Lake Ontario Whiting NASA Satellite Image

A whiting event is a phenomenon that occurs when a suspended cloud of fine-grained calcium carbonate precipitates in water bodies, typically during summer months, as a result of

photosynthetic Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...

microbiological activity or sediment disturbance. The phenomenon gets its name from the white, chalky color it imbues to the water. These events have been shown to occur in temperate waters as well as tropical ones, and they can span for hundreds of meters. They can also occur in both marine and freshwater environments. The origin of whiting events is debated among the scientific community, and it is unclear if there is a single, specific cause. Generally, they are thought to result from either bottom sediment re-suspension or by increased activity of certain microscopic life such as

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...

. Because whiting events affect aquatic chemistry, physical properties, and carbon cycling, studying the mechanisms behind them holds scientific relevance in various ways.

Characteristics

Whiting event clouds consist of calcium carbonate polymorphs; aragonite tends to be the dominant precipitate, but some studies in

oligotrophic An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates of ...

and mesotrophic lakes show

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

is favored. Whiting events have been observed in tropical and temperate waters, and they can potentially cover hundreds of meters. They tend to occur more often in summer months, as warmer waters promote calcium carbonate precipitation, and in hard waters. Whitings are typically characterized by cloudy, white patches of water, but they can also be tanner in hue in very shallow waters (less than 5m deep). In some cases, the whiting might be cryptic (not visible at the surface), but still generate calcium carbonate. These shallow water whiting events also tend to last less than a day in comparison to deeper water events that can last for several days up to several months. Regardless of the event's lifespan, the clouds it produces increase turbidity and hamper light penetration.

Potential causes

Some debate exists surrounding the exact cause of whiting events. And although much research exists on the subject, there is still no definitive consensus on the chemical mechanisms behind it. The three most common suggested causes for the phenomenon are: microbiological processes, re-suspension of marine or bottom sediments, and spontaneous direct precipitation from water. Of these three, the last has been ruled unlikely due to the unfavorable reaction kinetics of spontaneous calcium carbonate precipitation. It is also worth noting that it may be possible for more than one of the aforementioned factors to contribute to whiting events in the same region.

Microbiological activity

Substantial findings indicate

picoplankton, pico

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

, and

activity creates favorable conditions for carbonate precipitation. This link arises as a result o
planktonic blooms
being observed coinciding with the events. Subsequently, via photosynthesis, these organisms uptake inorganic carbon, raise water pH, and alter water alkalinity, which promotes calcium carbonate precipitation. The thermodynamic influence of inorganic carbon on whiting calcium carbonate production is shown in the equation below. Furthermore, cases exist in which the type of calcium carbonate found in the whiting cloud matches the type found on local cyanobacteria membranes. It's hypothesized that the extracellular polymeric substances (EPS) these microorganisms produce can act as

seed crystal A seed crystal is a small piece of single crystal or polycrystal material from which a large crystal of typically the same material is grown in a laboratory. Used to replicate material, the use of seed crystal to promote growth avoids the otherwi ...

s that provide a start for the precipitation process. Current research on the specifics of these EPS and the exact physiological mechanisms of the microorganisms' carbon uptake, however, are limited.

2 HCO3- (aq) + Ca^2+ (aq) <=> CaCO3 (s) + H2O + CO2

Sediment re-suspension

In shallower waters, evidence supports that activity of local fisherman and marine life such as fish and certain shark species can disturb bottom sediments containing calcium carbonate particles and lead to their suspension. In addition, as microorganisms impact water chemistry in observable ways and require certain nutrient levels to thrive, whiting events found occurring in nutrient-poor waters where no significant alkalinity difference exists between whiting and non-whiting waters support the idea of sediment re-suspension as a primary cause.

Relevance

Whiting events have a unique effect on the waters around them. The fact that calcium carbonate clouds increase turbidity and light reflectance holds implications for organisms and processes that depend on light. In addition, whiting events can function as a transport mechanism for organic carbon to the

benthic zone The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning " ...

, which is relevant to nutrient cycling. The cyanobacteria abundant clouds also hold the potential to act as a means to study the microorganism's role in carbon cycling (especially in relation to climate change) and their possible role in finding petroleum source rocks.

Characteristics

Potential causes

Microbiological activity

Sediment re-suspension

Relevance

References

Further reading