26 February 2023

If, like me, you live far from the ocean you may never have seen breaking waves glow blue at night. This bioluminescence is caused by single-celled organisms floating in ocean surface water whose defense mechanism creates blue light when they feel threatened.

Bioluminescence is relatively rare on land (think fireflies and fungi) but is common in the ocean where 76% of the organisms can create their own light through a chemical reaction between oxygen and the enzyme luciferase. The color is predominantly blue, the wavelength that travels furthest in water, and is a useful adaptation in the deep where sunlight cannot penetrate below 200 feet.

The glowing blue waves pictured above are created by dense populations of marine plankton called dinoflagellates. During the day they color the water red — a “red tide.”

Some are toxic but in San Diego in 2011 the organism was identified as harmless Lingulodinium polyedrum so it was safe to swim. ( Lingulodinium polyedrum might be top center below.)

Dinoflagellates automatically glow to warn off predators so when a wave begins to break and the jostling mimics a predator, the glowing begins. When the wave subsides the glowing stops. You can see the red tide of dinoflagellates in front of the blue wave below.

Watch it in action in this video from 2011.

Red tides happen fairly frequently in San Diego, though not every year, and they tend to be benign. (They are generally NOT benign in Florida!) Learn more about the 2011 bioluminescence in this video:

(photos from Wikimedia Commons and by Kevin Baird via Flickr Creative Commons license)

29 December 2022

Tundra swans pass over Pittsburgh in mid November but rarely stop on their way to the Chesapeake and Tidewater North Carolina. I missed seeing them overhead in Pennsylvania so while in Virginia this week I went to visit them at their winter home.

Tundra swans (Cygnus columbianus) breed in the arctic wetlands of Russia, Alaska and Canada and spend the winter in temperate marshes and grasslands, often near the coast.

Banding and radio-tag studies in the 1980s revealed that North America’s tundra swan population is split east and west with separate breeding and wintering grounds. In 2015 US Fish and Wildlife estimated approximately 117,100 in the eastern population and 56,300 in the west.

The largest winter concentration of tundra swans is in northeastern North Carolina, deep purple on this eBird map (Dec-Jan occurrences in the past 10 years).

Virginia’s Back Bay National Wildlife Refuge is close to the North Carolina border and attracts a portion of that large population. On the day after Christmas I stopped by to see them.

The bay view from the boardwalk is vast (see below) and the swans were quite distant. Through my scope I counted only 65 at first.

But I could hear a lot more swans than I could see. Over the next few hours more than 200 moved out to open water. The loudest ones shouted at each other and leaned in to emphasize their point.

Listen to distant tundra swans at Back Bay NWR, humming, whistling and shouting. Don’t be fooled when they sound like sandhill cranes. These are tundra swans at their winter home.

(credits are in the photo and map captions; click on the captions to see the originals. Sound converted from .wav to .mp3 using online-audio-converter.com)

11 December 2022

Similar to smoke rings, bubbles rings are vortexes that spin internally while they move through the water.

The internal spinning keeps the core in shape and allows it to continue traveling long after other bubbles have dispersed.

Dolphins and whales purposely produce bubble rings from their blow holes and play with them. They examine and prod the rings, roll them like wheels, speed them up, or nudge them until a smaller ring splits off. They will even bite or swallow the ring or swim through it if it’s large enough.

Divers familiar with the wild animals probably knew about this long ago. The rest of us saw it for the first time at aquariums. Here are some videos.

Video from 2008:

Video from 2010 at Sea World:

p.s. Though scientists have written about dolphins and bubble rings for at least 50 years, BBC Earth published a video only 8 months ago in which a scuba diver placed a bubble machine underwater and filmed the dolphins’ reactions. The narrated script says the dolphins are afraid of the manufactured bubbles and have to learn to be brave. Apparently, the producer was not aware dolphins already know about bubble rings, so why would they be afraid? Sigh. It’s a good example of why you cannot believe everything you hear on TV. Stay curious!

(photos and animation from Wikimedia Commons; click on the captions to see the originals. videos embedded from YouTube)