Spring has sprung! The days are getting longer, and the weather is getting warmer as the first hints of summer peak through from winter.
However, for some areas the warmer water brings an unwanted visitor. For many divers the change in visibility and clarity caused by algae blooms puts a damper on their pre summer diving. But not for us, it means the winter wetsuits can be put into storage and warmer water and seasonal species are on the way!
What is an algae bloom and how do they occur?
Algae is necessary component of our ocean environments; they are a source of food and oxygen for many species. They come about when the environment changes to facilitate their growth.
Often in freshwater environments this is due to:
Nutrient run-off
Still or slow-moving water
Urban development impact
But in our marine environment the dominant factor is the seasonal increase in water temperature, alongside changing ocean current such as upwellings.
Why blooms reduce visibility:
When plankton or algae multiply rapidly, several things tend to happen:
The water becomes “greener” and more turbid as microscopic organisms scatter light and absorb certain wavelengths.
Less sunlight reaches deeper water, suppressing the clarity we tend to take for granted.
When the bloom dies off, decomposition consumes oxygen and can produce fine particles that further reduce clarity.
Some blooms may congregate as layers which may physically block light or cause it to filter differently.
What your dives might look like:
Reduced and/ or varied visibility, water may appear green and hazy.
Visibility will vary between dive sites. Mainland coastal, island coastal, pins and sites exposed to current will all differ.
‘Red tides’ along coastline and in currents will appear as a red hue of varying intensity.
The fish haven't got anywhere! Still an array of species and colours out there.
Blue sky and calm conditions, a spring classic!
What about bioluminescence?
Featuring in the same weather window is bioluminescent algae, appearing during warmer weather and when nutrient levels rise. A form of bioluminescent plankton, their chemical reaction is triggered by mechanical disturbance. We see this when the likes of waves, fish, swimmers, oars disturb the water surface.
Best time to see this is during calm, warm nights with as little light as possible. This includes reducing artificial light and ideally during a new moon when the sky is at its darkest.
Long story short, algae means the is getting warmer and summer is on its way. Don’t let the algae bloom doom you dive!