Momtazi, F. & H. Saeedi (2024). Exploring latitudinal gradients and environmental drivers of amphipod biodiversity patterns regarding depth and habitat variations. Scientific Reports, 14, 30547. https://doi.org/10.1038/s41598-024-83314-6.
The Importance of Crustaceans
When at the beach, many people will notice the many crabs and small critters. But most of the small critters are actually cousins to crabs called amphipods. amphipods are like crabs, though they lack a carapace (or hard back shell) and are laterally compressed, which is to say they are flattened side-to-side like an angelfish. Most amphipods species are marine, and they are extremely widespread, often being the dominant species in healthy ecosystems in the ocean. So, understanding where they live is key to understanding marine biodiversity, as well as what key habitats must be protected when determining new marine protected areas.
Momtazi and Saeedi decided to study just how diverse and widespread amphipods are in the oceans. Due to the extreme variability in location of amphipods, and just how many there are (thousands!), only one previous team, Arfianti and Costello, has tackled this question in 2020 with less data.
So this was no small undertaking for Momtazi and Saeedi. The team studied how depth, habitat type, latitude and environmental factors affected amphipod diversity and distributions. Depth was divided into shallow or deep, using a 200 m depth divider. Momtazi and Saeedi used pelagic (free-swimming) and benthic (seafloor bound) as habitat types of amphipods. Latitude was broken into 5 degrees, and any and all environmental factors were considered, like temperature, depth, salinity, and chemicals in the water like carbon.
So Many Amphipods!
The team considered about 1.74 million data points of amphipod identification and locations. Their data was from library and museum archives, literature reviews, open access science sites, and their own personal data—which turned out to be of significant benefit when they examined the tropics and subtropical data.
Momtazi and Saeedi removed any fossil records, poorly located records, and repeats. That process left the team with 1.14 million data points and 6,424 species ranging from 0 m to 10,900 m depth. And finally, the Momtazi and Saeedi compared the species and locations to their depth categories (shallow or deep), habitat types (pelagic or benthic), and environmental factors.
Claw-fully Awesome Diversity
Momtazi and Saeedi determined that Liljeborgia is the most widespread genera of amphipod and Corophium volutator was the most frequent benthic species.
Shallow pelagic amphipods were mostly recorded in the Caribbean and northern Atlantic, while deep pelagic amphipods were mostly found in the Gulf of California. In contrast, shallow benthic amphipods were found predominantly in the northern Atlantic, but deep benthic species were mostly in the Artic and Norwegian Seas.
The richest, or most diverse, shallow benthic amphipod communities were found in the Norwegian Sea, North Sea, and both coasts of the USA, but deep benthic amphipod richness was greatest in only the Norwegian Sea and Barents Sea.
Momtazi and Saeedi also determined that in shallow communities, temperature, chlorophyll, productivity were key drivers of the amphipod communities, but that dissolved oxygen in deep waters was the most determining factor. And finally, based on their analyses of all the factors, species, and locations, the team determined about a dozen groups of amphipod communities, which they grouped by location (figure 2).
Crustaceans and their Habitats
Momtazi and Saeedi’s study updated diversity research of amphipods in the world’s oceans, and begin a new level of understanding of distribution and diversity. Not only this, but the scientists found that with increasing temperatures and decreasing dissolved oxygen, there are less diverse amphipod communities. This could be call for concern, as the oceans change.
But, they also found that other variables like salinity may have a control over some diversity patterns. In the deep-sea, other scientists also have found sediment and carbon controlled amphipod diversity. Though it’s important to consider that Momtazi and Saeedi did not find agreement in their own work.
In the future this study will help inform new marine protected areas, because of the importance and dominance of amphipods in healthy marine ecosystems. Momatzi and Saeedi also argue that their work has highlighted the need to consider the ecological context (location, habitat type, environmental variables, etc.) when studying marine organisms.
I am a PhD student in Biological Oceanography at the University of Rhode Island, Graduate School of Oceanography. I completed my M.Res in Ocean Science at the University of Southampton, and completed my B.S. in Biology at Florida State University. I study deep sea coral communities and hydrothermal vent communities, especially with a focus on how physical and geological variable drive organism distribution, diversity, and change over time. When I’m not focused on school, I work with reptiles, and spend a lot of time making art for my friends and family!
