Oceans Before Humans: What Can Sponges Tell Us?

Buenas de Panama!

As I mentioned in my last blog post “#LoaGlobal: LoaTree Goes to Panama,” I am currently living in Panama and interning for the Smithsonian Tropical Research Institute’s (STRI) Paleobiology lab. There are a number of interns here working on independent projects that focus on varying organisms from colorful Parrotfish to branching corals, and while each of these projects are intricate and rich on their own, my lab is stringing them together to construct a realistic baseline of what a “pristine” ocean reef looks like. The purpose in constructing this narrative is to develop conservation measures that are better informed, and we expect that the knowledge gained from this historical ecology project will give us a more complete picture of the impacts that anthropogenic (human) stressors have had on coral reefs from the Pleistocene (about 11,700 years ago) to the present.

 Leading the Research

STRI Symposium PhotoCue Mike Hynes! Or as we like to refer to him as in our lab, “The Sponge Prince.” Mike is a graduate of the University of Calgary where he majored in Geology and Paleontology. He’s been working in Panama for seven months now on a collaborative sponge project with Magdalena Lukowiak (STRI Fellow and Post Doc at the Polish Academy of Sciences) and Aaron O’Dea (STRI) to reconstruct the history of sponge communities in Caribbean reefs. For those of you aren’t sponge experts, I’ll break down why sponge research is essential to the constructing the baseline.

The Sponge and the Spicules

Porifera_body_structures_01-1024x544Not to be confused with corals, sponges are actually animals with a worldwide distribution stretching from polar regions to the tropics, and live in both marine and freshwater environments. Why are these simple organisms a fundamental part of marine ecosystems? Because they filter water and add stability to reefs. Acting like a chimney, sponges take in and expel water, trapping 90% of the bacteria they filter. They can pump 10,000 times their own volume in one day, and a sponge the size of a gallon milk container could pump and clean enough water to fill a residential swimming pool in 24 hours. The sponges phylum name Porifera literally means, “pore bearer” which makes perfect sense, considering sponges are composed of pores and channels that facilitate the circulation and filtration of water.

Sponges have relatively simple body plans, which have been tailored to be efficient at filtering water through the central cavity of their bodies. The “skeleton” of the sponge is composed of tiny needle-like splinters called spicules (which can either be formed of silica dioxide or calcium carbonate), a mesh of protein called spongin, or a combination of both. Because of their dependence on a water-flow system, they tend to occupy habitats characterized by quiet, clear waters as wave action stirs up sediment, clogging their pores and preventing them from feeding and breathing.

What Does Is All Mean?

Sponges of Interest: Placospongia intermedia and Geodia papyracea

 

The silica spicules of sponges preserve exceptionally well in reef sediments after sponges die. For Mike’s project, sediment samples were extracted from three reefs in Bocas del Toro, Panama to explore changes in sponge communities over the last 1-3 thousand years. Of the twelve spicule types found in the samples, two specific types seemed to be dominant (for the purpose of this post, and because the terms even confuse me, I will be referring to these two types as type 1 and type 2). Mike and crew observed that as they moved up the sediment core towards the present day, the relative abundance of type 1 spicules increased; a pattern that occurs in each of the three geographically separate reefs, suggesting a region-wide driver.

Spicules1Type 1 spicules are only produced by two types of encrusting sponges, and have previously been known to increase in abundance as coral reefs degrade, filling the niche the coral has left behind. Additionally, sponges represent the principal diet of Hawksbill turtles, so an increase in type 1 spicules could be the result of the drastic decline of Hawksbills, well-documented spongiovores. Once plentiful off Panama’s Caribbean coast, Hawksbills have undergone an almost complete eradication as the result of heavy and ever-increasing fishing pressures. This dramatic decline may have facilitated a shift in the sponge community, allowing them to escape predation and increase in numbers. By applying the Spicular Analysis Approach to loose sponge spicules preserved in sediment from reef cores recovered from the Caribbean, Mike’s aim is to reconstruct the history of sponge communities in Caribbean reefs.

Tune in next time to hear about what my lab mate Erin Dillon is doing with shark dermal denticles!

If you have any questions or comments about Mike’s sponge project, or just want to know a little more about what goes on here at the Smithsonian Tropical Research Institute in Panama, please feel free to send me an e-mail at: cthrncourtier@gmail.com

 

 

Images courtesy of: 3) Sponge Diagram 4-5) Sponge Images 6) Spicules

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