On the thoughts of iNaturalist, marine biodiversity, and identifying sponges from photos.
I decided to make a sub-project within my greater 'Marine Biodiversity of Canada" umbrella project to refocus some of my spare time on one group of animals that I've thought a lot about over the past couple of decades (https://www.inaturalist.org/projects/marine-sponges-of-the-pacific-northwest)
20 years ago, I stepped into my first sponge biology lab. My first lesson was that these animals are characterized by their 'absence' of everything. Sponges lack heads, organs, tissues. Some lack 'true cells'. They're often described as 'shapeless, amorphous blobs'. One encounter I had with professional oceanographers sticks with me - "I thought they were some kind of rock!". It made studying them hard when general ignorance was the predominant mindset among ocean science community. On the flipside, it was also rewarding when you can somehow generate some rules to push the science forward with baby steps.
For those open to learning, the first steps to identifying a sponge as a non-specialist is to accept that you can't identify them like you would a plant or a bird through macroscopic whole-organism features.
(1) You need microscopy to identify a sponge down to the species level with high confidence; the entire phylum's taxonomy is characterized by tiny skeleton features known as 'spicules'.
These glass or calcium carbonate 'lego bricks' make up the internal skeleton upon which the amorphous blob of tissues is draped. When the sponge dies (I also have stories to tell about how some oceanographers don't know how to tell the difference between a live, dead, and upside down sponge!), the spicules remain, but often the 'diagnostic spicules' are small, loose, and drift away with the decaying tissue. The presence or absence of these diagnostic spicules is how some species are identified. So, the false-absence of some spicules as a result of 'spicule loss' can also confuse even the best sponge taxonomists.
Therefore, the gold standard for a species-level ID for sponges requires a large fragment of the whole-healthy sponge for proper microscopy. A thorough inspection, with an exhaustive effort to look for 'rare and hard-to-find diagnostic spicules', also makes high-level taxonomic work difficult. Without microscopic evidence and focused detective-type lab work, any species-level sponge ID would be an informed best guess by even professionally trained sponge biologists (i.e. take it with a grain of salt, and with a large degree of uncertainty).
(2) Sponges are known to be diverse in form, meaning a species of sponge can take the whole-body shape of a saucer, a boot, or a blob.
However,
(3) Sponges are known for their cryptic diversity, meaning several species of sponges can look identical.
Endless arguments from sponge taxonomists with sponge 'biologists' have centered on whether or not we can move away from high rigor and have 'looser' IDs (heated debates).
Together, this adds to the difficulty of bridging the heart of how iNaturalist crowd-sources 'species identifications' with easy-to-capture photographs of the organism to generate hypothetical data that could be useful for scientists like me who research/map biodiversity patterns.
At the moment, I won't use iNaturalist data for this group of animals because the crowd-sourcing process forces 'incorrect' species IDs but labels it as 'research-grade'. In other words, the iNat platform has systematically injected wrong IDs into the majority of the data because the majority crowd-sourced audience doesn't have formal official knowledge to correctly ID an entire phylum's worth of species.
This is by no means saying iNaturalist isn't useful (I have the complete opposite perspective), but rather an example of how 'marine' biodiversity observations on iNat are lagging behind terrestrial efforts (deja vu if you've followed the history of ecological research).
So, using sponges as an example, are there rules that can help intertidalists and scuba divers put a name to their wonderful photos of sponges on iNaturalist?
(i) The auto-suggestion algorithms for iNaturalist for sponges are more than likely incorrect. However, with systematic incorrect labelling, projects like this can hopefully back-trace a more appropriate species ID in the future.
(ii) When taking snapshots, take a picture of the whole sponge and provide as accurate a location as possible. At a minimum, one can assume the same morphotype from a 'geographically distinct' population will be the same species, so a voucher specimen sampled at a later date might improve ID confidence for a commonly visited site.
(iii) There are three 'common' classes of sponges: Demosponges, Glass Sponges, and Calcarea Sponges (stop right there with Homosclereomorphs - i said common and this post is about the Pacific Northwest).
Without expert training, it's more than likely any intertidal sponge will either be a demosponge or a calcareous sponge. Glass sponges are only found in deep waters at the edge of safe recreational scuba diving limits. Calcareous sponges and glass sponges also have much less morphological variety when compared to demosponges.
So, through a process of elimination, if it doesn't look like the standard calcareous sponge (small finger shaped or bird's nest intertwined forms) or glass sponge (cloud sponges bushes and globlets, boot sponge cylinders), it'll likely be a demosponge (every infinite permutation of amorphous blob you can think of). Therefore, most IDs can be done with high confidence to the class level by everyday explorers.
Hopefully, this helps improve the data being generated by community scientists for this group of animals. Sponges have survived every mass extinction our planet has experienced (and will survive the Anthropocene). They're one of the oldest animals found in the fossil record. They have occupied every aquatic habitat on our planet They are found in every ocean from pole to pole. Our collective science has historically misrepresented this group as a 'minority' of the marine biodiversity world, but in a reality, they are the dominant animal of our past, present, and future planet.
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