It descends on New Zealand every spring, some time in September or October. It’s the dreaded phytoplankton bloom, turning our normally beautiful blue seas into something green, murky and slightly toxic-looking. You could be mistaken for thinking Ebola had been announced in New Zealand the way you hear some divers talking about spring diving. There is an obsession with the visibility and whether it’s worth dropping into the water. As you pull up by boat to a dive site, divers peer uncertainly into the water, squinting, heads tilted sideways. Everybody is asking “how does the viz look?” And some are seriously thinking: should I have stayed home to clean the house and reseal the deck?
What is this phenomenon that can turn your normally hardy kiwi diver into a bad tempered couch-surfer? What is plankton?
"I’m not coming out of my room until the viz improves."
plankton n. the forms of organic life (chiefly microscopic) that float in the sea or fresh water.
Plankton is made up of many kinds of organisms. Phytoplankton, or plant plankton, are single-celled photosynthetic organisms which manufacture food using energy from sunlight and these microscopic buggers are important.
Te Ara, The Encyclopedia of New Zealand says:
Phytoplankton perform three main functions, crucial to life on earth:
- They provide nearly half of the earth’s atmospheric oxygen.
- They regulate carbon dioxide levels in the water and atmosphere.
- They are the founding organisms of aquatic food webs.
The most well known phytoplankton are microscopic algae. The distribution and quantity of phytoplankton depends on light penetration, the stability of water layers and the availability of nutrients. Around New Zealand there is usually a spring-time bloom of phytoplankton algae in surface waters. At this time, surface temperatures rise, sunlight hours increase and nutrients become abundant following winter cooling and the stirring action of storms. Phytoplankton grow and reproduce rapidly, doubling their population each day…
When this happens, the visibility underwater can go from good to bad, and even really, really, really bad. As a diver how do you survive this annual phytoplankton bloom?
- Accept that the visibility is what it is and decide to have a great dive anyway. Remember that you love diving. Your worst day diving still beats a day in the office. Bring your 'never say die' attitude. You’re not really going to let a bunch of single-celled organisms spoil your day in the water, are you?
- If you can’t see far, stop looking. In bad visibility forget about manta rays and whale sharks. Start thinking nudibranchs, octopuses, and kinky sponges. Don’t hover over the top of the kelp, pause and poke your head underneath. You’ll be amazed at what grows under a forest of kelp. There are seasonal types of invertebrates that bloom in spring for a couple of months and then disappear. Now is the only time of year you can see these creatures and they come in some crazy colours, shapes and textures. Share your discoveries with your buddy.
- Find a wall of colourful organisms and kiss it. I mean get up really close (but be careful not to damage it!). Dive sites like Magic Wall at the Poor Knights Islands are great for this. They are crawling with nudibranchs, sea spiders, amphipods and skeleton shrimps. The underwater world is full of bizarre alien creatures that are often overlooked. Take the time to check them out. [Remember that a gentle single finger push off a bare piece of rock can prevent mass destruction of a world of miniatures - frantic hand waving gestures to try and back away from a wall are not a great idea, try gently pushing off with one finger. Better still, learn to back kick and you can comfortably wall gaze for hours, hovering in and out at your leisure.]
- Underwater photographers – time to get experimental. The visibility can be widely variable from site to site and week to week at this time of year. Macro can be a safe option and there are usually loads of subjects to play with in springtime. But wide angle can be fun too. If the water is intensely green then look for ways to feature this element in your photos. You may have to think on your fins to capture extraordinary photos in 'ordinary conditions'. Get excited by the challenge.
- Keep it safe and practice your teamwork. If you’re diving in diminished visibility then it becomes much easier to lose your buddy. Now is a great time to brush up on lost buddy procedures. Work on your buoyancy, trim, finning techniques and visual awareness. These are important techniques for safe diving all year round. In bad visibility honing these techniques will help you keep your diving team tight, together and relaxed underwater. More fun for everyone.
Murphy’s Law applies to scuba diving: something epic will always happen on the dive you don’t do. Is your fear of bad visibility causing you to miss out on something awesome? Don’t let the plankton get you down.