Toxic Algae and Man-Sized Jellyfish

Once a swampy backwater of fewer than 20 million people, the Pearl River Delta—the southern swath of mainland China above Hong Kong—now has three times that population. Tens of millions more humans in the Pearl River Delta means many more toilets a-flush, pumping a steady gush of human waste into the South China Sea.
Read the full story at Quartz

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SCMP: Mainland sewage fuelling Hong Kong’s ‘red tides’

According to the SCMP, sewage from the mainland is fuelling an increase of harmful algal blooms – known as red tides – in Hong Kong waters.

Professor Ho Kin-chung, dean of the Open University’s school of science and technology and an expert on algae, told the SCMP the red tides were “fed” by nutrients flowing in from mainland waters to the east and west of Hong Kong.

“The economic boom across the border leads to more sewage discharge into the sea and rivers, and in the right seasons [the nutrients] come down to us. So this is no longer a local phenomenon but a regional one,” Ho said.

Within the last fortnight brown algae been spotted across the territory – off Lamma Island, Cheung Chau, Lantau and within Victoria Harbour.

Agriculture, Fisheries and Conservation Department staff said they had spotted red tides at fish culture zones within Tolo Harbour, Sha Tau Kok and Tai Mei Tuk, while a member of the public reported another at Pak Sha Wan in Sai Kung.

Most algae absorb nutrients such as phosphates or nitrates that are commonly found in cities’ wastewater. At the right temperature, well-fed algae will proliferate in a short period of time.

Ho said Hong Kong was sandwiched by the Pearl River in the west and Mirs Bay in the east and these were the two key origins of red tides in local waters.

As a result, Tuen Mun, Lantau, Tolo Harbour and Sai Kung were becoming increasingly prone to the phenomenon.

Recent reports of large amounts of seaweed being washed onto beaches in South Lantau should not be confused with red tides. Red tides are composed of free-floating (planktonic) algae, seaweed however are larger marine plants normally growing attached to the seabed, reefs or rocks.

A spokeswoman for the Agriculture, Fisheries and Conservation Department said it would announce today whether tests had found the algae off Lamma Island to be toxic.

Four red tides were also spotted in Hong Kong waters last week.
Three red tides at fish culture zones within Tolo Harbour, Sha Tau Kok fish culture zone and Tai Mei Tuk were observed by staff members of the Agriculture, Fisheries and Conservation Department (AFCD) during April 8 to 10. Another red tide was spotted on April 9 by a member of the public at Pak Sha Wan, Sai Kung.

None of the red tides were associated with the death of fish in these occurrences.  “The red tides at fish culture zones within Tolo Harbour and Tai Mei Tuk were formed by Gonyaulax polygramma, Prorocentrum minimum and Heterosigma akashiwo. The one at Pak Sha Wan, Sai Kung, was formed by Gonyaulax polygramma whereas the one at Sha Tau Kok fish culture zone was formed by Heterosigma akashiwo and Prorocentrum minimum. All the above algal blooms are commonly found in Hong Kong waters. Gonyaulax polygramma and Heterosigma akashiwo are non-toxic. Studies have shown that Prorocentrum minimum may produce toxin, but no such reports or associated fish kills have been recorded in Hong Kong,” a spokesman for the working group said.

Red tides are a natural phenomenon. The AFCD’s phytoplankton monitoring programme will continue monitoring red tide occurrences to minimise the impact on the mariculture industry and the public.

In 1998, a red tide killed 80 per cent of the stock at Hong Kong fish farms.

 Source: SCMP 17/04/2014 and AFCD Press Release 11/04/2014

Global Citizen Science – Introducing the Secchi App

Screenshots of the Secchi App
Screenshots of the Secchi App

SecchiApp2Calling all budding marine biologists!
The University of Plymouth has developed an app that let’s you directly contribute to science by recording phytoplankton densities with the aid of a simple device called a Secchi disk – which you can make at home – and their free iPhone or Android app.
Phytoplankton are tiny floating algae that soak up carbon dioxide and nutrients and use sunlight to convert them into carbohydrates, proteins and fats to grow and release oxygen at the same time. Phytoplankton is very important for climate change because when they die they settle down to the sea bed either directly or by being eaten and then pooped out by animals. This process of binding carbon dioxide from the ocean and burying it layer upon layer of sediment on the ocean floor is often called a carbon sink.
Quite apart from this phytoplankton is also the basis of the marine food chain, so almost all other ocean creatures depend on it.
But many researchers have claimed to find a decrease in phytoplankton levels. But now you can help in what may become the worlds biggest phytoplankton study and help find out what is really happening with phytoplankton worldwide.
The app shoes you how to make a simple device called a Secchi disk – basically a flat circular disk lowers into the water by a rope. You then lower thie disk down into the water until it just disappears from view and record this depth – this is the ‘Secchi depth’. So basically you are measuring underwater visability in the vertical dimension.

how a secchi disk works
The Secchi disk measures the visibility of the water column in the vertical plane and this measurement serves as a crude measure of plankton density.

This is a so-called proxy for phytoplankton density in the water – it’s not the actual measurement of phytoplankton density but a measurement that is very strongly correlated to it, because phytoplankton is the main cause of visibility levels. So by measuring the visibility we can indirectly infer how dense the phytoplankton is in the water.
The app has full instructions on how to make a Secchi disk and how to make the measurements. So if you have access to a boat, download the app, and get busy as doing some ‘citizen marine biology’!