Anyone that has played with coral reef sand has felt the sharp needles of sponge spicules in their hands. Spicules are made by sponges (and other animals too, like some ascidians) and are like glass. In fact they are glass, being made of pure silica, and they are used by sponges as defense from chomping fish or to help keep the sponge rigid. They come in an amazing variety of shapes and sizes, and the sands of coral reefs can be filled with billions of spicules.
Sponges are very important for reefs. They filter huge quantities of water keeping things clear and clean, provide important homes for loads of other animals, and they protect reefs from erosion by binding the reef together. But, as with most of life in the Caribbean, sponge communities have started to deteriorate. Since the 1980’s they have become less abundant and less diverse. Without sponges reefs may just wash away.
We wish to explore the historical changes in Caribbean reef sponge communities. When did sponges decline and why? The coring project of the TMHE will be exploring sponge spicules through the last few thousand years in several Caribbean reefs (see here). However, spicules are strange beasts. Some sponges produce millions of spicules, others hardly any or none at all. Spicule shape is highly variable (see image) but is not tightly phylogenetically constrained. That means that some spicule types occur in unrelated groups. What’s more, some sponges have more than one type of spicule, sometimes three or four.
This all makes it extremely difficult to reconstruct the sponge community from a bunch of spicules. In this paper student Magdalena Lukowiak at the Polish Academy of Sciences who had held a short term fellowship at STRI explores the taphonomy of sponge spicules on a Caribbean reef in Bocas del Toro. The relationships between sponge community and spicules found on the sea floor explored in this paper will help us to resolve changes in sponge communities through our cores.
Upwelling along the Pacific coast of Central America today occurs where the land drops to less than 500m. Low land allows the trade winds to blow across and push surface waters out to open ocean causing strong coastal upwelling.
In this paper we estimate the strength of upwelling in the Plio-Pleistocene Continue reading →
What drives major ecological and evolutionary changes in the seas? To explore this question we documented changes in the abundance of different clams in the Caribbean over the past 11 Myr.
The structure of clam communities shifted dramatically with an increase in the abundance of attached epifaunal bivalves and a decrease in infaunal bivalves. This was driven by the proliferation of coral reefs, ultimately caused by the closure of the Isthmus of Panama.
These data provide a classic case of proximate and ultimate drivers of evolutionary change. Jill Leonard-Pingel was lead author. Pdf forthcoming….
In the coming century, life in the ocean will be confronted with a suite of environmental conditions that have no analog in human history. Will marine species adapt or go extinct?
The last two years I have been involved in a dynamic working group called “Determinants of extinction in ancient and modern seas” led by Paul Harnik, Rowan Lockwood and Seth Finnegan and funded by NESCent. The aim of the working group is to use the history of life as preserved in the fossil record to help make better predictions about where life is heading in the future, especially in view of the looming sixth mass extinction.
We have just published our first paper in Trends in Ecology and Evolution. The study compares the patterns, drivers, and biological correlates of marine extinctions in the fossil, historical, and modern records and evaluates how this information can be used to better predict the impact of current and projected future environmental changes on extinction risk in the sea.
Download the pdf of the paper by clicking on the image.
Records of seawater chemistry help constrain temporal variations in geochemical processes that impact the global carbon cycle and climate through Earth’s history. Here we reconstruct Cenozoic seawater Sr/Ca using fossil Conus and turritellid gastropods.
Our favored seawater Sr/Ca scenarios point to a significant increase in the proportion of aragonite versus calcite deposition in shelf sediments from the Middle Miocene, coincident with the proliferation of coral reefs. We propose that this occurred at least 10 million years after the seawater Mg/Ca threshold was passed, and was instead aided by declining levels of atmospheric carbon dioxide.
Pdf of the paper available by clicking on these images of cone shells…
Fossils and genes are the two principal ways to study evolution, but they are rarely studied together. This project allowed us to make the first integration of fossil and molecular records of cupuladriid bryozoans Continue reading →
Rising ocean temperatures and ocean acidity may deliver a deadly one-two punch to the world’s corals. Holger Anlauf placed coral larvae and young corals under four controlled culture conditions: (1) increased temperatures (2) increased acidity (3) combination of Continue reading →
As a PhD student I devised and developed a completely new technique for investigating paleoseasonality. Reconstructions of paleoenvironments often fail to understand the importance of the mean annual range of temperature (MART) in both oceanographic and biological contexts. The new technique, called the ‘zooid size approach’ makes use of the temperature-size rule in colonial bryozoans to estimate MART. The temperature-size rule is a universal phenomenon that states that body size decreases as temperature increases.
At the time, our understanding of the temperature-size rule was rudimentary and it was necessary to develop hypotheses on the mechanisms behind the rule and then test them under controlled culture and natural experiments, before finally applying the approach to fossil bryozoans to estimate MART’s in ancient seas.
The original paper published in 2000 presenting the technique can be downloaded here.
Now 10 years later with my ex-Phd supervisor Beth Okamura we review the approach along with the growing body of work that has since been published on the theme. We consider the general issue of why body size varies with temperature, explore the limitations of the approach and highlight its advantages relative to other proxies for palaeotemperature inferences.
Download the pdf of this new paper by clicking on the image.
Even genetically identical animals can look very different if they grow and live in different environments. Think ‘you are what you eat’. I make use of this phenomenon to try to reveal changes in environments in the deep past by first understanding what drives change in morphology in the animals in question and then measuring that morphology in fossils through time.
I applied this paradigm to one of the most studied and certainly most discussed events in the history of life on earth. The K-T (Cretaceous-Tertiary) boundary, 65 million years ago and the demise of the non-avian Dinosaurs and a suite of other animals and plants in the seas and on land. I made detailed measures of morphology in a number of fossil bryozoans in a beautiful K-T section of chalk in Denmark.
Rapid and repeated changes in morphology suggest that there were a suite of environmental changes in the last few thousand years just before the K-T boundary.
Although we dont explore the causes of the extinctions, or the ‘smoking gun’, these results are important for a full understanding of the complex changes associated with major extinctions observed to occur around the world. Click on the image for the pdf.
Evolutionary success was determined by mode of reproduction in cupuladriid bryozoans: Closure of the Panama Isthmus 3 million years ago led to a rapid reduction in primary productivity across the Caribbean. In response, cupuladriid bryozoans underwent a major transition, with evolutionary winners and losers dictated by how much sex they were having. Click on the image to download the pdf.
Hotspots of high species diversity are a prominent feature of modern global biodiversity patterns. Fossil and molecular evidence is starting to reveal the history of these hotspots. There have been at least three marine biodiversity hotspots during the past 50 million years. They have moved across almost half the globe, with their timing and locations coinciding with major tectonic events. The birth and death of successive hotspots highlights the link between environmental change and biodiversity patterns. The antiquity of the taxa in the modern Indo-Australian Archipelago hotspot emphasizes the role of pre-Pleistocene events in shaping modern diversity patterns. Click on the image for the pdf of the paper.
Since the late Mesozoic, several bryozoan groups have occupied unstable soft-sediment habitats by adopting a free-living and motile mode of life. Today, the free-living bryozoans often dominate epibenthic faunal communities in these expansive habitats, yet their biology and ecology remain poorly understood. This study examines their unique mode of life by exploring the relationship between form and function in the free-living Cupuladriidae of tropical America. Click on the image for the pdf of the paper.
Most people think Panama has two seas – the Caribbean and the Pacific. In fact it has three and they are each very distinct. This paper presents detailed hydrological measurements from the two seas along the Pacific coast of Panama: the Gulf of Panama and the Gulf of Chiriqui, and characterizes the environmental differences between them. Click on the image for the pdf of the paper.
We discovered a two million year lag in Caribbean extinction after the environmental and ecological events responsible. This finding challenges the conventional wisdom that evolutionary cause and effect should necessarily coincide. Click on the image for the pdf of the paper.
A full understanding of any climate requires an appreciation of the amount of seasonal variation in temperature. This is important not only for present-day climatology but also for investigation of ancient environments. In this paper I present a novel approach to reveal how seasonal an ancient sea was by measuring the amount of variation in zooid size within colonies of fossil cheilostome bryozoans.