding it) was washed away. During the very stormy 1950s and 1960s eelgrass now “retreated” into the shallows away from the high energy areas – and as the storm intensity warned after 1965 eelgrass then advanced back out into deeper waters. Not all areas would recover quickly the 1938 hurricane had changed the morphology of so many coastal areas, left cobblestones in areas of soft eelgrass meadows and deepened others changing energy profiles of these habitats – with new depths and changes in topography some areas were replaced with the kelp/cobble stone. (Restoring eelgrass to high energy areas is not realistic).

It would take decades for this habitat to again reverse if at all. Some areas were so changed after 1938 they will not hold eelgrass again.

When our climate warmed again in the 1970s -1980s heat allowed organic matter to increase (build up) again and the same pattern of eelgrass die off occurred except in different areas. The areas first to go – the slow or “stagnant” waters that obtained large amounts of leaf material, organic compost which became known as black mayonnaise. Many eelgrass reports include observations that eelgrass is an effective stabilizer of organic deposits (which it is) but frequently leave out discussions about the levels of sulfides below them. Some of the early eelgrass research often looked at many variables or questions regarding the increases and declines of eelgrass. (See Wax and Wane of Eelgrass Zostera marina and Water Column Silicon Levels – Netherlands Institute of Ecology – Herman et al Marine Ecology Progress Series 1996, Vol 144.303 –30, Dec 1996). Some reported that the availability of silicon was thought to be more of a factor in eelgrass declines than nitrogen loadings. Authors looked at declines of silicia acid from rivers from coastal weathering processes as one factor in declining available silicon for eelgrass plant tissue during low water flows – droughts. Low silica availability is one factor that might be intensified in high heat and lower rainfall.

The high level of silicon in eelgrass is most likely responsible for it being largely rejected as a fertilizer. In a 1904 Report of Commissioner United States Commission of Fisheries has a section that talks about “Aquatic Products as Fertilizer” pg 278-299.

“Eelgrass taken by itself has little or no fertilizing power. It will hardly rot
anywhere, either in the ground, in the hog sty or in the manure or compost heap. It is a distinctly inconvenient thing, more over to have in the way of the plow shire or during fork. Considered as a manure it was rejected by the farmers long ago. It has been tried and found wanting by generations of men.”

And later the report continues -

“The trouble with is, as was said before, that it will not rot in the soil.” Pg 279. High silicon leaf levels is believed to have been the source of this “trouble.” The silicon levels in eelgrass might be related to heat, dry periods which reduced silicon inputs available for growth – i.e. silicon became a limiting factor (see Possible Cause of Eelgrass loss in Frenchman Bay Maine 2014 Disney et al The Bulletin, MDI Biological laboratory 53.2014). The availability of silicon appears to have a possible climate/rainfall connection. Less rainfall would allow salinities to rise indicating additional supplies of seawater sulfate were available to bacterial reduction collected by eelgrass. Vander Heide et al Immunology Oceanography 54 (6) 2009 ranked sulfate reduction second to the availability of light as two easy to measure variables in explaining the presence and absence of temperate seagrass populations (Zostera species). Part of the conclusion includes sulfate reduction and sulfide concentrations.

Eelgrass researchers had also found an acidic link to such organic deposits (often captured by eelgrass). James L. Kellogg a noted shellfish researcher of the last century in a study of the soft shell clam included observations of marine soils. In a United States Commission of Fish and Fisheries. George M. Bowers Commission Part 29 Report of the Commissioner for the year ending June 30, 1903 (published Washington DC GPO 1905) Kellogg on page 224 details some of the negative “humous acids” upon bivalve shell formation in marine soils.

“Experiments indicated that the character of the bottom had much to do in determining the existence of clams those soils containing much decaying vegetable (organic) matter destroys the shells faster than they could be built up, the active agents being the humous acids formed in the decay of plants.”

From the available scientific initiative submerged aquatic vegetation (SAV) has different environmental services under different climate conditions. It appears to follow massive energy events, just as wildflowers after a forest fire, eelgrass appears to follow hurricanes.

The Role of Eelgrass –

Like terrestrial grasses eelgrass appears to have a specific habitat role – holding estuarine soils. The largest difference between stabilizing forest soils, eelgrass can change entire profiles – there is no tree canopy to speed habitat succession. The concept of habitat of eelgrass stability needs a review. Estuarine habitats (stable) can become unstable in healthy habitat profiles, the open beach front for example. Here stability can be measured in a single tidal cycle. It is natural to have constant habitat instability while other areas years or decades before natural forces create change eelgrass vanquished to these habitat refugia areas until energy lessened and temperatures increase. Then began the advance of eelgrass (again) mentioned in so many state and local shellfish reports.

Stability and collecting partially decayed organics in areas of low flushing or poor tidal exchange as a positive estuarine health indicator, is in conflict with studies associated with some of the first Salmon farms. Here the accumulation of organic matter was seen to increase sediment sulfides (uneaten food and fecal matter) and was to shift from sulfide sensitive to sulfide tolerant species (favorable) until sulfide levels became high (annelid worms and some crustaceans). Rapidly accumulating organics did influence total sediment sulfides and reviewed factors of location, season and temperature in sulfide formation (Brooks 2001 – TAG British Columbia Ministry of Environment Canada VAT – 6J9). Compounding the evaluation (called total volatile solids) were those organics that could under go oxidation – reduction was the appearance of “woody debris, eelgrass and macroalgae” as this material does not decompose as quickly as animal waste which has a high immediate BOD – Biological Oxygen Demand. This is the material that eelgrass collects, woody tissue, leaf matter that can slowly rot in oxygen limited waters. Most salmon growers realize now the need of oxygen to quickly break down organic matter (fish manure) minimizing sediment change – no where here have I found studies suggesting that such farms locate in poorly flushed bays or coves with oxygen depleted waters or as to allow the accumulated of partially reduced organics as a positive habitat factor. Some recent eelgrass studies appear to indicate, that as a positive environmental factor, when it high heat it can produce sulfide a very toxic compound.

Much of the controversy which now surrounds eelgrass regarding nitrogen policies is that nitrogen TMDL levels were designed to protect it. Not included in eelgrass/nitrogen studies was the impact of temperature and energy. Water clarity mentioned often as an eelgrass stressor is also water temperature dependent, colder water can sustain more less plankton (any winter time beach visitor can attest to such occurrences) and therefore clearer. When New England was in a cooler period (a negative NAO) water visibility was on the average better – waters were clearer because waters were cooler.

In times of cold and frequent energy events (storms) gives rise to the clean and green eelgrass and its positive habitat services. In times of great heat and low energy (which can be several decades in length) eelgrass helps to form Sapropel deposits and toxic sulfides – its deposits the rotting residue leaves and take on sticky or greasy consistency digested (waxes paraffin rise).

In very high heat enormous of quantities of ammonia can be released as a result of the organic reduction process.

With the prospect of global warming and increasing water temperatures for fish and shellfish eelgrass is not always a preferred habitat type. In fact, the habitat succession attributes in warm temperatures puts eelgrass as a negative habitat type in shallow waters subject to intense summer heating. Here are some of the first negative habitat impacts, it turns black, can be covered in gelatinous epiphytes, slows tidal currents and traps organics. Here these conditions give rise to the brown and furry eelgrass that lives in Sapropel habitats and fosters dangerous sulfides. These sulfides may increase over time killing the eelgrass or weakening it for disease. The continued absence of sulfide pore water discussions under eelgrass meadows in high heat gives a biased view of eelgrass. In times of gradual warming eelgrass tends to “move” into cooler waters. As the 1890s came to close eelgrass populations surged into Long Island Sound, Narragansett Bay and even Buzzards Bay by the 1910s. As waters cooled and disease eliminated many populations eelgrass retreated into protected coves and bays vanquished to these habitat refugia until energy lessened and temperatures increased. Then began the advance of eelgrass (again) mentioned in so many states and local shellfish reports. It may be that the cycle of eelgrass in New England resembles a wave – that reaches the cooler waters last as warming begins, and in colder times falls back into more stable cooler habitats. We may even have strains from the North Sea carried aboard ships or even imported into the US (Cobot Corp at the end of the latest habitat cycle imported German eelgrass bales in the late 1940s). The cycle of eelgrass is far than complete and to base environmental policy upon it is suspect until we fully explore all of habitat history is unclear at best.

Eelgrass Could Save The Planet?

That was the title of recent Boston Globe article (November 9, 2014) by Derrick Z. Jackson. The article described sea grass ecosystems ability to store carbon making the mud below eelgrass perhaps “the most precious mud in the world.” The article describes a mud sample about 8 feet below there because there is little to no oxygen, bacteria can take centuries to break it down and re-release it (carbon) back into the water.” On the chemical level (analytical) that is absolutely true – the storage is a component of available oxygen. Organic matter built upon terrestrial soils are quickly recycled back, along with its carbon content. It takes a long time to build organic soil horizons on land (about half-inch a century).

But in the shallow marine habitats, it can build much faster and at times be measured in feet. That is because bacterial sulfate reduction is very slow. We have the examples of peat bogs and salt marshes over glacial fill with core studies. But few such articles mention the negative consequences of high heat organic matter storage systems, even including salt marshes. In high heat, these organic deposits sustain sulfur-reducing bacteria that leach effluent that would most likely fail today’s Clean Water Act (CWA) discharge requirements. They in fact under these circumstances be considered a potential non-point source of nutrients including ammonia and sulfides (1994 Wetlands Investigations, Guilford, CT).

Often these eelgrass reports give the opinion of habitat stability, but they are not. In fact, at times they are naturally very unstable. They are influenced by the lands adjacent to them, rainfall, vegetation growths (types) and temperature.

Sulfate reducing bacteria cannot quickly break down complex cellulose compounds especially those with high paraffin levels, such as acidic oak leaves. Storing huge deposits of organic matter in coves has many of the same negative habitat environments as excessive terrestrial deposits also deprived of oxygen and most gardeners recognize the beneficial impacts of turning over the compost pile to add additional oxygen. (Nature’s way to turn estuarine composts is by periodic storms clearing as something we may feel is negative or destructive but simply a series of long cycles that appears to be natural). As with any habitat reversals there are clearly some habitat “winners and losers.” It is not natural with energy cycles to find eelgrass always a dominant habitat feature. The truth may be that high eelgrass populations signal more of habitat change process than renewals.

After the 1938 Hurricane the habitat profiles of Connecticut’s coast was so altered many areas may never support eelgrass populations. Sea level rise is an important aspect here for layer habitat reversals – some areas were stripped of sand leaving acres of cobblestones.

The early New England salmon industry came under close environmental scrutiny for excess organics in the 1970s – organic matter from feeding would often settle on bay bottoms in a low energy/current areas and could build up over time. In cold water some organisms increased in these areas but in time sulfides would form and habitat profiles changed. This organic matter was soon found to be limiting to oxygen requiring organisms – created temporary shifts in species dominance and in time produced sulfur sulfide compounds. Careful site selection and recovery periods allowed this organic matter to be dispersed and enter the marine food chain. Eelgrass meadows collect much the same organic matter and accumulations they tend to rise over time. In high heat sulfide levels can reach toxic levels even for the eelgrass plant itself. Which in shallow water after 1938 supported “new” kelp forests – important as a final lobster nursery area or habitat not eelgrass.

Most of the eelgrass reports also do not include climate factors such as temperature and energy, some fail to mention the consequences of high levels of organic matter in creeks and bays in these often warm shallow areas and presence of sulfides.

New England has experienced four such periods --a period of cold and high intensity storms followed by periods of general habitat stability – hot and with little storm activity. The cycle of eelgrass also appears to follow such natural patterns, as evidenced by accounts of fishers who once thought of eelgrass as a foe, not a friend.

Could eelgrass save the planet? If the organic matter collection in increasing heat (global warming) is the way it would, I have many questions – warm water, organic source ammonia, and sulfate reduction by bacteria would strengthen the sulfur cycle – putting those organisms that need oxygen at risk. If the planet was saved by eelgrass it might not be for us. – My View.

Appendix #2 Organic Matter Sulfide Toxicity A Case History

Paul Galtsoff and York River Virginia Oyster Investigations 1935-37

Preliminary report on the cause of the decline of the oyster industry of the York River, and the effects of pulp mill pollution on oysters by Paul Galtsoff, Water A. Chapman, Arthur D. Hasler and James B. Engle (1938).

This 1938 report with Paul Galtsoff (later a distinguished Bureau of Commercial Fisheries (Interior) oyster researcher) and James E. Engle (who later went on publish many shellfish research papers) with Water Chapman and Arthur D. Hasler gives an unique view on manmade versus natural organic matter pollution. It also gives a viewpoint of the habitat condition/transition just prior to the 1938 Hurricane following decades of heat. Many historic habitat transitions occur during periods of low rainfalls - an enhanced tidal wedge brings saline bottom waters far into estuaries and with sulfate now in non limiting quantities fosters sulfate bacterial reduction. Many habitat changes occur in heat and drought changing the ebb flows (and thereby residence times of nitrogen/and ammonia compounds in heat). In the historical conditions are often described as foul stagnant waters. Often such reports are accompanied by noxious fumes and smells of sulfur – the most common example of the 1880-1920 period in New England was that of “rotten eggs.” The high heat putrification of organic matter sealed from oxygen by the smell of sulfides. It (the report) gives an example of high heat organic mater digestion and possible damaging natural sulfide residues. The investigation of the York River Oyster fisheries was to respond to complaints of oyster growers concerned about pulpmill pollution impacts from a paper plant discharge near West Point. Oysters would not grow and oyster meats described as in poor quality suggesting slow starvation.

The pulpmill plant which opened in 1913 was cleared in 1917 of pollution but the 1938 report mentions that some subtle change had taken place in the York River “the extent and nature of which could not be determined” pg 3. In 1918 Gutsell and Churchill (also distinguished oyster industry researchers) had looked at sulfites and sulfides which were known then to “exert deleterious effects on oysters” but no field tests were done. It was most likely upon exposure to air any sulfide bottom organic samples would quickly react with oxygen forming sulfuric acids. (This is the same situation today with the Army Corps definition of acidic sulfate material as dredged material once these deposits obtains oxygen it becomes acidic). Terrestrial farmers a century ago who used this marine compost to nourish soils experienced much the same toxic result. Gutsell and Churchill did comment that it appeared that sampled oysters “were starving.” The York River peak oyster production year was 1912 just prior to the papermill opening and one of the few
studies during a period of high heat and organic matter digestion that had most likely entered the Sulfur – Sapropel cycle. The habitat change had been noticed and on page 9 is found this statement “In deep channels soft mud predominates.” This is one of the observations that are associated with organic matter accumulations, which in low oxygen conditions takes on Sapropelic qualities.

The paper plant which began operating in 1913 discharged about 1 million gallons/day of pulp wash water containing fragments of bark and pulp into the York River – by the late 1930s it was five millions/gallons a day. The paper plant utilized a much faster process of tearing apart cellulose tissue for paper “lignin” than natural sulfate reducing bacteria could ever do. These plants utilized a Kraft sulphate process which digested the pine chips at high temperature producing a black liquor that was recycled and retuned to the digestion tanks – rich in sulfur compounds as basic as lye. This had the ability quite simply to strip away the woody tissue around the lignin which then fibers was reconstructed fibers for paper products.

Tests of the York River oxygen levels didn’t exhibit any differences between growing areas – oxygen is lower during the summer months due probably to the increased oxygen demand of the waters at higher temperatures, pg 16 oysters moved from the York River to other growing areas recovered and grow/feed normally; there was plenty of food in the water, as compared to others used in growth trials it was dry in the summer of 1936 and salt water flowed far inland. Oxygen did not appear to be a concern. Researchers drew a blank until they tested the black liquor on oysters in tanks – here the results were profound – oysters closed and did not open – when they did open they did not feed long and in time starved. The tests with black water were conclusive but researchers did not link the plant – it recycled the black water and in time dried the sludge and disposed of it away from the river. The pulp and wash water containing organic matter in the natural world although much slower was part of a much larger natural sulfide event. Although the black liquor was harmful to oysters they pointed at something else, that the environmental conditions had changed, and the York River had a small excess of ebb tides – “This condition (the researchers concluded) tends to aggravate the situation by creating a so called tidal stagnation and gradual accumulation of toxic elements in the river” pg 42.

It is hard to completely review the habitat conditions, but drought, heat low flows and stagnation with organic matter residues are all indications of the sulfur cycle. The plant did contribute organic matter (as lumber mills with sawdust) but in high heat conditions the habitat transition was largely natural, did the pulp from the plant contribute certainly, but was it all the plant, no most likely not. In times of habitat failure we look to our activities as a chief reason – when overall it is not. Did researchers give the natural world a free pass when it came to the York River – no not really they knew the impacts of sulfides back then and black liquor tests were conclusive but did not have the evidence of large scale natural sulfur digestion event although alluded to it. The report most likely did not please either the oyster growers or the plant owners. Heat was also cooking the organic matter slowly releasing the lignin to the fate of sulfur reducing bacteria on the river bottom and with it toxic sulfides – (It just was a lot slower than stream boilers).

But the black liquor tests were conclusive and carried forward whether they were discharged into the York River or not. It tagged the plant as a pollution entity but the impact its organic discharge in relation to leaves twigs from other natural organic sources remains in question.

High heat digestion of organic matter did produce sulfides (sulfur compounds) and those compounds certainly if present had a negative impact of upon oysters. One of the indications of sulfide toxicity to shellfish is slow starvation and thin often “watery” meats.

One may question therefore the impact of increased organics in high heat – in the presence of sulfate in oxygen depleted conditions, whether it be collected and held by vegetation (eelgrass) or accumulates in slow poorly flushed tidal restricted areas or washed from land as leaves. Although eelgrass has been recently praised for its ability to capture and hold organics we need to look at that very carefully. Any collection of organics in high heat poorly flushed areas has at times severe habitat consequences.

Some of the research regarding the Conowingo Dam organic deposits may answer many of these sulfides – sulfuric acid habitat questions in a few years.

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