As a U.S. military naval blockade remains active in the Strait of Hormuz, traffic in the port has been massively reduced over the summer.
But one lesser-known impact of the blockade is what’s going on underneath the ships that are stalled, specifically a process called biofouling.
To learn more, Meteorologist Dave Epstein spoke with two experts for GBH’s Morning Edition.
Mario Tamburri is a professor at the University of Maryland Center for Environmental Science, and Carolyn Tepolt is an Associate Scientist at Woods Hole Oceanographic Institution. They recently co-authored a paper about how the closure of the Strait of Hormuz may trigger a bioinvasion super-spreader event. What follows is a lightly edited transcript.
Dave Epstein: Can you talk about — for an audience that may not have heard the term biofouling — what is that?
Carolyn Tepolt: Biofouling is basically the animals and plants that grow on hard structures that you put into the ocean. Things like floating docks, the hulls of ships, aquaculture, as well. And it’s actually a really rich biological community of all kinds of species.
It maybe just looks like the goo that grows on the bottom of your dock — but we’re talking about things like barnacles, things like sea squirts of many varieties, algae and a lot of other smaller animals that don’t directly attach to docks but live in the structure provided by the animals and plants that do.
Epstein: So, what’s unique about [this]? Obviously the Strait of Hormuz has been closed for many, many months. So, why is there more concern with the ships just sitting there than they would if the ships are sort of just moving through the strait?
Mario Tamburri: Well, this is actually a really unique situation. Ships will carry fouling organisms with them as they move around the world in normal operations. But all ships have antifouling coatings on them. These are paints that are designed to keep that growth at a minimum. And they work fairly well when the ship’s under normal operations, when it’s actively moving from port to port, maybe staying a day or two in port doing cargo operations. But when ships sit idle or sit still for long periods of time, the coatings actually end up failing and they get overwhelmed by the biofouling growth.
So, when the Strait of Hormuz was closed, we had well over 1,500 ships trapped within the Persian Arabian Gulf and another few hundred that were outside of the strait in the Gulf of Oman, idle as well. And as they sat there for now months, there was a real opportunity for this biofouling to accumulate. So, the reason why it’s so concerning is it’s almost a perfect storm. These are hundreds of ships sitting for extended periods of times. They’re typically very large ships like oil tankers, so bigger surface areas for things to grow on.
They were sort of stranded, if you will, during the worst time of year for biofouling, right when spring was coming on — in March and April, waters were warming up. And just like on land, as spring comes on, these marine organisms go through an increase in growth and reproduction. The organisms found in that region also are particularly tolerant to things like high temperatures and high salinities. So, we have really robust organisms felling those ships. And then we also have limited opportunity to do anything about it, given the situation and an active conflict.
There are in-water cleaning opportunities where you can sort of scrape the material off the site before the ships leave, but they’re not really set up to handle all those ships all at once in a safe and effective way. And finally, I think that one of the biggest points is that these ships have a global reach. Once they leave that region of the Persian Gulf, Arabian Gulf, they can go to ports around the world. Now, Asia and Europe are the closest and have the highest risk, but these ships can eventually reach the Americas, Australia and beyond. So, it’s really a sort of a worst-case scenario to cause a super spreader event, if you will, for invasive species.
Epstein: Carolyn, Mario alluded to something there that I think is important in your research, and that is: these organisms that are sitting there are in a very inhospitable, very warm environment. And your research is concerned about [that] sort of even at the genetic level. Can you talk about that a little bit?
Tepolt: Yeah, absolutely. So as Mario said, the current environment is very hot, it’s very stressful, but things are still growing there. And so, those animals are essentially under selection — adapting to that really harsh, particularly warm environment.
We know from studies of widespread fouling species that they can adapt to their local environment. So, if you find the same species in a colder area, it’s probably going to be more tolerant of cold than the same species from a warmer area. So, one of the concerns with this spread is not just the spread of new species — although that is a primary concern — but also the spread of genetic diversity that might be adapted to some of those warmer, more stressful conditions, and they again then get brought to their populations and essentially give them a little bit of adaptive flexibility against future changes, particularly warming.
Epstein: Is there any organism that you’re particularly concerned about, or is this more just a general idea? Or is there something that you’re aware of that might start spreading around the world?
Tamburri: It’s hard to predict who the next invader might be. There’s so many variables involved with the successful translocation of an organism and its establishment in that new location. But it can range from microbes — that can include things like pathogens that can impact human health or wildlife or aquaculture health — all the way to those larger organisms that Carolyn already mentioned.
An example is the Asian green mussel that’s native to the region. It is now an invasive species in Florida, in the Caribbean, in South America, Australia. It’s displaced native organisms. It’s clogging the cooling system of power plants. So, it’s having dramatic impacts.. It’s hard to pick which suite of organisms might be the next invader from this event, but it’s likely there’s going to be some.
