Prymnesium on Hickling?

[Guest]

I'm afraid that once that seed was sown, the  mistaken belief that dredging is the only cause of Prymnesium outbreaks will never be shaken now.

 

Especially here on the Broads, with the inevitable Bogeyman.

[MauriceMynah]

I once asked in another place if dredging might not actually be counter to this bloom. needless to say I wasn't taken seriously and given that the question was asked in my normal style I'm not too surprised, but I do still wonder... sometimes!

[BroadScot]

I may well be wide of the mark here, but surely up in the Hickling Broad/Thurne area regular water testing takes place to try and avoid such loss of fish? 

 

 

Iain.

[Poppy]

Iain,

Frequent and regular testing was certainly part of the process when the  dredging was taking place in Heigham sound . No evidence of prymnesium parva bloom was found.

The fact seems to be that PP flourishes in brackish water. Prolonged periods of low rainfall will lead to increased salinity...... Q.E.D.!

[MauriceMynah]

Even though I'm not wanting to seem even more stupid than I am, I have a few questions.

 

If Hickling broad were to be dredged to a significant depth throughout, would the ingress of saline increase or would it remain constant therefore being more diluted?

 

Has the formation of the shallow "Duck Broad" exacerbated this problem as I understand it was built with dredgings?

 

If the broad remains shallow, do not fish themselves disturb the sediment?

Same question applies to boats, wind, birds or any other activity I can think of!

 

General and thorough dredging does seem to be the answer for everyone, even the fishermen!

[BroadScot]

Well I am going to add a suggestion, will put my hard hat on first  What IF a lot more cruisers were up in the Hickling area moving the water about like they USED to do, would that make any difference, and IF it it did, then remedial work would be required to that bridge maybe? So more cruisers got to the area. My thoughts are all guess work, and more than likely well wide of the mark.

 

 

Iain.

[JennyMorgan]

My understanding of the problem, in part, and it applies to other Broads, is that a decreasing depth, e.g. by not dredging, results in a reduced flow or flush. This, so I'm told, leads to eventual health problems, as has happened at Hickling and, to a lesser degree, Oulton Broad. Not only does this affect the Broad in question but also the rivers and streams that feed them.

[smellyloo]

It seems to me that conservationlists want to freeze habitat in time to preserve/protect the current wildlife.

 

Whilst this may be possible in natural salt marsh and estuaries man made habitat such as the broads need constant management to preserve the status quo otherwise they will eventually silt up and return to scrub land

 

...... which I suppose would benefit the ****.

 

The forum software moderated my use of the word **** (a small blue bird or indees a coal ****)

[Guest]

Well I am going to add a suggestion, will put my hard hat on first  What IF a lot more cruisers were up in the Hickling area moving the water about like they USED to do, would that make any difference, and IF it it did, then remedial work would be required to that bridge maybe? So more cruisers got to the area. My thoughts are all guess work, and more than likely well wide of the mark.

 

There's that other well propogated myth again "remedial work on the bridge".

 

The bridge has stood there for over 600 years, and yet the average clearance has reduced by about 3" only in the last 40 years or so.

 

The bridge is not sinking in relation to the surrounding land, a misaprehension that has been debated so often.

 

East Anglia is tilting downwards, and sea levels are rising, and no "remedial work" can cure that.

 

Because its only 3 inches, it's only noticeable at the "hole" under Potter, where such a tiny measurement is so obvious.

 

The other factor that has reduced the number of craft getting through is the hire companies now building wider and taller craft, effectively giving up on the design constraints of Potter bridge.

[MauriceMynah]

Whether its the water level rising or the bridge sinking, that overall problem remains the same and should be the subject matter of a different thread. It's only relevance to the algae is if it has reduced the flow of water through it. If so, is that part of the problem and again if so,  how best to regain that flow.

Would a full dredge from Breydon to the Pleasure boat do what's necessary to improve the flush and thus to preserve the nature, the fish and the navigation for all ?

If the answer to this is "yes" then tolls alone will not cover it. We would need some serious lottery heritage money as well as a drop of government dosh.

[Guest]

.....Would a full dredge from Breydon to the Pleasure boat do what's necessary to improve the flush and thus to preserve the nature, the fish and the navigation for all ?.....

 

All of the recent discussions by many people about this on the Internet would seem to agree that increasing the depth of Hickling and surrounding waterways would probably ease the Prymnesium problem, due to a reduction in sediment stirring, by boats or weather.

 

However, I'm not sure about there being any way to "improve the flush" to any great extent by extra dredging of the lower Bure down to Yarmouth.

 

Hickling is 22 miles upriver from the Sea at Yarmouth, and the Thurne carries far less natural rainwater drainage than the Bure, Waveney, and Yare.

 

Improving the flow of the ebb would be matched almost exactly by an improved flood tide, so the tidal rise and fall at Hickling would increase, but the salinity might increase too.

[BroadScot]

Strowy the bridge bit was tongue in cheek. I was thinking more in chemistry...NOT my strongest school subject! A propeller creates bubbles... bubbles produce Oxygen? So more airiation in the water? More cruisers more airiation? Told you I was rubbish at Chemistry!

 

 

Iain

[Guest]

I'm even more rubbish at chemistry Iain, I never took it at school, but did physics instead.

 

...and so, with great trepidation (in case someone jumps on me with chapter and verse on the subject ), I'll add my musings to your oxygen hypothesis.

 

IMVHO, a propellor only creates oxygen bubbles if it's either cavitating, or not immersed enough.  When running correctly at displacement speeds, it should be slicing nicely through the water without any bubbles being produced.

 

So more cruisers without sufficient depth would probably disturb the bottom silt more, without adding any extra aeration.

[BroadScot]

As Strowy says ....

 

 

..and so, with great trepidation (in case someone jumps on me with chapter and verse on the subject   ), I'll add my musings to your oxygen hypothesis.

Can't think of anyone who would do that  

 

 

 Iain.

[marshman]

Martham Broad is very shallow in parts and hitherto PP has not been an especial problem up at West Somerton?  Discuss.

 

Catfield Dyke was affected 2 years ago and not this time  -  discuss.

 

The reed bed at Duck Broad and which once separated Heigham Sound from Duck Broad has been re-established - no mud was pumped into Duck Broad but into the lagoon created by baskets placed to recreate the old reed bed.

[MauriceMynah]

Interesting and fair points Marshman though may I ask you what you mean by "especial problem" regarding Martham broad?

 

My experience of trout fishing reservoirs is such that I notice debris including the occasional dead fish, collects in certain areas. Most of the dead fish I saw in this outbreak were in the boat dyke close to Whispering Reeds yard. Is that where the algae bloomed or just where the dead and dying fish drifted too?

 

Could the above be relevant when discussing the lack of same in Catfield dyke on this occasion?

 

As I understand it, Martham broad is not only very shallow but also pretty weed bound too. Could those water plants not only hold the sediment in place but also calm 'wind disturbed' water.

 

Your post suggests that you either know the answers to the points you raise or at least you have some deep seated theories. I would be most interested to read them.

[Poppy]

Interesting and fair points Marshman though may I ask you what you mean by "especial problem" regarding Martham broad?

 

My experience of trout fishing reservoirs is such that I notice debris including the occasional dead fish, collects in certain areas. Most of the dead fish I saw in this outbreak were in the boat dyke close to Whispering Reeds yard. Is that where the algae bloomed or just where the dead and dying fish drifted too?

 

Could the above be relevant when discussing the lack of same in Catfield dyke on this occasion?

 

As I understand it, Martham broad is not only very shallow but also pretty weed bound too. Could those water plants not only hold the sediment in place but also calm 'wind disturbed' water.

 

Your post suggests that you either know the answers to the points you raise or at least you have some deep seated theories. I would be most interested to read them.

 

This will be due to wind direction - nothing more. as a I understand this :naughty:

[marshman]

Hi MM - wrong choice of words for Somerton - I believe many years ago there was a problem above Martham Ferry but I do not recall a specific problem at W Somerton. But I am only youngish!!!!! And no, I do not have any specific answers but can see inconsistencies between the outbreaks.

 

What I was really trying to point out was despite all the profound theories and learned papers prepared and published, and individuals own views, there is just not one constant in any of these outbreaks and I do not think any one action will sort the problem - it really is inappropriate to blame anyone or any body for their actions when no one really knows the direct causes.

 

In these particular areas there are a number of factors which make the situation more difficult to pin down and this is made worse often by the spring weather we frequently have up here in Norfolk - brackish water springs in Hickling do not help, neither does lack of oxygenating plants.This time of year any run off pumped out from the deep dykes in the area are probably phosphate rich but each and every time it happens one or more of these "events" combine together to exacerbate the issue. However none of the outbreaks ever seem to have the same combination of events which "cause" it!!

 

But what does seem to be clear is that in neither of the outbreaks this year nor the one 2 years ago, could dredging operations have been part of the equation and yet time and time again this issue of dredging is raised as the culprit - is it the need to "blame" somebody???? This time of the year it is algae growth which is beginning to cloud the water not mud in suspension - you have only to look into the water everywhere to see this happening.

 

What is probably needed to help everyone is a bloomin' great 'ol storm to flush it out the Broads and rivers.

[MauriceMynah]

Thanks for the clarification Marshman, and I think I agree with you in that there is almost certainly a collection of causes and possibly an "Any three from eight" situation.

 

It does seem that "sediment disturbance" is a major player though, but having said that, there are so many different things that can make such disturbances it is hardly worth even 'going there'.

[JennyMorgan]

http://www.edp24.co.uk/news/600_000_fish_rescued_in_norfolk_broads_1_4036410

 

The Angling Trust has some serious funding behind it, not up to the RSPB, but nevertheless enough to kick some reluctant rrrrrrrrrs. It's long overdue, we need to see the stakeholders working together and doing so with some urgency. Now the fish are off the Broad then maybe the dredgers should be moving in?

[JennyMorgan]

Yet more similar news:

http://www.theguardian.com/environment/2015/apr/15/smell-of-dead-fish-could-put-visitors-off-norfolk-broads-anglers-say

[JennyMorgan]

Yet more info, including a/v report:

 

http://www.itv.com/news/anglia/2015-04-15/toxic-algae-killing-thousands-of-fish-on-the-norfolk-broads/

 

No knee jerk reference to dredging.

[bigbream]

Moving fish from hickling and Somerton to potter heigham is not what I call a great distance apart why couldn't these fish of been put in somewhere like horning or wroxham well out of the way and into deeper flowing water absolute joke

[JennyMorgan]

Moving fish from hickling and Somerton to potter heigham is not what I call a great distance apart why couldn't these fish of been put in somewhere like horning or wroxham well out of the way and into deeper flowing water absolute joke

Knowing the fisheries people involved I'm quite certain that the actions taken are far from being a joke. 

[bigbream]

Are these the same fisheries people who put a ban on river fishing for 3 months yet allow fishing on canals and lakes to go ahead explain that one in great differences