Category Archives: Red Tides

What is plankton, marine biology of plankton, what are the different types of plankton occurring in Hong Kong waters, how to observe plankton, why is plankton important.

HKD 4.3M Grants Won for Tolo Harbor (吐露港) Biodiversity & Ecology Research

More than 25 local marine biologists have been awarded a grant that will enable them to study the marine biodiversity and ecology of the Tolo Harbour and channel.

Tolo Harbor is a semi-enclosed body of water in the northeast of Hong Kong linked to the sea only by the narrow Tolo Channel. The Tolo Channel and Harbor were infamous in the 1980’s for terrible water pollution, fould smells and red tides. A rapid expansion of urban areas on the firnge of Tolo Harbor with direct, untreated sewage discharges into the Harbor caused large scale eutrophication. The sewage outfalls provided nutrients feeding massive algal blooms which subsequently died and their decomposition by microorganisms used up so much oxygen that the water and sediment became anoxic, killing fish and many other marine organism (again feeding oxygen demand form decomposition) and causing foul smelling water. The problem was made much worse because Tolo Harbor is not very well flushed with new oxygenated water from the sea. It was eventually improved by providing proper modern sewage treatment and recognizing the particular vulnerablility of the area to eutrophication.

The HK$4.3 million will benefit the Joint University Consortium for Biodiversity, Ecology and Conservation of Marine Ecosystems and comes via the Environment and Conservation Fund (ECF). The ECF was established by the government in 1994 as part of its long-term commitment to environmental protection and conservation and received an injection of $5 billion in 2013, to serve as seed money generating an annual investment returns to support green projects and activities. The ECF has so far funded over 4,290 educational, research, and other projects and activities in relation to environmental and conservation matters.

Despite the funding being delayed for about two years, the proposal was approved last month and the 18-month project will commence later this year. The first stage of the two-phase study is aimed at finding the current ecological status of the area as well as the economic value of marine resources. The team will establish a comprehensive species database of the area. Kevin Ho King-yan, a senior research assistant at the School of Biological Sciences at the University of Hong Kong, said the proposal was aired at least two rounds of interviews, possibly because of the large amount of money required.

“Usually, project funding proposals to the conservation fund average around the hundred thousand mark, but this time it is in the millions,” he said. The announcement comes after an international conference, jointly organized by the Swire Institute of Marine Science and the University of Hong Kong School of Biological Sciences, kicked off at HKU yesterday.

More than 280 participants from 26 countries have come together for the four-day conference to discuss issues such as coastal development and marine conservation. More than 20 marine scientists from overseas and the mainland are attending. Organizing committee chairman Kenneth Leung Mei-yee said experts from across the globe need to work together to map out a plan to protect marine biodiversity. “We need experts from all different sectors to join hands together to uncover what we have and how we can protect them and how we can make sustainable use of these resources,” Leung said.

Note: The Hoi Ha Wan marine park – noted for its corals – is located at the seaward mouth of the Tolo Channel.

Source: The Standard 2nd June 2015

Ciguatera: Another Good Reason To Avoid Large Reef Fish

Hongkongers love their seafood – a quick glance at the local restaurants scene will more than proove that point. Per capita HK has one of the highest seafood consumption rates in the world. For many locals, expats and tourists a trip to Sok Kwu Wan on Lamma for a seafood meal would not be complete without a big steamed grouper (also called garoupa). But aside from concerns about over-fishing and sustainability, eating these fish can be a health risk, too. That is because these large reef fish are more likely than others to give you ‘Ciguatera fish-poisoning‘. Ciguatera (‘see-gwa-terra’) is a food born toxin harbored by large reef fish. Originally the toxin (CTX) comes from a microscopic organism called Gambierdiscus. Gambierdiscus is a dinoflagellate – a single-called organism with a thin shell and two beating hair-like whips called ‘flagella’ that move it through the water.

Marine plankton Gambierdiscus toxicus can produce ciguatera toxins (Image taken by Dr. Maria A. Faust, Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington D.C., U.S.A.)
Marine plankton Gambierdiscus toxicus can produce ciguatera toxins (Image taken by Dr. Maria A. Faust, Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington D.C., U.S.A.)

Gambierdiscus sticks to coral, seaweed and algae in tropical and sub-tropical regions (like HK) and is eaten by smaller fish feeding on the coral and algae. These fish in turn are eaten by predator fish and so the toxin moves up the food chain, finally accumulating in its greatest concentration in the large reef fish.

Figure_2_1_sTissues like the roe (fish eggs), head, skin and insides are particularly good at concentrating CTX. CTX is odourless and tasteless and very heat-resistant – so conventional cooking will not destroy or inactivate the toxin.

So how bad is CTX poisoning?

Ciguatera causes a combination of gastrointestinal, neurological and cardiovascular symptoms. The gastrointestinal symptoms include nausea, vomiting, abdominal pain and diarrhoea. That might not be that bad, right? But the cardiovascular symptoms are more serious: a slowing of your pulse to under 60 beats per minute (sinus bradycardia) and low-blood pressure (hypotension) which can be life-threatening but can also be treated. The common neurological symptoms include a sensation of tingling, tickling, pricking, or burning of a person’s skin, numbness of lips, tongue and the four limbs, reversal of hot-cold sensation, muscle pain, muscle weakness, joint pains, itching and fatigue and these symptoms can last for weeks or even months.

CTX in Hong Kong

Because ciguatera is a matter of food safety the HK government requires by law that the reporting of all diagnosed or suspected cases and as a result there are some good statistics on ciguatera in Hong Kong. From 1988 to 2008 there were between 3 and 117 outbreaks annually causing between 19 and 425 people to fall ill. Groupers were responsible for almost 60% of those cases, with snappers causing another 32%. The rest of the cases were caused by moray eels, triggerfish, parrot fish and other reef fish. Past records of ciguatera fish poisoning cases in Hong Kong show that the following fish are more likely to contain ciguatoxins: Moray Eels, Potato Groupers, Speckled Blue Groupers, Tiger Groupers, High Fin Groupers, Hump Head Wrasses, Areolated Coral Groupers, Black Saddled Coral Groupers, Lyretails, Black Fin Red Snappers, Flowery Groupers and Leopard Coral Groupers.

HK Ciguatoxin poisonming cases 1989 – 2008

The most recent suspected case was in September 2014 when a 38-year old man became ill. Before that 19 people aged between 23 and 71 became ill after a shared seafood meal on Lamma in June 2013.

Ciguatoxin cases reported in HK
Ciguatoxin cases reported in HK

Ciguatoxin is very difficult to detect in fish samples so quality control measures are very difficult to implement and suspected cases are often not confirmed because either a sample of the eaten fish is not available anymore or chemical test are not able to detect the ciguatoxin well enough.

How to avoid CTX poisoning

To avoid this nasty CTX poisoning your best bet is to avoid large reef fish especially groupers. Any reef fish over 2 kg in weight is especially risky. And if you do chose to eat such fish stay away from the high-risk body parts of head (sorry, no more sought-after cheek meat), insides, skin and roe (eggs).

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The HK government’s guidelines for the prevention of CTX poisoning are:

  • Buy coral reef fish from reputable and licensed seafood shops. Do not buy the fish if in doubt.
  • Consume less coral reef fish, especially marine fish over three catties (1.5 kg).
  • Only eat small amounts of coral reef fish at any one meal and avoid having a “whole fish feast” in which all the dishes come from the same big coral reef fish.
  • Avoid eating the head, viscera, skin, and roe of coral reef fish which usually have higher concentration of toxin.
  • When eating coral reef fish, avoid alcohol, peanuts or beans as they may aggravate ciguatera poisoning.
  • If you are suffering from ciguatoxin poisoning you should refrain from coral reef fish. The intoxication will sensitize patients and they will suffer from ciguatoxin poisoning even if they are exposed to a lower concentration of toxin.
  • Seek medical treatment immediately when symptoms of ciguatera fish poisoning appear. The unfinished fish should be brought to FEHD (Food & Environmental Hygiene Department) for testing.
  • There is HK Centre for Food Safety Info-Poster on Ciguatera Fish-Poisoning Prevention you can download here.

 

Interesting side notes
  • Ciguatoxins are actually a group of about 20 chemically related toxins. The most potent of these is Pacific-CTX-1 (PCTX-1) which is found in the Pacific Ocean.
  • Ciguatera fish-poisoning was described as early as 600 BC by the Chinese and Captain James Cook’s log details effects felt by his crew on a voyage to Tahiti in 1774.
  • The clinical description of the syndrome came from Portuguese biologist Don Antonio Parra and were published in Havana in 1787. Parra said, “some [fishes] cannot be eaten because they are `ciguatos’ and some others are suspicioned because they carry with them the poison..I can speak from personal experience, because on 15 March 1786, twenty-two of us ate a Cubera, and we all developed those symptoms to a greater or lesser extent. All were prostrated, but each one was suffering various types of discomfort, although the most common type of difficulty was the extreme exhaustion accompanied by more or less pain. I observed that I had extreme difficulty in breathing, which caused great pain and a feeling of suffocation. My tongue became rough and I developed a sour taste in my mouth.”
  • There is commercially available test kit for consumers called Cigua-Check®, however studies have shown it to have a lower than desired reliability and I do not encourage its use over the HK government’s advice cited above.

Noctiluca scintillans Makes Global Headlines for HK

As reported by Apple Daily today, a recent bloom of the bioluminescent organism Noctiluca scintillans – often known as “Sea Sparkle” – and a frequent cause of red-tides in Hong Kong (recent posts here, here and here ), has occcured in the sea near Tai Po. The bloom has attracted more and more people hoping to capture the bioluminescence on camera. Some of the images and video have even made international media reports.

But the sudden influx of night-time visitors is causing some aggravation to villagers who are complaining about the noise nuisance. Many people have also been throwing rocks into the sea to agitate the single-celled organisms into sparkling, which is harming the local ecology.  While one or two stones thrown hardly make a difference, several hundred rocks hurled into the sea does create some damage. If you are reading this and planning to go and see the blooms, please DO NOT THROW STUFF IN THE SEA, NOT EVEN STONES. If you really want to see the sparkle then wade in to use your hands or a stick to agitate the water – but I don’t advise this either.

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Some villagers have now taken to blocking beaches. Up to 100 visitors are coming to the beaches and cars are now blocking lanes causing a major disturbance to village life.

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Advice on viewing Noctiluca scintillans in Hong Kong:

1. DO NOT THROW ANYTHING INTO THE SEA. If you want to agitate the bloom use a stick or branch to swirl the water. Or just watch out for waves which will do the same.

2. Respect local villagers. Do not be noisy and obnoxious. Do not block lanes

3. DO NOT LITTER. TAKE ONLY PICTURES AND VIDEO, LEAVE NOTHING BEHIND.

4.  Use a tripod and a slow shutter speed and high sensitivity (ISO) for long exposures to capture the full sparkle.5. If you can tame your urge to see the sea sparkle in person please do, it would really help the environment (and the villagers). You can just enjoy the images and videos floating around the internet,for example this (probably copied) video:

Click here to see irresponsible behaviour in the Apple Daily article ( so you know what not to do).

Noctiluca scintillans – Jekyll & Hyde of Plankton

This week red tides have been reported all across the western half of Hong Kong including Discovery Bay, Peng Chau, Mui Wo, East and West Lamma Channel. The culprit was once again the plankton species Noctiluca scintillans – neither fully plant not fully animal. It’s a single-called organism from a group called dinoflagellates. They consist of a bubble-shaped cell with two whips called flagella – that propel them through the water.

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Though Noctiluca eats other plankton it doesn’t always kill what it eats: sometimes it leaves algae intact and stores it in little bubbles in its body (cell) where the algae make sugars that leak out and feed Noctiluca while the waste produced by Noctiluca feeds the photosynthesis of the preyed on algae – a process known to most as symbiosis and also found in tropical corals. However Noctiluca can also just eat the algae. Why and how it decides to eat or farm the algae is not really clear.
Noctiluca is a well known and non-toxic local red tide species and its occurrence is not necessarily a sign of pollution, but entirely natural. What is perhaps not natural is the size of the bloom, though. This could well point to agricultural fertiliser run-off and sewage effluent particularly from the fast growing population of the Pearl River Delta (PRD).

Images of the recent red tide at Discovery Bay North:
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Noctiluca has however a redeeming feature – bioluminescence! That beautiful sea sparkle of iridescent blue that night divers in the tropics often sea or beach goers see in the breaking waves at night. So blood-red tides on the one side and beautiful sea sparkle on the other, Noctiluca is the Jekyll and Hyde of HK’s marine environment.

Long exposure image of a Noctiluca scintillans patch (cm via WikiCommons):

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If you would like to know more about Actual toxic red tides in Hong Kong here is a little TV news documentary from 2013 I found on YouTube:

Dramatic Images of Shenzhen Red Tide

The Shanghaiist (Nov 26, 2014) reports that on Monday (24/11/2014), guests at the Dameisha Sheraton Resort in Shenzhen were witness to a red tide, as the sea water at the nearby beach turned a deep pink color, stretching for hundreds of meters. Dameisha is located in Mirs Bay just a few kilometres to the northeast of Hong Kong
According to the Shenzhen Marine Environment and Resources Monitoring Center, the red tide in this instance resulted from a non-toxic, algal bloom. However, despite center’s insistence that the bizarrely coloured water is harmless, a restriction on swimming and direct contact with the water has been advised.
This is not the first, and probably not the last, case of strangely colored water appearing in China.

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The red tide cause was identified as the non-toxic plankton species Karenia brevis (according to this article). Aerial photographs printed by the daily mail show the extent of the bloom. Only two problems: 1) Karenia brevis is native to the Gulf of Mexico, 2) it is toxic. In fact HK AFCD does not even list this species in its red tide database, which would be odd since it has been monitoring red tides in Hong Kong waters for over 20 years…
So once again a tabloid (the UK’s Daily Mail) has not done its research properly.

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HATS and Mullets – Victoria Harbor

This week I spotted the largest school of fish I have ever seen in Hong Kong. The grey mullets (Mugil cephalus) were attracted to a submarine seawater cooling outflow pipe that was discharging a grey liquid into the sea in western Kowloon. Each of the fish in the video below is 30-50 cm in length and I estimate there were at least 1000 of them.

I often see large mullets in that area. They regularly leap several feet into the air which is quite a spectacular sight. I have also seen an old angler at the Central ferry piers catching a 40cm mullet to the raucous applause of about 30 onlookers. The thing is the fish wasn’t hooked through the mouth but through the fin (quite a skill!) because it was swimming at the surface gasping and dying…
The behaviour of leaping out of the water according to some sources is a method mullets use to get more oxygen by storing air in their bodies so they can dive down into anoxic or low-oxygen water layers to catch prey others can’t. Grey mullets are known to be hypoxia-tolerant meaning they can tolerate low-oxygen environments better than other fish.

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And here is another video of a large mullet just meters from Discovery Bay beach. The way it is gasping at the surface while swimming in its side is just how the fish was behaving which I saw caught at Central ferry pier.

So what does it mean if there is a large aggregation of fish which are known to be tolerant of low-oxygen environments and which are exhibiting low-oxygen behaviour? It’s a pretty good sign of a lack of oxygen – duh! What causes low oxygen in the sea? Nearly always eutrophication – the process whereby excess nutrients from normally man-made sources cause microscopic algae known as phytoplankton to grow into large blooms (and sometimes red tides). When these inevitably die off the mass of dead material on the seabed decomposes using up oxygen until there is so little that the seabed and lower depths become so-called dead zones (anoxic zone) where very few hardy species can survive.
So I suspected illegal waste-water discharge and made a report to the EPD (Environmental Protection Department) online including the above video (you can also report pollution via the government telephone hotline 1823).
Say what you want about the HK government, the civil service works! They followed up with a site visit to test the water and issued an order to the building management to repair their outflow pipe. Apparently the pipe was seawater cooling air conditioning outflow, but was discharging wastewater as well. Two days later after the problem was fixed and the fish were gone!

(Note: grey mullet is a very popular food fish in southern China and you will see it even in most supermarkets. But the vast majority is farmed – in case you were worried about your fish being from sewage outfalls!)

So what have HATS got to do with it?
HATS stands for the Harbour Area Treatment Scheme, a large sewage and wastewater treatment scheme designed to clean up HK’s notoriously filthy harbour. Setup in 2 phases, the first phase was successful enough to reduce the concentration of sewage to levels acceptable enough to allow the return of the New Year’s Cross Harbour Swim event. The annual event sees swimmers cross 1.89km from Lei Yu Mun’s Sam Ka Tsuen pier to Quarry Bay Park pier. First held in 1911 the event was stopped in 1978 because of health concerns.
However, in 2011 the EPD announced that water quality in the harbor, particularly in the eastern section where the race took place, had “shown significant improvement” and E. coli levels had decreased by 95 percent since 2001. Yet, the data from the EPD Shortly before the restarted race revealed that E. coli levels in the harbor were still twice the maximum acceptable level at Hong Kong bathing beaches. But it was still a big improvement.

The 2011 Cross-Harbour Swimming Race

The sewage levels are evaluated by measuring the concentration of the common gut bacteria Escheria coli(E. coli) in the samples as a proxy for all the other gut inhabiting and potentially dangerous bacteria and viruses in sewage.

However,the planned second phase of Hong Kong’s Harbour Area Treatment Scheme (HATS) has recently been put on indefinite hold. The upgrade would have boosted the capacity of the treatment works to remove nutrients such as phosphates from effluent. This would have reduce eutrophication and helped rehabilitate the dead zones. Excess phosphates are also linked to increases of toxic algal blooms.

Officials said the current chemical-based treatment system was enough to meet most water quality objectives and stressed the upgrade to biological treatment was not “critical” at this stage. The planned upgrade would deliver “only marginal improvements” to water quality in western Victoria Harbour and bring little benefit to near-shore pollution. Their priority was to cut off improperly connected pipes and crack down on unlawful discharges into the harbour off Central and Wan Chai.
When I first read that I was highly sceptical and thought the government was just trying to save money. But having seen illegal discharge from a major shopping mall and office complex directly into the Harbour I now think they actually have a very good point!

The HATS scheme overview

Denying the scheme was declared dead, assistant director of environmental protection Amy Yuen Wai-yin said that in terms of E coli levels close to the harbour’s shores, the upgrade was “not an answer”, citing water quality modelling results. The cost of the upgrade, according to the latest estimate based on 2012 prices, has almost tripled from the 2004 estimate of HK$11 billion to up to HK$30 billion. Perhaps then they are right to concentrate on cleaning up the illegal and accidental discharges of wastewater before tackling the finer points of more advanced clean up.

Jonathan Wong Woon-chung, another council member, said officials should clarify to what extent illegal discharges and improperly connected pipes contributed to water pollution. He also questioned whether the upgrade would have the intended effect, as improvements might be offset by cross-border pollution.

As a side note, the Kai Tak nullah, has been renamed Kai Tak river and has seen the return of grey mullets. This drainage channel in the old airport area is a catchment for several rivulets from the foothills of the Kowloon mountains, but was surrounded by rapidly growing factories and homes from the 1960’s to the late 1980’s which discharged all their effluent into it. It was so badly polluted and foul smelling that at one point there was a plan to completely cover it up and make it subterranean! Luckily science prevailed in the planning and there is now a scheme to remediate and green the area and especially the river. Obviously this wi take years, but the effort seems to already be beating fruits. See the project website here for more details.

The former Kai Tak Nullah now Kai Tak River at Tung Tau Estate
The former Kai Tak Nullah now Kai Tak River at Tung Tau Estate

Red Tides, Fish Kills and iPhone Apps

Today I snapped a couple of images of some pretty right red tide patches in Discovery Bay. But what on earth is it that makes the water go red like this and is it dangerous?

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Floating patch of red tide in Discovery Bay 4/6/2014

Red tide is the collective name for phytoplankton blooms that tend to colour the water. Phytoplankton is made up of microscopic plants that drift through the sea. When conditions are right (mostly when there is nutrient-rich water and a stable water column) some species of these micro-algae form red tides. Depending on the pigments, the massive growth of algal cells may turn the water into pink, red, brown, reddish-brown, deep green or other colours.

"Pink" Red Tide on Tai Pak Beach
“Pink” Red Tide washing ashore on Tai Pak Beach in Discovery Bay 4/6/2014

 

Red tides are a relatively common sight in Hong Kong with 20-30 reports a year. The immediate reaction from most people is to think that they are the result of some terrible pollution. In fact the phytoplankton species are perfectly natural and normally occur in Hong Kong waters, but under certain conditions they can grow faster and form patches on the sea surface which we call ‘blooms’. Phytoplankton blooms by different species occur all over the world and are often seen by satellites with colour sensors.

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Bloom of the phytoplankton species Emiliania huxleyi in the English Channel as seen from space by a satellite. The light blue comes from the seawater and the white calcium shell of the algal species.

Some red tides produce natural toxins, and can cause depletion of dissolved oxygen or other harmful effects, and are generally described as harmful algal blooms (HAB). The most conspicuous effects of these kinds of red tides are the deaths of marine and coastal species of fish, birds, marine mammals, and other organisms. This happens either as a direct effect of the toxins produced or because of oxygen depletion (known as hypoxia) which happens when the algae die and bacteria consume all the oxygen in decomposing the dead algae.
Only some species involved in red tides however are toxin-producing and cause fish kills. The bioluminescing species Noctiluca scintillans which I wrote about in an earlier post, is not toxic but still can cause red tides.
For Hong Kong this is an economic concern because of the many fish farms and aquaculture areas. When a toxic red tide drifts into a fish farming zone only early warning will help the farmers avoid large economic losses from fish kills by temporarily evacuating their fish cages or transferring their fish to tanks.
The Agriculture, Fisheries & Conservation Department (AFCD) of Hong Kong runs a red tide monitoring network which relies partly on fish farmers and members of the public.  The AFCD follows up reports by taking samples from the red tides and identifying the contributing species under the microscope to determine the risk to aquaculturists and the public. The majority of the reports are caused by non-toxic species. If you would like to know more about the network, the AFCD now has a fantatsitc  app for iPhone and Android (pictured below) with weekly updates and the functionality to report red tide sightings (which I proudly did today) with this new app, including submitting  pictures. (I would also recommend some of the other Hong Kong apps for marine enthusiasts out there:  HK Geopark, Wetland Park, Reef Check, Red Tide Information Network and the WWF Seafood Guide).

 

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The AFCD’s “Red Tide” App for iPhone (also for Android). You can get weekly updates and also report red tide sightings. Available in Chinese (traditional and simpliefied) and English.

 

The AFCD started to record the occurrences of red tide since 1975. From 1975 to 2013, a total of 875 red tide incidents were recorded in Hong Kong waters. Amongst these incidents, only 27 were associated with fish kills.

77 algal species have formed red tides in Hong Kong, but majority of them are harmless. 19 of these species are considered harmful or toxic. Amongst these harmful/toxic algal species, only 5 of them caused fish kills and the other two caused contamination of shellfish by toxin in Hong Kong. The red tide associated fish kill events were mostly recorded in the 80’s and early 90’s.

So are there dangers to human health? If a red tide is identified as a harmful algal bloom (HAB) – then, yes, there is a risk:
The consumption of shellfish (e.g. mussels, clams) is one of the most common ways for algal toxins to impact human health. Each species has it’s own toxin so the health effects they cause are also varied. One example is Ciguatera fish poisoning. This type of fish poisoning is caused by eating fish that contain toxins produced by a the marine microalgae Gambierdiscus toxicus, which has been recorded in Hong Kong waters. Barracuda, black grouper,blackfin snapper, king mackerel, groupers and any large predatory fish can carryciguatoxins. People who haveciguatera may experience nausea, vomiting, and neurologic symptoms such as tingling fingers or toes. They also may find that cold things feel hot and hot things feel cold.Ciguatera has no cure. Symptoms usually go away in days or weeks but can last for years. People who haveciguateracan be treated for their symptoms. In Hong Kong with its rapacious appetite for seafood, ciguatera fish poisoning occurs quite frequently. For example, in 2004 it made up 7.9% of all food poisoning cases recorded that year. In June 2013, fourteen men and five women, aged 23 to 71, fell ill with ciguatera poisoning after eating coral reef fish at a restaurant in Sok Kwu Wan (Lamma Island). The fish in this case actually came from the Pratas/Dongsha Islands out in the South China Sea. Ciguatoxin’s is very stable, so cooking, drying or refrigerating fish will not destroy the poison. There is also no effective way to test fish for ciguatoxin, yet. If you want to play it safe avoid large predatory fish like tuna, grouper and others alltogether (they are mostly overfished already, especially blue-fin tuna, so you would be doing the planet a big favor).

So eating shellfish or fish which has been exposed to HABs is the main danger to humans. There are instances of skin irritations and breathing difficulties after direct human exposure to HABs but these are rarer and not as well understood. So to be absolutely safe, I would advise you to avoid contact with red tides – no swimming in, diving under or touching them!