Research Objectives & Our funding for this cruise These are our aims. 1. Quantify cost of filtration for the two main reef sponges: Farrea occa and Heterochone calyx. Here we will measure how much oxygen is used to filter each liter of water. We will also capture water filtered to get a count of the food intake. From our 2015 trip we think there is not enough food to power the sponge pump. We think (hypothesize) that they use 'passive flow'.
2. Determine the effect of resuspended sediment on filtration by Farrea occa. Glass sponges use electrical signals to stop filtration (see our 1997,1999 papers). In lab work sediment can cause sponges to really reduce filtration. Does this happen at the reefs? We will create sediment disturbances to see if Farrea reduces filtration, and we'll look at how much sediment it takes to stop the sponge filtering, and also how long it takes the sponge to recover if it stops filtering water.
3. Quantify water properties (bacteria, nutrients) filtered by sponges. Not only will bacteria counts tell us how much food the sponge gets, but by measuring all the contents of the water filtered by the sponge, we can use the rate of filtration (from  above) and a count of all the sponges on the reefs ( below) to determine what effect reef sponges have on the water around them. From 2015 we calculated that one sponge can filter up to 300,000 liters of water a day.
4. Validate estimates of live sponge cover mapped in 2015. To calculate the effect of reef filtration on the water column we need to have an accurate measure of how much reef there is. We also would like to know whether the current reef boundaries accurately reflect the living reef. We will use ROPOS to fly over the reef capturing video and still images.
5. Quantify biodiversity and abundance of species associated with the reef using imagery and sound; evaluate mechanisms of monitoring above characteristics for MPAs. We will use the images and video to count all the animals we find on the reef and between reef patches (inter-reef). We will also place hydrophones on and off the reef to listen to the sound of a living reef. And we will use short transects over different parts of the reef to find out how the height and complexity of reef mounds corresponds to animal density. We hope to use these different approaches to come up with practical tools for monitoring reefs in the future.
6. Determine food web structure on the reef via stable isotopes and an on-board experiment. The reef is built by sponges, which create habitat for other animals, but perhaps the sponges also rely on those animals for food. We will collect representatives of animals on and around the sponges, in the muds around the sponges, and in the water around the sponges, and use stable isotope analysis and DNA to determine who feeds on who. We hope to understand what interactions are important for a vibrant reef.
And...we're hoping for good weather to do this all in :)
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