Plankton does not only kill by producing poisonous organisms, but it can also kill because it contains a strong catabolic (decomposing) part consisting of active bacteria, fungi and viruses that are necessary to decompose dead organisms and wastes. As a result, most organisms in the sea, and particularly those who depend on plankton for food, live in constant defiance of death. By increasing the density of the plankton soup, the additional food is of no extra value to them, but the decomposing bacteria become a life-threatening risk. This simple theory (hypothesis) explains many vexing questions about the undersea ecology and habitat degradation, an ecofactor that has been overlooked completely.

The mere formulation of a problem is far more essential than its solution, which may be merely a matter of mathematical or experimental skills. To raise new questions, new possibilities, to regard old problems from a new angle requires creative imagination and marks real advances in science. - Albert Einstein

Another vexing question asks why marine life is so different at remote islands compared to the best places along our coast, and why these in turn differ from locations near population centres. The common theme is that the water becomes clearer as one travels away from population centres towards remote islands. But how can this explain their differences in marine life? Obviously, harmful pollution diminishes but so does nutritious plankton density.

Then the idea arose that the solution to these and other vexing questions, is indeed quite simple. Normal plankton feeds and kills at the same time! It has to, for sound ecological reasons.
 
 

The diagram on right pictures the planktonic food chain, starting from phytoplankton through zooplankton to higher vertebrates (fish) and mammals like dolphins, not shown in the diagram. The many trophic (food) levels are necessary to convert the energy from sunlight into ever larger food packages, from minuscule plant plankton to zoo plankton to fish larvae to small fish to large predatory fish. But this is not the complete story. The plankton food pyramid is part of a larger food chain, a planktonic ecosystem in which nutrients are eventually restored to feed the phytoplankton. It is a closed cycle.

 

This diagram simplifies the food pyramid above but adds the missing components that complete the nutrient cycle as is characteristic of any ecosystem. From nutrients and sunlight the plant plankton captures solar energy and packs it into carbohydrates and proteins, the basic food for animals, which begin in the animal plankton and end with higher vertebrates (fish). In the process, energy is used up for moving and growing, resulting in an ever smaller biomass (ovals) for each higher trophic level.  As energy is burnt, it is returned in the form of carbondioxide and water but as animals digest their food, a large part is excreted as waste. The tiny dead plant plankton and waste particles from zooplankton are intercepted by the guild of decomposers, consisting of viruses, bacteria and the equivalent of fungi (saprobic microbes).

Saprophyte: Gk sapros= putrid; phyton= plant. Sapro- = rotten. Any microorganism living in and on putrid matter
Saprogenic: causing or produced by putrefaction
Saprophile: a bacterium inhabiting putrid matter.
Saprophage: feeding on decaying matter

Dead phyto- and zooplankton organisms are mostly decomposed in mid water but the wastes and bodies of larger animals sink to the sea bottom where they are decomposed by a different guild of benthic (bottom) decomposers. Some of these have claws and teeth to physically divide the larger particles into smaller ones. But eventually the nutrients, the ashes of life, are returned to the water where they take part once again in the planktonic food cycle.

Because plant plankton has a short life, much of it dies and decomposes in mid water. As can be seen from the diagram, the amount of energy (food, dead bodies and waste) flowing through the planktonic decomposers is a large part of the total. It is a very active guild, and not surprisingly a threat to life because they decompose living cells as eagerly as dead ones. Fortunately, the biomass of these decomposers is relatively small because they are so active, but their numbers are extremely high because they are so small (picoplankton).

Think for a moment about ourselves. Inside our guts we host a very active community of decomposers, most of which are bacteria of the genus Eschericia coli (E coli), a sausage-formed single-celled microbe. We live in a cautious balance with this destructive organism, protected by a special slimy lining inside our guts. But things can go wrong as in an ulcer, and an appendicitis. When the gut bacteria break through the gut lining, entering the cavity of our belly, death is almost certain as these bacteria decompose cells they were never meant to decompose. Scratch your skin, and most likely an infection results from the same guild of bacteria. When left untreated, such infections can kill.

Now imagine living inside a soup of food and faeces, complete with gut bacteria, viruses and fungi. That describes what it means to live in the sea. All marine organisms have developed some level of defence, like our gut lining, but when overwhelmed by decomposing bacteria and viruses, the nutritious soup can kill. Thus ironically, plankton has two sides to it: on the one hand the life-bringing food but on the other hand the deadly decomposers. It both nurtures and kills. It is thus understandable that all sea animals have slimy skins to protect themselves from the deadly decomposers.

The next part of our thesis is the assumption that marine organisms have evolved to occupy a niche in the gradient from dense to dilute plankton. If the plankton soup becomes thinner, the organism dies from lack of food. Conversely, if the soup becomes too thick, organisms can no longer benefit from the additional food, and they become threatened by the decomposers instead. So each organism and community of organisms has evolved to live in balance within a particular density of plankton, most suitable to its own success. In this manner an unusual plankton bloom can kill a large area, including many species, without actually being poisonous.

Some organisms have evolved to live in a wide range of conditions and these we call hardy. Conversely, those restricted to a narrow range are sensitive. It just so happens that there are many sensitive species but only few hardy ones.
 
 
 

f033805: In this very degraded environment live three hardy sponges that are also found in the cleanest of waters: The yellow boring sponge (Cliona celata), the orange or golden golfball sponge (Tethya aurantium) and the massive grey sponge (Ancorina alata). (Martins Bay)

f036831: A fragile and sensitive bryozoan (polyzoan) of the Pterocella genus grows on sheltered vertical walls or under overhangs, where currents flow but waves do not destroy. It is often preyed upon by specialist nudibranchs. Normally these are clumped together forming a fluffy turf, which makes photographing an individual difficult. But this photo was taken where nearly all bryozoa had disappeared, and with them their predators/grazers. This surviving specimen stands alone and is larger than normal. (Arid Island)

Reader please note that this hypothesis lacks formal proof. It is attractive as a working hypothesis because it is derived from sound ecological principles, while it explains many vexing observations. As a theory it should also be able to predict. To my knowledge, this is the first time this hypothesis has been proposed. Floor Anthoni, June 2003.
In January 2005 we invented a measuring technique to quantify the biomass of decomposers and their aggressiveness. Since then very solid support has been found for the Plankton Balance hypothesis. See the extensive chapter about the Dark Decay Analysis (DDA).

This hypothesis was presented at the annual conference of the New Zealand Marine Sciences Society's in Auckland on 2 Sept 2003 where it was received with hostility and ridicule. The words of session chair Sam McClatchie, a fisheries scientist from NIWA, sums it all up: "Although it was an enthusiastic presentation, you have underestimated your audience and would do well to go back to school to do a course on plankton ecology".

nzmss.rsnz.org/pubdocs/pdfdocs/Review_45_2003.pdf  Presentation of The Plankton Balance Hypothesis to the New Zealand Marine Sciences Conference 2003 in Auckland. (p29 of 171pp, June 2004)

A plankton or nutrient gradient results as on the one hand plankton is consumed, while on the other hand plankton and fine mud ooze down the continental slope into the abyss (depthlessness) of the the deep ocean. This diagram shows how soil arrives into the sea as mud. Consisting of three main components, sands, silt and clay, the mud is winnowed into these components which settle out in this order away from the shore. Also nutrients are released, giving rise to plankton blooms a few days later. The plankton cycles renourish the nutrients, but eventually they are lost down the continental slope. It is a slow and gradual process acted upon by forces that mop the nutrients back to the land, thus minimising losses (see diagram)

As a result a gradient exist from thick soup to thin, extending out from the shore. Similar plankton density gradients exist along the shore, extending out from dense populations or where rivers enter the sea. Particularly rivers on large continents provide steep gradients extending outward and along the shore away from their mouths.
 
 

This diagram shows four gradients. The top two relate to a coastal gradient, for example when moving away from a population centre along the coast  from say, west to east. The top situation shows where six species A to F choose to live, at a plankton density most suitable for their existence. Think of these hypothetical species as hypothetical communities of species. This is of course a most simplified situation, since many species tolerate a wider range of plankton densities, such that their zones overlap. As the coast pollutes, the gradient moves further east. This destroys all species along the coast, as they become replaced by ones lower in the alphabet. But it seems as if nothing much has happened but a shift in habitat. Note how species F becomes extinct as also a new niche is vacated by species A for unknown (?) species to occupy.

The third and fourth row show a coastal profile, extending outward from the shore. Species E lives on an island. As the environment pollutes, species B and E are pushed off their substrate and vanish. Their places become occupied by species A and D. Again, it seems as if nothing much has happened, yet major mortalities over the entire region accompanied the process. Species E may even be pushed to extinction this way if it has no other place to re-establish itself.

The question marks raise an interesting question: what will establish in the places left behind by species A? This is where foreign introduced species may find a foothold. Note that with each increase in pollution, another habitat shift occurs accompanied by more mass mortalities, and the possibility for alien species to establish themselves.

In other words, a seemingly innocent increase in pollution will be accompanied by:

• disease, particularly viral, fungal and common infections.
• major mortalities over large areas, affecting many species
• a chance for alien species to establish themselves, particularly near large populations of people (!)
• loss of long-lived species, particularly sensitive ones
• the possibility of true extinctions

Now imagine that we have a ten year cycle of good years alternated by bad ones. In other words, the plankton density shifting in and out, east to west and back again, repeatedly. It will lead to:

• permanent loss of many species, including vertebrates (fish)
• permanent loss of long-lived species
• an overall degradation of all habitats with fewer species, even those far out in sea over the continental shelf
• repeated opportunity for alien species to establish themselves here, because few if any indigenous species exist to fill this niche.

Now imagine the picture with a gradient that is even steeper than shown. Obviously, the effects will be more accentuated. This is what has been happening in the past twenty years - reason for alarm.

Gradient in time
The above picture is valid not only for spatial gradients, but also for gradients in time. Wasn't it Capt d'Urville who mentioned in his ship's log that the water was so clear while anchored where now the Harbour Bridge in Auckland spans? He could see his anchor 15m down. Visibility there is now 0.5-1.5m!
Apparently a steep gradient has occurred since the arrival of White Men, and this gradient has been worsening (steepening) rapidly in the past twenty years. As shown in the diagram above, this has been accompanied by mass mortalities, particularly of those species that are attached to the substrate, unable to move to more suitable places.

This new theory predicts that if we were able to turn back time by cleaning the water and reducing the concentrations of mud and nutrients, the recovery phase will also be accompanied by mass mortalities, although less severe.

Reader please note that none of the above has been proved by scientific method. However, our observations neatly fit the theory.

It is common for marine organisms to start life at less than 1mm in size, growing to 50mm before leaving their planktonic stage. This equates to a growth of 50x50x50= 125,000 times, a miraculous act. During that time, the organism must efficiently find larger food parcels, thus changing its diet regularly as it grows. How this is achieved for the many species involved, is not known.
 
 

For our hypothesis it is sufficient to know that nearly all marine organisms, and certainly all of our commercial species (except sharks, etc) start life as very small fry (1mm) with proportionally thin skins, being totally dependent on the composition of the plankton soup. Like other species, they too are successful only if they are hatched in the right density of soup with enough nutrition but insufficient decomposition to kill. This can easily be inadequate, resulting in recruitment failure. For snapper, temperature is important too. Not because snapper produce more eggs in warm water, but because for some unknown reasons, warmer water is accompanied with better hatching and survival conditions for their larvae. Here in NZ the warm water years are also accompanied by cleaner water.

What we have been seeing underwater is the recruitment failure of many invertebrate species, and recently also of vertebrate species like snapper. Scientific fishing trawls confirm this. What is so worrying about this new problem, is that it is rapidly worsening as we enter a new era of scarcity. We cannot afford to wait and see.

This diagram shows the amount of light falling on Earth, for three places on the northern hemisphere (summer in June/July). The diagram does not take into account the sunlight intercepted by clouds. Note how light varies only little from season to season in the tropics (red curve). By comparison the light at the poles (blue) reaches zero in winter, to rise ABOVE tropical values in summer, because in summer the sun shines all day. The availability of light can be a problem for places with dark winters, as the diagram shows. In a temperate climate like that of New Zealand (about 40º latitude, green), the difference in incident light between summer (light intensity x duration= green curve) and winter can be as much as three times (40/13).

When light absorption by clouds is taken into account, the difference between winter and summer becomes larger still. This diagram shows the actual amount of light measured in Lincoln, New Zealand, which is situated near the middle. As one can see, the radiation runs from 4 to 24 MJ/m2/day or six times more light in mid summer than in mid winter. [Guess where the 'winter blues' come from?]  But for underwater plants the situation becomes worse still due to the amount of light reflected back into space by the water's surface.

This diagram shows a polar diagram of the theoretical amount of light reflected off the water (orange lobe) and that transmitted into the water (blue lobe). Note that when the sun stands lower than 40 degrees during the day, much of its light does not enter the sea (one third of blue lobe). For New Zealand the sun moves in the range of the numbers 4, 5 and 6 in winter and in the range from 2 to 6 in summer. Note at this point how the light is bent in such a way that the sun appears to be overhead as the sun rays are descending more steeply into the water. The blue lobe misses the light from angles where the words 'transmitted light' appear.  Furthermore, divers observe that the moment their cameras go under water, they experience a loss of light of at least 50%, which is caused by the vagaries of ripples and waves. See graph As a result, the light underwater in temperate seas is scarce, a limiting factor. Not surprisingly, marine algae have evolved methods to catch what is possible of this scarce amount of light. They have evolved different pigments like brown and red in order to absorb light more efficiently, which brings us to the quality of light under water.

This diagram breaks sunlight down into its visible components and the invisible UltraViolet A and B. Horizontally it shows wave length (colour) and vertically the amount absorbed per metre of depth. For ease of reference, coloured bars show what these wave lengths mean. Three curves are shown, the absorption in blue oceanic water (50m viz), polluted oceanic water (35m viz) and coastal water (10m viz). It omits showing the absorption curve for truly polluted coastal water which lies anywhere above the green curve.  An important conclusion from this graph is that even the clearest of waters absorb the red and orange components almost as much as coastal water does. This is simply a property of water. However, note how the UV component is absorbed quickly by green coastal water compared to clean oceanic water. But what seaweeds need for growth, are the yellow, green and blue components of the light. For these the brown and red 'chlorophyll' pigments are most suitable (chlorophyll is green).

f033429: Most of the large seaweeds (macroalgae) in New Zealand have brown pigments, like this stalked kelp (Ecklonia radiata) found here in the sheltered shallows of a rock pool. The brown pigment which can look reddish, brownish or greenish is suitable for absorbing light in shallow to moderate depths. (Tawharanui)

f034114: Red seaweeds like this (Pterocladia lucida?) are usually small. They do well in lower light conditions and deeper water. Their red pigment is more suitable for absorbing the blue component of the light, which is more prevalent in the deep. Red seaweeds are sensitive to pollution. It is not known why. (Mayor I)

f001319: One of the most amazing of marine algae is the pink paint, a crustose coralline alga (Lithothamnion sp.) or stone-leaf. It grows a single 'leaf' of hard limestone inside which it lives. This limestone is hardy enough to survive the bite marks of grazers like sea urchins, Cooks turban snails and others, all visible in this photo. The pink paint lives higher on the shore than any other and much deeper too. (Goat Island)

f034100: Turfing coralline algae have evolved into finely carved forms like the one shown here, consisting of flexibly jointed bits of limestone, infused with pink coloured plant life. These plants are very hardy, resisting strong wave action, low and bright light conditions and many forms of pollution as well. (Mayor I)

Loss of light alters coastal marine habitats quite considerably. Whereas seaweeds are probably less sensitive to the composition of plankton with regards to its catabolic component (they do not feed on plankton, nor do they breathe it), they are very sensitive to the loss of light caused by thicker plankton soup or mud particles in the water.  This diagram shows how the coastal fringe degrades. On left a clear water situation with healthy kelp, dense canopy, large urchins, high biodiversity and many species of sessile filterfeeders. The photic zone (light zone suitable for plants) penetrates deep. As the water degrades, so does the coastal habitat, eventually resulting in very few plant and animal species. As the photic zone moves up, it is accompanied by a severe loss in biodiversity. The catabolic component takes care of killing the sessile animal species. Suffocation from sticky mud is also a problem. The situation with the plankton soup, however, is quite different.

Plankton species are essentially weightless, living suspended in the water (this is not entirely true). Eddies and currents move them around not only horizontally but also vertically (up and down). Whereas a coastal seaweed lives attached to the rock in a certain position relative to the photic zone, phytoplankton has the added difficulty of moving in and out of the photic zone. In other words, the phytoplankton has all the difficulties of seasonal loss of light plus the problem of being moved in and out of the photic zone  also when the sun shines. Not surprisingly, phytoplankton suffers high mortality but this is offset by its ability to grow and reproduce fast, for which sea water temperature can be decisive. What then is the effect of degrading water quality?
 
 

As the plankton soup becomes thicker or when polluted by clay particles, the photic zone extends less deep, resulting in poorer growth combined with higher mortality of the phytoplankton. It is a double-edged sword by which the productivity of the plankton can diminish very rapidly, leaving the water free for other organisms like cyanobacteria (bacteria that photosynthesise like plants) to take over. The soup becomes poisonous. Precisely how this works is not known, but our theory predicts that the soup becomes less nutritious and more murderous, resulting in all kinds of unforeseen problems.  Ultimately a dead zone is formed, as happens every year near the mouth of the Mississippi River in the USA. This diagram shows how sediment and dense plankton reduce the photic (light) zone. As the overproduction of phyto plankton rains down to the deep, it dies while decomposers in the water do their job. More rains down onto the sea soil, where the bottom decomposers act. They all need oxygen which runs out. Then the anoxic decomposers take over and the whole sea and bottom become a stinking black putrid mess.

Does the plankton like the rocky shore become less diverse as the plankton becomes more dense? It behaves like a double-edged sword: on the one side the threat of reducing light and on the other that of increasing chance of infection.
Can the plankton become 'sick' such that it no longer functions as a food producer? Is it possible that the decomposers start to attack the live producers? It all depends how the balance changes. In the end, the dead zones prove that plankton can become very sick indeed. One could even say that it can die.

If our theory holds true, then the death and disappearance of sponges is caused mainly by the murderous component of the plankton, which is not unlike that of disease-causing microbes and viruses. Being able to survive their attacks suggests that such sponges have a secret that could well be of benefit to people. It is an idea worth investigating. Here are the winners in our contest (also look at the first photo of this section).
 
 

f035922: The ugly grey massive sponge (Ancorina alata) is perhaps the most rugged of all, not only surviving in polluted waters but also in waters with little nutrition. Here it shows signs of distress, unable to shrug off the attack by the invading pink paint. (Little Barrier I)

f011302: These velvety black soft sponges and orange/cream intestinal seasquirts are typical of highly degraded habitat. Ugly and ominous, they may well contain potions of longevity. (Houhora Harbour)

Those that are able to roam more freely may opt to limit their feeding presence in dense plankton, to return to clearer waters for resting and socialising. Several species choose to spend most of their time in the clear and cleaner depths below 30m, only to come near the surface for feeding. Others choose to rest along steep cliff faces where their wastes cannot collect.

It would be interesting to pursue this idea further to see if some of the behaviour of marine organisms can be explained in this manner.

Our new hypothesis is based on the two components of the plankton, the productive (anabolic) branch and the reductive (catabolic) one. For maximal productivity, all green matter (phytoplankton of sufficient size) must be eaten (grazed) by zooplankton, which in turn must be fully predated on by larger organisms. Only in this way will the amount of waste descending to the sea bottom, be minimal and also the reductive (disease bringing) organisms. This is what we would call optimal health.

By contrast, a sick plankton ecosystem would see much of its productivity in phyto- and zooplankton go to waste. It would have a high reductive component, bringing a higher risk of disease.

The idea is that the ratio between the two components could be measured objectively in any sample of seawater. It would consist of sieving the net plankton (large phytoplankton + small zooplankton) out, and centrifuging the remainder. The dry biomass of the two compartments could be obtained, and a ratio established. Likewise the concentrations of oxygen and carbondioxide could be measured, the one being produced by the producers, the other by the decomposers.

Assuming that phytoplankton has a short life cycle, one could say by rule of thumb that a green sea is not being grazed sufficiently, giving rise to a high disease-bringing component. Visibly green or brown seas are likely to be also increasing the risk of disease. Thus the simple measure of visibility, well known to divers, may well be a good indicator of health.

Reader, please note that a simple and cheap technique (DDA) has been invented to measure the health of plankton and this can now be done by a 12-year young school student. With this techniqe we have shown conclusively that plankton can indeed become sick and murderous and that this kind of plankton has little food value.

1) Where the rock face faces the sun light, plants are found because they compete much better for space than invertebrate organisms. The polar diagram above shows in the blue lobe that the light underwater comes from above, even when the sun sets at the horizon. As a result, a steep slope suddenly loses much of the available light. The difference between sunlit and shaded sides of rocks is also rather large. It causes large shifts in plant and animal communities.

2) Wave exposure decreases rapidly with depth but also behind a rock which shelters its side turned away from the waves. Since large waves always arrive from the sea, the landward sides of rocks and islands are always predictably sheltered, allowing more fragile organisms to live.

3) Wave exposure is not always destructive, but may bring salvation where the environment is threatened by mud. Fine soil particles need calm water in order to be able to settle out, and wave action prevents this. Thus the rocks facing moderate wave action are in a better state than those with complete shelter. Wave action not only prevents sedimentation but also cleans sediment away.

Because of the above factors, the space underneath overhangs is the favourite place for sensitive invertebrate life, so easily killed by sedimentation. But even here the composition of communities can change suddenly.

4) To explain the finer points in what lives where, the plankton balance hypothesis becomes necessary. In clear waters the availability of food is important, and invertebrate life favours a place in the current but sheltered from wave action. The deep reef (below the photic zone) is rich in invertebrate life where currents prevail, but threatened by sediment in other places.
Areas of shelter and darkness, lacking currents (caves) can sustain only the most thrifty of invertebrate life, able to 'live off the smell of an oily rag'. They do not have adequate reserves to fight disease, so they are sensitive to the disease effect of denser plankton. In recent times, these places have also been attacked by unnatural sediment loads, resulting in direct suffocation and an increase in disease carrying microbes. As a result, caves and niches in the rock face, once carpeted in life, now stand barren as a testimony to ongoing degradation. But before sediment can be seen accumulating in crevices and on ledges, sensitive sponges and others disappeared because the plankton balance between food and disease became unfavourable for them.
 
 
 

f036734: This photo shows a sharp boundary between healthy and sick sponges, due to wave action. Currents rush in the top part of the photo, keeping the large grey sponge (Anchorina alata) healthy. But lower down, three of the same species of sponge are dying, For them the plankton threat was not matched by enough food for fitness to fight disease. (Arid Island)

f036015: An organ sponge (Callyspongia latituba) stands dead on a vertical wall, surrounded by other healthy invertebrate species like orange carpet sponges (Crella incrustans), white anemones (Actinothoe albocincta) and common sea urchins (Evechinus chloroticus). This photo was taken during an unusual period of clear water in a year that saw underwater visibility starkly reduced (May 2003). As a result of presumably 'sick' plankton conditions, these purple organ sponges were observed dead and dying. It could be explained that for them the balance between the good and the bad components in the plankton had tipped unfavourably, resulting in (slow) death. (Mimiwhangata)

Support for the hypothesis Once in 1991 and again in 1992 dense plankton blooms reduced the photic zone so severely and for such a long time that large areas of kelpbed died. This map shows their extent and severity. During a private expedition measurements were taken at the sample sites indicated. For more detail see enviro/habitat/survey93.htm.  The 1992/93 kelp dieoff was more severe than that of a year before, and we observed many organisms dying, apparently because of it. What makes this event so special is that it happened outside the Hauraki Gulf in an area of the sea which normally has clear water. The outlying islands and the north-eastern portion of Great Barrier are not normally threatened by excessive sedimentation. So the decline in sessile filterfeeders could be attributed to this single event consisting of a denser than normal plankton bloom. Amazingly, the plankton bloom was able to kill both plants and animals in two entirely different ways.

Support for the Plankton Balance Hypotheses was obtained only recently from our data of August 1993. Horizontally the severity of the plankton bloom as measured objectively by the amount of kelp death. To the left none, and to the right severe. The disappearance of the filterfeeders was measured by how many were left, in qualitative terms like few and many. Yet such inaccurate values were adequate for revealing relationships (dose-mortality) in these cluster diagrams. All sessile filterfeeders were affected by the plankton bloom, but each at a different rate. Note that the black points are from places that are influenced by mud and currents, around the Colville Channel  whereas the blue points were subject to a similar plankton bloom the year before (for details see the survey report).  Actinothoe (white anemone), Polymastia (yellow and orange nipple sponge), Tethya (pink and golden golfball sponges), Bryozoa (various species) were all missing where the kelp death was severe. Note that the pink golfball sponge (Tethya ingalli) proved to be more sensitive than the orange one (Tethya aurantium).

The plankton balance hypothesis explains why these organisms were affected and why each has a different sensitivity to such threats.

• Nutrient concentration gradients in fresh water as it entered the bay were stimulatory to phytoplankton blooms
• Species that showed distinctive seasonal and interannual successions dominated plankton blooms
• High relative dominance of bloom species was associated with significant reduction of phytoplankton species richness and diversity
• The blooms were associated with major reductions of infaunal and epibenthic macroinvertibrates, forcing a serious disruption of the food webs and losses of secondary production

More indications of support for the hypothesis may follow.

The hypothesis is attractive because it is:

• a simple theory/ hypothesis
• holistic: precise details are not required
• based on sound ecological principles
• provides another ‘limiting factor’ to consider
• explains many vexing questions
• makes interesting predictions
• encounters no conflicts with existing knowledge

Philosophically, the plankton balance hypothesis also has to answer the fine points why such an important factor has been overlooked by so many professionals in the field. We made the bold conclusion that a missing but important limiting factor had to exist to explain the many remaining paradoxes surrounding species distribution and the ill effects of plankton density. Then we began to look for one. For this hypothesis to be overlooked, it had to be:

• unique to the aquatic environment - otherwise we would have known about it.
• invisible - otherwise it would have been seen before.
• everywhere - because the unexplained paradoxes reigned everywhere
• important - otherwise the unexplained paradoxes would be trivial.
• simple and obvious - otherwise it would not have been overlooked.

Below follows a point by point summary of the observations explained by this new theory, and the predictions it makes. Although at the moment no conflicting observations or facts have been brought to light, they will in due time also be included as paradoxes contradicting the the hypothesis.

• ecosystem gradients and gradients of invertebrate communities
• explains biodiversity gradient away from large river mouths
• explains biodiversity gradient away from large populations
• explains biodiversity gradient away from the shore
• explains why remote islands are so different from the the main land.
• explains why changes in community structure can happen suddenly (living around the corner) and in time
• erosion and loss of soil; sewage and nutrients from farming; overnourishment
• explains why erosion is a major component of degradation
• predicts major problems from rapidly increasing erosion in the very recent past and future
• predicts major problems as human habitation densities increase
• invertebrate mortalities
• explains massive mortalities of many invertebrate species
• explains spring mortality, when plankton blooms most densely
• explains and predicts cyclical mortalities due to El Niño/ La Niña or Interdecadal Pacific Oscillation (IPO)
• explains and predicts habitat degradation
• explains scallop, Bluff oyster, mussel mortalities
• predicts mussel/oyster/salmon farm disease when decomposition on the sea bottom increases
• predicts mussel farm disease when plankton becomes 'sick'
• explains that plants are much less affected (this is not quite true, because some plants are indeed very sensitive)
• invasive species, where and when
• explains the prevalence of invasive species in the recent past
• predicts that this trend is increasing
• explains/predicts that invasive alien species establish in the most polluted places or in places of repetitive mortality
• explains/predicts prevalence for a certain phase in the IPO (El Niño phase)
• explains/predicts vertebrate mortalities
• vertebrate mortality due to viral, fungal and common infections
• explains fish mass mortalities from viral diseases
• explains parore (Girella tricuspidata) fungal warts and mortality
• predicts an increase in mammal and bird mortalities due to 'normal' infectious diseases
• predicts that animal pathogens are normal plankton catabolic organisms (viruses, bacteria, fungi)
• recruitment failures
• predicts recruitment failure due to dense plankton blooms
• predicts recruitment failure in certain phases of the IPO cycle (El Niño)
• explains mussel spat recruitment problems
• predicts that recruitment failures will become more common and more serious
• aquariums/ biology
• explains the kinds of disease found in aquariums
• explains why so many marine creatures have slimy skins
• explains why damage to the skin's slime layer can cause infections
• visible indicators
• explains that underwater visibility (viz) is a major indicator
• explains that sediment (mud/clay) increases the catabolic component
• explains that sturdy and sensitive organisms are both good indicator species
• potions for longevity
• predicts that chemicals beneficial for health are present in hardy organisms, particularly those surviving extreme degradation and those living inside caves
• paradoxes seemingly contradicting the plankton balance hypothesis