Where can I find out more about the Secchi App and this project?

  • Please see the two presentations for iOS and Android. Full instructions are also included with the App. 


Why is this project important?
  • The phytoplankton underpin the marine food chain and so we need to know as much about them as possible.

Who can use the Secchi App?

  • Secchi App is for seafarers and scientists.

Is the Secchi App free?

  • The Secchi App is free and it is free to take part, however, we do ask you to make a Secchi Disk.

Why won't the Secchi App install on my device?

  • The Secchi app will only install on a compatible device. The Secchi app works on all mobile devices that can obtain a GPS signal from satellites without requiring a network connection. For iOS devices this means the iPhone models 3GS and later, or 3G and 4G iPads. There are over 2000 compatible Android devices.

Do I need a network connection to use the Secchi App?

  • You do not need a network connection to use the Secchi app. Secchi stores the data you collect while at sea until you get a network connection when you will be prompted to upload your data to the database. If you wish, you can defer the upload until another time in case you have joined a roaming network.

What is a Secchi Disk?

  • A Secchi Disk is a 30 cm, flat, white disk attached to a tape measure or a rope, and weighted from below by a small 200 g weight.

Do all Secchi Disks have to be 30 cm in diameter?

  • Yes. It is very important that everyone uses a disk that is the same size to standardise the survey.

What is the Secchi Disk used for?

  • A Secchi Disk is used to measure the Secchi Depth. The Secchi Depth measures the turbidity of the water, which is influenced by the amount of phytoplankton in the water column.

What are phytoplankton?

  • Phytoplankton - also called microalgae - are microscopic plant-like cells and they are the sea's main primary producers.

How do you use Secchi Disk to measure the Secchi Depth?

  • With the sun behind you, you lower the Secchi Disk vertically into the water from the side of your boat. The point at which the disk just disappears from sight is the Secchi Depth.

Can a Secchi Disk be made from anything?

  • Yes. A Secchi Disk can be made from any material so long as it is white, or it is painted white.

How often should I take a Secchi Depth reading?

  • You can take a Secchi Disk reading as often as you wish, every day, once a week, twice a month, or just occasionally.

Where should I take a Secchi Disk reading?

  • You can take a Secchi Disk reading wherever you wish at sea so long as you cannot see the seabed and you avoid estuaries.

Should I measure the Secchi Depth at a particular time of day?

  • Yes. The Secchi Depth should be measured between 10.00 hrs and 14.00 hrs.

Should I remove my sunglasses?

  • Yes. Please do not wear sunglasses when you measure the Secchi Depth.

Should I clean the Secchi Disk?

  • Yes. It is important to keep your Secchi Disk clean so that its visibility does not change.

Who will use the data I collect?

  • The data you collect will help scientists around the world to understand the phytoplankton.

What happens if I submit a Secchi Depth when I have no network connection?

  • In this case, the data will be stored on your phone as a pending reading. When you next get a network connection you will be prompted to either submit or delay until later.

How much data am I uploading to the database?

  • Secchi data occupies about 4 kb per reading. Photographs occupy about 50 kb.

How long will the project run?

  • This project begins now and continues indefinitely into the future.

Will this really be the biggest global marine survey?

  • We hope so, but that is up to you.