Algae - North Adriatic

I am creating this thread to host anyone interested in discussing the algae situation in the North Adriatic.

From what I read it sounds more than troublesome.

Is this algae suspended in the water column or does it largely float on the surface?

Can you post some pictures?

I haven't seen any yet, but am heading in the direction where it apparently exists. I have found some chatter on the internet about it, but surprisingly little, actually. One video (17 June 2024) claimed columnar, but it wasn't clear to me in the video. Lots of small surface algae doesn't worry me. But columnar "slime-algae" does. If it means having to clean strainers 2x per day, I could live with that for awhile. But can a troublesome amount get beyond the strainer baskets??

I've been through an awful lot of algae and slime in the French waterways and it never resulted in a problem... But then the risks in a canal system are fewer than they would be in the Adriatic sea.

Already when we went up to Venice on 19 July we did see quite a bit of algae in the area between Venice and Istra. Also lots of freshly cut grass in the water, which came all out of the lagoon as we found out later. Someone has been cutting grass and dumped it all in the lagoon.
The algae apparently come from the river Po and initially we thought that someone had emptied his black water tank in front of the anchorage (Vabriga). But then the situation turned and the last week the amount of algae has increased drastically
We were in Vabriga for some work on our engines, but had to cut it short and make a run to Pula (we are now in the port of Pula on anchor). Along the way we basically were sailing through algae. Closer to the coast they were thick layers and stretching for a couple of miles long, few hundred meters wide.
Problem with the algae is that they multiply rapidly and then slowly start to sink. The algae at the surface are not the problem for our engines, but the ones below the surface are. They can get sucked into the filters, potentially blocking them.
Also, the use of a water maker, generator, air conditioning etc is not possible, but worst of all is the smell once they start to die and rot. It is truly disgusting.

I have asked the question on facebook fora and basically Trieste until Pula is fully covered in algae. There are pictures where beaches have become unserviceable due to thick algae fields.
We thought that going 5 nm off shore would help us find clean water, but although the thick fields were not there, we could see algae everywhere.
Around the corner, so Pula direction Rijeka, is still clean. I have no information about the Kornati or the islands south of Istra.

Since it takes between 6 and 10 weeks before the algae are all dead and have been eaten or sunk to the bottom, the tourist season for Istra is over. Swimming is not really possible and the smell is horrendous. Local fishermen now have a big problem and especially the oyster and mussel farms are hard hit. They cannot harvest the shell fish anymore.
Once the algae die they will start to ferment and turn into food for plankton eaters, so for nature itself it is not a bad thing that we have the algae.

Now in Rab. Fortunately haven't seen a hint of algae or grass yet!

I sent out a few "chat" requests for information via a local marina booking app, Navily. The app lets you see where various members are currently located and you can initiate a chat session with them, if desired. Here's some of the feedback I received today:

• Rovinj: a little mucilage outside harbor and, I think, more in the harbor
• Portoroz: No algae
• Umag to Veruda - situation reportedly "bad"
• Pula: No algae
• Aquileia: No algae
• Grado lagoon: No algae
• Grado - outside: long pieces of sea grass that do get into the strainers.
• Trieste: No idea...but I've asked a couple of people and am awaiting responses.
• Muggia (just a bit south of Trieste): Water fairly clean.
• Numana to Venice (Italian east coast): Bad. Large brown masses of algae.

Am in Rovinj now and fortunately, have seen only a tiny trace of mucilage - and that was in the harbor.

Cruised from Rovinj, Croatia to Piran, Slovenia today. Happy to report that we did not encounter any algae or grass whatsoever. Quite amazing, since the water temps were ca 31 degrees C in the harbors and 29 along the coastal route we took today.

Cruised from Piran, Slovenia to Trieste, Italy today. Didn’t see any algae whatsoever. A Navily booking app user reported that the Trieste harbor was clogged with algae in June. Fortunately, there’s no trace of it now.

Cruised from Trieste to Aquileia a couple of days ago. Saw only traces of grass. Fortunately no algae or mucilage. Aquileia has a fantastic museum dedicated to Roman antiquity. Worth a detour, if you are ever in northern Italy!

Left Aquileia and cruised through the Grado and Marano lagoons today to Lignano Sabbiadoro.
Saw sporadic, small clumps of grass and dead algae. Fortunately not enough to cause any problems.

Cruised from Caorle to Venice today. Sea was like glass! Saw only sporadic islets of grass and algae/slime. No inconvenience caused. Cruised some of the major channels around Venice and did not see any algae or grass. Our destination marina, Marina Sant' Elena in Venice has ~5% grass coverage. No algae.

The roughest seas we've encountered in the last three months were in the Venice lagoon with no wind...but lots of watercraft traffic!

This is my last post on this thread as in a few days we will magically find ourselves in the Ligurian sea, after truck transport to Genova.