Thoughts on water colour???

[cuzzamundi]

G'day,

Anyone got any thoughts on why the water dirties up/goes greener from the northerlies in SEQ? Even well offshore, it seems to turn a greener colour. Why do you reckon it does, compared to south easters? If it was sediment, you'd think the southerlies would be just as bad, as it's still movement from wave action. Any thoughts?

Cuzza

[EdBerg]

Just guessing on my part, but it could be due to the nutrient level and and more specifically the algae from the tropics which is more prevalent the closer you get to the coastline up there and clears up the further you go out to sea, it could be pushed south by the Northerlies. The nutients are from the runoff from all the mangrove swamps, tidal areas and river systems which increase the algae growth.

Ed.

[Slider]

Expect it would be 'anaulus australis' Cuzza - which is what we've been seeing cycles of here at Noosa. Northerlies increase water temp and sun for photosynthesis and the algae proliferates. South easter drops the water temp and sun and the algae dies off and washes on to the beaches.

We're expecting the surf here to go from green to brown today or tomorrow as the bloom intensifies.

[cuzzamundi]

Never thought of that, Lindsay. Was hoping you might chime in. Does the annus australis occur year round - does it dirty the water via northerlies all year? Seems that the bas%ard northerlies dirty the water no matter what time of year, and a long way out, too.

Cuzza

[Slider]

Is predominantly spring through to autumn but the tell tale signs of brownish foam on the edge of the waterline on the beach during winter in some recent years indicates the presence of anaulus australis, though the water looks clean.

We usually start to see signs of algae during Oct/Nov when the northerlies kick in and the temp rises, but have had bad blooms in late August/Sep after sufficient rainfall to cause a stream rise. Any flood in the warmer months seems to always trigger a bloom as the sediment drops out of the water column.

Have had situations in the last few years when the algae (aa) seems to stretch from Yeppoon to Ballina, but could be far further in both directions. I've seen Moreton Bay completely discoloured by aa at the same time as Hervey Bay, Fraser and all Sunny and Gold Coast surfs which makes it hard to find clean water at times apart from up the streams. The Noosa Rvr has certainly been cleaner than the surf at times lately.

Didn't see blooms prior to 2001 apart from the very occasional one during the 80s drought. The last el nino phase delivered serious blooms with northerlies predominating and other algaes like hincksia, trichodesmium and lingbya also causing problems in SEQ. Increased nutrient load from suburban and agricultural runoff, dryer hotter climate with more extreme weather events and probably reduced predator numbers would be the causes for an escalation in algal blooms. There are many potential negatives associated with increasing incidences of blooms and a few potential positives. Invariably though, blooms will alter the structure of inshore ecosystems with some species benefitting, but most, and likely the ones we currently harvest, depleting. Invasive species are most likely to be the main beneficiaries of algal blooms.

Interesting this morning that the surf at Teewah is fairly clean, though a little green, when we expected it to bloom in these temps. But then I hear last night that the water temp on the Sunny Coast has gone from 23 to 21 degrees in the last couple of days.