MillersLocal
  • Home
  • Latest Shots
  • Blog
  • Comp news
  • Surf Report
  • SurfGuide
  • PHOTOS
  • Vintage
  • Enviro
  • Shop

Blog

Red tide. Blue glow. Black death

1/26/2014

 
Picture
All that glitters is not gold. Turns out that all that glows has a dark side too.

The plankton party that has had everyone in awe by turning the wildside shoreline into a spectacular light show has got a sting in the tail. There were reports of a large number of dead fished washed up on Sards beach yesterday.

Local scientists had warned that this could be one of the side-effects of the recent red tide. The party can go bad for two reasons, both oxygen-related. 

Firstly the plankton are on such a mad jol with their nocturnal glow antics that they suck all the available dissolved oxygen out of the water at night cos of some heavy breathing (cellular respiration in science-speak). Pretty much the same way you'd get breathless busting out all your moves on the dance floor.

Secondly, all epic jols have to end. The mass death of the critters once the party is over results in a whole big pile of bodies on the ocean floor. Along come hordes of bacteria - who are the grim reapers of the sea and pitch up wherever things are dying. These ocean street cleaners have to decompose all the dead stuff. But guess what, decomposing death is hard work!
Picture
© Marizanne Ferreira
Picture
© Marizanne Ferreira
All this effort means the bacteria suck up most of the oxygen in the surrounding water. Although not a great thing, it isn't a train smash as long as the bottom waters are mixing well with the oxygen-rich surface waters - which means the oxygen content down below gets renewed. The hiccup comes if due to localised sea conditions the water becomes stratified. This is basically like a Water Apartheid.  The water on the top don't mix with the water on the bottom. It often occurs in bays and coves, such as Sards, that are cut off from the large-scale circulation patterns that promote mixing. Probably find the lack of swell on that side has amplified the weak local currents even further.

Because the oxygen-depleted bottom waters don't get refreshed, it causes hypoxia. This makes it really hard for fish and other marine creatures to breathe. Pretty much a case of "Move or die, fish". Sometimes the oxygen depletion happens so quickly that it cuts off escape routes and then results in the death of marine life through suffocation. This is called a black tide, and seems to have been the case at Sardinia Bay - with upwards of 300 fish washed up onto the beach on Saturday afternoon.

It's pretty ironic considering the bacteria are there to clean up the dead to start with. You're maybe not doing your job so lekker if you cause death whilst you're cleaning death up. Just saying. 

Nature can be weird sometimes.

And there's still possibly another twist in the tale. Low oxygen conditions can allow certain bacteria to convert sulphates in the water to hydrogen sulphide gas. Remember the stuff that smelt like rotten eggs in science class? This stuffs so hectic it can even corrode metal objects and cause respiratory problems if you live close by.

So if the water is ponging like your fat uncle's fart, probably don't swim with your Rolex or stand there for hours gulping in lungfuls of the stinky air. Let's hope these sulphate-converting bacteria don't show up, cos besides the pong it could result in even greater fish deaths.

Scientists from Bayworld have collected samples of the dead fish from Sards and will be investigating further.
Picture
© Nick Cadle Photography
Marizanne Ferreira link
1/25/2014 07:53:44 pm

Very informative! Thank you x

Clifford clarke
1/26/2014 04:37:03 am

Any idea how much longer the red tide will be around?

millerslocal
1/26/2014 05:08:58 am

Hard to say - but it appears really widespread along the whole coastline. Think some big swells will help in terms of dissipating it. Looks like some surf on Wednesday which might do the trick. Some strong offshore winds could also help.

Brownie
1/26/2014 02:10:03 pm

Any idea if its safe to chow fish caught yesterday in the bay, i have a few from off shore fishing, they fought propper n didnt seem sick?!

Peter
1/26/2014 04:17:11 pm

Is it safe for people to go swimming and surfing at the moment? Secondly, is it an issue if one swallows some of the water?

millerslocal
1/26/2014 06:18:52 pm

My understanding is that the fish deaths at Sards are related to hypoxia not directly from ingestion/exposure to the plankton. To date studies have cautioned against eating filter feeders such as mussels & oysters cos they eat the plankton itself, the fish do not. To date there doesn't appear to be any study which can show a direct correlation between yessotoxin ingestion and an health impact in humans. However, certain countries such as Aus & New Zealand have set upper limits of yessotoxin concentrations in fish that are sold. Maybe just to hedge their bets in case someone does get sick eventually? Long story short - you're probably fine to eat them, but don;t blame me if you get gippo-guts, your heart fails or you glow blue in the dark!!

Marney
1/27/2014 06:05:18 pm

It might just be the coolest thing to glow blue in the water at dusk. Surfing boardies at sunset time would be the way to go and hopefully ingesting some of that smurf-juice. It has affected one or two okes who did swallow a duckdive - okes that swallow, yah right - and they have experienced tightness of the chest on the golf course - serves them right for playing without me!
My own laaitie was out in the red stuff yesterday and lasted about half an hour until he complained of burning eyes, serves him right for not listening but the pharmacist did skeef the 13year old laaitie when he bought eye-gene.
My advice, even though the waves are coming on Wednesday, dont swallow ( hehehe) and close your eyes when you're under. You cant see the reef anyway so touch will rule.. Oh yes... Wear a wetsuit it will protect your skin from absorbing stuff and if you do go out in boardies wear SUNSCREEN even if there's no sun.. It protects the skin from absorbing crap...


Comments are closed.
    Picture
    LATEST POSTS
    More posts HERE

    Author

    Millerslocal

    RSS Feed

    Archives

    August 2020
    July 2020
    May 2020
    April 2020
    March 2020
    February 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    July 2019
    June 2019
    May 2019
    April 2019
    March 2019
    February 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    April 2018
    March 2018
    February 2018
    January 2018
    December 2017
    November 2017
    October 2017
    September 2017
    August 2017
    July 2017
    June 2017
    May 2017
    April 2017
    March 2017
    February 2017
    January 2017
    December 2016
    November 2016
    October 2016
    September 2016
    August 2016
    July 2016
    June 2016
    May 2016
    April 2016
    March 2016
    February 2016
    January 2016
    December 2015
    November 2015
    October 2015
    September 2015
    August 2015
    July 2015
    June 2015
    May 2015
    April 2015
    March 2015
    February 2015
    January 2015
    December 2014
    November 2014
    October 2014
    September 2014
    August 2014
    July 2014
    June 2014
    May 2014
    April 2014
    March 2014
    February 2014
    January 2014
    December 2013
    November 2013
    October 2013
    September 2013
    August 2013
    July 2013
    June 2013
    May 2013
    April 2013
    March 2013
    February 2013
    January 2013
    December 2012
    November 2012
    October 2012
    September 2012
    August 2012
    July 2012
    June 2012
    May 2012
    April 2012
    March 2012
    February 2012
    January 2012
    December 2011
    November 2011
    October 2011
    September 2011
    August 2011
    July 2011
    June 2011
    May 2011
    April 2011
    March 2011
    February 2011
    January 2011
    December 2010
    November 2010

Picture
SURF GUIDE
Shit you should know
​Surf safe

Da rules
Gear Guide
​
SURF STUFF
The Boardroom
Greg Smith boards
​Surf Centre
DEETS
Contact us
​Terms & conditions
  • Home
  • Latest Shots
  • Blog
  • Comp news
  • Surf Report
  • SurfGuide
  • PHOTOS
  • Vintage
  • Enviro
  • Shop