Harmful Algal blooms

Question 1

What is phytoplankton?

Answer 1

Some phytoplankton are bacteria, some are protists, and most are single-celled plants. Among the common kinds are cyanobacteria, silica-encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores

Question 2

What energy sources does phytoplankton use?

Answer 2

•Like land plants, phytoplankton have chlorophyll to capture sunlight, and they use photosynthesis to turn it into chemical energy. They consume carbon dioxide, and release oxygen. All phytoplankton photosynthesize, but some get additional energy by consuming other organisms (Heterotrophs and Mixotrophs).

Question 3

What does phytoplankton growth depend on?

Answer 3

•Phytoplankton growth depends on the availability of carbon dioxide, sunlight, and nutrients. Phytoplankton, like land plants, require nutrients such as nitrate, phosphate, silicate, and calcium at various levels depending on the species

Question 4

What other factors influence phytoplankton growth?

Answer 4

•Some phytoplankton can fix nitrogen and can grow in areas where nitrate concentrations are low. They also require trace amounts of iron which limits phytoplankton growth in large areas of the ocean because iron concentrations are very low.

Other factors:

• water temperature
• salinity
• water depth
• wind
• predators

Question 5

What is a phytoplankton bloom?

Answer 5

• the explosive growth of phytoplankton
• may cover hundreds of square km
• visible on satellite images
• may last several weeks but individual phytoplankton cells live only for a few days.

Question 6

What is a Harmful Algal bloom?

Answer 6

• (approximately 1 million cells per litre of seawater equals a “bloom”) and produce biotoxins, these events are termed harmful algal blooms or HABs.
• Some HAB species (Alexandrium spp.) can cause toxicity at low cell numbers of >50 cells per liter if they persist as their toxin is bioaccumulated into the lipid of shellfish
• These blooms can have deleterious effects on both other aquatic life and on those who depend on water for subsidies.
• Note: Large algal blooms which do not contain biotoxins, can also have a deleterious affect, especially on the benthos-> decomposition of dead algae can make benthosanoxic.

Question 7

How do algal blooms occur?

Answer 7

• right set of environmental conditions, i.e., nutrients or sunlight or temperature or a combination of these.
• provided on a local basis by natural run-off from the land or by human (anthropogenic) inputs (e.g., treated or untreated sewage, farming or urban gardening practices).
• “global” processes, such as El Nino-Southern Oscillation (ENSO) and Decadal Oscillations. These global processes can drive and cause huge weather and climatic occurrences such as higher than average rainfall (thus increasing runoff) and higher air and hence surface temperatures, all impacting surface and deep currents.
• –> These events may all impact the frequency and magnitude of oceanic HABs.

Question 8

How do algal blooms stop?

Answer 8

• finite amount of nutrients available for the phytoplankton.
• As nutrients are used up and assimilated into cell tissue, the growth of the cells begins to slow in response to declining nutrients.
• presence of toxic components in the water. (e.g. herbicides from land run-off, natural compounds - bacteria, fungi, other algae)
• some fungi produce “antibiotics” to ward off other competing microorganisms).
• The production of these control chemical (alleopathic) compounds may confer a survival benefit to an organism, allowing it to have a small niche the overall scheme of the water column -> Every now and then, one organism is able to outcompete its neighbors and become the “top dog”, which in the case of phytoplankton is what we call a “bloom”.
• Marine viruses have also been associated with bloom collapses.
• When times get tough-> form cyst (hibernation) -> circumstances change and algae comes out of cyst returning to vegetative state

Question 9

Hos does harmful algae move around?

Answer 9

• when algae forms cysts, they can be easily transported by both surface and deep currents over long distances.
• Ballast water exchange can transport cysts
• Aquacultural activities can also transport cysts e.g. mussel spat collection (Kaitaia spat)
• Eventually many phtyoplankton run out of nutrients, lose their buoyancy, and become part of oceanic “snow” -> might be a way that marine biotoxins (produced perhaps during stationary phase) become introduced into the benthic environment.
• creatures can then consume this toxic “snow” and accumulate toxins. Either through the active uptake of live, vegetative cells or perhaps withered dead cells, biotoxins can enter the food web.

Question 10

What are marine Biotoxins?

List the common ones their cause and symptoms

Answer 10

• produced by phytoplankton usually during HAB events
• some of the most potent toxins in the world and extremely dangerous (some toxins, doses at the microgram per kilogram level to kill)
• When enough toxin is accumulated in fish or shellfish, small amounts of cooked or raw tissue can kill a human.
• Paralytic shellfish poisoning (PSP) is caused by a group of chemicals called the saxitoxins and gonyautoxins.
• Symptoms of PSP can occur within 12 hours of consumption. (numbness and a tingling around the mouth, face, and extremities, followed by difficulty swallowing or breathing, headache, dizziness, and double vision)
• Amnesic shellfish poisoning (ASP) is caused by Domoic Acid in shellfish.
• Symptoms of ASP are mainly gastrointestinal (vomiting, diarrhoea etc), especially at low levels,
• about a quarter of cases experience neurological problems including memory loss that may be significant and permanent.
• Gastro-intestinal symptoms first appear within 24 hours and neurological difficulties within 48 hours
• Diarrhetic shellfish poisoning (DSP) is caused by Okadaic Acid and related compounds.
• Symptoms of DSP are diarrhoea, nausea, vomitingandabdominal pain.
• Acute symptoms occur within 12 hours and are usually of short duration.
• Neurotoxic shellfish poisoning (NSP) is caused by the consumption of shellfish contaminated by breve-toxins or brevetoxin analogs.
• Symptoms of NSP in humans include vomiting and nausea and a variety of neurological symptoms such as slurred speech.
• No fatalities have been reported but there are a number of cases which led to hospitalization
• Ciguatera is a foodborne illness caused by eating certain reef fish whose flesh is contaminated with a toxin made by dinoflagellates such as Gambierdiscus toxicus which live in tropical and subtropical waters.
• These dinoflagellates adhere to coral, algae and seaweed, where they are eaten by herbivorous fish which in turn are eaten by larger carnivorous fish.
• This is called biomagnification

Question 11

How are marine Biotoxins monitored?

Answer 11

• Monitoring of algal toxins involves assays and/or analytical or instrumental methodologies.
• They include in vivo bioassays using live animals (mouse bioassay) or in vitro assays, including:
• •Cytotoxicity assays (these can eliminate the need for live animals by using immortal cell lines)
• Receptor assays (in which binding affinity of a toxin is related to its potency)
• Immunological or structural assays

Question 12

What are mouse bioassays?

Answer 12

• Mouse bioassays measure the biological response of the whole animal, thus allowing correlation with human toxicity effects.
• They do not require expensive equipment or extensive sample cleanup procedures.
• Their main disadvantages are that they involve use of live animals
• require experienced personnel and careful standardization of assay conditions to obtain reproducible results
• cannot be automated
• show lower sensitivity than other methods, and provide no information on specific toxin composition.

Question 13

how can HAB species be identified and quantified more easily?

Answer 13

• Counting of HAB species in water samples is often done in conjunction with biotoxin testing.
• The primary reason is that there is usually a lag between when HAB numbers are increasing in the water column to when toxicity is observed in shellfish.
• Benefits: beaches can be closed to harvesting and aquacultural harvesting can be ceased until biotoxin testing has been done to check for toxicity.
• A major disadvantage is that just because a potentially toxic HAB species is present does not mean it is toxic
• counting HAB species in a background of other species can be difficult and also identification to species level can be very difficult.
• Whole cell assays: Fluorescent In Situ Hybridisation (FISH); lectins; cell wall antibodies
• Nucleic acid assays: Sandwich Hybridisation Assay (SHA); quantitative Polymerase Chain Reaction (qPCR)

Question 14

What is Fluorescent in situ hybridization (FISH)?

Answer 14

• Fluorescent in situ hybridization (FISH) is used on fixed intact cells that are either immobilized on a microscope slide or suspended in solution.

Question 15

What is sandwich hybridization?

What is its advantage?

Answer 15

• The sandwich hybridisation assay uses two oligonucleotide probes – a capture probe and a signal probe.
• The major advantage is that the assay is amenable to automation, is quick and is relatively cheap. In addition, it does not need intact cells to work.
• The major disadvantage is that it does not have the morphology of the target cell as a double check on specificity. In addition, the target molecule - rRNA can vary with the stage of cells physiological state making quantitative assessment difficult.

Question 16

What is quantitave PCR?

Answer 16

•Quantitative PCR in recent times has become the most widely used method for the detection of HABs.

• two primers (oligonucleotides) are used to amplify a region of the genome to produce many thousands of copies.
• copies are then detected by a fluorescently labelled probe (The signal is proportional to the number of starting molecules in the assay.

•If the target is ribosomal DNA or a single copy gene the number of molecules can be quantified

Question 17

What is the future of monitoring algal blooms?

Answer 17

• Remote sensing: airplanes; drones, satellites; smart buoys
• Airplanes, drones and particularly satellite imagery can provide information on the presence of blooms at large scales.
• However in most cases the images do not allow for species identification and in most cases blooms are non-toxic.
• Potentially the use of hyperspectral images can detect different pigments to allow some level of differentiation of phytoplankton type.

However this type of imagery is expensive, although as the cost of these camera systems reduce in cost and size reduces the possibility of deploying on drones is now feasible

•Smart buoys

-advantage is that they can collect data autonomously for long periods of time at high frequency levels

• The disadvantages are that they are expensive to deploy and maintain (biofouling, vandalism, storm damage). They are however invaluable for regular collection of data.
• Biological data has mostly been measurements of chlorophyl a which is a proxy for algal biomass, but does not provide species level determination.
• A new generation of smart buoys has now been developed and the most advanced has recently been commercialised – the Environmental Sample Processor (ESP)
• This system collects water samples, filters the samples and then processes them with a number of modules including: SHA, qPCR and ELISA for toxins. The results are relayed to shore either by radio or satellite in realtime for action as appropriate.