#sciencey stuff

Biocrusts form when filimentous cyanobacteria and/or fungi knit the surface of the soil together, forming a stable aggregate. You can tell a biocrust from normal soil because it retains its shape when you pick it up and it has little dangly bits of soil (the cyanobacteria holding the soil):

There are different types of biocrusts, distinguished by the dominant organism. From right to left there are light cyanobacterial, dark cyanobacterial (the cyanobacteria are have dark sunscreen pigment), lichen, and moss/bryophite crusts.

Biocrusts form in places where plant cover is low, thus they are often found in deserts (in the pic below basically all of the rough ground cover is biocrust on gypsum soil, which they love). But they can be found in any climate (there's actually a small area in ohio where they are common).

Biocrusts are NOT formed directly on the surface of rocks (left pic), they are SOIL aggregates. They also DON'T include areas where algae have colonized the soil but where the surface cannot be removed as seperate from the rest of the soil column (this would probably be more of a biofilm (right pic)):

For Shark Week this year I wanna do something fun so for every day of Shark Week I’m gonna share one of my favorite species of sharks and some ✨zesty shark facts✨ about them!! Sharks are cool so here we go

Shark Week Day 1: epaulette shark

The epaulette shark (Hemiscyllium ocellatum) is a species of carpet shark found near Australia! They’re called epaulette sharks because of the large false eyespots found on their back, the purpose of which is to confuse and deter predators

In my opinion, however, the coolest thing about the epaulette shark is that they are actually able to walk around! They’ve evolved such that their pectoral and pelvic fins can almost function as legs and enable them to “walk” around the seafloor! Not only that but they’re also able to survive up to 2 hours of total anoxia and remain out of water, by increasing blood supply to its brain. Yay epaulette sharks!

Some highlights from my trip to Tring Natural History Museum included:

An elephant bird leg cast and complete model skeleton

A cassowary skeleton

A thylacine (and skeleton)

An albino eastern grey kangaroo

A ground sloth skeleton

A quagga (along with a copy of the only living specimen ever photographed)

Well, setting aside how unbelievably cool they are, they have very important ecosystem functions. Biocrusts exist where there is a lack of plant cover. Plant roots help to hold soil in place and biocrusts provide that same function because cyanobacteria hold the soil particles together. When biocrusts are disturbed, the underlying soil is eroded away.

Biocrusts are also important for nutrient cycling, particularly in the deserts where nutrients are limited. Cyanobacteria, lichens, and mosses all photosynthesize so they are fixing carbon into the soil. Some cyanobacteria also fix atmospheric nitrogen, which is a super energetically costly thing to do and is very important given that nitrogen deficiency very commonly limits plant/organism growth. These nutrients are also likely being absorbed by the surrounding plant life, thus befitting the whole system.

On top of that, biocrusts host a great diversity of microorganisms. These organisms live life on the edge of habitatability. There is so much we can learn from studying how they survive and thrive under such desolate conditions. And we can use that knowledge to build a better picture of how life functions as well as steal from mother nature to improve our biotech.