Happy Monday, Speak Up For Blue Crew! On today’s episode, Andrew talks about how different environmental regimes can cause seagrasses to switch between two or three different reproductive strategies. Unless you study seagrass meadows for a living, you might not have known that they are both an incredibly important and rare habitat for many juvenile fish, shrimp, crabs, and sea turtles. These animals prefer the shelter and foraging ground provided by lush seagrass meadows to the dangerous and mostly-desolate open ocean. Seagrass roots also help to hold together sediment along the seafloor, thereby preventing erosion and subsequent land loss in many coastal areas. Finally, seagrass meadows store a lot of carbon, which would otherwise end up in the oceans and increase ocean acidification.
Under neutral or favorable conditions, many seagrass species reproduce asexually or vegetatively. Individual plantlets bud up from underground root-like structures called rhizomes of the parent plant. This allows an individual seagrass to produce genetically-identical offspring in close proximity. And when there is no reason to move or spread to a new area, this works great for the community. However, when genetic diversity in a given habitat is low, some seagrass species will spend extra energy to produce seeds. This provides an opportunity for an individual seagrass to reproduce sexually and increase the genetic diversity of its offspring. As we’ve mentioned before, genetic diversity is what allows a given species or group of organisms to adapt to changing environments. A seagrass meadow composed of genetically-identical clones is much more susceptible to mortality events caused by diseases, storms, or pollution than is a community made up of genetically-distinct plants.
Recent research also shows that seagrasses have yet a third reproductive strategy, called pseudovivipary. This occurs when a seagrass flower contains an individual, genetically-identical plantlet instead of seeds. Though this strategy appears to be energetically the most expensive of the three, it lets an individual grass disperse its exact genome to a potentially healthier environment when its current habitat becomes unsuitable.
It’s important for scientists to understand the tradeoffs between these different reproductive strategies because, as coastal development and climate change increase, we’re seeing seagrass communities diminish at an alarming rate. These grasses are extremely sensitive to high salinity levels and turbidity, or the amount of sediment and pollutants in the water. As sea levels rise, we can expect to see rising salinity levels in areas that may previously have had vast stretches seagrass. And with all the runoff and increased activity that comes with coastal development, the turbidity and pollution of previously pristine seagrass medows may rise as well. If these nursery habitats go, so do the animals that so heavily rely on them. If you like (or make a living off of) fishing, if you enjoy your beachfront property, or if you simply want to prevent climate change from getting worse, start speaking up for seagrasses and the weird ways they make babies.
Enjoy the Podcast!