Australasian barnacle )Austrominius modestus) Public Domain)

Dear Readers, my Linnean Society newsletter this week featured an interesting example of the law of unintended consequences. There are currently some 1500 vessels stuck in the Strait of Hormuz, waiting for the current war with Iran to end. All of them will have been fitted with what are known as biofouling measures – these are special paint or structures that reduce the amount of algae, bacteria or other marine organisms that grow on the undersides of the ship. Coupled with the fact that ships are normally only in dock for a couple of days, this means that most biofouling is minimal. Which is just as well, as when the ships move on you don’t want them to spread their organisms to other ports. The barnacles in the photo above came originally from New Zealand, and spread to Western Europe while ships from the Antipodes were laid up waiting for escorts across the Atlantic.

The ships in the Strait of Hormuz have been stuck there for, in some cases, months. Biofouling measures start to break down when the ship doesn’t move, and organisms accumulate. Furthermore, there’s a problem in the Strait itself – rising temperatures have had a knock-on effect on salinity, which has decreased biodiversity and increased the number of a small number of extremely tough organisms who can survive a wide range of conditions. And then there’s the question of reproduction: the delightfully-named Cosmopolitan Barnacle (Amphibalanus improvisus) can produce up to 36 offspring per day when the temperature is above 30 degrees Celsius. The ships then form a perfect substrate for the baby barnacles to attach and continue to grow.

Cosmopolitan Barnacles (Photo By Andrew Butko, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10732884)

It’s in the interests of the shipping companies to make sure that their ships aren’t covered in barnacles or algae – these organisms increase drag, making ships slower and less fuel-efficient. However, the scientists in the paper quoted (Tamburi et al, 2026) suspect (and I’m sure they’re right) that when the Strait opens, the last thing on the mind of the captains will be sorting out biosecurity – they will want to get their crews and their cargo to where they’re supposed to be. Sadly, they will not only be transporting barnacles and algae, but also the pathogens and parasites that use them. The final result could be the spreading of organisms all over the world, particularly to ports with similar conditions to those in the Strait, with Jeddah, Mumbai, Colombo, Singapore, Alexandria, Piraeus, Algeciras and even Rotterdam being vulnerable to these organisms setting up home. Not only will these cause problems for ships, but they will also damage the ecosystems to which they’re introduced, being so well adapted to warming waters that they could well out compete existing plants and animals.

The report suggests that there’s little that can be done in the Strait itself, but that destination ports could be put on high alert and have remedial measures ready when an infected ship arrives. Furthermore, even if the ships can’t worry about treating biofouling while stationery, estimating the amount and type of organisms involved could help destination ports to prepare.

While the economic and human costs of the US/Iran war are foremost in everybody’s mind, I hadn’t thought of this particular aspect of the (many) ecological impacts that it will have. With shipping routes increasingly becoming targets for military action, and with ships and crews being ‘stuck’ more and more often, it would seem sensible to have plans and measures in place. Let’s see if it happens. Otherwise, as the report describes, we could be about to witness a ‘global bioinvasion super-spreader event;.

The report can be read here (and very interesting it is too!)