EC #30 Benthic Flux And The Nitrogen-Eelgrass TMDL Levels

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EC #30
Benthic Flux And The Nitrogen-Eelgrass TMDL Levels
Bacterial Generation of Sulfide and Ammonia Impacts Toxicology Testing
The Bacteria-Nitrogen Series on The Blue Crab ForumTM
Environment Conservation Thread
Thank you, The Blue Crab ForumTM Managers for posting these Habitat and Nitrogen newsletters – over 300,000 views to date
June 2021 revised to February 2023
This is a delayed report – February, 2015
Tim Visel retired from The Sound School June 30, 2022
Viewpoint of Tim Visel – no other agency or organization
(This paper, in draft form since 2015, was revised in 2021.  Since that time, many nitrogen models have been modified for sulfur bacterial composting – T. Visel)

A Note From Tim Visel

The nitrogen TMDL allowances linked to eelgrass health are subject to review.  Many nitrogen TMDL could have a research bias (measuring estuaries typically occurred in hot weather, an analytical methods bias) as ammonia levels generated from bacterial sulfate digestion was possibly counted as human nitrogen sources (See Environment Conservation #8: Natural Nitrogen Bacteria Filter Systems, The Blue Crab ForumTM, 2015).  Residence time (also flushing time), in addition, was often not included.  Much of the nitrogen increase during this period was ammonia and possibly counted as "ambient" and then possibly assigned to human impacts.  Bacterial sulfate digestion linked to sapropel formation was not counted or, if included, assigned minimal value(s) - my view, T. Visel. 

When habitat studies for eelgrass looked at fishery habitats, the low oxygen ecology of such eelgrass meadows for sulfide enrichment was often not included.  In fact, sulfide as a byproduct of organic composting in high heat is also frequently omitted.  Estuary Program TMDL's are being "recalibrated," which is another way of saying amended.  Any TMDL's undergoing recalculation should ascertain that sulfate bacterial (composting) metabolism has been included as a possible nitrogen source – my view, Tim Visel.

Nitrogen models, which fail to include the impacts of bacterial sulfate reduction – (sulfate is not limiting in the marine environment) in high heat that frequently dominates the nitrogen spectrum – may miss very high ammonia levels from bacteria species change, which later sustained brown algal blooms or HAB's and should be reviewed – my view, T. Visel.  Many Cape Cod and eastern New York Long Island fishers reminisce that these brown algal blooms appeared first in hot tidally restricted coves and bays, those that were partially flushed and those often held sulfate-reducing bacteria and had high ammonia levels.  Some of the early research in this area happened in Long Island, New York – the organic matter deposited by a once large duck farm industry there dates back to the 1960's.  Researchers in the 1970's detailed how sulfide emissions have discolored lead-based paint of homes near then at the time from duck slude deposits.  The following is from a large report (US Army Corps of Engineers – Suffolk County, New York titled "Long Island Duck Farm History and Ecosystem Restoration Opportunities," February, 2009) about this duck waste compost in tidal waters and its impact upon nitrogen and algal growths:

"As the duck waste entered surface waters, heavier suspended particles settled to the bottom near the discharge point, while lighter particles were distributed tidally until they too settled throughout the estuaries.  These settled particles of decomposing organic matter created blankets of sludge that consisted of a homogeneous black, plastic material with a strong unpleasant odor."

And also –

"The decomposable organic matter depleted dissolved oxygen, and anaerobic digestion resulted in generation of hydrogen sulfide gas" (Federal Water Pollution Control Administration, 1966).

Connecticut's case history of sulfate reduction, sapropel formation and habitat degradation is similar in many eastern Connecticut coves road and rail bed flow restrictions.  It is here that sulfate reduction by bacterial sulfur strains with sulfides, sulfuric acid and ammonia were first reported by winter flounder fishers (See IMEP #15) in Jordan Cove, Waterford, CT (Waterford Studies Urge Action On Coves, The New London Day, December 3, 1983). 

Winter flounder fishers in eastern CT coves also noticed the build-up of sapropel (black mayonnaise) behind railroad causeways.  In eastern CT, a major rail line constructed in the 1860's cut across over 40 wetlands and tidal rivers.  These railroad bridges had restricted flushing and, in high heat, sapropel accumulated quickly behind them.  One of the first surveys was done in Jordan Cove in 1981, once a popular site of winter flounder fishing.  This build-up of this sulfide-rich marine compost behind rail causeways was noticed throughout New England.  This was attributed to excess nitrogen but more likely a type of "tidal choking" detailed by Welsh et al. in the November 1981 Proceedings of the Sixth Biennial International Estuarine Comparisons, Editor Victor S. Kennedy, pg. 53.  Once saltwater exchange was reduced, an invasive reed "took over" salt marsh habitats (See IMEP #18-Part 2: Invasive Phragmites Habitat War, posted June 19, 2014, The Blue Crab ForumTM).

The Eel Pond Mattapoisett Restoration EPA Project in Massachusetts correctly details how reduced flushing not only forms this marine compost but also changed salt marsh species to that of Asian or European strain of Phragmites, a tall marsh reed (See Cryptic Invasion by a Non-Native Genotype of the Common Reed Phragmites australis into North America, Kristin Saltonstall, 2002).  The following is a segment from a Massachusetts Restoration Project fact sheet:

"Eel Pond has also been long closed to shellfishing due to elevated fecal coliform levels from various sources.  However, few shellfish grow there because the excessive inputs of nitrogen have contributed to large areas of the salt pond having thick layers of fine anoxic mud that has the appearance of black mayonnaise.  Shellfish cannot survive in these kinds of habitats." 

"The cause of the tidal restriction to Eel Pond was the construction of a railroad bridge across the east channel more than a century ago.  At that time, there was only one opening to the bay.  Tidal flow to Eel Pond likely declined for years because of infill to this original channel.  In recent years, further declines in flushing have helped the invasive common reed Phragmites to overtake at least 6.2 acres of salt marsh around the pond.  This railroad bridge tidal restriction is listed as a priority site in the Atlas of Tidally Restricted Salt Marshes in the Buzzards Bay Watershed."

To further complicate the nitrogen TMDL issue, nitrate was often not included in the sulfate reduction process; sometimes nitrate buffering and/or bacterial sulfate reduction were not mentioned at all.  Chances are that many nitrogen TMDL models may not be correct if they excluded nitrogen compounds from bacterial composting.  If that happened, they should be reviewed.  When eelgrass helps the formation of sapropel, sulfate digestion below its root layer actually helps to generate ammonia.  In other words, in high heat low energy (composting) conditions, it adds to the nitrogen problem itself!  Sulfate reduction can completely alter the habitat value of salt marshes during warming climate periods.  If your existing estuary program has linked nitrogen and eelgrass health or submerged aquatic vegetation to a nitrogen TMDL, it is not likely to be accurate unless bacterial nitrogen sources, climate change (warm water) and tidal energy for the residence time of them was also included.  The habitat services of eelgrass in cold and cool water (which are significant and positive for many species) in heat and no soil cultivation (few storms) can, over time, become extremely negative.  The climate aspect of biochemical changes in meadow peat chemistry was often not included as well.  Following are some general concerns:

•   The eelgrass/nitrogen habitat association is likely biased for climate and is incomplete (law of habitat succession) for Connecticut.

•   The nitrogen TMDL was determined largely upon human impacts masking long-term natural impacts and natural sources, mostly the high heat decay of organic matter or leaves (Law of Habitat Succession – Natural Climate Patterns). (See Yale University Nitrogen Reports, Harris, 1959)

•   The "funding effect" that has led to several Congressional reviews seeking if grants compromised university sponsored research (agenda biased science that peer or review panels did not filter/a type of discovery) called a meta-analysis that results supported funding agencies positions more than the scientific literature.

•   Was historical information and long-term climate and energy patterns omitted from public policy discussions (this is still occurring in regards to
the NAO – North Atlantic Oscillation, T. Visel).  Lack of long-term historical balance or cycles actually minimizes the importance of climate change.  This is a great concern as warming is happening and shifting to move dangerous bacteria, such as Vibrio species.  This was predicted in the 1980's on Cape Cod as a new bacterial indicator species.

•   Both the eelgrass/nitrogen indicator and eelgrass habitat models are now subject to citation amnesia or reference negligence, a form of scientific misconduct, that "cherry picks" references (data) that supports a predetermined point of view and ignores those references (most pre-1972) that did not.

•   The need of grants resulted in an organized grant process that tailored conversations to match pre-established interests.  This became part of a positive feedback loop, listening to responses to questions, which were then used to generate reports, thus creating a positive feedback loop that defined specific interests into grant policy. For example, several eelgrass requests for proposals (grants) often were proceeded with a lengthy position statement on how important/critical eelgrass was.  Hopeful grant applicants then responded with a proposal that mirrored a type of group think consensus that agreed with the grantor position statement.  The results of these grants (reports) were then used to justify additional grants in support of eelgrass research.  This research often led to greater SAV public policies.

The bacterial generation of sulfide and nitrogen (ammonium) is so large that reduction in nitrogen from wastewater treatment plants may be overshadowed by climate heating of marine composts – sapropel.  So much sulfide and ammonium from sapropel (both very toxic compounds) caused redefinition of toxicology testing EPA methods for dredge material in 2015 (See Appendix #2).

The emphasis on dredged material testing was detailed in several reports after 2012, a time of peak heating of Long Island Sound.  Concerns were raised that so much sulfide and ammonia were being generated by bacteria that toxic levels alone could kill all test organisms.  Suggestions were made to purge (rinse or aerate) dredge material samples (likely sulfide-rich sapropel) until ammonium toxic levels were reduced to nontoxic levels – determined for specific test organisms.  It was noted that even after sampling bacterial generation of ammonia and sulfide could continue as toxicology tests were underway.

From April 7, 2015, Draft Dredged Material Management Plan Clarification Paper (EPA and Army Corps of Engineers), pg. 6 contains this segment:

"Ammonia and sulfides can continue to be generated in sediment during the bioassays themselves."

Bacteria thrive in warm water and organic-rich, oxygen-poor composts (sapropel).  One huge source of organic matter is not only wastewater but also street runoff and rainfall direct discharges from them. 

Since the beginning of burying open sewers in streets to reduce human disease, capacity was always a concern.  Bury it and send it down the road was the public policy response at the time.  The problem was, of course, lines and outfall pipes did not enlarge with a city's population or number of connections made.  Therefore, design function had a time stamp with cost/capacity.  Very few cities kept pace with discharge capacity.  Heavy rains from street drains assured periodic direct discharge events.  The transition from digestion ponds to indoor facilities took away some of the negatives of the odors (sulfide and ammonia) with open air digestion of organic matter.  The emphasis was from primary to secondary treatment meant that sludge was now often burned instead of dumped as a dry "cake" or layer from open digestion ponds.  The digestion terminology describes a bacterial composting process of breaking down paper and plant fibers from a huge bulk to a few gallons of thick slurry.  It is the same as a huge pile of fall leaves in October to a five-gallon bucket of compost in April.  To speed the process, enhanced bacterial cultures are used and termed "activated sludge" to help speed this bacterial reduction.

This was an attempt to use bacteria to consume (digest) organic matter in the sewage.  It might be correct to think of this process as "wet bacterial composting," which in high heat and ample sulfate occurs naturally on mud flats along the shore.  In cold conditions, ample oxygen yields high amounts of nitrate, a plant nutrient for the good algae - and forage for shellfish while in heat produces large quantities of ammonia – the nutrient for many of the Brown Tide Blooms, those with little nutritional benefit for shellfish (they starve even surrounded by these algal strains) or themselves produce toxic compounds.  The process of bacteria in high heat can utilize sulfate SO4 as an oxygen source, continuing to consume organic wood and plant tissue.  This sulfide can also create sulfuric acid and can be traced to the first iron sewage pipes buried below ground – they started to dissolve.

Storm Water Pipes and High Bacteria

After the dismissal of the Miasma theory in favor of the germ (bacteria) theory of spreading disease around 1900 programs to reduce bacteria commenced, pasteurization of milk testing of water for bacteria and eliminating bacteria in sewage outfalls.  The latter was done with chlorine but was only effective in streams of water with low organic matter.  It was also easier to handle and efforts commenced to settle out solids (an old practice) from the waste stream first by simple sedimentation basins or ponds (that is being generous of their use) that evaporation would leave a cake layer or compost residue.

The proximity of settling basins to the public caused concerns, they did not function well in cold months as ice could form and in summer bacteria produced ammonia and sulfides - they smelled bad.

The capacity of some plants was exceeded (especially during heavy rains) and early flow through systems directly discharged into bays and coves.  Efforts were made to settle out solids and send them to huge bacteria digesting tanks which is a way to say composting.  It is much the same bacterial reduction of bulk plant tissue on land into more manageable volumes and usually the sewage compost sludge was burned.

These composting tanks were called digesters because bacteria consumed the plant tissue and organic matter in the presence of oxygen - and air was provided to keep these bacteria cultures alive- and is often termed activated sludge.  As with terrestrial composting a huge pile of dead leaves is only a pail of compost in the spring, the same basic principle exists here.

The burying of open or "unsanitary" sewers below streets to reduce human disease and the capacity to treat this waste stream has always been a concern.  Heavy rains entering street drains assured periodic large direct discharge events (spills) The transition from digestion ponds to indoor facilities took away some of the negatives associated with open air digestion.  This change however opened a new concern- the increasing paving of streets and resulting "storm water".  Very soon storm water became a large concern of modern treatment plants as it complicated the removal of brown water (also termed street water) with little organic loads from high organic human sewage.  The connections of street storm water drains to sewers were an effort to treat all waste water and lower bacteria by chlorination.  The added flow of water, however, soon overwhelmed sewage treatment plants causing direct untreated discharges.  (Programs are now underway to separate storm water from sewer mains opposite the previous public policy to connect them.) 

Often, storm water pipes from paved surfaces obtained no treatment at all.  This results in bacterial pollution - carrying bits of leaf and organic matter with wildlife bacteria especially from pets.  Storm water bacteria is connected to bathing beach closures and shellfish harvesting closures under the FDA - NSSP, National Shellfish Sanitation Program.  Extensive water testing programs have identified areas subject to direct shellfish harvesting closures based upon rainfall hitting a "closure trigger," so many inches of rain in a predetermined period.   Storm water has become a major source of what is termed "non-point" pollution of both bacteria and nitrogen.  Bacteria flushed into coastal bays and coves from street fecal matter was first noticed on Cape Cod by duck hunters.  Later, studies in the 1980's documented shellfish areas on Cape Cod heavily contaminated with bird feces (See Journal of Field Ornithology, Summer 1981, and personal observations of Lewis Bay, T. Visel).  Street canals and sewage discharges of untreated waste was linked to human disease in the 1890's.

In the 1920's, Typhoid fever was linked to outbreaks from food, one of which was the consumption of raw oysters.  Much of the industry before 1900 was centered on shucked meats put in sealed cans or gallon metal containers banked with ice. These were later cooked or used in stuffing.  Cooking oyster meats could kill bacteria- but with increased market share of oyster consumed raw they were suspected in outbreaks as early as the 1890's.  The winter outbreaks of typhoid in Chicago, New York City and Washington DC in 1924 resulted in a US Surgeon General sponsored conference on February 19, 1925.  A few days earlier New York admitted it was the source of contaminated oysters (New York Times, February 10, 1925) that were attributed to an outbreak of Typhoid.

The conference of federal and state health officials focused upon developing water harvesting criteria based upon detectable bacteria.  Waters with high bacteria indicated potential contamination and then not approved for direct shellfish harvesting, which was termed certification. This program continues today under a state-federal partnership overseen by the FDA.

It is here that stormwater bacteria and certified shellfish beds interact.  After heavy rains, once certified areas could now be closed to shellfish harvesting.

In Madison, CT, I participated in a sanitary survey a part of the NSSP that monitors water quality of East Wharf - once a relay area for a Madison recreational oyster program- 1984 -1988.  East Wharf, a Town of Madison beach was located miles from any sewage discharge or permitted point source discharges.  In late fall the usual oyster transplant time the bacteria counts were very low- nowhere near the closure criteria of the NSSP.  A change in the NSSP required testing all year not just during the bathing beach season of June 15 to Sept 15.  The June tests were very high - so high as to trigger a NSSP shellfish closure.

A sanitary survey was requested as the 14-day relay area for East River oysters was closed.  The survey revealed a metal corrugated storm water pipe just a few feet from the water's edge and adjacent to the oyster relay area.

Additional testing linked high bacteria counts to the stormwater pipe after a heavy rain.  A larger survey focusing on the storm water discharge identified a series of street drains connected to the pipe.

Surveys of the drains revealed the remains of what appeared to be pet excrement (personal observations, Tim Visel during the survey).  Middle Beach road next to East Wharf had become a popular dog walking area.  (This was decades before plastic bag pet dispensers.)

The presence of storm water can deliver high bacteria counts from wildlife.  Areas that contain storm water retention basins have two benefits, one is replacing the groundwater and secondly the use of bacteria to break down organics.  As the NSSP is based on bacteria, reducing bacterial loads is critical to keeping shellfish areas open.  On Cape Cod, I participated in water management projects (early 1980's) during the Route 6 reconstruction that took street water and redirected it into "water recharge basins" where it was naturally filtered and allowed to replenish the groundwater lens. (These are called sidewalk rain gardens today).  However, this storm water from several drains was put into a traditional septic/ leaching system built under the East Wharf beach parking lot. Septic inspection plates are visible marking the location on the lot.  The change of discharging the Middle Beach road to a leaching field resulted in an immediate drop in bacteria levels.  The pipe next to the boat rack was then removed on the east side of West Wharf Town Beach.

Building water recharge basins (sidewalk rain gardens) has become a national priority under MS4 permits.

Rocky Neck State Park on Long Island Sound has a history of high rainfall - high bacteria beach closures.  Several years ago, these high counts were attributed to animal wastes in storm water from heavy rains.  In 2014 Brides Brook was connected to high bacteria from storm water flows by the CT DEEP.
Brides Brook empties into the Rocky Neck State Park beach.

Storm water once a concern of the cities has spread to the suburbs.


Heat Impacts Nitrogen as Ammonia and Growth of Marine Plants

One of the key indicators of a climate cycle impacting inshore fisheries is the account of increases in trash or picking times (increase of plants) for bay scallops and winter flounder – both a type of net/capture gear that also mimics leaf collection.  This increase in algae or seaweed picking time, i.e., the time it takes to separate fish and shellfish suitable for the market – is mentioned many times on Cape Cod and New York by baymen during scalloping and winter flounder fishing.  These changes happen in the shallow habitats first, they warm and ammonia levels increase fueling macro alga blooms that blanket the bottom.  (This is related to a climate/bacterial transition in the soils mentioned in EC #7: Salt Marshes – A Climate Change Bacterial Battlefield, posted September 29, 2015, The Blue Crab Forum™).

It is the thick growths of eelgrass (nitrate) in cool water and sea lettuce Ulva species in (ammonia) heat that slow down fishing – and therefore are mentioned in the historical fishery records over time – compare the statements from The US Fish Commission into the great heat – 1887 of the scallop fisheries – Groton, CT eelgrass segment.     

Notes on The Oyster Fishery of Connecticut by J. W. Collins, US Fish Commission 1891, Groton, CT, pg. 177 – my comments (T. Visel).

"The Poquonnock method (placing of birch branches for off bottom culture T. Visel) has been moderately successful, and perhaps is the best for the locality where it is employed.  The are several reasons why it has not proved entirely successful on which may be mentioned the collection of large quantities of eelgrass about the flats at the mouth of the stream, causes stagnation of water producing such conditions (Putrid smells – T. Visel) that the board of health of the town has caused the brush to be pulled up and destroyed." 

(What is not mentioned in this section is that the Poquonnock River is known to have a restricted tidal opening – a barrier spit that closes in high heat and very deep accumulations of sapropel, an organic compost north of two rail bed causeways.  That is why the oyster sets occurred on the brush).

In the 1960's, comments from small boat draggers "Cape Cod Fisherman" by Phil Schwind, 1974 has this segment regarding skiff trawl fisheries and the soil cultivation aspect.  Cultivation often included moving thick carpets of bottom algae with small trawl nets while capturing winter flounder.

"An explanation of the process of flounder dragging (or otter trawling) is in order.  First, in salt ponds off Pleasant Bay and Town Cove, as well as in the Bay and the Coves themselves, dragging in prohibited by law from May first to November first.  (This is an old law lobbied through by the lobster fishermen to keep their pots from being smashed within the three-mile limit by the offshore fish draggers.)  Contrary to the objections by the casual sports fishermen, flounder dragging in these waters improves the fishing by "cultivating" the bottom.  Frank used to say, "If you don't cultivate a garden you can't grow any vegetables, and the same holds true to for shellfish and finfish."  Those ponds closed by law to flounder dragging, Ryder's Cove, Little Round Pond and Quanset Pond, no longer produce flounders.  The ponds still dragged, Meetinghouse, Lonnie's, Joe Arey's and Mill Pond, still produce – if not as many as formerly, the fault may be laid to excessive offshore fishing by foreign fleets rather than to the relatively miniscule catches of the little boats inside in the winter."

The Rhode Island salt ponds observations of the skiff trawl fisheries share similar observations that build-up of marine plants (Ulva) in heat can cause suffocation and change compost chemistry – emitting sulfides that are toxic to marine life.  A switch to bacterial production of ammonia causes nuisance algae growths.  These plants die, they suffocate the oxygen-requiring bacteria when composting begins.  This is called the sulfide deadline.  In these circumstances, the green sea lettuce (Ulva) turns black from iron sulfide.

From – An Elusive Compromise, Rhode Island Coastal Ponds and Their People by Virginia Lee, 1980, University of Rhode Island, on page 42 is found this segment:

"Eutrophication.  Pollution from excessive fertilization is also considered to be a major problem in the ponds, particularly in coves where circulation is sluggish.  It is thought that nuisance algae are increasing because of increased nutrients coming into the ponds from surrounding residential developments.  Flounder fishermen report that algae are becoming more and more dense on the pond bottom and fouling their nets.  Trawls come up with about 12 bushels of algae with each bushel of flounder even though most of the algae passes through the 4½-inch mesh in the net.  The abundance of algae is not only an impediment to fishing.  When the temperatures rise in late summer, oxygen is used up by decomposing algae, making it scarce for bottom-dwelling organisms.  When oxygen levels are very low, young flounder either leave the pond or die of suffocation.  After oxygen levels are depleted, toxic hydrogen sulfide is often produced, causing the rotten egg smell that lurks over mud flats and back coves.  The increased algal growth may be making the pond environment less hospitable as a nursery and spawning area for a variety of fish and shellfish.  For instance, in the summer 1978, Fosters Cove in Charlestown Pond went anoxic for so long that the oyster spat growing on the aquaculture rafts died."

And for State of Massachusetts Marine Resource Bulletin Series, A Study of the Marine Resources of Pleasant Bay (1967), pg. 25 describes the hand hauled otter trawl fishery – for winter flounder, detailed below:

"The fishery (winter flounder hand hauled otter trawl – Tim Visel) is mainly conducted with small individually operated otter trawls with mesh openings ranging from 3 to 5 inches.  These trawls are towed behind outboard powered skiffs and occasional small in boarddragger.  In general, larger mesh sizes are preferred due to the excessive weed growths in the bay, which have a tendency to foul the smaller meshes.  All but the smallest flounders are retained by the fishermen.  The price differential which favors the larger fish encourages the fishermen to grade his catch according to size."

All these observations point to climate induced habitat changes connected to bacterial purged nitrogen and temperature, and the increase of plant organics in coastal areas.

The collection of fine grain compost is very damaging to shellfish.  We have the records of the oyster industry that detail how the accumulation of fines, either rock flour or organics, can be devastating to shellfish sets and growth.  A Diving For Science or Tide (1989), 5 pages, G.R. Hampson, D.C. Rhoads and D.W. Clark titled "Benthic Mariculture And Research Rig" details growing shellfish above the "Benthic Turbidity Zone."  The article contains this segment on pg. 1 (my comments, T. Visel):

"The system described here is a radical departure from existing practice as the growth structure is located on the sea floor (above the bottom, T. Visel) and the flood resource is nitrogen-rich detritus associated with resuspension of bottom sediment.  Deep muddy areas of estuaries and non-estuarine embayments of New England have been shown to be potential growth sites for commercially important molluscan species, particularly Mytilus edulis (Rhoads et al., 1984 Bulletin Marine Science, Vol. 35, pp. 536-549).  Normally, filter-feeding organisms do not live on these bottom types because of high fluxes of fine sediments that resuspended by tidal scour.  The high resuspension rates exclude natural settlement of filtering organisms by burying them or otherwise inhibiting survivorship" (Rhoads and Young, 1970).
When oxygen is reintroduced, these soils now generate sulfuric acid and a term acid sulfate soil is now recognized in many countries (See EC #13, posted July 2016, The Blue Crab ForumTM). Unfortunately, the negative eelgrass habitat services in high heat have been largely glossed over in the recent habitat literature, citation amnesia, or research suppression, both forms of research misconduct mentioned in recent reports.
This is because much of the environmental community lined up behind eelgrass and other SAV without exploring deadly sulfide, ammonia or even the forms of bacteria species (vibrios) that grows beneath them – some of these strains deadly to seafood and even to us have been known for decades. This aspect is rarely mentioned in the eelgrass habitat services literature.
In many respects, eelgrass was to be the "hammer" to drive the anti-bottom disturbance and conservation policies "home" along the coast. It was promoted in the research community while ignoring the marine soil chemistry consequences of such organic accumulations upon marine soils and the role of root SAV (plants) in collecting them. Over time and in heat eelgrass becomes part of a destructive sulfur cycle in shallow waters. The peer review process needs to be reexamined as this case clearly illustrates it did not bring forward nearly a century of negative observations – just including the positive, and now connected to the "funding effect" investigated by Congress after the 1965 Surgeon General's report on smoking and the funded science that supported minimal health impacts.

A century before that, we had a similar episode in the United States involving snake oil cures – a term today that still denotes that snake oil "science" was something biased or often false.  This science bias was one of the reasons Connecticut's terrestrial farmers supported the nation's first Agricultural Experiment Station (New Haven, CT) to examine massive fertilizer fraud for soils low in plant nutrients and carbon.  But these past cases may be surpassed by eelgrass by the sheer amount of eelgrass literature published since 1972 that missed chemical soil changes and natural long term habitat (It is estimated that over 3,000 articles have been published on the habitat services (See Eelgrass is Great but Shellfish Aquaculture is Better - 2001, ECSGA 2017 Newsletter).

However, the increase of soil bacteria is closely related to its increase of food – organic content in marine soils.  It is fortunate that a marine education program "Project Oceanology" is located on the University of Connecticut Marine campus, known as University of Connecticut Avery Point.  This coastal campus lies on the former estate of Morton Plant, formed in 1967 with Project Oceanology joining the campus in 1973.  Project Oceanology provides students and adults educational opportunities along Connecticut's coast but has focused upon Pine Island Bay and the Poquonnock River adjacent and north of Pine Island.  In 2019, the importance of the Summer Marine Studies Program, conducted over 35 years, was recognized as an important time series record of multi-decadal ecosystem change in eastern Long Island Sound (Snyder et al., 2019, Marine Environmental Research, Vol. 146, April 2019, pp. 80-88).

In 1988, The Project Oceanology Session III, August 8 – August 26 (1988) conducted a study on Pine Island Bay as part of the Summer Marine Studies Program.  In one study by Joshua Brewster of the Williams School titled "Sediment Analysis," a breakwater was being proposed and studies undertaken as a "before" look at the proposed construction site (See Appendix #3).

The study details the organic content of the sediment and connects that to bacterial sulfate metabolism.  The concern was high organic buildup as a result of reduced waves and flushing ability to clear organics from bottom habitats.  Sediment (soil, T. Visel) samples were collected, dried and then burned to remove organics with the results giving organic percentages. High carbon percentages were linked to reduced waves, currents and tidal flushing.  High organics could cause bacterial strains using sulfate as a source of oxygen and then the release of toxic sulfides.  From Brewster (1988) in his Project Oceanology report contains this statement on pg. 2-1 – (my comments, T. Visel):

"The reason there may not be life where there is high organic carbon concentrations in the sediment is that as aerobic and anaerobic bacteria decompose organic matter, a variety of byproducts are produced.  Aerobic bacteria use the oxygen (in the water, T. Visel) and release carbon dioxide, leaving no oxygen (dissolved in seawater, T. Visel) for animal life, while the anaerobic bacteria use sulfate (as a source of compound oxygen, T. Visel) and release hydrogen sulfide during the decomposition of organic matter.  Thus, there is likely to be low or zero oxygen concentrations and high concentrations of hydrogen sulfide or other toxic materials present in the sediment."   

Hydrogen sulfide is highly toxic to eelgrass. In areas of high organic content, bacterial sulfate metabolism could itself cause eelgrass dieoffs.  This is natural and related to low oxygen levels in warm seawater.  Knowing the sulfide and ammonia (nitrogen) potential of organic composts is key to habitat quality for many species, including eelgrass – my view, T. Visel.

Appendix #1

The Impact of Organic Matter upon Blue Crab and Fisheries Habitat Quality
Ralph Vaccaro – Woods Hole Oceanographic Testimony 1981
The Mapping of Coastal Sapropels for Marine Chemistry
Timothy C. Visel
The Sound School, New Haven, CT

Ralph Vaccaro of Woods Hole Oceanographic Institution in 1981 gave a detailed explanation of the impacts of organic sludge to marine environments in Congressional testimony during a May 1981 hearing before a subcommittee of the then House Merchant Marine Fisheries Committee on Ocean Dumping – it is during this testimony Congress learned of the double impact of organic sludge – mostly sewage sludge, including the suffocation of the bottom and then the negative bio chemical impacts of glucose digestion in it (composting) to benthic organisms (See IMEP #15 Part II, posted April 2, 2014,  The Blue Crab Forum™ Fishing, Eeling and Oystering thread) Ralph Vaccaro – testimony (1981):

"The negative impacts from indiscriminate sludge release in near shore coastal waters include the accumulations of excessive concentrations of inorganic and organic nutrients (which diminish the quality of the local bio chemical tension) and unfavorable species diversity.  In extreme eases anoxic conditions develop, resulting in odiferous and toxic hydrogen sulfide evolutions.  Such conditions usually signify extensive damage to the benthic biota."
Ralph Vaccaro, Senior Scientist, Biology Dept. – Woods Hole Oceanographic Institution (1981) Testimony before Congress.

Did the members of Congress fully understand the scientific concepts and terms of the testimony?  That is left as an open question, but I have rewritten the testimony in a way I feel could be easier to understand in terms of blue crab habitat quality and our role in it.

My testimony is presented on the same topic area the impact of organic matter deposits in cove and bay bottoms.

Timothy C. Visel

The habitat destruction from placing organic composts (sludge) in the shallow fish/shellfish nursery areas can cause significant habitat damages far beyond suffocation.  The organic composts—natural or man-made—purge nutrients in chemical or biochemical forms (plant/animal matter).  In time, as the compost (sludge) is consumed by bacteria, it can emit nitrogen compounds (especially ammonia in high heat) that overwhelm the elemental oxygen bacterial reduction pathway and open the sulfur bacterial reduction process.  This can result in fish and shellfish die offs, especially in shallow waters as sulfides create toxic conditions too many oxygen dependent species.  In time, only the ones most tolerant of sulfide can live, such as primitive worms.  Eventually, sulfur rich compost called Sapropel begins to form.  In high heat, Sapropel conditions may release hydrogen sulfide into the air and water and create a sulfur smell similar to that of rotten eggs.  If occurring long enough, such Sulfur/Sapropel conditions can kill most oxygen dependent life forms, leaving a black/blue greasy wax deposit, devoid of most life forms on the bottom - T. Visel.

That testimony, in my view, is more understandable.

I offer these explanations:

Sentence #1:  "Indiscriminate sludge release."

Prevent loadings of organic matter—manure, human waste from sewage, leaves, forest debris and compost dumping can be sudden and random.

#1 "Excessive concentrations of inorganic and organic nutrients"

Inorganic nutrients are often described as those that do mostly not contain carbon and did not come from living tissue—(cellulose—sugars do contain living organisms carbon and are therefore organic.  Compounds that contain carbon are organic and consist of CHON, carbon, hydrogen, oxygen and nitrogen.

#1 "Quality of the local biochemical tension"
This refers to the ability to undergo chemical reactions—such as buffers and catalysts.  Established tension is a pathway or pattern that can be put out of balance and overwhelmed.

#1 "Unfavorable species diversity"

This is usually mentioned in context with habitat quality indicators or reference species.  The Saprobien System (1902) later was the foundation index upon which water and habitat quality indicators were developed using living organisms as reference (pollution) impacts to species.  It was Robert Lauterborn (1869-1952), a professor of forestry, who would build the foundation of all future biological indices.  Those streams described as free of pollution organic matter held many more organisms than polluted ones.  His research is known today as the "Saprobial System."

[Kolkwitz and Marsson (1909) further developed the index as the presence or absence of certain species based upon the purity of flowing stream water.  They were to define three Saprobic tones based upon the reduction of compost material—humus or the Saprobic System]

Sentence #2 "Anoxic conditions develop" (extreme conditions)

When it is very hot because of oxygen inverse solubility, warm or hot water naturally can hold less oxygen combined with glucose reduction (rotting compost); very low or no oxygen levels can be recorded. This is referred to as anoxic conditions in the scientific literature.

Sentence #3 "Odiferous and toxic hydrogen sulfide evolutions"

Sometimes I think science has been—"too polite" at times-in hot weather, organic matter will stink of hydrogen sulfide—a toxic substance to most oxygen dependent life.  This is the rotten egg smell (sulfide) mentioned so many times in the historical fisheries literature.  It can choke and in confined breathing spaces even kill us. Very few organisms can survive sulfide events and often formed the Blue Crab Jubilees in southern areas.

Sentence #5 "Extensive damage to the benthic biota"

The processes described above can and with the correct conditions, kill bottom dwellers. This is the dead bottoms or dead mud bottoms mentioned in the historical fisheries literature. Vaccaro (1965) found that dead decomposing organisms rapidly release ammonia, as a bacterial process of nitrogen metabolism toxic at low pH levels (Kinne, 1976).

All of these conditions can have negative habitat implications upon the quality and quantity of fish and blue crab habitats.  In fact, I would argue that these blue crab habitats are the ones most susceptible; they can warm up the fastest and being close to land (and yes our actions) can at times obtain sewage solids, leaves, twigs, bark and forest litter, going from a suitable habitat to unsuitable.  The blue crab jubilees, black water sulfide kills and cold water sulfide kills all have an organic compost bacterial connection. The Blue Crab Jubilees of Mobile Bay and other areas had a direct organic matter link and sulfate reduction (bacterial) process – what Dr. Vaccaro was describing was a jubilee for all species.

Of the above, I feel the most damaging is organic matter swept off land by tropical rains—they cause this "green" compost in warm weather in the areas most critical for nursery reproductive functions of most of our recreational and commercial fisheries. In many areas, this organic matter is delivered to shallow waters, key habitats for many species.  As sapropel increases, these habitats lose their nursery and grow out functions. I often give the terrestrial example of dumping several feet of leaves overnight on a lawn.  It may take two to three years for oxygen bacteria to fully break down this leaf matter. In the marine environment sulfate bacteria this could take decades. Many reports of the Chesapeake Bay mention the organic river of oatmeal (grouped up organic paste) as ruining formerly productive blue crab habitats.

Appendix #2

Bacterial Generation of Ammonia and Sulfide Compromises Toxicology Testing

April 17, 2015 Draft

DMMP Clarification Paper
Modifications to Ammonia and Sulfide Triggers for Purging and Reference Toxicant Testing for Marine Bioassays

Prepared by Laura Inouye (Ecology), Erika Hoffman (EPA) and David Fox (Corps) for the DMMP agencies.  Segments abstracted for content, T. Visel


The potential for ammonia and sulfides to complicate bioassay evaluations of dredged material has been addressed in the following DMMP clarification papers:

•   DMMP (1993) The Neanthes 20-day Bioassay – Requirements for Ammonia /Sulfides Monitoring and Initial Weight,
•   DMMP (2001) Reporting Ammonia LC50 data for Larval and Amphipod Bioassays,
•   DMMP (2002) Ammonia and Amphipod Toxicity Testing, and
•   DMMP (2004) Ammonia and Sulfide Guidance Relative to Neanthes Growth Bioassay.

In addition, the DMMP agencies drafted a clarification paper for the 2013 SMARM with guidelines for addressing potential non-treatment effects from ammonia and sulfides.  That paper elicited constructive comments from consultants and bioassay labs that resulted in the agencies postponing implementation of the guidelines until more work could be done.  Since then, the Corps of Engineers has had additional ammonia and sulfides testing done for four federal navigation projects.


Ammonia and sulfides are potential non-treatment factors that may affect the results of bioassays.  Despite the numerous clarification papers addressing these chemicals, there remain data gaps and inconsistencies in the existing guidance that limit the DMMP agencies' ability to adequately interpret the effects of these non-treatment factors or prevent them altogether.  Existing deficiencies in the DMMP guidance can be categorized as follows:

Threshold concentrations that would trigger purging and/or reference toxicant (Ref Tox) testing have been established for the amphipod and Neanthes bioassays, but nor for the larval test.

Hydrogen Sulfide:
Threshold concentrations that would trigger purging1 have been established for the Neanthes bioassay, but nor for the amphipod and larval bioassays.


In order to evaluate the validity of existing triggers and establish new triggers where missing, ammonia and sulfide toxicity data for standard test organisms were collected from published studies, poster presentations at various toxicological meetings, and reference toxicity studies from laboratories.  Data were expressed as endpoints including No Observable Effect Concentrations (NOECs), Lowest Observable Effect Concentrations (LOECs), and the concentration at which 50% of the population was impacted – exhibited as either abnormal development (effective concentration or EC50) or mortality (lethal concentration or LC50).  All collected data are presented in Appendix A for ammonia and Appendix B for sulfides.


Unionized Ammonia and Hydrogen Sulfide Triggers

The DMMP agencies propose using the lowest available NOEC as a trigger for purging bioassay containers prior testing.   Further, it is proposed that triggers be established for only the most toxic constituents – namely unionized ammonia and hydrogen sulfide – rather than for total ammonia and total sulfides.  For ammonia, half the NOEC is proposed as a trigger for Ref Tox testing.  The new and revised trigger concentrations are presented in Table 1.

Table 1.  Ref Tox and Purging Triggers for the various bioassays

Trigger   Bedded sediment tests   Larval tests
   Neanthes   Ampelisca   Eohaustorius   Rhepoxynius   Bivalve   Echinoderm
Unionized Ammonia (mg)/L Ref Tox   
Unionized Ammonia (mg)/L Purge   
Hydrogen Sulfide (mg/L) Purge   

The proposed triggers are expressed in terms of unionized ammonia and hydrogen sulfide.  Unionized ammonia and hydrogen sulfide concentrations must be derived from measurements of total ammonia and sulfides using test-specific pH, temperature and salinity measurements.

Purging methods:

For sediment toxicity testing, there are a variety of approaches used by regulatory agencies, project proponents and laboratories to purge samples.  Purging is most often performed either by replacing overlying water twice a day plus continuous aeration, or by aeration alone.  Once the unionized ammonia and/or hydrogen sulfide concentrations are below the trigger levels in Table 1 for all test samples (labs should use the minimum purging required to bring concentrations below the NOEC), the bioassay may be initiated.  Each batch of test sediments must have associated and similarly purged control and reference sediments.

If purging for the larval test is conducted by aeration alone, the test and water quality beakers are set up as they would be for the bioassay, but without the test organisms being introduced.  Aeration is applied until the ammonia/sulfides concentrations in the overlying water fall below the NOEC.

Ammonia and sulfides can continue to be generated in sediment during the bioassays themselves.  Therefore, if the water replacement method is used for purging, water exchanges may need to continue during the bioassay.  This may be done for bedded sediment bioassays in which exposure to porewater is a critical factor.  This includes the Neanthes test, and the amphipod test using Eohaustorius and Rhepoxynius.  Ampelisca would only require continued water exchanges if concentrations of ammonia or sulfides in the overlying water rise above the NOEC.  Continued water exchanges are not possible for the larval test.  Due to the small volume of sediment used for this bioassay, aeration alone will typically be sufficient to maintain ammonia/sulfides concentrations below the NOEC.

Ammonia and sulfides are more likely to be present in deeper sediments or sediments containing a significant fraction of organic material such as wood waste.  Therefore, the type of sediment being tested will need to be assessed to determine the likelihood for elevated ammonia and sulfides.  Initial bulk ammonia and sulfides testing by the analytical lab will also provide valuable information in this regard.

Appendix #3

Project Oceanology Session III, August 8 – August 26, 1988
Pine Island Bay Summer Marine Studies Program
Sediment Study


Coastal embayments have recently been experiencing increased pressure from human populations that are seeking to spend more time near or on the water.  As the popularity of boating has increased, the need to create more moorings and dockage has become acute.  The greater number or boats, combined with the increased value of each boat, has led to a need for more protection for these boats.  The construction of breakwaters is a common technique to create safe harbors.
In Pine Island Bay in Groton, Connecticut, just such a situation is occurring.  A five hundred foot long breakwater has been proposed to extend southward from Avery Point.  The breakwater would provide protection for moorings and slips already to the east.  By dredging the area immediately to the east of the breakwater, new dock space will be created.
   The construction of such structures must take into account alterations to other aspects of the environment that may occur as a result of the breakwater.  Breakwaters may alter current flow, change sedimentation rates and patterns, alter animal and vegetation distribution as well as reduce wave action.

Thaxter Tewksbury      Project Oceanology
Barbara Williams         Williams School
Seth Yarish            Project Oceanology


By Joshua Brewster


Pine Island Bay is an estuary located off Groton, Connecticut.  To the west there is a connection with Long Island Sound.  To the south there is a smaller opening to the water from Fishers Island Sound.  The Poquonnock River flows into the bay from the northeast.  A breakwater is planned to extend from the area near the Project Oceanology building out towards Pine Island approximately 500 feet.  The breakwater should protect the bay from large waves that flow into the bay during storms.  A study was done to investigate the organic content of the sediment in the bay before the breakwater is built.  The bay can later be studied after the breakwater is built.  At the end of this study, a prediction can be made as to the effect of the breakwater on organic content of sediment in the bay.
   The organic content of sediment indicates the amount of the remains of living organisms.  Other organic substances that often enter the water are sewage, oil, paper pulp, and other agricultural and industrial wastes.  On the average, 1% of the sediment is organic.  If the organic carbon concentration is unusually high (3.0% and up) or low (0.1% and below), it may be unsuitable for organisms to live there.  Therefore, organic concentration may affect the distribution of organisms.  The reason there may not be life where there is high organic carbon concentration in the sediments is that as aerobic and anaerobic bacteria decompose organic matter, a variety of by-products are produced.  Aerobic bacteria use the oxygen and release carbon dioxide (leaving no oxygen for animal life), while the anaerobic bacteria use sulfate and release hydrogen sulfide during the decomposition of organic matter. Thus, there is likely to be low or zero oxygen concentrations and high concentrations of hydrogen sulfide or other toxic materials present in the sediment.  The reason life is unable to live where the organic carbon is low is that organisms live off of organic material on the bottom and it would be difficult for them to feed in an area where the percentage of organic carbon is low.     
   Sediment is one of the main habitats of life in the bay.  If a breakwater is built, it may affect the currents in the bay, and since the currents move sediment the environment may be totally changed.  This investigation will look at the sediments prior to the construction of the breakwater so that it may be studied     
after it is built.


   Sediment samples were collected along eight transect lines in Pine Island Bay.  The transect lines ran north and south every 100 meters.  Samples were collected every 200 feet along the transect lines.  The distances were measured with a marked fishing line.  Samples were collected with clam tongs in deep water.  Where the water was more shallow, the samples were collected by hand from a quarter meter square quadrat.  The samples were then placed in labeled plastic bags.  The samples were then brought back to the lab.
   In the lab, the samples were placed in labeled tinfoil boats.  The boats were placed into a drying oven at approximately 100 degrees Celsius for two to five hours.  After the samples were dry, as close to 10 grams as possible of each sediment sample, was placed in preweighed crucibles.  The crucibles were then put in a combustion furnace at 500-600 degrees Celsius for two to three hours.  The samples were baked in the combustion furnace to burn off all of the organics.  After the samples were combusted, they were reweighed.  The weight of the sediment after combustion was subtracted from the weight before combustion to determine the amount of organic carbon in the sample.  This number was then multiplied by ten to determine the percentage of organic carbon in each sediment sample.  For more detailed instructions, see "Investigating the Marine Environment: A Sourcebook," Vol. 2, pp. 431-434.


   The organic carbon content of the sediment in Pine Island Bay ranged from 0.1 to 7.5%.  Of the 66 stations sampled, 18 had 1.1 to 2% organic carbon (see figure 1).  This was the most frequent percentage of organic carbon found in bay sediments.   Fourteen stations had between 2.1 and 3% organic carbon.  This is the second most frequent.  These were followed by 5% and up and 3.1 to 4% organic carbon with 14 and 13 stations respectively.  0 to 1% organic carbon found at 8 stations.  The least frequent organic carbon percentage found was 4.1 to 5%, found at 4 stations.  In a few of the samples, there was visible vegetation, which would have raised the percent of organic carbon.


   It was found that the majority of the bay sediments had an organic carbon percentage between 1.1 and 3.  This means that the bay sediments have an average to above average percentage of organic carbon.  At numerous stations, there were abnormally high amounts of organic carbon, between 4.1% and up.  But that is most likely because there were visible amounts of vegetation in the sediment samples.  A few stations with rocky and/or coarse sand had a low (0 to 1) percentage of organic carbon.  The organics are not able to stick to the rocks or sand and, therefore, they are able to be washed away with the slightest current.  Strong currents tend not to allow the particles to settle.  Where the current is weaker, the organics settle there, producing an area with high percentages of organic carbon.  When the breakwater is built, the currents could change, and that may change the organic carbon of the sediment in Pine Island Bay.

Appendix #4

Canada Geese Contaminate Water Supplies on Cape Cod – 1981
Journal of Field Ornithology
Summer 1981, Vol. 52, No. 3
Pg. 240-241

Canada Goose Feeding Damages Shellfish Beds. – During the fall of 1976, the Massachusetts Shellfish Officers Association (MSOA) lodged a complaint with the Division of Fisheries and Wildlife that Canada Geese (Branta canadensis) were feeding on soft shelled clams (Mya arenaria).  A review of the literature revealed no reports of Canada Geese ingesting shellfish.  A questionnaire prepared by Burke Limeburner, President of MSOA was distributed in 1977 at the MSOA convention.  Officers from 11 towns indicated they had "major problems" with geese on shellfish beds, 4 indicated "minor problems," and 8 had no problems.  I contacted several of the officers reporting major problems.  Officers differed in their views of when depredations on clam beds were greatest.  Some felt the problem occurred during the summer when seed clams were small enough to be ingested by geese, while others felt that winter was the worst time when wintering populations of geese were greatest and other food sources limited.

. . .

No further field observations were made until January 1980 when I observed Canada Geese feeding over clam beds and performing the puddling actions described by Shellfish Officers.  The geese, however, appeared to be feeding on grasses inundated by the high tide.

. . .

While I find no evidence to support MSOA allegations that Canada Geese were ingesting shellfish, it did become apparent to me that the feeding activities of geese over soft shelled and quahog (Mercenaria mercenaria) clam beds were detrimental to shellfisheries.  Puddling by geese dredged up seed clams, exposing them to the elements and to predation by other animals know to eat shellfish, including waterfowl.  The large size of the geese allowed them to create deeper depressions than Black Ducks and Mallards and expose larger shellfish.  During aerial inventories, I observed that the cratering effect on areas where geese fed over clam beds was both intensive and extensive.
The Canada Goose was not a common nester in Massachusetts until the mid-1940's (Griscom and Snyder, The Birds of Massachusetts, Peabody Museum, Salem, Mass., 1955).  When the use of live decoys was outlawed in 1935, geese kept for this purpose were released to the wild (Blandin and Heusmann, Trans. N. E. Sect. Wildl. Soc. 31:83-100, 1974).  Since that time, breeding flocks have increased in both size and numbers.  Wintering geese have increased from 3000-4000 birds in the mid-1940's to 10,000-14,000 in recent years.  This increase has amplified problems of goose grazing on crops, golf courses, and private lawns, fouling beaches, contaminating water supplies, and now, damaging shellfish beds.  While it became apparent that Canada Geese have a detrimental effect on soft shell clam beds, the economic impact was not measured by this study.

. . .

This study was a contribution of Massachusetts Federal Aid in Wildlife Restoration Project W-42-R. –H. W. HEUSMANN, Massachusetts Division of Fisheries and Wildlife, Westboro, MA 01581.  Received 10 October 1980, accepted 28 May 1981.   

Appendix #5

Middletown Looks to Prevent Blue-Green Algae and Control Geese at Crystal Lake
The Middletown Press
March 6, 2024

Middletown – "The city is trying to remedy blue-green blooms at Crystal Lake as well as deter the geese that nest there, and whose droppings contaminate the water with E. coli bacteria, closing the water to swimming.  The State Department of Energy and Environmental Protection Bureau of Natural Resources awarded the city $14,250 to fund a diagnostic feasibility study of the 32-acre water body on Livingston Road used for swimming, boating and fishing.

The money will be used by the Middletown Public Works Department to develop strategies to manage harmful algal blooms known as cyanobacteria, as well as identify what species are in the water.

Higher than normal E. coli bacteria levels prompted the city to close the water to swimmers for about two weeks late last summer.  At one point, tests found the presence of bacteria ten times above the safety threshold.  Canada geese feces contain nutrients that encourage such algal growth.  These droppings have limiting levels of nitrogen and phosphorus.