CTFishTalk.com: Oxygen & Sulfur Reducing Bacteria Questions #10 - Tim Vi - Connecticut Saltwater Reports ( CT Saltwater Reports ) - A Community Built for Connecticut Fisherman.

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Oxygen and Sulfur Reducing Bacteria Questions

CT Fish Talk™ Environmental Conservation #10
When It Came To Fish and Shellfish Did We Take Out
The Wrong Nitrogen

Did We Remove The Correct Nitrogen Compounds In The High Heat –
Low Energy Conditions

The Role of Eelgrass in the Formation of Sapropel

Ammonia Filter Systems for the Aquaculture Industry Require Bacteria
Tim Visel, The Sound School*

[The views expressed here do not reflect the Citizens Advisory Committee nor Habitat Working Group of the EPA Long Island Sound Study. As of November 2015 The Long Island Sound Study contains eelgrass nitrogen policies that differ from my personal viewpoint. The viewpoint expressed here is the viewpoint of Tim Visel.]

60 South Water Street
New Haven, CT 06519
Questions about Eelgrass – Nitrogen Research

Preface -

Students considering this as a Capstone proposal topics should read The Cycle of Eelgrass, Do We Have the Correct Scallop Grass and The Trouble with Eelgrass reports for fish and shellfish habitat quality information – Each report discusses shallow water glucose metabolism in high organic low oxygen environments

Did We Take Out the Wrong Nitrogen?
ASTE CTE Standards – Aquaculture A-4 A-5 A- 6 Describe how the biofilter of a recirculating system converts ammonia to nitrite, and nitrite to nitrate.

Every salt water or fresh water aquarium owner knows about the sulfur cycle or what happens when organic matter builds up in a small system environment. It can foster an ammonia level rise, toxic to most sea and aquarium life. Ammonia is very toxic to fish and an entire industry has evolved about aquarium filter systems to remove it. In heat, filter systems fail faster, organic matter turns black and the smell of sulfur can make any fish aquarium owner cringe. Heat, uneaten food and fish waste are constant concerns. What about larger systems? That was a question asked me in 2004 after a multiple exercise page about nitrogen/ammonia filter systems during a classroom discussion about the nitrogen cycle.

In 2004, I returned to the classroom to fill in for an aquaculture science teacher who had suddenly become very ill. It had been a decade since I had an aquaculture science class (Bridgeport) but after a few days had developed a series of laboratory practicals – the foundation of agriculture education. One exercise was titled #11 “The Nitrogen Cycle in a Closed Aquaculture System” which talked about Water Quality Monitoring” – and the importance of nitrite and nitrate fixing bacteria in the filter systems (Readers might want to review a Blue Crab Forum™ Environment and Conservation post titled “Natural Nitrogen Bacteria Filter Systems” October 30, 2015).

At the end of the exercise was a performance measure aligned to a standard that asked about the reduction of ammonia from bacterial use of nitrites and nitrates (bacterial action) in the filter pillow – then one of the students asked about natures filters and the presence of nitrate and what if we removed them, what was the result – it was a great question and one in a related way I heard before – in 1982 when I attended meetings at the Hyannis Waste Water treatment facility on Cape Cod. In one less than cordial meeting regarding the facility, (the filter beds in heat we generating noxious fumes) one plant operator exclaimed something like ”take the solids but leave us the nitrate” and again “we need all the nitrate to keep our filters alive and operable in this heat”. It was hot and very dry on the Cape during this period the class discussion then turned to Connecticut’s program to remove nitrogen compounds including nitrate – what was the impact upon that with Long Island Sound’s natural filter systems? I couldn’t answer the question and within a year I was back on the EPA Long Island Sound Study – If nitrate was important to waste water treatment facilities and small filter systems what about a much larger one?

Environment and Conservation – The Blue Crab Forum™ - Bacteria Nitrogen Series

I want to thank the Blue Crab Forum for allowing me to post in a new thread – Environment and Conservation and also Connecticut Fish Talk for reposting these reports. This is my tenth report about bacteria and nitrogen cycles. Coastal habitats once praised for valuable habitat services are impacted by bacteria and at times become nature’s killing fields, eliminating critical nursery and spawning grounds for many inshore fish and shellfish species. Coastal fishers often observe these events, mats of bottom bacteria, chocolate or purple waters, brown tides, blue crab jubilees or just fish kills. Beyond these public events bacteria and nitrogen change the habitat qualities that we recognize today as “good” onto something that is “bad” for inshore fish and shellfishing. Out of sight and rarely discussed, these conflicting bacteria strains have important implications for estuarine health and seafood production worldwide.

#10 Oxygen and Sulfur Reducing Bacteria Questions

#9 Nitrogen and Eelgrass Habitat Questions 11/18/2015

#8 Natural Nitrogen Bacteria Filter Systems 10/20/2015

#7 Salt Marshes a Climate Bacterial Battlefield 9/10/2015

#6 Bacteria Disease and Warm Water Concerns 7/23/2015

#5 Nitrogen, Inshore Habitats and Climate Change 1/12/2015

#4 Black Mayonnaise Impacts to Blue Crabs and Oysters 1972 to Present
10/16/2014

#3 A Caution Regarding Black Mayonnaise Habitats 10/2/2014

#2 Black Mayonnaise, Leaves and Blue Crab Habitats 9/30/2014

#1 What About Sapropel and the Conowingo Dam? 9/29/14

Fishers should follow this bacterial conflict as more and more information comes in regarding habitat quality and important recreational fisheries such as striped bass, winter flounder and blue crabs or lobster habitats are subject to bacterial impacts. It is also important that shallow water fishers be aware that sulfur bacteria contain a series of antibiotic resistant strains first identified in Contaminate Effects On Biota of the New York Bight by Joel, O’Connor, NOAA (1976). Soft organics with bacteria do pose risks to fishers and bathers – coastal bacteria benthic monitoring programs are needed. – My View.

As additional habitat information comes in from Europe a clearer picture of what a warming climate can do to fisheries is evolving. While most of the fisheries research here has occurred in deeper waters – fish and offshore grounds and off continental shelves, however most of the sharpest negative habitat conditions happen in areas that are shallow, ten feet or less. Here the impact of warmer temperatures can occur quicker and the increase of energy is much more noticeable. This is the site of our numerous inshore bay and cove fisheries. It is the ten feet or less habitats, the marshes, coves and shallow bays that give us a look of what warming can do to fisheries habitat quality and those with and without oxygen, and at different energy levels (storm activity) over time.

For example in New England a warming period can shift species range and we have seen “southern” fishes move north while a return to colder conditions northern species move south – many times. Oxygen levels also are subject to rapid change in the shallows, colder conditions result in “saturation” an older term that denotes much greater “available” oxygen levels in water. While warmer waters contain less oxygen and they can at times become devoid of free of elemental oxygen as many areas of Long Island Sound experienced in the 1980s and 1990s. This was called hypoxia a condition of low or no oxygen which in these climate changes. Even harmful algal blooms have occurred here many times before and Dr. Scott Nixon (URI) has written extensive accounts of past algal blooms especially the one that occurred in 1898 in Narragansett Bay. Red tide cysts have been found in Mumford Core CT under several meters of Sapropel – once thought to be the remains of red tide blooms centuries ago.

As most fish and shellfish require elemental oxygen (as we do) a decline in oxygen is “bad” for fish and shellfish which it is. We can see this impact, dead fish, dead oysters and a very different species profile. But warm water can be productive as well, the bays and sounds in southern states support significant inshore fisheries they are on average warmer than ours – the difference is energy and the presence of organic matter on the bottom (more marshes and less leaves). Energy (wave and currents) tend to keep organics in motion and recycling back to minerals by “filter” bacteria that quite simply eat it. Remove the energy (as many habitat histories in New England around inlets and bays mention) and fishes habitat conditions can change rapidly – increase the heat and oxygen levels drop (that is a natural solubility law) naturally, dump large amounts of organic matter into the water and very shortly you will have a “smelly compost,” similar to those on land even if it is below the water.

This “smelly compost” does smell in sub tidal habitats – it purges ammonia and sulfides the by production of bacterial reduction and fish or crabs avoid these areas, they can “smell it” – mostly likely the most known of these toxic results are the “Blue Crab Jubilees” when toxic sulfides get so high “blue crabs pick land over sea.” That happened in Niantic Bay a few years ago. It is during these sulfide events that coastal residents mention the “the smell of rotting eggs” most prevalent during the 1880-1920 hot period in New England. When this occurs one type of “filter bacteria” die and another type emerged. This type is not the beneficial bacteria filter species that so many aquarium owners recognize a second group that literally feeds off the flesh of those that proceeded them – the sulfur and sulfate reducing bacteria – the signs of dying salt water system, the smell of sulfur. Most of the sulfide and ammonia comes from sulfur bacteria that can live in these hot low oxygen conditions, they are commonly termed sulfur reducing bacteria or SRB. These bacteria are “slower” than those who need oxygen and when large amounts of organic debris is swept in they cannot keep up. When oxygen is low these bacteria can utilize sulfate as an oxygen source and ammonia levels that can then soar. Sulfate in high salinity marine waters is abundant and often termed not limiting” that means there is plenty of it. For these bacteria in shallow marine habitats, there can be no oxygen shortage.

One of the signs that bacterial habitats are changing or how it is occurring is the buildup of organic matter in low oxygen conditions – it accumulates and putrefies – in times becoming Sapropel which as part of the bacterial reduction process sheds toxic ammonia. Organic matter changes habitats by direct suffocation (burial) but also by sulfur bacterial reduction. The Indian River lagoon estuary program (Florida) has been one of the first programs to zero in on this as ambient ammonia levels that have reached greater than 50% - and organic matter has built up to many feet in slow poorly flushed areas which now purges toxics and feeds toxic algal strains that now feast upon ammonia. After all the first commercial ammonia plants simply produced it by heating organic matter in low oxygen conditions. This generation of ammonia from organic matter in the marine environment has been known since the 1930s.

Sapropel forms first under conditions that favor sulfur bacterial reduction – low energy warm temperatures, and ample organic matter. That is why winter flounder fishers first noticed the build up behind eastern Connecticut tidal restrictions such as railroad crossings. Mostly railroad causeways that reduced energy and oxygen availability by slowing tidal flows. As the climate cycle changed sapropel formed here first. As energy lessened in a positive NAO climate cycle – warming waters soon favored sulfur reducing bacterial and sapropel built up. Previously hard pebble and sand bottoms now became “foul” and muck covered – at night when element oxygen levels are at a low point they would smell of sulfur. In time six inches of dead leaves turned into a foot – then many feet of this sapropel gathered over time in dredged channels and the quiet backwaters of poorly flushed coves. These were areas that we also the “nursery habitats” of important inshore fisheries, striped bass, winter flounder, for example became putrefied and deadly to larval forms. These critical shallow habitats “failed” and reproduce year classes declined – fishery catches soon declined. The winter flounder fishers correctly called this habitat change in many eastern Connecticut coves bisected by railroad restrictions decades ago, but no one unfortunately listened to them.

Dr. Donald Rhoads, Chairperson of Yale’s Geology Dept, summed it up for Long Island Sound workshop participants in a published seminar proceedings, produced by NOAA under contact by the EPA – (1985) mentioning changing profiles – habitat compression (referring to a similar soar then crash in blue crab productivity) highlights a large habitat shift, climate induced and connected to energy levels – occurs just before a habitat crash. A compression of species can occur as diminished aerobic habitat space intensifies competition – for space and food, increasing populations such as benthic foragers such as crustaceans (crabs and lobsters) in a smaller area. When this happens fishers may begin to catch higher amounts of them (crabs and lobsters) as catches go up – (increasing catch per unit effort). In other words as low oxygen conditions to spread into the sides of the basin (shallow water habitats) from Sapropels just before a population crash – such lobster catches may in fact soar – which followed precisely the catches of CT lobsters a decade later. (See page 56 The Benthic Ecosystem – Dr. Rhoads Department of Geology and Geophysics Yale University from a 1985 Long Island Sound Estuary of the Month Proceedings in which Dr. Rhoads mentions that measured dissolved oxygen is not adequate but urged mapping the distribution of Sapropels instead). Despite this 1985 caution about Sapropel monitoring - no Sapropel studies (maps) were conducted.

Early researchers also detected higher oxygen levels immediately above Long Island Sound “sediment” interfaces – highlighting the importance of sulfate digestion (glucose metabolism) in Long Island Sound Sediments. As oxygen dependent bacteria died off – sulfate reducers did not need it and higher bottom oxygen levels here were actually very bad habitat signs, showing a bacterial “war” in progress that sulfate reducers had “won” then they simply did not need it – elemental oxygen as sulfate can be the oxygen source for these bacteria and is plentiful in sea water, salinity, temperature and organic matter were three important elements in the rise of sapropel – a sulfide rich organic compost that would drive habitat compression and the expansion of some shellfish and finfish species followed by a dramatic collapse.

In fact some early Long Island Sound researchers were concerned about sapropel and the importance of the biochemical reactions in them – Dr. Rhoads in 1985 urged mapping Sapropels as an indicator of low oxygen conditions. However, Dr. Barbara Welsh at the same conference discussed the “short” nitrogen/carbon cycle decomposition rates are very short pg 65 and a larger pathway that showed accumulations as “fluff” on the bottom pg 66.

From the NOAA 1985 Estuary of Month Seminar Battelle contract #68-03-3319 (Victoria Gibson and Michael S. Connor for the U.S. Environmental Protection Agency Office of Marine and Estuary Protection Washington, DC January 15, 1986 (pg 148) has this section, in which Dr. Rhodes draws attention to Sapropel.

“Dr. Rhoads: One reason I mentioned the importance of the sapropels these black iron monosulfide muds on the bottom – was the direct point that Peter raised (Dr. P. K. Weyl Marine Sciences Research Center – State University of New York). The system is so dynamic that to measure the change from year to year in dissolved oxygen as measured in the water column would take more money then we have. It’s not practical at all.

Given that kind of variability, what you need is a low pass filter and an integrator, and that’s the sediment. I suggest that a very sensitive index of the waxing and warning of this condition would be the map of where the Sapropels terminate, whatever isobaths that might be follow the edge of those Sapropels. If they’re encroaching upwards into the shallow water, it’s getting worse. If they’re receding, it’s getting better.”

It would be the shellfishers, then winter flounder fishers who would first notice the increase of Sapropel – commonly termed “black mayonnaise.” In time the continued mild and then hot weather would cause Sapropels to grow deeper and in fact spread into the shallows. By 1995 it (Sapropel) would become a dominate habitat type in many New England small coves and bays. (IMEP #14, The Rise of Sapropel the Fall of Bay Scallops, March 2014 – Blue Crab Forum™ fishing, eeling oystering thread. This report on Sapropel and Bay Scallops has been one of the most viewed of all the IMEP habitat newsletters T. Visel).

It is Sediment or Soil?

Sediment – In several reports I urge caution around the term sediment and suggest “soil” instead as soil can contain living bacteria. Early Long Island Sound Studies Environmental Baselines in Long Island Sound 1972-1973, Informal Report No. 42 Ecosystem Investigation – December 1974 described geological parameters of sediments merely as geological terms such as;

“Weathering and Erosion – (grain sizes) contamination (heavy metals) and the presence microorganisms – meiofauna 5 centimeters deep cores, macrofauna (grab samples). The study of soil organisms (bacteria) or soil biochemical interactions were not included – an absence of soil science. Here the condition of saprotrophic – the eating of dead organic matter (Principles of Terrestrial Ecosystem Ecology – Chapin et al 2001) came from the discussions of Saprobien System (during a hot climate period) of organic matter digestion and the term Sapropel itself absent from many studies (see Saprobien System, Kollowitz and Marsson 1909).

{The continued exclusion of Sapropel formation (marine humus) and the absence of ammonia/sulfide purging from them is a form of science research misconduct/bias – an emphasis that appears to shift blame or responsibility for seafood increases or decreases to just human nitrogen inputs – my view, T. Visel}.

The large question is how bacterial changes respond to climate conditions in hot water sulfur reducing bacterial are just fine they don’t need “elemental oxygen” they get it from sulfate an oxygen source that is not limiting in sea water and they have plenty of it. They are not impacted by heat – in fact they thrive in it as the oxygen requiring bacteria die off. These bacterial strains that use sulfate are the remains of the sulfur cycle – when sulfur life forms dominated the world in a hot climate period. Sulfur reducing bacteria are always present at low levels – waiting for conditions that favor them – again, such when climate conditions favor them – those long hot periods that contain few storms.

When the oxygen requiring bacteria (the good bacteria) die off and replaced by sulfur reducing bacteria that use sulfate these once positive shallow habitats turn into natures killing zones – wiping out year classes and egg/larval forms as well. Striped Bass fisheries know what happened when they “loose” several year classes in a row – it is devastating. The byproducts of sulfate reduction are deadly – sulfide which is highly toxic, ammonia toxic itself and which now fuels harmful algal blooms which themselves produce additional toxins. It at the end is a sulfur cycle that creates a clean sweep of elemental oxygen requiring life forms – the dead zones found close to shore and supplied with excess organics from land in rivers (the most familiar natural zone is the “Dead Zone” at the mouth of Mississippi River). When elemental oxygen levels go down sulfate reduction goes up and the dead zones increase – colder water (containing more elemental oxygen and energy storms can break this sulfur cycle introducing oxygen to rebuild nature’s oxygen bacterial filter systems – but it takes time. Bacteria populations need to rebuild and it can be such a slow process and hard to document in large systems. That is why it is important to look at small systems and all the available sources of oxygen – not just elemental. Those are the shallow coves and bays that is where most of the sulfate/ammonia exchange takes place in organics now termed glucose metabolism. That is where relatively quick habitat changes can be measured as represented by winter flounder fishers observations in the 1980s as firm bottoms ones that once contained soft shell clams become soft and deep suffocating the shellfish and become void of winter flounder. People could notice the sulfur reduction of organic matter as well.

When I was employed by the University of Massachusetts the Hyannis Wastewater Treatment Plant had serious problems. It was hot then on the Cape – 1981-83 and low rainfall – it was hot and dry.

The smell of sulfide (and ammonia) coming off the Hyannis Treatment facility aeration fields was so intense it was causing people to abandon nearby backyards. (I was to witness these events). The topic of one meeting was nitrate to them was a second source oxygen compound that bacterial filters needed to live or the sulfur and ammonia smells would become worse. To keep them alive they needed the nitrate. That did not seem strange at the time, having graduated from the University of Rhode Island – I was exposed to the first indoor large scale filter systems for salmon. We used bacteria to control ammonia – the compound of great concern as it is highly toxic, and had inoculated filter systems with marine mud in seawater systems using oyster shell as a bacteria bio film surface (Conservation and Environmental thread Blue Crab Forum #6 Bacteria, Disease and Warm Water Concerns – July 2015) we used a mud gathered at low tide to inoculate the filter system feeding it organic matter, to start the bacterial processes. Today most of the recirculation aquaculture industry has gone to a plastic bio pac media – commonly called bead filters – here bacterial films convert ammonia into less toxic forms of nitrite and nitrate – a key feature being dissolved oxygen. The bottom line we needed those bacteria to stay alive to keep ammonia levels low – nature it seems does that as well when it is cold – only here the filter are huge areas of cove and bay bottoms.

In a Rhode Island Sea Grant fact sheet Pg 463- RIU-G-97-003 by Scott Beatty “Bio Filters for Recirculating Aquaculture Systems”, mentions the problem of excess organics –

“Bio filters generally do not filter out sold matter, suspended or otherwise from the water. Furthermore bio filters are known as nitrification filters. This means that the removal of ammonia results in the generation of nitrate.”

For most aquarium owners the organic matter build up in low oxygen conditions is a black layer in bottom sands or gravel. If oxygen levels drop the smell of sulfur will result – no different than a miniature blue crab jubilee of Mobile Bay. This is especially noticeable in sea water systems in heat until all the sulfate is utilizes but in coves and bays the supply of sulfate is refreshed twice a day by tides here sulfate reduction could purge ammonia in high heat – deadly to fish and shellfish.

One of the best examples and one that I find most easy to read (many current papers on this topic spend more effort in defining complex language than the topic itself - my view) was a March 1987 newsletter from The Texas A and M Sea Grant College program “Marine Education” Vol 7, No. 3 March 1987. The article by Gil Naizer and Randy Cooper describes the nitrogen cycle in the filter system itself,

“The nitrogen cycle consists of three processes – ammonifation, nitrification and denitrification. Ammonification is the breakdown of organic nitrogen (such as leaves – T. Visel) waste (also known was manure) into toxic ammonia by heterortroplic bacteria (sulfur and sulfate reducers – T. Visel). These bacteria will be the first to develop in a new (unconditioned) – (bacterial free – T. Visel) aquarium. (This is the first step in which to start marine filters we would add “marine mud” rich in several types of bacteria – T. Visel). The feed on waste products (organics T. Visel) as they accumulate, and multiply on gravel surfaces and tank walls. The ammonia resulting from decomposition of organic compounds provides food for another group of bacteria.”

This process describes the role of bacteria in the nitrogen cycle – add heat to lower dissolved oxygen levels and “filters” fail faster even in bays and coves. That is how natures bacterial filters changed in Long Island Sound as it became hotter the bacteria that need oxygen and nitrate died off as sulfate reduction of organic matter caused ammonia levels to soar. (These rapid increases in ammonia is now linked to the rise of harmful algal blooms called HABS).

By removing nitrate we only added to the “oxygen shortage” in high heat we made a negative condition only worse – this is being confirmed as more studies investigate nitrate buffering of glucose metabolism.

Some of the best information about the toxicity of sulfide and the buffering impact of nitrate organic digestion is coming from Florida and Tampa Bay. Cellulose digestion of leaf material feeds sulfate reducing bacteria – it is “sugar” that feeds this strain. Although wastewater treatment operators have long known about the oxygen buffering capacity of nitrate recent studies from Florida provide a great insight about what is happening in marine soils.

It is in these marine soils that much information can be obtained the bacterial processes in them and provide a window into the climate change and fisheries discussion. When it came to waging war upon nitrogen we removed oxygen as well – the nitrite and nitrate compounds that have been so much the focus of “nitrogen” removal. The problem is with them we removed oxygen attached to nitrogen opening the door to ammonia generation from organic matter. To starve sulfate reducing bacteria the ones that are most dangerous to seafood (sulfate is not limiting in seawater) organic matter reduction – not nitrogen is the key. By removing nitrite and nitrate we just it appears caused more ammonia generation far more deadly to fish and shellfish. We may have made a bad climate condition only worse – instead of concentrating on toxic ammonia we removed those nitrogen compounds that contained oxygen as well. As we continue to examine sulfate reduction we need to look at the role of submerged aquatic vegetation in the process – eelgrass ability to start sapropel and sea lettuce that thrives in warm ammonia rich regions that purged from sapropel. Not only is glucose metabolism connected to submerged aquatic vegetation - such vegetation mats may add to the toxic problem when nitrate and nitrate compounds were removed.

In chapter five of a New York State Department of Environmental Conservation (DEC) New York State Federation of Lake Associations, Inc. Report, titled “Fisheries Management, Matching Expectations to Reality“ from Diet for a Small Lake, second edition 2009, the habitat limitations of ammonia generation and sulfide purging are discussed. The higher ammonia levels in heat on pg 98 “Ammonia is toxic to fish and other aquatic organisms. The amount of ammonia in the (ionized) toxic form NH3 is greater at higher temperatures and pH” and further – “Hydrogen sulfide is very toxic to aquatic organisms and continuous to levels as low as .002 ppm (parts per million) – Hydrogen sulfide is more toxic at low temperatures and pH.” And pg 111 “winter – kills” are massive die offs that occur periodically in many small lakes – when thick ice and snow prevent light from reaching underwater plants they stop producing oxygen.” This is a cooperative New York DEC publication- New York State Federation of Lake Associations, Inc. 2009.

This is how ammonia levels spike in August in shallow bays (and Brown Algal HABS) and cold long winters can produce sulfide winter kills on ice covered embayments (Megalops Special Report #1 Blue Crab Winter Kill, June 15, 2015 Northeast Crabbing Resources Blue Crab Forum™). Extremely cold winters can kill fish with sulfide – hot weather can cause ammonia levels to soar to toxic levels but sulfate reduction – the metabolism of glucose by bacteria can cause both to happen quicker and that relationship is linked to particulate organic matter POM – temperature and energy. The greatest immediate habitat quality factors are the sediments themselves which should be classified as soil and under the correct biologically processes now as Sapropel – my view.

I respond to all emails at tim.visel@new-haven.k12.ct.us. I always welcome comments and suggestions.

This report section combines a second nitrogen warning from The Sound School – Dec. 2014 – Abbe Smith, Memorandum November 18, 2014 and the following reports,
Does the Long Island Sound TMDL Need an Immediate Review for Bentic flux and Sapropel formation – ammonia generation? (2011)
Questions About Nitrogen Programs and Sapropel formation – Dec 2012
Nitrogen/Eelgrass TMDL Levels and eelgrass research needs immediate review for high heat Sapropel formation and toxic sulfide purging related to habitat succession (2013).
Similar Comments provided to The Long Island Sound Study CCMP revision concerns in October 2014 - The Nitrogen Problem – The Oxygen/Nitrate – Sulfate Ammonia Pathways in the TMDL process. (See 2004 Aquaculture Science and Natural Resources Class notes #11 filter sytems).

- Bacteria Natures Nitrogen Filters -

Last fall (2013) The Sound School issued a second caution around our Long Island Sound nitrogen TMDL – total maximum daily limit. (The first research caution in 2012). This report is the third nitrogen caution as it relates to seafood abundance. Nitrogen pollution had been identified as the largest constraint to shellfish and finfish abundance including the overall health of Long Island Sound in general. That position and similar ones are now being examined by estuary programs nationwide. I have been part of the Long Island Sound Study representing Sound School since 2005 (I had been previously on the EPA/DEP Long Island Sound study before 1986 – 1990) and now serve on the Habitat and Citizens Advisory sub committees. (These viewpoints represented here are the viewpoint of Tim Visel not the EPA Long Island Sound Study or sub committees).
As part of the Citizens Advisory Committee (CAC) our purview was to bring forward different points of view or perspectives with needs and concerns and one that the study should respond to including a need (from me) for a much longer term historical fisheries/habitat viewpoint. (T. Visel multiple proposals). Unfortunately a long term environmental fisheries history did not occur although a long term habitat view is frequently termed the law of habitat (historical) succession, that aspect has been missing from many nitrogen research projects. Fisheries history concerns expanded into eelgrass and nitrogen reviews in 2006 – also containing needs to review previous habitat and water quality studies.
Research from Europe and now the west coast is also looking at long term habitat perspectives and living marine resource abundance in terms of benthic flux – the high heat low energy Sapropel shedding of ammonia and the purging of toxic sulfide compounds.

The term organic nitrogen or hard nitrogen (nitrogen compounds bound in hard wood or leaf tissue) is currently not measured (instruments cannot measure it) leaving many questions as to impacts upon estuarine habitat quality and life processes of benthic organic matter (leaves in northern areas, manure in the southern areas) in a warming climate. Questions about connecting nitrogen removal to increasing seafood species however remain especially when not connected to temperature or climate cycles. Connecticut’s rebuilt forest canopy now estimated at 78% is dramatically higher than its dairy golden days in the 1880s when agriculture clearly had reduced forest coverage below 30%. The increase in leaves on estuaries bottoms has increased substantially. (A regional leaf burning ban 1972-74 should also be examined for increasing organic inputs). This leaf fall contains a phosphate flush and nitrogen compounds as particulate organic matter termed “POM.” Many estuaries are also looking at Sapropel deposits behind coastal dams, or restricted transportation crossings.

The early Long Island Sound Study participants however were informed about the significance of particulate organic matter (POM) and nitrogen second source generation now termed as “benthic flux” or Sapropel formation. Water quality projects that once combined storm water into municipal wastewater plants were discontinued and efforts to separate such discharges isolated a huge source of organic or hard nitrogen sources in storm water run off (organic matter leaves on streets). As Connecticut’s forest canopy increased from agricultural fields to woods the amounts of hard organic nitrogen “Duff” (leaf material) then carried into estuaries soared. The increase in organic matter was not included (as it was not measurable) as part of a point source nitrogen waste input. During the nitrogen TMDL discussion process this issue was brought forward by Waste Water Treatment Plant operators who voiced similar concerns as in this example below clearly illustrates.

Response to Public Comments on the Long Island Sound Draft Total Maximum Daily Load Analysis
To Achieve Water Quality Standards for Dissolved Oxygen in Long Island Sound
December 2000
Prepared by Connecticut Department of Environmental Protection
Bureau of Water Management, 79 Elm Street, Hartford, CT 06106-5127

XV. Individual Plan WLA concerns {Comments abstracted from a much longer report}
85. Bristol: “The plant expansion should provide for adequate removal of nitrogen species such as ammonia and nitrate but this upgrade will not specifically remove organic nitrogen from the wastestream. We realized that a percentage of organic nitrogen will be chemically converted to ammonia by hydrolysis and biologically converted to ammonia through ammonification in aerobic or anoxic zones but how much of the organic nitrogen can be removed? We understand a strategy employed for the treatment of residual nitrate such as varying recycle flows might enhance organic nitrogen removal but to what extent? We also know that there will be a certain soluble fraction of Total Kjeldahl Nitrogen that is not biodegradable and therefore can never be removed in a wastewater treatment plant. This fraction will be determined for the City of Bristol through analysis of a number of composite samples by the Stamford WPCF in January 2000. They city wishes to state for the record that we fully plan on upgrading our facility with an eye to meeting the phased nitrogen limits culminating in the final limits in the year 2014. We are concerned though that we are being permitted at the limits of BAT and run the risk of non compliance during periods of insufficient nitrogen removal. Please review Table 1 {available in hard copy}, which shows historical organic nitrogen concentrations from March 1997 through the present. The data reveals large fluctuations in organic nitrogen content, which are our greatest concerns.”

Those large fluctuations are now attributed to fall and spring rains, washing “hard nitrogen” (and leaves) in the form of organic matter. This nitrogen TMDL concern and related eelgrass research was also a part of CCMP-CAC review discussions. As for back as 2006 a concern existed during some CAC meetings that placed much more emphasis on human nitrogen reduction to protect submerged aquatic vegetation or SAV for short. This emphasis often contained a position which overtime became research bias (also called research suppression) with the apparent exclusion of historical references that did not support the current view or perception of SAV significance to shellfish or benthic habitat quality, especially for eelgrass. {In the historical records eelgrass meadow is often found to be detrimental to shellfish habitats.} The bias as to second source generation known as benthic flux regarding the nitrogen TMDL also included the question of Sapropel formation was also raised to the nitrogen non point source LISS working group also in 2013. For southern areas mild snow free winter rains would wash organic matter (manure) from fields when in colder periods it would be frozen and held in place as soil nourishment. As the heat continued (into the 1990s) organic matter flows increased (both north and south) masking a much larger nitrogen problem that was largely climate induced – the sulfate/ammonia pathway. (The period from 1972 to 2012 would resemble habitat and fisheries catches of a similar “hot term” 1880 to 1920 approx.).

{At the time some members of our CAC felt that we should cause a review of the EPA second source (organic matter) and nitrogen reduction position in the CCMP but on October 16, 2014 our CAC delivered a letter of concern to the EPA – the CAC held a press conference at Housatonic Community College in which to deliver it. Instead of pausing and taking a step back to review nitrogen policies or nitrogen reduction/removal programs in terms of habitat quality they were proposed to be strengthened – T. Visel}.

We need to conduct a meta analysis of the nitrogen research that contains this research emphasis (whenever confirmed) that maximizes direct human nitrogen sources but minimizes or excludes the toxic impacts of climate induced Sapropel (my view). Much of the first focus of such nitrogen reduction programs was living marine resource based, the fisheries and seafood utilization. The basis of this concern was combined with a need to balance a long term historical fisheries perspective, much of which has a climate change foundation (cycle) with the nitrogen TMDL itself. Research from overseas has recently supported similar toxic sulfide concerns and the research bias that excludes climate cycles is appearing in other marine fields as well, dredging (which is vital to the Port of New Haven), Connecticut early salt marsh habitat values and fisheries management policy (long term habitat stability and habitat quality) as it for example relates to recent lobster fishery investigations – the 1898 southern New England lobster die off are some of the areas of needed review.

We need to look at climate and energy cycles to more fully understand nitrogen impacts to fin fish and shellfish habitats. Most of that review information is found in historical reference materials which include climate and energy cycles over the past century or more. Much of the current research papers do not include such long term historical information leaving questions about the impact of mild open winters on organic (not human) inputs. Some communities have spent millions of dollars (or public state/federal funds) to remove a few hundred pounds of aqueous nitrogen as organic matter inputs – (leaves woody tissue) more than offset these reductions. We may have been better off if we had concentrated on organic source nitrogen (including manure) than field agricultural fertilizer application or human sources (my view). {To the farms to our south – a colder cycle 50 years ago froze manure in place a past practice that continued when winters were open and contained heavy rains it would be “natural” to see such climate impacts influence nitrogen levels).

Most recently research on the west coast identifies a suspicion that we may have in fact targeted the wrong nitrogen compounds for removal in terms of fish and shellfish larval habitat quality. Shallow waters those protected from energy dispersal or predation are often termed critical but the most impacted by sulfate reduction. This involves investigating the oxygen/nitrate pathway in cold versus the sulfate/ammonia pathway in heat. (Did TMDL nitrogen models include climate change). This aspect (if sustained) has far reaching policy and economic impacts for coastal communities across the country.

Students considering this topic for a public policy Capstone or ISSP proposal please contact me if you have any questions. Most of the available estuarine habitat quality information that includes climate change is coming from Denmark and Australia. Sulfate reduction is often termed glucose metabolism – the ability of sulfur reducing bacteria to break down these organic surveys from the production of terrestrial organic matter that enters the sea.

Tim Visel

The Capstone Proposal

Statement of Problem – Nitrogen/eelgrass TMDL linkage to fish and shellfish abundance
While many US Communities spent hundreds of millions to remove water borne (dissolved) human nitrogen and based upon TMDL allowances that had focused on only part of the nitrogen sources. The largest negative nitrogen habitat factor for fish and shellfish populations in heat was from leaf and natural organic material in shallow warm sediments. [Also termed Benthic Flux, Sapropel, Black Mayonnaise, gytta - See The Norwalk Hour 10/21/2012 Black Mayonnaise in the Saugatuck River, Dick Harris, Southern University Newsletter, August 2011 Vol.14 #6 Sound School Southern New Haven Harbor Collaborative page 1., Dr. Vince Breslin, New Haven Harbor Black Mayonnaise. Early LISS researchers called benthic flux particulate organic matter (POM). More recently termed organic nitrogen flux accumulations of organic matter can purge ammonia directly into coastal waters during high heat. The term flux is an analytical measure which does not adequately define organic deposits that sustain sulfur reducing bacteria.] This is frequently called benthic flux or benthic generation but does not include the formation of Sapropel – mentioned as a concern at the very beginning of the Long Island Sound Study (1985-86). The public policy agenda soon eclipsed other non human nitrogen concerns as a crisis public policy reaction that occurred when Long Island Sound experienced a warm climate cycle in the late 1980s into the 1990s2. [I have the “open classroom” situation that happened here in CT as a classic and often cited educational reform example. Educators who spoke up in the 1970s expressing concern about large general purpose rooms with hundreds of students in one large room without walls or partitions were often excluded from the decision making process. Decades later reflection upon the open classroom school buildings does not share the early reported optimism, or public policy support in fact, in most cases open classroom school construction projects are generally described now as “failures.” In the public crisis regarding Long Island Sound health in the 1980s a desire to fix excess “nitrogen” quickly often did not include second source or benthic flux generation from natural organics. The mention of Sapropel is clearly absent from Long Island Sound Study documents, but was highlighted in Long Island Sound – NOAA Estuary of the Month Seminar #3 – Battelle Contract #68-03-3319, 1/15//86 “Underlying the dysaerobic and an aerobic water one typically finds organic – rich black (i.e. sulfidic) muds that are termed Sapropels. These are rich in iron, mono sulfide. The best description that I have heard of them (The physical properties of these muds are distinctive) is that they are like a “black mayonnaise – The Benthic Ecosystem Dr. Rhoads Yale University pgs 47 to 57 (Published in 1987).]
Large areas of Long Island Sound became anoxic shellfish and finfish perished. Excess nitrogen was linked to these catastrophic events. In time programs were put in place to reduce nitrogen entering Long Island Sound.

The eelgrass/nitrogen indicator for water quality

The eelgrass/nitrogen research controversy centers on the growing conclusion that we may have targeted the wrong nitrogen sources and chose the wrong environmental indicator (eelgrass) to measure it regarding fish and shellfish habitat quality. The problem is changes in eelgrass abundance was a key reference as evidence that nitrogen reduction is beneficial and the reason (justification) to spend hundreds of millions (perhaps) billions citing eelgrass as an embayment health indicator, however that concept of an eelgrass quality indicator now is subject unfortunately to scientific review – citation or reference amnesia review regarding eelgrass. There was ample evidence decades ago that sediment sulfides negatively impacted the growth of eelgrass and may be subject to natural cycles dominated by temperature and energy – storms not human impacts. Most of those submerged aquatic vegetation studies were conducted in southern areas – especially Tampa Bay. Recent studies now indicate that nitrate can even influence pore water sulfide levels below those lethal to submerged aquaculture vegetation (SAV) Carlson et al in a short report over a ten year period 1990-2000 - (The Effects of Sediment Toxicity on Florida Bay Turtle Grass – A synthesis of field experiments 1990-2000) found a direct relationship between pore water sulfide level toxicity and the addition of nitrate (potassium nitrate) amendment “lowered pore water sulfide concentrations significantly.” (This is the buffering capacity of nitrate that Hyannis Waste Water treatment operators mentioned the importance of nitrate to filter beds in hot weather).
Dozens of studies have indicated that most critical factor to eelgrass habitat quality is the amount of sulfides in the sediment (marine soil); some date back to the 1980s. Important sediment sulfide studies that could have pointed the nitrogen/eelgrass research in a very different direction were “forgotten” and misrepresented perhaps in an effort to respond to public policy pressures3. [As Long Island Sound warmed and lobsters died off public decision makers were faced with a “do something now response” from the public – decades later we now know more about this warm period and the impacts of heat upon shallow and surface waters. A similar lobster die-off occurred in the 1890s and in 1899 a Ice failure or famine occurred in Southern New England when waters were so warm ice did not form. The heat continued as Tarpon were now caught in Narragansett Bay in the early 1900s. A cooling period occurred after 1931 which continued to 1972.] This bias appears to have a foundation in numerous EPA TMDL documents apparently “benthic flux” exclusion of second source generation nitrogen in the formation of TMDL limits. This resulted in a greater emphasis – to human nitrogen sources as overall factors/limitations to seafood abundance. As a long term perspective lacked any historical reviews (most looked at a decade or two) and therefore missed the 1950-60 negative NAO climate pattern.

The Sapropel – sulfur cycle is also clearly underrepresented in the marine eelgrass literature especially when sulfate is not limiting. In winter sulfide purging occurs from organic benthic sludge (Sapropel) often containing an eelgrass crust. The long term ecological services of eelgrass have been questioned for almost a decade. (NOAA report by Tim Visel, Dec 2006) and historic non supporting or negative habitat references have been excluded from most of the current eelgrass studies. More recent studies from Europe (Denmark) eelgrass meadows have a direct role in helping sulfide formation. Such reports highlight the negative impacts of binding organic matter accretions while in United States several studies highlight them as positive. The winter rains of now “open” winters became the common “enemy” for manure in the south and leaves in the north for east coast estuary programs. Rains washed huge accumulations of organic matter into estuaries and in high heat overwhelmed the oxygen/nitrate reduction bacterial pathway.
Just as New England fishers watched as bay scallops disappeared as brown tides enveloped coastal bays farmers now had manure wash from fields devoid of snow. Frozen fields gave manure a chance to be assimilated into agricultural soils. Snowfall does not wash nitrogen from fields but rains in an open winter will. Did farmers realize they were heading into a positive NAO – with winters that had heavy cold rain?

Alan Taylor a soil scientist with the University of Maryland Agricultural Experiment Station had some idea, calling the nitrogen cycle “leaky” in a Maryland Sea Grant publication titled Troubled Waters – Jack Green article titled “Fertile Waters: Stemming The Nutrient Flow (1985).

The combination of dry summer growing season was in Taylor’s words “a horror” – plants could not grow and the winter came and rains saturated fields – this left much of the nitrogen “available” and ready to leak into the watershed. Taylor sums up the problem – on pg 4 “You tell me what kind of weather were going to have this summer, and I’ll tell you how much nitrogen to put on your field.” Blaming fishers for empty dredges or farmers for warm winters is what we often do, while both had no choice before massive climate cycle impacts. In northern areas a renewed forest canopy dropped million of tons of leaves in southern areas manure washed by “warm” winter rains added to composting habitats that purged ammonia much as those composts on land sealed from oxygen. It is thought that a leaf burning ban also contributed to the increase in organics entering water courses (1970s). I was introduced to that concept while involved in Herring run restoration on Cape Cod.

We call second source nitrogen generation organic material from leaves ammonia – summer and in winter sulfide purging, one of the most toxic of all substances to fish and shellfish. An organic paste a residue of forest litter and leaf fall has been swept into LIS after a series of strong storms. In high heat this organic matter breaks down into Long Island Sound a slippery black ooze often called Black Mayonnaise by fishers. In streams in iron poor waters this substance is often brown having the consistency of loose peanut butter. This is fresh water Sapropel. In New England fresh and saltwater Sapropel has a long history of fertilizer use, including Connecticut Rivers (IMEP #26 oystering fish eel thread Blue Crab Forum™).

The issue of fresh water Sapropel has been an educational effort to address as well. Many mill ponds have accumulated deep organic deposits behind them and that as dam removal occurs this “back log” of organic debris or sometimes referred to as “legacy sediment” now moves into the estuaries during storm or rain water events. It is a flow of sludge that often has the consistency of firm peanut butter in low flow streams. This is the Sapropel that Connecticut farmers once harvested for use as fertilizer from local coves and mill ponds. Storm water and rains into streets can also wash this sludge downstream forming a paste like substance that is sticky (left over leaf paraffin’s). In slow flow areas it takes on the consistency of peanut butter a slippery compost that can shed sulfides when disturbed. This occurs during spring rains (ice melt) and this material collects at the headwaters where it now turns black with iron sulfides. It is a toxic substance when in motion and can cover entire estuarine bottoms when it finally reaches the coast. Many alewife streams subject to leaf falls are suspected of forming sulfide blocks – ruining or reducing runs.

Many programs state and federal have both set to remove these dams and increase stream energy. One factor that should be considered is altered natural drainage – storm street water now has the capacity to delivers vast amounts of this organic matter very quickly into streams especially with Connecticut’s forest canopy now at 78% coverage. The amount of leaves entering our estuary has soared. This material is nitrogen rich (depends on age) and is also termed “legacy nitrogen sediments” in more recent literature. It can have an negative impact upon herring runs (alewife) sulfide and aluminum levels need to carefully monitored. When this organic material reaches the estuary it is often collected by eelgrass acting as a low profile dam that gathers organics in deep deposits. It is this ability of eelgrass to collect or slow organic deposits that is so damaging in high heat. Eelgrass meadows under these circumstances purge sulfides which are toxic to fish and shellfish larval forms.

Also implicated in this growing eelgrass/nitrogen controversy is the association of eelgrass and other submerged aquatic vegetation commonly called “SAV” to specific estuarine health indicators. SAV became an environmental lightening rod so to speak to galvanize public opinion and then public policy makers as to protect and conserve SAV habitat types. In New England, eelgrass was promoted to benefit the bay scallop, a much-admired delicacy in our bays and coves. While lightly populated SAV patches are beneficial as reef habitats in long periods of heat and little storm activity, dense SAV meadows collect organic matter, which then sheds ammonia in heat and purges toxic sulfides in winter. In the end SAV becomes natures sulfide killing fields signaling the end of periodic habitat succession. It is deadly to shellfish and finfish larval stages and sheds ammonia a key nutrient ingredient for brown algae also called Harmful Algal Blooms or “HAB” for short. A huge source of ammonia is second source generation from organic deposits and was not included in the TMDL process. (EPA Source Document EPA 600/R) – 09/050 June 2009). As eelgrass density declines the purging of toxic substances increase reducing biological diversity and richness. In the end sulfides becomes so high toxic they kill eelgrass itself and drives fish from these now “barren” mud flats. By this time any existing benthic shellfish populations were long ago suffocated. A link to declining eelgrass populations to declines in fish and shellfish biological richness is therefore natural.
The shellfishers on Cape Cod correctly called the SAV/shellfish relationship decades ago, but no one believed them. How could the shellfishers be correct when nearly all of the current scientific community was promoting the eelgrass/bay scallop model? In this situation, quite simply, the Cape Cod and Niantic Bay CT bay scallop shellfishers “nailed it.” On many areas on the Cape and Massachusetts coastal coves dense eelgrass growths destroyed bay scallop habitats or caused low meat yields from limiting food. Several turn of the century shellfish researchers had reported on similar negative habitat observations regarding eelgrass and shellfish. Eelgrass meadows attracted ducks and geese and increased feeding soon had fecal material covering the bottom – closing shellfish beds as bacterial levels increased. Although bay scallops will set on the “clean and green” eelgrass – the brown and furry eelgrass is often associated to sulfide or “deadline” formation.

Dense thick growths of submerged aquatic vegetation directly suffocates living benthic shellfish and destroys habitat capacity for future populations. At the end of its habitat “clock” it traps organic matter and increases sulfide purging – that is a type of habitat succession. In heat and low energy environments it assists habitat types Sapropel that help end its life cycle. (Sulfide toxicity weakens eelgrass to opportunistic fungal infections). In the end storms uproot these weakened plants from root necrosis – tissue rot – leaving Sapropel deposits.

The law of habitat succession or those who have fished and shell-fished in New England’s coves and bays and have seen eelgrass come and go in long term natural cycles often share a different view of eelgrass. The habitat history of eelgrass is very different than what have been portrayed to the public even to the current shellfishing community itself. We know from historical records (mostly from the State of Massachusetts) that dense eelgrass meadows were not beneficial for shellfish populations and in fact now it seems that Bay scallops will set on eelgrass not as a preferred settlement type, but largely perhaps to escape toxic sulfide (sulfide deadline) purging from the eelgrass meadows below. Early bay scallop studies clearly documented “blade attack” from crabs and that scallop fishers (CT) called redweed the true “scallop grass” which also served as a settlement type for bay scallops, and the source of these reports were the bay scallop fishers from Niantic Bay itself (setting and spawning chemicals for scallops worldwide has been identified to coralline red algae). These reports and historical documents report that dense eelgrass monocultures destroyed numerous New England shellfish habitats were forgotten, a type of scientific misconduct as they do not appear in the more recent eelgrass research. (Often termed cherry picking sources that only support stated positions and also can be termed the “funding effect”). In fact both long after recent green crab research indicates that it has a strong habitat association with eelgrass – and may in fact arrived from Europe North Sea around the same time long after our ice sheet receded. {John Hammond on Cape Cod suggested that eelgrass was a packing material for the first shipments of oyster in barrels and he believed our strain in fact was not native}.
Introduction

This report began in 2013. It first examined how bacteria formed, but was later expanded to include Sapropel and bacterial filter systems to remove ammonia compounds. When many U.S. estuaries suffered from oxygen depletion during extended warm to hot periods, the oxygen/nitrogen pathway was emphasized as low oxygen levels were observed to be impacting both finfish and shellfish. But elemental oxygen was only one source of oxygen into Long Island Sound waters; if total oxygen availability (TOA) was examined for bacteria three distinct oxygen reduction pathways existed - those bacteria that utilized oxygen in a dissolved O2 state or those that utilize oxygen bound to nitrogen compounds of nitrite and nitrate or those who used sulfate – abundant in sea water.

The oxide of sulfur (sulfate) was an oxygen source for a very different type of bacteria - those who do fine in high heat, the sulfur-reducing bacteria or SRB. Sulfate is not limiting in saline waters. Sulfur Reducing Bacteria (SRB) are now associated with producing some of the most toxic substances – hydrogen sulfide, ammonia and metals, such as toxic aluminum.

As nitrosomonas and nitrobacter bacteria needed oxygen in nitrogen compounds to survive, sulfate-reducing bacteria did not. As nitrosomonas and nitrobacter bacteria removed toxic ammonia and helped keep habitats viable, sulfur reducing bacteria poisoned it with sulfides, sulfuric acids, often with heavy metals and toxic aluminum. Most nitrogen reduction programs removed nitrate and the nitrite and when they did, they also removed the TOA oxygen that could help keep nature’s natural filter systems alive. Instead of improving oxygen to these bacterial filter systems that need it – it was removed.

Once that happened, sulfur reducing bacteria out competed the oxygen-reducing bacteria that consumed organic matter deposits. Organic matter became both the food and toxic producer for a sulfur killing zone impacting fish and shellfish larval stages. By reducing nitrate and nitrite, we may have reduced nature’s ability to modify the high heat / low energy impacts of sulfur. Did we, by removing those nitrogen compounds containing critical life support oxygen, make sulfur toxic conditions only worse?

Apparently the only ones concerned about this oxygen loss were some waste water treatment operators at the time (1980s) who in heat had some experience with “secondary oxygen sources” such as nitrate in keeping bacterial filter systems from dying or collapsing. When it came to nitrogen removal, did we in fact make a bad condition only worse for our seafood?

I believe we did.
I respond to all emails at Tim.Visel@new-haven.k12.ct.us